Low-Noise Mid-Wavelength Infrared Avalanche Photodiodes

Mid-wavelength infrared (MWIR) p ⁺–n ⁻–n ⁺ avalanche photodiodes (APDs) were fabricated using two materials systems, one with mercury cadmium telluride (HgCdTe) on a silicon (Si) substrate and the other with an indium arsenide/gallium antimonide (InAs/GaSb) strained layer superlattice (SLS). Diode characteristics, avalanche characteristics, and excess noise factors were measured for both sets of devices. Maximum zero-bias resistance times active area (R ₀ A) of 3 × 10⁶ Ω cm² and 1.1 × 10⁶ Ω cm² and maximum multiplication gains of 1250 at −10 V and 1800 at −20 V were measured for the HgCdTe and the SLS, respectively, at 77 K. Gains reduce to 200 in either case at 120 K. Excess noise factors were almost constant with increasing gain and were measured in the range of 1 to 1.2.