Characterization of III-Nitrides on Hydrogen-Etched 6H-SiC

1. 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

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

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

4. 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

5. 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.

6. GaN on H-etched SiC (on axis)

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

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

9. GaN on H-Etched SiC- RT PL

10. GaN on H-Etched SiC- LT PL

11. GaN on H-Etched SiC- LT PL

12. 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