Low-noise infrared digital-alloy avalanche photodiodes

Abstract

Avalanche photodiodes (APDs) can provide high receiver sensitivity owing to their internal gain, however, the impact ionization gain mechanism is also a source of noise. Recently, AlxIn1-xAsySb1-y grown as a digital alloy has been used to fabricate APDs with excess noise as low as Si (k ~ 0.01). Operation of these APDs at telecommunication wavelengths (1300 nm to 1550 nm) or 2 µm has been achieved. This paper also discusses staircase APDs, which utilize compositional grading to mimic the dynodes of a photomultiplier tube, with a gain of 2x arising at each step providing extremely low noise avalanche gain.