INTERFACE ELECTRONIC-TRANSITION OBSERVED BY OPTICAL 2ND-HARMONIC SPECTROSCOPY IN BETA-GAN GAAS(001) HETEROSTRUCTURES/

Optical second-harmonic spectroscopy was used to probe the interface e lectronic structure of highly mismatched beta-GaN/GaAs(001) heterostru ctures 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 trans itions from layers between 1- and 100-nm thickness are identical, indi cating the absence of appreciable amounts of strain and electric field s in this materials system. This finding is in striking contrast to ob servations made for other materials systems, including ZnSe/GaAs and S iO2/Si, where large shifts of several 10 meV with respect to the bulk values have been found. [S0163-1829(98)06804-0].