2006 Fiscal Year Final Research Report Summary
Suppression of Gate Leakage Current in AlGaN/GaN Heterostructures and Polarity-Controlled MBE Growth of GaN-Based Semiconductors
| Project/Area Number |
17560013
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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 | Hokkaido Institute of Technology |
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Principal Investigator |
SAWADA Takayuki Hokkaido Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (40113568)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Kazuhiko Hokkaido Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (30226500)
KITAMORI Kazutaka Hokkaido Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (40153134)
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| Project Period (FY) |
2005 – 2006
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| Keywords | A1GaN / GaN Heterostructure / Schottky Diode / 2-Dimensional Electron Gas / Gate Leakage Current / HEMT Device / MBE Growth / MIS Structures / Interface State Density |
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| Research Abstract |
The following results have been obtained from investigations of electrical properties of AlGaN/GaN HEMT structures and growth of (Al, In)GaN layers by RF-MBE:
1. Characterization and control of Ni/n-(Al)GaN interfaces; Leakage current due to "surface patches" is much larger for MBE samples. The inclusion of N-polarity domains in the Ga-polarity layer seems to be the origin of the patches for MBE samples, while dislocations are likely the origin for MOCVD samples.
2. Suppression of gate leakage current; Ni/anodic-Al_2O_3/i-AlGaN/GaN structures effectively suppressed the reverse leakage current down to 10^<-7>A/cm^2 range, after optimum annealing in N_2 at 400℃. Measured C-V curves indicated a small density of states at anodic-Al_20_3/A1GaN interface.
3. Influence of surface preparation and AlGaN thickness on 2DEG; (1) Native oxides of AlGaN/GaN increase 2DEG density. The phenomenon can be explained by the lowering of the surface barrier. (2) The thinner the AlGaN layer is, the lower the 2DEG density is, accompanied with reduction of the electron mobility. Theoretical calculation indicated that the 2DEG density varies with a constant SBH. (3) The effective SBH decreased with decreasing the AlGaN layer owing to combined leakage currents due to the patches and simple tunneling through the surface barrier.
4. Growth of (Al, In)GaN layers by RF-MBE; (l) The Al composition of AlGaN layer directly depends on Al beam intensity rather than Al/(Al+Ga) beam ratio, while Ga beam intensity is correlated with the quality of the layer. (2) A Monte Carlo simulation for RF-MBE growth of GaN, which includes formation of anti-site defects and vacancy defects, was developed. (3) Poor adhesion of the MBE-grown InN layer to sapphire substrate is greatly improved by the use of GaN buffer layer.
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Research Products
(12 results)
