Excess noise characteristics of Al/sub 0.8/Ga/sub 0.2/As avalanche photodiodes

The avalanche noise characteristics of Al/sub 0.8/Ga/sub 0.2/As have been measured in a range of p-i-n and n-i-p diodes with i-region widths /spl omega/ varying from 1.02 to 0.02 μm. While thick bulk diodes exhibit low excess noise from electron initiated multiplication, owing to the large /spl alpha///spl beta/ ratio (1/k), the excess noise of diodes with /spl omega/ < 0.31 μm were found to be greatly reduced by the effects of dead space. The thinnest diodes exhibit very low excess noise, corresponding to k = 0.08, up to a multiplication value of 90. In contrast to most III-V materials, it was found that both thick and thin Al/sub 0.8/Ga/sub 0.2/As multiplication layers can give very low excess noise and that electrons must initiate multiplication to minimize excess noise, even in thin structures.