BAND OFFSETS AND STRAIN IN CDTE-GAAS HETEROSTRUCTURES

CdTe(111)-GaAs(001) and CdTe(001)-GaAs(001) heterostructures were synt hesized through molecular-beam epitaxy. In situ monochromatic x-ray ph otoemission spectroscopy and reflection high-energy electron diffracti on, together with ex situ cross-sectional transmission electron micros copy, were exploited to probe the relation between overlayer orientati on, residual strain, and the band discontinuities. CdTe(001)-GaAs(001) heterostructures appear fully relaxed even at the lowest overlayer th icknesses explored through the formation of a misfit dislocation netwo rk. Correspondingly, the valence-band maximum in the CdTe(001) overlay er is found 0.07-0.09 eV below that of GaAs(001). In CdTe(111)-GaAs(00 1) heterostructures, we find that residual strains are gradually accom modated within a 200-angstrom-thick CdTe layer near the interface. The average position of the valence-band maximum in CdTe(111) is 0.09-0.1 1 eV above that of GaAs(001) at the interface. The difference in valen ce-band discontinuity for the two interfaces is qualitatively consiste nt with that expected from the effect of the residual strain on the va lence-band maximum of CdTe(111).