Efficient analysis of large two-dimensional arbitrarily shaped finite gratings for quantum well infrared photodetectors

In this work, a recently developed full-wave electromagnetic analysis technique is applied to the simulation of two-dimensional finite quasi-random and rough surface gratings for quantum well infrared photodetectors. This new steepest descent fast multipole method (SDFMM) is a mathematically rigorous technique that permits the rapid and accurate solution of the electric field integral equation governing scattering from a quasi-planar structure. In the present application, it enables the efficient and accurate simulation of scattering by finite two-dimensional grating structures interfacing with GaAs. Grating absorption is predicted by evaluating the scattered optical electric field component at the device layer along the growth direction. Numerical examples illustrating the functional dependence of the absorption on grating parameters and wavelength are discussed. The simulation approach presented here should prove to be a useful tool for the a priori design of novel aperiodic, quasi-random and rough surface two-dimensional gratings for infrared imaging applications.