sic schottkymodel

3558 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 5, SEPTEMBER/OCTOBER 2014

Parameter Extraction Procedure for a Physics-BasedPower SiC Schottky Diode Model

Ruiyun Fu, Alexander E. Grekov, Kang Peng, and Enrico Santi, Senior Member, IEEE

Abstract—A detailed parameter extraction procedure for asimple physics-based power silicon carbide (SiC) Schottky diodemodel is presented. The developed procedure includes the extrac-tion of carrier concentration, active area, and thickness of thedrift region, which are needed in the power Schottky diode model.The main advantage is that the developed procedure does notrequire any knowledge of device fabrication, which is usually notavailable to circuit designers. The only measurements required forthe parameter extraction are simple static I–V characterizationand C–V measurements. Furthermore, the physics-based SiCSchottky diode model whose parameters are extracted by theproposed procedure includes temperature dependences and is gen-erally applicable to SiC Schottky diodes. The procedure is demon-strated for five Schottky diodes from two different manufacturershaving the following ratings: 600 V/50 A, 1.2 kV/3 A, 1.2 kV/7 A,1.2 kV/20 A, and 600 V/4 A.

Index Terms—Parameter extraction procedure, physics-basedmodel, Schottky diode, silicon carbide (SiC).

I. INTRODUCTION

S ILICON CARBIDE (SiC) is one of the most promis-ing semiconductor materials for high-voltage, high-speed,

and low-loss power switching applications. Excellent electricalproperties of SiC material, such as wider bandgap (3.26 eV),higher thermal conductivity (4.9 W/cm · K), and higher criticalbreakdown electric field (2.2× 106 V/cm, which is almost tentimes larger than Si), make it a very attractive semiconductormaterial for power switching devices with capabilities that aresuperior to those of devices based on silicon technology [1]–[3].

Owing to recent progress in SiC technology, SiC Schottkydiodes are now commercially available from several companiessuch as Cree, GeneSiC, and Infineon. Since power devicesplay a key role in power electronics applications, accurate andcomputationally efficient power device models are required forpower electronics designers to evaluate the performance ofSiC Schottky diodes in different applications. So far, severalmodels have been developed for SiC Schottky diodes [4]–[10].

Manuscript received May 16, 2013; revised October 25, 2013; acceptedJanuary 1, 2014. Date of publication February 5, 2014; date of current versionSeptember 16, 2014. Paper 2013-PEDCC-282.R1, presented at the 2013 IEEEApplied Power Electronics Conference and Exposition, Long Beach, CA, USA,March 17–21, and approved for publication in the IEEE TRANSACTIONS ON

INDUSTRY APPLICATIONS by the Power Electronic Devices and ComponentsCommittee of the IEEE Industry Applications Society. This work was sup-ported by the Office of Naval Research under Grant N00014-08-1-0080.

The authors are with the Department of Electrical Engineering, Universityof South Carolina, Columbia, SC 29208 USA (e-mail: [email protected];[email protected]; [email protected]; [email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIA.2014.2304617

However, these models typically use either some fitting param-eters that have no physical meaning or physical parameters thatare difficult to extract from experimental measurements. Theelectrothermal macromodel in [4] is a standard piecewise linearbehavioral model. The model is simple, and the parametersare easy to extract but have no physical meaning. The modelin [5] is a physics-based model implemented in the circuitsimulator Spice. The main feature of this model is that it takesinto account electrothermal (including self-heating) effects, butit uses a few fitting parameters. The model in [6] is a simplephysics-based model for system modeling. The parameters inthis model are typical values from the literature. The physics-based numerical model in [7] is based on the solution of thesemiconductor transport equations from the surface to the bulkregion. This model is accurate but complicated. The model in[8] is a physics-based temperature-dependent model developedin the Saber circuit simulator for Schottky merged PiN Schottky(MPS) and PiN power diodes. Although this model can be usedin a wide range of test circuit conditions and for different typesof devices, it needs a few parameters that are unknown to thedesigners. The parameter extraction sequence for this model isgiven in [9]. Reference [10] shows an accurate analytical modeland complete parameter extraction of the forward characteris-tics of the Ni/6H-SiC Schottky barrier diodes (SBDs) for low-and high-level current densities using MEDICI program. Thismodel takes into account high-level injection effects and thecurrent dependence of the series resistance. The parameters areextracted using the extraction program EXTRDEV.

In conclusion, some of the proposed physics-based modelsprovide good accuracy but usually need several device param-eters (which are usually unknown to designers) to implementthe model for a specific device, and sometimes, the modelitself is overly complicated and requires long simulation time.The SiC Schottky diode model presented in this paper is asimple model that represents the basic physics behavior of thedevice. This model has been implemented in PSPICE, a productof CADENCE Corporation. The detailed parameter extractionprocedure introduced here does not require any knowledge ofdevice fabrication. The only measurements required for theparameter extraction are simple static I–V characterization andC–V measurement. These measurements are typically givenin the datasheets for commercial devices, so the parameterextraction procedure can be performed based on datasheetsonly. The extraction procedure is applied to several SiC powerdiodes from different manufacturers. Results will be presentedfor the following:

1) a 600-V 50-A Schottky diode from GeneSiC Inc.;2) a 1200-V 3-A Schottky diode from GeneSiC Inc.;

0093-9994 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

FU et al.: PARAMETER EXTRACTION PROCEDURE FOR A PHYSICS-BASED POWER SiC SCHOTTKY DIODE MODEL 3559

Fig. 1. (a) Structure of power Schottky diode. (b) Simple physics-basedSchottky diode model.

3) a 1200-V 7-A Schottky diode from GeneSiC Inc.;4) a 1200-V 20-A Schottky diode from Cree Inc.;5) a 600-V 4-A punch-through (PT) Schottky diode from

Cree Inc.In Section II, the proposed physics-based model is intro-

duced. The parameter extraction procedure is described inSection III for non-PT (NPT) Schottky diodes, and the mod-ifications needed for PT devices are described in Section IV.In Section V, experimental validation is presented both understatic conditions and under inductive switching dynamic op-eration. Section VI presents a discussion of the results, andSection VII presents the conclusion.

II. SIMPLE PHYSICS-BASED SCHOTTKY DIODE MODEL

The structure of the power SiC Schottky diode with themetal–semiconductor Schottky contact is shown in Fig. 1(a).The simple physics-based Schottky diode model [shown inFig. 1(b)] is developed by using thermionic emission theory,which describes the dominant carrier transport mechanismin Schottky power rectifiers [11]. The model is comprisedof three elements: a voltage-controlled current source ID, atemperature-dependent drift region resistance RD, and a non-linear capacitance Cr.

In a SiC Schottky diode, the thermionic emission processdominates in the current transport across the metal semiconduc-tor contact. Under forward bias condition, the current across theSchottky barrier is given by

ID =AA∗T 2e−(qϕb/kT )[e(qVD/nkT ) − 1

]= IS

[e(qVD/nkT ) − 1

](1)

where IS is the saturation current density, A is the active areaof the diode, A∗ is the Richardson’s constant, ϕb is the barrierheight between the metal and N-type semiconductor, n is theideality factor, T is the absolute temperature, q is the electroncharge, k is the Boltzmann’s constant, and VD is the voltagedrop across the Schottky barrier.

TABLE ISCHOTTKY DIODE MODEL PARAMETERS

The series drift region resistance RD is given by

RD =LD

qμD(T )ND ×A(2)

where ND is the drift region carrier concentration, LD is thethickness of the drift region, and μD(T ) is the temperature-dependent electron mobility. Following [12], the temperature-dependent mobility can be expressed as

μD(T ) = μ300

(T

300

)−x

(3)

where μ300 is the carrier mobility at room temperature T =300 K.

Since Schottky diode is a majority carrier device, there isno minority carrier injection in the drift region during forwardconduction and no storage effect at diode turn-off. Conse-quently, the depletion layer capacitance determines the diode’sswitching behavior. When a reverse bias voltage VR is appliedto the Schottky diode, a depletion region forms under the metalsemiconductor interface, and the depletion layer thickness Wr

can be calculated as [11]

Wr =

√2ε0εrqND

(VR + Vbi) ≈√

2ε0εrqND

(VR + ϕb). (4)

Because all of the applied bias voltage is supported in thesemiconductor, this depletion width can be used to calculatethe nonlinear capacitance Cr of the Schottky diode as

Cr =ε0εrA

Wr= A×

√qNDε0εr2(VR + ϕb)

. (5)

The diode model described by (1)–(5) is implemented inCadence Spice using the behavioral modeling source capabilityof Spice. The nonlinear capacitor is implemented as a nonlinearvoltage-controlled current source. Since the capacitor current isrelated to the voltage derivative, the capacitor implementationmay suffer from high-frequency noise problems. The use of abandwidth-limited derivative is recommended.

The complete list of the needed parameters for the considereddevice model is given in Table I.

The proposed model neglects a number of physical effects.This is done for simplicity and because a more complex de-vice model capturing these effects would have a number ofparameters that cannot be easily extracted through measure-ments. Among the neglected effects are contact resistances andsubstrate resistance. Several effects related to reverse leakagecurrent are also neglected, such as Schottky barrier lowering


and avalanche multiplication. Also neglected is the fact thatmany commercially available SiC diodes are not pure Schottkydiodes but junction barrier Schottky (JBS) also known as MPS.Device manufacturers use this approach to reduce leakage cur-rent and to improve reverse blocking voltage capability. Underextreme conditions such as very high temperature > 250 ◦C andhigh current density, the p-n junction in MPS and JBS diodesalso serves for improvement of the pulse current capability ofSchottky diodes. Since the proposed model does not considerthe effect of the p-n junction of the JBS structure on forwardconduction at extreme conditions such as very high temperatureand large forward bias, the validity of the proposed model islimited to the nominal range of operation (< 200 ◦C).

The effect of incomplete ionization can be neglected forSBD since it consists of a metal and a semiconductor withvery low doping concentration (blocking region). The energylevel for nitrogen—typical residual donor in low-doped SiC—issituated very close to the conduction band minimum (0.1 eV),and therefore, ionization of nitrogen dopant in 4H-SiC occurswith high rate (> 99%) even at room temperature. It is truethat the effect of incomplete doping ionization is significantfor devices with active region with moderate and high dopingconcentrations (p-n junction, BJT). Since the proposed modeldoes not consider the effect of the p-n junction of the JBS orMPS structure on forward conduction at extreme conditionssuch as very high temperature and large forward bias, the effectof incomplete ionization of dopant atoms is not included.

III. PARAMETER EXTRACTION PROCEDURE

The proposed parameter extraction procedure is equally ap-plicable to NPT and PT Schottky diodes. This section describesthe NPT case, and the next section describes the modificationsneeded to apply the method to PT devices.

The parameter extraction approach discussed in this sectionis based on the assumption that the Schottky diode is NPT andthat the carrier mobility at room temperature μ300 is known.The theoretical value of mobility for low-doped 4H-SiC ma-terial at room temperature is ∼980 cm2/V · s [13]. From pastexperience in characterization of SiC MOSFETs and JFETs[12], it was found that the actual room temperature electronmobility is smaller than theoretical value and is in the range of400–600 cm2/V · s. Therefore, a value of μ300 = 500 cm2/V ·s is used in this work.

With an NPT Schottky diode structure shown in Fig. 2(a), it isassumed that the low-doped drift region is completely depletedwhen the breakdown reverse voltage is applied. In other words,the breakdown voltage coincides with the PT point. Underthis assumption, the breakdown voltage of the device can becalculated by calculating the triangular area under the electricfield profile shown in Fig. 2(b).

A. Drift Region Parameters ND, LD, and A

To extract the drift region parameters ND, LD, and A, thestatic I–V characterization and C–V measurements of theSchottky diode are needed. The I–V measurements in this workare performed using a Tektronix 371 A power curve tracer, andthe C–V measurements are performed using a Keithley 590 CV

Fig. 2. (a) Structure of NPT Schottky diode. (b) Electric field distributionalong the drift region.

Fig. 3. I–V characteristics from 25 ◦C to 175◦ for the 600-V 50-A GeneSiCSchottky diode.

analyzer. The value of series resistance RD can be estimatedfrom the slope of the I–V characteristics at high currents, asshown in Fig. 3 for the 600-V 50-A GeneSiC Schottky diode.

Therefore, the slope S1 of the I–V characteristics at a certaintemperature can be calculated from

S1 =1

RD=

qμDND ·ALD

. (6)

Besides the I–V characteristics of the Schottky diode, C–Vmeasurement is needed for the extraction procedure. Fig. 4shows the C–V characteristics of the 600-V 50-A GeneSiCSchottky diode at measurement frequency f = 1 MHz.

From (5), one obtains

1

C2r

=2

A2qNDε0εr(VR + Vbi). (7)

Therefore, the slope S2 of 1/C2r versus VR is given by

S2 =2

A2qNDε0εr. (8)


Fig. 4. C–V measurement of the 600-V 50-A GeneSiC Schottky diode.(a) Cr versus Vr . (b) 1/C2

r versus Vr .

Based on the assumption of a triangular electric field distribu-tion shown in Fig. 2(b), one can calculate the device thicknessbased on the breakdown voltage VB as

LD =

√2ε0εrVB

qND. (9)

Substituting (9) into (6) and squaring both sides, one obtains

S21 =

q3N3Dμ2

DA2

2ε0εrVB. (10)

Rewriting (8) to get an expression for A2 and then substi-tuting it into (10), an expression for carrier concentration as afunction of breakdown voltage and slopes S1 and S2 can beobtained

ND =S1ε0εr

√VBS2

qμD. (11)

This is the first parameter extraction equation. Then, sub-stituting the value for ND found using (11) back into (8), theactive area A can be calculated as

A =

√2

S2qNDε0εr. (12)

For a specific device with known breakdown voltage, by cap-turing the I–V characteristics and C–V measurements of theSchottky diode at room temperature, the drift region parametersND, LD, and A can be extracted using (11), (9), and (12),respectively. The breakdown voltage can be either estimatedfrom the datasheets or measured with a power curve tracer.

B. Barrier Height ϕb and Temperature Coefficient x

The barrier height ϕb is defined as the potential differencebetween the metal Fermi level and the majority carrier bandedge of the semiconductor. Barrier height of Schottky diodesdepends on the fabrication process and semiconductor material.Any surface contamination introduced during the diode fabri-

cation process can affect the barrier height of the diodes. Thebarrier height ϕb can be extracted using the following steps.

Rewrite (1) for V � kT/q as

ln(I) = ln(Is) +qV

nkT. (13)

From the semilog plot of ln(I) versus V , the intercept of thecurrent axis at V = 0 gives the saturation current Is. The barrierheight ϕb can be expressed as

ϕb =kT

qln

(AA∗T 2

Is

). (14)

Based on the assumption that the carrier mobility at roomtemperature μ300 is known (500 cm2/V · s is used in thiswork), the temperature coefficient of carrier mobility x can becalculated by using the value of mobility extracted from staticcharacteristics at an elevated temperature T1 [12]

x =ln(μ(T1)/μ300

)ln(T1/300)

. (15)

For 4H-SiC, the theoretical value of Richardson’s constantA∗ is 146 A · cm−2 · K−2 [6]. For simplicity, the ideality factorn is assumed to be unity.

In conclusion, the parameter extraction procedure consists ofthe following steps.

1) Assume that the Richardson’s constant is A∗ = 146 A ·cm−2 · K−2, the ideality factor is n = 1, and the carriermobility at room temperature μ300 has a known value(500 cm2/V · s is used in this work).

2) Obtain slope S1 from the I–V characteristics and slopeS2 from the C–V measurement [see Figs. 3 and 4(b)].

3) Calculate the drift region parameters ND, LD, and A byusing (11), (9), and (12), respectively.

4) Extract barrier height ϕb from the I–V characteristics byusing (14).

5) Calculate the corresponding carrier mobility μ(T1) at oneelevated temperature T1. Mobility at elevated temperatureT1 is calculated using (6), since all other quantities in (6)are known, including the measured slope S1 at elevatedtemperatures and carrier concentration ND previouslyextracted from slope S1 at room temperature in step 3.

6) Extract the temperature coefficient x of carrier mobilityby using (15).

IV. MODIFICATIONS OF PARAMETER EXTRACTION

PROCEDURE FOR A PT SCHOTTKY DIODE

For a PT Schottky diode shown in Fig. 1(a), the parameterextraction procedure is quite similar to the NPT case describedpreviously. The only difference is that the voltage used tocalculate the drift region thickness LD is not the breakdownvoltage VB but the PT voltage VPT that totally depletes the driftregion. In PT operation, the C–V characteristic of the Schottkydiode is shown in Fig. 5. Once the drift region is totally depletedat voltage VPT, any further increase in applied voltage does notcause a decrease in the incremental capacitance Cr, which isconstant and equal to CPT and no longer dependent on reverse


Fig. 5. C–V characteristics of a PT Schottky diode.

bias. Using this feature, it is straightforward to establish fromthe C–V characteristic whether a Schottky diode operates inPT mode or not. Note that the C–V characteristic must bemeasured over an extended voltage range all the way to ratedblocking voltage.

When the depletion region just hits the N− /N+ interfaceat voltage VPT, the electric field profile along the drift region istriangular and is shown in Fig. 2(b). Therefore, the thickness ofthe drift region can be calculated using (16), which replaces (9)

LD =

√2ε0εrVPT

qND(16)

where VPT is the voltage totally depleting the drift region. Thisvoltage can be obtained from the diode C–V characteristic(see Fig. 5).

Therefore, the carrier concentration in drift region ND canbe rewritten as

ND =S1ε0εr

√VPTS2

qμD. (17)

The parameter extraction procedure for the PT case is iden-tical to the procedure for the NPT case given in Section III,except that step 3) is modified to the following.3) Calculate the drift region parameters ND, LD, and A by

using (17), (16), and (12), respectively.The nonlinear capacitance model in the simple Schottky

diode model needs to be modified: its value needs to have alower bound equal to the PT capacitance CPT at voltage VPT.

The I–V characteristics and C–V characteristics needed forthe extraction procedure can typically be found in the devicedatasheet provided by the manufacturer. In this paper, the PTparameter extraction procedure is applied to the 600-V 4-A PTSchottky diode C3 D04060A from Cree Inc. Since the Keithley590 C–V measurement setup available in our laboratory islimited to a maximum bias voltage of 100 V, the parameterextraction data are obtained from the datasheet. The actual I–Vand C–V data obtained by scanning the Cree datasheets usingthe Plot Digitizer software program are shown in Fig. 6.

V. VALIDATION OF PARAMETER EXTRACTION

PROCEDURE AND SCHOTTKY DIODE MODEL

The parameter extraction procedure is applied to severalSiC Schottky diodes: 600-V 50-A, 1200-V 3-A, and 1200-V7-A Schottky diodes from GeneSiC Inc., and a 1200-V 20-A

Fig. 6. Characteristics of 600-V/4-A PT Schottky diode scanned fromdatasheet. (a) I–V curves. (b) C–V curve.

TABLE IIEXTRACTED PARAMETERS

Schottky diode and a 600-V 4-A PT Schottky diode from CreeInc. Table II gives the extracted parameters of the five deviceswith the assumption that room temperature electron mobilityμ300 is 550 cm2/V · s. After all Schottky diode parametersare extracted, the model defined by (1), (2), and (5) can bevalidated. Fig. 7 shows the comparison of the simulated (dashedlines) I–V characteristics of SiC Schottky diodes based onextracted parameters, with experimental (solid lines) staticcharacteristics for temperatures from 25 ◦C to 175 ◦C. Thetemperature step is Δt = 50 ◦C. The simulated I–V curves arein fairly good agreement with the experimental results for thefive devices. Fig. 8 shows the comparison of simulated (dashedlines) with experimental C–V characteristics of SiC Schottkydiodes measured at frequency f = 1 MHz. Fig. 9 shows thecomparison of the corresponding curves of 1/C2

r versus reversevoltage Vr. Figs. 8 and 9 demonstrate that the simulated C–Vcurves have fairly good agreement with the experimental re-sults, which is very important for switching performance, evenif some discrepancy can be seen at low voltages.


Fig. 7. Comparison of simulated (dashed lines) with experimental (solid lines) static characteristics of SiC Schottky diodes measured at a temperature from 25 ◦Cto 175 ◦C. (a) GeneSiC 1200 V, 3 A. (b) GeneSiC 1200, 7 A. (c) Cree 1200 V, 20 A. (d) GeneSiC 600 V, 50 A. (e) Cree 600 V, 4 A (estimated from datasheet).

For a dynamic characteristic validation, a Double Pulse Testerwas built to perform inductive switching experiments on thesefive SiC Schottky diodes. The active device used for the exper-iment was a 1200-V 24-A n-channel SiC MOSFET from Cree,Inc., part number CMF10120D. Fig. 10 shows the correspond-ing inductive circuit used in the simulation, which includes var-ious parasitic inductances. The gate-to-source switching loopand drain-to-source switching loop parasitic inductances of thePCB layout are extracted by the 3-D inductance extraction pro-gram FastHenry, which uses partial element equivalent circuitmethod for magneto-quasistatic analysis of 3-D packages and

interconnects [14]. The simulation uses the MOSFET modelproposed in [15], which models the nonuniform current distri-bution in the JFET region by using a nonlinear controlled volt-age source and a resistance network. VDR is the voltage acrossthe Schottky diode, and ISCH denotes the current through thediode, which are both shown in the figure. Comparisons be-tween experimental and simulated results are shown in Fig. 11for inductive switching of the device GeneSiC 1200 V, 3 A.Figs. 12–15 are the inductive switching comparisons of the de-vices GeneSiC 1200, 7 A; Cree 1200 V, 20 A; GeneSiC 600 V,50 A; and Cree 600 V, 4 A (PT), respectively.


Fig. 8. Comparison of simulated (dashed lines) with experimental (solid lines) C–V characteristics of SiC Schottky diodes measured at frequency = 1 MHz.(a) GeneSiC 1200 V, 3 A. (b) GeneSiC 1200, 7 A. (c) Cree 1200 V, 20 A. (d) GeneSiC 600 V, 50 A. (e) Cree 600 V, 4 A (estimated from datasheet).

VI. DISCUSSION

The proposed Schottky diode model is a simple physics-based model whose parameters are extracted using a combi-nation of I–V and C–V measurements, without the need fordevice manufacturing information.

The parameter extraction procedure proposed in this paperis based on the assumption that the carrier mobility at roomtemperature μ300 in the drift region is known. The criticalpoint of the procedure is to obtain the slope S1 from the I–Vcharacteristics and slope S2 from C–V measurement so that thedrift region parameters ND, LD, and A can be extracted. Theseparameters are critical for the accuracy of the proposed Schot-tky diode model under both static and dynamic conditions. ForPT devices, the parameter extraction procedure is the same asthat of the NPT devices. The only difference is that the PTpoint voltage is used in place of the breakdown voltage in theequation used to determine the drift region thickness. The I–Vcharacteristics and C–V characteristics can be either obtainedfrom datasheets, as shown in Fig. 6 for the 600-V 4-A PTdevice, or measured experimentally, as shown in Fig. 7(a)–(d)for the other four devices.

The results of the parameter extraction procedure are shownin Table II. The values of doping concentration and driftregion thickness appear reasonable for SiC and show fairlysimilar design choices. Table III shows a comparison of the

diode designs based on the extracted parameters of Table II.Notice the similar values of rated current density JF , inthe range of 140–180 A/cm2, except for the fourth device,which has a significantly larger current density. The secondcolumn shows the calculated peak electric field Emax at ratedvoltage, calculated using the triangular electric field profileof Fig. 2(b) for the NPT devices and a trapezoidal profilefor the PT device. This electric field is approximately onehalf of the critical electric field (Ec = 2.8 E 6 V/cm) fora doping concentration of 3E15 cm−3 [16]. The last twocolumns show the specific diode resistance calculated using (2)and the capacitance per unit area at rated voltage calculatedusing (5).

Fig. 7 shows pretty good agreement between simulated andexperimental results of I–V static characteristics for all devicesat different temperatures, especially in the linear regions oc-curring at high current levels. At low current levels, some dis-crepancies can be seen. These discrepancies could be reducedby using a nonunity ideality factor n extracted from the I–Vcharacteristics, whereas the ideality factor n of the model ischosen to be unity for simplicity in this paper. Since the lowcurrent region does not play an important role in determiningconduction losses and during switching transients, the simplemodel appears to be adequate for modeling of SiC Schottkydiodes for switching converter applications.


Fig. 9. Corresponding comparisons of simulated (dashed lines) with experimental (solid lines) 1/C2−V characteristics of SiC Schottky diodes measured atfrequency = 1 MHz. (a) GeneSiC 1200 V, 3 A. (b) GeneSiC 1200, 7 A. (c) Cree 1200 V, 20 A. (d) GeneSiC 600 V, 50 A. (e) Cree 600 V, 4 A (estimated fromdatasheet).

Fig. 10. Equivalent circuit used for inductive switching simulation.

Figs. 8 and 9 show the comparisons between simulated andexperimental results of C–V measurements of four differentSiC Schottky diodes. Some discrepancies appear at low voltagein Fig. 8. One reason for this is overestimating the activearea of the Schottky diodes by using the proposed parameterextraction procedure based on a pure Schottky diode structurewhile some tested Schottky diodes are actually JBS or MPS.Another reason may be that the quantity used in the extractionprocedure is the slope S2 of the curves 1/C2

r versus Vr and notthe absolute capacitance values. Fig. 9 shows the curves 1/C2

r

versus Vr, which are very close to straight lines, as expectedfrom (7), indicating that the doping concentration in the driftregion is uniform. Some nonlinear features appear in Fig. 9at low voltage, possibly due to the JBS structure. To improvethe Schottky diode model, one could take into account thesenonlinear features at low voltage in the parameter extractionprocedure. This is left as future work. Note that the plots inFig. 9 tend to overemphasize discrepancies at high voltages:for example, the flat asymptote for the PT capacitance inFig. 9(e) shows a large visual discrepancy; however, the relativecapacitance error with respect to the low-voltage capacitance isless than 5%.


Fig. 11. Simulated (dashed) and experimental (solid) waveforms of inductiveswitching for Schottky diode GeneSiC 1200 V, 3 A. (a) Turn-on. (b) Turn-off(2 A/div, 100 V/div).


Fig. 13. Simulated (dashed) and experimental (solid) waveforms of inductiveswitching for Schottky diode Cree 1200 V, 20 A. (a) Turn-on. (b) Turn-off(5 A/div, 100 V/div).



Fig. 15. Simulated (dashed) and experimental (solid) waveforms of inductiveswitching for Schottky diode Cree 600 V, 4 A (PT). (a) Turn-on (2 A/div,100 V/div). (b) Turn-off (5 A/div, 100 V/div).

TABLE IIIDEVICE COMPARISON BASED ON EXTRACTED PARAMETERS

The inductive switching validations in Figs. 11–15 for thefive different Schottky diodes show good agreements in theturn-on and turn-off transients. The simulation results inFigs. 13 and 14 show more ringing compared with the experi-mental results. The ringing is caused by the interaction betweenthe diode and the rest of the circuit, including the SiC MOSFET,the bus capacitors, and the PCB traces. Accurate prediction ofthis ringing requires accurate modeling of all of these elementsand is beyond the scope of this paper.

In conclusion, the proposed Schottky diode model can begenerally used for a wide range of devices with differentblocking voltage and current ratings and is capable of accu-rately describing device operation under static and dynamicconditions.

VII. CONCLUSION

The proposed parameter extraction procedure includes theextraction of doping concentration, active area, and thicknessof the drift region, which are needed for the proposed physics-based power Schottky diode model. The main advantage isthat this procedure does not require any knowledge of devicefabrication. The only measurements required for the parameterextraction are simple static I–V characterization andC–V mea-surements. Validity of the approach is verified by comparison ofsimulated and experimental results at temperatures from 25 ◦Cto 175 ◦C for five different devices from two different manufac-turers. Inductive switching validation also shows that the modelprovides a fairly good match with experiments. This shows thatthe parameter extraction procedure and model presented in thispaper are generally applicable to SiC Schottky diodes.

ACKNOWLEDGMENT

The authors would like to thank GeneSiC Inc. for providingsome of the diodes used in this work.

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Ruiyun Fu received the B.S. and M.S. degrees inelectrical engineering from Huazhong University ofScience and Technology, Wuhan, China, in 2004 and2007, respectively, and the Ph.D. degree from theUniversity of South Carolina, Columbia, SC, USA,in 2013.

She is currently an Assistant Professor with theSchool of Engineering, Mercer University, Macon,GA, USA. Her research is focused on modeling andsimulation of power semiconductor devices.

Alexander E. Grekov received the M.S. degree fromTaganrog State University of Radio Engineering,Taganrog, Russia, in 1996 and the Ph.D. degree inelectrical engineering from the University of SouthCarolina (USC), Columbia, SC, USA, in 2005.

He is currently a Research Associate with theDepartment of Electrical Engineering, USC. His re-search interests include design, simulation, and mod-eling of SiC power devices and circuits.

Kang Peng received the B.S. degree in electrical en-gineering from Hunan University, Changsha, China,in 2008 and the M.S. degree in electrical engineeringfrom Huazhong University of Science and Technol-ogy, Wuhan, China, in 2011. He has been workingtoward the Ph.D. degree at the University of SouthCarolina, Columbia, SC, USA, since August 2011.

His research interests include power semiconduc-tor device modeling and applications.

Enrico Santi (S’90–M’94–SM’02) received theDr.Ing. degree in electrical engineering from theUniversity of Padua, Padova, Italy, in 1988 andthe M.S. and Ph.D. degrees from the California In-stitute of Technology, Pasadena, CA, USA, in 1989and 1994, respectively.

He was a Senior Design Engineer with TESLAcofrom 1993 to 1998, where he was responsible for thedevelopment of various switching power supplies forcommercial applications. Since 1998, he has beenwith the University of South Carolina, Columbia,

SC, USA, where he is currently an Associate Professor with the Department ofElectrical Engineering. He has published over 100 papers on power electronicsand modeling and simulation in international journals and conference proceed-ings. He is the holder of two patents. His research interests include switched-mode power converters, advanced modeling and simulation of power systems,modeling and simulation of semiconductor power devices, and control of powerelectronics systems.

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