Yazar "Ulas, M" seçeneğine göre listele
Listeleniyor 1 - 6 / 6
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Acceptor 1s-2p± transitions in GaAs/Ga0.7Al0.3As quantum wells(Wiley-V C H Verlag Gmbh, 1998) Akbas, H; Aktas, S; Okan, SE; Ulas, M; Tomak, MThe valence subband energies in the presence of an electric-field are calculated using the fourth-order Runge-Kutta method. The 1s- and 2p(+/-)-like acceptor states in the presence of a magnetic field are then calculated variationally. The effects of the spatially dependent screening function epsilon(r) on the calculation of the transition energies are specifically investigated. The use of a constant epsilon(o) is shown to yield better agreement with experimental results.Öğe Elecric field effect on the binding energy of a non-hydrogenic donor mpuirfty in a cylindrical cross-sectional quantum well wire(Wiley-V C H Verlag Gmbh, 2004) Ulas, M; Cicek, E; Dalgic, SSThe effect of an electric field on the non-hydrogenic binding energy of a shallow donor impurity in a cylindrical cross-sectional GaAs-(Ga,Al)As quantum well wire (QWW) was investigated. Within the effective mass approximation, the non-hydrogenic binding energy of the donor impurity was calculated by a variational method as a function of the wire radius, donor impurity position and applied electric field. The results show that the non-hydrogenic binding energy of the donor impurity located around the centre is larger than that of the hydrogenic binding energy. The difference in binding energy of an on-centre shallow donor impurity in the two regimes increases more rapidly with decreasing QWW radius than for other impurity positions. It has been found that the sensitivity of the donor binding energies to the applied electric field in both regimes is almost the same. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Öğe Electric field effect on the binding energy of a non-hydrogenic donor impurity in a square quantum well wire(Natl Inst Optoelectronics, 2005) Dalgic, S; Ulas, M; Ozkapi, BWe have used a variational technique to calculate the effect of an electric field on the non-hydrogenic binding energy of a donor impurity in a square GaAs/Ga1-x AlxAs quantum well wire (QWW). The non-hydrogenic binding energy of the donor impurity was calculated by the variational method as a function of applied electric field, the wire radius and donor impurity position. The results show that the non-hydrogenic binding energy of donar impurity located around the centre is larger than that of the hydrogenic binding energy. In this work, the variational method employed is capable of giving all the correct trends for impurity binding energies as a function of applied electric field, impurity position and screening effect.Öğe Screening effect on the binding energies of shallow donors, acceptors and excitons in finite-barrier quantum wells(Academic Press Ltd, 1998) Akbas, H; Aktas, S; Okan, SE; Ulas, M; Tomak, MThe conduction and valence subband energies in the presence of an electric field are calculated using the fifth-order Runge-Kutta method. The binding energies of shallow donors, accepters and excitons in finite-barrier GaAs/Ga1-xAlx As quantum wells are then obtained variationally in the presence of a magnetic field. The effects of a spatially dependent screening function epsilon(r) On the calculation of binding energies are specifically investigated. The use of epsilon(r) in comparison with the use of a constant epsilon(0) increases the binding energy of accepters as the increase on shallow donors and excitons is quite small. (C) 1998 Academic Press Limited.Öğe Self polarization in GaAs-(Ga, Al)As quantum well wires: electric field and geometrical effects(Elsevier Science Bv, 2005) Ulas, M; Erdogan, I; Cicek, E; Dalgic, SSThe response of an electron to an external electric field in different shapes of infinite quantum well wires has been investigated. The self-polarization effect which can be defined as the influence of the barrier potential on the impurity electron is studied for the quantum well wire of square, rectangular and cylindrical cross-sections. An external electric field vanishes due to the self-polarization effect has been calculated. It is shown that the self-polarization effect outside of the center depends on both the geometrical form of the wire and the impurity position in the same structure. (C) 2004 Elsevier B.V. All rights reserved.Öğe Shallow donors in a quantum well wire: Electric field and geometrical effects(Wiley-V C H Verlag Gmbh, 1997) Ulas, M; Akbas, H; Tomak, MSubband and shallow donor binding energies are calculated. The emphasis is given on the electric field effects for wires of different shapes. It is shown that the donor binding energy is sensitive to the interplay of the electric field and geometrical effects.
