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Morphological and microstructural evolution in the two-step growth of nonpolar a-plane GaN on r-plane sapphire

Authors :
Hyung Koun Cho
Tsung-Shine Ko
Christopher D. Yerino
Benjamin Leung
Jung Han
Qian Sun
Bo Hyun Kong
Source :
Journal of Applied Physics. 106:123519
Publication Year :
2009
Publisher :
AIP Publishing, 2009.

Abstract

In this paper, we report a detailed study on the evolution of surface morphology and microstructure of nonpolar a-plane GaN (a-GaN) through controlled growth interruptions. Microscopy imaging shows that the two-step a-GaN growth went through a roughening-recovery process. The first-step growth (under high V/III and high pressure) produced a rough surface with tall mesas separated by voids. The second-step growth (under low V/III and low pressure) promoted the lateral growth and filled up the voids. Striations that formed during the island coalescence persisted throughout the second-step growth, but could be relieved by an additional third-step growth. The morphological evolution was explained according to the kinetic Wulff plots. The microstructure of the a-GaN films was investigated by transmission electron microscopy (TEM) and x-ray rocking curve analysis. Most of the extended defects observed in the plan-view TEM images were I1 type basal-plane stacking faults (BSFs) and their associated partial dislocations (PDs). It is found that the bending of PDs (at the inclined/vertical growth fronts) within the basal plane toward the m-axes was responsible for the substantial reduction in threading PDs and the increase in BSF dimension. Based on a careful correlation between the morphological evolution and the microstructure development, we proposed a model explaining the possible mechanisms for the great reduction in defect density during the two-step growth process.

Details

ISSN :
10897550 and 00218979
Volume :
106
Database :
OpenAIRE
Journal :
Journal of Applied Physics
Accession number :
edsair.doi...........4cf6847f4d96a843e372d6c85d4e3aaa
Full Text :
https://doi.org/10.1063/1.3272790