Low avalanche noise characteristics in thin InP p/sup +/-i-n/sup +/ diodes with electron initiated multiplication

We have performed electron initiated avalanche noise measurements on a range of homojunction InP p/sup +/-i-n/sup +/ diodes with "i" region widths, w ranging from 2.40 to 0.24 μm. In contrast to McIntyre's noise model a significant reduction in the excess noise factor is observed with decreasing w at a constant multiplication in spite of /spl alpha/, the electron ionization coefficient being less than /spl beta/, the hole ionization coefficient. In the w=0.24 μm structure an effective /spl beta///spl alpha/ ratio of approximately 0.4 is deduced from the excess noise factor even when electrons initiate multiplication, suggesting that hole initiated multiplication is not always necessary for the lowest avalanche noise in InP-based avalanche photodiodes.