A. Joullié

Observation of room-temperature laser emission from type III InAs/GaSb multiple quantum well structures

Multiple quantum well InAs/GaSb laser heterostructures with type III (type II broken gap) band alignment in the active region have been grown by molecular beam epitaxy. Intense electroluminescence was observed at room temperature (RT) with peak emission wavelengths in the range 1.95–3.4 μm. RT lasing has been achieved at 1.98 and 2.32 μm for the structures with 6 and 12 A thick InAs quantum wells, respectively.

Refractive indices of AlSb and GaSb‐lattice‐matched AlxGa1−xAsySb1−y in the transparent wavelength region

The refractive indices of AlSb grown by the solute diffusion method and GaSb‐lattice‐matched AlxGa1−xAsySb1−y alloy grown by liquid‐phase epitaxy have been determined at room temperature from accurate measurements of the reflectance of p‐polarized light as a function of the angle of incidence. The refractive index variations versus the photon energy were obtained in the spectral range 0.5–1.5 eV. Experimental data in the transparent wavelength region could be matched by calculated curves on the basis of a single‐oscillator model.

GaSb-based mid-infrared 2–5 μm laser diodes

Laser diodes emitting at room temperature in continuous wave regime (CW) in the mid-infrared (2–5 μm spectral domain) are needed for applications such as high sensitivity gas analysis by tunable diode laser absorption spectroscopy (TDLAS) and environmental monitoring. Such semiconductor devices do not exist today, with the exception of type-I GaInAsSb/AlGaAsSb quantum well laser diodes which show excellent room temperature performance, but only in the 2.0–2.6 μm wavelength range. Beyond 2.6 μm, type-II GaInAsSb/GaSb QW lasers, type-III ‘W’ InAs/GaInSb lasers, and interband quantum cascade lasers employing the InAs/Ga(In)Sb/AlSb system, all based on GaSb substrate, are competitive technologies to reach the goal of room temperature CW operation. These different technologies are discussed in this paper. To cite this article: A. Joullie, P. Christol, C. R. Physique 4 (2003).

2.5 μm GaInAsSb lattice‐matched to GaSb by liquid phase epitaxy

GaSb lattice‐matched Ga1−xInxAsySb1−y has been grown by liquid phase epitaxy on (100) and (111)B oriented substrates using initial melt supersaturation ΔT varying from 10 to 30 °C, at growth temperatures >600 °C. It is shown that the band‐gap cutoff wavelength, measured at room temperature by the electroreflectance method, is ∼2.38 μm for (100) layers whatever ΔT, and increases from 2.38 μm up to 2.51 μm for (111)B oriented layers when ΔT is increased from 15 to 25 °C. Photoluminescence experiments at 2 K confirm the band‐gap reduction occurring at high ΔT with the (111)B orientation.

Recombination processes in midinfrared InGaAsSb diode lasers emitting at 2.37μm

The temperature dependence of the threshold current of InGaAsSb∕AlGaAsSb compressively strained lasers is investigated by analyzing the spontaneous emission from working laser devices through a window formed in the substrate metallization and by applying high pressures. It is found that nonradiative recombination accounts for 80% of the threshold current at room temperature and is responsible for the high temperature sensitivity. The authors suggest that Auger recombination involving hot holes is suppressed in these devices because the spin-orbit splitting energy is larger than the band gap, but other Auger processes persist and are responsible for the low T0 values.

High temperature liquid phase epitaxy of (100) oriented GaInAsSb near the miscibility gap boundary

Abstract The Ga 1- x In x As y Sb 1- y quaternary alloy has been grown by liquid phase epitaxy at high temperature ( T = 600–615° C) on (100) oriented GaSb substrate. The highest indium concentration in the solid phase that could be achieved for perfect GaSb-lattice-matched layers was x = 0.23, which corresponds to a band-gap cut off wavelength λ = 2.39 μm at room temperature. Thermodynamical calculations show this composition ( x = 0.23 y = 0.20) is situated at the boundary of the solid phase miscibility gap (binodal curve). Mismatched quaternary layers with more indium content (up to x = 0.52) could be grown outside the miscibility gap, but their morphology was bad.

Pressure-tuned InGaAsSb∕AlGaAsSb diode laser with 700nm tuning range

InGaAsSb∕AlGaAsSb type-I midinfrared diode lasers emitting continuous wave at 2.4μm at room temperature have been studied under high hydrostatic pressure. When the pressure was increased up to 19kbar, the threshold current varied from 240to400A∕cm2, showing a minimum of 200A∕cm2 close to 8kbar, and the emission spectra shifted to shorter wavelengths by up to 700nm (i.e., from 2.4μmto1.7μm). This exceptional tuning range could be very useful in tunable diode laser absorption spectroscopy.

Type-II InAsSb/InAs strained quantum-well laser diodes emitting at 3.5 μm

Mid-infrared laser diodes with compressively strained InAsSb/InAs type-II slightly coupled quantum wells are reported. These lasers, grown on InAs by molecular-beam epitaxy, have emission wavelength near 3.5 μm. They exhibit pulsed operation up to 220 K, with at 90 K threshold current density of 150 A/cm2. Ridge lasers continuous wave (cw) operated up to 130 K with cw output power of 40 mW/A/facet and a characteristic temperature T0=40 K.

GaInSb/AlGaAsSb strained quantum well semiconductor lasers for 1.55 m operation

Gallium antimonide and related compounds are promising materials for fabricating monolithic vertical cavity semiconductor lasers operating at telecommunications wavelengths. With that aim active layers based on multiquantum wells have been evaluated by means of a separate-confinement laser diode structure grown on a GaSb substrate by molecular beam epitaxy. Owing to optimization of the growing process, for the well/barrier structure, laser emission at 1.4 m has been obtained at 80 K with a threshold current as low as 15 mA for a 640 m long and 15 m wide mesa stripe structure. At room temperature laser emission occurred at 1.55 m with a pulsed threshold current density of 4 kA according to the measured characteristic temperature of 50 K. In a first attempt such an active layer has been included in a 1.5 m microcavity involving antimonide Bragg mirrors.

Growth limitations by the miscibility gap in liquid phase epitaxy of Ga1−xInxAsySb1−y on GaSb

The boundary line (binodal curve) of the solid phase miscibility gap of the Ga1−xInxAsySb1−y quaternary alloy has been calculated from the regular solution model, taking into account the latticemismatched strain energy induced by a GaSb substrate. A calculation suggests that the miscibility gap is reduced and epitaxial layers might be deposited over the entire range of lattice-matched compositions at 615°C. Ga1−xInxAsySb1−y epitaxial layers have been grown by liquid phase epitaxy on (100)- and (111)B- oriented GaSb substrates. The lattice-matched epitaxial layers which were richest in indium (x = 0.23) for the (100) orientation and x = 0.26 for the (111)B orientation have compositions located in the vicinity of the boundary of the miscibility gap calculated ignoring the strain energy, showing that stabilization by the substrate is far less effective than predicted.