2005 Fiscal Year Final Research Report Summary
Study of Fluoride Ultra-thin Hetero Structure Devices with Complete Lattice Matched Structures
| Project/Area Number |
16560003
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
TSUTSUI Kazuo Tokyo Institute of Technology, Intercisciplinary Graduate School of Science and Engineering, Associate Professor, 大学院総合理工学研究科, 助教授 (60188589)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Fluoride / Lattice matching / Resonant tunneling / Alloy crystal / CaF2 / CdF2 / MgF2 / SrF2 |
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| Research Abstract |
Fluoride heterosturctres grown on Si substrates are promising material systems for integration of quantum effect devices such as resonant tunneling diodes (RTDs) and conventional Si based devices. However, crystalline quality of the fluoride heterostructures has been not enough for stable device operation. The purpose of this work was improvement of the quality of the structure by introducing fluoride alloy system to every layer (barrier layers and well layer of resonant tunneling structures) so that lattice constant of every layer is matched to that of Si substrate. Basic structure treated in this work was structure of barrier(CaF_2)/well(CdF_2)/barrier(CaF_2)/Si.
The new alloy of Ca_xMg_<1-x>F_2 was introduced to replace the initially grown layer of CaF_2. It was found that the alloy layer can be epitaxially grown on Si substrates with whole range of x. The crystalline structure of the epitaxial alloy was found to be cubic fluorite structure. The most important finding was that the Ca_xMg_<1-x>F_2 layer with near lattice matching condition (x=0.1-0.2) suppressed generation of pin-hole defects which was always appear in the conventional CaF_2 layers. As a result, leakage current was effectively reduced and electrical properties of RTDs using the Ca_xMg_<1-x>F_2 barrier layers were improved.
For the well layers which have been made of CdF_2, the new alloy of Sr_xCd_<1-x>F_2was examined. It was found that the alloy also can be epitaxially grown on the CaF_2/Si structures with whole range of x, and lattice constant was changed with x. RTDs using lattice matched Sr_xCd_<1-x>F_2 (x=0.2-0.3 is matching condition) layers for the well layer exhibited good electrical properties.
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