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.
| Original language | English |
|---|---|
| Article number | 123519 |
| Journal | Journal of Applied Physics |
| Volume | 106 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 2009 Dec 1 |
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All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
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Morphological and microstructural evolution in the two-step growth of nonpolar a -plane GaN on r -plane sapphire. / Sun, Qian; Kong, Bo Hyun; Yerino, Christopher D.; Ko, Tsung-Shine; Leung, Benjamin; Cho, Hyung Koun; Han, Jung.
In: Journal of Applied Physics, Vol. 106, No. 12, 123519, 01.12.2009.Research output: Contribution to journal › Article
TY - JOUR
T1 - Morphological and microstructural evolution in the two-step growth of nonpolar a -plane GaN on r -plane sapphire
AU - Sun, Qian
AU - Kong, Bo Hyun
AU - Yerino, Christopher D.
AU - Ko, Tsung-Shine
AU - Leung, Benjamin
AU - Cho, Hyung Koun
AU - Han, Jung
PY - 2009/12/1
Y1 - 2009/12/1
N2 - 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.
AB - 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.
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U2 - 10.1063/1.3272790
DO - 10.1063/1.3272790
M3 - Article
AN - SCOPUS:73849095031
VL - 106
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 12
M1 - 123519
ER -