An analytical model for the forward characteristics of gated p-i-n switches applied to lateral structures

This paper models the forward characteristics of high voltage p-i-n switches. The model is applied to the gated diode switch which is used in the subscriber line interface circuits of telecommunication systems. The p-shield around the cathode of the GDS, which is used for punchthrough protection, is shown to limit the injection efficiency of the cathode in linear devices. The resultant carrier distribution in the drift region is asymmetrical resulting in a large voltage drop. The model predicts that when the cathode efficiency is improved, even at the expense of the anode efficiency, the drift voltage and the drift resistance are reduced. Radial structures, with larger cathode areas and smaller anode areas than the linear structures, show an improved on resistance for competitive device areas. An optimum cathode to anode edge length ratio is obtainable to minimize the on resistance at a fixed current. While gated p-i-n structures are modeled in this paper, these principles are applicable to all lateral double injection devices.