Excess Noise Characteristics of Thin AlAsSb APDs

Characterization of AlAsSb avalanche photodiodes (APDs) with avalanche region widthswof 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 ofk= 0.1,k= 0.15, andk= 0.21, wherekis the effective ionization coefficient ratio, for the APDs withw= 80 nm. Under the same carrier injection conditions, the APDs withw= 230 nm exhibit even lower noise corresponding tok= 0.05,k= 0.12, andk= 0.17. The lowest excess noise achieved, withk= 0.05, is significantly lower than those obtained in InP and InAlAs APDs with the samew.