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Photosensitive Capacitance Effect In High-purity Semi-insulating 4H-SiC

Published online by Cambridge University Press:  18 June 2014

Joseph Register ,
Stephen E. Saddow  and
Kevin Boulais
Joseph Register
Affiliation:
University of South Florida, Dept. of Electrical Engineering, 4202 E. Fowler Ave., Tampa, FL 33620, USA
Stephen E. Saddow
Affiliation:
University of South Florida, Dept. of Electrical Engineering, 4202 E. Fowler Ave., Tampa, FL 33620, USA
Kevin Boulais
Affiliation:
Naval Surface Warfare Center, Dahlgren, VA
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Abstract

We demonstrate a novel optically tunable photosensitive capacitor (PSC) made from high-purity semi-insulating 4H-SiC. Photosensitive capacitors can provide continuously variable reactive tuning in RF circuitry or enable capacitive-optical sensing applications. Unlike varactors, PSCs often do not require a DC bias voltage to operate. To demonstrate the effect, we fabricated several 1cm x 1cm square photocapacitor devices from bulk material using metal-evaporated Ti/Au contacts using a simple planar parallel-gap geometry. IV curves were taken of the devices using an HP-4145B semiconductor parameter analyzer to verify Schottky behavior as a function of DC bias. The samples were then illuminated with pulsed below-bandgap 470 nm and 590 nm high intensity LED light sources. The resulting data demonstrated an increase in capacitance, Cs, and a drop in resistance, Rs, with increasing optical intensity incident on the device. The observed shifts in both Cs and Rs were repeatable. At a measurement frequency of 33 kHz. Cs increased from its nominal value of 186.7 pF to 575.6 pF while Rs dropped from 150.0 kΩ to 22.4 kΩ. This demonstrates the existence of the photocapacitance effect in high-purity semi-insulating 4H-SiC and thus warrants further investigation. The underlying phenomenon of the effect is suspected to be light interaction with the dominant deep level traps through the Shockley–Read–Hall (SRH) recombination mechanism.

Keywords

semiconductingopticaldefects
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1693: Symposium DD – Silicon Carbide–Materials, Processing and Devices , 2014 , mrss14-1693-dd06-18
Copyright
Copyright © Materials Research Society 2014 

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