Characteristics of GaAs and AlGaAs homojunction avalanche photodiodes with thin multiplication regions

The gain and noise of thin GaAs and ${\mathrm{Al}}_{\mathrm{0.2}}{\mathrm{Ga}}_{\mathrm{0.8}}\mathrm{As}$ homojunction avalanche photodiodes were measured. The gain and the excess noise factor were found to be significantly lower than would be expected using ionization coefficients reported in the literature. The discrepancy is believed to be due to physical effects that become significant in thin multiplication layers. It is shown that the gain and excess noise under electron injection can be accurately fit using conventional models with width-dependent ionization coefficients.