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Wide spectral response of two-dimensional grating for quantum well infrared detector and wideband bound/quasi-bound QWIPs

By defining a grating coupling efficiency for quantum well infrared photodetectors (QWIPs) and including all possible high order diffracted waves, the authors calculate the spectral response of grating for QWIPs on the basis of modal expansion method (MEM). Numerical simulations show that the two dimensional grating can cover very wide spectral range, including 3 - 5 micrometer and 8 - 12 micrometer. The influence of the depth of grating and cavity width on the spectral response has been shown. A method of improving the response bandwidth of grating coupled QWIPs has been realized. A wideband bound-quasibound type QWIP has been fabricated. The measured detectivity (80 K) at the wavelength of 6.6 micrometer, 7.8 micrometer, 9.0 micrometer and 9.5 micrometer are 2.6 multiplied by 109, 2.1 multiplied by 109,4.8 multiplied by 109 and 4.4 multiplied by 109 cmHz1/2/W, respectively. The experiment has a good agreement with the theoretical results.