Effect of growth sequence on the band discontinuities at AlAs/GaAs (100) and (110) heterojunction interfaces

The valence band discontinuity ΔEv for the AlAs grown on GaAs (AlAs–GaAs) heterojunction interface is compared to the corresponding ΔEv for the GaAs grown on AlAs interface (GaAs–AlAs) for both (100) and (110) crystallographic orientations by using x‐ray photoemission spectroscopy (XPS). Molecular‐beam epitaxy within the XPS system was used to prepare the samples. The XPS method has the feature that ΔEv differences are measured more accurately than the corresponding absolute magnitudes. For the (100) interface, the value of ΔEv(AlAs–GaAs) is 0.10±0.02 eV larger than ΔEv(GaAs–AlAs). For the (110) interface, ΔEv(AlAs–GaAs) is 0.13±0.04 eV larger than ΔEv(GaAs–AlAs). The average discontinuity magnitudes are: ΔEv(AlAs–GaAs)(100)=0.46 eV; ΔEv(GaAs–AlAs)(100)=0.36 eV; ΔEv(AlAs–GaAs)(110)=0.55 eV; and ΔEv(GaAs–AlAs)(110)=0.42 eV. Thus, both a growth sequence effect and an orientation dependence have been found to be intrinsic characteristics of the (100) and (110) AlAs/GaAs heterojunction interfaces. As a conseq...