Comparative study of Ga- and N-polar GaN films grown on sapphiresubstrates by molecular beam epitaxy
We report the surface, structural, and optical properties of typical Ga- and N-polar GaN films grown on sapphire substrates by molecular beam epitaxy. The Ga-polar films were grown on AlN buffer while the N-polar films were grown on GaN buffer layers. Atomic force microscopy imaging shows that the as-grown and chemically etched Ga-polar films have a flat and pitted surface while the N-polar surface is rougher with isolated columns or islands. Transmission electron microscopy demonstrates a low density of inversion domains in the Ga-polar films,while a much higher density of inversion domains was observed in the N-polar films. X-ray diffraction curves show a narrower (002) peak for Ga-polar films than that for N-polar films. On the other hand, both Ga-and N-polar films show a similar width of (104) peak. Despite their rough surfaces, high density of inversion domains, and broader (002) x-ray diffraction peaks, N-polar films with low dislocation density were demonstrated. In addition, higher PL efficiency for the N-polar films than that for the Ga-polar films was observed.
- 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-ISSA-00-0011 and In-HouseLaboratory Task 2305EW, Office of Naval Research
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 861960
- Report Number(s):
- LBNL--53093; BnR: 400403109
- Journal Information:
- Journal of Vacuum Science and Technology B, Journal Name: Journal of Vacuum Science and Technology B Journal Issue: 6 Vol. 20
- Country of Publication:
- United States
- Language:
- English
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