High-operability SWIR HgCdTe focal plane arrays

Abstract

SWIR HgCdTe photodiode test chips and 256x256 Focal Plane arrays with a 2.1 micron cutoff wavelength have been fabricated and tested. The base material was n-type HgCdTe. P-type junctions were created by ion implantation. Test chip arrays with 60-micron pixels exhibited an average R_oA of 509 ohm-cm² and internal quantum efficiency (QE) of 98% at 295 K; R_oA and QE were uniform. Average R_oA increased to 2.22x10⁴ at 250 K and internal QE remained high at 93%. The mini-array of 30-micron pixels had lower R_oA values, 152 and 6.24x10³ ohm-cm2 at 295 and 250 K, but 100% internal quantum efficiency at both temperatures. There was no bias dependence of quantum efficiency, demonstrating that our junction formation process does not give rise to valence band barriers. FPA test data have demonstrated NEI operability greater than 98% at 220 K and greater than 97% at 250 K along with QE operability in excess of 99.9% at 220 K and in excess of 99.8% at 250 K.