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JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ
Vol. 9 No 1, 01002(4pp) (2017) Том 9 № 1, 01002(4cc) (2017)
2077-6772/2017/9(1)01002(4) 01002-1 2017 Sumy State University
Analog Behavioral Modeling of Schottky Diode Using Spice
Messaadi Lotfi1,
*
, Dibi Zohir2
1 University of Batna, Advanced Electronic Laboratory (LEA), Avenue Mohamed El-Hadi Boukhlouf, 05000, Batna,
Algeria
2 University of Batna, Advanced Electronic Laboratory (LEA), Avenue Mohamed El-Hadi Boukhlouf, 05000, Batna,
Algeria
(Received 17 December 2016; revised manuscript received 08 February 2017; published online 20 February 2017)
This paper presents a SiC Schottky diode model including static and dynamic features
implemented as a parameterized block constructed from SPICE Analog Behavioral Mod-
eling (ABM) controlled sources. The parameters for this block are easy to extract, even from
readily available diode data sheet information. This model can easily simulate the diode’s re-
verse recovery and power losses behavior over all temperatures from 0 C to 175 C.
Keywords: Silicon carbide, Reverse recovery, Schottky diode, Temperature effect, Modeling, pspice, ABM,
Characterization.
DOI: 10.21272/jnep.9(1).01002
PACS numbers: 73.30. + y, 85.30.Hi
*
lotfi.messaadi@gmail.com
1. INTRODUCTION
The semiconductor industry has a well-established
history of “smaller, faster, and cheaper.” Improving
performance and reducing device cost while shrinking
packaging size is fundamental to virtually every semi-
conductor product type. For power products, improved
performance is measured by increased efficiency and
power density, higher power handling capability, and
wider operating temperature range. Such improve-
ments depend largely on the desirable characteristics of
power components used, such as low switching and
conduction losses, high switching frequency, stable
electrical characteristics over a wide temperature
range, high operating temperature, and high blocking
voltage. As silicon power components approach their
theoretical limits, compound semiconductor materials,
such as silicon carbide (SiC) and gallium nitride (GaN),
provide the capability to dramatically improve these
parameters.
Efficient device models are required to evaluate the
performance of SiC Schottky diodes in different appli-
cations and guide system design. Although several
models have been developed for SiC Schottky diodes,
most of them are based on device physics or based on
experiments [1, 2]. For the former, usually a number of
device parameters (which are usually known only by
designers) are required to solve the model, and some-
times the model itself is complicated, and difficult to
solve or time consuming. For the latter, a variety of
experiments are needed. Parameter extractions are
also involved and can be rather tough. Accordingly,
these models are difficult to be integrated into a system
simulation. It is necessary to find some models of SiC
Schottky power diodes specialized for system modeling.
This work is to address this need.
2. DIODE CHARACTERISTICS
In Fig. 1, it is represented the original Schottky Di-
ode model we have implemented. It is composed of a
voltage controlled current generator in parallel to the
original SPICE diode. The aim of this current generator
is to provide a better accuracy in the reverse I-V char-
acteristic. The I-V and reverse current are among the
static characteristics of the device. Due to higher level
of majority carrier injection in Si diode, this causes a
lower voltage drop and hence smaller capacitance to
bias the junction for turn-on process. This is the only
advantage of Si diode compared to SiC. Here, SiC diode
requires a higher voltage to forward bias the device [3].
Apart from that, SiC diode can handle larger reverse
voltage as compared to Si.
Fig. 1– Electric Schottky diode model
The forward I-V characteristics will be modeled by
means of the standard piece-wise linear (PWL) model
[4], featuring a D.C. voltage V0 and a series resistance
Rd as follows:
VD V0 + RD ID (1)
Temperature dependence for V0 and Rd is intro-
duced at this point as:
V0 V00 +
V (T – T0) (2)
MESSAADI LOTFI, DIBI ZOHIR J. NANO- ELECTRON. PHYS. 9, 01002 (2017)
01002-2
Rd Rd0 +
R (T – T0) (3)
where V0 temperature dependence is assumed linear,
which is a good fit in practice, and series resistance is
fitted by a power law. If we want a simpler linear mod-
el we can make n 1. However, a better fit is generally
achieved if n has a value between 2 and 3. For practical
purposes, the value 2 can be forced with sufficient ap-
proximation. T0 is the reference (ambient) temperature.
Substituting (2) and (3) into (1) we get for the diode
forward drop, including temperature variation:
Vd V00 +
V(T – T0) + Rd0ID +
R(T – T0) (4)
This constitutes the model equation. Note that the
way equations (2), (3) and (4) are stated,
V and
R
have dimensions of V/ºC and Ω/(ºC) n. This is consistent
with the way parameters are extracted from data sheet
or measurements.
3. DYNAMIC CHARACTERISTIC
The characteristic that changes with time is inher-
ited in both devices. Si and SiC diodes are compared in
terms of the reverse recovery time, reverse recovery
current and corresponding switching losses. The com-
parisons in dynamic characteristics between two devic-
es are tabulated in Table 1. The SiC and Si diodes used
are of part number SDP04S60 and SB30-03F respec-
tively [5].
Table 1 show that SiC diode has advantages in all
dynamic characteristics. Si diode suffers from higher
reverse recovery current and switching losses. This
clearly indicates the additional carbide substance in
the device may improve switching speed and reduce
power dissipation. Reverse recovery is one of the prop-
erties in a diode. It can be a factor in determining the
efficiency of the applications. When a diode has been
conducting in a forward bias long enough for it to estab-
lish steady state, there will be charges due to the pres-
ence of minority charge carriers. This charge must be
removed to block in reverse direction [6].
Table 1 – Comparison of dynamic characteristics
The characteristic of reverse recovery current expe-
rienced by a diode is represented in Figure 2 above. trr
represents the reverse recovery time, Irr is the peak
reverse current whilst ta is the transition time due to
charge stored in depletion region of the p-n junction. tb
is the time for the current to relax to zero.
Fig. 2 – Reverse recovery current characteristic
The peak reverse recovery current depends on the
falling rate of change in current during turn-off. In SiC
diode, there will be less or none reverse recovery cur-
rent due to its ability to immediately remove stored
charge [7]. However, there are differences observed
during the recovery from the peak values. This is mere-
ly reflected from different device’s fabrication tech-
niques. Normally, in SiC, the rising currents rate to
zero takes a longer time (trr) as shown in part (a) in
Figure 2. This eventually reduces the turn-off speed. In
other SiC type, the speed can also be slightly faster due
to smaller tb but with the cost of higher dissipation.
This can be seen in part (b) as oscillation exists during
the end stage of turn-off time. In addition, if the falling
current rate during the beginning of turn-off time is
high as in the case of non-schottky diode, the reverse
current would also be high, leading to both high power
dissipation and lower in turn-off speed [8].
4. SPICE MODELING
Analog behavior modeling (ABM) is utilized exten-
sively in this model to represent the conductance of the
diode based on equations presented in the first part of
the paper. ABM itself is a powerful tool available in
most SPICE software packages enabling time and fre-
quency domain evaluation of equations or look up ta-
bles.
Fig. 3 – SPICE ABM static and dynamic SiC Schottky diode
model
Fig. 4 – SPICE symbol diode model inserted in spice library
Characteristics
SiC Schottky
(SDP 04S60)
Si Schottky
(SB30-03F)
Reverse Recovery
Time
Unchanged
with tempera-
ture variation
Increases as
temperature
increases
Reverse Recovery
Current
Negligible
Increases as
temperature
increases
Switching Losses
Low
Slightly higher
ANALOG BEHAVIORAL MODELING OF SCHOTTKY DIODE USING SPICE J. NANO- ELECTRON. PHYS. 9, 01002 (2017)
01002-3
Fig. 5 – Forward characteristic at T 25 ºC, 75 ºC, 125 ºC and
175 ºC (Yellow to Green)
Some packages provide block diagram components
simplifying the modeling process. The proposed charge
control model was implemented using ABM block dia-
gram components as shown in Fig. 3. Taking advantage
of existing stability, only the modified charge controlled
equation was added to the native diode model available
in the standard SPICE library. The model is a function
of temperature and with a few parameter changes can
easily represent a new JBS SiC diode at the respective
temperature. The new diode model shown in Fig. 3 was
packaged in a single part for quick archiving into the
existing library.
The first step towards a model is extracting the pa-
rameters that describe the behavior of the diode. For all
semiconductors, temperature has a significant effect on
the material's conductive properties. Silicon carbide in-
creases resistance with increasing temperature and this is
observable in the curve trace. At elevated temperatures,
the carriers at the junction become excited lowering the
junction voltage. These two phenomenons are demon-
strated from the collected data and presented in Fig. 5
illustrate the thermal influence on conductivity.
5. TEST CIRCUIT SIMULATION
The test circuit used for the Pspice simulation of
this model is shown in Fig. 6.
Fig. 6 – The test circuit used for simulation
Fig. 7 – V2 (Vpulse) signal
Fig. 8 – Turn-off reverse recovery current of SiC diodes for
I1 0.5 A, 0.75 A and 1 A (Yellow to Blue)
Fig. 9 – Turn-off transient for I1 1 A and T 25 ºC, 75 ºC,
125 ºC and 175 ºC
Fig. 10 – Forward recovery simulations of SiC Shottky
MESSAADI LOTFI, DIBI ZOHIR J. NANO- ELECTRON. PHYS. 9, 01002 (2017)
01002-4
Fig. 11 – Forward recovery simulations of SiC at T 25 °C,
75 C, 125 C, 175 C (Purple to Blue)
Fig. 12 – Power loss during FET turn-on
Fig. 13 – Power loss during FET turn-on for T 25 C and
175 C
6. CONCLUSION
We have been presented an Analog behavioral mod-
el for SiC Schottky Diodes based on Orcad Pspice. This
model not only described static and dynamic character-
istics of SiC Schottky power diodes, but also reflects
their dependence on temperature. Thus, they are very
useful and effective to estimate the power losses of SiC
Schottky diodes and to predict device temperatures.
The model was also used to estimate the efficiency of a
Si IGBT/SiC Schottky diode hybrid inverter.
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