Numerical simulation of clustering phenomena for point-defects in HgCdTe

We investigated the formation of cluster defects in HgCdTe materials by numerical simulation. The equations used for the simulation include change in the activation energy for Hg vacancy diffusion dependent on the local cadmium composition. This study demonstrated how defects grow during thermal treatment. We simulated the annealing process for initial composition fluctuations in uniform n-type Hg0.78Cd0.22Te. When the local composition fluctuations increase, we found that the concentration of vacancies around the initial core increases because of the composition difference between the initial core and bulk region. Concurrently, if the fluctuation range is narrow, the resulting large constant for interstitial diffusion accelerates this process. We determined that the critical fluctuation range is in the order of 50 nm for annealing at 150°C. The concentration of clustering vacancies around the initial core reached 1016 cm−3, meaning that the conductivity of the cluster region changed to the p-type. We conclude that such cluster defects have a structure consisting of a core surrounded by a p-type shell.