Study of semiconductor heterointerface using low-energy electron transmission spectroscopy

用低能电子衍射（LEED）、俄歇电子能谱（AES）和低能电子透射谱（LEETS）研究了Ge在Si及其异质界面上生长的初始阶段，对于Si（001）表面Ge的生长，LEED和AES测量表明，直到覆盖度为5 ML时，Ge的生长是以假晶的逐层方式进行的。超过5 ML的覆盖范围，具有{015}面的小3D簇外延生长，保持衬底取向。当在Si（111）表面上用As表面活性剂生长时，Ge的生长以假晶的逐层方式进行，直到覆盖率达到8 ML。Ge的进一步沉积导致晶格失配的弛豫和具有与体Ge相同的晶格常数的Ge膜的生长。相比之下，没有作为表面活性剂的Ge生长在Stranski-Krastanov模式中进行。LEED测量表明，Ge岛的晶格常数比体Ge小1.5%。我们认为，所产生的岛是Si和Ge的合金，因为生长温度很高（500 ℃），生长速度很慢（0.07ML/min）。我们对生长在Si（001）和Si（111）表面上的Ge薄膜进行了LEET测量。对于Si（111）衬底上生长的Ge，LEET谱显示出特征的量子尺寸特征，表明Ge/Si界面突变。相比之下，当在600 ℃下使用As表面活性剂不仅在Si（001）上生长而且在Si（111）上生长时，没有观察到LEET光谱的量子特征。这些结果表明，LEETS提供了半导体异质界面结构的信息。

Initial stages of Ge growth on Si and its heterointerface have been investigated using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and low-energy electron transmission spectroscopy (LEETS).For Ge growth on Si(001) surface, LEED and AES measurements reveal that up to a coverage of 5ML, Ge growth proceeds in the pseudomorphic layer-by-layer fashion. Beyond a coverage of 5ML, small 3D clusters with {015} facets grow epitaxially keeping the substrate orientation. Moreover, energy dependence of the LEED spot profiles reveals that the lattice distortion still remains in this phase consisting of small 3D clusters.When growing on Si(111) surface with an As surfactant, up to a coverage of 8ML, Ge growth proceeds in the pseudomorphic layer-by-layer fashion. Further deposition of Ge leads to the relaxation of lattice misfit and growth of Ge films having the same lattice constant as bulk Ge. In contrast, Ge growth without the As surfactant proceeds in the Stranski-Krastanov mode. LEED measurements reveal that Ge islands have the smaller lattice constant by 1.5% than that of bulk Ge. We believe that the resulting island is an alloy of Si and Ge, since growth temperature is high (500ﾟC) and growth rate is very slow (0.07ML/min). Based on the results, we speculate that the As surfactant prevents the alloying of growing films.LEET measurements have been employed for Ge films grown on both Si(001) and Si(111) surfaces. For Ge growth on Si(111) at 500ﾟC with the As surfactant, LEET spectra exhibit characteristic quantum size features, suggesting the abrupt Ge/Si interface. In contrast, when growing not only on Si(001) but on Si(111) at 600ﾟC with the As surfactant, no quantum feature characteristic of LEET spectra was observed. These results indicate that LEETS provides information on the structure of semiconductor heterointerfaces.