Negative luminescence from large-area HgCdTe photodiode arrays with 4.8-6.0-μm cutoff wavelengths

We demonstrate the substantial suppression of infrared (IR) blackbody emission from HgCdTe photodiode arrays with cutoff wavelengths of 4.8, 5.5, and 6.0 μm. At room temperature, a reverse bias induces internal negative luminescence (NL) efficiencies of 95%, 93%, and 88%, respectively, which correspond to apparent cooling of the surface temperatures by 60, 59, and 49 K. Reverse-bias saturation current densities for the three devices were 0.11, 0.7, and 32 A/cm². Measurement and analysis of the material transmission characteristics indicate that the small residual inefficiencies may be limited by a parasitic absorption process. The 4.8 and 5.5 μm photodiodes were fabricated into 18 × 2 arrays with total areas of 5 mm × 5 mm. In both cases, all 36 array elements were fully operable, and had similar electrical and NL properties. Effective fill factors were ≈100%, since carrier diffusion led to the extraction of carriers from regions between the elements. These results show that efficient, low-power NL devices with active areas in the square-inch range are now feasible for such applications as the cold shielding of infrared focal-plane arrays.