A New 4H-SiC Lateral Merged Double Schottky (LMDS) Rectifier With Excellent Forward and Reverse Characteristics

The novel characteristics of a new Schottky rectifier structure, known as the lateral merged double Schottky (LMDS) rectifier, on 4H-SiC are explored theoretically and compared with those of the compatible conventional 4H-SiC Schottky rectifiers. The anode of the proposed lateral device utilizes the trenches filled with a high barrier Schottky (HBS) metal to pinch off a low barrier Schottky (LBS) contact during reverse bias. Numerical simulation of any such SiC structure is complicated by the fact that the thermionic emission theory predicts the reverse leakage current to be orders of magnitude smaller than the measured data. We, therefore, first propose a simple empirical model for barrier height lowering to accurately estimate the reverse leakage current in a SiC Schottky contact. The accuracy of the empirical model is verified by comparing the simulated reverse leakage current with the reported experimental results on different SiC Schottky structures. Using the proposed empirical model, the two-dimensional (2-D) numerical simulations reveal that the new LMDS rectifier demonstrates about three orders of magnitude reduction in the reverse leakage current and two times higher reverse breakdown voltage when compared to the conventional lateral low barrier Schottky (LLBS) rectifier while keeping the forward voltage drop comparable to that of the conventional LLBS rectifier. A unique feature of the 4H-SiC LMDS rectifier is that it exhibits a very sharp PiN diode-like reverse blocking characteristic in spite of the fact that only Schottky junctions are used in the structure. The reasons for the improved performance of the LMDS rectifier are analyzed and design tradeoff between the forward voltage drop and the reverse leakage current is provided by varying the device parameters. Finally, this work demonstrates a simple way of achieving excellent Schottky characteristics on 4H-SiC and provides the incentive for experimental exploration.