Impact ionization coefficients and excess noise characteristics of Al0.85Ga0.15As0.07Sb0.93 on GaSb substrate

Abstract

We report the multiplication properties of Al0.85Ga0.15As0.07Sb0.93 for use in separate absorption charge and multiplication avalanche photodiode lattice matched to a GaSb substrate. The demonstration of a high gain, low excess noise multiplier lattice matched to GaSb is a critical step toward high performance avalanche photodiodes operating at wavelengths exceeding 2 μm. We have measured impact ionization coefficients of random alloy Al0.85Ga0.15As0.07Sb0.93 grown on GaSb substrates from 210 to 421 kV/cm. Our results show an α value (0.25–40×103 cm−1) significantly greater than β (0.002–4.8×103 cm−1) over the measured field range, indicating this material is a favorable multiplier candidate for electron avalanche photodiodes. We also report excess noise measurements of both p-i-n and n-i-p devices under illumination, resulting in single carrier injection. The p-i-n devices showed a low excess noise of 2.98 at a maximum gain of ∼17, while the n-i-p devices showed a high excess noise of 9.34 at a gain of ∼8, further implicating that this material predominantly multiplies electrons.