In this research, we report on the measurement of the capacitance-voltage (C-V) characteristics
Al / ZnO / p-Si / Al Schottky diode at room temperature and in dark condition fabricated by spray pyrolysis
process. C-V characteristics, within the range of frequencies 5 kHz-5 MHz, are investigated and microelectronic
parameters are extracted. Donor density and diffusion potential vary with frequency from 15 to 28
1014 cm – 3, 0.21 to 0.45 V. Besides, the interface state density of Al /ZnO /pSi/Al Schottky is determined
and found to be 1012 (eV cm²) – 1. Calculated at 1 MHz, the interfacial layer thickness and depletion layer
width are of 760 Å and 0.28 m

Benhaliliba, M.

Kiliçoglu, T.

Mokhtari, H.

Ocak, Y.S.

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 7 No 2, 02001(4pp) (2015) Том 7 № 2, 02001(4cc) (2015) 
 
 
2077-6772/2015/7(2)02001(4) 02001-1  2015 Sumy State University 
AC Impedance Analysis of the Al/ZnO/p-Si/Al Schottky Diode: C-V Plots  
and Extraction of Parameters 
 
M. Benhaliliba1,*, Y.S. Ocak2, H. Mokhtari1, T. Kiliçoglu3 
 
1 Material Technology Department, Physics Faculty, Oran University of Sciences and Technology USTO-MB, 
BP1505 Oran, Algeria 
2 Dicle University, Education Faculty, Science Department, 21280 Diyarbakir, Turkey 
3 Department of Physics, Faculty of Science, Batman University, 72000 Batman Turkey 
 
(Received 06 January 2015; revised manuscript received 06 June 2015; published online 10 June 2015) 
 
In this research, we report on the measurement of the capacitance-voltage (C-V) characteristics 
Al / ZnO / p-Si / Al Schottky diode at room temperature and in dark condition fabricated by spray pyrolysis 
process. C-V characteristics, within the range of frequencies 5 kHz-5 MHz, are investigated and microelec-
tronic parameters are extracted. Donor density and diffusion potential vary with frequency from 15 to 28 
1014 cm – 3, 0.21 to 0.45 V. Besides, the interface state density of Al /ZnO /pSi/Al Schottky is determined 
and found to be 1012 (eV cm²) – 1. Calculated at 1 MHz, the interfacial layer thickness and depletion layer 
width are of 760 Å and 0.28 m. 
 
Keywords: Spray pyrolysis, ZnO / p-Si Schottky diode, C-V characteristics, Capacitance-Voltage, Interface 
density. 
 
 PACS numbers: 73.30. + y, 84.37. + q 
 
 
                                                                
* mbenhaliliba@gmail.com 
1. INTRODUCTION 
 
Zinc oxide (ZnO) films and diodes have been among 
the most investigated oxides in recent years, principal-
ly due to its applications in opto-electronic devices  
[1-3]. Many processes have been used to fabricate de-
vice based on ZnO like sputtering, sol gel method [4-5]. 
A Schottky diode based on a wide band gap semicon-
ductor ZnO, Eg  3 eV with a good rectifying behavior 
has been fabricated and its capacitance-voltage is in-
vestigated. In order to fabricate the solar cell based on 
wide band gap semiconductor, we achieve this device 
and we determine its microelectronic parameters such 
as height barrier, diffusion voltage, and donor density, 
at room temperature in dark and at various work fre-
quencies 5k-5 MHz. 
 
2. EXPERIMENTAL PROCEDURE 
 
ZnO films are grown by USPD route from zinc ace-
tate (Zn (CH3COO)2, 2H2O) used as precursor. 0.1 mole 
of zinc acetate was dissolved in 100 ml of methanol. 
Both Al and Sn doping were added from the aluminum 
chloride (AlCl3) and tin chloride (SnCl2) to the precur-
sor with a density of 2 %. The used substrates were 
successively cleaned by methanol for 15 min and dis-
tilled water for 20 min. We deposit our films at fixed 
substrate temperature of 350 °C and the time deposi-
tion was 5 min and the distance nozzle substrate was 
around 5 cm. The metallic contacts were made by 
thermal evaporation in vacuum at 10 – 6 Torr, using a 
mask. The cross section of Al / ZnO / p-Si / Al structure 
is sketched in figure 1A. The obtained Al contacts are 
circular with a diameter of 1.5 mm and thickness of 
250 nm. Capacitance-voltage measurements are per-
formed by the use of a Agilent HP 4294A impedance 
analyzer as shown in figure 1B. 
 
3. MEASUREMENT AND RESULTS 
 
The measurement of capacitance-voltage of 
Al / ZnO / p-Si diode was carried out at frequencies 
range within 50 kHz-5 MHz, is plotted in figure 2. 
It is seen in figure 2 that the capacitance of the as-
fabricated diode increases with a decrease in frequency 
as indicated by arrow, and the reached high point is of 
16 nF at 50 kHz, and these characteristics demonstrate 
a step down, around 0.3 nF, in the reverse-bias region 
as depicted in figure 2. This attenuation of capacitance 
is ascribed to series resistance and interface presence 
as mentioned above or even to deep levels existence in 
the semiconductor bandgap. At zero bias voltage, C-V 
values descend from 3.78 to 0.45 nF when frequency rang-
es within the 50 kHz-5 MHz band. As seen in the C-V 
variation, two regions of capacitance frequency-dependent 
for the forward bias can be estimated, the lower frequency 
(f  500 kHz) and the higher ones (f ≥ 500 kHz). In the 
first regions, the capacitance goes from 8 to 16 nF while 
 
 
Fig. 1A – A schematic cross-section of the Al / ZnO / p-Si / Al 
structure 
 M. BENHALILIBA, Y.S. OSAK, ET AL. J. NANO- ELECTRON. PHYS. 7, 02001 (2015) 
 
 
02001-2 
the second one from 0.35 to 3 nF. In general, at suffi-
ciently high frequencies the interface states do not con-
tribute to the capacitance as mentioned in literature [6-
8]. It is suitable to study C-V data for Schottky diodes by 
plotting 1 / C2 -V, for reverse bias, expressed by eqn. 1. 
 
 
 
Fig. 1B – Experimental system for diode fabrication and 
electrical characterization system. 1. Diode with Al contacts 
are fabricated, 2. Thermal evaporator with vacuum set up, 3. 
Agilent HP 4294A Impedance analyzer for C-V measurement 
 
Using this plot showed in figure 2, we determine the car-
rier density ND according to the following relation [9-10]; 
 
 
2( )1
.
² ²
D
D
V V
C q A N
 (1) 
 
It is seen in figure 3 that the capacitance of the 
Al / ZnO / p-Si diode and the derivate of 1/C2 and the 
coordinate at bias V  0 are then determined from; 
 
 
1 ² 2
,
² D
d C
dV q A N
 (2) 
 
where ε is a dielectric constant of ZnO and p-silicon 
(εi  8.47 ε0, εs  11.9 ε0, where ε0  8.84 10 – 12 F/m), the 
value contact area of A is found to be 0.018 cm2, Vd is 
the diffusion potential at zero bias and Nd is a donor 
carrier density. 
 
 
0
21
.
² ²
V
D
D
V
C q A N
 (3) 
 
The slope gives the carrier density ND, and the ex-
trapolation to 1/C²  0 gives the potential Vd. From the 
C-V characteristics, the potential ΦB is obtained as 
follows [11-12],  
 
 .B D nV V  (4) 
 
This expression is available for an ideal diode but 
for a rectifying one it is a bit corrected as ΦB  cVD + Vn 
 
 
 
Fig. 2 – C-V characteristics at room temperature in dark 
condition of Al / ZnO / p-Si diode at various frequencies 
 
where c correspond to 1/n. The obtained value of the 
carrier density Nd, calculated at 1 MHz, is about  
23 1014 cm – 3 as depicted in figure 4 and Vd is found to 
be 0.135 V. As found above, ΦB  0.74 V and thus we 
deduce the potential Vn which is equal to 0.605 V. Fur-
thermore, from the C-V investigation it is well-known 
that depletion layer width and built-potential can be 
determined. Vd is the diffusion potential at zero bias 
and Vn is the difference between the Fermi level energy 
and the bottom of conduction band.  
The bias dependence of BH, electron tunneling 
through the barrier and the carrier recombination within 
the depletion region are the main elements which make 
n values greater than unity. Where Rs  5.4 kΩ and 
I0  32 nA are calculated from I-V measurement in dark 
behavior (not mentioned here). Where ideality factor 
versus bias voltage is given by [11-12], 
 
 ( ) 1 ( ),s ss
i
n V qN
d
 (6) 
 
where n is dependent on applied voltage, 
 
 ( ),ss V eE E q V  (7) 
 
where Ess is the energy corresponding to the bottom of 
the conduction band BC at the surface of the semicon-
ductor, V is the voltage and Φe is the effective barrier 
height depending applied voltage due to an interfacial 
layer given by equation; 
 
 (1 1 ) .e b n V  (8) 
 
If εi and εs are respectively the permittivity of the inter-
facial layer and the semiconductor, d is the space 
charge width and δ is the ZnO layer thickness, the 
interface density Nss is determined by the equation 9. 
In this study, ideality factor dependence of interface 
states densities were obtained using eqn. 6 [9]. 
 
 
 
Fig. 3 – Plot of 1/C² versus voltage of Al / ZnO / p-Si diode at 
various frequencies 50 kHz-5 MHz 
 
 
1
( ( ) 1) .i sssN n V
q d
 (9) 
 
From I-V characteristics (not shown here) n is found 
to be 3.5. The interfacial layer thickness was found from 
C-V plots in the strong accumulation region using the 
interfacial layer capacitance relation Ci  εi ε0 A / δ [10]. 
Determined from C-V curve at 1 MHz, Ci  1.783 nF. 
 AC IMPEDANCE ANALYSIS OF THE AL/ZNO/P-SI/AL … J. NANO- ELECTRON. PHYS. 7, 02001 (2015) 
 
 
02001-3 
Knowing that the dielectric constant of silicon and ZnO 
are respectively εs  11.9 ε0 and εi  8.47 ε0, the value of 
contact area is A  0.018 cm2 and δ is of 760 Å as listed in 
table 1 and d is deduced from eqn. 10 [9]. 
 
 
 
Fig. 4 – Plot of 1/C2 vs. V of the Al / ZnO / p-Si / Al Schottky 
diode at 1 MHz, red solid line is a linear fit. The inset shows 
the as-fabricated Al / ZnO / p-Si / Al Schottky barrier diode 
 
 
 
Fig. 5 – Plot of 1/C2 versus bias voltage, the extrapolation 
intercept the voltage axis gives the potential in built Vbi and 
the slope is proportional to donor concentration 
 
 
1/2
02 ,s D
D
d V
qN
 (10) 
 
 2 ,D biV V kT q  (11) 
 
where Vbi is the built-in potential and VD is the diffusion 
potential. The figure 5 shows how we determine the 
value of Vbi-2kT / q and the slope of linear part of the 
1/C2 curve. 
The figure 6 depicts the density of states of interfaces 
(Nss) versus energy (Ess – Ev). As shown in fig. 6, the Nss 
variation is plotted within the 0.58-0.68 eV energy 
range, two curves corresponding respectively to with and 
without series resistance Rs are plotted. The decay of Nss 
from 1012 to 1011 (eV cm2) – 1 is observed. 
 
 
 
Fig. 6 – Interface state density distribution profile of 
Al / ZnO / p-Si / Al Schottky diode at room temperature 
 
4. CONCLUSION 
 
Al / ZnO / p-Si Schottky diode has been successfully 
fabricated by spray pyrolysis and thermal evaporation 
processes in vacuum. The capacitance verus voltage has 
been measured at room tempearture and various fre-
quencies and electronic parameters have been deter-
mined. At 1 MHz, we find then ND  23.21 1014 cm – 3, 
VD  0.135 V, d  0.28 µm and δ  760 Å,  the potential 
VD and the depletion width decreased when the frequen-
cy increased while the donor density and interfacial 
layer thickness increased with frequency. The diode 
presents a non-ideal behavior due to interface density 
which is evaluated at 1 MHz of 1012 (eV  cm2) – 1.  
 
ACKNOWLEDGMENTS 
 
This research is a part of the D01920120039 
CNEPRU project, supported by The High Teaching 
and Scientific Research Ministry MESRS. 
www.mesrs.dz and USTOMB  www.univ-usto.dz 
 
 
Table 1 – Frequency, donor carrier concentration, the voltage Vbi-2kT / q, the slope, the depletion layer width and interfacial 
layer thickness 
 
 
 
 
 
-2.0 -1.8 -1.6 -1.4 -1.2 -1.0
1.50E+019
2.00E+019
2.50E+019
3.00E+019
3.50E+019
 
 
Y =-3.247E18-1.933E19 X
1
/C
² 
  
(1
/F
²)
Voltage (V)
 1/C²  at 1MHz
 Polynomial fit 
Frequency 
(kHz) 
ND 
(  1014 cm – 3) 
VD 
(V) 
The ratio VD / ND 
(V cm3 10 – 14) 
Slope of linear 
part of  1/C2 vs. V (  1019) 
depletion layer 
width d (µm) 
Interfacial layer 
thickness δ (Å) 
50 15.7 0.45 0.028 3.3 0.61 84 
100 14.6 0.43 0.029 3.5 0.62 101 
200 15.1 0.39 0.025 3.4 0.57 150 
500 18.4 0.29 0.016 1.99 0.46 370 
1000 23.2 0.135 0.006 2.2 0.28 760 
2000 26.3 0.008 0.0003 1.86 0.06 1357 
5000 28.1 0.21 0.007 1.78 0.30 2772 
 M. BENHALILIBA, Y.S. OSAK, ET AL. J. NANO- ELECTRON. PHYS. 7, 02001 (2015) 
 
 
02001-4 
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AC Impedance Analysis of the Al/ZnO/p-Si/Al Schottky Diode: C-V Plots and Extraction of Parameters

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AC Impedance Analysis of the Al/ZnO/p-Si/Al Schottky Diode: C-V Plots and Extraction of Parameters

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