CHARGED VERSUS NEUTRAL INTERFACES IN III-V GE QUANTUM-WELLS/

We discriminate between the charged and neutral character of Ge/III-V semiconductor interfaces by examining the band discontinuities across each interface in AlAs-Ge-GaAs(001) and GaAs-Ge-AlAs(001) single quant um well structures as a function of Ge thickness in the 2-16 monolayer range and comparing them with those of individual, isolated Ge-GaAs(0 01), Ge-AlAs(001), GaAs-Ge(001) and AlAs-Ge(001) heterojunctions. All structures were grown by molecular beam epitaxy at 360-degrees-C and e xamined in situ by X-ray photoemission spectroscopy. While ideally abr upt polar heterovalent interfaces are predicted to be charged, we find that all of the observed deviations from the commutativity and transi tivity rules of heterojunction band offsets are consistent with the es tablishment of inequivalent, neutral IV/III-V and III-V/IV interfaces.