ATOMIC-LAYER CONTROLLED SUPER-HETEROEPITAXY AND PROPERTIES OF LANTHANOIDE/SEMICONDUCTOR STRUCTURES

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There has been increasing interest in the combination of rare-earth (RE) elements and III-V semiconductors. One of the reasons is RE reacts with group-V elements to form lanthanoides such as ErP and ErAs. Incorporation of the lanthanoide layrs in semiconductor heterostructures is expected to facilitate new physics in quantum-confined systems and novel electronic devices, since the lanthanoides exhibit semimetallic behavior.In this research project, we investigated atomic-layr controlled super-heteroepitaxy of ErP on InP substrates. Gas-flow sequence used for the epitaxy was basically the same as that for "delta-doping" of Er. Results obtained experimentally are summarized as follows ;1) Rutherford backscattering (RBS) measurements showed that Er sheet density in samples increases linearly with Er-exposure duration and exhibits no saturation even at 80 min, and that Er atoms, corresponding to 1 mono-layr (ML) in number, are incorporated during the Er-exposure duration of 23 min.2) In 4.2K photoluminescence (PL) measurements, characteristic Er-related emissions due to 4f-intra shell transitions were observed, which were quite different from those in InP doped uniformly with Er.3) X-ray crystal truncation rod (CTR) scattering measurements using synchrotron radiation revealed clearly that Er atoms are incorporated having the NaCl crystal arrangement with P atoms, which was also supported by fluorescence-detected extended X-ray absorption fine structure (EXAFS) measurements. The resultant Er profiles were almost symmetric and were characterized by Er atoms confined in several MLs in thickness.4) Epitaxy of ErP on InP were observed by atomic force microscope (AFM) and ultra-high vacuum scanning tunnelling microscope (UHV-STM). Surface morphology depended strongly on substrate temperature and Er-exposure duration. There were generation of misfit dislocations along the [110] direction and formation of voids and holes.