# Characterization and Variable Temperature Modeling of SiC MOSFET

## Abstract

Silicon power semiconductor device is difficult to meet the requirements of high temperature, high pressure and high frequency. Among them, the MOSFET which has the fast switch speed and the simple driving circuit, become the most popular object in SiC power electronic devices. In this paper, we choose the C2M0160120D chip of CREE company, establishing a complete model. And the static characteristics of SiC MOSFET under different temperature points are simulated. The switching characteristics of SiC MOSFET under different driving resistances are analyzed and compared with the experimental results, and the accuracy of the model is verified in this paper.

## Keywords

SiC MOSFET Simulation model Pspice Characteristic analysis## 1 Introduction

Si and GaAs, as the representative of the traditional semiconductor devices, can only work under 200 °C, and they can’t meet the new requirements of the development of modern electronic technology [1]. Since 1990s, with the outstanding performance advantages of band gap, breakdown field strength, thermal conductivity and saturation electron drift rate, the third generation wide band gap semiconductor material, represented by SiC and GaN, have become the research focus. At present, SiC MOSFETs have a very good application in the civil power substation and transmission field, the aerospace field, and the new energy field, such as PV inverter, hybrid/electric vehicles, rail vehicles, wind power [2].

With the wide use of SiC MOSFET, it is very important to use a model of the device to evaluate performance. Therefore, obtaining a precise and concise model is the key to simulate exactly of the device characteristics. The MOSFET device model can be divided into physical model and equivalent circuit model [3]. According to the structure diagram of the SiC MOSFET, the circuit schematic diagram and the physical equations of the model, a SiC MOSFET model based on the physical level was established in Ref. [4]. However, this method has a large amount of calculation. It is suitable for the research at the physical level and the analysis of the intrinsic characteristics of the device, but industrial applications. Taking SiC MOSFET CMF20120D chip of CREE company as an example, a variable temperature parameter PSpice model was built in Ref. [5]. The model was tested under different voltage, current and temperature conditions. It was turned out that the model was accurate and had a high reference value [6, 7, 8]. But the way, modeling of temperature controlled voltage source, is very complex and easy to make mistakes. In this paper, we use ABM (Analog Behavioral Modeling) simulation behavior model to improve the modeling method. Gate-drain capacitance *C*_{GD} is an important factor to affect the switching characteristic of SiC MOSFET, and the method in Ref. [6] has a poor accuracy. In this paper, based on the establishment of the SiC MOSFET model of MOS3, we make a thorough inquiry of modeling *C*_{GD.}

## 2 Variable Temperature Modeling of SiC MOSFET

*E*TEMP, is employed to describe the static characteristics of SiC MOSFET.

*C*GD and

*C*GS are used to describe the dynamic characteristics.

### 2.1 Temperature Compensation Modeling of on-State Resistance

*R*

_{ds}. From the datasheet of C2M0160120D, we can know that the value of

*R*

_{ds}increases with temperature. To simplify the modeling process, We combine the drain and source resistance into

*R*

_{ds(on)}, and we use the second-order fit method for its mathematical treatment

*R*

_{ds(on)}(

*T*

_{25}) is the typical

*R*

_{ds(on)}value at 25 °C, we take 160 mΩ,

*T*is the temperature point in simulations,

*TC*

_{1}and

*TC*

_{2}are fitting coefficients.

Place the temperature compensation resistor in the circuit, and test the *R*_{ds(on)} of SiC MOSFET with the condition of *U*_{GS} = 20 V,*I*_{D} = 10A.

### 2.2 Modeling of Temperature Control Voltage Source

In this paper, ABM (Analog Behavioral Modeling) is used to model the temperature control voltage source. ABM is an extension of the controlled source. It calls mathematical formulas or look-up tables to describe the device, without the need to design specific circuit [9].

*E*

_{TEMP}is used to compensate for the change of threshold voltage caused by temperature change. It proposed in Ref. [10]. Simple linear fitting can’t perfectly represent the curve of Threshold Voltage vs. Temperature. So we use the three order function and three order fitting to the

*E*

_{TEMP}modeling,

*T*is the temperature point in simulations,

*VT*1,

*VT*2 and

*VT*3 are fitting coefficients. The ABM model used in this paper is simpler, and the improved formula is

### 2.3 Modeling of Gate-Source Capacitance

The capacitance between several poles affect the switching characteristics of SiC MOSFET. It is almost independent of temperature, but sensitive to voltage parameters. So, in this paper, temperature factors will not be considered, and mainly discuss the modeling of *C*_{GD} which has a significant influence on the switching characteristics of the device. Two modeling methods of *C*_{GD} will be explored in this paper.

#### 2.3.1 Sub Circuit Modeling Method

*C*

_{GD.}We can reasonably configure the parameters of two diodes to accurately simulate the changes in capacitance.

When the device is in off-state, *U*_{GD} < 0, *D*_{GD1} and *D*_{GD2,} in series, are used to describe the changes in *C*_{GD}. When the device is in the on-state, *U*_{GD} > 0, fixed capacitance *CGD*_{MAX} = *C*_{GD}. In this way, the sub circuit can accurately describe the nonlinear variable capacitance *C*_{GD.}

The waveform of the capacitance with voltage is shown in Fig. 3b. In the simulation process, the running speed is slow and the simulation curve is not easy to converge, which is prone to error. The capacitance value increases with the *U*_{GD} value, which is far from the actual one. Diode parameters can only be set by trial and error, which has poor accuracy.

#### 2.3.2 Descriptive Statement Modeling Method

*C*

_{GD}is nonlinear before the device is fully turn on, and it is a fixed value after the opening. It needs to describe the nonlinear variation of the capacitance value, which is expressed in

*C*

_{g}. Because measure capacitance directly is hard, referring to the formula (6), when d

*U*

_{GD}/d

*t*is linear to 1, the

*i*

_{g}−

*t*change can be used to replace the description of

*C*

_{g}−

*U*

_{GD}change.

*C*

_{g}only works when the

*C*

_{GD}is less than zero. We can get the fitting function (8).

According to the fitting formula and using statement modeling method of Model Editor, we can build *C*_{GD} sub circuit module.

As is shown,when *U*_{GD} < 0, the capacitance value decreases with the increase of voltage. When *U*_{GD} > 0, the capacitance value keeps constant. Therefore, this model can accurately simulate the nonlinear capacitance *C*_{GD} in SiC MOSFET.

The above two models respectively use diode and voltage control current source to complete the modeling of *C*_{GD}. There is a great deal of uncertainty in parameter setting by using diode modeling. So we select the second method by using VCCS to the modeling in this paper.

## 3 Characteristics Verification

### 3.1 Static Characteristics Verification

### 3.2 Dynamic Characteristics Verification

The test circuit uses a double pulse gate drive mode. The drive voltage is −5/19 V. The drain-source voltage is 600 V. The load inductance is 5 Ω, 10 Ω, 20 Ω, 30 Ω. Observe the on-state and off-state simulation waveform of SiC MOSFET on different drive resistances, and compare to the experimental result.

Due to the fast switching speed of the SiC MOSFET, it requires wider band gap of current and voltage probes. We use the 100 MHz bandwidth voltage probe and 120 MHz current probe in this paper.

- (1)The driving resistance is set to 5 Ω. The moment the device turn on (Fig. 8)

Above the pictures, the prior is simulation waveform. The latter is the experimental waveform. The blue line represents the change in drain-source voltage with time, and the red line represents the change in drain current with time.

From the simulation and experimentation results can be seen, the model built in this paper can fit the waveforms of current and voltage in the turn-on and turn-off time of SiC MOSFET C2M0160120D.

## 4 Conclusion

This paper focuses on the establishment of the simulation model based on SiC MOSFET C2M0160120D in Pspice. When modeling temperature-controlled voltage sources, we use the ABM module to simplify the modeling process. On the basis of the previous modeling methods, the model is further improved in this paper. Test the static characteristics of the model at different temperatures, the simulation results are in good agreement with the data provided in datasheet. Two models respectively use diode and voltage control current source to complete the modeling of *C*_{GD}. After the comparison, we select the second method by using VCCS to the modeling in this paper. Build the test circuit by the dynamic model and test switching characteristics under different driving resistance. Compare the simulation result with experiment. It verifies the correctness of the dynamic model.

## Notes

### Acknowledgements

This work was supported by the Fundamental Research Funds for the Central Universities of China (No. E16JB00160/2016JBM062/2016JBM058) and The National Key Research and Development Program of China (2016YFB1200504-C-02).

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