Effects of low-temperature-grown buffers on pulsed-laser deposition of GaN on LiNbO3

The authors have investigated the effects of low-temperature-grown (LTG) GaN buffer layers on the pulsed-laser deposition of GaN films on LiNbO3. LiNbO3 substrates with atomically flat surfaces have been prepared by annealing in a box constructed from blocks of single crystal LiNbO3 wafers. When the GaN growth temperature is lowered from 700to580°C, the GaN∕LiNbO3 interfacial layer thickness is reduced. When these LTG-GaN layers, which have a thickness of 20nm, are employed as buffers for the subsequent high temperature growth of 200-nm-thick GaN layers, a decrease in root-mean-square surface roughness and a reduction in tilt and twist mosaicities are observed. This technique seems quite promising for achieving high quality GaN on LiNbO3 substrates, which is attractive for the fabrication of future optoelectronic integrated circuits.