Sb-doped <i>p</i>-type ZnO films were grown on <i>n</i>-Si (100) by electron cyclotron resonance (ECR)-assisted molecular-beam epitaxy (MBE). Room temperature Hall effect measurements reveal that a heavily Sb-doped ZnO sample exhibits a low resistivity of 0.2 Ω cm, high hole concentration of 1.7×1018 cm<sup>-3</sup>, and high mobility of 20.0 cm<sup>2</sup>/V s. Low-temperature photoluminescence (PL) measurements show an Sb-associated acceptor-bound exciton (A<sup>o</sup>X) emission exists at 3.358 eV at 8.5 K. The acceptor energy level of the Sb dopant is estimated to be 0.14 eV above the valence band. Based on these electrical and optical properties, <i>p-n</i> hetero- and homojunction photodetectors employing Sb-doped <i>p-</i>type ZnO films were designed and fabricated. The heterojunction photodiode consists of Sb-doped <i>p-</i>type ZnO grown on <i>n</i>-Si (100) substrate. An Sb-doped <i>p</i>-type ZnO layer with an n-type Ga-doped ZnO layer was grown on a <i>p</i>-Si (111) substrate to form the homojunction. Current-Voltage (<i>I-V</i>) characterizations reveal rectifying characteristics. Good photoresponse to UV light has been demonstrated for both hetero and homojunction photodetectors.