The surface modification and reactivity of LiGaO_2 substrates during GaN epitaxy

摘要

The chemistry and kinetics of lithium gallate (LGO) substrates during nitridation are investigated. Nitridation experiments have been carried out using two remote nitrogen RF plasma sources: in an MBE system and in a remote plasma MOCVD system. The difference between the two nitrogen sources is the pressure. The experiments were run in parallel to demonstrate that the same heterogeneous chemistry applies during LGO nitridation in both MBE and MOCVD environments, provided that the same species is produced in the gas phase. Surface analysis techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and spectroscopic ellipsometry (SE), show that an optimal temperature of about 600℃ and an optimal time that depends on the incident nitrogen density exists that results in the formation of ～5 A of GaN on LGO. The nitridation process competes with lattice damage that is enhanced by the presence of hydrogen.