研究目的
To investigate 380 keV proton irradiation effects on p-GaN and n-GaN layers in GaN-based LED by characterizing two-terminal resistances and I-V characteristics, and to understand the differences in irradiation tolerance between p- and n-type GaN.
研究成果
Proton irradiation at 380 keV causes significant increases in resistance for p-GaN at lower fluences compared to n-GaN, due to lower initial hole density in p-GaN. The irradiation tolerance of GaN-based devices is primarily governed by the p-GaN layer, suggesting that improving p-type doping efficiency could enhance device robustness in harsh environments.
研究不足
The initial carrier concentrations of the LED wafer are not precisely known, and the study relies on estimations. The trap introduction rate from PL studies may be overestimated for holes. The effects of complex defects at high fluences are not fully explored, and further studies are needed for a complete understanding of irradiation effects on p-GaN with varying hole concentrations.
1：Experimental Design and Method Selection:
The study uses a commercially available GaN-based LED wafer with InGaN/GaN MQW active layer. Proton irradiation at 380 keV is applied to investigate effects on p- and n-GaN layers by measuring two-terminal resistance and I-V characteristics.
2：Sample Selection and Data Sources:
A GaN-based LED wafer with luminescence peak wavelength around 450 nm is used. Ohmic contacts are formed on p- and n-GaN layers using etching and deposition techniques.
3：List of Experimental Equipment and Materials:
Equipment includes inductively coupled reactive ion etching (ICP-RIE) system, photolithography setup, electron beam evaporator for electrode deposition, rapid thermal annealer, ion-implantation facility at JAEA for proton irradiation, and semiconductor device analyzer B1500A (Agilent Technologies) for I-V measurements. Materials include Ti/Al/Ti/Au for n-GaN contacts and Ag for p-GaN contacts.
4：Experimental Procedures and Operational Workflow:
p-GaN is etched by 700 nm using ICP-RIE to expose n-GaN for contact formation. Ohmic contacts are deposited via electron beam evaporation and annealed. Proton irradiation is performed at room temperature with fluences of 1e14 and 1e15 cm^-
5：I-V characteristics and two-terminal resistances are measured before and after irradiation. Data Analysis Methods:
Resistance data is analyzed using circular transmission line model (c-TLM) to estimate sheet resistance and carrier density. Results are interpreted in terms of trap introduction and carrier density changes.
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