Epitaxial Growth of ZnO on LiAlO2 and LiGaO2 Substrates by Chemical Vapor Deposition

Epitaxial growth of ZnO on a tetragonal LiAlO2 (100) substrate and an orthorhombic LiGaO2 (100) substrate was examined using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Results indicated that the crystal structure plays a major role on the orientation selection. The m-plane ZnO is favorable to grow on both substrates due to its low lattice mismatch to the substrates. However, the kinetic factor cannot be ignored on epitaxial growth. At low temperatures, limited adatom mobility can lead to the nucleation of crystals having a less favorable orientation, such as the c-plane ZnO on LAO or the random oriented ZnO on LGO. In addition, the morphology of the epitaxially grown crystals is affected by the anisotropy of the growth rate. For the c-plane ZnO, high anisotropy at low growth temperature results in rod shape crystals. At higher temperatures, the anisotropy is decreased and lateral growth leads to wineglass shape crystals.