An alternative route to form a wide band-gap Cu(In,Al)S-2 (CIAS) thin film with Al content of approximately 23 at.% and its application to ultraviolet (UV) photodetectors (PDs) have been demonstrated. X-ray diffraction patterns and scanning electron microscope micrographs show that the CIAS thin film, formed by 700 degrees C sulfurization of Cu9Al4 (330) compound, is a single phased polycrystalline film with the (112)-preferred orientation and grain size of approximately 400-500 nm. At a 3 V bias voltage, the metal-semiconductor-metal structured UV PD has a dark current of 4.31 x 10(-9) A and a photocurrent of 6.55 x 10(-8) A using electrodes with 5-mu m finger spacing. More than one order of magnitude in photocurrent amplification has been demonstrated. The spectral response of the PD is 0.72 A/W and the cut off wavelength occurs at 380 nm, which suggests that the band-gap of the CIAS film is 3.27 eV. The wide band-gap CIAS film has the potential to be a good candidate for UV PD applications. (C) 2014 Elsevier B.V. All rights reserved.