Mid-wavelength infrared p-on-n Hg1-xCdxTe heterostructure detectors: 30-120 kelvin state-of-the-art performance

Authors report on Hg1-xCdxTe mid-wavelength ir (MWIR) detectors grown by MBE on CdZnTe substrates. I-V characteristics of HgCdTe-MWIR devices and temperature dependence of focal-plane array (FPA) dark current have been investigated and compared with the most recent InSb published data. These MWIR p-on-n Hg1-xCdxTe/CdZnTe heterostructure detectors give outstanding performance, and at 68 K, they are limited by diffusion currents. For temperatures lower than 68 K, in the near small-bias region, another current is dominant. This current has lower sensitivity to temperature and most likely is of tunneling origin. High-performance MWIR devices and arrays were fabricated with median RoA values of 3.96 x 1010 OMEGA-cm2 at 78 K and 1.27 x 1012 OMEGA-cm2 at 60 K; the quantum efficiency (QE) without an antireflection (AR) coating was 73% for a cutoff wavelength of 5.3 mum at 78 K. The QE measurement was performed with a narrow pass filter centered at 3.5 mum. Many large-format MWIR 1024 x 1024 FPAs were fabricated and tested as a function of temperature to confirm the ultra-low dark currents observed in individual devices. The 1024 x 1024 array operability and AR-coated QE at 78 K were 99.48% and 88.3%, resp. A comparison of these results with the state-of-the-art InSb-detector data suggests MWIR-HgCdTe devices have significantly higher performance in the 30-120 K temperature range. The InSb detectors are dominated by generation-recombination currents in the 60-120 K temperature range because of a defect center in the energy gap, whereas MWIR-HgCdTe detectors do not exhibit G-R-type currents in this temperature range and are limited by diffusion currents. 9 refs.