Modeling of the terahertz response of metal-semiconductor-metal photodetectors

Abstract

In this paper a two-dimensional ensemble Monte Carlo particle method is used to simulate the metal-semiconductor-metal (MSM) photodetector response in the terahertz range of signal frequencies. We consider planar MSM photodetectors consisting of a GaAs absorbing layer with a system of Schottky contacts made 'back-to-back' on the above layer. The model takes into account the features of the carrier energy spectra, mechanisms of their scattering and a self-consistent electric field. The intrinsic transient response triggered by an ultra-short light pulse is calculated. The MSM frequency response is calculated using the Fourier transform of the obtained temporal dependences. It is shown that due to velocity overshoot effect exhibited by the photoelectrons, the MSM photodetector reveals rather high response to terahertz signals even if the contact spacing is relatively large. The frequency response of the MSM photodetectors utilizing the photoelectron velocity overshoot effect is compared with that of the MSM photodetectors with ultra-short carrier lifetime.