Epitaxy of single-crystalline GaN films on novel Ca3Ta(Ga0.5Al0.5)3Si2O14 substrates by metal-organic chemical vapor deposition

Abstract

The langasite (La3Ga5SiO14, LGS) is a nearly lattice-matched substrate for epitaxy of GaN films. However, it is a challenge to grow GaN films on LGS substrates by metal-organic chemical vapor deposition (MOCVD) because LGS is unstable in aggressive gas atmosphere at high temperature of ∼1000 °C. To overcome the problem, this study chooses another LGS family crystal Ca3Ta(Ga0.5Al0.5)3Si2O14 (CTAGS) which has the same crystal structure as LGS and is more stable in high temperature. The morphology of GaN films at different growth stages are characterized and the results show continuous and smooth GaN films could be obtained after growing for 3 h. Single-crystalline GaN films are determined by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) measurements. The epitaxial relationship between GaN and CTAGS is GaN(0001)//CTAGS(0001) and GaN(101¯0)//CTAGS(213¯0), the lattice mismatch between GaN and CTAGS is 4.15%. The work is great potential in promoting the development of GaN-based devices.