The detection of infrared radiation is of great importance for many defense and civilian applications. Eyesafe short-wavelength infrared (SWIR) spectral range is particularly interesting due to atmospheric propagation through obscurants. Applications include low-cost, long-range target identification, identification of heavily obscured targets, obstacle avoidance, and high resolution imaging from a variety of platforms including hand-held devices, unmanned air vehicles, or ground vehicles. HgCdTe grown on CdTe/Si by molecular beam epitaxy (MBE) was processed into mini-arrays for 1.55 μm LADAR applications. Low-capacitance photodiodes (<10 pF) were demonstrated at room temperature with frequency responses exceeding 100 MHz. This paper discusses the device architecture and device performance results.
We report the growth of HgCdTe by metal organic vapor phase epitaxy (MOVPE), using (211)B CdTe/Si substrates grown by molecular beam epitaxy (MBE). The surface morphology of these films is very smooth. Morphological defects are primarily oval type void defects with the density of 500cm<sup>-2</sup>. The etch pit densities (EPD) and full widths at half maximum (FWHM) of x-ray rocking curves exhibit that the grown epilayers replicate exactly the structural properties of substrate. The Hall parameters of undoped HgCdTe layers show anomalous n-type behavior with temperature. Long time annealing under Hg-saturated condition found to deteriorate the transport properties of HgCdTe layers resulting from the possible in corporation of impurities in the layers. Mid wave infrared (MWIR) photovoltaic devices have been fabricated from n on p HgCdTe films. The MOVPE grown films were processed into mesa type discrete devices with wet chemical etching employed for mesa delineation and ZnS surface passivation. The dynamic resistance-area product at zero bias voltage for a temperature of 77K is 4000 ohm-cm<sup>2</sup>. But R<sub>o</sub>A values are scattered drastically. In some detectors, R<sub>o</sub>A values are less than 100 ohm-cm<sup>2</sup>. It is thought that these results are related with localized defects or anomalous transport properties of epilayer.