Dislocation reduction in an MOVPE-grown CdTe/Si epilayer by ex-situ annealing and its effect on the performances of gamma ray detectors fabricated

Abstract

We studied ex situ thermal cycle annealing on metalorganic vapor phase epitaxy (MOVPE) grown CdTe on (211) Si substrates for dislocation density reduction and its effect on the performance of gamma-ray detector fabricated. The ex situ annealing was performed by varying temperatures from 600 °C to 1000 °C for different anneal durations and cycles varied from 1 to 7 in a hydrogen environment. Gamma-ray detector was fabricated in a p-CdTe/n-CdTe/n+-Si heterojunction diode structure. Dislocation densities were evaluated by the etch pit density (EPD) technique. Dislocation densities were decreased when the annealing temperature was increased above 800 °C. This is due to the annealing enhancing dislocations’ glide motion, which annihilate and reduce their density. The device property could be improved by subjecting the annealing during the early stage of the growth. Devices subjected to annealing showed lower dark current and improved gamma detection property when compared to the devices that were not subjected to annealing during their fabrications.