GS-MBE生长的GaP/Si的XPS研究

利用X射线光电子能谱(XPS)深度剖析方法对气体源分子束外延(GS-MBE)生长的GaP/Si异质结构进行了详细的分析.其结果表明:(1)外延层内Ga、P光电子峰与GaP相相符,且组份分布均匀,为正化学比GaP.(2)在不同富PH₃流量条件下生长的样品,其表面富P量稍有不同,而GaP外延层内的测试结果相同.界面也未见有P的富集.(3)XPS剖析至GaP/Si界面附近,随外延层界面向衬底过渡,Si2p光电子峰向高结合能方向移动,且其结合能高于原衬底p型Si,接近于n型Si.但Ga、P光电子峰未发现有明显能移.(4)在XPS检测限内,外延层内和界面都未见有C、O等沾污.这一研究表明:无污染的本底超高真空、相对过剩的富₃生长环境、成功的Si衬底清洗方法等措施保证了GS-MBE生长出正化学比GaP/Si外延异质结构.

X-RAY PHOTOELECTRON SPECTROSCOPY STUDIES OF THE EPITAXIAL STRUCTURE GaP/Si GROWN BY GS MBE

In this work, the heteroepitaxial structure GaP/Si grown by Gas Source Molecular Beam Epitaxy (GS MBE) has been investigated by using X-ray Photoelectron Spectroscopy (XPS) depth profile measurements. The experimental results show that: (1) P, Ga peaks in XPS spectra within epilayer coincided with those of GaP phase. The components of P, Ga in the epilayr were distributed homogeneously correponding to GaP stoichiometry except for rich P existing in the surface, although the epitaxy proceeded in relative rich PH 3 environment. (2) There is the same quality of the samples GaP/Si grown by GS MBE under the different flowing rates of rich PH 3, and no obviously rich P has been found at the GaP/Si interface as well, except for slightly different amount of rich P existing in the surface. (3) In the vicinity of the GaP/Si interface, the peaks Si2p of the XPS spectra moved upwards to high binding energy terminal as Ar etching GaP/Si until the substrates Si, but any other XPS peaks shift had not been found. The experimental binding energy of Si2p was higher than the expected p Si substrates, approaching the binding energy of n Si. (4) The C, O and other contamination scarcely existed in epitaxial layer and its interface within XPS detectability. All the experimental results revealed that the uncontaminated background UHV (Ultra High Va cuum), relative rich PH 3 growing environment, and the successful process of cleaning Si substrate etc. were suitable for growth the stoichiometric heterostructrue GaP/Si.