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
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) (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 µm 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)
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.

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