研究目的
Investigating the influence of a regrown interface on the electrical properties of AlGaN/GaN heterostructure for recessed-gate MOSFETs fabricated by selective area regrowth, and improving these properties by suppressing residual interface charge.
研究成果
The regrown interface in AlGaN/GaN structures causes degradation of 2DEG electron mobility due to high carrier concentrations and Si impurities. Using a GaN spacer layer and UV treatment before regrowth suppresses unintentional carrier generation and improves electrical characteristics. Fabricated MOSFETs exhibit normally-off operation without hysteresis, reduced on-state resistance, and improved breakdown voltage, demonstrating effective suppression of interface charge.
研究不足
The study did not clarify the atomic state of residual Si impurities after UV treatment. The experiments were conducted at room temperature, and the impact of temperature variations or long-term stability was not addressed. The specific origin of Si contamination (e.g., organosiloxane) was suspected but not definitively identified.
1：Experimental Design and Method Selection:
The study involved fabricating GaN templates on Si substrates using MOCVD, regrowing AlGaN/GaN structures with varying GaN spacer layer thicknesses, and employing UV treatment for surface cleaning. Hall effect measurements, C-V measurements, and SIMS were used to analyze electrical properties and impurities. MOSFET devices were fabricated with selective area regrowth and characterized using electrical measurements.
2：Sample Selection and Data Sources:
GaN templates were fabricated on Si (111) substrates with AlN and AlGaN buffer layers, consisting of undoped and carbon-doped GaN layers. Samples were exposed to air or not before regrowth, and UV treatment was applied to some.
3：List of Experimental Equipment and Materials:
MOCVD system for growth, Hall effect measurement setup, C-V measurement equipment, SIMS analyzer, UV light source (xenon excimer lamp), wet chemical treatment solutions (hydrochloric acid, buffered hydrofluoric acid), SiO2 for masking, Ti/Al/Ni/Au for ohmic contacts, TiN for gate metal, atomic layer deposition for gate insulator, Keiythley 4200 for DC electrical evaluation.
4：Experimental Procedures and Operational Workflow:
Fabricate GaN templates, expose surfaces to air or not, perform UV treatment and wet cleaning if applicable, regrow AlGaN/GaN structures with GaN spacer layers, perform Hall effect, C-V, and SIMS analyses, fabricate MOSFET devices with selective area regrowth, remove mask, deposit gate insulator, form electrodes, and measure electrical properties.
5：Data Analysis Methods:
Data from Hall effect measurements provided electron concentration and mobility, C-V measurements gave carrier profiles, SIMS provided impurity concentrations, and electrical measurements (e.g., transfer characteristics, on-state resistance, breakdown voltage) were analyzed to assess device performance.
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