研究目的
To characterize the interface of plasma enhanced chemical vapor deposition (PECVD) dielectrics, SiO2 and SiNx with AlGaN as a function of Al composition, focusing on band offsets and interface studies.
研究成果
SiO2 is suitable for insulating layers or electrical isolation on AlGaN at all compositions but requires an additional passivating interlayer for passivation on Al-rich AlGaN. Si-rich PECVD SiNx is unsuitable for insulating layers or electrical isolation on Al-rich AlGaN due to its band alignment and lack of interface state reduction.
研究不足
The study is limited by the resolution of XPS measurements and the assumption of bandgap values for some materials. The interface Fermi level pinning indicates a significant density of interface states, suggesting SiO2 may not be suitable for surface passivation without an additional interlayer.
1：Experimental Design and Method Selection:
The study employed PECVD to deposit SiO2 and SiNx on AlGaN of varying compositions. X-ray photoelectron spectroscopy (XPS) was used to measure band offsets and interface Fermi level.
2：Sample Selection and Data Sources:
Thin films of GaN, AlGaN, and AlN were grown on low temperature AlN template on c-plane sapphire via metalorganic chemical vapor deposition.
3：List of Experimental Equipment and Materials:
A dual anode x-ray source with Al and Mg anodes in a UHV chamber, a concentric hemispherical analyzer, a Philips X’Pert Materials Research Diffractometer, and a Woollam variable angle spectroscopic ellipsometer were used.
4：Experimental Procedures and Operational Workflow:
SiO2 and SiNx were deposited via PECVD at 250 °C. XPS was used to analyze core levels and valence bands.
5：Data Analysis Methods:
The valence band offset was determined using XPS data, and the bandgap of materials was measured via ellipsometry.
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