Three-wave-mixing spectroscopy of ZnSe/GaAs(001) heterointerfaces

Three-wave-mixing spectroscopy was used to probe the interfacial electronic structure of ZnSe/GaAs(001) heterojunctions. The interface spectra exhibit two sharp features at 2.92 and 2.72 eV. The former resonance was assigned to the E₁ transition of buried GaAs. This assignment was consistent with thickness-dependent measurements of the resonance intensity. The strong interfacial feature at 2.72 eV resulted from a virtual crossover transition connecting a resonance state of the interfacial quantum well to the ZnSe valence band. The interfacial quantum well was produced by band bending near the junction. Photomodulation second-harmonic measurements corroborate the assignment of the 2.72 eV resonance. A quantitative microscopic calculation of the relevant matrix elements suggests that the strong interfacial resonance at 2.72 eV is probably the result of a two-level nonlinear process involving only the quantum well resonance state and the ZnSe valence band. Finally we demonstrate that the interfacial deformation potential could not be responsible for the generation of the interfacial resonance.