AlN/Mo/Sc0.2Al0.8N　composite　structure　films　were　prepared　on　Si（100）　substrate　by　pulsed　DC　magnetron　sputtering，　and　the　epitaxy　of　GaN　films　was　grown　by　metal-organic　chemical　vapor　deposition（MOCVD）.　Atomic　force　microscopy，　high-resolution　X-ray　diffraction，　powder　X-ray　diffraction，　scanning　electron　microscopy　and　Raman　spectroscopy　were　used　to　study　the　effect　of　the　thickness　of　the　Mo　layer　on　the　crystal　quality　of　the　Sc0.2Al0.8N　layer　and　the　GaN　epitaxial　layer，　and　the　importance　of　the　Sc0.2Al0.8N　layer　for　the　GaN　epitaxial　layer　grown　on　Mo　was　also　studied.　The　results　show　that　the　thickness　of　the　Mo　layer　is　an　important　factor　affecting　the　Sc0.2Al0.8N　layer　and　the　GaN　epitaxial　layer，　and　the　Sc0.2Al0.8N　layer　is　of　great　significance　to　the　epitaxy　of　GaN　on　Mo.　When　the　thickness　of　the　Mo　layer　is　400　nm，　the　crystal　quality　of　the　GaN　epitaxial　layer　is　the　best，　the　full　width　at　half　maximum　of　the　X-ray　diffraction　on　the　GaN（002）　surface　is　0.51°，　and　the　compressive　stress　calculated　by　Raman　spectroscopy　is　483.09　MPa.　©　2023　Chines　Academy　of　Sciences.　All　rights　reserved.