INVESTIGATION OF ALUMINUM NITRIDE GROWN BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION ON SILICON

Undoped single crystalline aluminum nitride films were grown on 4H and 6H SiC substrates using metal-organic chemical-vapor deposition at 12 00 degrees C, From in situ reflection high-energy electron diffraction , x-ray diffraction rocking curves, and cathodoluminescence spectra, t he crystallinity of the films was confirmed. Atomic force microscopy s howed that some films were substantially dominated by island growth, r ather than step flow growth. Aluminum was evaporated to form metal-ins ulator-semiconductor (MIS) capacitors for high-frequency capacitance v oltage measurements carried out at room temperature. Low leakage made it possible to measure the structures and characterize accumulation, d epletion, deep depletion, and, in some cases, inversion. From independ ent optical thickness measurements, the relative dielectric constant o f aluminum nitride was confirmed at 8.4. The flatband voltage of the A lN MIS capacitors on p-type SiC was close to the theoretical value exp ected. The films were stressed up to 60 V (3 MV/cm) without breakdown, but excessive leakage currents (>0.1 A/cm(2)), probably dominated by grain-boundary conduction, shifted the flatband voltage of the capacit ors. These results indicate the possibility of replacing silicon dioxi de with aluminum nitride in SiC field effect transistors using insulat ed gates. (C) 1997 American Institute of Physics.