GaN thin films are grown on Si-terminated (0001) 6H-SiC substrates pre-treated with SiH4 in a metal organic chemical vapor deposition system.The influence of the SiH4 pre-treatment conditions on the SiC surface is carefully investigated.It is found that SiH4 could react with the SiC surface oxide,which will change the surface termination.Moreover,our experiments demonstrate that SiH4 pre-treatment can distinctly influence the AlGaN nucleation layer and the basic characteristics of GaN.