International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 04 Special Issue: 09 | Sep -2017
p-ISSN: 2395-0072
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One Day International Seminar on Materials Science & Technology (ISMST 2017) 4th August 2017 Organized by
Department of Physics, Mother Teresa Women’s University, Kodaikanal, Tamilnadu, India
Effects of spatially dependent effective mass and non-parabolicity on hydrogenic impurity binding energy in a near triangular quantum well T. Subha Shree1, M. Arulmozhi2 1,2Department
of Physics, Jayaraj Annapackiam College for Women (Autonomous) Periyakulam 625601, Theni District, Tamilnadu, India. ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Low dimensional semiconducting systems like
quantum wells, wires and dots are extensively studied due to their applications in various fields. Near triangular quantum wells have attracted considerable attention of the researchers because of its applications such as speed circuits, optical devices etc. The effects of spatially dependent effective mass and nonparabolicity of conduction band on hydrogenic impurity binding energy in near triangular quantum well composed of GaAs/ Ga1-xAlxAs have been investigated by variational method as a function of wellwidth and Al concentration. The spatially dependent effective mass (SDEM) affects the hydrogenic impurity to be less bound than that without the SDEM. Nonparabolicity of conduction band affects the hydrogenic impurity to be less bound than that without the non-parabolicity. The observed results are compared with those available in the literature. Key Words: Quantum well, Hydrogenic impurity, Binding energy, Spatially dependent effective mass, Non-parabolicity.
1.INTRODUCTION
The binding energy of the ground state hydrogenic donor in Rectangular quantum well (RQW) has been calculated without [1] and with applied magnetic field [2]. The effect of a constant electric field on the energy position of the ground state exciton was studied in RQW [3]. The temperature dependence of the binding energy of shallow donors was reported in RQW [4]. The effect of non-parabolicity on hydrogenic donor binding energy in RQW was determined |
Qi et al [7] have calculated the effect of SDEM on hydrogenic impurity binding energy in a finite PQW as a function of wellwidth. Peter et al [8] have investigated the effects of both SDEM and DSF on hydrogenic donor binding energy in a quantum dot of GaAs/GaAlAs. Abarna et al [9] have theoretically studied the effects of dielectric screening function and image charges on hydrogenic donor binding energy in a surface quantum well made of vacuum/GaAs/Ga1-xAlxAs. In this paper, the effect of SDEM on the hydrogenic impurity binding energy in a NTQW formed by GaAs-AlxGa1-xAs have been calculated and the results are compared with the available data.
2. THEORY
The most significant nanostructures required to design nanoelectronic devices are Quantum Wells, Quantum Wires and Quantum Dots. In recent years, a great deal of interest has been shown in the properties of electron states in various quantum well structures. Experimental and theoretical researches have been made on the energies of electron states in a parabolic quantum well (PQW) with and without including the effect of spatially dependent effective mass (SDEM).
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without and with an applied magnetic field [5]. The effect of magnetic field on exciton binding energy in Near triangular quantum well (NTQW) composed of GaAs-AlxGa1-xAs has been calculated as a function of wellwidth and Al concentration [6].
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The Hamiltonian of hydrogenic impurity in a NTQW in the effective mass approximation can be written as [10] H=-
+ V (z) -
(1)
We have considered the growth axis of quantum well structures to be the z axis. , is the distance in x-y plane. The effective Rydberg R* is used as the unit of energy (R*=m*e4/2ħ2 o2) and the effective Bohr radius a* as the unit of length (a*= ħ2 o/m*e2), where m*is the effective mass of the electron. The potential profile for electron in NTQW is
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