Simultaneous effects of pressure and laser field on donors in GaAs/Ga 1x Al x As quantum wells N. Eseanu à , E.C. Niculescu, L.M. Burileanu Department of Physics, ‘‘Politehnica’’ University of Bucharest, 313 Splaiul Independentei, RO-060042 Bucharest, Romania article info Article history: Received 17 February 2009 Received in revised form 2 April 2009 Accepted 3 April 2009 Available online 16 April 2009 PACS: 71.55.EQ 73.21.Fg Keywords: Quantum well Hydrogenic impurity Binding energy Hydrostatic pressure Laser field abstract Within the framework of effective-mass approximation, using a variational method, the combined effect of the hydrostatic pressure and high-frequency laser field on the binding energy of a hydrogenic impurity in square and parabolic GaAs/Ga 1x Al x As quantum wells is investigated. Our numerical results show that the effects of the laser field on the electronic properties are more pronounced than those of the pressure ones, and the changes in the binding energy are dependent on the shape of the confinement potential. The variations of the impurity binding energy in intense laser fields can be tuned by the hydrostatic pressure. & 2009 Elsevier B.V. All rights reserved. 1. Introduction The impurity plays a fundamental role in some physical properties such as optical and transport phenomena of semi- conductor nanostructures at low temperature. There was a great interest of experimental and theoretical research on the pressure and external field influence on the physical properties of bulk and low-dimensional-doped semiconductors [1–8]. Since GaAs/Ga 1x Al x As quantum well (QW) structure has been applied in modern high-speed electronic and photoelectronic devices, the pressure and external field dependence of the optical and electric properties in the related systems have been extensively investigated. Ban and Liang [9] have studied the binding energy of a donor near the interface of a GaAs/Ga 1x Al x As heterojunction under hydrostatic pressure. They developed a variational method and considered the influence of a realistic interface potential. Zhao et al. adopted a variational method to calculate the binding energy of a donor in a QW structure with finite barriers under hydrostatic pressure and found that the donor binding energy monotonically increases with pressure in the region from 0 to 40 kbar [10]. By considering the G–X crossover in the GaAlAs region it was reported, as general feature, a linear dependence of the binding energy in the direct gap regime on the applied pressure, while in the indirect gap regime the energy grows with the pressure until reaching a maximum and then it decreases [11–14]. Oyoko et al. [15] have calculated the effect of hydrostatic pressure and temperature on shallow- impurity-related optical absorption spectra in GaAs/GaAlAs single and double quantum wells. Peter and Navaneethakrishnan [16] have calculated the binding energies of donors in GaAs/GaAlAs single quantum well as a function of the pressure and tempera- ture. Recently, the combined effect of hydrostatic pressure and temperature on donor impurity binding energy in GaAs/Ga 0.7 Al 0.3 As double quantum well in the presence of the electric and magnetic fields applied along the growth direction have been studied by using a variational technique within the effective-mass approximation [17]. A lot of studies have been carried out about quantum wells under intense electric fields created by high-intensity THz lasers. Neto and Qu [18] have derived the laser-dressed quantum well potential for an electron in a square quantum well (SQW), in the frame of a non-perturbation theory and a variational approach. A simple scheme based on the considered effect of the laser interaction with the semiconductor through the renormalization of the effective mass has been proposed by Brandi and Jalbert [19]. Ozturk et al. [20] have investigated the effect of the laser field on ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physe Physica E 1386-9477/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.physe.2009.04.001 à Corresponding author. Tel.: +40 214 029 321. E-mail address: nicoletaeseanu@yahoo.com (N. Eseanu). Physica E 41 (2009) 1386–1392