Impact of Al2O3 Buffer Layers on the Properties of GaN/Si for LED Applications

The growth of GaN on Si substrates using Metal-Organic Chemical Vapor Deposition (MOCVD) and Atomic Layer Deposition (ALD)-grown Al2O3 buffer layers was analyzed for its impact on crystal quality and LED application. Two samples with 10nm and 20nm Al2O3 buffer layers were evaluated through Raman spectroscopy and fitting data of the E2(High) and A1(LO) modes. The sample with 20nm buffer layer demonstrated superior crystalline quality with higher Raman intensities, narrower Full Width at Half Maximum (FWHM), and more stable peak positions across temperature ranges, indicating lower strain and better thermal stability compared to the sample with 10nm buffer layer. The sample with 20nm buffer layer exhibited enhanced phonon lifetimes, lower plasmon damping, and higher carrier concentrations, which are crucial for LED efficiency. Spectroscopic Ellipsometry confirmed the sample with 20nm buffer layer has smoother surface and higher bandgap, providing further advantages for light extraction and energy efficiency. These findings suggest that the sample with 20nm Al2O3 buffer layer offers superior performance for GaN-based LEDs, particularly in terms of improved crystal quality, thermal stability, and reduced defect density. Consequently, the 20nm buffer layer offers a promising pathway for developing high-efficiency GaN-based optoelectronic devices on Si substrates.