Polarisation-insensitive high-speed InGaAs metal-semiconductor-metalphotodetectors

Abstract
High-speed InGaAs metal-semiconductor-metal (MSM) photodetectors with circularly shaped finger electrodes have been fabricated in order to minimise the strong polarisation dependence of the responsivity of conventional MSM detectors with linear finger electrodes. Under front illumination with 1.55 µm light, the circular devices with electrode feature sizes as small as 0.6 µm are demonstrated to be virtually free of polarisation effects. High-speed performance (3 dB bandwidth up to 18.5 GHz) is also reported.