X-ray-scattering analysis of surface structures produced by vapor-phase epitaxy of GaAs.
X-ray-scattering analysis of surface structures produced by vapor-phase epitaxy of GaAs.
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GaAs 气相外延产生的表面结构的 X 射线散射分析。
DOI：
10.1103/physrevb.49.1957
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Brennan
中科院分区：
文献类型：
--
作者：
Lamelas;Fuoss;Kisker;Stephenson;Imperatori;Brennan
我们已经使用了原位X射线散射技术来分析表面重建和有序的步骤，在不同阶段的GaAs有机金属气相外延生长。与先前报道的c（4× 4）重建相反，我们目前的测量揭示了具有1× 2对称性的相关结构。1× 2结构是c（4× 4）重构的无序形式，其中二聚体行之间的长程相关性被保留，但二聚体空位随机定位。除了重建，有序的步骤结构进行了研究，样品与高（2.2）和低（0.07）水平的误切。使用高斯步距分布的宽度的平均阶地大小的顺序，一个数值模型是用来重现测量截断棒轮廓扫描垂直于步骤。我们还使用该模型来跟踪在生长过程中发生的步长分布的变窄。在生长了几百埃的GaAs之后，截断棒轮廓变得尖锐，并伴随着峰位的移动。这种转变是由于不同宽度的梯田散射的不对称加权：宽梯田对结构因子的贡献更大。对于具有加宽的阶跃间距分布的样品，这种效应导致比理想的误切样品将发生的更小的峰分裂。
We have used in situ x-ray-scattering techniques to analyze surface reconstructions and ordered steps at various stages in the growth of GaAs by organometallic vapor-phase epitaxy. In contrast to an earlier report of a c (4× 4) reconstruction, our current measurements reveal a related structure with 1× 2 symmetry. The 1× 2 structure is a disordered form of the c (4× 4) reconstruction in which long-range correlations between dimer rows are preserved but dimer vacancies are located at random. Aside from reconstructions, ordered step structures were studied on samples with both high (2.2) and low (0.07) levels of miscut. Using Gaussian step-spacing distributions with widths of order the mean terrace size, a numerical model is used to reproduce measured truncation rod profiles in scans perpendicular to steps. We also use the model to follow the narrowing of the step-spacing distribution which occurs during growth. After the growth of several hundred angstroms of GaAs, truncation-rod profiles sharpen, accompanied by a shift in peak positions. The shift is due to an asymmetric weighting of the scattering from terraces of different widths: wide terraces make a greater contribution to the structure factor. For samples with a broadened distribution of step spacings, this effect results in a smaller peak splitting than that which would occur for an ideally miscut sample.