Mid-infrared gallium-indium-antimony/aluminum-gallium-indium-antimony MQW laser grown on aluminum-indium-antimony metamorphic buffer layers

There is a growing need for antimonide-based, room temperature, 2–5 μm, semiconductor lasers for trace gas spectroscopy, ultra-low loss communication, infrared countermeasures, and ladar. High power, low threshold lasers using InGa(As)Sb type-I quantum wells with emission wavelengths near 2 μm have been demonstrated. However, to extend the wavelength beyond 2 μm, increased arsenic content has been needed to reduce the bandgap and maintain a lattice match to GaSb. This has resulted in degraded performance due in part to a smaller valence band offset. In this work, the need for lattice match between the active region and the GaSb substrate is avoided by the use of metamorphic AlInSb buffer layers. This provides a virtual substrate to extend the wavelength of GaInSb quantum wells. With the use of lattice constants larger than GaSb, the need for arsenic has been eliminated resulting in pure antimonide crystals, which provides for large valence band offsets.; The performance of various types of antimonide-based mid-infrared lasers is explored. The methods for predicting material parameters are developed including a bandgap with a cubic dependence as determined by photoluminescence of bulk GaInSb. The numerical calculations employed to predict the band structure of type-I and type-II quantum wells are demonstrated including a statement of higher order methods.; Samples are grown by solid source molecular beam epitaxy. The AlInSb metamorphic buffer layer is a superlattice consisting of alternating layers of Al_xIn_1−xSb and Al_yIn_1−y Sb where the indium content and thickness ratios are chosen to provide the desired average indium content. After growth of a suitable number of periods, the superlattice is step-graded until the desired lattice constant is achieved. The strain across the superlattice heterojunction is instrumental in preventing dislocations from threading into the active region.; Using these buffer layers, optically pumped GalnSb/AlGalnSb multiple quantum well lasers with as much as 76% indium content in the quantum well and emission wavelength as long as 3.3 μm at room temperature have been achieved. The best performing room temperature laser emits at 2.8 μm with a threshold power density of 169 W/cm2 and a differential quantum efficiency of 28%.