ZHEN Hui-hui, LU Lin, LIU Zi-chao, SHANG Lin, XU Bing-she. Correlation Between The Morphology of Threading Dislocations and The Origin of High-resistivity GaN[J]. Chinese Journal of Luminescence, 2013,34(12): 1607-1612
ZHEN Hui-hui, LU Lin, LIU Zi-chao, SHANG Lin, XU Bing-she. Correlation Between The Morphology of Threading Dislocations and The Origin of High-resistivity GaN[J]. Chinese Journal of Luminescence, 2013,34(12): 1607-1612 DOI: 10.3788/fgxb20133412.1607.
Correlation Between The Morphology of Threading Dislocations and The Origin of High-resistivity GaN
The high-resistivity (HR) GaN is the basis of GaN-based electronic devices. The HR-GaN films were grown by metal organic chemical vapor deposition (MOCVD) on
c
-plane sapphire substrates
using trimethyl gallium (TMGa) and NH
3
as precursors and high purity H
2
as carrier gas. GaN samples with different resistivity were prepared at various annealing pressures between 10 000 Pa and 54 200 Pa. Surface morphology
dislocation density of different resistivity of the GaN films were characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). The resistance of GaN increases rapidly with the annealing pressure reducing. The high-quality GaN epitaxial films have been achieved by the experimental method. With the annealing pressure reducing
the edge dislocation density significantly increases by several times
and the screw dislocation density changes. The correlation between the morphology of threading dislocations (TDs) and the origin of HR GaN films was investigated using transmission electron microscopy. It is observed that the morphology of TDs can lead to different resistivity in GaN film
and the edge-type TDs are more sensitive to the sheet resistivity than the screw-type TDs. The sheet resistivity increases by seven orders of magnitude with the increase in the edge-type TDs. The morphology of TDs determines the movement of the negative charges which leads to different resistivity of the GaN film. The TDs can work as the electronic conduction channels. In the low-resistivity GaN
almost all TDs are bent and interactive
and the electrons also move along with the channels formed by the bent TDs. In the HR-GaN
TDs are all straight and perpendicular to the sapphire
and the electrons are difficult to move in the lateral direction.
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references
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