High-Responsivity InGaAs MSM Photodetectors with Semi-Transparent Schottky Contacts

High-performance metal-semiconductor-metal photodetectors (MSM-PD's) with interdigitated semi-transparent Au Schottky contacts have been fabricated on pseudomorphic In0.9Ga0.1P–InP–InGaAs heterostructure. The responsivity measured at 1.55-µm wavelength is greatly enhanced from 0.4 A/W to 0.7 A/W as the thickness of the Au electrodes is decreased to 10 nm. This corresponds to a 75% improvement over the conventional MSM-PD's with opaque metal electrodes. With a pseudomorphic InGaP barrier-enhancement layer, these devices exhibit a dark current density as low as 1.6 pA/µm2. Extremely linear photoresponse without any internal gain is also observed for these detectors. The full-width at half maximum of the temporal response for the devices with semi-transparent electrodes is about 85 ps compared to 80 ps for the conventional ones.