Kinetic Process Of Nitridation On The α-sapphire Surface In The Combination Of KMC And MD

Nitride compound semiconductors are widely used for optoelectronic devices as LEDs and laser diodes. And AlGaN/GaN based LEDs are focused by large amount of researchers as it is a nice choice for emitting DUV light with large band gap, strong polarization effects, high critical field strength, high electron saturation velocity and thermal conductivity and other outstanding features.However, it is very difficult to reduce defect, QCSE and polarized light emitting as it is not easy to operate a nice process of growth on α-sapphire surface. Nitridation of α-sapphire is an important operation to improve this situation and to obtain high quality semiconductors. Several studies have reported the formation of AlN layer on α-sapphire (0001) surface by exposing ammonia, N-radical or N2-plasma in MBE as well as MOVPE. And the discussion of calculated result of energy pointed the mode of growth is varied with conditions. Despite these experimental efforts, the atomic-scale understanding of dynamic process by nitrogen on α-sapphire and the mechanism of over nitridation are still unclear.In this paper, we investigate the dynamic process of N atoms on the α-sapphire surface by the combination of kinetic Monte Carlo (KMC) and molecule dynamics (MD) method to clarify the process on the surface and under the layer. A stable layer of α-sapphire(0001) to absorb N atoms is developed and calculated by Vienna Ab-initio Simulation Package (VASP). We observed the dynamic process of nitridation in MBE system through RHEED under different temperature. A combination of the experiment and simulation clarify the mechanism of nitridation and over-nitridation as well as confine the best condition of nitridation.