Performance and reproducibility enhancement of HgCdTe molecular beam epitaxy growth on CdZnTe substrates using interfacial HgTe/CdTe superlattice layers

摘要

Interfacial layers including HgTe/CdTe superlattices (SLs) were introduced during the molecular-beam epitaxy growth of HgCdTe on CdZnTe (211)B substrates. Transmission-electron-microscopic observations show that the SLs smooth out the substrates' surface roughness during growth, and can also bend or block threading dislocations in a way that prevents their propagation from the substrate into the functional HgCdTe epilayers. An average etch pit density value in the low-10~5 cm~(-2) range was reproducibly achieved in long wavelength HgCdTe samples, with the best value being 4 x 10~4 cm~(-2). Photoconductive decay lifetime measurements give values approaching theoretical limits, as determined by the intrinsic radiative and Auger recombination mechanisms. The use of such interfacial layers thus leads to enhanced growth yields and material properties.