2006 Fiscal Year Final Research Report Summary
High-Voltage GaN p-n Junction Diodes with Low Leakage Current
| Project/Area Number |
17560307
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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 |
Electron device/Electronic equipment
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| Research Institution | University of Fukui |
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Principal Investigator |
KUZUHARA Masaaki University of Fukui, Department of Electrical and Electronics Engineering, Professor, 工学研究科, 教授 (20377469)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAMOTO Akio University of Fukui, Department of Electrical and Electronics Engineering, Professor, 工学研究科, 教授 (90210517)
HASHIMOTO Akihiro University of Fukui, Department of Electrical and Electronics Engineering, Associated Professor, 工学研究科, 助教授 (10251985)
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| Project Period (FY) |
2005 – 2006
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| Keywords | nitride semiconductor / p-n junction / diode / field effect transistor / GaN / p-type semiconductor / breakdown voltage / on resistance |
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| Research Abstract |
In this research work, the optimum post rapid thermal annealing (RTA) conditions have been investigated to electrically activate Mg acceptors doped in the MOCVD grown GaN. It is widely known that the MOCVD as-grown Mg-doped GaN shows high resistivity unless the sample is annealed after crystal growth. This is due to the H passivation of Mg acceptors in GaN. So far, the optimum annealing conditions have not been studied depending on the Mg concentration. It was found that there was an optimum annealing temperature depending on the Mg doping concentration in GaN. Results showed that the maximum hole concentration at room temperature was about 8x10^<17>cm^<-3> regardless of the Mg doping concentration between 1.25x10^<19> and 1x10^<20>cm^<-3>. A maximum activation efficiency of over 80 % was obtained for the sample doped with 1.25x10^<19>cm^<-3> when the sample was characterized at 200℃. Electrical characterization at elevated temperatures revealed that excessive high temperature annealing for heavily Mg-doped GaN samples resulted in Mg-related donor level generation, leading to the reduced Mg acceptor activation at elevated temperatures. This is the reason why Mg-doped GaN samples with 2.5x10^<19>cm^<-3> and 5x10^<19>cm^<-3> exhibited a maximum hole concentration of 8x10^<17>cm^<-3> annealed at 750℃ and 650℃, respectively.
Based on the above results, p-n junction diodes have been fabricated. The doping concentration in n-GaN was chosen to be 5x10^<17>cm^<-3>. The breakdown voltage of the diodes was more than 100V and it increased with increasing the measurement temperature, suggesting the breakdown mechanism is due to avalanche breakdown. It was found that the estimated breakdown field was as high as 2.9MV/cm, which was proved to be very close to the theoretical limit of 3.3MV/cm.
We believe that these results provide useful information as design parameters for the fabrication of GaN-based electronic devices with p-type materials.
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