AlGaAsSb/InGaAsSb on GaSb, Infrared, Separate Absorption and Multiplication, Avalanche Photodiodes

AstroPower proposes to develop high performance, room temperature, mass-producible, low-cost infrared detectors using liquid-phase heteroepitaxy of lattice-matched InGaAsSb and AlGaAsSb on GaSb substrates. The structure of these detectors will be a Separate Absorption and Multiplication Avalanche Photodiode (SAM-APD). This structure has proven to be an effective means of producing large gain in the absence of large dark current. With proper composition InGaAsSb can be prepared with band gap adjustable in wavelength from 1.7 to 4.5 mm. The major advantage of using quaternary systems over binary and ternary compounds is the ability to vary the band gap while still providing lattice matched growth to the substrate material. Another expected advantage is that this detector structure will have good detectivity at room temperature while most commercially available detectors need cooling to liquid nitrogen temperatures. AstroPower has previous experience in the growth of these material systems. Liquid phase epitaxy has routinely provided quality III-V detectors and photovoltaic cells with the highest optical-to-electrical energy conversion efficiency, and has significant cost advantages over other forms of epitaxy. Feasibility of this approach will be demonstrated by the end of the Phase I program.