Corrugated quantum well infrared photodetectors for material characterization

In this article, we discuss the utilities of corrugated quantum well infrared photodetectors (C-QWIPs) in detector material characterization. By measuring the detector responsivity as a function of corrugation period, several important detector parameters, such as the absorption coefficient alpha of parallel propagating light and the energy resolved photoconductive gain g, can be directly deduced. For the QWIP material presented, alpha at the peak was found to be 0.21 mu m(-1) under the usual operating condition. This value of alpha corresponds to an absorption length of 4.8 mu m. Instead of being a constant, the value of g also varies significantly across the excitation spectrum, and the peak value is larger than the noise gain at large bias. Our results show that the present characterization technique is capable of providing accurate and detailed information on the intrinsic properties of QWIP materials under actual operating conditions. It is extremely useful in detector optimization. In addition, we also show the characteristics of C-QWIPs with an additional vertical trench at the center of each corrugation to gain more insights into the distribution of light intensity in a C-QWIP structure. (C) 2000 American Institute of Physics. [S0021-8979(00)08015-4].