MBE HgCdTe for infrared focal plane arrays

The recent progress in MBE growth of HgCdTe at the Epitaxy Research Center for Advanced Materials, and the National Laboratory for Infrared Physics is described. It was found that the surface morphology is sensitive to the growth temperature and the flux ratio. The compositional reproducibility studied in a limited number of samples showed that a STDDEV for x-values of 0.0017 deviated from an average value of 0.229 was obtained. The epilayers showed excellent compositional uniformity across 2-inch wafers, the relative deviations for x-value and thickness were found to be 0.18% and 2.19%, respectively. Ellipsometer was used for real-time monitoring the compositional variations during growth. The post growth annealing process was found to be effective in reducing the dislocation density, a reduction in dislocation density by ∼50% could be obtained even by ∼250°C low temperature annealing. Electrical properties of epilayers are described, and a p-type in situ vacuum annealing process was demonstrated. MBE grown p-HgCdTe epilayers were successfully incorporated into 32×32 focal plane arrays detectors.