Comparison of Parameter Extraction Techniques for SiC Schottky Diodes
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0911-B10-12
Comparison of Parameter Extraction Techniques for SiC Schottky Diodes Ming H. Weng, Alton B. Horsfall, Nick G. Wright, Konstantin V. Vassilevski, and Irina P. Nikitina School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne, Merz Court, University of Newcastle, Newcastle upon Tyne, NE1 7RU, United Kingdom ABSTRACT
Schottky barrier diodes fabricated on silicon carbide have been demonstrated as gas sensors for deployment in extreme environments. It has been shown that the interfacial layer formed at the metal – semiconductor junction, determines both the sensitivity and the reliability of the device. Hence, accurate knowledge of the thickness and interfacial trap density of this layer is required to make predictions of the behaviour of the sensor in the environment under investigation and to predict its variation with time. Diode parameters, such as the ideality factor, barrier height and series resistance have been extracted from experimental measurements on palladium Schottky barrier diodes on 4H-SiC, over a range of temperatures. The comparison of the parameters extracted from modified Norde function, Cheung’s method and Thermonic Emission model has been performed. The variation in the barrier height obtained is quite marked between the different techniques. The reverse I-V characteristics have been used to extract thickness of the interfacial layer, by fitting to the experimental data using the Thermionic Emission with Barrier Lowering (TEBIL) model to extract the value of Dit from δ and the ideality factor, assuming the interfacial layer is stoichiometric SiO2. This allows a comparison between the effective interfacial layer behaviour for the different parameter extraction techniques and demonstrates that knowledge of this interfacial layer is influenced by the technique selected. INTRODUCTION
Silicon carbide based Schottky barrier diodes are being developed for use in power electronic systems as well as in gas sensing applications. The interfacial layer has a large influence on the forward I-V characteristics of these devices by its effect on the effective barrier height and ideality factor [1]. For the gas sensing application, incident gas species decompose catalytically on the metal contact and then the hydrogen atoms form a dipole layer at the metalinsulator interface. Hence the presence of an interfacial layer and the associated interfacial traps have a large effect on the behaviour of the sensor. The stability and sensitivity of the sensor are affected by many parameters. The quality of the interface between the metal and the epilayer of the diode is an important factor in high temperature operation. It is therefore, essential to understand the behaviour of both interface traps density (Dit) and interfacial thickness (δ) and their influence on the variation and drift with time for the devices. To achieve a good quality insulating layer is not easy on wide band-gap materials, since the barrier height at the dielectric layer decreases as the band-gap of the
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