Hindawi Publishing Corporation Journal of Nanotechnology Volume 2013, Article ID 302647, 5 pages http://dx.doi.org/10.1155/2013/302647 Research Article Electronic Properties and Density of States of Self-Assembled GaSb/GaAs Quantum Dots T. Nowozin, 1 A. Wiengarten, 1 L. Bonato, 1 D. Bimberg, 1,2 Wei-Hsun Lin, 3 Shih-Yen Lin, 3 M. N. Ajour, 4 K. Daqrouq, 4 and A. S. Balamesh 4 1 Institut f¨ ur Festk¨ orperphysik, Technische Universit¨ at Berlin, Hardenbergstraße 36, 10623 Berlin, Germany 2 King Abdulaziz University, Jeddah 21589, Saudi Arabia 3 Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan 4 Electric and Computer Engineering Department, King Abdulaziz University, Jeddah 21589, Saudi Arabia Correspondence should be addressed to T. Nowozin; nowozin@sol.physik.tu-berlin.de Received 1 July 2013; Accepted 30 July 2013 Academic Editor: Xiao Wei Sun Copyright © 2013 T. Nowozin et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te electronic properties of a self-assembled GaSb/GaAs QD ensemble are determined by capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS). Te charging and discharging bias regions of the QDs are determined for diferent temperatures. With a value of 335 (±15) meV the localization energy is rather small compared to values previously determined for the same material system. Similarly, a very small apparent capture cross section is measured (1 ⋅ 10 −16 cm 2 ). DLTS signal analysis yields an equivalent to the ensemble density of states for the individual energies as well as the density function of the confnement energies of the QDs in the ensemble. 1. Introduction GaSb/GaAs quantum dots are an interesting material system due to their type-II band alignment with its exclusive hole confnement and a barrier present for electrons [1]. In par- ticular for charge storage applications, they are a promising option due to not only the very large barriers that can be achieved [2–5] but also the spatial separation of electrons and holes which facilitates long exciton lifetimes [6, 7] and could lead to interesting long-wavelength optoelectronic applications [8]. Although growth by metal organic vapor phase epitaxy (MOCVD) has been demonstrated [9, 10], the common way to fabricate these dots is molecular beam epitaxy (MBE) due to the peculiarities of Sb (i.e., smaller vapor pressure of Sb as compared to As, Sb crystal formation). For the use of GaSb/GaAs QDs in applications knowledge of their electronic properties is required. In this paper, we present an investigation of the electronic structure of GaSb/GaAs QDs. We analyze static as well as time-resolved capacitance-voltage (C-V ) measurements, in particular deep-level transient measurements (DLTS), in order to determine the key electronic properties, such as the activation energies, the localization energy, and the apparent capture cross sections of the QD ensemble. Te analysis of the DLTS signal yields an equivalent to the density of states of the QD ensemble for each individual energy. 2. Sample Te sample is grown by MBE. It consists of a layer of GaSb QDs embedded on the -side of a  diode. Te design allows to charge and discharge the QDs with holes in a controlled way. Te layer structure is the following: on top of an -doped GaAs substrate a 300 nm wide highly doped ( = 1 ⋅ 10 18 cm −3 ) layer is grown as back contact. Ten, a 500 nm wide -doped ( = 2 ⋅ 10 16 cm −3 ) layer is deposited, followed by 7 nm nominally undoped GaAs. On top of the undoped layer, 3 ML GaSb are deposited to form QDs with a growth interruption to prevent GaSb ring formation [11]. Details on the growth process can be found in [11, 12]. Te QD layer is covered by another 7 nm of undoped GaAs.