ScAlN　thin　films　were　first　prepared　on　Si　(100)　substrate　by　pulsed　DC　magnetron　sputtering.　Then,　GaN　thin　films　were　epitaxial　grown　on　Si　(100)　substrate　with　metal-organic　chemical　vapor　deposition　(MOCVD)　by　using　ScAlN　as　the　buffer　layer.　The　influence　of　the　thickness　of　ScAlN　buffer　layer　on　ScAlN　buffer　layer　and　GaN　epitaxial　layer　is　investigated　by　high　resolution　X-ray　diffraction,　atomic　force　microscopy　(AFM)　and　Raman　spectroscopy.　The　results　show　that　the　thickness　of　ScAlN　buffer　layer　is　an　important　factor　affecting　the　crystal　quality　of　GaN　thin　films.　With　the　increase　of　ScAlN　thickness,　the　full　width　at　half　maximum　(FWHM)　of　ScAlN　(002)　X-ray　diffraction　rocking　curve　continues　to　decrease,　and　the　FWHM　of　GaN　(002)　X-ray　diffraction　rocking　curve　first　decreases　and　then　increases.　When　the　thickness　of　ScAlN　buffer　layer　is　500　nm,　the　crystal　quality　of　GaN　is　the　best,　the　FWHM　of　GaN　(002)　X-ray　diffraction　rocking　curve　is　0.38°,　and　the　tensile　stress　calculated　by　Raman　spectrum　is　398.38　MPa.　©　2022,　Editorial　Office　of　Semiconductor　Optoelectronics.　All　right　reserved.