Dislocation reduction in CdTe/Si by molecular beam epitaxy through in-situ annealing

The relatively high dislocation density of HgCdTe material grown on CdTe/Si by MBE has become a major roadblock toward achieving high operability of LWIR HgCdTe/Si FPAs. One approach to mitigate this problem is to reduce the dislocation density of the underlying CdTe/Si composite substrate, which is currently about two orders higher than that of bulk CdZnTe. In this paper, we will report on our systematic study of in-situ cyclic annealing of CdTe/Si and its impact on dislocation density. We observed a two orders of magnitude reduction of dislocation density on in-situ annealed CdTe/Si with respect to un-annealed CdTe/Si. The degree of reduction is proportional to the number of annealing cycles applied during the growth run. Depth profiling of the dislocation density of CdTe/Si layers with and without in-situ cyclic annealing has also been investigated. We do not observe the conventional 1/h behavior of the dislocation density for layers grown without any thermal treatment. In contrast, for the layer grown with in-situ cyclic annealing, we observe an exponential decay of dislocation density as a function of layer thickness. However, we also observe a saturation of dislocation density in low to mid 105 cm−2, regardless of the annealing temperature and number of the cycles used during annealing.