THEORETICAL-STUDY OF DEVICE SENSITIVITY AND GAIN SATURATION OF SEPARATE ABSORPTION, GRADING, CHARGE, AND MULTIPLICATION INP INGAAS AVALANCHE PHOTODIODES/

In this paper, we present a theoretical investigation into the perform ance of a separate absorption, grading, charge, and multiplication InP /InGaAs photodiode (SAGCM) using a two-dimensional drift-diffusion mod el, The analysis examines the sensitivity of the device performance to variations within the overall geometry of the photodiode. Specificall y, we explore modifications to the p(+) diffusion at the surface of th e device, the thickness of the multiplication region, and the relative doping within the mesa charge sheet, It is found that variations with in the design specifications may lead to considerable perturbations in the current-voltage response. In addition to the sensitivity analysis , the extent of gain saturation due to space charge effects within the diode is investigated, The effect of gain saturation is observed to a gree with analytical based predictions, To the authors' knowledge, thi s is the first demonstration of gain saturation due to space charge ef fects in a SAGCM APD.