Fabrication and evaluation of 11.2 and 16.2 μm cutoff C-QWIP arrays

Corrugated quantum well infrared photodetector (C-QWIP) focal plane arrays (FPA) with cutoff wavelength of 11.2 and 16.2 mu m were fabricated and tested. Each detector array has 256 x 256 pixel elements, indium bumped to a direct injection readout circuit manufactured by Rockwell Science Center. The rest of the supporting electronics were designed and built inhouse to provide biases and clock functions to the FPAs. Infrared imageries with good aesthetic attributes were obtained from both FPAs. For the 11.2 mu m FPA, background limited infrared performance (BLIP) was obtained at 63 K under F/2 optics, consistent with the test results of a large area detector. This operating temperature is substantially higher than the grating coupled arrays with comparable cutoff wavelengths. On the other hand, the optics of the present camera were not optimized for wavelengths beyond 14 mu m. As a result, the BLIP temperature for the 16.2 mu m FPA, observed to be 38 K, was somewhat lower than the expected 42 K from the single detector characterization Despite the reduced detector volume of a C-QWIP structure, the measured internal quantum efficiency remains to be high, being 20.5% and 25.4% at 2 V bias for the 11.2 mu m and the 16.2 mu m FPA, respectively.