Al掺杂4H-SiC同质外延的缓冲层

The Buffer Layer of Al-doped 4H-SiC

利用扫描电子显微镜(SEM)、X射线双晶衍射谱(XRD)和光致发光谱(PL)对在4H-SiC单晶衬底上采用CVD同质外延的4H-SiC单晶薄膜的特性进行研究,发现外延层有很好的晶格结构和完整性。由于Al原位掺杂引起的晶格失配和衬底和外延的晶向偏离,在样品的衬底和外延的界面出现了约1μm的缓冲层,使得XRD摇摆曲线距主峰左侧约41arcs出现了强衍射峰。缓冲层中存在大量的堆垛缺陷和位错,引入缺陷能级,使室温PL测试为"绿带"发光。通过PL全片扫描发现缓冲层在整个样品中普遍存在且分布均匀。

Properties of Al-doped 4H-SiC epitaxial layer, grown by CVD on the 4H-SiC were studied using scanning electron microscope （SEM）, X-ray diffraction （XRD） and photoluminescence （PL）. The results indicate that the 4H-SiC epitaxial layer has a good crystalline structure. The buffer layer at the interface of n-type substrate and p-type epitaxial layer is found by SEM caused by lattice mismatch and lattice misorientation, hence two well-shaped peaks in dou- ble-axis rocking curve are found. The room temperature photoluminescence measurements show the green band is attributed to the DAP-type transitions from the shallow accepter （Al） to the deep donor caused by defect energy. Finally, the room temperature PI. mapping results illustrate that the defect energy is uniform distribution in the epitaxial layer.