MWIR InAsSb APD Receiver

Current state-of-the-art avalanche photodiode (APD) material in mid- and long-wave infrared is HgCdTe. Because impact ionization coefficient for electrons, gamma is larger than that for holes, which enables low noise multiplication in APDs. However, significant drawbacks to HgCdTe materials such as fragility, difficulty in single-crystal growth have triggered the search for III-V/IV hybrid alternatives, employing either device structure or materials innovations.InAs, has many desirable attributes for APDs: low electron effective mass of ~0.023m0, high saturation velocity, large gamma-L and gamma-X separations that are larger than bandgap, resulting in useful gain at modest electric fields; 50% larger electric fields are required for HgCdTe.So far AlxIn1-xAsySb1-y lattice-matched to GaSb as material system due to many possible applications for AlxIn1-xAsySb1-y alloys lattice-matched to GaSb in mid-infrared (IR) and near-IR optoelectronic devices. But, still growth of this alloy have remained largely unexplored, which is due to the presence of a wide miscibility gap. However, it has recently been shown that stable AlInAsSb can be grown within the miscibility gap by molecular-beam-epitaxy as a digital alloy of component binaries, AlAs, AlSb, InAs, and InSb. We have extended this method which covers the entire direct bandgap compositional range of AlInAsSb lattice-matched to GaSb.