Low avalanche excess noise in thin Al/sub x/Ga/sub 1-x/As (x=0.15 and 0.60) avalanche photodiodes

Abstract

Avalanche photodiodes with thin avalanche multiplication regions were found to exhibit lower excess noise than those predicted by the conventional local noise theory. Experimental excess noise measurements on a range of sub-micron Al/sub 0.6/Ga/sub 0.4/As and Al/sub 0.15/Ga/sub 0.85/As homojunction p/sup +/in/sup +/ diodes show that the excess noise decreases as the avalanche width is reduced below 1 /spl mu/m. The Al/sub 0.6/Ga/sub 0.4/As p/sup +/in/sup +/ diodes show extremely low excess noise despite the electron and hole ionization coefficients being very similar. Modelling using a nonlocal model indicates that dead space plays an important role in determining the excess noise in thin avalanching regions.