Characterization of III-Nitrides on Hydrogen-Etched 6H-SiC Z.J. Reitmeier, E.A. Preble, R.F. Davis North Carolina State University Department of Materials Science and Engineering Brian Skromme Arizona State University Department of Electrical Engineering February 12, 2002

Outline Review of motivation for hydrogen etching Results from literature Comparison of GaN on H-Etched vs. as-received SiC HRXRD PL Other techniques

Review- Motives for H-Etching Cross Section GaN SiC 5m X 5m AFM of as-received wafer Stacking Mismatch Boundary* Eliminate polishing scratches Produce unit cell height steps Minimize stacking mismatch boundaries in III-Nitride films Plan View A A A A B B B B A C A C A C A C C C B B B B A A C A C A C C B B B B A C A C A C A C C C B B B B * Image taken from: Torres et al. Applied Phys. Lett., 74 (7) 985-987 (1999)

Surfaces of H-Etched SiC Substrates Etching conditions: Temperature = 1600ºC 75%H2/25%He Flow Time at temp.= 20 min. System pressure = 1atm Results in: Steps 15A high (1 unit cell) Terraces 0.2-0.7µm wide

Results from Literature Z.Y. Xie et. al., MRS Internet J. Nitride Semicond. Res. 4S1, G3.39 (1999). MOCVD GaN Slightly lower (0001) x-ray FWHM for GaN on etched SiC. R. Lantier et. al. MRS Internet J. Nitride Semicond. Res. 4S1, G3.50 (1999). MBE GaN Lowest (002) GaN x-ray FWHM for etched SiC. HR-TEM revealed identical dislocation populations. Identical PL spectra.

GaN on H-etched SiC (on axis) This plot of GaN FWHM vs. SiC FWHM on hydrogen etched and as-received SiC shows that the GaN is actually worse on etched material than on as-received material.

GaN & AlN on H-Etched SiC- On-Axis HRXRD

GaN & AlN on H-Etched SiC- On-Axis HRXRD

GaN on H-Etched SiC- RT PL

GaN on H-Etched SiC- LT PL

GaN on H-Etched SiC- LT PL

Summary H-etching SiC substrates does not reduce the on- or off-axis X-ray FWHM of GaN H-etching SiC substrates increases the on-axis X-ray FWHM of AlN GaN on H-etched SiC has less un-relaxed compressive strain