研究目的
Investigating the effect of initial conditions on the growth kinetics and polarity of GaN layers on Si(111) substrates using nitrogen-plasma-assisted molecular-beam epitaxy.
研究成果
High-temperature nitridation of Si(111) substrates at ~850°C for 30 minutes is optimal for the epitaxy of smooth Ga-polar GaN layers. The polarity of GaN layers can be controlled by adjusting the substrate temperature during the initial growth stage, with lower temperatures favoring N-polarity and higher temperatures favoring Ga-polarity.
研究不足
The study is limited by the specific conditions of PA MBE growth and the focus on Si(111) substrates. The mutual diffusion of Ga and Si atoms and the formation of defects due to lattice mismatch are challenges that need further optimization.
1：Experimental Design and Method Selection:
The study used nitrogen-plasma-assisted molecular-beam epitaxy (PA MBE) to grow GaN layers on Si(111) substrates, focusing on the effects of nitridation, growth temperature, and stoichiometry.
2：Sample Selection and Data Sources:
Semi-insulating Si(111) substrates were used, prepared by the Shiraki method, and nitridated at various temperatures and durations.
3：List of Experimental Equipment and Materials:
A Veeco Gen 200 industrial installation for PA MBE, a Riber RFN 50/63 high-frequency plasma source for nitrogen activation, and a Zeiss Supra 25 scanning electron microscope for surface morphology analysis.
4：Experimental Procedures and Operational Workflow:
Substrates were nitridated at temperatures ranging from 400–850°C for 0–60 minutes before GaN growth. GaN layers were grown in two stages: a low-temperature nucleating layer followed by a high-temperature main layer.
5：Data Analysis Methods:
Reflected high-energy electron diffraction (RHEED) for in situ observation, SEM for ex situ morphology analysis, Hall measurements for electrical properties, and photoluminescence (PL) spectra for optical properties.
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