A novel technique for the MBE growth of twin-free HgCdTe

Abstract

A novel photon-assisted MBE technique, compositionally modulated structures (CMSs), has been developed to suppress twinning in MBE HgCdTe growth. Strain effects, introduced by thin CdTe layers, suppress planar twinning as well as lowering dislocation densities. A CMS epilayer consists of multiple repeats of a basic unit comprised of a thick (500–1500 Å) layer of HgCdTe and a thin (20–50 Å) layer of CdTe. The CMS epilayer is then interdiffused in a sealed quartz ampoule at temperatures consistent with n-type (or p-type) annealing producing isotropic HgCdTe suitable for infrared detector array fabrication. CMS has also been successfully applied to the low defect density growth of HgCdTe on the slightly lattice-mismatched CdTe substrates. This is an important result because CdTe substrates are less expensive, more chemically pure, and more readily available than the lattice-matched substrate CdZnTe.