In this paper, we report the comparative study of both lateral n-SiCN/p-porous silicon (PS) and vertical n-SiCN/p-porous silicon (PS) heterojunctions for low cost and high temperature ultraviolet (UV) detecting applications. The cubic crystalline n-SiCN films were deposited on p-(100) PS substrate with rapid thermal chemical vapor deposition (RTCVD). Owing to the PS layer features high resistivity and the flexibility, thus suppress the dark current to obtain a high photocurrent/dark current ratio (PDCR). Therefore, these junctions on PS substrate have achieved high sensing performances. For example, with a 0.5 mW/cm(2) sensing area and under the condition of room temperature and -5 V bias, the measured PDCR of the lateral n-SiCN/p-PS and vertical n-SiCN/p-PS heterojunctions with and without irradiation of 254 nm UV light, are up to 98.3 and 85.4, respectively. Even at the high temperature of 200 degrees C, they still have PDCR of 8.5 and 7.42, respectively. These values are better than that of the reported ZnO on GaAs substrate or beta-SiC on Si substrate without porous treatment UV detectors. (C) 2015 Elsevier Ltd. All rights reserved.