In　this　letter,　vertically　conductive　GaN　epilayer　on　SiC　substrate　was　achieved　without　the　typically　used　conductive　buffer　layer.　Here,　in　order　to　reduce　the　impacts　of　band　offset　of　different　layers　on　vertical　conductivity　and　improve　the　vertical　carrier　transportation,　an　ultrathin　AlGaN　buffer　layer　was　employed　to　replace　the　thick　conductive　buffer　layer.　Fully-vertical　Schottky　barrier　diode　(SBD)　based　on　this　vertically　conductive　epi-stack　demonstrated　a　much　lower　specific　on-resistance　of　0.84　m　omega　center　dot　cm2　with　superior　thermal　stability.　Moreover,　the　SBD　also　exhibited　an　on/off　ratio　of　similar　to　5　x　109　and　a　nearly　unity　ideality　factor　of　1.08.　This　approach　lays　the　foundation　for　the　heterogeneous　integration　of　GaN/SiC　based　devices.