Investigation of defects and surface polarity in GaN using hot wetetching together with microscopy and diffraction techniques
The availability of reliable and quick methods to determine defect density and polarity in GaN films is of great interest.Photoelectrochemical (PEC) and hot wet etching using both H3PO4 and molten KOH have been used to estimate the defect density in GaN by producing at the surface defect sites free standing whiskers and hexagonal pits, respectively. Using Atomic Force Microscopy (AFM), we found the whisker density to be similar to etch pit density for samples etched under precise conditions. Additionally, Transmission electron microscopy (TEM) analysis confirmed dislocation densities obtained by etching which increased our confidence in the consistency of methods used. Hot wet etching was used also to investigate the polarity of GaN films together with Convergent beam electron diffraction (CBED) and AFM imaging. We found that hot H3PO4 etches N-polar GaN films very quickly resulting in the complete removal or drastic change of surface morphology. On the contrary, the acid attacks only defect sites in Ga-polar films producing pits but leaving the defect-free GaN intact and the morphology unchanged. Additionally,the polarity assignments were related to the as-grown morphology and to the growth conditions. We have found that the GaN films grown on high temperature AlN and GaN buffer layers on sapphire by molecular beam epitaxy (MBE) show Ga and N-polarity, respectively. However, the polarity of GaN films grown on low temperature AlN or GaN buffer layers depends critically on the growth conditions.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE; National Science Foundation, Department of Defense.Air Force Office of Scientific Research AFOSR-M50017
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 861963
- Report Number(s):
- LBNL--53101; BnR: 400403109
- Journal Information:
- Materials Science & Engineering, Journal Name: Materials Science & Engineering Vol. B93
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMIC FORCE MICROSCOPY
AVAILABILITY
Atomic force microscopy Transmission electron microscopyMolecular beam epitaxy
BUFFERS
DEFECTS
DIFFRACTION
DISLOCATIONS
ELECTRON DIFFRACTION
ETCHING
MICROSCOPY
MOLECULAR BEAM EPITAXY
MORPHOLOGY
REMOVAL
SAPPHIRE
TRANSMISSION ELECTRON MICROSCOPY