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We report the implementation of recent advances in metalorganic chemical vapor deposition (MOCVD) for in situ growth of four-layer HgCdTe mid wave/ long wave (MW/LW) simultaneous dual-band 64 • 64 infrared detector arrays. This independently accessed, simultaneous, double-heterojunction p-n-N-P dualband detector has two back-to-back stacked photodiodes grown on CdZnTe (100) substrates. The LW photodiode is a p-on-n heterojunction grown on top of an MW N-on-P heterojunction photodiode. Secondary ion mass spectrometry depth profiles of these 28 pm thick p-n-N-P dual-band films show four well-defined regions of alloy composition and doping, and agree well with the device design. 64 x 64 arrays of dual-band detectors were fabricated from these films using electron cyclotron resonance dry etching and CdTe passivation, and hybridized to a dual-band readout chip. Two bump inter-connects in each unit cell provide independent electrical access to the back-to-back MW and LW photodiodes, and allow the MW and LW photocurrents to be separate and independent. The dualband infrared focal plane arrays (IRFPAs) spectral response data at 78K are well-behaved and are fully consistent with that observed in individual singleband LW p-on-n and MW N-on-P heterojunction devices of the same design. The hybridized 64 x 64 dual-band FPAs have MW and LW average in-band quantum efficiencies of 79 and 67%, and median D* values of 4.8 z 1011 and 7.1 x 10 l~ cm-~/Hz/W, in the respective spectral bands at 78K. The data demonstrate that MOCVD has progressed significantly toward being a practical and viable vapor phase in situ growth technology for advanced bandgap-engineered HgCdTe detector arrays.

Recent results on MOVPE growth of multilayer two-color HgCdTe detectors, for simultaneous and independent detection of medium wavelength (MW, 3–5 μm) and long wavelength (LW, 8–12 μm) bands, are reported. The structures are grown in situ on lattice matched (100) CdZnTe in the double-heterojunction p-n-N-P configuration. A barrier layer is placed between the LW and MW absorber layers to prevent diffusion of MW photocarriers into the LW junction and thereby eliminate spectral crosstalk. X-ray double crystal rocking curve widths are ∼ 45 arc-secs, indicating good epitaxial quality. SIMS depth profile measurements of these 28 μm thick structures show well-defined alloy compositions, and arsenic and iodine doping. SIMS data on a series of thirteen films show that good run-to-run repeatability is obtained on thicknesses, compositions, and dopant levels with values close to the device design targets. Depth profile of etch pits through the thickness of the films show etch pit densities in the range of 8×105-5×106 cm−2.

We report on the technology we are developing to produce photovoltaic devices of HgCdTe which are sensitive in the short wave region of the solar radiation and exhibiting detectivity performance close to theoretical limits imposed by the fundamental properties of the material.Photodiodes were fabricated in a p on n device configuration, where the n-type base layer acts as the absorber layer and the p-type layer is a wider band gap HgCdTe layer with a higher fraction of Cd than in the base layer.For a cut-off wavelength of 2 tm , external Quantum efficiency as high as 69% and RA value of 3xl03 ohm-cm2 at zero bias (going up to 4x104 ohm-cm2 at -lOOmV bias and up to l.5xl05 ohm-cm2 at -200mV bias) have been demonstrated at 300 K.