Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

Abstract

We report on the electrical properties of Al2O3 films grown on 4H-SiC by successive thermal oxidation of thin Al layers at low temperatures (200°C - 300°C). MOS capacitors made using these films contain lower density of interface traps, are more immune to electron injection and exhibit higher breakdown field (5MV/cm) than Al2O3 films grown by atomic layer deposition (ALD) or rapid thermal processing (RTP). Furthermore, the interface state density is significantly lower than in MOS capacitors with nitrided thermal silicon dioxide, grown in N2O, serving as the gate dielectric. Deposition of an additional SiO2 film on the top of the Al2O3 layer increases the breakdown voltage of the MOS capacitors while maintaining low density of interface traps. We examine the origin of negative charges frequently encountered in Al2O3 films grown on SiC and find that these charges consist of trapped electrons which can be released from the Al2O3 layer by depletion bias stress and ultraviolet light exposure. This electron trapping needs to be reduced if Al2O3 is to be used as a gate dielectric in SiC MOS technology.

High Performance Single Crystalline Diamond Normally-Off Field Effect Transistors

“…Based on the thickness of 5.0 nm of the alumina layer, the permittivity is calculated to be 2.7, which is at the same level with the results of Wang et al [15] and Hirama et al [18]. However, this value is lower than the reported value of 6∼9 [23]- [25]. The alumina in this study is formed by oxidizing aluminum at low temperature on hotplate in the air.…”

Electrode and electrolyte configurations for low frequency motion energy harvesting based on reverse electrowetting

“…Since there is no restriction to breakdown voltage, dielectric thickness could be reduced to just a few tens of nanometer, thereby increasing the current density by over fifty percent, assuming the proportionality holds. To put it into perspective, the breakdown strength of Al 2 O 3 thin film dielectrics deposited with e-beam evaporation has been shown to be ~ 0.5–0.8 V/nm 37 , implying that if even just a few mV of DC offset were applied, less than 1 nm of Al 2 O 3 would be needed for a REWOD energy harvester. By using physical vapor deposition (PVD) systems such as E-beam evaporation and sputtering, and atomic layer deposition (ALD), conformal and uniform deposition thickness could be very well controlled to a few tens of nanometer.…”

Improving the Performance of Gas Sensor Systems with Advanced Data Evaluation, Operation, and Calibration Methods

“…Dynamic effects appear with UV irradiation, causing a general upwards trend over time especially at positive gate bias. A tentative explanation which fits the direction of the drift is the removal of trapped electrons from the oxide which has been reported to happen only under UV light for Al 2 O 3 as gate insulator [258]. Alternatively, the additional electron-hole pairs in the channel could increase the time constant until a new charge carrier equilibrium in the channel has been reached, which is accelerated through higher temperatures.…”

“…Little research has been directed to exploring the effects of light irradiation on field-effect gas sensors. Most of these works focus on 1D gate materials [256], [257] and one mentions UV irradiation to remove trapped electrons from an Al 2 O 3 gate insulator [258]. The lack of motivation for this kind of research is not very surprising given that MOS sensors promise much larger effects upon irradiation due to their semiconducting nature.…”