Nonlinear mechanisms in microwave photodetectors operated with high intrinsic region electric fields

Measurements and simulations to determine the contributing nonlinear mechanisms in microwave photodetectors operated with high intrinsic region electric fields are presented. An important component of the nonlinear behavior is attributed to absorption in undepleted material adjacent to the depletion region, limiting the attainable device linearity. With as little as 10 nm of undepleted absorbing material, the second harmonic of a 5 GHz fundamental frequency at 1 mA of average detector current can be −60 dBc. Linearity improvements up to 50 dB should be possible if photodetectors can be fabricated with strictly depleted absorbing regions.