Physical modelling of GaAs photodiodes

The bipolar drift-diffusion model of an ITO/GaAs Schottky photodiode has been used to demonstrate the importance of photogenerated charge build up within the photodiode when used in detecting high bit rate digital signals. This causes an asymmetrical response affecting the detected high and low levels which become dependent on the digital pulse pattern. Optical illumination at wavelengths ⩽880 nm is through the ITO which is transparent to these frequencies. These devices have been fabricated where the depth of the intrinsic n^- layer ranges from 10 μm to 0.45 μm with the smallest having a reported bandwidth of 110 GHz