Morphology evolution of nano-structured InN grown by MOMBE

In this paper, the evolution of surface morphology and electrical properties during metalorganic molecular beam epitaxy growth of InN on sapphire substrates was investigated. The growth parameters such as growth temperature, flow rate of trimethylindium (TMIn) and AlN buffer were observed to strongly correlated with InN growth. Structural property and surface morphology were analyzed by X-ray diffraction, scanning electron microscopy, atomic force microscopy and transmission electron microscopy, respectively. Electrical and transport properties were obtained by Hall-effect measurement. InN grown directly on sapphire substrate preferred two-dimensional rather than island growth at the growth temperature of 500 °C. Because of residual stress caused by lattice mismatch, however, the thickness of InN with smooth surface was limited at 50 nm. Moreover, In segregation was found under high TMIn flow rate condition. By inserting low-temperature-grown intermediate AlN buffer layer, the structural and electrical properties of InN can be effectively improved. These observations indicate that the growth parameters are essential for engineering the growth of indium nitride.