Growth of in situ As doped Hg1−xCdxTe by molecular beam epitaxy and activation of As at 250 °C is reported. We have used elemental arsenic, As4, as the p-type dopant source. The activation of As was observed in the 1016–1018 cm−3 range after a low temperature annealing step at 250 °C. However, for doping levels above 5×1018 cm−3, we have observed that the As activation efficiency drops. It is speculated at this time that self-compensation and formation of neutral As complexes may limit doping efficiency at very high levels. We also report our data on the structural and electrical characteristics of these As doped p-type layers using secondary ion mass spectroscopy analysis, and Hall effect measurements. An acceptor activation energy of 5.4 meV was obtained based on the dependence of the Hall coefficient on temperature. This value was attributed to singly ionized As located on a Te site (AsTe•) acting as an acceptor. A brief discussion on activation mechanism of As doped p-type HgCdTe material is also presented.

We report a process to fabricate planar Hg1−yCdyTe/Hg1−xCdxTe (x<y) heterostructure photodiodes with the p-on-n configuration. The material used for this demonstration was grown by molecular beam epitaxy. The p-on-n planar devices consist of an arsenic-doped p-type epilayer (y=0.28) on top of a long wavelength infrared n-type epilayer (x=0.225, λ=10 μm). The planar junctions were formed by selective pocket diffusion of arsenic deposited by ion implantation. The detailed analysis of the current-voltage characteristics of these diodes as a function of temperature show that they have high performance and that their dark currents are diffusion limited down to 52 K. The results also show that the R0A values for these devices are highly uniform at 77 K.

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We have developed a low temperature procedure for molecular beam epitaxy of CdTe buffer layers on {211} Si wafers and have used Si/ZnTe/CdTe composite substrates for molecular beam epitaxy of double layer Hg1−xCdxTe heterostructures. Planar p-on-n double layer heterostructures were formed by an implantation technique and test diodes were fabricated and characterized. At 77 K, devices with 30×30 μm2 junction area had R0A values in the range 1.5×106–1×107Ω cm2 with a uniform cut-off wavelength of 4.65 μm.