Proceedings Article | 24 June 2014
Proc. SPIE. 9070, Infrared Technology and Applications XL
KEYWORDS: Quantum efficiency, Sensors, Staring arrays, Quantum well infrared photodetectors, Absorption, Quantum wells, Gold, Resonators, Diffraction gratings, Semiconducting wafers
The quantum efficiency of QWIPs is difficult to predict and optimize. Recently, we have established a quantitative 3- dimensional electromagnetic model for QE computation. In this work, we used this model to design and optimize new detector structures. In one approach, we adjusted the detector volume to resonate strongly with the scattered light from the diffractive elements (DEs). The resulting intensified field increases the detector QE correspondingly. We tested this resonator-QWIP concept on four detector materials and obtained satisfactory agreements between theory and experiment. The observed single detector QE ranges from 15 to 71%, depending on the realized pixel geometry and the matching detector material. We processed one of the materials into hybridized FPAs and observed a QE of 30% with a conversion efficiency of 11%, in agreement with theory. By using rings as DEs, the FPA spectral nonuniformity can also be minimized with an observed value of 4% in comparison with the 7% for gratings. With a proven EM model, we further designed different R-QWIPs for a wide range of applications, including high conversion efficiency detection, narrow band detection through a medium, narrow band detection at a gaseous medium, simultaneous two-color detection, sequential voltage tunable two-color detection, and broadband detection at Landsat wavelengths. Experimental efforts are underway.
