Linear mode avalanche photodiodes (APDs) will be developed in III-V materials epitaxially grown on commercially available GaSb substrates. The detectors will have bias-controllable internal current gain greater than 10, limited excess noise, and response times shorter than 0.5 nanosecond. In Phase I, initial APDs will use InAsSb absorbers, producing response out to 4.2 micron wavelengths. Next, APDs will be developed to reach out to 5 micron wavelengths using III-V superlattice absorbers. Finally, 10-12 micron APDs will be developed in Phase II. The high performance of these APDs is enabled by the development of the advanced avalanche material AlGaAsSb, which suppresses tunneling dark currents to undetectable levels, and enables the use of large electric fields and thin (sub-micron) multiplication layers, which produce low operating voltage, low noise, and high speed.
