Excess noise in GaAs avalanche photodiodes with thin multiplication regions

It is well known that the gain-bandwidth product of an avalanche photodiode can be increased by utilizing a thin multiplication region. Previously, measurements of the excess noise factor of InP-InGaAsP-InGaAs avalanche photodiodes with separate absorption and multiplication regions indicated that this approach could also be employed to reduce the multiplication noise. This paper presents a systematic study of the noise characteristics of GaAs homojunction avalanche photodiodes with different multiplication layer thicknesses. It is demonstrated that there is a definite "size effect" for multiplication regions less than approximately 0.5 /spl mu/m. A good fit to the experimental data has been achieved using a discrete, nonlocalized model for the impact ionization process.