Radical enhanced growth of GaN on Si with the buffer layer of GaN at a low temperature of 600 °C

Abstract

Gallium nitride (GaN) films have been grown on Si (111) substrates with low-temperature GaN as a buffer layer using a newly developed Radical Enhanced Metal Organic Chemical Vapor Deposition (REMOCVD) system. This REMOCVD system has three features; (1) the application of very high-frequency (VHF) of 100 MHz to increase the plasma density, (2) the introduction of H₂ gas together with N₂ gas in the plasma discharge region to generate active NH_x radical species in addition to nitrogen radicals, and (3) the radical supply under remote plasma arrangement with suppressed charged ions and photons by employing a Faraday‘s cage. Using this new system, we have studied the homoepitaxial growth of GaN. It was found that high-quality crystals can be grown by REMOCVD at temperatures of 800 °C lower than those of MOCVD. However, the buffer layer is necessary for the heteroepitaxial growth of GaN on Si. In the present study, the low-temperature GaN (LT-GaN) grown at 600 °C was used as the buffer layer. The growth conditions such as the effect of N-termination of Si and the effect of thickness of LT-GaN as a buffer layer were optimized. The surface morphology and the cleaved cross-sectional view of GaN grown on Si substrates were studied by scanning electron microscopy (SEM). The crystal quality of GaN grown on Si substrates was evaluated by X-ray diffraction (XRD). The epitaxial growth of GaN on Si (111) substrates was achieved by the REMOCVD method with a growth rate of approximately 0.6 µm/h at a low temperature of 800 ℃. The present REMOCVD system is a very promising method for the growth of GaN on Si at relatively low temperatures without using toxic and costly ammonia gas.