Variational results for electron mobility in modulation-doped In 0.53 Ga 0.47 As/InP single symmetric quantum wells F.M.S. Lima a, * , A.B. Veloso a , A.L.A. Fonseca a , O.A.C. Nunes a , E.F. da Silva Jr b a Instituto de Fı ´sica, Universidade de Brası ´lia, P.O. Box 04455, 70919-970 Brası ´lia-DF, Brazil b Departamento de Fı ´sica, Universidade Federal de Pernambuco, 50670-901 Recife-PE, Brazil Available online 26 May 2005 Abstract In this paper, the low-field carrier mobility is investigated for quasi-2D electrons in a n-doped In 0.53 Ga 0.47 As/InP single symmetric quantum well. An accurate variational scheme is developed in view to determine the subband structure in this lattice-matched heterostructure. In this scheme, the Schro ¨dinger–Poisson coupled equations are solved observing adequate matching conditions at the heterointerfaces, as well as exchange-correlation corrections to the Hartree potential. The results allowed us to compute the main scattering rates. Some interchanges in these scattering rates were found with respect to the limitation of electron mobility by varying the well and the spacer widths. q 2005 Elsevier Ltd. All rights reserved. Keywords: Quantum wells; InGaAs/InP; Alloy scattering; Electron mobility 1. Introduction The III–V semiconductors form a very important class of material for electronic and optoelectronic devices and circuits [1]. The evolution of epitaxial growth techniques for heterostructures involving such compounds has allowed an excellent control on both composition and doping, furnishing high-quality samples with almost abrupt heterointerfaces and doping profiles [2]. In fact, GaAs/ Al x Ga 1Kx As quantum heterostructures have been the leader in the search for high carrier mobility in semiconductors [3], but the use of n-doped Al x Ga 1Kx As as supply layers has some inconveniences for high-speed device applications, e.g. deep levels, interface states, and gate leakage [4]. These unwanted effects have been overcome by growing Al-free heterostructures, the choice of the compounds being decisive since it has direct impact on the device performance [5]. For instance, In 0.53 Ga 0.47 As/InP modulation-doped heterostruc- tures are of great interest since it treats of a lattice-matched (unstrained) structure and also due to the negligible concentrations of DX centers and dislocations on the InP donor layers [6]. As compared to In 0.52 Al 0.48 As, another important alloy that lattice-matches to In 0.53 Ga 0.47 As, the InP supply layers present a larger separation between G and L valleys (w0.63 in comparison to w0.34 eV), which reduces the probability of activation of DX-like centers and also lowers the hot carriers transfer between the channel and the doped layers [7]. However, the attainment of high carrier mobility in InGaAs/InP heterostructure-based devices has been hindered by alloy disorder (ALLOY) scattering of carriers in the In 0.53 Ga 0.47 As channel. To the authors knowledge, ALLOY scattering has always been considered as the main scattering mechanism in mobility limitation in the literature. Since electron mobility is the quantity that dictates the speed of modern electronic devices, we decided to investigate here in this work, the possibility of other scattering mechanisms come to limit the mobility in In 0.53 Ga 0.47 As/InP modu- lation-doped quantum wells (QWs). For this, we developed an accurate and flexible variational scheme for calculating the electronic subband structure in modulation-doped QWs whose doping profile is symmetric with respect to the QW center, thus forming a single symmetric QW (SSQW). The interface roughness (IR) scattering, dominant in thin GaAs/Al x Ga 1Kx As SSQWs [8,9], was investigated in view to identify the well width below which it becomes dominant. The possibility of remote ionized impurity (II) scattering to Microelectronics Journal 36 (2005) 1016–1019 www.elsevier.com/locate/mejo 0026-2692/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.mejo.2005.04.008 * Corresponding author. Tel.: C55 61 307 2900x312; fax: C55 61 3074 2363. E-mail address: fabio@fis.unb.br (F.M.S. Lima).