On the design of the channel region in 4H-SiC JBS diode through an analytical model of the potential barrier

摘要

In this paper, we propose a tool for the design of 4H-polytype Silicon Carbide Junction Barrier Schottky, JBS, diodes, which are promising devices for their low on-state resistance and their high blocking voltage. Our tool calculates the width of the channel region in terms of the geometrical and physical parameters and of the doping concentration in order that the device shows forward electrical characteristics similar to that of Schottky Barrier Diode. Their operating principle is defined by the control of the flow of electron carriers through a potential barrier, which is located in the n-type region under the Schottky metal contact surrounded by the p~+-type regions. Indeed, if the electric fields of the p~+-n junctions extend for the whole channel region under equilibrium conditions, the height of the induced potential barrier can be higher than that of the conventional Schottky built-in potential and can affect the electrical characteristics of the device, for example increasing the turn-on voltage. Although they have been firstly developed in Silicon technology, 4H-SiC JBS diodes are easier to fabricate because the electric fields of 4H-SiC p-n junctions have a wider space charge region for the same values of the doping concentrations with respect to Si JBS devices, resulting in a more relaxed design constrain of the channel geometry. Our analytical model can calculate the potential barrier height as function of the geometrical and physical parameters of the device and can evaluate the maximum channel width for which the potential barrier is higher than Schottky built-in voltage. The analytical results are compared through numerical simulations obtained from ATLAS Silvaco software.