In　order　to　improve　the　performance　of　GaN-on-Si　quasi-vertical　diodes,　this　letter　demonstrates　GaN　quasi-vertical　diodes　with　different　anode　area,　the　anode-cathode　spacing　(Lac)　and　layout　design　of　electrodes　(circular　and　finger　type).　By　optimizing　the　fabrication　process,　the　specific　contact　resistivity　of　ohmic　contact　between　metal　electrodes　and　n-GaN　(ND1×1019cm-3)　is　3.38×10-5Ω.cm2.　Comparing　devices　with　different　structures　shows　that　the　forward　current　density　of　the　diodes　increases　with　the　decrease　of　the　anode　area.　The　increase　of　anode-cathode　spacing　leads　to　the　increase　of　on-resistance.　The　forward　J-V　characteristics　of　the　PN　diodes　with　circular　and　finger-type　anode　are　compared,　the　forward　current　density　of　the　finger-type　diode　is　larger　than　that　of　the　circular　type　diode.　By　optimizing　the　device　structure,　a　circular　GaN　quasi-vertical　diode　with　the　turn-on　voltage　of　3.2V　(@1A/cm2),　the　specific　on-resistance　of　0.97mΩ.cm-2　and　the　on/off　current　ratio　of　109　was　obtained.　©　2021　IEEE.