研究目的
Investigating the controlled inversion of crystallographic polarity in AlN grown on Si(111) by plasma-assisted molecular beam epitaxy through a two-step growth process.
研究成果
The controlled positioning of a lateral, planar inversion boundary, at which the crystallographic polarity switched from N-polar to metal-polar, was achieved by abruptly changing from Al- to N-rich conditions during AlN growth. The results suggest that methods to include laterally homogeneous layers of Si or another dopant are necessary to achieve uniform polarity inversion in nitride structures.
研究不足
The study notes that relatively low levels of Al–Si eutectic formation combined with lateral variations in the Si incorporation lead to nonuniformity in the polarity inversion. The very small lateral dimensions of the vertical IDs are somewhat surprising, suggesting potential local clustering of the Si and/or Al atoms during their incorporation from the eutectic layer.
1：Experimental Design and Method Selection
The study employs a two-step growth process involving abrupt changes from Al-rich to N-rich conditions during AlN growth to control the position of the polarity inversion boundary.
2：Sample Selection and Data Sources
Samples with AlN and GaN layers were grown on Si(111) substrates by plasma-assisted MBE. The growth system and monitoring equipment were described previously.
3：List of Experimental Equipment and Materials
Plasma-assisted MBE system, Si(111) substrates, Al and N sources for MBE growth.
4：Experimental Procedures and Operational Workflow
AlN growths were initiated by exposing Si substrates to the nitrogen plasma prior to opening the Al-cell shutter. The V/III ratio was increased part way through the AlN growth by decreasing the Al flux and increasing the nitrogen flux.
5：Data Analysis Methods
The sample microstructure and elemental compositions were determined by STEM analysis. Compositional analysis was performed by energy-dispersive X-ray spectroscopy (EDS).
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