The application of Si detectors in the high-energy physics experiments requires a reliable performance in adverse radiation conditions, which is the main test for these detectors. Devices requiring high voltages face the problem of high peak electric field in the vicinity of junction termination. Various contours and design principles have evolved in the effort to reduce these peak fields. Out of many proposed solutions, metal-overhang and guard ring techniques are of general interest for improving the breakdown performance of the Si detectors (in the vertical devices). In the present work, the breakdown performance of metal-overhang and field-limiting ring techniques is compared for various values of junction depth, substrate resistivity, relative permittivity of the dielectric passivant and fixed oxide charge under similar conditions. The results demonstrate the superiority of metal-overhang technique over field-limiting ring technique for planar shallow-junction high-voltage Si detectors used in high-energy physics experiments. (C) 2004 Elsevier Ltd. All rights reserved.