Preparation and properties of Hetero-junctions between PtSi or p-Si and p-Si/Ge strained superlattice

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PtSi layrs were found to be grown epitaxially on Si (111) surface more perfectly than on Si (001) surface by co-evaporation of Pt and Si in a MBE system. When the substrate temperature was 400ﾟC or below, Si was epitaxially grown on PtSi layr and Si/PtSi/Si double-hetero structure was obtained. However, PtSi and Si reacted and made columnar structures when the substrate temperature of Si growth was 600ﾟC or above.In order to make an abrupt interface in a p-Si/Ge/Si strained super lattice, Boron (B) was investigated as a p-type surfactant. HBO_2 was used as the B source since it has a higher vapor pressure than elemental B itself. It was found that sub-monolayr adsorption of B could be controlled by observing the RHEED intensity oscillation of B absorved surface. When Si was epitaxially grown on Si (111) surface where the B was adsorbed more than 1/3 monolayrs (ML), period of the RHEED oscillation was twice of that for growth on the Si substrate where the B was adsorbed less than 1/3 ML.From the position where the period changes, segregation length of B could be estimated to be 14A at Si growth temperature of 450ﾟC.It increased rapidly with increase of the substrate temperature of the Si MBE growth, therefore, B is believed to be a promising p-type surfactant. Actual surfactant effect for a Si/Ge/Si strained super lattice is presently being studied.