PROPERTIES OF AL2O3 OPTICAL COATINGS ON GAAS PRODUCED BY OXIDATION OF EPITAXIAL ALAS/GAAS FILMS

Auger analysis of oxidized AlAs epitaxial layers grown by molecular-beam epitaxy reveals that the composition of the films is stoichiometric Al2O3. High optical quality of the films is demonstrated by optical reflection and transmission measurements. A reflectivity of 6% is measured for an antireflection coating on GaAs. Leakage currents in the nA range and resistivities >5X10(11) OMEGA cm are deduced from current-voltage measurements. Capacitance-voltage measurements on metal-oxide-semiconductor structures using the Al2O3 films obtained by oxidizing AlAs, reveal a significant reduction of the interface state density as compared to conventional, electron beam evaporated Al2O3.