Polarized photoreflectance spectroscopy of strained A-plane GaN films on R-plane sapphire
Polarized photoreflectance spectroscopy of strained A-plane GaN films on R-plane sapphire
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DOI：
10.1063/1.1968424
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发表时间：
2005-07
影响因子：
3.2
通讯作者：
Sandip Ghosh;P. Misra;H. Grahn;Bilge İmer;S. Nakamura;S. Denbaars;J. Speck
中科院分区：
文献类型：
--
作者：
Sandip Ghosh;P. Misra;H. Grahn;Bilge İmer;S. Nakamura;S. Denbaars;J. Speck
利用偏振光反射（PR）光谱研究了R面蓝宝石衬底上的[112 <$0]取向的A面GaN薄膜，其中GaN的c轴位于薄膜平面内。在GaN的基本能隙附近，具有垂直于c轴偏振的探测光的PR光谱表现出对应于标记为T1的单个跃迁的一个特征。对于平行于c轴的极化，在比跃迁T1更高的能量处观察到标记为T2和T3的两个不同特征。为了解释这三个功能的起源，我们比较测量的能量与计算的过渡能量和振子强度的三个带-带跃迁的GaN附近的基本间隙的各向异性面内应变在A平面。分析表明，所观察到的过渡能量和偏振特性的三个过渡可以解释的存在下，一个整体的压缩，各向异性的面内应变的膜。
We have investigated a [112¯0]-oriented A-plane GaN film on R-plane sapphire, where the c axis of GaN lies in the film plane, by polarized photoreflectance (PR) spectroscopy. Near the fundamental energy gap of GaN, the PR spectrum with the probe light polarized perpendicular to the c axis exhibits one feature corresponding to a single transition labeled T1. For a polarization parallel to c axis, two different features labeled T2 and T3 are observed at higher energies than the transition T1. In order to explain the origin of these three features, we compare the measured energies with calculations of the transition energies and oscillator strengths of the three band-to-band transitions of GaN near its fundamental gap for an anisotropic in-plane strain in the A plane. The analysis shows that the observed transition energies and polarization properties of the three transitions can be explained by the presence of an overall compressive, anisotropic in-plane strain in the film.