Annealing of MBE-grown CdTe epitaxial layer at various tellurium overpressure for reduced defect density
摘要
Cadmium telluride (CdTe) (211) epitaxial layers were grown on GaAs (211) substrates. These CdTe layers were annealed under tellurium overpressure at different annealing temperatures to optimize conditions for better crystal quality and surface roughness. Tellurium overpressure was calculated using thermodynamical equations and utilized during the growth of the CdTe epitaxial layer by MBE. It was found that crystal quality improved, which manifested in the reduction of XRD peak full width at half maximum (FWHM) from ~ 150 to ~ 70 arcsec, and observation of fivefold reduction in dislocation defect density. Annealing conditions were optimized with a tradeoff between crystal quality and surface roughness. The activation energy of β-dislocations in CdTe epitaxial layers was determined to be Ea = 1.05 ± 0.2 eV. HRXRD FWHM ~ 55 arcsec was obtained for 10-μm thick CdTe buffer layer. The large area (3 in. dia) high crystal quality (HRXRD FWHM ~ 70 arcsec) HgCdTe epitaxial layers were grown on CdTe/ GaAs substrates.