Spontaneous compositional superlattice and band-gap reduction in Si-doped AlxGa1−xN epilayers
Spontaneous compositional superlattice and band-gap reduction in Si-doped AlxGa1−xN epilayers
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DOI：
10.1063/1.2126127
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发表时间：
2005-11
影响因子：
4
通讯作者：
M. Gao;Y. Lin;S. T. Bradley;S. Ringel;J. Hwang;W. Schaff;L. Brillson
中科院分区：
文献类型：
--
作者：
M. Gao;Y. Lin;S. T. Bradley;S. Ringel;J. Hwang;W. Schaff;L. Brillson
结合透射电子显微镜（TEM），X射线衍射，和阴极发光光谱测量的AlxGa 1-xN薄膜生长的分子束外延揭示自发调制，相分离，和带隙的减少，系统地改变与AlN的摩尔分数在整个合金系列。在低AlN摩尔分数（x ≤ 0.5）时，AlGaN外延层表现出明显的相分离.随着AlN摩尔分数的增加，相分离被强烈抑制自发调制的形成，高空间分辨率TEM技术明确地确定是一个原子级的组成超晶格。超晶格诱导的减少，从带隙预期的成分无序外延层超过几百毫电子伏的富铝平均合金组合物。
Combined transmission electron microscopy (TEM), x-ray diffraction, and cathodoluminescence spectroscopy measurements of AlxGa1−xN thin films grown by molecular-beam epitaxy reveal spontaneous modulation, phase separation, and band-gap reductions that vary systematically with AlN mole fraction across the full alloy series. At low AlN mole fraction (x⩽0.5), AlGaN epilayers display pronounced phase separation. With increasing AlN mole fraction, phase separation is strongly suppressed by the formation of spontaneous modulation, which high spatial resolution TEM techniques unambiguously determine to be an atomic-scale compositional superlattice. Superlattice-induced reductions from band gaps expected for compositionally disordered epilayers exceed several hundred meV for the Al-rich average alloy composition.