Excess Noise Characteristics of Thin AlAsSb APDs

Characterization of AlAsSb avalanche photodiodes (APDs) with avalanche region widths w of 80 and 230 nm showed that electron ionization coefficient is slightly higher than that for hole. The avalanche gain at a given bias is marginally higher under pure electron injection, achieved using 442-nm laser, compared to those measured under mixed carrier injections using 542- and 633-nm lasers. Low-excess-noise factors were measured, corresponding to the lines of k = 0.1, k = 0.15, and k = 0.21, where k is the effective ionization coefficient ratio, for the APDs with w = 80 nm. Under the same carrier injection conditions, the APDs with w = 230 nm exhibit even lower noise corresponding to k = 0.05, k = 0.12, and k = 0.17. The lowest excess noise achieved, with k = 0.05, is significantly lower than those obtained in InP and InAlAs APDs with the same w.