CORRUGATED QUANTUM-WELL INFRARED PHOTODETECTORS FOR NORMAL INCIDENT LIGHT COUPLING

In this letter, we report a quantum well infrared photodetector geomet ry for normal incidence light coupling. The new optical coupling schem e utilizes total internal reflection at the sidewalls of triangular wi res to create favorable optical polarization for infrared absorption. These wires are created by chemically etching an array of V grooves th rough the detector active region along a specific crystallographic dir ection. Experimental results from the initial single color as well as two-color detectors with linear wires and unthinned substrate show eff icient light coupling comparable to the standard 45 degrees edge coupl ing, without the undesirable wavelength dependence or spectral narrowi ng effect of a conventional grating structure. At the same time, the d ark current density is substantially reduced due to the partial materi al removal. Further improvement is expected by creating a two-dimensio nal coupling structure with substrate thinning. (C) 1996 American Inst itute of Physics.