Large Area 6H- and 4H-SiC Photoconductive Switches
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Large Area 6H- and 4H-SiC Photoconductive Switches S. Doğan1,2, F. Yun1, C. B. Roberts3, J. Parish4, D. Huang1, R. E. Myers5, M. Smith, S. E Saddow5, B. Ganguly4 and H. Morkoç1 1 Department of Electrical Engineering, Virginia Commonwealth University, 601 W. Main Street, Richmond, VA 23284, USA. 2 Atatürk University, Faculty of Art & Science, Department of Physics, 25240 Erzurum, Turkey. 3 Tech Explore, LLC, 5273 College Corner Pike #12, Oxford, OH 45056-1055, USA. 4 Air Force Research Laboratory, Wright-Patterson AFB, OH 45433-7919, USA. 5 Electrical Engineering Dept., University of South Florida, Tampa, FL 33543, USA.
ABSTRACT
Photoconductive Semiconductor Switches (PCSS) were fabricated in planar structures on high resistivity 4H-SiC and conductive 6H-SiC and tested at DC Bias voltages up to 1000 V. The gap spacing between the electrodes is 1 mm. The average on-state resistance and the ratio of onstate to off-state currents were about 20 Ω and 3x1011 for 4H-SiC, and 60 Ω and 6.6x103 for 6HSiC, respectively. The typical maximum switch current at 1000 V is about 49 A for 4H-SiC. Photoconductivity pulse widths for all applied voltages were 8-10 ns. The observed performance is due in part to the removal of the surface damage by high temperature H2 etching and surface preparation. Atomic Force Microscopy (AFM) images revealed that very good surface morphology, atomic layer flatness and large step widths were achieved with this surface treatment and these atomically smooth surfaces likely contributed to the excellent switching performance of these devices.
INTRODUCTION
Silicon Carbide (SiC) is considered as a promising material for electronic and optical devices and has advantages over other semiconductors, especially for high temperature and high power applications [1-4]. SiC is from the IV-IV group semiconductor family and has an indirect band gap. In spite of its indirect bandgap, SiC can be applied to various optical devices such as LED and UV detectors [5]. SiC technology has seen tremendous advances in the last decade with a variety of encouraging device and circuit demonstrations because of its high saturation electron velocity (2.0x107 cm/s), thermal conductivity (4.9 W/cm-ºC) and high breakdown field (4 MV/cm) [6,7]. Owing to different arrangement of Si and C atoms within the SiC crystal lattice (individual bond length and local atomic environment by the stacking order) SiC occurs in many different crystal structures, called polytypes. Almost 200 different polytypes of SiC are known. But about 95 % of all publications deal with three main polytypes, 3C, 4H and 6H-SiC. 3C-SiC is the only form of SiC with a cubic crystal lattice structure. The non cubic 4H and 6H-SiC polytypes of SiC are two of many possible SiC polytypes with hexagonal crystal structure.
Downloaded from https://www.cambridge.org/core. North Carolina State University, on 28 Dec 2017 at 08:42:03, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-764-C7.2
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