Recently,　the　deep　ultraviolet　(DUV)　photodetectors　fabricated　from　two-dimensional　(2D)　hexagonal　boron　nitride　(h-BN)　layers　have　emerged　as　a　hot　research　topic.　However,　the　existing　studies　show　that　the　h-BN-based　photodetectors　have　relatively　poor　performance.　In　this　work,　C　doping　is　utilized　to　modulate　the　properties　of　h-BN　and　improve　the　performance　of　the　h-BN-based　photodetectors.　We　synthesized　the　h-BN　atomic　layers　with　various　C　concentrations　varying　from　0　to　10.2　atom　%　by　ion　beam　sputtering　deposition　through　controlling　the　sputtering　atmosphere.　The　h-BN　phase　remains　stable　when　a　small　amount　of　C　is　incorporated　into　h-BN,　whereas　the　introduction　of　a　large　amount　of　C　impurities　leads　to　the　rapidly　deteriorated　crystallinity　of　h-BN.　Furthermore,　the　DUV　photodetectors　based　on　C-doped　h-BN　layers　were　fabricated,　and　the　h-BN-based　photodetector　with　7.5　atom　%　C　exhibits　the　best　performance　with　a　responsivity　of　9.2　mA.W-1,　which　is　significantly　higher　than　that　of　the　intrinsic　h-BN　device.　This　work　demonstrates　that　the　C　doping　is　a　feasible　and　effective　method　for　improving　the　performance　of　h-BN　photodetectors.