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.

Index Terms—Silicon carbide, numerical simulation, lateral Schottky, barrier lowering.

The full paper can be downloaded from http://web.iitd.ac.in/~mamidala/id11.htm

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