Model for Low-Temperature Growth of Gallium Nitride

A low growth temperature is essential to realize low-cost and large-area GaN-based lighting and display. In this work, through detailed investigation under plasma-assisted molecular beam epitaxy, a physical model for low-temperature growth of GaN under N-rich conditions is proposed based on the fact that the desorption process of Ga adatoms can be ignored and the energy for lattice incorporation of Ga adatoms comes only from active N species. A normalized diffusion length (NDL, a dimensionless parameter) is also introduced to provide further insight: the diffusion rate and diffusion time of Ga adatoms are determined by the growth temperature and N flux, respectively; meanwhile the average distance between Ga adatoms is affected by both Ga flux and N flux. Excellent agreement between theoretical predictions and experimental results validates this model and demonstrates the importance of NDL in optimizing the growth condition. The model and NDL could be applied in growing III-nitrides under N-rich conditions by various low temperature growth techniques where group-III adatoms are unable to incorporate into the lattice by their own kinetic energy.