Characterization of p-on-n HgCdTe diffusion photodiodes

Medium- and long-wavelength infrared (MWIR and LWIR) Hg1-xCdxTe photodiodes (x equals 0.265 - 0.295, 0.205 - 0.220) for 3 - 5-micrometer and 8 - 12- micrometer wavelength spectral regions were fabricated by arsenic diffusion from the vapor source into the n-type HgCdTe bulk single crystals. The temperature dependence of current- voltage and capacity-voltage characteristics, and the photodiode speed response, were analyzed. For 3 - 5-micrometer photodiodes with the electron concentration 3 multiplied by 1015 cm-3 in the base n-type layer, the typical resistance-area product at zero bias RoA was about 104 (Omega) cm2 at 77 K. For 8 - 12 micrometer photodiodes with the same electron concentrations in the base region, the RoA product values of 1 - 10 (Omega) cm2 were obtained. The typical photoresponse speeds were in the range of 50 ns and 20 - 30 ns for 3 - 5-micrometer and 8 - 12-micrometer photodiodes, respectively. The dark current of fabricated photodiodes was tunneling limited at 77 K, and generation-recombination and diffusion limited at higher temperatures.