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The valence- and conduction-band discontinuities have been determined for the InAs–GaAs (100) heterojunction (HJ) by means of XPS measurements. The values are ΔEv = 0.17±0.07 eV and ΔEc = 0.90±0.07 eV, respectively. The InAs-GaAs HJ has a rather large lattice mismatch (7%) but high quality epitaxial heterojunctions may be grown by molecular beam epitaxy (MBE). We have carried out XPS measurements on MBE grown InAs (100) films and on the InAs-GaAs (100) HJ by using a recently developed arsenic cap transfer technique which permits XPS measurements on atomically clean and ordered heterojunctions. XPS is used to obtain the In4d and As3d to valence-band maximum binding-energy differences for bulk InAs by fitting the experimental XPS valence-band density of states (VBDOS) to an instrumentally broadened theoretical VBDOS. The values are (EInAsIn4d−EInAsv) = 17.43 ±0.02 eV and (EInAsAs3d−EInAsv) = 40.77±0.02 eV, respectively. The core-level separation ΔECL between the In4d and Ga3d core levels for a thin InAs–GaAs (100) HJ is experimentally determined to be 1.55±0.06 eV.
Kowalczyk et al. (1982) studied this question.