1. Introduction

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^^zcECCFd^z! 1! z0.,¥ ping effect and improved electrical performance in buried-gate 4H-SiC MESFETs.

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The wide band gap materials, such as silicon carbide (SiC) [1-3] and gallium nitride (GaN) [4-6], are the third generation semiconductor materials, which had been developed after the Silicon (Si) and gallium arsenide (GaAs) materials. Especially, the SiC material is very well- /1%0! z"+.z0\$!z\$%#\$z2+(0#!\_z\$%#\$z,+3!.z\* z\$%#\$z0!),!.01.!z,,(%0%+\*/z 1!z0+z%0/z/1,!.%¥ or material properties. Silicon carbide has been known investigated since 1907 after Captain H. J. Round demonstrated yellow and blue emission by application bias between a metal needle and SiC crystal. The potential of using SiC in semiconductor electronics was already recognized about a half of century ago. The most remarkable SiC properties include the 3% !z\* z#,\_z2!.5z(.#!z2(\*\$!z.!' +3\*z"%!( \_z\$%#\$z0\$!.)(z+\* 10%2%05\_z\$%#\$z)4¥ imum operating temperature and chemical inertness and radiation hardness.

Therefore the microwave power devices based on 4H-SiC have received increasing attention. The MESFETs (Metal Semiconductor Field Effect Transistor) is a hot research topic [7-10].

For the SiC power MESFETs, the breakdown voltage is a very important parameter that allows the power devices to achieve a specific power density and power conversion. Prior research has proposed many techniques to improve the breakdown voltage [11-15]. The conventional termination techniques include of the Field Plate structure in the source or drain electrode [16], RESURF (Reduced Surface field) technology [17], floating metal rings [18-19], p-epi guard .%\*#/zeECf\_z!0zeEDwEFf^z \*z+. !.z0+z+,0%)%6!z0\$!z/1."!z!(!0.%z"%!( z\* z%),.+2!z0\$!z.!'¥ +3\*z2+(0#!\_z0\$!z\*!3z0!\$\*+(+#%!/z\$ z!!\*z,.+,+/! \_z3\$%\$z%\*(1 !/z+"z0\$!zzc¥ duced BULk Field) [24] and complete 3D RESURF [15]. For the new power devices based on the silicon materials, the trade-off relationship had been broken between the breakdown voltage and specific on resistance by the complete 3D RESURF [15]. The high breakdown voltage had been obtained on the ultra thin epitaxial layer with the REBULF technology [24]. It can be sure 0\$0z0\$!/!z\*!3z0!\$\*+(+#%!/z\*z!z0.\*/,(\*0! z %.!0(5z0+z0\$!z%z,+3!.z
/^z+\_z/!2!.¥

© 2013 Yang et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Yang et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

al new SiC power MESFETs had been designed to optimize the characteristic of the breakdown voltage, specific on resistance, frequency and transconductance.

holes for the *p*-channel MESFETs that transport as the carriers in the channel. However, whether in the *n*-channel or *p*-channel MESFETs, the unique majority carriers undertake

Silicon Carbide Power MESFET http://dx.doi.org/10.5772/51085 293

In this section several new structures for the 4H-SiC power MESFETs are provided in which

Fig. 3 is the schematic diagram of the 4H-SiC MESFETs with the field-plate [25], which is the same as the channel-recessed device except the Si3N4 layer on top of the surface. The gate length (*L* g) is 0.5 µm, and the space of gate-source (*L* gs) and gate-drain (*L* gd) are 0.5 µm and

transporting the current. So, the MESFETs is an unipolar device.

the surface electric field and breakdown characteristics are optimized.

3. New 4H-SiC Power MESFETs

Figure 2. Depletion region in MESFETs with positive drain bias.

1.0 µm, respectively. The thickness of Si3N4 is 100 nm.

3.1. Field-Plated 4H-SiC MESFETs structure

Figure 3. Field-plate SiC MESFETS structure.
