Extremely low excess noise InAlAs avalanche photodiodes

Excess noise factors < 4 at avalanche gain of 10 measured on a series of p⁺in⁺ InAlAs diodes with avalanche regions ranging from 0.11 mum to 2.53 mum. Extremely low excess noise, corresponding to effective ionization coefficient ratios, k, of 0.15 < k < 0.25, showed the potential of InAlAs as multiplication region for avalanche photodiodes. Breakdown voltage obtained from multiplication characteristics of these diodes showed a linear dependence of breakdown voltage on the avalanche width. Using tunnelling parameters derived from current-voltage measurements with the ionization coefficients and threshold energies derived from gain and excess noise measurements, our calculations showed that InAlAs avalanche photodiodes have sensitivities of ~28.8 dBm assuming a rather high pre-amplifier noise of 15 pAHz^-1/2.