Paper Title:

Trap Assisted Gas Sensing Mechanism in MISiC Capacitors

Periodical Materials Science Forum (Volumes 556 - 557)
Main Theme Silicon Carbide and Related Materials 2006
Edited by N. Wright, C.M. Johnson, K. Vassilevski, I. Nikitina and A. Horsfall
Pages 621-626
DOI 10.4028/www.scientific.net/MSF.556-557.621
Citation Alton B. Horsfall et al., 2007, Materials Science Forum, 556-557, 621
Online since September 2007
Authors Alton B. Horsfall, Ming Hung Weng, Rajat Mahapatra, Nicolas G. Wright
Keywords Barrier Height, High-k, Sensor, Trap Assisted Conduction
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We present the variation of trap assisted conduction current through a dielectric stack comprising TiO2 and SiO2 on SiC as a function of both temperature and hydrogen gas concentration. We show that the current can be modeled by the use of a single barrier height across the temperature range of interest (>300oC ambient). Upon exposure to hydrogen gas, this barrier height is reduced from 0.405 to 0.325eV, whilst the density of traps in the bulk of the TiO2 remains unaffected. We conclude that the formation of a charge dipole layer under the palladium contact is responsible for this change in barrier height, as has been observed in Schottky diode sensor structures. Further, sensing the gas concentration by monitoring of the trap assisted conduction current appears not to be influenced by the existence of interfacial traps, offering the chance to fabricate low drift sensors for deployment in extreme environments.