Dislocation Density Reduction in MOVPE-Grown (211) CdTe/Si by Post-Growth Patterning and Annealing

We studied the effectiveness of post-growth patterning and annealing on threading dislocation (TD) reduction in (211) CdTe/Si epilayers grown using metalorganic vapor-phase epitaxy (MOVPE). Sixty-micrometer-wide square patterns were formed on the as-grown CdTe samples using photolithography and then subjected to ex situ annealing in a flowing hydrogen environment. The annealing temperature was varied from 550°C to 800°C, then held at this temperature for a fixed duration of 5 min. The TD densities were determined using the etch pit density (EPD) technique. A comparison of EPD values revealed that the patterned samples had lower EPD values than the unpatterned samples annealed under similar conditions. This suggests that annealing promotes dislocation glide to the sidewalls of the islands and is thus more effective at dislocation removal for the patterned samples in comparison to the unpatterned samples.