XPS measurement of GaAs–AlAs heterojunction band discontinuities: Growth sequence dependence

Abstract

We report the direct measurement, by x‐ray photoemissionspectroscopy, of the valence‐band discontinuity, ΔE v , for two types of abrupt GaAs–AlAs (110) heterojunctionsgrown by molecular beam epitaxy: (i) those formed by growth of GaAs on AlAs, and (ii) those grown in the reverse sequence, AlAs on GaAs. The ΔE v at GaAs–AlAs interfaces is, on average, 0.25 eV larger than at AlAs–GaAs interfaces. The ΔE v for GaAs–AlAs heterojunctions was found to average 0.4 eV; the corresponding ΔE v for AlAs–GaAs heterojunctions averaged 0.15 eV. The 0.25 eV difference in average ΔE v value that we observe for the two types of interface demonstrates that the energy‐band discontinuities depend on growth sequence in the GaAs–AlAs heterojunction system.