DocumentCode :
2314042
Title :
Interface states in high temperature SiC gas sensing
Author :
Ghosh, Ruby N. ; Tobias, Peter ; Ejakov, Sally G. ; Golding, Brage
Author_Institution :
Center for Sensor Mater. Phys. & Astron. Building, Michigan State Univ., East Lansing, MI, USA
Volume :
2
fYear :
2002
fDate :
2002
Firstpage :
1120
Abstract :
Silicon carbide based metal-oxide-semiconductor (MOS) devices are attractive for gas sensing in harsh, high temperature environments. The response of catalytic gate SiC sensors to hydrogen-containing species has been assumed to be due to the formation of a dipole layer at the metal/oxide interface which gives rise to a voltage translation of the high frequency capacitance voltage (C-V) curve. We have discovered that high temperature (800 K) exposure to hydrogen results in (i) a flat band voltage occurring at a more negative bias than in oxygen and (ii) the transition from accumulation (high capacitance) to inversion (low capacitance) occurring over a relatively narrow voltage range. In oxygen, this transition is broadened indicating the creation of a large number of interface states. We interpret these results as arising from two independent phenomena - a chemically induced shift in the metal/semiconductor work function difference and the passivation/creation of charged states at the SiO2/SiC interface. MIS capacitance sensors typically operate in constant capacitance mode. These results. affect sensor sensitivity since the slope of the C-V curve changes dramatically with gas exposure.
Keywords :
MIS devices; capacitive sensors; gas sensors; interface states; inversion layers; silicon compounds; wide band gap semiconductors; 800 K; MOS devices; SiC; SiO2-SiC; capacitance sensors; catalytic gate; flat band voltage; high frequency capacitance voltage curve; high temperature gas sensing; interface states; inversion; metal/semiconductor work function difference; sensor sensitivity; voltage translation; Capacitance; Capacitance-voltage characteristics; Capacitive sensors; Chemical sensors; Frequency; Interface states; Sensor phenomena and characterization; Silicon carbide; Temperature sensors; Voltage;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Sensors, 2002. Proceedings of IEEE
Print_ISBN :
0-7803-7454-1
Type :
conf
DOI :
10.1109/ICSENS.2002.1037271
Filename :
1037271
Link To Document :
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