SiC high voltage SBD

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SiC high voltage SBD

Because the barrier height and critical electric field of Si and GaAs are lower than that of broadband semiconductor, the breakdown voltage and reverse leakage current of SBD made of Si and GaAs are lower and larger. Silicon carbide (SIC) material has a wide band gap (2.2ev-3.2ev), a high critical breakdown electric field (2V / cm-4 × 106v / cm), a high saturation speed (2 × 107cm / s), a high thermal conductivity of 4.9w / (cm · K), a strong chemical corrosion resistance, a high hardness, and a relatively mature material preparation and manufacturing process. It is an ideal new material for making SBD with high voltage resistance, low forward voltage drop and high switching speed.

In 1999, Purdue University of the United States developed 4.9kv SiC Power SBD in the Muri project funded by the United States Navy, which made a fundamental breakthrough in SBD voltage withstand The forward voltage drop and reverse leakage current of SBD directly affect the power loss of SBD rectifier and the system efficiency. It is contradictory that low forward voltage requires low Schottky barrier height and high reverse breakdown voltage requires as high barrier height as possible. Therefore, the choice of barrier metal is very important because it must be considered as a compromise. Ni and Ti are ideal Schottky barrier metals for n-type SiC. Because the barrier height of Ni / SiC is higher than that of Ti / SiC, the former has lower reverse leakage current and the latter has smaller forward voltage drop. In order to obtain sicsbd with low forward voltage and reverse leakage current, the design of sicsbd with Ni contact and Ti contact and high / low barrier bimetal groove (DMT) structure is feasible. With this structure, the reverse leakage current of sicsbd is 75 times smaller than that of planar Ti Schottky rectifier at 300V reverse bias, and the forward leakage current is similar to that of nisbd. Using 6h sicsbd with protective ring, the breakdown voltage is up to 550V.

According to reports, c.m.zetterling et al. Epitaxed 10 μ m n-type layer on 6h SiC substrate, and then formed a series of parallel P + strips by ion implantation. The top barrier metal is ti. This structure is similar to that of junction barrier Schottky (JBS) device in Figure 2. The forward characteristics are the same as that of Ti Schottky barrier, and the reverse leakage current is between PN and Ti Schottky barrier, The on state resistance density is 20 m Ω· cm2, the blocking voltage is 1.1 kV, and the leakage current density is 10 μ A / cm2 under 200 V reverse bias. In addition, R. rayhunathon reported the development results of p-type 4H? Sicsbd and 6h? Sicsbd. The reverse breakdown voltage of p-type 4h-sicsbd and 6h-sicsbd with Ti as metal barrier is 600V and 540V respectively, and the leakage current density under 100V reverse bias is less than 0.1 μ A / cm2 (25 ℃).

SiC is an ideal material for making power semiconductor devices. On May 4, 2000, Cree of the United States and Kansai Electric Power Company of Japan jointly announced the successful development of 12.3kv SiC power diodes, with a forward voltage drop of VF of 4.9v at a current density of 100A / cm2. This fully shows the great power of SiC material to make power diodes.

In SBD, devices with SiC and JBS structure have great development potential. In the field of high-voltage power diodes, SBD will definitely occupy a place.