Study On Optical Coupling Performance Of Very Long-Wavelength Quantum Well Infrared Photodectors

In the past several years, the technology of Quantum Well Infrared Photodetectors (QWIP) has been developed rapidly. Compared with the conventional Hg_xCd_1-xTe infrared photodetectors, the QWIP technology values a great superiority in product rate, since it can fabricate an imaging system with large area, low power, low cost, high uniformity and high sensitivity focal plane array (FPA).However, the normal incidence infrared radiation can't be absorbed in the n type GaAs QWIP which is applied proverbially, because of the select rule of quantum absorption. Therefore, in order to enhance the responsivity and detectivity of the device, we have to fabricate some special structure or device such as edge coupler, grating, random reflector and Corrugated QWIP (C-QWIP).The paper studied the electrics performance and the optical performance of the QWIP fabricated with GaAs/AlGaAs super lattice material. The content includes:(1) We have discussed several computational model of energy level in super lattice quantum well briefly, because of the need of wavelength. We also have made a primary analysis on the responsivity and detectivity of the device. We have discussed the mechanism of dark current in the GaAs QWIP and made some optimization as well.(2) We have introduced the design idea, advancement and limitation of all the optical coupling models and made some exactly study on different coupling model based on model expand method (MEM), and finite element model (FEM). Contents include:(a) How to optimize the design of edge coupling from the investigation of absorption coefficient.(b) The design of the structure parameter of the 2-d grating and random reflector in the QWIP device.(c) Investigate the influence made by some special figure such as basin-shaped grating, ladder-shaped grating and column grating that may be formed in the dry etch progress.(d) Make an analysis and comparison between 45 edge coupler, 2-d grating and C-QWIP.The innovation of this paper includes:(1) Included all the possible diffractive wave from zero to infinitude order, we have calculated the best structure parameter of 2-d grating in very long-wavelength QWIPs.