Anisotropic strain relaxation and the resulting degree of polarization by one- and two-step growth in nonpolar a -plane GaN grown on r -sapphire substrate

Anisotropic strain relaxation and the resulting degree of polarization of the electronic transition in nonpolar a-plane GaN using one- and two-step growth are studied. By using two-step growth, a slower coalescence and a longer roughening-recovery process lead to larger anisotropic strain relaxation...

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Bibliographic Details
Published in:Journal of applied physics 2013-12, Vol.114 (23)
Main Authors: Feng, Shih-Wei, Chen, Yu-Yu, Lai, Chih-Ming, Tu, Li-Wei, Han, Jung
Format: Article
Language:English
Subjects:
ANISOTROPY
Applied physics
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Coalescing
GALLIUM NITRIDES
Indium gallium nitrides
Light emitting diodes
MATERIALS RECOVERY
OSCILLATOR STRENGTHS
Perturbation
PERTURBATION THEORY
Plane strain
POLARIZATION
Polarized light
Recovery
RELAXATION
Roughening
SAPPHIRE
STACKING FAULTS
Strain relaxation
STRAINS
Striations
SUBSTRATES
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Summary:Anisotropic strain relaxation and the resulting degree of polarization of the electronic transition in nonpolar a-plane GaN using one- and two-step growth are studied. By using two-step growth, a slower coalescence and a longer roughening-recovery process lead to larger anisotropic strain relaxation, a less striated surface, and lower densities of basal stacking fault (BSF) and prismatic stacking fault (PSF). It is suggested that anisotropic in-plane strains, surface striation, and BSF and PSF densities in nonpolar a-GaN are consequences of the rate of coalescence, the period of roughening-recovery process, and the degree of anisotropic strain relaxation. In addition, the two-step growth mode can enhance the degree of polarization of the electronic transition. The simulation results of the k⋅p perturbation approach show that the oscillator strength and degree of polarization of the electronic transition strongly depend on the in-plane strains upon anisotropic in-plane strain relaxation. The research results provide important information for optimized growth of nonpolar III-nitrides. By using two-step growth and by fabricating the devices on the high-quality nonpolar free-standing GaN substrates, high-efficiency nonpolar a-plane InGaN LEDs can be realized. Nonpolar a-plane InGaN/GaN LEDs can exhibit a strongly polarized light to improve the contrast, glare, eye discomfort and eye strain, and efficiency in display application.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4851755