Interface states in high-temperature gas sensors based on silicon carbide

Tobias, Peter S.; Golding, B.; Ghosh, Ruby N.

doi:10.1109/jsen.2003.817154

“…Over this temperature range, the response in capacitance could be affected by interface states activation at high temperature, this leading to the appearance of a two-peak response and to a decreasing of the response in capacitance. A possible explanation of this phenomenon could be the higher time response of interface states over 450 K [40]. As one can see in the inset of Fig.…”

Section: Sic-based Mos Capacitor Hydrogen Sensormentioning

confidence: 86%

A new 4H-SiC hydrogen sensor with oxide ramp termination

Pascu

¹

,

Kusko

²

,

Crǎciunoiu

³

et al. 2016

Materials Science in Semiconductor Processing

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“…At temperatures above 700 K the diffusion time for hydrogen through 100 nm of Pt and 50 nm of SiO 2 is less than 5 µs [Katsuta 1979] and 0.5 ms [Beadle 1985] respectively. We have previously demonstrated via in-situ C-V spectroscopy of Pt/SiO 2 /SiC sensors at 800 K that oxidizing species affect the electronic properties of both the metal/oxide and oxide/semiconductor interfaces [Tobias 2003A]. Fig.…”

Section: List(s) Of Graphical Materialsmentioning

confidence: 99%

Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions

Ghosh¹,

Tobias²,

Tobin³

2006

0

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A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen-containing species in chemically reactive, high temperature environments. For fast and stable sensor response measurements, a gate activation process is required. Activation of all sensors took place by switching back and forth between oxidizing (1.0 % oxygen in nitrogen) and reducing (10 % hydrogen in nitrogen) gases for several hours at a sensor temperature ≥620 °C. All 52 devices on the sensor chip were activated simultaneously by flooding the entire chip with gas. The effects of activation on surface morphology and structure of Pt gates before and after activation were investigated. The optical images obtained from Pt gates demonstrated a clear transition from a smooth and shiny surface to a grainy and cloudy surface morphology. XRD scans collected from Pt gates suggest the presence of an amorphous layer and species other than Pt (111) after activation.The reliability of the gate insulator of our metal-oxide-SiC sensors for long-term device operation at 630 °C was studied. We find that the dielectric is stable against breakdown due to electron injection from the substrate with gate leakage current densities as low at 5nA/cm 2 at 630 °C. We also designed and constructed a new nano-reactor capable of high gas flow rates at elevated pressure. Our reactor, which is a miniature version of an industrial reactor, is designed to heat the flowing gas up to 700 °C.Measurements in ultrahigh vacuum demonstrated that hydrogen sulfide readily deposits sulfur on the gate surface, even at the very high hydrogen/hydrogen sulfide ratios (10 3 -10 5 ) expected in applications. Once deposited, the sulfur adversely affects sensor response, and could not be removed by exposure to hydrogen at the temperatures and pressures accessible in the ultrahigh vacuum experiments. Oxygen exposures, however, were very effective at removing sulfur, and the device performance after sulfur removal was indistinguishable from performance before exposure to H 2 S.3

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“…At temperatures above 700 K the diffusion time for hydrogen through 100 nm of Pt and 50 nm of SiO 2 is less than 5 µs [Katsuta 1979] and 0.5 ms [Beadle 1985] respectively. We have previously demonstrated via in-situ C-V spectroscopy of Pt/SiO 2 /SiC sensors at 800 K that oxidizing species affect the electronic properties of both the metal/oxide and oxide/semiconductor interfaces [Tobias 2003A]. …”

Section: List(s) Of Graphical Materialsmentioning

confidence: 99%

Silicon Carbide Micro-Devices for Combustion Gas Sensing Under Harsh Conditions

Ghosh¹,

Tobias²,

Tobin³

2004

View full text Add to dashboard Cite

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen containing species in chemically reactive, high temperature environments. For these capacitive sensors we have determined that the optimum sensor operating point in terms of sensor lifetime and response time is at midgap. Detailed measurements of the oxide leakage current as a function of temperature were performed to investigate the high temperature reliability of the devices. In addition, robust metallization and electrical contacting techniques have been developed for device operation at elevated temperatures. To characterize the time response of the sensor responses in the millisecond range, a conceptually new apparatus has been built. Using laser induced fluorescence imaging techniques we have shown that that the gas underneath the sensor can be completely exchanged with a time constant under 1 millisecond. Ultrahigh vacuum studies of the surface chemistry of the platinum gate have shown that sensor deactivation by adsorbed sulfur is a possible problem. Investigations on the chemical removal of sulfur by catalytic oxidation or reduction are continuing.3

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Interface states in high-temperature gas sensors based on silicon carbide

Cited by 44 publications

References 16 publications

A new 4H-SiC hydrogen sensor with oxide ramp termination

A new 4H-SiC hydrogen sensor with oxide ramp termination

Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions

Silicon Carbide Micro-Devices for Combustion Gas Sensing Under Harsh Conditions

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