畸变纤锌矿晶胞：非极性a面AlGaN晶格参数的测定和固相Al含量的估算
Distorted wurtzite unit cells: Determination of lattice parameters of non-polar a-plane AlGaN and estimation of solid phase Al content
摘要：
与c面氮化物不同，由于晶格的各向异性和与衬底或缓冲层的热失配，在例如a面或m面取向上生长的“非极性”氮化物遇到各向异性面内应变。这种各向异性应变导致纤锌矿晶胞的畸变，并在三元合金中精确测定晶格参数和固相III族含量（x_solid）方面产生困难。在本文中，我们表明，晶格畸变是正交的，并概述了一个相对简单的程序，从高分辨率的X射线衍射测量的非极性III族氮化物外延层的晶格参数的测量。我们推导出一个近似表达式的x_solid考虑到各向异性应变。我们说明了这一点，使用a-平面AlGaN的数据，在那里我们测量的晶格参数和估计的固相Al含量，也表明这种方法是适用于m-平面结构。
英文摘要：
Unlike c-plane nitrides, ``non-polar" nitrides grown in e.g. the a-plane or m-plane orientation encounter anisotropic in-plane strain due to the anisotropy in the lattice and thermal mismatch with the substrate or buffer layer. Such anisotropic strain results in a distortion of the wurtzite unit cell and creates difficulty in accurate determination of lattice parameters and solid phase group-III content (x_solid) in ternary alloys. In this paper we show that the lattice distortion is orthorhombic, and outline a relatively simple procedure for measurement of lattice parameters of non-polar group III-nitrides epilayers from high resolution x-ray diffraction measurements. We derive an approximate expression for x_solid taking into account the anisotropic strain. We illustrate this using data for a-plane AlGaN, where we measure the lattice parameters and estimate the solid phase Al content, and also show that this method is applicable for m-plane structures as well.
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