In　this　work,　the　design　and　numerical　analysis　of　a　GaN/InGaN　npn　Avalanche　Heterojunction　Phototransistor　(AHPT)　with　an　open　base　were　performed.　Based　on　a　created　simulation　model,　the　operating　voltage　ranges　for　Avalanche　Photodiode　(APD)　mode　and　Heterojunction　Phototransistors　(HPT)　mode　are　obtained　and　the　APD　and　transistor　characteristics　are　verified　respectively.　The　effects　of　doping　concentration　of　collector　and　base　on　device　performance　are　analyzed,　and　the　device　structure　is　optimized　to　obtain　a　GaN/InGaN　AHPT　with　better　performance　based　on　these　analyses.　©　2023　IEEE.