OXIDE-GAAS INTERFACIAL ELECTRONIC-PROPERTIES CHARACTERIZED BY MODULATION SPECTROSCOPY OF PHOTOREFLECTANCE

Built-in electric fields and interfacial state densities (D-it) in a s eries of oxide-GaAs heterostructures fabricated by in situ molecular b eam epitaxy were studied using room temperature photoreflectance. The samples investigated were air-, Al2O3-Ga2Ox-, and Ga2O3(Gd2O3)-GaAs, W e found that the built-in electric fields are 48, 44, and 38 kV/cm for air-, Al2O3-, and Ga2Ox-GaAs samples, respectively. For the Ga2O3(Gd2 O3)-GaAs sample, the built-in electric field is negligibly small, indi cating a very low interfacial state density. Estimated by the low fiel d limit criterion, D-it is less than 1 x 10(11) cm(-2) eV(-1). Our res ults on the Ga2O3(Gd2O3)-GaAs sample are consistent with the data obta ined previously using capacitance-voltage measurements in quasistatic/ high frequency modes and photoluminescence measurements. (C) 1998 Amer ican Institute of Physics.