Scanning tunneling microscopy and -spectroscopy of GaP layers on Si(001)

在硅(001)衬底上生长的磷化镓材料有望实现光电子器件与成熟的硅技术的集成。与其他III-V半导体材料相比，磷化镓的优点是与硅的晶格失配较低。然而，极性半导体在非极性衬底上的生长导致形成不同极性的磁区，这些磁区被反相界隔开。反相界是一种层错，它导致相邻原子具有相同的电子组态。因此，在磷化镓中，形成了磷或镓双键，这些键是在晶体内二维进行的带电缺陷。因此，反相界起到了非辐射复合中心的作用，从而导致了器件的效率损失。在本项目中，将使用横截面扫描隧道显微镜和光谱分析来研究反相界的结构和电子性质及其对纳米结构样品的影响。特别是，GaP/Si(001)界面应在原子尺度上成像，并研究分解或偏析效应。这些研究的目的是在物理上了解GaP/Si(001)界面的生长过程以及磷化镓层内缺陷的结构和电子性质。结果将为避免或系统地湮灭反相界以便提高所得到的GaP/Si(001)层和顶部生长的半导体结构的质量铺平道路。

Gallium phosphide based materials on silicon(001) substrates are promising for the integration of optoelectronic devices with the well-established silicon technology. The advantage of gallium phosphide compared with other III-V semiconductor materials is the low lattice mismatch to silicon. However, the growth of polar semiconductors on non-polar substrates results in the formation of domains with different polarities, which are separated by antiphase boundaries. An antiphase boundary is a stacking fault, which leads to neighboring atoms with the identical electron configuration. Thus, within gallium phosphide, phosphorous or gallium double bonds are formed, which are charged defects proceeding two-dimensionally within the crystal. Hence, the antiphase boundaries act as nonradiative recombination centers and lead to efficiency losses of the resulting devices. In the present project the structural and electronic properties of the antiphase boundaries and their influence on nano-structured samples shall be investigated using cross-sectional scanning tunneling microscopy and spectroscopy. In particular the GaP/Si(001) interface shall be imaged on the atomic scale and studied with respect to decomposition or segregation effects. The goal of those investigations is to achieve a physical understanding of the growth processes at the GaP/Si(001) interface as well as of the structural and electronical properties of defects within the gallium-phosphide layer. The results shall pave the way to avoid or to systematically annihilate the antiphase boundaries in order to increase the quality of the resulting GaP/Si(001) layer and the semiconductor structures grown on top.