Epitaxial　growth　of　β-Ga2O3　nanowires　on　silicon　substrates　was　realized　by　the　low-pressure　chemical　vapor　deposition　(LPCVD)　method.　The　as-grown　Si/Ga2O3　heterojunctions　were　employed　in　the　Underwater　DUV　detection.　It　is　found　that　the　carrier　type　as　well　as　the　carrier　concentration　of　the　silicon　substrate　significantly　affect　the　performance　of　the　Si/Ga2O3　heterojunction.　The　p-Si/β-Ga2O3　(2.68　×　1015　cm−3)　devices　exhibit　a　responsivity　of　up　to　205.1　mA/W,　which　is　twice　the　performance　of　the　devices　on　the　n-type　substrate　(responsivity　of　93.69　mA/W).　Moreover,　the　devices’　performance　is　enhanced　with　the　increase　in　the　carrier　concentration　of　the　p-type　silicon　substrates;　the　corresponding　device　on　the　high　carrier　concentration　substrate　(6.48　×　1017　cm−3)　achieves　a　superior　responsivity　of　845.3　mA/W.　The　performance　enhancement　is　mainly　attributed　to　the　built-in　electric　field　at　the　p-Si/n-Ga2O3　heterojunction　and　the　reduction　in　the　Schottky　barrier　under　high　carrier　concentration.　These　findings　would　provide　a　strategy　for　optimizing　carrier　transport　and　interface　engineering　in　solar-blind　UV　photodetectors,　advancing　the　practical　use　of　high-performance　solar-blind　photodetectors　for　underwater　application.　©　2025　by　the　authors.