A novel nano-structured metal-semiconductor-metal photodetector consisting of interdigitated metal fingers and nanodots is successfully fabricated on a semi-insulating GaAs substrate by electron beam lithography, and integrated with an on-chip ground-signal-ground coplanar transmission line for pulse response measurements. The fabricated nano-structured metal-semiconductor-metal photodetector can be operated at 5 V, more than three times higher than the operating voltage of the regular metal-semiconductor-metal photodetector composed of narrowly spaced interdigitated electrodes only. Its dark current is lower than 0.5 nA until the bias voltage approaches the breakdown voltage. More importantly, it demonstrates a more than three times higher output peak voltage than the regular metal-semiconductor-metal photodetector while maintaining approximately a 10 ps pulse width that is limited by the bandwidth of the measurement setup, not by the speed of the photodetector. The transit model simulation indicates that the amplitude of the pulse response is strongly influenced by the voltage collapse across the photodetector.
Citation: Japanese Journal of Applied Physics
Pub Type: Journals
high voltage, MSM photodetector, semi-insulating GaAs