Heteroepitaxial growth of GaN on atomically flat LiTaO3 (0 0 0 1) using low-temperature AIN buffer layers

We have grown GaN films on atomically-flat LiTaO3 substrates by using pulsed laser deposition (PLD), and we then investigated the effect of the use of low-temperature AlN (LT-AlN) buffer layers on the structural properties of GaN. The full-width at half-maximum (FWHM) values for the crystal orientation distribution of the GaN films in the tilt directions were reduced from 0.48° to 0.17°, and those in the twist directions were reduced from 0.40° to 0.17° by the incorporation of AlN buffer layers grown at 580 °C. The surface morphology of GaN has also been improved by the insertion of LT-AlN buffer layers. X-ray reflectivity measurements have revealed that the interfacial layer thickness between LT-AlN and LiTaO3 is as thin as 1.7 nm, and that the increase in the interfacial layer thickness caused by annealing at up to 700 °C is quite small. These results indicate that the PLD growth of GaN on atomically flat substrates using LT-AlN buffer layers is quite promising for achieving GaN on LiTaO3.