InP square quantum well

InP square quantum well

Accepted Manuscript The hydrostatic pressure and temperature effects on hydrogenic impurity binding energies in lattice matched InP/In0.53Ga0.47As/InP...

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Accepted Manuscript The hydrostatic pressure and temperature effects on hydrogenic impurity binding energies in lattice matched InP/In0.53Ga0.47As/InP square quantum well P. Başer, S. Elagöz PII:

S0749-6036(16)31453-7

DOI:

10.1016/j.spmi.2016.12.020

Reference:

YSPMI 4723

To appear in:

Superlattices and Microstructures

Received Date: 10 November 2016 Revised Date:

7 December 2016

Accepted Date: 7 December 2016

Please cite this article as: P. Başer, S. Elagöz, The hydrostatic pressure and temperature effects on hydrogenic impurity binding energies in lattice matched InP/In0.53Ga0.47As/InP square quantum well, Superlattices and Microstructures (2017), doi: 10.1016/j.spmi.2016.12.020. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT The hydrostatic pressure and temperature effects on hydrogenic impurity binding energies in lattice matched InP/ In0.53Ga0.47As /InP square quantum well P. Başer, and S. Elagöza Department of Physics, Cumhuriyet University, 58140 Sivas, Turkey Department of Nano Technology Engineering, Cumhuriyet University, 58140 Sivas, Turkey

Hydrostatic pressure and temperature dependent a) Dielectric constant (b) Potential height and

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(c) Effective mass percentile changes for the lattice matched InP/ In0.53Ga0.47As /InP square well

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system.

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ACCEPTED MANUSCRIPT The hydrostatic pressure and temperature effects on hydrogenic impurity binding energies in lattice matched InP/ In0.53Ga0.47As /InP square quantum well P. Başer, S. Elagoza Department of Physics, Cumhuriyet University, 58140 Sivas Turkey Department of Nanotechnology Engineering, Cumhuriyet University, 58140 Sivas, Turkey

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a

ABSTRACT: The on-center shallow-donor impurity binding energy in lattice matched InP/In0.53Ga0.47As square quantum well structure have been theoretically investigated using

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effective mass and variational techniques. The effects of hydrostatic pressure, temperature and well width has been calculated and the results are discussed.

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Keywords: Donor Impurity Binding Energy; Quantum-well; Hydrostatic Pressure; Temperature Effect

Introduction:

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PACS: 73.21 Fg, 74.62 Fj, 73.40 Qv, 78.67 De

The properties of low-dimensional semiconductor systems (LDSS) have drawn great interest amidst the theoretical and applied physicists due to the quantum confinement effects

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[1-4]. The study of hydrogenic impurity is one of the main problems in semiconductor low dimensional systems because the presence of impurity in nanostructures influences greatly the electronic mobility and their optical properties. Since Bastard’s [5] pioneering works in the

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study of the donor binding energy of a hydrogenic impurity within an infinite potential well structure, the hydrogenic impurity states in quantum well (QW) systems have been widely studied [6–11]. Some macro-parameters have significant effects on low dimensional systems such as external electric field, magnetic field, hydrostatic pressure and temperature. These macro-parameters are also widely studied; for example, hydrostatic pressure has been shown to be of considerable utility in determining the electronic properties of semiconductors, both bulk materials and more recently low dimensional systems [12]. Hydrostatic pressure is an important thermodynamic variable, which provides a powerful tool to control and investigate the electronic states and optical properties of semiconductor materials based devices. Especially InP and GaAs are medium-gap semiconductors but the electron spin g factor at the

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ACCEPTED MANUSCRIPT band edge of InP is positive in contrast to InSb, InAs GaSb and GaAs [13], therefore the behavior under the hydrostatic pressure is expected to be different then say AlGaAs/GaAs/AlGaAs [14] and GaAs/InGaAs/GaAs [15] quantum wells. Lattice matched In0.53Ga0.47As to InP is an important ternary semiconductor alloy and it is the subject of intense study worldwide at the present time for a variety of optoelectronic

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applications due to its superior transport and optical properties (i.e., the high roomtemperature electron mobility 10x103 cm2V-1s-1and band-gap energy of 0.75 eV) [16-19]. The mobility is proportional to the carrier conductivity. As mobility increases, so does the currentcarrying capacity of transistors. A higher mobility shortens the response time of

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photodedectors, reduces series resistance, improves device efficiency and reduces noise and power consumption. In0.53Ga0.47As -InP quantum wells permit emission to be obtained in the wavelength range from 1.1 to 1.6 µm by variation of the In0.53Ga0.47As quantum-well width

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[20-22]. This wavelength range covers the regions of low attenuation and low dispersion in present-day optic-fiber communication systems. Other novel applications of InGaAs quantum wells and superlattices (with AlInAs barrier layers) include high-gain photodetectors [23], high-electron-mobility transistors [24] and high-speed 1.5µm optical modulators [25, 26]. The above list is not intended to be exhaustive but it does provide an indication of the wide range

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of applications available for quantum wells fabricated using InGaAs [27]. In this study, we investigate the hydrostatic pressure and the temperature dependency of the binding energy of a shallow donor impurity in lattice matched InP/In0.53Ga0.47As /InP square quantum well system using variational methods in the effective mass approximation

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scheme.

2.Theory:

In the framework of the effective-mass approximation, the Hamiltonian for an electron under the influence of hydrostatic pressure (P) and temperature (T) in a single InP/In0.53Ga0.47As/InP QW is given by [8]

H = ∇2 −

2 + V ( z , P, T ) r

(1)

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ACCEPTED MANUSCRIPT The Hamiltonian is written in a dimensionless form so that all energies are expressed in units =

of the effective Rydberg



units of the effective Bohr Radius

⁄2ℏ

~6.94

=ℏ ⁄





and all distances are expressed in

~ 83.38

, where



and

are the

electronic mass and dielectric constant for InP. The differences in the effective masses and dielectric constant of InP and In0.53Ga0.47As have been neglected in calculations. The origin of

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the coordinate system is chosen to be at the center of the well where the impurity ion is located and r is the dimensionless distance between impurity ion and electron.

The variation of the effective mass with temperature and pressure can be calculated from .

2

= 1+

" !7 " - (), +)

+

1 8 " - (), +) + ∆&

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& ∗ (), +) "

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theory according to [28]

Where is an energy related to the momentum matrix element

0.114 eV is the spin-orbit splitting for InP,

& is

" !

= 5.41

(2) for InP, ∆& =

the free electron mass [29]. The pressure

and temperature dependent static dielectric constant (), +) for GaAs is given by [15] 12.74 e0;.<=∗;& ! (), +) = 9 >? 13.18 0;.=E∗;& !

" - (), +)

Similarly,

@. ∗;&>A (B0=C.<)

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>?

&. ∗;&>A (B0E&&)

, + ≤ 2005 , + > 2005

(3)

is the pressure and temperature dependent energy gap for InP

(In0.53Ga0.47As) in units of eV and is given by

= 1.52

10.8 /100

5.405/100

=

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& -

(

& -

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where

- (), +)

/2)

= 0.42

(. = 7.7/100

& -

+ .) − 4+ (+ + H)0;

(4)

) is the energy gap at P=0 GPa and T=0 K, . =

/2) ) is the pressure coefficient and 4 =

/5 (4 = 4.19/100

/5) and c=204 K (c=271 K) are temperature

coefficients respectively for GaAs (and InAs) [30, 31]. Using the given parameters,

T as follows [31]: IJKLMN (), +, /) -

=

- (), +)

IJMN (), +) -

is written for GaxIn1-xAs alloy as a function of x, P and

+O

KLMN (), +) -



IJMN (), +)P/ -

+ H/(1 − /)

(5)

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ACCEPTED MANUSCRIPT where c is the bowing parameter c=-0.475. Similarly, function of P and T as follows with using parameters

GPa and T=0 K, . = 8.2 /100

& -

KL! - (), +)

= 1.42

is written for InP as a is the energy gap at P=0

/2) is the pressure coefficient and 4 = 4.5/100

and c=335 K are temperature coefficients. [29]. In equation (1)

/5

(Q, ), +) is the pressure and temperature dependent confining potential for

where

2R

and

& (Q, ), +)

= 2R(S) W

KL! - (), +)



IJKLMN (), +)X -

,

|Q| ≥ ())

0, |Q| < ())

2S

are

band

offsets

for

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(Q, ), +) = V

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electron and holes defined as [32],

conductance

and

valance

(6)

band,

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respectively. Conduction band to valence band offset assumed to remain constant with pressure for GaInAs/InP and the ratio is taken as 0.38: 0.62 [27].

For a donor impurity atom at the center of a quantum well of width L(P)=2R(P) the hydrostatic pressure dependent square quantum well width L(P) is given by ref [29], T()) = T(0)(1 − (U;; + 2U; )P)

(7)

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Where T(0) is the well width without hydrostatic pressure and U;; and U; are the elastic

compliance constant, which can be calculated using the definitions of elastic constants for

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InGaAs given below [33].

\;; = (8.34 + 3.56 ∗ /) ∗ 10; \; = (4.54 + 0.80 ∗ /) ∗ 10

\;; + \; −\; ; U; = (\;; − \; ) ∗ (\;; + 2\; ) (\;; − \; ) ∗ (\;; + 2\; )

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(8)

(9)

Due to complexities from the Coulombic term that describes the impurity binding, the binding energy is calculated by using variational methods. For this, we first obtain the ground state energy corresponding to the Hamiltonian given by Eq (1) without the Coulombic term. The ground state solution for this simplified case are just well know finite square well solutions and can be written as, [33]

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ACCEPTED MANUSCRIPT  Be+κ z  ψ s ( z ) = C sin(k z ) + D cos(k z )  Fe−κ z 

z < − R( P) − R( P ) < z < R( P )

In equation (11)

&

&

=b

and

&



&

is the ground state eigenenergy and

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z > − R( P)

where ^ ve k are given by ^=b

(10)

(11)

&

is the potential given by Eq (6).

solving the following transcendental equation.

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^ tan(^ ) =

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By matching _ and `_⁄`Q at the boundaries z=0 and R, the eigenenergy

&

can be obtain by

(12)

For calculating the ground state binding energy for hydrogenic impurity following Bastard’s procedure [5, 34], the trial wave function for the ground state is chosen as; 0h⁄i

(13)

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Ψ = g_N

where a is the variational parameter, N is normalization constant and _N is the ground state

eigenfunction given with Eq. (10). The ground state binding energy Eb, of the impurity is defined as the energy difference between the energy of system with and without the presence

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of Coulombic interaction. In this way, the ground state binding energy of the system is

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positively defined and given as

Ek =

&



lmnΨ|o|Ψp.

(14)

After some algebra, the normalization constant N and needed terms for obtaining binding energies are obtained as [31].

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ACCEPTED MANUSCRIPT t

2 ? 1 g = q E s V1 − (1 + ^ a ) ra

\wx(2^ ) 1 y + z (1 + ^ a ) a 1 + ^ a

λ

2

+κ2 −

Cos (κR )e

−2R / λ

πN 2κλ2 2

 2R  e − 2 R / λ 1 + Sin(2κR ) λ  

  1 k 2 − κ 2 2 1 + κ 2λ2 1 + κ 2λ2 2 R  1 k 2 R + + + − λ −    kλ + 1 λ (kλ + 1)2 kλ + 1 λ   

nΨ| (Q)|Ψp = +

rg aE \wx (^ ) 2( a + 1)

nΨ|−2/}|Ψp = −rg a ~+

0 €u/i

1 − 1+^ a

& y1

0 u/i

^aUlm(2^ ) 2\wx (^ ) •+ (1 + ^ a ) 1+ a

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(15a)

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1

0;/

(15b)

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2

2

a

+

2^ 1 + z a 1 + ^a

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+

πN 2λ

v1 +

^aUlm(2^ ) \wx (^ ) 2 1 − y1 + + z{| 2(1 + ^ a ) 1+ a a 1+ a



Ψ − ∇2 Ψ =

0 u/i

+

~1 +

\wx(2^ ) 1+^ a t

€u 0 uW€•‚X •

(15d)

(15c)

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nΨ|o|Ψp can now be easily computed from Eq. (15) and its minimization with respect to a leads to the desired ground state binding energy through Eq. (14).

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3.Results and Discussion:

We have chosen the parameters such that we avoid any further complications such as gammax crossing of InP In0.53Ga0.47As . It is known that InP goes from direct to indirect band gap (gamma-x crossing) at 15 GPa [35] and In0.53Ga0.47As undergo such a transformation when Ga alloy concentration goes beyond x=0.6 [gamma-L crossing] and x=0.8 [gamma-x

crossing][36]. We have calculated the ground state donor binding energy Ek as a function of

well width for different hydrostatic pressures P=0, 5, 10 and 12 GPa at T=300 K for finite potential barrier with a lattice matched InP/ In0.53Ga0.47As /InP QW.

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In Figure 1, the binding energy Ek as a function of quantum well width L(P), for various

hydrostatic pressure values at RT. The most important feature that is observed is that, the

ground state binding energy decreases with increasing hydrostatic pressure. This is contradictory to similar studies that were done for single GaAs/AlGaAs and GaAs/GaInAs square quantum wells. The reason for this can be explained by looking the behavior of the

is seen in the potential height

&ƒ (Q, ), +)

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changes of parameters with pressure for these material groups. The only behavioral difference for electron. It is decreasing as P increase for

InP/Ga0.47In0.53As/InP system while increases for AlxGa1-xAs/GaAs/AlxGa1-xAs and Ga1xInxAs/GaAs/

Ga1-xInxAs square quantum well systems.

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This effect come from Eq (4) and Eg (5); InP and Ga0.47In0.53As both have an increase of band gap with pressure as similar to GaAlAs/GaAs and GaAs/InGaAs but unlike these the difference in increase ratios are such that makes the conduction band potential height offset

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decrease i.e, Ga0.47In0.53As band gap increases more than InP band gap with pressure. As a result confining potential for electrons get weaker thus resulting a decrease in binding energy as seen from Fig. 2. For large well widths, the binding energies converge to bulk InxGa1−xAs ground state binding energy values as expected, since the confinement effects are weaker in this range so the binding energy becomes similar to bulk Ga0.47In0.53As binding energy. As the

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well widths get smaller, the binding energy increases due to the spatial confinement getting stronger. That is, the distance between the electron and the impurity is decreased when the well width L(P) is decreased which makes the binding stronger. Further decreasing the well widths cause the binding energy to reach a maximum value and then to drop sharply due to

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the leakage of the electron wave function into potential barrier until the particle totally tunnels out to the barrier region where its binding energy drops to the bulk value of InP. This is due to

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the fact that as the spatial confinement forces the particles to localize into a smaller space, the quantum confinement effects kicks in, that is; charged particles cannot be localized further due to the uncertainty principle and they start leaking out to the barrier reducing the binding energy sharply.

It is important to see how parameters are affected by the hydrostatic pressure and temperature for all well widths. These parameters and their changes with the hydrostatic pressure and temperature are summarized in Table 1 and Table 2. Similarly, in Table 2 the change of the parameters by increasing temperature is summarized for P=0 GPa. L(P)=0.14aB It is clearly seen from Table 2, that temperature changes do not really effect the important parameters as compared to hydrostatic pressure. As a results, the variation of binding energy

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ACCEPTED MANUSCRIPT due to temperature is ignorable in close agreement with the precious works found in the literature. [36] For the sake of completeness, we have shown all the percentile changes of dielectric constant, potential height and effective mass vs P and T for an on-center impurity in Fig. 3. Lines with empty square symbols represents T dependency and it is very small compared with the

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hydrostatic pressure dependency shown by lines with the filled diamond symbols. It is clear from Fig. 3 that temperature dependency of ground state donor binding energy in InP/ In0.53Ga0.47As/InP system is negligible, that is the system is very stable under temperature changes. On the other hand the hydrostatic pressure is very effective as shown in Fig. 3, the

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dielectric constant decreases (a), the potential height decreases (b) and the effective mass increases (c) with increasing pressure all add up to result a decrease in binding energy.

4.Conclusions:

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We have studied the ground state binding energy of a hydrogenic impurity under the effects of hydrostatic pressure and temperature as a function of well width by using variational techniques within the effective mass approximation in lattice matched InP/In0.47Ga0,53As/InP square quantum well structures. The obtained results illustrate that the ground state binding energy decreases with the hydrostatic pressure which is just the opposite of what is found for

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AlGaAs/GaAs/AlGaAs and GaAs/InGaAs/GaAs systems. The reason for this behavior is explained by the decrease of potential height for InP/In0.47Ga0,53As/InP system as the hydrostatic pressure increases. The binding energy dependency due to well width is found similar to the AlGaAs/GaAs/AlGaAs and GaAs/InGaAs/GaAs systems. That is; it is stronger

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for intermediate well width (0.1aB–0.4aB) and weaker for larger or smaller well widths. Furthermore, we have also shown that, the binding energy is very stable for a large (0-300K)

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range of temperature variation.

5.References:

[1]. Delerue C and Lannoo M 2004 Nanostructures: Theory and Modeling (Berlin: Springer) [2]. Harrison P 2010 Quantum Wells, Wires and Dots: Theoretical and Computational Physics of Semiconductor Nanostructures (3rd edn.) (UK: Wiley) [3]. A. B. ,Dzyubenko and A. L. Yablonskii, Phys. Rev. B, 53 (1996) 16355. [4]. A.J. Peter, K. Navaneethakrishnan, Superlatt.Microstruct. 43 (2008) 63. [5]. G. Bastard, Phys. Rev. B 24 (1981) 4714. [6]. J.H. Burnett, H.M. Cheong, W. Paul, E.S. Koteles, B. Elman, Phys. Rev. B 47 (1993) 1991.

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ACCEPTED MANUSCRIPT [7]. A.M. Elabsy, Superlatt. Microstruct. 14 (1993) 65. [8]. A.M. Elabsy, J. Phys.: Condens. Matter 6 (1994) 10025. [9]. A.L. Morales, A. Montes, S.Y. L´opez, C.A. Duque, J. Phys.: Condens. Matter 14 (2002) 987. [10]. E.C. Niculescu, L.M. Burileanu, A. Radu, Superlatt.Microstruct. 44 (2008) 173

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[11]. E. Kasapoglu, Phys. Lett. A 373 140 (2008) 140. [12]. M. A. Gell, D. Ninno, M. Jaros, D. J. Wolford, T. F. Keuch, and J. A. Bradley Phys. Rev. B 35 (1987) 1196.

[13]. P. Pfeffer and W. Zawadzki, J. Appl. Phys. 111 (2012) 083705.

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[14]. Gh. Safarpour, A. Jamasb, M. Dialameh, S. Yazdanpanahi, Superlattices and Microstructures 76 (2014) 442.

[15]. P. Başer, I. Altuntas, S. Elagoz, Superlattices and Microstructures 92 (2016) 210.

Jap.aip.org. Retrieved 2013-12-02.

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[16]. "Scitation: Electron mobility and energy gap of In0.53Ga0.47As on InP substrate".

[17]. T.P. Pearsall and J.P. Hirtz, J. Cryst. Growth 54 (1981) 127.

[18]. "IEEE Xplore - Ga0.47In0.53As: A ternary semiconductor for photodetector applications". Ieeexplore.ieee.org. doi:10.1109/JQE.1980.1070557. Retrieved 2013-12-

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02.

[19]. T.P. Pearsall, R. Bisaro, R. Ansel and P. Merenda, Appl. Phys. Lett. 32 (1978) 497. [20]. M. Razeghi, J. P. Hirtz, D. Ziemelis, C . Delalande, B. Etienne and M. Voos, Appl. Phys. Lett. 43 (1983) 585.

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[21]. M. Razeghi, J. Nagle and C. Weisbuch 1985 Gallium Arsenide and Related Compounds 1984 (Inst. Phys. ConJ Ser. 74) 319. [22]. J. H. Marsh, J. S. Roberts and P. A. Claxton, Appl. Phys. Lett. 46 (1985)1161.

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[23]. F. Capasso, K. Mohammed, A.Y., Cho, R. Hull and A. L. Hutchinson, Appl. Phys. Lett. 47 (1985) 420.

[24]. K. S. Seo, Y. Mashimoto, P. K. Bhattacharya and K. R. Gleason Proc. Int. Electron Devices Meeting, Washington, DC (1985) 321. [25]. K. Wakita, Y. Kawamura, Y. Yoshikuri and H. Asahi, Electron. Lett. 21 (1985) 514. [26]. J. S. Weiner, D. S. Chemla, D. A. B. Miller, T. H. Wood, D. Sivco and A. Y. Cho, Appl. Phys. Lett. 46 (1985) 619. [27]. M S Skolnick, P R Tapster, S J Bass, A D Pitt, N Apsley and S P Aldred, Sernicond. Sci. Technol. 1 (1986) 29. [28]. D. E. Aspnes, Phys. Rev. B 24 4714 (1981) 4714.

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ACCEPTED MANUSCRIPT [29]. S. Adachi Properties of Group IV, III-V and II-VI Semiconductors. [30]. P. Baser, H.D. Karki, I. Demir, S. Elagoz, Superlatt. Microstruct. 63 (2013) 100. [31]. S. Paul, J.B. Roy, P.K. Basu, J. Appl. Phys. 69 (1991) 827. [32]. H.M. Baghramyan, M.G. Barseghyan, A.A. Kirakosyan, J. Phys. Conf. Ser. 350 (2012) 012017.29.

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[33]. S. Chaudhuri, Phys. Rev. B 28 (1983) 4480. [34]. P. Baser, H.D. Karki, I. Demir, S. Elagoz, Superlatt. Microstruct. 63 (2013) 100. [35]. S. S. Parashari, S. Kumar, S. Auluck, Solid-State Electronics 52 (2008) 749.

[36]. Abdel Razik Degheidy, Sayed Abdel Aty Elwakil, Elkenany Brens Elkenany, Journal of Alloys

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and Compounds 574 (2013) 580.

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P(GPa)

,



change in ∆

Relative ,

,

change in ∆



,

Relative

,

change in

meV

13.8

0%

0.04

0%

208

5

13.2

-4%

0.06

50%

169

10

12.7

-8%

0.07

75%

129

12

12.5

-9%

0.08

100%

113



,

change in ∆

0%

1.00

0%

-19%

0.97

-3%

-38%

0.95

-5%

-46%

0.94

-6%

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0



Relative

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Relative

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Table 1: The variation of dielectric constant, effective mass ( ∗ , for Ga0.47In0.53As), potential height and well width, with hydrostatic pressures and their percentile changes for T = 300 K (where relative change in A is defined as ∆ , = , − ,0 ⁄ ,0 .

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Relative change in

,

T(K)





,

0,

Relative



change in

meV)

,



Eb (meV)

, 0%

15.5

13.5

0%

0.04

203

50

13.6

0%

0.04

204

100

13.6

0%

0.04

204

150

13.6

1%

0.04

205

200

13.7

1%

0.04

206

1%

15.6

250

13.7

2%

0.04

207

2%

15.6

300

13.8

2%

0.04

208

2%

15.6

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0

15.5

0%

15.5

1%

15.6

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0%

Table 2: The variation of dielectric constant, effective mass, potential height and binding energy with temperature for P = 0 GPa and L=0.14aB (where relative change in A is defined as ,



,0 ⁄

, 0 ).

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=

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,

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2,4 2,2

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Eb/RB

2,0 1,8 1,6

P=0Gpa P=5Gpa

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1,4

P=10Gpa

1,2

P=12Gpa

1,0 0,4

0,6

0,8

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0,2

1,0

1,2

L(P)/aB

Figure 1. On-center ground-state hydrogenic impurity binding energy as a function of the well

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EP

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width at T=300 K and P=0, 5, 10 and 12 GPa.

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2500

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Eg (meV)

2000

1500

Eg(InP) Eg(InGaAs) (EgInP-EgGaInAs)

1000

0 2

4

6

8

10

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P(GPa)

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500

12

Figure 2: Energy band gaps of InP, InGaAs and their difference as a function of hydrostatic

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EP

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pressure at T=300 K for L(P)=0.2aB

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Figure 3. Percentile changes for (a) dielectric constant (b) potential height, (c) effective mass, vs

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EP

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P and T for an on-center impurity.

ACCEPTED MANUSCRIPT •

The ground state impurity binding energy decreases with the hydrostatic pressure

which

is

just

the

opposite

of

what

is

found

for

AlGaAs/GaAs/AlGaAs and GaAs/InGaAs/GaAs systems. •

The binding energy dependency due to well width is found similar to the AlGaAs/GaAs/AlGaAs and GaAs/InGaAs/GaAs systems. The ground state binding energy is very stable for a temperature range of 0-

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300 K.