Fabrication and characterization of two-color midwavelength/long wavelength HgCdTe infrared detectors

High-performance 20-mu m unit-cell two-color detectors using an n-p(+)-n HgCdTe triple-layer heterojunction (TLHJ) device architecture grown by molecular beam epitaxy (MBE) on (211)-oriented CdZnTe substrates with midwave-length (MW) infrared and long wavelength (LW) infrared spectral bands have been demonstrated. Detectors with nominal MW and LW cut-off wavelengths of 5.5 mu m and 10.5 mu m, respectively, exhibit 78 K LW performance with > 70 % quantum efficiency, reverse bias dark currents below 300 pA, and RA products (zero field of view, 150-mV bias) in excess of 1 X 10(3) Omega cm(2). Temperature-dependent current-voltage (I-V) detector measurements show diffusion-limited LW dark current performance extending to temperatures below 70 K with good operating bias stability (150 mV 50 mV). These results reflect the successful implementation of MBE-grown TLHJ detector designs and the introduction of advanced photolithography techniques with inductively coupled plasma (ICP) etching to achieve high aspect ratio mesa delineation of individual detector elements with benefits to detector performance. These detector improvements complement the development of high operability large format 640 X 480 and 1280 X 720 two-color HgCdTe infrared focal plane arrays (FPAs) to support third generation forward looking infrared (FLIR) systems.