Low threshold, room temperature laser diode pumped Sb-based VECSEL emitting around 2.1 /spl mu/m

The operation of a diode-pumped AlGaAsSb/GaInAsSb type-I quantum-well vertical external cavity surface emitting laser (VECSEL) emitting near 2.1 /spl mu/m is reported. The epitaxial structure, grown on GaSb by molecular beam epitaxy consists of a GaSb/AlAsSb Bragg reflector and a GaInAsSb/AlGaAsSb active region. A TEM/sub 00/ low-divergence laser operation is demonstrated in quasi-CW (10 /spl mu/s pulses, 10% duty cycle) from 250 up to 350 K. A threshold as low as 390 W/cm/sup 2/ at 250 K combined with a T/sub 0/ around 33 K has been measured.     

Mid-infrared GaSb-based EP-VCSELl emitting at 2.63 μm

Electrically-pumped GaSb-based vertical-cavity surface-emitting lasers emitting up to 2.63 μm at room temperature are reported. The whole structure was grown monolithically in one run by solid-source molecular beam epitaxy. This heterostructure is composed of two n-doped AlAsSb/GaSb DBRs, a type-I GaInAsSb/AlGaAsSb multiquantum- well active region and an InAsSb/GaSb tunnel junction. A quasi-CW (1 μs, 5 %) operation was obtained at room temperature for 35 μm-diameter devices with threshold current of 85 mA.     

Long wavelength GaInAsSb-AlGaAsSb distributed-feedback lasers emitting at 2.84 /spl mu/m

Room-temperature continuous-wave operation of a singlemode GaInAsSb/GaSb/AlGaAsSb distributed feedback (DFB) laser is presented at a record long emission wavelength for this material system of 2.843 /spl mu/m. The threshold current at 20/spl deg/C is 75 mA. Mode selection was realised by metal gratings laterally patterned to a ridge waveguide. By varying the grating period, DFB emission from 2.738 up to 2.843 /spl mu/m is obtained.     

Room-temperature, monolithic, electrically-pumped type-L quantum-well SB-based VCSELS emitting at 2.3 mm

An all-epitaxial monolithic vertical cavity surface emitting laser grown on GaSb substrate is presented. The structure is composed of two n-doped AlAsSb/GaSb distributed Bragg reflectors, a type-I GalnAsSb/AlGaAsSb multi-quantum-well active region and a tunnel junction. Quasi continuous-wave laser operation is demonstrated at 2.3 mum up to room temperature. Threshold current densities of 0.8 and 0.6 kA/cm^-2 are obtained at 300 and 280 K for 80 mum-diameter devices (1 mus pulses, 10% duty cycle). A peak output optical power of 2 mW was achieved at 280 K.     

2.61 /spl mu/m GaInAsSb/AlGaAsSb type I quantum well laser diodes with low threshold

Double quantum well laser diodes based on the GaInAsSb/AlGaAsSb system emitting at 2.61 /spl mu/m in continuous-wave regime have been fabricated. In the pulsed regime for a 100 /spl mu/m-wide 1600 /spl mu/m-long device a record threshold current density of 76 A/cm/sup 2/ per quantum well was obtained.     

Light-emitting diodes based on GaSb alloys for the 1.6–4.4 μm mid-infrared spectral range

The available publications concerned with fabrication and study of light-emitting diodes (LEDs) intended for operation in the 1.6–4.4 μm spectral range; based on GaSb substrates; and grown by liquid-phase epitaxy, which makes it possible to form fairly thick layers lattice-matched to GaSb, are reviewed. In these studies, the active region consists of the GaInAsSb compound in LEDs for the spectral ranges 1.8–2.4 and 3.4–4.4 μm and the AlGaAsSb compound for the spectral region 1.6–1.8 μm. The wide-gap AlGaAsSb confining layers contain up to 64% of Al, which is an unprecedentedly high content for liquid-phase epitaxy. Asymmetric (GaSb/GaInAsSb/AlGaAsSb) and symmetric (AlGaAsSb/GaInAsSb/AlGaAsSb) heterostructures have been fabricated and studied. Various types of designs that make it possible to improve the yield of radiation generated in the active region have been developed. The measured external quantum yield of emission is as high as 6.0% at 300 K for the LEDs operating at the wavelengths 1.9–2.2 μm. A pulsed optical-radiation power of 7 mW at a current of 300 mA with a duty factor of 0.5 and 190 mW at a current of 1.4 A with a duty factor of 0.005 have been obtained. The external quantum emission yield of ～1% has been obtained for LEDs that emit in the spectral range 3.4–4.4 μm; this yield exceeds that obtained for the known InAsSb/InAsSbP heterostructure grown on an InAs substrate by a factor of 3. The measured lifetime of minority charge carriers (5–0 ns) is close to the theoretical lifetime if only the radiative recombination and impact CHCC bulk recombination are taken into account. The impact recombination is prevalent at temperatures higher than 200 K for LEDs operating in the spectral range 3.4–4.4 μm and at temperatures higher than 300 K for LEDs operating in the spectral range 1.6–2.4 μm.     

OMVPE growth of GaInAsSb/AlGaAsSb for quantum-well diode lasers

GaInAsSb and AlGaAsSb alloys have been grown by organometallic vapor phase epitaxy (OMVPE) using all organometallic sources, which include tritertiarybutylaluminum, triethylgallium, trimethylindium, tertiarybutylarsine (TBAs), and trimethylantimony. Excellent control of lattice-matching both alloys to GaSb substrates is achieved with TBAs. GaInAsSb/AlGaAsSb multiple quantum well (MQW) structures grown by OMVPE exhibit strong 4K photoluminescence with full width at half maximum of 10 meV, which is comparable to values reported for quantum well (QW) structures grown by molecular beam epitaxy. Furthermore, we have grown GaInAsSb/AlGaAsSb MQW diode lasers which consist of n- and p-doped Al_0.59Ga_0.41As_0.05Sb_0.95 cladding layers, Al_0.28Ga_0.72As_0.02Sb_0.98 confining layers, and four 15 nm thick Ga_0.87In_0.13As_0.12Sb_0.88 quantum wells with 20 nm thick Al_0.28Ga_0.72As_0.02Sb_0.98 barrier layers. These lasers, emitting at 2.1 μm, have exhibited room-temperature pulsed threshold current densities as low as 1.2 kA/cm².     

Wafer bonding and epitaxial transfer of GaSb-based epitaxy to GaAs for monolithic interconnection of thermophotovoltaic devices

GaInAsSb/AlGaAsSb/InAsSb/GaSb epitaxial layers were bonded to semi-insulating (SI) GaAs handle wafers with SiO_x/Ti/Au as the adhesion layer for monolithic interconnection of thermophotovolatic (TPV) devices. Epitaxial transfer was completed by removal of the GaSb substrate, GaSb buffer, and InAsSb etch-stop layer by selective chemical etching. The SiO_x/Ti/Au provides not only electrical isolation, but also high reflectivity and is used as an internal backsurface reflector (BSR). Characterization of wafer-bonded (WB) epitaxy by high-resolution x-ray diffraction (HRXRD) and time-decay photoluminescence (PL) indicates minimal residual stress and enhancement in optical quality. The 0.54-eV GaInAsSb cells were fabricated and monolithically interconnected in series. A ten-junction device exhibited linear voltage building with an opencircuit voltage of 1.8 V.     

Tunable photodetectors based on strain compensated GaInAsSb/AlAsSbmultiple quantum wells grown by molecular beam epitaxy

GaInAsSb/AlGaAsSb strain compensated multiple quantum well (MQW) p-i-n structures grown by molecular beam epitaxy on GaSb substrates have been successfully fabricated into tunable photodiodes, which showed a large photoresponse peak shift up to 30 meV (80 nm) at 77 K under a reverse bias of 10 V due to quantum confined Stark effect (QCSE). The QCSE persists up to room temperature and the values of the excitonic absorption peak shifts agree well with the calculated results. Based on the observed QCSE, an electrically tunable resonant cavity enhanced photodetector with strain compensated MQW structure is proposed and modeled     

2.0 ?m c.w. operation of GaInAsSb/GaSb d.h. lasers at 80 K

GaInAsSb/GaSb double-heterostructure (d.h.) lasers were fabricated by liquid-phase-epitaxial growth. C.W. operation was realised at 80 K with a wavelength of 2.0 ?m. From measurement of laser thresholds as a function of temperature, it was shown that threshold currents for pulsed operation are described by the expression I(T) ? exp (T/T0), where T0 = 58 K.     

Reduction of threshold current density of 2.2?m GaInAsSb/AlGaAsSb injection lasers

GaInAsSb/AlGaAsSb injection lasers have been fabricated with increased Al concentration in the cladding layers. As a result of improved optical and electrical confinement, the threshold current density Jth for these double heterostructures was a factor of two lower than reported previously; CW operation was achieved up to 235 K.     

High-power, high-temperature operation of GaInAsSb-AlGaAsSbridge-waveguide lasers emitting at 1.9 μm

Ridge-waveguide lasers emitting at ~1.9 μm 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°C, with a characteristic temperature of 85 K between 20 and 80°C     

Diminution des densités de courant de seuil dans le cas d’une structure planaire antiguidante de type GaSb/GalnAsSb/GaSb par adjonction d’une couche métallique

The propagating optical modes in antiguiding GaSb/ GaInAsSb/GaSb heterostructures are studied. Experiments have shown that laser action can be obtained in these heterostructures in spite of the fact that the active GaInAsSb refractive index is lower than that of GaSb. Our calculations show that if a reflecting gold coating is introduced at the appropriate distance from the active layer the gain in the active layer required to achieve a net positive gain for the guided wave is significantly reduced. This configuration is equivalent to a pair of antiguiding layers. It should lead to a significant reduction in threshold current. The threshold current has been calculated and compared with that of a simple thick antiguiding layer having the same composition.     

2.3-μm High-Power Type I Quantum-Well GaInAsSb/AlGaAsSb/GaSb Laser Diode Arrays with Increased Fill Factor

Arrays of 100-μm-wide GaInAsSb/AlGaAsSb laser diode emitters with a fill factor of 30% have been fabricated. Suppression of lateral lasing was achieved by the incorporation of grooves between the emitters. A quasi-continuous wave (CW) (30 μs, 300 Hz) output power of 16.7 W from a 4-mm-long laser bar has been demonstrated.     

High-power GaInAsSb-AlGaAsSb multiple-quantum-well diode lasersemitting at 1.9 μm

High-power diode lasers emitting at ~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/cm² for 2000-μm-long devices     

Demonstration of 3.5 μm Ga1-xInxSb/InAssuperlattice diode laser

A demonstration of a semiconductor diode laser based on a type-II Ga _1-xIn_xSb/InAs superlattice active layer is reported. The laser structure uses InAs/AlSb superlattice cladding layers and a multiquantum well active layer with GaInAsSb barriers and Ga_1-xIn_xSb/InAs-superlattice wells. An emission wavelength of 3.47 μm for pulsed operation up to 160 K is observed     

Hole-well antimonide laser diodes on GaSb operating near 2.93 /spl mu/m

The operation of electrically-pumped type-II Sb-based laser diodes in which only the holes are quantum confined is reported. These laser structures were fabricated by molecular beam epitaxy on (001) GaSb substrates. In the multi-quantum well region, radiative recombinations originate from InGaSb hole wells embedded in InGaAsSb barriers lattice-matched to GaSb. Laser operation was demonstrated from such structures up to 243 K at 2.93 mum in the pulsed regime (200 ns, 5 kHz). A minimum threshold of about 12.8 kW/cm² combined with a T₀ around 70 K have been measured     

2.6 μm GaSB based photonic crystal coupled cavity lasers

Long wavelength GaInAsSb/AlGaAsSb quantum wells lasers have been grown by molecular beam epitaxy and processed into ridge cavities coupled by an intracavity photonic crystal mirror, to enhance the laser spectral properties. The devices operate in the continuous-wave regime at room temperature with a single frequency emission at 2.6 m.     

Molecular beam epitaxy growth of InGaSb/AlGaAsSb strained quantum well diode lasers

2μm InGaSb/AlGaAsSb strained quantum wells and a tellurium-doped GaSb buffer layer were grown by molecular beam epitaxy（MBE）.The growth parameters of strained quantum wells were optimized by AFM, XRD and PL at 77 K.The optimal growth temperature of quantum wells is 440℃.The PL peak wavelength of quantum wells at 300 K is 1.98μm,and the FWHM is 115 nm.Tellurium-doped GaSb buffer layers were optimized by Hall measurement.The optimal doping concentration is 1.127×10¹⁸ cm^-3 and the resistivity is 5.295×10^-3Ω·cm.     

Photodiodes for a 1.5–4.8 µm spectral range based on type-II GaSb/InGaAsSb heterostructures

Long-wavelength photodiodes based on LPE-grown type-II heterostructures in lattice-matched GaSb/InGaAsSb/GaInAsSb and GaSb/InGaAsSb/AlGaAsSb systems were fabricated and studied. Band energy diagram engineering for heterostructures with wide-and narrow-gap layers allows the photodiode parameters to be controlled by varying the conditions at heterointerfaces. Electrical and photoelectric characteristics and the dark current mechanisms in the heterostructures were investigated. The optimal photodiode structure was selected that consists of two type-II broken-gap heterojunctions and one p-n-junction in the narrow-gap active layer. Room-temperature detectivity D _λ ^* Hz^1/2/W at λ=4.7 µm was obtained. Type-II heterostructures may help develop high-efficiency uncooled photodiodes for the 1.6–4.8 µm range for gas analysis, environmental monitoring, and also the diagnostics of combustion and explosion products.