C-QWIP material design and growth

Recently, large format and high quantum efficiency corrugated quantum well infrared photodetector (C-QWIP) FPAs have been demonstrated. Since the detector light coupling scheme does not alter the intrinsic absorption spectrum of the material, the QWIPs can now be designed with different bandwidths and lineshapes to suit various applications. Meanwhile, the internal optical field distribution of the C-QWIPs is different from that of a grating coupled detector, the material structure thus should be designed and optimized differently with respect to quantum efficiency, conversion efficiency and operating temperature. In this paper, we will provide a framework for the material design. Specifically, we will present a theoretical detector performance model and discuss two specific examples, namely with 9.2 and 10.2 μm cutoff wavelengths. We found that for both λ_c, the photocurrent to dark current ratio is maximized at an electron doping density N_D of 0.28 × 10¹⁸ cm^-3. The dark current limited detectivity meanwhile reaches a maximum at a higher N_D of 0.45 × 10¹⁸ cm^-3. But the lowest noise equivalent noise temperature difference is actually obtained at an even higher N_D of 1.0 × 10¹⁸ cm^-3 due to the larger quantum efficiency, if there are no limitations on the readout charge capacity. These predictions are compared with the data of a 1024 × 1024 C-QWIP FPA hybridized to a fan-out circuit, and the results are consistent.