研究目的
To develop a high-quality p-GaN metal-insulator-semiconductor (MIS) interface with low-density trap states using SiNx as the gate dielectric layer and effective surface treatments.
研究成果
The SiNx/p-GaN MIS interface with two-step surface treatment achieves the lowest trapped charge density (5 × 10^10 cm^?2) and reduced interface state density (~1–2 × 10^12 cm^?2 · eV^?1), attributed to effective removal of carbon and oxygen impurities and suppression of Mg-Ga-O disordered layer. This high-quality interface is promising for p-GaN-based electronic devices, with better stability and negligible hysteresis compared to other dielectrics.
研究不足
The study focuses on MIS capacitors and may not fully address device-level performance in transistors; the two-step treatment process might be complex for large-scale manufacturing; frequency dispersion in accumulation region is attributed to series resistance, not fully eliminated.
1：Experimental Design and Method Selection:
The study aims to improve the interface properties of p-GaN MIS capacitors by using SiNx as an oxygen-free gate dielectric and implementing a two-step surface pre-treatment (HCl etching and (NH4)2S passivation) to remove impurities and suppress trap states. Methods include capacitance-voltage (C-V) measurements, transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) for characterization.
2：Sample Selection and Data Sources:
Mg-doped p-GaN epitaxial layers grown on unintentionally doped GaN/sapphire templates by metal-organic chemical vapor deposition (MOCVD). Samples include as-grown p-GaN (sample A) and p-GaN with two-step surface treatment (sample B).
3：List of Experimental Equipment and Materials:
Equipment includes Agilent 4284A LCR meter for C-V measurements, JEOL JEM-2100 HR-TEM for microstructure evaluation, Bruker MM-SPM AFM for surface morphology, PHI Quantera SXM XPS for chemical analysis, E-beam evaporator for metal deposition, and radio frequency sputtering for SiNx deposition. Materials include dilute HCl, (NH4)2S solution, Ni/Au for Ohmic contacts, Ti/Au for gate electrodes, and SiNx film.
4：Experimental Procedures and Operational Workflow:
p-GaN activation at 700°C in N2; Ohmic contact deposition and annealing; surface pre-treatment (HCl etching for 5 min and (NH4)2S passivation at 75°C for 20 min for sample B); SiNx deposition by sputtering; patterning by laser photolithography and lift-off; gate electrode deposition; C-V measurements at 1 MHz and 100 KHz frequencies; TEM, AFM, and XPS analyses.
5：Data Analysis Methods:
Trapped charge density calculated from C-V hysteresis using Qt = (Cox * ΔVFB) / (q * A); interface state density (Dit) evaluated using Terman method by comparing experimental C-V curves to ideal simulated ones; XPS data analyzed for element concentrations and chemical states.
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