Growth and characterization of single crystalline Zn_(0.8-x)Mg_(0.2)Al_xO films with UV band gap on GaN/Al_2O_3 template by RF magnetron sputtering

摘要

Single crystalline Zn_(0.8-x)Mg_(0.2)Al_xO thin films were grown on a GaN/Al_2O_3 template. As the Al content is increased from 0 to 0.06, the optical band gap increased from 3.6 eV to 4.0 eV, growth rate decreased from 6 nm/min to 3 nm/min, and the surface roughness decreased from 17 nm to 0.8 nm. It was observed that interfacial layers were formed between the thin films and the substrates, identified as cubic MgAl_2O_4 in the case of ZnMgAlO/GaN and cubic MgO in the case of ZnMgO/GaN. It was proposed that the MgAl_2O_4 layer, with low lattice mismatch of ~7% against the GaN substrate, acted as the buffer layer to correlate the film and the substrate, resulting in growth of the single crystalline thin films in the case of the ZnMgAlO/GaN system.