Large area InAlAs/InGaAs metal semiconductor metal photodiode with very low dark current and its frequency response

Abstract

An MBE grown InGaAs metal semiconductor metal (MSM) photodiode (PD) with an InAlAs barrier enhancement layer is reported that has very low dark current and high speed characteristics. The detector using Cr/Au Schottky metal ®ngers with 4 lm spacing on a large active area of 300 300 lm2 shows a low dark current of 38 nA at 10 V. This corresponds to a dark current density of 0:42 pA=lm2 and is, to our knowledge, the best dark current ever obtained from a large area InGaAs MSM PD. The device also shows a low capacitance of 0:8 pF and a high 3 dB bandwidth of 2:4GHz. By ®tting the measured frequency response to a model consisting of both RC time and transit time limited responses, we show that the device has an RC time and a transit time limited 3 dB bandwidth of 3.0 and 4:9 GHz, respectively.