The valence-band discontinuity (ΔEv) at heterojunctions formed by growing GaAs epitaxially on Ge(110) substrates has been studied by using x-ray photoelectron spectroscopy. The GaAs grown on Ge (110) interface is observed to exhibit a time dependent variation in ΔEv that is as much as ∼0.2 eV. For GaAs/Ge(110) heterojunctions grown at 350 °C and kept at room temperature for >100 h, ΔEv∼0.3 eV; this is ∼0.25 eV less than the ΔEv measured for the stable interface formed by growing Ge epitaxially on GaAs (110). It is observed that ΔEv for growth of a lattice matched compound semiconductor (AB) on Ge(110) is substantially smaller than for the reverse growth sequence, i.e., ΔEv [AB/Ge(110)]<ΔEv[Ge/AB(110)]. A possible mechanism for this growth sequence effect which involves antiphase disorder at AB/Ge(110) interfaces is suggested.
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Grant et al. (1985) studied this question.