We are developing two-layer LPE P-on-n HgCdTe photovoltaic detector arrays with cutoff wavelengths out to 17 μm for a NASA spaceborne infrared radiometer. These bilinear multiplexed arrays will operate at 60 K, and must achieve sensitivities approaching the background limit for a background photon flux of 2×1015 photons/cm2-sec. The detectors must operate at reverse bias voltage to interface with silicon CMOS multiplexer circuits, and must exhibit low 1/f noise.
This paper reviews progress toward these demanding requirements. The limiting junction current mechanisms for HgCdTe photodiodes at these very long cutoff wavelengths are reviewed. Data are presented for both CdTe-passivated and ZnS-passivated arrays at 60 K with cutoff wavelengths of 15.4−16.9 μm. Average R0A products of 13 ohm-cm2 and quantum efficiencies of 89% have been achieved for cutoff wavelengths of 15.4 μm at 60 K. These array data demonstrate the potential for VLWIR PV HgCdTe to meet the requirements for advanced NASA applications.