Low-Temperature Growth of Crystalline Gallium Nitride Films Using Vibrational Excitation of Ammonia Molecules in Laser-Assisted Metalorganic Chemical Vapor Deposition

Abstract

Low-temperature growth of crystalline gallium nitride (GaN) films on c-plane sapphire (α-Al2O3) substrates was achieved by laser-assisted metalorganic chemical vapor deposition (LMOCVD) and coupling laser energy into the chemical reactions. Trimethylgallium (TMGa) and ammonia (NH3) were used as precursors for the growth of GaN films. Through the resonant excitation of rotational–vibrational transition (1084.71 cm–1) of the NH-wagging mode (v2) in NH3 molecules using a wavelength-tunable CO2 laser tuned at 9.219 μm, highly c-axis oriented GaN films were deposited on sapphire at low substrate temperatures from 250 to 600 °C. GaN films with a large thickness of 12 μm were obtained within 1 h at a substrate temperature of 600 °C. The GaN films deposited by LMOCVD showed a higher degree of crystallinity, higher growth rate, and lower defect densities as compared to those synthesized by MOCVD without resonant excitation of NH3 molecules. This low-temperature synthesis technique opens a promising approach to gro...