Optimized random/ordered grating for an n-type quantum well infrared photodetector

Coupling efficiency of infrared radiation to electron intersubband transiti on in quantum well infrared photodetector by a two-dimensional (2D) grooved grating is examined. A resonant enhancement of the coupling efficiency at a certain optimal groove depth is predicted and confirmed experimentally. I t is argued that a detector with a properly designed ordered cross grating performs better than a detector with optimized 2D random grating. In a dete ctor with ordered grating a quantum efficiency of 75% is obtained with a do ping level of only 3.5x10(17) cm(-3) in each quantum well and dark current density of 0.34 mA/cm(2) at 78 K. (C) 1999 American Institute of Physics. [ S0003- 6951(99)00243-0].