This paper presents the status of HgCdTe growth on large-area Si and CdZnTe substrates at Raytheon Vision Systems (RVS). The different technological tools that were used to scale up the growth from 4 inch to 6 inch diameter on Si and from 4 cm 9 4 cm to 8 cm 9 8 cm on CdZnTe without sacrificing the quality of the layers are described. Extremely high compositional uniformity and low macrodefect density were achieved for single-and two-color HgCdTe layers on both Si and CdZnTe substrates. Finally, a few examples of detector and focal-plane array results are included to highlight the importance of high compositional uniformity and uniformly low macrodefect density of the epitaxial layers in obtaining high operability and low cluster outages in single-and two-color focal-plane arrays (FPAs).

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HgCdTe grown on large-area Si substrates allows for larger array formats and potentially reduced focal-plane array (FPA) cost compared with smaller, more expensive CdZnTe substrates. The goal of this work is to evaluate the use of HgCdTe/Si for mid-wavelength/long-wavelength infrared (MWIR/LWIR) dualband FPAs. A series of MWIR/LWIR dual-band HgCdTe triple-layer n-P-n heterojunction (TLHJ) device structures were grown by molecular-beam epitaxy (MBE) on 100-mm (211)Si substrates. The wafers showed low macrodefect density (<300 cm À2 ) and was processed into 20-lm-unit-cell 640 9 480 detector arrays which were mated to dual-band readout integrated circuits (ROICs) to produce FPAs. The measured 80-K cutoff wavelengths were 5.5 lm for MWIR and 9.4 lm for LWIR, respectively. The FPAs exhibited high pixel operabilities in each band, with noise equivalent differential temperature (NEDT) operabilities of 99.98% for the MWIR band and 99.6% for the LWIR band demonstrated at 84 K.

This work investigates the use of photon trapping structures in HgCdTe detectors for use in mid-wavelength infrared (MWIR) detectors. Model results based on finite-difference time-domain electromagnetic simulation and a finite-element model of electronic performance are compared with Fouriertransfer infrared (FTIR) spectroscopy and measured device performance results. Reduced fill factor devices with lowered dark current and no appreciable decrease in quantum efficiency are demonstrated. This is compared against devices with reduced fill factor but no photon trapping capability, which exhibit reduced dark current but also reduced quantum efficiency.

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