外延GaN基薄膜表面应变演变RHEED分析

介绍了反射式高能电子衍射仪(RHEED)衍射原理以及半导体薄膜表面原子间距与其衍射图像间距成反比例关系。分析了采用ECR-PEMOCVD生长技术,在α-Al2O3衬底上低温外延GaN基薄膜(氮化层、缓冲层、外延层)工艺过程。通过对RHEED图像分析软件获取不同工艺过程中的外延薄膜衍射条纹间距的数据分析、计算、比较,得到薄膜表面衍射图像间距的大小,依据RHEED衍射图像与原子面间距之间的对应关系,分析薄膜表面的应变状态演变情况。分析计算结果表明生长20min氮化层、20min缓冲层的表面原子层处于压应变状态,而生长180min的AlN外延层,表面则处于完全弛豫状态。

Analysis of Surface Transformation State of Epitaxial GaN-Based Films by Using RHEED

The principle of reflect high energy electron diffraction(RHEED)and the inverse proportion relationship between the surface atomic distance of semiconductor films and the images of RHEED were introduced.GaN-based epitaxial films(nitrided layer,buffer layer,epitaxial layer)were grown on α-Al2O3 substrates at low temperature by ECR-PEMOCVD,and the whole process was analyzed.Distribution data of surface diffraction patterns of epitaxial films in the different processes by a RHEED analysis software were given,analyzed,calculated and compared to get the distances of surface diffraction patterns.Based on the corresponding relations between the images of RHEED and the distances of atomic surfaces,the surface state transformations of epitaxial films were analyzed.The results indicate that the surface atomic layers of the AlN layer grown by 20 min and the GaN buffer layer grown by 20 min are in the compressive strain state,while the surface of the AlN epitaxial layer grown by 180 min is in a completely relaxation state.