A study was made of GaN growth on Zn-polar ZnO substrates by using plasma-assisted molecular-beam epitaxy. Before GaN growth, ZnO substrate annealing conditions were optimized. Reflection high-energy electron diffraction patterns after low-temperature GaN buffer layer annealing changed from streaky to spotty, suggesting that Zn and O atoms interdiffused from the ZnO substrate into the GaN epilayer. This interdiffusion resulted in a mix-polar GaN epilayer.

Relation between Interdiffusion and Polarity for MBE Growth of GaN Epilayers on ZnO Substrates. T.Suzuki, C.Harada, H.Goto, T.Minegishi, A.Setiawan, H.J.Ko, M.W.Cho, T.Yao: Current Applied Physics, 2004, 4[6], 643-6