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InP-based type-II quantum-well lasers and LEDs
Abstract
Type-II InP-based light sources provide a promising concept for mid-infrared lasers. These have recently made huge progress, as the first electrically and optically pumped lasers could be demonstrated beyond the wavelength limit for type-I InP-based lasers (~2.3 μm). In this paper, we introduce the material system and device concepts, and report the latest achievements, such as electrically pumped lasing operation up to a wavelength of 2.6 μm in pulsed mode, continuous-wave resonant-cavity light-emitting diode operation up to a wavelength of 3.3 μm at 20-80 °C and photoluminescence even up to 3.9 μm.
... In this way, heterogeneously integrated III-Von-silicon lasers and photodetectors can be realized using the same epitaxial layer stack. In the midinfrared wavelength range, quantum cascade structures and interband cascade structures can be used as the active region for high-performance lasers above 3 μm wavelength [46,47], while InP-based type-I, type-II and GaSb-based type-I heterostructures can provide the gain for diode lasers in the 2-3 μm wavelength range [48][49][50], as shown in Figure 2. Recently, A. Spott et al. reported a quantum cascade laser (QCL) heterogeneously integrated on a silicon-on-nitride-on-insulator waveguide circuit, with emission wavelength between 4.6 and 4.9 μm [51]. For mid-infrared silicon photonic ICs, low-loss passive waveguides, beam splitters and filters (spectrometers) can be fabricated in silicon foundries [17], which is an asset of mid-infrared silicon photonic sensors. ...
... In this way, heterogeneously integrated III-V-on-silicon lasers and photodetectors can be realized using the same epitaxial layer stack. In the mid-infrared wavelength range, quantum cascade structures and interband cascade structures can be used as the active region for high-performance lasers above 3 µm wavelength [46,47], while InP-based type-I, type-II and GaSb-based type-I heterostructures can provide the gain for diode lasers in the 2-3 µm wavelength range [48][49][50], as shown in Figure 2 In this paper, we focus for the laser integration on the 2-2.5 μm wavelength range which is relevant for many gas sensing applications (including for example CO2, CO, HF and NH3). In this wavelength range, GaSb-based type-I diode lasers exhibit high performance. ...
... In recent years, type-II quantum well lasers grown on InP substrate with emission wavelength up to 2.7 μm were demonstrated [55]. Besides, resonant-cavity light emitting diodes operating up to 3.3 μm wavelength and photoluminescence up to 3.9 μm wavelength were reported based on these InP-based type-II InGaAs/GaAsSb quantum wells [49,56]. These results indicate that InP-based type-II heterostructures are promising for the integration of 2-4 μm wavelength range light sources on a silicon photonic integrated circuit. ...
The availability of silicon photonic integrated circuits (ICs) in the 2–4 µm wavelength range enables miniature optical sensors for trace gas and bio-molecule detection. In this paper, we review our recent work on III–V-on-silicon waveguide circuits for spectroscopic sensing in this wavelength range. We first present results on the heterogeneous integration of 2.3 µm wavelength III–V laser sources and photodetectors on silicon photonic ICs for fully integrated optical sensors. Then a compact 2 µm wavelength widely tunable external cavity laser using a silicon photonic IC for the wavelength selective feedback is shown. High-performance silicon arrayed waveguide grating spectrometers are also presented. Further we show an on-chip photothermal transducer using a suspended silicon-on-insulator microring resonator used for mid-infrared photothermal spectroscopy.
... In recent years, electrically pumped lasers using type-II heterostructures on an InP substrate were demonstrated up to a wavelength of 2.7 µm and with a threshold current density of 3.2 kA/cm 2 at 0 °C at a continuous wave (CW) lasing wavelength of 2.31 µm [15,16]. Besides, resonant-cavity light-emitting diodes operating up to 3.3 µm wavelength and photoluminescence up to 3.9 µm wavelength were reported based on this material system [17,18]. All of these results appear promising for the realization of III-V/silicon photonic ICs operating in the 2 μm or 3 μm wavelength range by bonding InP-based type-II heterostructures to a silicon waveguide circuit. ...
... The same epitaxial layer stack has been used to realize heterogeneously integrated InP-based type-II quantum well photodetectors. More specific information about the "W"shaped active region design can be found in [16,18]. The mode intensity profiles and optical coupling efficiency are calculated using commercial software (FIMMWAVE) to optimize the device design. ...
... Reducing the buried oxide thickness or connecting the top heat spreader to the silicon substrate also can be used to reduce the thermal resistance. Besides, the carrier injection efficiency of the InP-based type-II epitaxial structure should be further enhanced to improve the maximum operating temperature [18]. Figure 7 shows the laser output power coupled to the silicon waveguide as a function of the injected pulsed current (pulse duration 0.5 μs, period of 50 μs) at a stage temperature ranging from 15 °C to 40 °C. ...
Heterogeneously integrated InP-based type-II quantum well Fabry-Perot lasers on a silicon waveguide circuit emitting in the 2.3 µm wavelength range are demonstrated. The devices consist of a "W"-shaped InGaAs/GaAsSb multi-quantum-well gain section, III-V/silicon spot size converters and two silicon Bragg grating reflectors to form the laser cavity. In continuous-wave (CW) operation, we obtain a threshold current density of 2.7 kA/cm<sup>2</sup> and output power of 1.3 mW at 5 °C for 2.35 μm lasers. The lasers emit over 3.7 mW of peak power with a threshold current density of 1.6 kA/cm<sup>2</sup> in pulsed regime at room temperature. This demonstration of heterogeneously integrated lasers indicates that the material system and heterogeneous integration method are promising to realize fully integrated III-V/silicon photonics spectroscopic sensors in the 2 µm wavelength range.
... 'W'-type quantum wells with barrier layers incorporated for better carrier confinement and higher oscillator strength than those in original type-II band alignment have been proposed. By using 'W'-type structure, the lasing wavelength was extended recently [13][14][15]. So far, the longest lasing wavelength at room temperature was 2.6 μm. ...
... In our devices, highly-strained and thin GaAs 0.22 Sb 0.78 and In 0.66 Ga 0.34 As layers were used to increase the wavefunction overlap between electrons and holes to enhance the radiative recombination rate. In addition, to avoid the epitaxial problem of compositional control in the GaAsSb alloy [17], we used In 0.52 Al 0.24 Ga 0.24 As as the separate confined layer (SCL) instead of conventional GaAs 0.51 Sb 0.49 [13,15]. In the following, we shall present three lasers lasing at different wavelengths (2.1, 2.2, and 2.35 μm) with very low J th at room temperature. ...
... The lowest threshold current of ~130 mA was obtained for the 1.5-mm-long laser. For the 2-mm-long laser, the measured threshold current (I th ) was 140 mA, corresponding to a much lower J th of about 0.781 kA/cm 2 (compared with the best result J th ~2.4 kA/cm 2 from the lasers with the same cavity length and 2.3 μm lasing wavelength in the previously published work) [15]. Even smaller J th was obtained for lasers with longer cavities. ...
The electrically driven short-wavelength infrared semiconductor laser using InP-based InGaAs/GaAsSb W-type quantum wells (QWs) is investigated. Using Sb-free separate confined layer and engineered QWs, the laser lasing at 2.35 μm exhibits a low-threshold current density at infinite cavity length of 83 A/cm2 per QW under pulsed operation at room temperature. The internal loss αi and internal quantum efficiency ηi of the laser are 17.5 cm-1 and 15%, respectively.
... Low-temperature lasing in pulsed mode; growth on In 0.8 Al 0.2 As metamorphic buffer [31] GaInAs/GaAsSb type-II quantum wells 2.6-3. 9 Electrically pumped lasing in pulsed mode at 2.6 µm; spontaneous emission up to 3.9 µm [32] InGaAs/GaAsSb type-II 'W-design' quantum wells > 2.0 Room temperature PL at ∼2.1 µm; up to ∼2.5 µm from calculations [33] GaInAs/GaAsSb type-II quantum wells 2.4-3.0 Room temperature PL data [34] Type II W-shaped InAsN/GaAsSb/InAsN/GaInP QW ∼3.8 ...
In this study, we propose designs of an interband cascade laser (ICL) active region able to emit in the application-relevant mid infrared (MIR) spectral range and to be grown on an InP substrate. This is a long-sought solution as it promises a combination of ICL advantages with mature and cost-effective epitaxial technology of fabricating materials and devices with high structural and optical quality, when compared to standard approaches of growing ICLs on GaSb or InAs substrates. Therefore, we theoretically investigate a family of type II, “W”-shaped quantum wells made of InGaAs/InAs/GaAsSb with different barriers, for a range of compositions assuring the strain levels acceptable from the growth point of view. The calculated band structure within the 8-band k·p approximation showed that the inclusion of a thin InAs layer into such a type II system brings a useful additional tuning knob to tailor the electronic confined states, optical transitions’ energy and their intensity. Eventually, it allows achieving the emission wavelengths from below 3 to at least 4.6 μm, while still keeping reasonably high gain when compared to the state-of-the-art ICLs. We demonstrate a good tunability of both the emission wavelength and the optical transitions’ oscillator strength, which are competitive with other approaches in the MIR. This is an original solution which has not been demonstrated so far experimentally. Such InP-based interband cascade lasers are of crucial application importance, particularly for the optical gas sensing.
... Type-I active regions on InP can currently only access wavelengths up 2.33 µm with longer wavelength emission limited by strain [202]- [204]. In contrast the 'W' GaInAs/GaAsSb active region can theoretically access wavelengths up to 4 µm and has demonstrated room temperature electroluminescence at 3.9 µm [205]. The 'W' structure consists of a GaAsSb layers for hole confinement, grown between two GaInAs layers for electron confinement. ...
... Sprengel et al. [65] reported the first InP-based type-II laser diode with emission wavelength above 2.3 pm, electrically pumped up to 2.55 pm. The lasing wavelength was then extended to 2.7 pm in 2014 [66]. To achieve this long-wavelength emission, a "W"-shaped InGaAs/GaAsSb quantum well was used. ...
... Stephan Sprengel et al. have demonstrated InP-based InGaAs/GaAsSb type-II QW nanoheterostruc- ture lasers for wavelength range up to 2.7 µm [3]. Electrically and optically pumped InP-based type-II mid-infrared lasers have been demonstrated [4]. Chia- Hao Chang et al. have investigated InP-based InGaAs/GaAsSb W-type quantum wells [5]. ...
Variations in wavefunction confinement under external uniaxial strain are observed to affect the optical gain obtained in type-II quantum well nanodimension heterostructures. This paper reports the wavefunctions and optical gain realized in In0.3Ga0.7As/GaAs0.4Sb0.6 type-II double QW heterostructure under uniaxial strain along [001]. Energy bands, wavefunctions of confinement states in the structure and optical gain of the heterostructure under electromagnetic field perturbation are presented. The 6 × 6 k·p Hamiltonian matrix is considered, and Luttinger–Kohn model has been applied for the electronic band structure calculations. Optical gain spectra of the double QW nanoheterostructure under external uniaxial strain of 1, 2 and 5 GPa, respectively, is calculated. The optical gain curve shows a significant improvement in gain under external uniaxial strain along [001] at 300 K. For a charge carrier injection of 8 × 10¹²/cm², the optical gain is 9170 in x polarization. The heterostructure is seen to be operating in the energy range of 0.65–0.8 eV (1549–1907 nm). Thus, a wide range wavelength tuning can be realized.
... 15,16 The lasing wavelength in this material system can possibly be extended to longer wavelengths as photoluminescence up to 3.9 lm wavelength has been demonstrated. 17 These results indicate that compact III-V/silicon photonics sensor systems can be realized by integrating InP-based type-II active structures with silicon. Recently, we demonstrated heterogeneously integrated InP-based type-II Fabry-Perot lasers on silicon photonics integrated circuits (PICs) based on adhesive bonding technology. ...
We report on 2.3x μm wavelength InP-based type-II distributed feedback (DFB) lasers heterogeneously integrated on a silicon photonics integrated circuit. In the devices, a III–V epitaxial layer stack with a “W”-shaped InGaAs/GaAsSb multi-quantum-well active region is adhesively bonded to the first-order silicon DFB gratings. Single mode laser emission coupled to a single mode silicon waveguide with a side mode suppression ratio of 40 dB is obtained. In continuous-wave regime, the 2.32 μm laser operates close to room temperature (above 15 °C) and emits more than 1 mW output power with a threshold current density of 1.8 kA/cm² at 5 °C. A tunable diode laser absorption measurement of CO is demonstrated using this source.
... 3 Type-I QW laser diodes and interband cascade lasers on GaSb can cover a significant portion of the mid-IR spectral range (k ¼ 1.9-5.5 lm) under continuous wave (CW) operation at RT. 4 However, GaSb is a less-than-ideal substrate for the growth of optoelectronic devices, especially when compared to InP, which has a higher thermal conductivity and the option of semi-insulating substrates, but perhaps most importantly, a more mature commercial processing infrastructure resulting from InP's position as the substrate of choice for 1.55 lm telecommunication laser diodes. 5,6 Type-I laser diodes on InP have achieved RT lasing up to $2.4 lm through the use of highly strained InAs QWs, while InGaAs/GaAsSb type-II laser diodes on InP have achieved near-RT CW lasing at 2.5 lm. 1,7,8 On the longer wavelength side, strain-balanced QCLs on InP have recently shown significant advances, with high output power and RT CW lasing down to k ¼ 3.0 lm. 9 To emit wavelengths below $4.0 lm, extremely high strain is required for maximum conduction band offsets. 2 Despite a number of possible device design options, the realization of efficient RT CW InP-based lasers for k ¼ 2.5-3.0 lm is highly challenging due to the very high strain in the active region materials. ...
The modern commercial optoelectronic infrastructure rests on a foundation of only a few, select semiconductor materials, capable of serving as viable substrates for devices. Any new active device, to have any hope of moving past the laboratory setting, must demonstrate compatibility with these substrate materials. Across much of the electromagnetic spectrum, this simple fact has guided the development of lasers, photodetectors, and other optoelectronic devices. In this work, we propose and demonstrate the concept of a multi-functional metamorphic buffer (MFMB) layer that not only allows for growth of highly lattice-mismatched active regions on InP substrates but also serves as a bottom cladding layer for optical confinement in a laser waveguide. Using the MFMB concept in conjunction with a strain-balanced multiple quantum well active region, we demonstrate laser diodes operating at room temperature in the technologically vital, and currently underserved, 2.5–3.0 μm wavelength range.
... However, room-temperature InP-based type-I laser diodes have only been reported up to ∼2.4 μm [21]. While InP-based type-II quantum wells have generated photoluminescence up to 3.9 μm, electrically pumped lasing has only been seen up to 2.6 μm [22]. GaSb-based type-I laser diodes can operate up to 3.6 μm [23]. ...
The mid-infrared spectral region, 2–20 μm, is of great interest for sensing and detection applications, in part because the vibrational transition energies of numerous molecules fall in that region. Silicon photonics is a promising tech- nology to address many of these applications on a single integrated, low-cost platform. Near-infrared light sources, heterogeneously integrated on silicon, have existed for more than a decade, and there have been numerous incorpo- rations of mid-infrared optical devices on silicon platforms. However, no lasers fully integrated onto silicon have previously been demonstrated for wavelengths longer than 2.0 μm. Here we report, to the best of our knowledge, the first quantum cascade lasers on silicon emitting 4.8 μm light, integrated with silicon-on-nitride-on-insulator (SONOI) waveguides, and operating in pulsed mode at room temperature. The broadband and versatile nature of both quantum cascade lasers and the SONOI platform suggests that this development can be expanded to build photonic integrated circuits throughout the near- and mid-infrared on the same chip.
... 6 However, the InAs QW critical thickness constraint limits further increases in type-I QW emission wavelength on the InP lattice constant. As an alternative, InGaAs/GaAsSb type-II structures have been employed on InP, and recently Sprengel et al. demonstrated type-II laser diodes at 2.6 lm in pulsed mode at RT and at 2.3 lm in the CW mode at 0 C. 7 On the longer wavelength side for InP-based technologies, quantum cascade lasers (QCLs) have recently achieved significant advances with high output power and RT CW lasing at k ¼ 3.0 lm. 8 Even with the merits of high power output under RT CW operation, QCLs fundamentally require high turn-on voltages ($12 V) and large threshold currents, leading to high threshold power densities. Furthermore, to emit wavelengths close to 3 lm, highly strained InGaAs/InAlAs growth is required for large conduction band offsets. ...
We report room-temperature (RT) electroluminescence
(EL) from InAs/InAsxP1−x
quantum well
(QW)
light-emitting diodes
(LEDs) over a wide wavelength range of 2.50–2.94 μm. We demonstrate the ability to accurately design strained InAs
QW emission wavelengths while maintaining low threading dislocation density, coherent QW interfaces, and high EL intensity. Investigation of the optical properties of the LEDs grown on different InAs
xP1−x metamorphic buffers showed higher EL intensity and lower thermal quenching for QWs with higher barriers and stronger carrier confinement. Strong RT EL intensity from LEDs with narrow full-width at half-maximum shows future potential for InAs
QW mid-infrared laser diodes on InAsP/InP.
The development of integrated photonics experiences an unprecedented growth dynamic, owing to accelerated penetration to new applications. This leads to new requirements in terms of functionality, with the most obvious feature being the increased need for wavelength versatility. To this end, we demonstrate for the first time the flip-chip integration of a GaSb semiconductor optical amplifier with a silicon photonic circuit, addressing the transition of photonic integration technology towards mid-IR wavelengths. In particular, an on-chip hybrid DBR laser emitting in the 2 µm region with an output power of 6 mW at room temperature is demonstrated. Wavelength locking was achieved employing a grating realized using 3 µm thick silicon-on-insulator (SOI) technology. The SOI waveguides exhibit strong mode confinement and low losses, as well as excellent mode matching with GaSb optoelectronic chips ensuring low loss coupling. These narrow line-width laser diodes with an on-chip extended cavity can generate a continuous-wave output power of more than 1 mW even when operated at an elevated temperature of 45°C. The demonstration opens an attractive perspective for the on-chip silicon photonics integration of GaSb gain chips, enabling the development of PICs in a broad spectral range extending from 1.8 µm to beyond 3 µm.
Integrating III-V gain material with silicon photonic integrated circuits enables the realization of advanced laser sources and fully integrated photonics systems for optical communication and sensing applications. The availability of III-V/silicon laser sources operating in the 2-2.5 μm short-wave infrared (SWIR) wavelength range is very valuable for spectroscopic sensing since many important industrial gases and blood glucose have absorption bands in this wavelength range. In this paper, first we present our latest results on heterogeneously integrated III-V-on-silicon distributed feedback (DFB) laser arrays. A III-V-on-silicon DFB laser array covering the 2.27-2.39 μm wavelength range with 6 nm wavelength spacing is reported. This DFB laser array is employed as the light source for tunable diode laser absorption spectroscopy of different gases. A four-channel DFB laser array integrated with a beam combiner is used to perform spectroscopic sensing over a 7nm spectral range without mode hopping at room temperature. Finally, we present our recent advances in widely tunable Vernier lasers based on heterogeneous integration and butt-coupling of the gain section. Continuous tuning near the absorption lines by thermally adjusting the laser cavity length enable high-resolution tunable diode laser absorption spectroscopy (TDLAS) measurements together with wide wavelength coverage.
Heterogeneously integrating III-V materials on silicon photonic integrated circuits has emerged as a promising approach to make advanced laser sources for optical communication and sensing applications. Tunable semiconductor lasers operating in the 2–2.5 μm range are of great interest for industrial and medical applications since many gases (e.g., CO2, CO, CH4) and biomolecules (such as blood glucose) have strong absorption features in this wavelength region. The development of integrated tunable laser sources in this wavelength range enables low-cost and miniature spectroscopic sensors. Here we report heterogeneously integrated widely tunable III-V-on-silicon Vernier lasers using two silicon microring resonators as the wavelength tuning components. The laser has a wavelength tuning range of more than 40 nm near 2.35 μm. By combining two lasers with different distributed Bragg reflectors, a tuning range of more than 70 nm is achieved. Over the whole tuning range, the side-mode suppression ratio is higher than 35 dB. As a proof-of-principle, this III-V-on-silicon Vernier laser is used to measure the absorption lines of CO. The measurement results match very well with the high-resolution transmission molecular absorption (HITRAN) database and indicate that this laser is suitable for broadband spectroscopy.
Silicon photonics is a promising integrated-optics platform for optical communication and sensing applications. Integrating 2–3 μm wavelength widely tunable lasers on silicon photonic integrated circuits enables fully integrated spectroscopic sensors with different potential applications such as multi-species trace gas spectroscopy and bio-molecule detection. Here, we demonstrate a continuous-wave (CW) operated III–V-on-silicon distributed feedback (DFB) laser array covered a broad wavelength range from 2.28 to 2.43 μm. CW operation up to 25°C and an on-chip output power of 2.7 mWin a single mode at 5°C is achieved for lasers operating at 2.35 μm wavelength. Four-channel DFB laser arrays with a continuous tuning range of 10 nm and side mode suppression ratio of 40 dB over the whole range are also presented. This work is a major advance toward chip-scale silicon photonics spectroscopic sensing systems.
Nano-photonic structures offer a highly interesting platform to enhance light-matter interaction on a nanometer scale.
Recently, high-index dielectric structures have gained increasing attention as possible low-loss alternatives to plasmonic nano-antennas made from noble metals.
Furthermore, since non-linear effects offer many unique functionalities like the coherent up-conversion of photons, including the generation of harmonics, many efforts are being made to exploit such phenomena in nano-photonics.
In this thesis, an analysis is presented on nonlinear optical effects in individual dielectric structures, specifically in silicon nanowires (SiNWs).
Nanowires develop strong optical resonances in the visible and infrared spectral range.
In this context, strong enhancement of the optical near-field together with a large surface to volume ratio support the appearance of nonlinear effects.
We show that, compared to bulk Si, a two orders of magnitude increase in second harmonic generation (SHG) is feasible and furthermore unravel different polarization and size-dependent contributions at the origin of the SHG.
Numerical simulations are carried out to reaffirm these experimental findings for which a numerical technique is presented to describe nonlinear effects on the basis of the Green Dyadic Method (GDM).
In the last part of the thesis, the GDM is used together with evolutionary optimization (EO) algorithms to tailor and optimize optical properties of photonic nano-structures.
We eventually fabricate samples, based on EO design, and successfully verify the predictions of the optimization algorithm.
It turns out that EO is an extremely versatile tool and has a tremendous potential for many kinds of further applications in nano-optics.
The electronic and optical properties of InP-based InGaAs/GaAsSbBi type-II quantum well (QW) structures are investigated theoretically. The detailed analyses of the InGaAs/GaAsSbBi type-II QW laser structures were based on a 14-band k · p model. The theoretical results indicate that adding Bi into InGaAs/GaAsSb type-II active regions on InP allows wavelength extension, but with minimal impact to transition matrix element. Moreover, the gain characteristics of the active region of laser were studied as a function of the Bi composition. It is shown that these type-II QW structures are suitable for mid-infrared (2-4 μm) operation at room temperature.
In this paper a generic monolithic photonic integration technology platform and tunable laser devices for gas sensing applications at 2 μm will be presented. The basic set of long wavelength optical functions which is fundamental for a generic photonic integration approach is realized using planar, but-joint, active-passive integration on indium phosphide substrate with active components based on strained InGaAs quantum wells. Using this limited set of basic building blocks a novel geometry, widely tunable laser source was designed and fabricated within the first long wavelength multiproject wafer run. The fabricated laser operates around 2027 nm, covers a record tuning range of 31 nm and is successfully employed in absorption measurements of carbon dioxide. These results demonstrate a fully functional long wavelength photonic integrated circuit that operates at these wavelengths. Moreover, the process steps and material system used for the long wavelength technology are almost identical to the ones which are used in the technology process at 1.5μm which makes it straightforward and hassle-free to transfer to the photonic foundries with existing fabrication lines. The changes from the 1550 nm technology and the trade-offs made in the building block design and layer stack will be discussed. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
We present a widely tunable extended cavity ring laser operating at 2 μm that is monolithically integrated on an indium phosphide substrate. The photonic integrated circuit is designed and fabricated within a multiproject wafer run using a generic integration technology platform. The laser features an intracavity tuning mechanism based on nested asymmetric Mach–Zehnder interferometers with voltage controlled electro-refractive modulators. The laser operates in a single-mode regime and is tunable over the recorded wavelength range of 31 nm, spanning from 2011 to 2042 nm. Its capability for high-resolution scanning is demonstrated in a single-line spectroscopy experiment using a carbon dioxide reference cell.
Annealing effects on the properties of InGaAsN/GaAsSb type-II quantum well (QW) diodes grown on InP substrates by molecular beam epitaxy (MBE) were studied. It was found that the peak of electroluminescence (EL) shows drastic red-shift and the reverse-biased current of the current–voltage (I–V) characteristic of the type-II QW diode increases by the annealing. In addition, we found that the electron effective mass of the InGaAsN layer of the type-II InGaAsN/GaAsSb multiple quantum wells (MQWs) estimated by the temperature dependence of the amplitude of the Shubnikov-de Haas (SdH) oscillations decreases by the annealing. The mechanism of the observed annealing effects was discussed.
The growth of high quality (GaIn)As/Ga(AsSb)/(GaIn)As “W”-quantum well heterostructures is discussed with respect to their application in 1300 nm laser devices. The structures are grown using metal organic vapor phase epitaxy and characterized using high-resolution X-ray diffraction, scanning transmission electron microscopy and photoluminescence measurements. The agreement between experimental high-resolution X-ray diffraction patterns and full dynamical simulations is verified for these structurally challenging heterostructures. Scanning transmission electron microscopy is used to demonstrate that the structure consists of well-defined quantum wells and forms the basis for future improvements of the optoelectronic quality of this materials system. By altering the group-V gas phase ratio, it is possible to cover a large spectral range between 1200 nm and 1470 nm using a growth temperature of 550 °C and a V/III ratio of 7.5. A comparison of a sample with a photoluminescence emission wavelength at 1360 nm with single quantum well material reference samples proves the type-II character of the emission. A further optimization of these structures for application in 1300 nm lasers by applying different V/III ratios yields a stable behavior of the photoluminescence intensity using a growth temperature of 550 °C.
This topical review presents an overview on novel concepts for light emitting diodes (LEDs) and lasers for the near infrared to the THz regime. GaSb-based quantum well lasers are shown to be a promising concept for laser from the near to mid infrared. The GaSb-based edge-emitting lasers offer low thresholds for wavelengths ranging from about 2 to 3.7 μm. However, the development of vertical-cavity surface-emitting lasers and other advanced laser concepts is lagging behind due to material issues and complicated process technology. InP-based type-II quantum wells are an innovative concept for sources emitting in the wavelength range from 2 to 4 μm. This concept combines extended long wavelength emission with the reliable process technology of the already well-established InP-based lasers. Based on this, we present LEDs up to 3.5 μm wavelength, surface emitting lasers at 2.5 μm wavelength and edge emitting lasers up to 2.7 μm. For longer wavelengths, the so-called GaSb- and InAs-based interband cascade lasers can be used operating up to about 7 μm. The mid infrared range between 3 and 20 μm is also covered by quantum cascade lasers (QCL), which are dominating especially in the longer wavelength range above 7 μm. The far infrared reaching to the THz regime is exclusively covered by QCL. While for decades the only available semiconductor laser source for the far infrared and THz range was the direct THz QCL, recent progress demonstrated THz emission in nonlinear mid infrared QCLs. These devices are emitting THz by a nonlinear frequency conversion process, which allows operation at room temperature and beyond. Tunable THz lasers were demonstrated using both monolithic tuning mechanisms and an external cavity approach.
The short-wave infrared wavelength range (2-3 μm) is attractive for applications in gas sensing and next-generation communication systems. Photodetectors and wavelength (de)multiplexers are key components that have to be developed for these systems. In this contribution, we report the integration of InGaAs/GaAsSb type-II quantum well photodetectors and spectrometers on the silicon photonics platform. In this photodetector epitaxial layer stack, the absorbing active region consists of 6 periods of W-shaped quantum wells, which can also be used to realize lasers. The efficient coupling between silicon waveguides and quantum well photodetectors is realized by tapered III-V waveguides. The photodetectors have a very low dark current of 12 nA at -0.5 V bias at room temperature. The devices show a responsivity of 1.2 A/W at 2.32 μm wavelength, and higher than 0.5A/W over the 2.2-2.4 μm wavelength range. On the silicon-on-insulator platform we also demonstrate high performance short-wave infrared spectrometers. 8-channel spectrometers in the 2.3-2.4 μm range with a resolution of 5nm and 1.4nm are demonstrated, showing a cross-talk below -25 dB and an insertion loss lower than 3 dB.
Type-II light sources on InP substrate are an innovative concept for wavelengths ranging from 2 Î1/4m to the mid-IR. The concept is using the type-II band alignment between GaInAs and GaAsSb to exceed the limitation of type-I devices. Since the first demonstration of InP type-II heterostructure lasers above 2.3 Î1/4m in 2012, we have extended the emission wavelength to 2.7 Î1/4m. Furthermore, a drastic reduction in threshold current density down to 104 A/cm2 per QW at infinite length was achieved (at 2.5 Î1/4m), which represents an improvement by more than a factor of two. Additionally CW operation up to 30°C and up to 80°C pulsed is presented. Furthermore, LEDs for 3.5Î1/4m peak emission wavelength and up to 86 Î1/4W output power are shown.
The heterogeneous integration of InP-based type-II quantum well photodiodes on silicon photonic integrated circuits for the 2 µm wavelength range is presented. A responsivity of 1.2 A/W at a wavelength of 2.32 µm and 0.6 A/W at 2.4 µm wavelength is demonstrated. The photodiodes have a dark current of 12 nA at -0.5 V at room temperature. The absorbing active region of the integrated photodiodes consists of six periods of a "W"-shaped quantum well, also allowing for laser integration on the same platform.
We present different concepts for long wavelength buried tunnel junction VCSELs for the spectroscopically important range above 2 μm. This includes GaSb-based laser using GaInAsSb quantum wells, InP-based lasers with V-shaped quantum wells and InP-based lasers using type-II quantum wells. For InP-based devices, emission wavelengths up to 2.36 μm are presented, with single-mode output powers of roughly 500 μW and side-mode suppression ratios of more than 30 dB. GaSb-based VCSELs are presented with single-mode emission at 2.6 μm, a side-mode suppression ratio of more than 20 dB and a peak output power of 400 μW.
InP-based type-II quantum wells are a promising concept for long wavelength lasers beyond 2 μm. In this paper, recently developed vertical-cavity surface-emitting lasers for 2.5 μm with type-II quantum wells are introduced and their performance is discussed. These lasers demonstrate single-mode CW operation with an output power up to 400 μW and side-mode suppression ratio of 30 dB. The maximum temperature for CW operation is 10°C. In order to further analyze their performance, a phenomenological model for the temperature dependences of threshold current densities is presented. Based on this model influence of heat sink temperature, current broadening and self-heating is quantified and conclusions are drawn for an improved design.
A concept for electrically pumped vertical cavity surface emitting lasers
(VCSEL) for emission wavelength beyond 2 μm is presented. This concept integrates type-II quantum wells into InP-based VCSELs with a buried tunnel junction as current aperture. The W-shaped quantum wells are based on the type-II band alignment between GaInAs and GaAsSb. The structure includes an epitaxial GaInAs/InP and an amorphous AlF3/ZnS distributed Bragg reflector as bottom and top (outcoupling) mirror, respectively. Continuous-wave operation up to 10 °C at a wavelength of 2.49 μm and a peak output power of 400 μW at −18 °C has been achieved. Single-mode emission with a side-mode suppression ratio of 30 dB for mesa diameters up to 14 μm is presented. The long emission wavelength and current tunability over a wavelength range of more than 5 nm combined with its single-mode operation makes this device ideally suited for spectroscopy applications.
The mid-infrared electrically-driven laser using InGaAs/GaAsSb ‘W’-type QWs is demonstrated at room temperature. The InP-based laser lasing at 2.35 μm with the lowest threshold current density of 1.42 kA/cm2 is presented.
We show that the morphology of the initial monolayers of InP on Al0.48In0.52As grown by metalorganic vapor-phase epitaxy does not follow the expected layer-by-layer growth mode of lattice-matched systems, but instead develops a number of low-dimensional structures, e.g., quantum dots and wires. We discuss how the macroscopically strain-free heteroepitaxy might be strongly affected by local phase separation/alloying-induced strain and that the preferred aggregation of adatom species on the substrate surface and reduced wettability of InP on AlInAs surfaces might be the cause of the unusual (step) organization and morphology.
We have demonstrated experimentally the InP-based "M"-type GaAsSb/InGaAs quantum-well (QW) laser lasing at 2.41 μm at room temperature by optical pumping. The threshold power density per QW and extracted internal loss were about 234 W/cm2 and 20.5 cm-1, respectively. The temperature-dependent photoluminescence (PL) and lasing spectra revealed interesting characteristics for this type of lasers. Two distinct regions in the temperature dependent threshold behavior were observed and the transition temperature was found to coincide with the cross over point of the PL and lasing emission peaks. The current-voltage characteristic of "M"-type QW laser was superior to the inverse "W"-type one due to its thinner barrier for holes. Further improvement of the "M"-type QW structure could lead to a cost-effective mid-infrared light source.
In this work, we report on the above-room-temperature continuous-wave operation of InP-based antimony-free triangular quantum well (QW)
lasers emitting up to approximately 2.4 μm. X-ray diffraction measurement confirms the favorable structural quality of the highly strained triangular
QWs composed of InAs/In0.53Ga0.47As digital alloy. The maximum continuous-wave working temperature reaches 340 K, and the output power at
300K is about 11mW/facet at an injection current of 350 mA. The internal quantum efficiency of 58% is deduced at 300 K, and the extrapolated
threshold current density for infinite cavity length is 210A/cm2 per quantum well.
We present 3 mu m photoluminescence at room temperature, which is achieved with GaInAs/GaAsSb type-II quantum wells on InP substrate. This long-wavelength emission became feasible by using highly compressive strained Ga(0.25)In(0.75)As and GaAs(0.4)Sb(0.6) layers. Furthermore, a comparison between standard superlattice and so called "W" shaped quantum wells revealed that the emission linewidth can be drastically reduced by using the latter design, which is necessary for low threshold laser operation (C) 2011 American Institute of Physics. [doi:10.1063/1.3665256].
Room-temperature lasing at 2.55 μm is reported for InP-based GaInAs/GaAsSb type-II quantum well lasers in pulsed mode up to 42 °C. This record long-wavelength lasing has become feasible by implementing compressive strain in both materials and a carrier confinement design using an AlAsSb/AlGaInAs electron/hole blocking layer. The device concept appears promising for extending the wavelength range further towards 3 μm.
GaInAsSb–GaSb strained quantum-well (QW) ridge waveguide diode lasers emitting in the wavelength range from 2.51 to 2.72 m have been grown by molecular beam epitaxy. The de-vices show ultralow threshold current densities of 44 A cm 2 () for a single QW device at 2.51 m, which is the lowest re-ported value in continuous-wave operation near room tempera-ture (15 C) at this wavelength. The devices have an internal loss of 3 cm 1 and a characteristic temperature of 42 K. By using broader QWs, wavelengths up to 2.72 m could be achieved. Index Terms—Optical spectroscopy, quantum-well (QW) lasers.
The interband cascade laser (ICL) concept provides robust and efficient emission in the midwave infrared spectral band. While the geometry is somewhat analogous to that of a quantum cascade laser employing intersubband transitions, the ICL implementation exploits the type-II band alignment of the GaSb-based material system. A semimetallic band overlap at the boundary between the electron and hole injector regions automatically generates carriers with densities tunable by quantum confinement. Electrical injection then replenishes the carriers already present rather than creating the population inversion. In this paper, we describe and analyze the physical principles governing ICL operation, and discuss specific modifications to the active region, electron injector, hole injector, and waveguide designs that demonstrably improve the performance. The pulsed I- V and L-I characteristics of devices processed from over 50 wafers provide a statistically meaningful confirmation of the established trends.
We present a rationalized biquadratic interpolation algorithm for calculating quaternary semiconductor parameters and apply it to determine the band gaps of AlGaInAs, AlGaInP, AlInAsSb, GaInPAs, and GaInAsSb over complete compositional ranges. Extension to include bicubic corrections and quinary alloys are discussed. The band gaps of lattice-matched AlGaInAsSb and AlGaInPAs are reported. © 2003 American Institute of Physics.
We present a comprehensive, up-to-date compilation of band parameters for the technologically important III{endash}V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other. {copyright} 2001 American Institute of Physics.
The vast majority of gaseous chemical substances exhibit fundamental vibrational absorption bands in the mid-infrared spectral
region (≈ 2–25 µm), and the absorption of light by these fundamental bands provides a nearly universal means for their detection.
A main feature of optical techniques is the non-intrusive in situ detection capability for trace gases. The focus time period of this chapter is the years 1996–2002 and we will discuss primarily
CW mid-infrared laser spectroscopy. We shall not attempt to review the large number of diverse mid-infrared spectroscopic
laser applications published to date. The scope of this chapter is rather to discuss recent developments of mid-infrared laser
sources, with emphasis on established and new spectroscopic techniques and their applications for sensitive, selective, and
quantitative trace gas detection. For example, laboratory based spectroscopic studies and chemical kinetics, which will also
benefit from new laser source and technique developments, will not be considered.
We report on the fabrication and characterization of light-emitting diodes (LEDs) and laser diodes with a staggered type II Ga <sub>1-x</sub> In <sub>x</sub> As/GaAs <sub>1-y</sub> Sb <sub>y</sub> superlattice (SL) as the active region. SLs were grown strain compensated on the InP substrate using metalorganic chemical vapor deposition. The LEDs show room-temperature electroluminescence up to 2.14 μm, the index-guided diode lasers displayed cw laser emission at 1.71 μm up to 300 K. The spontaneous emission spectrum was found to show a significant blueshift with increasing injection current density, resulting in shorter laser emission wavelengths for the diode laser than for the LED. © 1999 American Institute of Physics.
Extension of the room-temperature operation wavelength of GaSb-based type-I laser diodes up to 3.6 μm is presented. Episide-up mounted ridge waveguide lasers with five compressively strained quantum-wells exhibit lasing in pulsed operation with a threshold current densitiy of 862 A/cm<sup>2</sup> at infinite resonator length at 15°C and 20°mW of average output power per facet.
One-dimensional microcavities are optical resonators with coplanar reflectors separated by a distance on the order of the optical wavelength. Such structures quantize the energy of photons propagating along the optical axis of the cavity and thereby strongly modify the spontaneous emission properties of a photon-emitting medium inside a microcavity. This report concerns semiconductor light-emitting diodes with the photon-emitting active region of the light-emitting diodes placed inside a microcavity. These devices are shown to have strongly modified emission properties including experimental emission efficiencies that are higher by more than a factor of 5 and theoretical emission efficiencies that are higher by more than a factor of 10 than the emission efficiencies in conventional light-emitting diodes.
A mid-IR type-II “W” quantum well diode laser
(λ=3.30 μm) with a broadened waveguide operated in pulsed mode
at 300 K is presented. The spectral width at that temperature was 12 nm,
and the peak output power was 2 mW/facet. The characteristic temperature
T<sub>0</sub> for the range 100-280 K was 48 K
IntroductionTunable, Widely Tunable, and Externally Modulated LasersAdvanced PICsPICs for Coherent Optical CommunicationsReferencesReading ListProblems
We present InP-based resonant-cavity light emitting diodes (LEDs), which are emitting at 2.8 μm, 3.3 μm, and 3.5 μm and were grown by metalorganic vapor phase epitaxy. This long wavelength electroluminescence is achieved by using highly strained GaInAs/GaAsSb type-II quantum wells. The performance of two different active region designs, superlattice (“SL”) and “W”-shaped quantum wells (“W”), is compared. Although continuous wave operation up to 80 °C could be proven, a spontaneous emission droop similar to nitride-based LEDs has been observed and is discussed.
In this paper we present the epitaxial growth and characterization of an InP-based micro-cavity light emitting diode (LED) with up to 3 mu m light emission by using GaInAs/GaAsSb-based type-II quantum wells. The LED was grown by LP-MOVPE and achieves emission from 2 mu m to 3 mu m at room-temperature. Furthermore a second LED with centered emission at 2.8 mu m has been realized. Hence, the achievable long-wavelength electroluminescence emission with InP-based materials has been extended up to 3 mu m.
The optically pumped laser using InGaAs/GaAsSb W-type quantum wells is demonstrated with a threshold power density ${\sim}{\rm 40}~{\rm kW}/{\rm cm}^{2}$. The L–L curve and the dramatic line width shrinkage above threshold confirm, for the first time, mid-infrared lasing in this structure on InP substrates. The lasing wavelength at 2.56 $\mu{\rm m}$ is the longest lasing wavelength at room temperature for the interband transition of InP-based material system.
In this paper, we consider the role of carrier con- finement in achieving high-power continuous wave (CW) room temperature operation of GaSb-based type-I quantum-well (QW) diode lasers at wavelengths above 3 μm. The use of compressive strain and quinternary barrier materials to confine holes in the active QWs allows the fabrication of 3-μm GaSb-based type-I QW diode lasers operating at 17 ◦ C in the CW mode with output power of 360 mW. We will present the results of characterization of 2.2-μm diode lasers grown on metamorphic virtual substrates. The use of InGaSb virtual substrate makes it possible to fabricate de- vices with As free QWs. The prospects of using virtual substrates for development of GaSb-based type-I lasers will be discussed.
An emission wavelength of 2.33 mum in an InAs/InGaAs multiple-quantum-well laser grown by metal-organic vapour phase epitaxy is reported. The laser had an output power above 10 mW under continuous-wave operation at temperatures between 15 and 45degC. High-temperature operation up to 50degC and a characteristic temperature of 51 K were also confirmed.
The alteration of spontaneous emission characteristics in terms of the spontaneous lifetime and spectral emission characteristics are discussed for dipoles in the presence of nearby planar reflecting interfaces and cavities, specifically for the case of semiconductors. For dipoles closely spaced to absorbing metal mirrors, significant lifetime change is possible. Analysis and experimental data are presented for light emitting diodes. For dielectric Fabry-Perot microcavities, the expected lifetime change is small, but significant modification in the radiation pattern of the emitted light occurs. It is shown that the spectral characteristics of emission have a sensitive dependence on the dipole location in the cavity. Comparison is made between a classical against a quantum treatment of the spontaneous emission modification due to the cavity.
The properties of Al<sub>x</sub>In<sub>1-x</sub>Sb light-emitting diodes (LEDs) and photodetectors have been investigated to establish their suitability for methane sensing. Using these components it is possible to achieve good signal-to-noise values at both the characteristic absorption wavelength and also at 4 ¿m, an attractive wavelength for use as a reference channel. A limit of sensitivity of approximately 400 ppm, with an integration time of 10 s and a path length of 5 cm, was estimated for methane detection.
Ingredients. A Phenomenological Approach to Diode Lasers. Mirrors and Resonators for Diode Lasers. Gain and Current Relations. Dynamic Effects. Perturbation and Coupled--Mode Theory. Dielectric Waveguides. Photonic Integrated Circuits. Appendices (16). Index.
Nitride-based light-emitting diodes (LEDs) suffer from a reduction (droop) of the internal quantum efficiency with increasing injection current. This droop phenomenon is currently the subject of intense research worldwide, as it delays general lighting applications of GaN-based LEDs. Several explanations of the efficiency droop have been proposed in recent years, but none is widely accepted. This feature article provides a snapshot of the present state of droop research, reviews currently discussed droop mechanisms, contextualizes them, and proposes a simple yet unified model for the LED efficiency droop.
Illustration of LED efficiency droop (details in Fig. 13).
Vertical-cavity surface-emitting lasers are attractive light sources particularly for gas-sensing applications. Using the AlGaInAs/InP material system, an emission wavelength ranges from 1.3 to 2.05 μm has already been achieved [G. Boehm, M. Ortsiefer R. Shau, J. Rosskopf, C. Lauer, M. Maute, F. Köhler, F. Mederer, R. Meyer, M.-C. Amann, in: Proceedings of MBE XII, J. Crystal Growth (2002) pp. 748–753]. Within this range, absorption lines of gases like H2S (1590 nm), CH4 (1654 nm), H2O (1877 nm) and CO2 (2004 nm) are detectable [G. Totschnig, M. Lackner, R. Shau, M. Ortsiefer, J. Rosskopf, M.-C. Amann, F. Winter, Meas. Sci. Technol. 14 (2003) 472]. The aim of this work is a further expansion of the emission wavelength up to 2.3 μm, exploiting the well-known InP-based material system and the fabrication technique of buried tunnel junction (BTJ) VCSELs [R. Shau, M. Ortsiefer, J. Rosskopf, G. Boehm, C. Lauer, M. Maute, M.-C. Amann, in: Proceedings of SPIE, 5364 (2004) 1–15] to reach the technologically important absorption lines of carbon monoxide (CO) around 2.33 μm.
The effective-mass equations using the Luttinger-Kohn Hamiltonian taking into account the strain effects are solved exactly by making a unitary transformation. Using this method, we need to solve two 2×2 matrices instead of the original 4×4 matrix. The eigenvalues and eigenvectors for the heavy hole and the light hole can be expressed analytically. When applied to heterojunctions such as quantum wells, the reduction in the number of unknowns makes the method a more efficient approach to the calculations of valence-band structures, which takes into account the valence-band mixing and the strain effects with proper boundary conditions. Detailed numerical results and significant features for strained GaxIn1-xAs grown on an In1-xGaxAsyP1-y lattice matched to InP are presented. For a Ga mole fraction x less than 0.468 (compression), the top subband is heavy-hole-like. For x greater than 0.468 (tension strain), the top band can be either a heavy-hole or a light-hole subband, depending on the well width and the shear deformation potential. Interesting subband structures, which show a negative effective mass in the top subband, are discussed.