Diffusion of As and Sb in HgCdTe

This paper reports the diffusion mechanisms of ion-implanted As and Sb in HgCdTe, grown by metalorgic chemical vapor deposition (MOCVD), and on the application of the resultant findings to the As diffusion from a grown source. A diffusion model was developed from a chemical analysis using secondary ion mass spectroscopy (SIMS) and a Gaussian theoretical model. The nature of the As and Sb diffusion mechanism and the various components of the diffusion profile were investigated. The most controllable mechanism is found to be the atomic vacancy-based component in which As and Sb start on the Te sublattice. The associated diffusion coefficients of D_{400° C}=3 x10 ^-14 cm ²/s and D_{450° C}=2 x10 ^-13 cm ²/s for As and D_{350° C}= 0.9 x10 ^-14 cm ²/s, and D_{400° C}=4 x10 ^-13 cm ²/s for Sb were calculated from the experimental data. The dislocation density and its distribution were the main cause for the enhancement of As diffusion in the tailing components. The proper choice of ion implantation and anneal conditions reduced the tailing components of the diffusion profile for a given dislocation density. High performance p-on-n photodiodes at 77 K were demonstrated, using As diffusion, from implanted and grown source, into n-type In doped HgCdTe grown on GaAs/Si substrates.