Photoluminescence of GaAsBi/GaAs quantum dots grown by metalorganic vapor phase epitaxy H. Fitouri n , K. Chakir, Z. Chine, A. Rebey, B. El Jani University of Monastir, Faculty of Sciences, Unité de Recherche sur les Hétéro-Epitaxies et Applications, 5019, Tunisia article info Article history: Received 4 February 2015 Accepted 27 February 2015 Available online 9 March 2015 Keywords: Epitaxial growth GaAsBi Luminescence abstract GaAsBi/GaAs nanostructure is successfully grown by metalorganic vapor phase epitaxy. The GaAsBi layer grown on a rough GaAs buffer surface is investigated in order to succeed the formation of quantum dots (QDs) structures. Photoluminescence (PL) measurements show signals from all QDs up to the room- temperature. The PL peak positions are nearly unchanged by varying measurement temperature, but relative intensity of some peaks has changed. In addition, the positions of these low temperature PL peaks slightly shift after annealing, although the QDs luminescence intensity has strongly affected. These results are considered to be related to the reduced size of the QDs and/or by Bi content changes in the QDs. & 2015 Elsevier B.V. All rights reserved. 1. Introduction The semiconductor alloy GaAsBi has attracts increasing interest in the last few years owing to their potential application in optoelec- tronic devices operating in the near to long infrared wavelength regions with enhanced capability [1]. GaAsBi are obtained by incor- porating a small amount of Bi in the host semiconductor resulting in a major reduction in the material band gap and a strong enhancement of the spin-orbit splitting [2,3]. The spin-orbit coupling influences the nature of bonding at high Bi content [4] . However, GaAsBi/GaAs structures have been proposed to be used for laser diodes in 1.3– 1.6 mm wavelength range to improve the operation efficiency and achieve temperature insensitivity [5]. Moreover, GaAsBi bulk material, GaAsBi/GaAs single quantum wells, GaAsBi/GaAs multiple quantum wells, and GaAsBi/AlGaAs have been grown at low temperatures using molecular beam epitaxy or metal-organic vapor phase epitaxy (MOVPE) [6–10]. The existence of bismuth atoms leads to a carrier localization effect at low temperatures and usually deteriorates the optical quality, thus affecting the performance of optoelectronic devices [11]. The emergence of the localized states in GaAsBi is attributed to the fluctuations of the alloy composition together with the clustering of Bi [12]. However, having quantum dots (QDs) instead of quantum wells as the active layer is expected to improve the performance of optoelectronic devices. In fact, the formation of Bi- containing QD-like clusters in annealed GaAsBi alloys grown at low temperature [13] has been recently identified. Moreover, because of the localization of carriers trapped at dislocations, QDs structures have been probably expected to increase the efficiency of the luminescence of semiconductor structures like in the case of QDs based on III–V compounds that consist of alloys such as InGaAs [14], InAsBi [15] and InGaN [16]. In this paper, we focus on the MOVPE growth of GaAsBi QDs, which is grown on a GaAs nanoholes buffer layer surface. The optical properties of the sample are investigated using photolu- minescence (PL). The low temperature PL changes after thermal annealing are also discussed. 2. Experimental The samples used in this study are grown on (001) p-GaAs substrates by atmospheric-pressure MOVPE. Trimethyl bismuth (TMBi), trimethyl gallium and pure arsine (AsH 3 ) is used as precursors. After annealing the substrate in a mixture flow H 2 and AsH 3 at 750 1C, the temperature decreases to 420 1C and a GaAs buffer layer was deposited. The growth of GaAsBi is then attempted by introducing a small flow of TMBi. In order to investigate the effect of the GaAs buffer layer on the GaAsBi layer, GaAsBi films were grown on both smooth and rough GaAs buffer surfaces. For growth of smooth GaAs buffer layer, the III/V ratio is set close to 9.5, while for growth of rough GaAs buffer layer, the III/V ratio increases to 26. This is followed by the growth of GaAsBi structure. The surface morphology of the GaAs buffer layer are analyzed by scanning electron microscopy (SEM). Post-growth thermal anneal- ing is performed in the growth reactor for 15 min under AsH 3 flow at 650 and 700 1C. Optical properties of the GaAsBi QDs are examined by PL using a He–Cd laser with the wavelength of 325 nm and a beam Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters http://dx.doi.org/10.1016/j.matlet.2015.02.131 0167-577X/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ216 73 500 274; fax: þ216 73 500 278. E-mail address: hedi.fitouri@fsm.rnu.tn (H. Fitouri). Materials Letters 152 (2015) 45–47