High performance SWIR HgCdTe detector arrays

Short wave infrared (SWIR) devices have been fabricated using Rockwell's double layer planar heterostructure (DI;PH) architecture with arsenic-ion implanted junctions. Molecular beam epitaxially grown HgCdTe/CdZnTe multilayer structures allowed the thin, tailored device geometries (typical active layer thickness was similar to 3.5 mu m and cap layer thickness was similar to 0.4 mu m) to be grown. A planar-mesa geometry that preserved the passivation advantages of the DLPH structure with enhanced optical collection improved the performance. Test detectors showed Band 7 detectors performing near the radiative limit (similar to 3-5X below theory). Band 5 detector performance was similar to 4-50X lower than radiative limited performance, apparently due to Shockley-Hall-Read recombination. We have fabricated SWIR HgCdTe 256 x 12 x 2 arrays of 45 mu m x 45 mu m detector on 45 mu m x 60 mu m centers and with cutoff wavelength which allows coverage of the Landsat Band 5 (1.5-1.75 mu m) and Landsat Band 7 (2.08-2.35 mu m) spectral regions. The hybridizable arrays have four subarrays, each having a different detector architecture. One of the Band 7 hybrids has demonstrated performance approaching the radiative theoretical limit for temperatures from 250 to 295K, consistent with test results. D* performance at 250K of the best subarray was high, with an operability of similar to 99% at 10(12) cm Hz(1/2)/W at a few mV bias. We have observed 1/f noise below 8E-17 AHz(-1/2) at 1 Hz. Also for Band 7 test structures, Ge thin film diffractive microlenses fabricated directly on the back side of the CdZnTe substrate showed the ability to increase the effective collection area of small (nominally <20 mu m mu m)planar-mesa diodes to the microlens size of 48 mu m. Using microlenses allows array performance to exceed 1-D theory up to a factor of 5.