EXCESS NOISE IN GAAS AVALANCHE PHOTODIODES WITH THIN MULTIPLICATION REGIONS

It is well known that the gain-bandwidth product of an avalanche photo diode can be increased by utilizing a thin multiplication region. Prev iously, measurements of the excess noise factor of InP-InCaAsP-InGaAs avalanche photodiodes with separate absorption and multiplication regi ons indicated that this approach could also he employed to reduce the multiplication noise, This paper presents a systematic study of the no ise characteristics of GaAs homojunction avalanche photodiodes with di fferent multiplication layer thicknesses, It is demonstrated that ther e is a definite ''size effect'' for multiplication regions less than a pproximately 0.5 mu m. A good fit to the experimental data has been ac hieved using a discrete, nonlocalized model for the impact ionization process.