Using a First Principles Coulomb Scattering Mobility Model for 4H-SiC MOSFET Device Simulation

A physics based device simulator for detailed numerical analysis of 4H-SiC MOSFETs with an advanced mobility model that accounts for the effects of bulk and surface phonons, surface roughness and Coulomb scattering by occupied interface traps and fixed oxide charges, has been developed. A first principles quasi-2D Coulomb scattering mobility model specifically for SiC MOSFETs has been formulated. Using this, we have been able to extract the interface trap density of states profile for 4H-SiC MOSFETs and have shown that at room temperature, Coulomb scattering controls the total mobility close to the interface. High temperature, low field simulations and experiments show that the current increases with increase in temperature. The effect of Coulomb scattering decreases with increase in temperature causing an increase in the total mobility near the interface at low gate voltages.

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SiC MOSFET Channel Mobility Dependence on Substrate Doping and Temperature Considering High Density of Interface Traps

Materials Science Forum ◽

10.4028/www.scientific.net/msf.556-557.835 ◽

2007 ◽

Vol 556-557 ◽

pp. 835-838 ◽

Cited By ~ 3

Author(s):

Amador Pérez-Tomás ◽

Michael R. Jennings ◽

Philip A. Mawby ◽

James A. Covington ◽

Phillippe Godignon ◽

...

Keyword(s):

Degradation Mechanism ◽

Mobility Model ◽

Effect Of Temperature ◽

Coulomb Scattering ◽

Interface Traps ◽

Channel Mobility ◽

Inversion Channel ◽

Scattering Effects ◽

Charge Concentration ◽

Substrate Doping

In prior work we have proposed a mobility model for describing the mobility degradation observed in SiC MOSFET devices, suitable for being implemented into a commercial simulator, including Coulomb scattering effects at interface traps. In this paper, the effect of temperature and doping on the channel mobility has been modelled. The computation results suggest that the Coulomb scattering at charged interface traps is the dominant degradation mechanism. Simulations also show that a temperature increase implies an improvement in field-effect mobility since the inversion channel concentration increases and the trapped charge is reduced due to bandgap narrowing. In contrast, increasing the substrate impurity concentration further degrades the fieldeffect mobility since the inversion charge concentration decreases for a given gate bias. We have good agreement between the computational results and experimental mobility measurements.

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A unified mobility model for device simulation—II. Temperature dependence of carrier mobility and life-time

Microelectronics Reliability ◽

10.1016/0026-2714(93)90166-v ◽

1993 ◽

Vol 33 (9) ◽

pp. 1424

Keyword(s):

Temperature Dependence ◽

Carrier Mobility ◽

Device Simulation ◽

Life Time ◽

Mobility Model

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A semi-empirical model for electron mobility at the SiC/SiO2 interface

MRS Proceedings ◽

10.1557/proc-742-k4.8 ◽

2002 ◽

Vol 742 ◽

Cited By ~ 5

Author(s):

Nelson S. Saks

Keyword(s):

Surface Roughness ◽

Empirical Model ◽

Gate Voltage ◽

Mobility Model ◽

Coulomb Scattering ◽

Mos Devices ◽

Surface Roughness Scattering ◽

Hall Effect Measurements ◽

Semi Empirical ◽

Mos Device

ABSTRACTThe mobility of electrons in inversion layers at SiC/SiO2 interfaces μinv has been characterized in 4H- and 6H-SiC using Hall effect measurements. In order to understand the cause of the low mobilities typically observed in SiC MOS devices, a semi-empirical mobility model has been developed based on a previous model for silicon inversion layers. Using this model, two scattering mechanisms, surface phonon and Coulomb scattering from high densities of electrons trapped at the SiC/SiO2 interface, are found to account reasonably well for the behavior of the mobility. The model employs a changing density of trapped electrons as a function of gate voltage to accurately model Coulomb scattering. Surprisingly, evidence of surface roughness scattering is not observed in any SiC MOS device.

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