Corrugated QWIP array fabrication and characterization

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Abstract
A corrugated quantum well IR photodetector (C-QWIP) focal plane array (FPA) with cutoff at 11.2 micrometers has been fabricated and characterized. The C-QWIP array uses total internal reflection to couple normal incident light into the pixels. The processing steps involve only one chemical etching, one optional reactive ion etching, and one ohmic contact metalization. The detector array has 256 X 256 pixel elements, indium bumped to a direct injection readout circuit. The photocurrent to dark current ratio measured in this FPA, on which the noise equivalent temperature difference depends, is consistent with that of a large area test sample. The array shows good responsivity uniformity of 5.2 percent with no extra leakage resulted from array processing. The estimated noise equivalent temperature difference of this array, excluding the readout noise, is 17 mK at T equals 63 K. The fact that this FPA can be operated at a temperature similar to those of standard QWIP arrays with much shorter wavelengths shows that the C-QWIP structure can greatly increase array performance.

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