TCAD Based Simulation and Performance Optimization of InxGa(1-X)N based Solar Cell

Table of contents

1. I. INTRODUCTION

roup III-V nitride are now a widely studied class of semiconductor materials. In x Ga (1-x) N, with small x, are very ef ficient light emitters, even in samples with relatively high densities of structural defects are used as component layers in a wide range of optoelectronic devices. Its high light absorption and its Indium-composition-tuned band gap, the Indium Gallium Nitride (InGaN) ternary alloy is a good candidate for high-efficiency-high-reliability solar cells able to operate in harsh environments.

Moreover, the most important advantage of InGaN alloy might be the direct band gap energy which can be adjusted according to the indium composition.

Thus, the InGaN's energy band gap can be tuned from 0.7 eV to 3.42 eV, covering approximately the total solar spectrum [1]. In this paper, we present simulation of InGaN based p-n homo junction solar cell at different Indium composition . The layers of InGaN solar cell can be deposited using the cost-effective techniques, such as Metal Organic Chemical Vapor Deposition (MOCVD), Metal Organic Vapor Phase Epitaxy (MOVPE), and Molecular Beam Epitaxy (MBE) [2]. Whatever the deposition technique used, higher growth rates (~1.0 Angstrom/second) and lower temperature(~550 °C) characterize the InGaN growth

2. (

)

InN GaN g x g g 1-x In Ga N =x.E +(1-x).E -b.x.(1-x) E (1)

where the band gap energy of InN denoted as ?? ð??"ð??" ?????? and band gap energy of GaN denoted as ?? ð??"ð??" ?????? is 0.7eV and 3.42eV, respectively, x is the indium content and ?? is the bowing parameter (?? = 1.43) [5][6].

The other modeling parameters of the In??Ga (1-??)N alloy were calculated using the following equations-Electron Affinity [7][8][9]: -

( ) ( ) 1 4.1 0.7(3.4 ) x g x In Ga N E ? ? = + ? (2)

Relative permittivity[6]: -

( ) ( )1

15.3 8.9(1 ) ( ) 18 1 (0.9 2.3(1 )).10

x x In Ga N x x ? ? = + ? (3)C x x N In Ga N x x ? = + ? (4)

Effective density of valence band [8][9]: -

( ) ( )19 1

(5.3 1.8(1 )).10

V x x N In Ga N x x ? = + ? (5)

3. b) Physical & Optical Perameters

The energy band gap of In x Ga (1-x) N is depended on concentration of Indium (x) and energy band gap of In x Ga (1-x) N is given by following formula ( )

(GaN) 1 (524* x) n x n x U In Ga N U ? = +(11) ( ) ( )h(GaN) 1 (6.5* x) h x x U In Ga N U ? = +(12)

Where the U n(GaN) is 1000 & U h(GaN) is 170.

For the In??Ga 1-?? N alloys, Adachi's wavelengthdependent refractive index model is given by the following equation [6,12]:

2 E E E (E) 2 1 1 B E E E ph ph ph g g g n A ? = ? + ? ? + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? .......(13)

Where Eph is photon Energy A & B is coefficient dependent on material composition that equation giving by following equation. This real part of refractive index is approximate same 2.32 Its slightly worry for InGaN alloy with different composition of x from 2.30 to 2.34.

The InGaN alloys absorption coefficient ?? is given by equation ( 16) [13] ( )

4. (

) Mobility [11]: -

5 2 1 10 (E E ) D(E E ) x ph g ph g x In Ga N C ? ? = ? + ? ???????????????????(B B i i B U U T U N T U ? ? ? ? = + ? ? ? ? + ????????????????????(10)( ) . . % SC OC in I V FF P ? =(9)

Where I SC is short circuit current, V OC is open circuit voltage, P in is incident optical power and FF is fill factor of the solar cell. [10] ( ) ( ) 1 0.17 1.0(1 ) Intrinsic carrier concentration: -

h x x m In Ga N x x ? = + ? (7)2 g B E K T i C V N N e n ? =(8)

Where K B is Boltzmann constant and T is lattice temperature Efficiency: -

Velocity of electron & hole (S n,h ) [cm/s] 10 3

5. Recombination time of electron & hole (? n,h )[sec.] 1ns

For the case studied, the initial physical and geometrical parameter values used for In x Ga (1-x) N single p-n junction solar cell are presented in table 6. After modeling & simulation get results with the help of above work following results are tabulates ( )

5 1 1.24 2.2*10 E x g x In Ga N ? ? ? = ? ????.(19)

Where ? is photon wavelength

For the In??Ga 1-?? N alloys, wavelength-dependent imaginary part of refractive index is given by the following equation

4 K ?? = ? ??????????????(20)

Where pie (?) is 3.14. Following Fig. 2 Spectral response with respect to wavelength has been shown above in Fig. 5. Source photo current is maximum possible total current due to incident photons, available photo current is current due to total generated electron-hole pair and cathode current is total current collected at terminals. Among these three, source current is always greater than other two. Total photons incident losses due to reflection, transmission, thermalization etc. Further there is loss of some of the generated electron-hole pairs due to recombination and hence collected cathode current is less than or equal available photo current. After getting all results we gets maximum efficiency is 19.36% at In 0.50 Ga 0.50 N single p-n junction solar cell. This above table 9 shows simulation results of fill factor and efficiency at different composition of x for single p-n junction solar cell. In this paper we report the TCAD simulation and performance optimization of In x Ga (1-x) N based solar cell. Evaluation of the performance of the device has been performed for various values of mole fraction x of In in InGaN. Extracted performance parameters such as current, voltage, power, fill factor and efficiency from the proposed structure are: open circuit voltage (V oc ) of 1.08 V, Short circuit current (I sc ) is 0.027A, Fill Factor (FF) is 88.58%, Maximum voltage (V max ) is 0.99 V, Maximum current (I max ) is 0.26A and overall efficiency is 19.36%. IV.

6. Conclusion

Figure 1.
[3] II. MODELLING AND SIMULATION a) Structure As the numerical simulation is an important way to explore the possibility of a new solar cell structure the InGaN single p-n junction solar cell has been studied using commercial device simulator Atlas from Dilvaco Inc [4].All the simulations were performed under normalized conditions that are 1 sun, a temperature of 300 K, and AM0 illumination. The In x Ga (1-x) N single p-n junction solar cell structure studied consists of p-type emitter and n-type base as shown in Fig.1.
Figure 2. Fig. 1 :
1Fig. 1: In x Ga (1 -x) N single p-n junction solar cell structure
Figure 3.
The following equation(11,12) is simplified equation for electron & hole mobility for InGaN alloy.
Figure 4. Table 2 :
2
of electron affinity and relative permittivity
of In x Ga (1-x) N at different value of x
Material Electron Relative
In x Ga (1-x) N Affinity(X) permittivity(E)
GaN 4.092 8.9
In 0.20 Ga 0.80 N 4.3955 10.18
In 0.35 Ga 0.65 N 4.5931 11.14
In 0.50 Ga 0.50 N 4.765 12.1
In 0.62 Ga 0.38 N 4.884 12.868
In 0.78 Ga 0.22 N 5.017 13.892
In 0.90 Ga 0.10 N 5.0975 14.66
InN 5.152 15.3
Note: ( )
Figure 5. Table 3 :
3
Energy Band Gap of In x Ga (1-x) N at x
Material In x Ga (1-x) N Energy band gap (Eg)
GaN 3.42
In 0.20 Ga 0.80 N 2.6612
In 0.35 Ga 0.65 N 2.1672
In 0.50 Ga 0.50 N 1.7375
In 0.62 Ga 0.38 N 1.4401
In 0.78 Ga 0.22 N 1.1076
In 0.90 Ga 0.10 N 0.9063
Year 2019 InN 0.77
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of Researches in Engineering ( ) Volume XIX Issue IV Version I F
Global Journal
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Figure 6. Table 1 :
1
Effective density Effective density
Material of Conduction of Valance
In x Ga (1-x) N band (Nc) Band(Nv)
(1×10 18 ) (1×10 20 )
GaN 0 0
In 0.20 Ga 0.80 N 1.8 1.06
In 0.35 Ga 0.65 N 3.15 1.855
In 0.50 Ga 0.50 N 4.5 2.65
In 0.62 Ga 0.38 N 5.58 3.286
In 0.78 Ga 0.22 N 7.02 4.134
In 0.90 Ga 0.10 N 8.1 4.77
InN 9 5.3
Effective mass of electron[7]
Figure 7. Table 5 :
5
Material In x Ga (1-x) N Mobility of Electron (MUN or Un) Mobility of Hole (MUP or Uh)
GaN 1000 170
In 0.20 Ga 0.80 N 1104.8 171.3
In 0.35 Ga 0.65 N 1183.4 172.275
In 0.50 Ga 0.50 N 1262 173.25
In 0.62 Ga 0.38 N 1324.9 174.03
In 0.78 Ga 0.22 N 1408.7 175.07
In 0.90 Ga 0.10 N 1471.6 175.85
InN 1524 176.5
Figure 8. Table 4 :
4
Material Effective Mass of Effective Mass
In x Ga (1-x) N Electron (Mn) of Hole (Mh)
GaN 0.2 1
In 0.20 Ga 0.80 N 0.184 0.834
In 0.35 Ga 0.65 N 0.172 0.7095
In 0.50 Ga 0.50 N 0.16 0.585
In 0.62 Ga 0.38 N 0.1504 0.4854
In 0.78 Ga 0.22 N 0.1376 0.3526
In 0.90 Ga 0.10 N 0.128 0.253
InN 0.12 0.17
Figure 9. Table 7 :
7
Material In x Ga (1-x) N Isc (mA/cm^2) Voc (V)
In 0.20 Ga 0.80 N 0.00813315 1.9963
In 0.35 Ga 0.65 N 0.0158621 1.51555
In 0.50 Ga 0.50 N 0.0274789 1.08184
In 0.62 Ga 0.38 N 0.0385468 0.781803
In 0.78 Ga 0.22 N 0.0539032 0.446001
In 0.90 Ga 0.10 N 0.0654447 0.242227
Figure 10. Table 6 :
6
( ) 1 x D In Ga N ( x ? ) 0.665 3.616 2.460 x = ? + ? x 2 ?(18)
Following equation is simplified expression of
absorption coefficient ?? (19)
Imaginary Part of Refractive Index(K) 0 2000 4000 6000 8000 10000 12000 x=0.1 x=0.9 x=0.62 x=0.35 x=0.2 x=0.5 x=0.78
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
Wavelength(?)
Fig. 2: Graph of wavelength vs imaginary part of refrective index at different value of x
Some initial parameter are given in the following table-6
Parameter Used Value
Thickness of n-InGaN layer 0.015 micron
Thickness of p-InGaN layer 0.63 micron
n-type doping [cm -3 ] 2e18
Note: ( )
Figure 11.
TCAD Based Simulation and Performance Optimization of In x ga (1-X) N Based Solar Cell
( ) 1 x C In Ga N ( x ? ) 3.525 18.29 40.22 x = ? + x 2 ? 37.52 x 3 + 12.77 x 4 ????????????????????(17)
III. RESULT & DISCUSSION
Figure 12. Table 8 :
8
Material In x Ga (1-x) N Im (mA/cm^2) Vm (V)
In 0.20 Ga 0.80 N 0.00798644 1.88
In 0.35 Ga 0.65 N 0.01556 1.41
In 0.50 Ga 0.50 N 0.0265989 0.99
In 0.62 Ga 0.38 N 0.0372977 0.69
In 0.78 Ga 0.22 N 0.0507992 0.369998
In 0.90 Ga 0.10 N 0.0563837 0.19
Figure 13. Table 9 :
9
Material In x Ga (1-x) N Fill Factor Efficiency
In 0.20 Ga 0.80 N 92.4754 11.0401
In 0.35 Ga 0.65 N 91.2636 16.1321
In 0.50 Ga 0.50 N 88.5801 19.3624
In 0.62 Ga 0.38 N 85.3975 18.9231
In 0.78 Ga 0.22 N 78.1818 13.8203
In 0.90 Ga 0.10 N 67.5787 7.87713
Figure 14.
Year 2019
22
of Researches in Engineering ( ) Volume XIX Issue IV Version I F Efficiency Corporation, International Journal of Photoenergy, Volume 2015, Article ID 594858, 9 pages 2. N. Akter, "Design and simulation of Indium Gallium Nitridemultijunction tandem solar cells," International Journal of Research in Engineering and Technology, vol. 3, no.1,pp. 315 321, 2014. 3. D. V. P. McLaughlin and J. M. Pearce, "Progress in indium gallium nitride materials for solar photovoltaic energy conversion," Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science,vol.44,no.4,pp.1947-1954,2013. References références referencias 1. Mesrane, F. Rahmoune, A. Mahrane and and A. Oulebsir " Design and Simulation of InGaNp-n Junction Solar Cell" Hindawi Publishing
Global Journal 5. F. Bouzid and S. Ben Machiche, "Potentials of InxGa1-xN photovoltaic tandems," Revue des
Energies Renouvelables, vol.14,no.1,pp.47-
56,2011.
(b) 6. Z. Li,H.Xiao, X. Wang et al., "T heoreticalsimulations
Fig. 7: of InGaN/Si mechanically stacked two-junction solar cell," Physica B: Condensed Matter, vol. 414, pp.
110-114, 2013.
1

Appendix A

Appendix A.1 Acknowledgement

The authors are thankful to SERB, DST Government of India for the financial support under the grant sanctioned for Project No.ECR/2017/000179.

Appendix B

  1. Investigation of InGaN/Si double junction tandem solar cells. F Bouzid , L Hamlaoui . Journal of Fundamental and Applied Sciences 2012. 4 p. .
  2. Finite element simulations of compositionally graded InGaN solar cells. G F Brown , J W Ager , Iii , W Walukiewicz , J Wu . Solar Energy Materials & Solar Cells 2010. 94 (3) p. .
  3. Simulation of a solar cell based on InGaN. L A Vilbois , A Cheknane , A C Boney , T Benouaz . Energy Procedia, 2012. 18 p. .
  4. Monte Carlo sim-ulation of electron transport in the IIInitride Wurtzite phase materials system: binaries and ternaries. M Farahmand , C Garetto , E Bellotti . IEEE Transactions on Electron Devices 2001. 48 (3) p. .
  5. GaAs shallow homojunction solar cells fabricated on thin epitaxial films by a simple Zn solid state diffusion method. M Garozzo , A Parretta , G Maletta , V Adoncecchi , M Gentili . Solar Energy Materials 1986. 14 (1) p. .
  6. A TCAD-based modeling of GaN/InGaN/Si solar cells. M Nawaz , A Ahmad . ID 035019. Semiconductor Science and Technology, 2012. 27.
  7. Modeling of two junction, series-connected tandem solar cells using top-cell thickness as an adjustable parameter. S R Kurtz , P Faine , J M Olson . Journal of Applied Physics 1990. 68 (4) p. .
Notes
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Date: 2019-01-15