Achieving atomically flat surfaces for LiGaO2 substrates for epitaxial growth of GaN films

Atomically flat surfaces for LiGaO2 substrates have been achieved by annealing two face-to-face substrates at high temperature. Investigation reveals that for as-received LiGaO2 substrates with surface root mean square (RMS) values up to 1.00 nm, it is possible to obtain atomically flat surface by annealing at 1050 deg. C. On the contrary, for very rough LiGaO2 surfaces with larger RMS values, it is hard to achieve atomically flat surface by this technique. The phenomenon has been interpreted in terms of the two main behaviors of surface atoms during annealing, i.e., evaporation into ambient and migration on the surface. Epitaxial growth of GaN films on both atomically flat and as-received rough LiGaO2 surfaces indicates that the application of atomically flat LiGaO2 surface can significantly improve the quality of GaN films.