Experimental Evidence for Subsurface Diffusion of Nitrogen Adatoms during MBE Growth of GaN
Abstract
Great progress has been made in the fabrication of GaN light emitting devices. However, the understanding of GaN epitaxy on the atomic scale is still very limited. A recent study suggested that diffusion below the surface is an efficient channel for lateral nitrogen adatom transport during GaN MBE [1]. In this work, GaN were grown on 6H-SiC (0001) using ECR plasma-assisted MBE at 600 C under Ga-rich conditions, which resulted in Ga-polar films with the pseudo-(1x1) reconstruction. After growth termination, the surface was exposed to nitrogen-plasma at temperatures below 500 C, which resulted in the formation of three types of metastable GaN islands. By continual STM imaging, these islands can be irreversibly converted to single bilayer height islands. The conversion rate depends on both the magnitude and polarity of the bias voltage, with the positive tip bias having a more pronounced effect. The formation of the metastable islands is attributed to the incorporation of nitrogen atoms at interstitial sites under the (1x1) surface, supporting the existence of a subsurface diffusion channel for nitrogen adatoms during GaN MBE. The conversion of islands by sustained STM imaging implies an electrical field induced phase transition under which mechanism will be discussed at the meeting. [1] Neugebauer et al., PRL 90, 056101 (2003).
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARN10006K