AlGaAsSb Barriers Research Articles

GaSb-based type-I quantum well cascade diode lasers emitting at nearly 2-μm wavelength with digitally grown AlGaAsSb gradient layers* *Project supported by the Major Program of the National Natural Science Foundation of China (Grant No. 61790581) and the Key Area Research and Development Program of Guangdong Province, China (Grant No. 2020B0303020001).

We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength. The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector. The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper. And the quantum well cascade laser with 100-μm-wide, 2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature. The characteristic temperature T 0 is estimated at above 60 K.

2.1 μm InGaSb quantum well lasers exhibiting the maximum conversion efficiency of 27.5% with digitally grown AlGaAsSb barriers and gradient layers

Abstract The 2.1-μm-wavelength InGaSb/AlGaAsSb/GaSb double quantum well lasers, exhibiting a high performance with the peak output power of 1.62 W and the maximum conversion efficiency of 27.5%, had been grown by molecular-beam-epitaxy (MBE). Digitally grown AlxGa1-xAsSb barriers and grading layers were employed in the devices to increase the valence-band offset and to improve the simplicity and controllability of MBE growth. The quaternary digital alloys were grown with short-period superlattices (SPS) of AlSb, AlAs and GaSb and varieties of growth conditions such as growth temperature, interface control and growth rate were considered to get the high-quality crystal films. The digitally grown film was parametrically characterized by atomic force microscopy, high resolution X-ray and transmission electron microscope, showing a smooth surface, clear satellite peaks and clear growth cross sections, respectively. Besides the good power performance of the devices, a low threshold current density of 60 A/cm2 was also achieved and the calculated differential resistance was 0.17 Ω.

High performance GaSb based digital-grown InGaSb/AlGaAsSb mid-infrared lasers and bars**Project supported by the National Natural Science Foundation of China (Grant Nos. 61790580 and 61435012), the National Basic Research Program of China (Grant No. 2014CB643903), and the Scientific Instrument Developing Project of the Chinese Academy of Sciences (Grant No. YJKYYQ20170032).

InGaSb/AlGaAsSb double-quantum-well diode lasers emitting around 2 μm are demonstrated. The AlGaAsSb barriers of the lasers are grown with digital alloy techniques consisting of binary AlSb/AlAs/GaSb short-period pairs. Peak power conversion efficiency of 26% and an efficiency higher than 16% at 1 W are achieved at continuous-wave operation for a 2-mm-long and 100-μm-wide stripe laser. The maximum output power of a single emitter reaches to 1.4 W at 7 A. 19-emitter bars with maximum efficiency higher than 20% and maximum power of 16 W are fabricated. Lasers with the short-period-pair barriers are proved to have improved temperature properties and wavelength stabilities. The characteristic temperature (T0) is up to 140 °C near room temperature (25–55 °C).

Reprint of “Mid-infrared InAsSb-based nBn photodetectors with AlGaAsSb barrier layers – grown on GaAs, using an interfacial misfit array, and on native GaSb”

InAsSb-based nBn photodetectors were fabricated on GaAs, using the interfacial misfit (IMF) array growth mode, and on native GaSb. At −0.1V operating bias, 200K dark current densities of 1.4×10−5Acm−2 (on GaAs) and 4.8×10−6Acm−2 (on GaSb) were measured. At the same temperature, specific detectivity (D*) figures of 1.2×1010Jones (on GaAs) and 7.2×1010Jones (on GaSb) were calculated. Arrhenius plots of the dark current densities yielded activation energies of 0.37eV (on GaAs) and 0.42eV (on GaSb). These values are close to the 4K bandgap of the absorption layers (0.32–0.35eV) indicating diffusion limited dark currents and small valence band offsets. Significantly, these devices could be used for mid-infrared focal plane arrays operating within the temperature range of cost-effective thermoelectric coolers.

GaSb-based composite quantum wells for laser diodes operating in the telecom wavelength range near 1.55-μm

We have investigated in detail the material, optical, and lasing properties of innovative GaInSb/AlInSb composite quantum wells (CQWs). The CQWs are confined by AlGaAsSb barrier layers, and a monolayer-thin AlInSb barrier layer has been inserted within the GaInSb QWs in order to achieve lasing emission within the telecom window. High-resolution X-ray diffraction, transmission electron microscopy, and photoluminescence spectroscopies reveal high structural quality of the samples. Inserting AlInSb layers allows wider QWs, and thus higher gain-material volume and CQW/optical mode overlap. This translates into better laser performances. Near room temperature, a threshold current of 85 mA and an output power of ∼30 mW/uncoated-facet under continuous wave operation are demonstrated at 1.55 μm with 10 μm × 1 mm laser diodes.

Mid-infrared InAsSb-based nBn photodetectors with AlGaAsSb barrier layers – Grown on GaAs, using an interfacial misfit array, and on native GaSb

InAsSb-based nBn photodetectors were fabricated on GaAs, using the interfacial misfit (IMF) array growth mode, and on native GaSb. At −0.1V operating bias, 200K dark current densities of 1.4×10−5Acm−2 (on GaAs) and 4.8×10−6Acm−2 (on GaSb) were measured. At the same temperature, specific detectivity (D*) figures of 1.2×1010Jones (on GaAs) and 7.2×1010Jones (on GaSb) were calculated. Arrhenius plots of the dark current densities yielded activation energies of 0.37eV (on GaAs) and 0.42eV (on GaSb). These values are close to the 4K bandgap of the absorption layers (0.32–0.35eV) indicating diffusion limited dark currents and small valence band offsets. Significantly, these devices could be used for mid-infrared focal plane arrays operating within the temperature range of cost-effective thermoelectric coolers.

GaSb-based, 2.2 μm type-I laser fabricated on GaAs substrate operating continuous wave at room temperature

We report on a Sb-based type-I laser grown on GaAs substrate, emitting continuous wave at room temperature around 2.2 μm. The device was grown using solid-source molecular beam epitaxy and comprised two GaInAsSb quantum wells embedded in AlGaAsSb barriers. Despite the large lattice mismatch, a good crystalline quality was obtained, and processed devices operated continuous wave up to 50 °C with threshold current densities in the range of 1.5–2.2 kA/cm2. An optical output power of 3.7 mW was obtained at 20 °C.

Advances in Type-I GaSb Based Lasers

We show that high level of compressive strain in the optically active quantum wells is a key condition for efficient continuous-wave room-temperature operation of the type-I GaSb-based diode lasers. Lasers with two highly strained InGaAsSb quantum wells and AlGaAsSb barriers demonstrate an output CW power of 1050 mW at 2.4 µm and 85 mW at 3.1 µm.

Midinfrared InGaAsSb quantum well lasers with digitally grown tensile-strained AlGaAsSb barriers

The InGaAsSb lasers emitting in the midinfrared with strain-compensated multiple-quantum-well (MQW) active region have been grown by solid-source molecular-beam epitaxy (MBE). Digitally grown tensile-strained AlGaAsSb was employed as barriers to increase the valence-band offset for hole confinement. The laser structures were characterized by reflection high-energy electron diffraction, x-ray diffraction, and photoluminescence. The digital-growth approach for the tensile-strained AlGaAsSb barriers improved the reliability and controllability of MBE growth for the MQW active region. The optical and structural qualities of InGaAsSb MQW were improved significantly as compared to those with random-alloy barriers due to the removal of growth interruption at the barrier/well interfaces in digital growth. As a result, high-performance devices were achieved in the InGaAsSb lasers with digital AlGaAsSb barriers. A low threshold current density of 163A∕cm2 at room temperature was achieved for 1000-μm-long lasers emi...

Tunable Laser Diode System for Noninvasive Blood Glucose Measurements

Optical sensing of glucose would allow more frequent monitoring and tighter glucose control for people with diabetes. The key to a successful optical noninvasive measurement of glucose is the collection of an optical spectrum with a very high signal-to-noise ratio in a spectral region with significant glucose absorption. Unfortunately, the optical throughput of skin is low due to absorption and scattering. To overcome these difficulties, we have developed a high-brightness tunable laser system for measurements in the 2.0-2.5 microm wavelength range. The system is based on a 2.3 microm wavelength, strained quantum-well laser diode incorporating GaInAsSb wells and AlGaAsSb barrier and cladding layers. Wavelength control is provided by coupling the laser diode to an external cavity that includes an acousto-optic tunable filter. Tuning ranges of greater than 110 nm have been obtained. Because the tunable filter has no moving parts, scans can be completed very quickly, typically in less than 10 ms. We describe the performance of the present laser system and avenues for extending the tuning range beyond 400 nm.

Strain-compensated InGaAsSb multiple quantum-wells with digital AlGaAsSb barriers for midinfrared lasers

Midinfrared InGaAsSb-AlGaAsSb strain-compensated multiple quantum-wells (SCMQW) have been grown by solid-source molecular beam epitaxy. Short-period (AlGaAsSb)/sub y/--(AlGaSb)/sub 1-y/ digital barriers were employed to avoid growth interruptions at the barrier-well interfaces, thereby significantly improving the structural and optical properties of the InGaAsSb SCMQW as evidenced by X-ray diffraction and photoluminescence measurements. Based on these high-quality SCMQW, a room-temperature threshold current density as low as 163 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was achieved for 1000-μm-long broad-area lasers emitting at 2.38 μm in pulsed mode. The 880-μm-long lasers retained a high characteristic temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) of 165 K up to 80/spl deg/C and could operate at temperatures above 100/spl deg/C. A typical wavelength blueshift of 38 meV was observed in the SCMQW laser samples compared to the SCMQW-only samples.

Midinfrared InAs∕InGaSb “W” diode lasers with digitally grown tensile-strained AlGaAsSb barriers

W-shaped InAs∕In0.2Ga0.8Sb∕InAs∕Al0.25Ga0.75As0.08Sb0.92 quantum wells (QWs) have been grown by solid-source molecular beam epitaxy for midinfrared wavelength emission. The tensile strain and the higher As composition in the tensile AlGaAsSb barriers lower the energy level of the heavy holes and increase the hole confinement in the “W” quantum wells, which can improve the temperature properties of the “W” lasers. The tensile-strained Al0.25Ga0.75As0.08Sb0.92 barriers were obtained by growing Al0.25Ga0.75Sb(2ML)∕Al0.25Ga0.75As0.24Sb0.76 (1 ML) digital layers. As evidenced from low-temperature photoluminescence (PL) and x-ray diffraction measurements, the “W” QWs with digitally grown AlGaAsSb barriers show better interface quality and higher PL efficiency than analogous structures with random-alloy AlGaAsSb barriers. Broad-area diode lasers with five-period “W” QWs have been fabricated. A low threshold of 734A∕cm2 at a lasing wavelength of 3.238μm was measured for the 800μm×200μm stripe at 153K. Characteristic temperatures as high as 103K are achieved in the 80–150K range.

Epitaxial growth of InGaAsSb/AlGaAsSb heterostructures for mid-infrared lasers based on strain engineering

An approach based on strain engineering to fabricate GaSb-based type I InGaAsSb/AlGaAsSb mid-infrared laser diodes emitting at long wavelengths is presented. By incorporating a high arsenic fraction (above 2.1%) in the AlGaAsSb barriers, a tensile strain is created to compensate the compressive strain in the InGaAsSb wells. Calculations are presented to show how, while maintaining a low average strain in the active region, a low well bandgap energy and an increased valence band offset resulting in a better hole confinement can be obtained. Strain compensation is investigated experimentally by x-ray diffraction and photoluminescence. Double quantum well laser diodes were grown on GaSb by molecular-beam epitaxy. Stable room temperature pulsed lasing emission at 2.89 μm, the longest wavelength ever reported for this type of structure, was observed along with a threshold current density of 920 A/cm2.

Study of AlGaAsSb/InGaAsSb strained quantum well grown by molecular beam epitaxy on GaSb(100)

Al 0.2Ga 0.8As 0.02Sb 0.98/In 0.24Ga 0.76As 0.05Sb 0.95 strained quantum well structures were successfully grown by solid source molecular beam epitaxy. X-Ray rocking curves and reciprocal space mapping were applied to determine the strain status of epilayers. Photoluminescence was used to investigate band alignment of AlGaAsSb/InGaAsSb quantum wells. For samples with low Al concentration barrier, type II band alignment was found in such structures. The optical transition is between bound state in conduction band and continuous state in valence band. If the Al concentration in AlGaAsSb barrier increases, the band alignment changes to type I. The optical transition is between bound states. Due to the 0.5% lattice mismatch between AlGaAsSb layer and GaSb substrate, a thick barrier will lead to relaxation, and this has been proven by PL measurements.

2.78 μm InGaAsSb/AlGaAsSb multiple quantum-well lasers with metastable InGaAsSb wells grown by molecular beam epitaxy

Multiple quantum-well (MQW) lasers with metastable InGaAsSb quantum wells and AlGaAsSb barriers and claddings were grown on n +− GaSb(100) substrates by molecular beam epitaxy. The lasers exhibited a lasing wavelength of 2.78 μm and pulsed operation up to 60°C. Pulsed threshold current of 1.1 A, corresponding to a current density of 9.5 kA/cm 2, and maximum output power of 30 mW have been achieved at 15°C for broad-area lasers. The characteristic temperature was 58 K over the temperature range of 0 to 40°C. This is the longest emission wavelength reported for quantum-well lasers operating at room temperature.

High-power, high-temperature operation of GaInAsSb-AlGaAsSb ridge-waveguide lasers emitting at 1.9 &amp;#x03BC;m

Ridge-waveguide lasers emitting at /spl sim/1.9 /spl mu/m have been fabricated from a multiple-quantum-well heterostructure with an active region consisting of five GaInAsSb wells and six AlGaAsSb barriers. At room temperature, single-ended cw output power as high as 100 mW has been obtained. The maximum cw operating temperature is 130/spl deg/C, with a characteristic temperature of 85 K between 20 and 80/spl deg/C. >

High-power GaInAsSb-AlGaAsSb multiple-quantum-well diode lasers emitting at 1.9 /spl mu/m

High-power diode lasers emitting at /spl sim/1.9 μm have been fabricated from a quantum-well heterostructure having an active region consisting of five GaInAsSb wells and six AlGaAsSb barriers. For devices 300 μm wide and 1000 μm long, single-ended output power as high as 1.3 W cw has been obtained with an initial differential quantum efficiency of 47%. The pulsed threshold current density is as low as 143 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for 2000-μm-long devices.

Low-threshold GaInAsSb/AlGaAsSb quantum-well ridge-waveguide lasers emitting at 2.1 mu m

The authors report on a laser structure consisting of the following layers grown on an n-GaSb substrate by molecular beam epitaxy: n-GaSb buffer, n-AlGaAsSb cladding, active consisting of GaInAsSb wells and AlGaAsSb barriers, p-AlGaAsSb cladding, and p/sup +/-GaSb contacting. Ridges 8- mu m wide were defined by reactive ion etching. For CW operation of a 300- mu m-long device at a heat-sink temperature of 20 degrees C, the threshold current is 29 mA and the maximum power is 12.5 mW/facet limited by junction heating. Initial slope efficiency is approximately 0.1 W/A per facet. Fundamental-mode emission is maintained up to 200 mA, with lateral full width at half maximum (FWHM) of 15 degrees . For the transverse far-field pattern, the FWHM is approximately 50 degrees . The emission spectra show multiple longitudinal modes at approximately 2.13 mu m.