High speed photodetectors based on a two-dimensional electron/hole gas heterostructure

Abstract

We report on high-speed metal-semiconductor-metal (MSM) resonant cavity enhanced photodetectors based on Schottky-contacted (Al,In)GaAs heterostructures containing both electron and hole quantum wells. Interdigitated detectors were fabricated and characterized with and without an underlying Distributed Bragg Reflector (DBR). All detectors had very low dark currents and high linear responsivities. The fastest measured temporal response with a 16 ps full-width at half-maximum and a 29 ps fall time was demonstrated on a device with 1 μm gap between electrodes and an underlying DBR. Single quantum well detectors have previously demonstrated increased responsivity and speed but were limited by a slow decaying tail in the high speed photoresponse, attributed to the long collection path of minority carriers. The use of an electron and hole well, separated by a 110 nm absorption region as well as an underlying DBR, eliminates the slow tail by providing an enhanced collection path for both optically generated electrons and holes. Here, we present the fabricated device structure along with the DC and high speed photoresponse under varying incident powers. We briefly compare these results to those of the previous single well devices and attribute improvements in the time response tail to enhanced diffusion created by the presence of the separated dual well structure.