Low-Noise Digital Alloy Avalanche Photodiodes

Avalanche photodiodes (APDs) can provide higher sensitivity than p-i-n photodiodes owing to their internal gain. However, the gain, which originates from impact ionization is also a source of noise. Recently, using AlxIn1-xAsySb1-y grown as a digital alloy we have demonstrated APDs with noise as low as Si at telecommunication wavelengths (1300 nm to 1550 nm). In this paper, we report on additional AlInGaAsSb digital alloys and demonstrate noise suppression relative to random alloys. This is related to the fundamental issue of transport in ordered materials and provides the potential for "designer APDs" covering a broad range of spectral bands.