1999 Fiscal Year Final Research Report Summary
Study on electrochemical etching of nitride semiconductors
| Project/Area Number |
09650350
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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 |
Electronic materials/Electric materials
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| Research Institution | Fukui University |
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Principal Investigator |
YAMAMOTO Akio Faculty of Engineering, Fukui University Professor, 工学部, 教授 (90210517)
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| Co-Investigator(Kenkyū-buntansha) |
HASHIMOTO Akihiro Faculty of Engineering, Fukui University Associate Professor, 工学部, 助教授 (10251985)
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| Project Period (FY) |
1997 – 1999
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| Keywords | electrochemical etching / GaN / hole injection / photo-electrochemistry / needle-like hillocks / detection of dislocations / 貫通転位 |
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| Research Abstract |
III-nitrides such as GaN are known to be chemically stable. This results in that chemical dissolution processes can not be applied to these semiconductors. The purpose of this study is develop etching technologies for III-nitrides as a surface polishing, selective removal in device process and/or defect detection in the crystals, through the investigation of electrochemical behavior of III-nitrides, especially GaN. Results obtained are summarized as follows.
1) Electrochemical properties of GaN: Basic electrochemical properties of GaN are similar to those of other semiconductors such as GaAs. Because of notable non-uniformity in electrical properties and/or defect density and, moreover, presence of nano-pipe defects in GaN crystals grown on sapphire substrates, reproducibility of electrochemical data obtained for those samples are very low. This is a major cause for misunderstandings of electrochemical properties of GaN, such as the passivation effects.
2) Electrochemical behavior and non-uniformity of GaN: By clarifying the relationships between electrochemical behavior and electrical properties and presence of defects, it is possible to evaluate the uniformity of GaN films from electrochemical data.
3) Photo-electrochemical etching of n-type GaN - Detection of dislocations -: Electrochemical etching (anodic dissolution) of n-type semiconductors needs extra hole supply. Under the He-Cd laser (wavelength 325 nm) irradiation, photo-electrochemical etching of n-type GaN film on sapphire is made in a NaOH solution. After the etching of current density 〜1mA/cmィイD12ィエD1 and etching time of 1 hour, needle-like hillocks with a density of 10ィイD18ィエD1-10ィイD110ィエD1 cmィイD1-2ィエD1 are formed on the etched surface. From the shape and the density of the hillocks, it is reasonable to interpret that such a needle-like hillock is due to a threading dislocation in the samples. Thus, electrochemical etching becomes a simple and safe method for defect detection for III-nitrides.
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