HgCdTe LWIR p-on-n photodiodes formed by arsenic diffusion from the vapor phase

We report current-voltage data for back-illuminated mesa photodiode test structures fabricated by arsenic-diffusion into n-type LPE HgCdTe films. Arsenic diffusion was carried out in a sealed quartz ampoule containing a source of both Hg and As. The arsenic-diffused p-on-n photodiodes were characterized at 70 K and 80 K. The cutoff wavelength was about 11 μm at 80 K. The data for 400 μm diameter photodiodes fabricated by the arsenic diffusion process are very similar to those from a conventional two-layer LPE P-on-n process for material with approximately the same cutoff wavelength. We outline process and doping level changes that should improve detector performance.