Article

Demonstration of Si based InAs/GaSb type-II superlattice p-i-n photodetector

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Abstract

In this paper, mid-wave infrared photodetection based on an InAs/GaSb type-II superlattice p-i-n photodetector grown directly on Si substrate is demonstrated and characterized. Excitation power dependence on integrated intensity from the photoluminescence measurements reveals a power coefficient of P ∼ I0.74, indicating that defects related process is playing an important role in the predominant recombination channel for photogenerated carriers. At 70 K, the device exhibits a dark current density of 2.3 A/cm2 under −0.1 V bias. Arrhenius analysis of dark current shows activation energies much less than half of the active layer bandgap, which suggests that the device is mainly limited by surface leakage and defect-related generation-recombination, consistent with the photoluminescence analysis. The detector shows 50% cutoff wavelength at ∼5.5 µm at 70 K under bias of −0.1 V. The corresponding peak responsivity and specific detectivity are 1.2 A/W and 1.3 × 109 cm∙Hz1/2/W, respectively. Based on these optoelectronics characterization results, reduction of defects by optimizing the III/V-Si interface and material growth quality are argued to be the main factors for performance improvement in this Si-based T2SL detector towards low cost, large-format MWIR detection system on Si photonics platform.

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... Fig. 6 plots the dependences of PL integrated intensity (IPL) on laser excitation intensity (LPL) for both peaks. The data are modelled by the power law relation [26]: ...
... here a is a coefficient and the exponent k is more crucial since it is indicative of the dominant recombination pathways. In high temperature regime where both radiative and non-radiative recombination mechanism exist, three types of recombination can affect the PL intensity: Shockley-Read-Hall (k~2), radiative (k~1) and Auger (k~2/3) [26]; in low temperature region, nonradiative processes can be negligible and two possible recombination routes are generally considered: free-or boundexciton (1£k<2) and free-to-bound or donor-acceptor pair (k<1) [27]. As seen from Fig. 6, for the low to moderate laser intensity (<10 W/cm 2 ) the exponent k~1.03 and k~0.97 for QW and QD PL peak suggest that the two emissions are most probably associated with the radiative recombination of exciton bound at electron and hole ground state. ...
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... The diffusion-and generation-recombination(G-R)-limited behavior, fitted according to the analytical expressions presented by Gopal et al. 62 , are also shown. As Fig. 5c shows, Sample C is dominated by diffusion currents at temperatures above 120 K and G-R currents in the temperature range 100 K-120 K in a manner consistent with previously reported devices 47,63 . At temperatures below 100 K, the measured dark current density deviates from the fitted G-R-dominated behavior, possibly due to the presence of other sources of dark current such as trap assisted tunneling (TAT) or shunt currents. ...
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... The thermal and shot noise limited specific detectivity D * of the HPT is calculated by [21]: ...
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... It involves numerous applications, such as vision at night, detection of temperature, early warning, navigation, flight control systems, weather tracking, protection, and monitoring. They are also ideal for tracking and measuring emissions, relative humidity profiles, and ambient distribution of various gases (such as ozone, carbon monoxide, and nitrous oxide) [7][8][9]. This is because, in this infrared (IR) spectral field [10], most of the absorption lines of gas molecules lie [11][12][13]. ...
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... In the case of integration of Sb-based devices with Si substrates, ~12% lattice mismatch between GaSb and Si and the corresponding 0.67 monolayer critical thickness of GaSb on Si [5] become a crucial issue for the growth of a high crystal quality buffer layer directly on Si substrate. Although Sb-based photodetectors on Si have been successfully demonstrated in recent years [6][7][8], the growth conditions for buffer layers still need to be improved for better device performances. ...
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... Finally, the specific detectivity D* was calculated by [26]: * = ...
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We analyze and compare different aspects of InAs/InAsSb and InAs/GaSb type-II superlattices for infrared detector applications and argue that the former is the most effective when implemented for mid-wavelength infrared detectors. We then report results on an InAs/InAsSb superlattice based mid-wavelength high operating temperature barrier infrared detector. At 150 K, the 50% cutoff wavelength is 5.37 μm, the quantum efficiency at 4.5 μm is ∼52% without anti-reflection coating, the dark current density under −0.2 V bias is 4.5 × 10−5 A/cm², and the dark-current-limited and the f/2 black-body (300 K background in 3–5 μm band) specific detectivities are 4.6 × 10¹¹ and 3.0 × 10¹¹ cm-Hz1/2/W, respectively. A focal plane array made from the same material exhibits a mean noise equivalent differential temperature of 18.7 mK at 160 K operating temperature with an f/2 optics and a 300 K background, demonstrating significantly higher operating temperature than InSb.
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We report on the direct growth and characterization of type-II InAs/GaSb superlattice (T2SL) MWIR photodetector structure grown on a GaAs substrate by molecular beam epitaxy. The designed photodetector structure contains 140 period of 8.0 ML InAs/8.3 ML GaSb p-i-n SL structure with a 50% cutoff wavelength of 3.78 μm. We achieved a peak specific detectivity (D∗) and differential resistance area product at zero bias (R0A) of 1.3 × 10¹² cm Hz½ W⁻¹ and 10⁴ Ω cm² at 80 K, respectively. The obtained D∗ value is the best value reported up to now for a T2SL MWIR p-i-n photodetector grown on a GaAs substrate. The crystalline quality and the uniformity of the grown structure were verified by high resolution X-ray diffraction method by measuring three different spots on grown structure on a full 4 inch SI GaAs substrate.
Article
In this work, the effects of p-type beryllium (Be) doping on the optical properties of GaSb epilayers grown on GaAs substrate by Molecular Beam Epitaxy (MBE) have been studied. Temperature- and excitation power-dependent photoluminescence (PL) measurements were performed on both nominally undoped and intentionally Be-doped GaSb layers. Clear PL emissions are observable even at the temperature of 270 K from both layers, indicating the high material quality. In the Be-doped GaSb layer, the transition energies of main PL features exhibit red-shift up to ∼7 meV, and the peak widths characterized by Full-Width-at-Half-Maximum (FWHM) also decrease. In addition, analysis on the PL integrated intensity in the Be-doped sample reveals a gain of emission signal, as well as a larger carrier thermal activation energy. These distinctive PL behaviors identified in the Be-doped GaSb layer suggest that the residual compressive strain is effectively relaxed in the epilayer, due possibly to the reduction of dislocation density in the GaSb layer with the intentional incorporation of Be dopants. Our results confirm the role of Be as a promising dopant in the improvement of crystalline quality in GaSb, which is a crucial factor for growth and fabrication of high quality strain-free GaSb-based devices on foreign substrates.
Article
In this study, p-i-n InAs/GaSb type II superlattice photodiodes were directly grown on silicon substrates. The superlattice structures were grown monolithically on miscut Si substrates via a 10 nm AlSb nucleation layer. Interfacial misfit array technique was used to accommodate the large lattice mismatch between III-Sb epi-layers and Si. Atomic force microscopy and X-ray diffraction measurements revealed degraded material quality of type II superlattices grown on Si, compared with the sample grown on GaAs. Photoluminescence characterisation indicates comparable optical properties with about 39% deduction of peak intensity. Dark current measurements were also used to study the electrical properties of the samples.
Article
Multiple quantum well (MQW) photodiodes based on the InGaAs/GaAsSb material system are emerging as viable candidates for mid infrared detection. A critical issue for these devices is dark current caused by defects within the material. In this work, low frequency noise spectroscopy and random telegraph signal characterization were used to characterize defect levels in MQW photodiodes. Three traps, located at 0.14 eV (Ea), 0.34 eV (Eb), and 0.43 eV (Ec), were identified from the measured noise. Ea is associated with bulk InGaAs, Eb may be associated with bulk GaAsSb, and Ec is localized at the InGaAs/GaAsSb heterointerface.
Article
We have investigated various passivation techniques for type-II InAs/GaSb strained layer superlattice (SLS) detectors with p-i-n and PbIbN designs with a 100%-cut-off wavelength of ∼12μm at 77K. The passivation schemes include dielectric deposition (silicon nitride (SiNx), silicon dioxide (SiO2), photoresist (SU-8)), chalcogenide treatments (zinc sulfide (ZnS), ammonium sulfide [(NH4)2S]), and electrochemical sulphur deposition. [(NH4)2S] passivation and electrochemical sulphur passivation (ECP) showed the better performances, improving the dark current density by factors of 200 and 25 (p-i-n detector) and ∼3 and 54 (PbIbN detector), respectively (T=77K, −0.1V of applied bias). The specific detectivity D* was improved by a factor of 2 and by an order of magnitude for (NH4)2S and ECP passivated PbIbN detectors, respectively.
Article
The injection and temperature dependence of the spontaneous emission quantum efficiency of molecular beam epitaxy grown GaAs/AlGaAs heterostructures is determined using excitation dependent photoluminescence (PL) measurements. Two samples are compared; one grown with Sb as a surfactant and one grown without Sb. The PL measurements were performed at temperatures from 80 to 320 K using a HeNe pump laser with powers ranging from 0.6 to 35 mW. The quantum efficiency is inferred from the power law predicted by the rate equations that links pump power and integrated PL signal. The use of Sb as surfactant improved the extrapolated peak spontaneous emission quantum efficiency from 0.970 to 0.977 at 300 K and from 0.996 to 0.998 at 180 K. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
• Z Deng
Z. Deng, et al. Infrared Physics and Technology 101 (2019) 133-137