Interface electronic transition observed by optical second-harmonic spectroscopy in β-GaN/GaAs(001) heterostructures

Optical second-harmonic spectroscopy was used to probe the interface electronic structure of highly mismatched beta-GaN/GaAs(001) heterostructures in the vicinity of the E-0 interband critical point of beta-GaN. The resonance energy of both bulk and interface two-photon E-0 transitions from layers between 1- and 100-nm thickness are identical, indicating the absence of appreciable amounts of strain and electric fields in this materials system. This finding is in striking contrast to observations made for other materials systems, including ZnSe/GaAs and SiO2/Si, where large shifts of several 10 meV with respect to the bulk values have been found. [S0163-1829(98)06804-0].