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Revathi M.,Yadava College Coeducational Institute | John Peter A.,Government Arts and Science College
Solid State Communications | Year: 2010

Exciton states confined in a GaN/Ga1-xAlxN Quantum dot are investigated within the framework of single band effective mass approximation. Charged donor bound exciton, D+ X energy is computed as a function of dot radius for different Al concentration and the height of cylindrical dot. The interband optical transition of GaN/Ga1-xAlxN dot is calculated with the various structural parameters. The valence band anisotropy is included in our theoretical model by using different hole masses in different spatial directions. Binding energy of the ground state of exciton is calculated, with the inclusion of 2D Hartree dielectric screening function. Our results show that quantum size has a considerable influence on exciton states and interband optical transitions of the narrow dots. The ground state exciton binding energy and the interband emission energy are increased when the cylindrical quantum dot height or radius is decreased and the effect of exciton has influence on the interband emission energy. The donor bound exciton binding energy increases monotonically as Al concentration increases. Our results are compared with the existing available literature. © 2010 Elsevier Ltd. All rights reserved.


Joseph Sharkey J.,Control Electrochemical Research Institute | Yoo C.,Kyung Hee University | John Peter A.,Government Arts and Science College
Superlattices and Microstructures | Year: 2010

The binding energies of a hydrogenic donor in a GaN/AlGaN quantum dot are calculated in the influence of magnetic field. The calculations are carried out using the single-band effective mass approximation within a variational scheme. The magnetic field induced binding energy and diamagnetic susceptibility of the hydrogenic donor are obtained as a function of dot radius. Calculations have been carried out with and without the Zeeman effect through the energy-dependent effective mass. The diamagnetic shift of the hydrogenic donor is found for different dot radii. Our results show that (i) the binding energy is higher for smaller dot radii and the magnetic field effects are predominant for larger dot sizes, (ii) the binding energy is higher when the Zeeman effect is included for all the magnetic fields, (iii) the diamagnetic susceptibility increases with the magnetic field and is not pronounced for smaller dot radii and (iv) the diamagnetic shift has a good influence of larger dot radii. © 2010 Elsevier Ltd.


John Peter A.,Government Arts and Science College
Superlattices and Microstructures | Year: 2010

The binding energy of laser dressed donor impurity is calculated under the influence of a magnetic field in a quantum well. The binding energy of the ground state of a donor is investigated, within the single band effective mass approximation, variationally for different concentrations at the well centre. The effect of laser and magnetic fields on diamagnetic susceptibility of the hydrogenic donor is reported. The Landau energy levels of electrons in the quantum well as a function of magnetic field are reported. The results show that the diamagnetic susceptibility (i) decreases drastically as intensity of the laser field increases (ii) increases with the magnetic field strength (iii) decreases as the Al-concentration decreases and (iv) a variation of increase in binding energy is observed when non-parabolicity is included and this effect is predominant for narrow wells. Our results are in good agreement with previous investigations for other heterostructures in the presence of laser intensity. © 2009 Elsevier Ltd. All rights reserved.


Narayanan M.,Yadava College Govindarajan Campus | John Peter A.,Government Arts and Science College
Superlattices and Microstructures | Year: 2012

The effect of electric field on the binding energy, interband emission energy and the non-linear optical properties of exciton as a function of dot radius in an InSb/InGa xSb 1-x quantum dot are investigated. Numerical calculations are carried out using single band effective mass approximation variationally to compute the exciton binding energy and optical properties are obtained using the compact density matrix approach. The dependence of the nonlinear optical processes on the dot sizes is investigated for various electric field strength. The linear, third order non-linear optical absorption coefficients, susceptibility values and the refractive index changes of electric field induced exciton as a function of photon energy are obtained. It is found that electric field and the geometrical confinement have great influence on the optical properties of dots. © 2012 Elsevier Ltd. All rights reserved.


John Peter A.,Government Arts and Science College
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010

A systematic study of binding energy of the ground state of a hydrogenic donor in a quantum well is calculated in the presence of a uniform electric field for different measure of laser intensities. Binding energy of the ground state of a donor is calculated, within the effective mass approximation, with the Bessel and Airy functions. Polarizability of a laser dressed donor impurity in the presence of electric field is reported. It is observed that the polarizability (i) increases as intensity of the laser field increases (ii) increases with the electric field strength and (iii) increases drastically when both the fields are applied. The dependence of the donor binding energy on the well width, the laser field intensity and the electric field is discussed. Our results are in good agreement with the previous investigations for other heterostructures in the presence of laser intensity. © 2010 Elsevier B.V. All rights reserved.


El Ghazi H.,University Sidi Mohammed Ben Abdellah | John Peter A.,Government Arts and Science College
Solid State Communications | Year: 2015

The shallow-donor ground-state binding energy of wurtzite strained (In,Ga)N asymmetric coupled quantum wells (ACQW) is calculated. Within the effective-mass and the one-band parabolic approximations, the structure size, the composition of well and the barrier, the position of the impurity and the built-in electric field effects are investigated using a variational approach under finite confinement potential. The competition effect between the quantum confinement potential and the BEF is also shown. Our results reveal that the binding energy is the largest at a point corresponding to the maxima of the electron wave-function and a larger value is obtained compared to uncoupled QWs. Moreover, the principle effect of the BEF is to reduce the binding energy. It is established that the binding energy can be easily modulated by modifying the structure size, its constitution and the impurity's position. © 2014 Elsevier Ltd. All rights reserved.


Arunachalam N.,Government Hr. Sec. School | Peter A.J.,Government Arts and Science College | Yoo C.K.,Kyung Hee University
Physica Status Solidi (B) Basic Research | Year: 2012

The effect of electric-field strength on the binding energy of a hydrogenic impurity in an InAs/GaAs quantum wire is discussed. Calculations have been performed using Bessel functions as an orthonormal basis within a single-band effective-mass approximation. The electric-field-induced photoionization cross section of the hydrogenic impurity is investigated. The total optical absorption and the refractive-index changes as a function of normalized photon energy between the ground and the first excited state under the influence of an electric field are analyzed. The optical absorption coefficients and the refractive-index changes strongly depend on the incident optical intensity and the electric-field intensity. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Pattammal M.,Yadava College Coeducational Institute | Peter A.J.,Government Arts and Science College
Applied Surface Science | Year: 2010

Binding energies of ground and a few low lying excited states of a hydrogenic donor confined in a zinc-blende GaN/AlGaN quantum well are investigated. They are computed within the framework of single band effective mass approximation, by means of a variational approach. The donor states are investigated with the various impurity positions as a function of well width. The calculations have been carried out with the inclusion of conduction band non-parabolicity through the energy dependent effective mass. The variational solutions have been improved by using a two-parametric trial wavefunction. The results seem better and good agreement with the other investigators. To support our results, we observe that the values of variational parameters are consistent when two parameter wave function is used. We find that the inclusion of non-parabolic effects leads to more binding for all the values of well width and is significant for narrow wells. The results are compared with the existing available literature. © 2010 Elsevier B.V.


Bhandary M.J.,Government Arts and Science College | Chandrashekar K.R.,Mangalore University
Indian Journal of Traditional Knowledge | Year: 2011

Traditional herbalists of Coastal Karnataka were found to be practicing 34 different methods of treatment for herpes infection in which 57 species of local plants are used. A herbal paste prepared by grinding one or more herbal ingredients for repeated application on the lesions of the skin is the common formulation involved in all the recorded methods. A scrutiny of literature revealed that 25 of plant species used have antiviral and other antimicrobial properties. In addition, some plants are described as antiinflammatory, wound healing and coolants in the ethnomedicinal literature of India, a few of which have been scientifically ascertained. These facts provide an indirect scientific basis to the efficacy of the recorded treatment methods.


Arunachalam N.,Government Hr. Sec. School | Yoo C.,Kyung Hee University | Peter A.J.,Government Arts and Science College
Superlattices and Microstructures | Year: 2011

Magnetoexciton bound donor is investigated in a strained InAs/InP quantum wire within the framework of single band effective mass approximation. The strain contribution to the potential is determined via deformation potential theory. The interband optical transition is computed with the various structural parameters in the influence of magnetic field. © 2010 Elsevier Ltd. All rights reserved.

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