[show abstract][hide abstract] ABSTRACT: Minority carrier lifetime in long-wave infrared (LWIR) type II InAs/GaSb superlattices was studied using the optical modulation response (OMR) technique in wide ranges of excitation and temperature. The measured carrier lifetime was found to increase superexponentially with decreasing excitation power density below the level of 1 mW/cm2 to 2 mW/cm2. The phenomenon was qualitatively explained by the presence of shallow trapping centers.
Journal of Electronic Materials 08/2013; 41(11). · 1.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: Carrier recombination processes, including the Auger recombination, are studied in InGaAsSb/AlGaAsSb quantum well nanostructures. Based on the dynamics of photoluminescence, we estimate the emission time of an optical phonon, determined the recombination rate as a function of optical-excitation intensity, and estimated the coefficient characterizing the rate of the resonance Auger recombination.
Bulletin of the Russian Academy of Sciences Physics 08/2013; 76(2).
[show abstract][hide abstract] ABSTRACT: The time dependences of the photoluminescence intensity is studied for InGaAsSb/AlGaAsSb quantum wells with different barrier widths and different barrier-material compositions. From analysis of the photoluminescence dynamics, the times of charge-carrier trapping at quantum wells, the energy dissipation times, and the lifetimes, including the lifetime with respect to resonant Auger recombination, are determined. It is shown that, for a certain structure configuration, it is possible to observe the resonant Auger recombination of nonequilibrium charge carriers.
[show abstract][hide abstract] ABSTRACT: We have demonstrated a wet etching technique for fabrication of narrow ridge lasers. Precise control over etching depth and ridge width was realized by introducing an etch stop layer into a laser structure and by using two etchants with different selectivity. The 6-μm-wide ridge laser emitting at 2 μm generated continuous-wave power of 70 mW at 20°C. Single lateral mode operation was observed up to 400 mA, corresponding to 8 × I
Journal of Electronic Materials 08/2013; 41(5). · 1.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: The energy gaps were studied in two types of structures: unrelaxed bulk InAs1−x
layers with x = 0.2 to 0.46 grown on metamorphic buffers and type II InAs1−x
/InAs strained-layer superlattices (SLS) with x = 0.225 to 0.296 in the temperature range from T = 13 K to 300 K. All structures were grown on GaSb substrates. The longest wavelength of photoluminescence (PL) at low temperatures was observed from bulk InAs0.56Sb0.44 with a peak at 10.3 μm and full-width at half-maximum (FWHM) of 11 meV. The PL data for the bulk InAs1−x
materials of various compositions imply an energy gap bowing parameter of 0.87 eV. A low-temperature PL peak at 9.1 μm with FWHM of 13 meV was observed for InAs0.704Sb0.296/InAs SLS. The PL spectrum of InAs0.775Sb0.225/InAs SLS under pulsed excitation revealed a second peak associated with recombination of electrons in the three-dimensional (3D) continuum with holes in the InAs0.775Sb0.225. This experiment determined the conduction-band offset in the InAs0.775Sb0.225/InAs SLS. The energies of the conduction and valence bands in unstrained InAs1−x
and their bowing with respect to the Sb composition are discussed.
Journal of Electronic Materials 08/2013; 42(5). · 1.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: InAs0.6Sb0.4/Al0.75In0.25Sb-based barrier photodetectors were grown metamorphically on compositionally graded Ga1−xInxSb buffer layers and GaSb substrates by molecular beam epitaxy. At the wavelength of 8 μm and T = 150 K, devices with 1-μm thick absorbers demonstrated an external quantum efficiency of 18% under a bias voltage of 0.45 V.
[show abstract][hide abstract] ABSTRACT: Continuous tuning of a room-temperature-operated distributed feedback quantum cascade laser in the range of 0.6 cm−1 (20 GHz) was achieved using 1.3 μm telecom diode laser as a pumping source. We demonstrate wavelength modulation of the quantum cascade laser at frequencies up to 300 MHz.
[show abstract][hide abstract] ABSTRACT: Metamorphic heterostructures containing bulk InAs1−xSbx layers and AlInAsSb barriers were grown on GaSb substrates. The lattice mismatch (up to 2.1%) between the GaSb substrates and the InAsSb layers was accommodated by the growth of GaInSb linearly graded buffers. The 1 μm thick InAsSb0.44 layer with an absorption edge above 9 μm exhibited an in-plane residual strain of about 0.08%. InAs1−xSbx structures with x = 0.2 and x = 0.44 operated as light emitting diodes at 80 K demonstrated output powers of 90 μW and 8 μW at 5 μm and 8 μm, respectively.
[show abstract][hide abstract] ABSTRACT: We demonstrate rapid tuning of the emission frequency of a room-temperature mid-infrared quantum cascade laser by external optical pumping. Emission frequency tuning over 0.3 cm−1 (10 GHz) has been achieved for a λ = 9 μm device by optical generation of electron-hole pairs along the entire length of the laser stripe. Measurements indicate that this approach allows for rapid broadband frequency-modulation of mid-infrared quantum cascade lasers at above 300 MHz modulation frequencies.
[show abstract][hide abstract] ABSTRACT: The band gap energy of the alloy InAsSb has been studied as a function of composition with special emphasis on minimization of strain-induced artifacts. The films were grown by molecular beam epitaxy on GaSb substrates with compositionally graded buffer layers that were designed to produce strain-free films. The compositions were precisely determined by high-resolution x-ray diffraction. Evidence for weak, long-range, group-V ordering was detected in materials exhibiting residual strain and relaxation. In contrast, unstrained films having the nondistorted cubic form showed no evidence of group-V ordering. The photoluminescence (PL) peak positions therefore corresponds to the inherent band gap of unstrained, unrelaxed, InAsSb. PL peaks were recorded for compositions up to 46% Sb, reaching a peak wavelength of 10.3 μm, observed under low excitation at T=13 K. The alloy band gap energies determined from PL maxima are described with a bowing parameter of 0.87 eV, which is significantly larger than measured for InAsSb in earlier work. The sufficiently large bowing parameter and the ability to grow the alloys without ordering allows direct band gap InAsSb to be a candidate material for low-temperature long-wavelength infrared detector applications.
[show abstract][hide abstract] ABSTRACT: Carrier heating in GaAs/AlGaAs quantum wells (QWs) under optical interband pumping in the spontaneous-emission mode has been
studied. The electron temperature was determined as a function of the pumping intensity. The effect of the electric field
on the photoluminescence spectrum was examined. The change in the carrier concentration with the drive current in the spontaneous-
and stimulated-emission modes in InGaAsSb/InAlGaAsSb QWs was determined from electroluminescence spectra. The rise in the
temperature of hot carriers, which results in the increase in the carrier concentration with the drive current, was roughly
[show abstract][hide abstract] ABSTRACT: An interband cascade laser design has been grown by molecular beam
epitaxy using uncracked arsenic and antimony sources. Lasers were
fabricated into both broad-area and narrow-ridge devices, with cavity
lengths ranging between 1 mm and 4 mm. At 300K, under low-duty-cycle
pulsed conditions, threshold current densities for lasers with 2-mm
cavity lengths are as low as 395 A/cm2, with optical emission
centered at a wavelength of ~3.82 μm at 300 K. Continuous-wave (cw)
performance of the narrow-ridge devices has been achieved for
temperatures up to almost 60°C. We present results of both pulsed
(broad-area and ridge) and cw (ridge only) measurements on these lasers,
including L-I-V, spectral, cavity-length, and Hakki-Paoli analyses.
[show abstract][hide abstract] ABSTRACT: Diffraction limited λ = 2–2.2 µm ridge waveguide lasers with continuous wave output power near 100 mW at room temperature were fabricated with a two-step wet etching technique using the interface between the top cladding and waveguide core materials as an etch stopper. The devices did not suffer from lateral current spreading. The second optical mode was suppressed by the low lateral confinement. Experiments showed that reducing the ridge width below 6 µm did not affect the device efficiency or the output beam quality but led to an increase of the transparency current density. We speculate that this increase was associated with the mismatch between the wide modal size and the narrow current path in ridge lasers with suppressed lateral current spreading.
Semiconductor Science and Technology 01/2012; 27(8). · 1.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: Diode lasers operating at 3 µm in continuous wave mode at room temperature were fabricated using metamorphic molecular beam epitaxy. The laser heterostructures have a lattice constant 1.3–1.6% bigger than that of the GaSb substrates. The mismatch between the epi-structure and the substrate lattice constants was accommodated by a network of misfit dislocations confined within linearly compositionally graded buffer layers. Two types of the buffers were tested—GaInSb and AlGaInSb. The laser heterostructures with Al-containing buffer layers demonstrated better surface morphology and produced devices with lower threshold and higher efficiency. At the same time the use of Al-containing buffers caused an excessive voltage drop across the laser heterostructure. Thus, a maximum continuous wave output power of 200 mW was obtained from lasers grown on GaInSb buffers, while only 170 mW was obtained from those grown on AlGaInSb buffers.
Semiconductor Science and Technology 01/2012; 27(5). · 1.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: Infrared (IR) detector materials based on III-V semiconductors are an
affordable alternative to HgCdTe, which is the current material of
choice for most high performance IR focal plane array systems fielded in
the Army. Based on the assumption that III-V compounds do not have an
inherently small bandgap enabling operation out to 10 μm, the long
wave infrared (LWIR) range, there has been substantial research
investment in superlattice (SL) approaches. For this reason, quantum
structures such as quantum well IR photodetectors (QWIPs) and type-II
strained-layer superlattices (SLS) are grown to take advantage of
confinement effects and to induce an effective bandgap in the desired
range. The drawbacks of these approaches include inherently low quantum
efficiencies and operating temperature for QWIPs, and very short
minority carrier lifetimes for SLS detectors. In this presentation, we
will discuss approaches for developing III-V, direct bandgap, dilute N
and Bi alloys grown by molecular beam epitaxy (MBE) for LWIR
[show abstract][hide abstract] ABSTRACT: In plane and growth direction electron effective mass in short period InAs/GaSb semiconductor superlattices (SL) was measured using cyclotron resonance at different orientations of magnetic field with respect to SL growth direction. It was demonstrated that the electron spectrum near the bottom of the SL subband has 3D character, with the in-plane effective masses ranging from 0.023 m0 to 0.028 m0 and growth direction effective masses of 0.03–0.034 m0 depending on the SL period and growth conditions. The measured effective masses are close to those calculated in the weak coupling limit of the Kronig-Penney model. In this limit the SL electron effective mass is a weighted average of the electron effective masses of corresponding bulk materials. Correlation between the magnitude of cyclotron mobility, amplitude of negative magnetoresistance, and steepness of the long wavelength side of the photoluminescence spectrum indicate that the crystalline structure disorder is a major factor contributing to the momentum relaxation time of the electrons.
Journal of Applied Physics 08/2011; 110:043720. · 2.21 Impact Factor
[show abstract][hide abstract] ABSTRACT: We have demonstrated Fabry–Perot single spatial mode antimonide-based type-I quantum-well ridge waveguide semiconductor diode lasers operating at 3.0–3.2 µm wavelength in continuous mode up to 333 K. Internal optical loss in narrow ridge devices was significantly reduced by using thick Si3N4 dielectric films for planarization. The fabricated lasers operate in CW mode at room temperature with output powers exceeding 5 mW and have power consumption of less than 0.2 W at the output power of 1 mW, which is the power level needed in many gas sensing applications.
Semiconductor Science and Technology 08/2011; 26(9):095024. · 1.92 Impact Factor