Impact ionization coefficients and excess noise characteristics of <i>Al0.85Ga0.15As0.07Sb0.93</i> 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.