BRIEF COMMUNICATION Insight into optical properties of strain-free quantum dot pairs Jiang Wu • Zhiming M. Wang • Vitaliy G. Dorogan • Yuriy I. Mazur • Shibin Li • Gregory J. Salamo Received: 18 September 2010 / Accepted: 30 December 2010 / Published online: 25 January 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Self-assembled GaAs/AlGaAs quantum dot pairs (QDPs) are grown by molecular beam epitaxy using high temperature droplet epitaxy tech- nique. A typical QDP consists of dual-size quantum dots as observed based on atomic force microscopy image. The average height of quantum dot is 5.7 nm for the large quantum dots and 4.6 nm for the small ones. The average peak-to-peak distance of the two dots is about 75 nm. The optical properties of GaAs QDPs are studied by measuring excitation power- dependent and temperature-dependent photolumines- cence. Unique photoluminescence properties have been observed from both excitation power-dependent and temperature-dependent measurements. Excitation power-dependent as well as temperature-dependent PL measurements have suggested lateral exciton transfer in the QDPs. Keywords Droplet epitaxy Á Quantum dot pairs Á Photoluminescence Á Molecular beam epitaxy Abbreviations QD Quantum dot QDM Quantum dot molecule PL Photoluminescence S–K Stranski–Krastanow QDP Quantum dot pair AFM Atomic force microscopy Introduction Coupled semiconductor quantum dots (QDs) or the simplest form of quantum dot molecules (QDM) has attracted considerable attention due to their interesting fundamental properties and potential applications for quantum computing devices (Livermore et al. 1996; Stinaff et al. 2006; Li et al. 1996; Li and Xia 2007). Substantial advancements have been achieved on the fabrication as well as probing the fundamental prop- erties of self-assembled coupled QDs (Ledentsov et al. 1996; Li and Xia 1997; Wang et al. 2006; Yamagiwa et al. 2006; Liang et al. 2008; Pomraenke et al. 2008; Wang et al. 2008; Wu et al. 2010; Hanke et al. 2006; Lee et al. 2006). Recently, fabrication of laterally aligned quantum dots and molecules has been pro- posed in several works (Ledentsov et al. 1996; Wang et al. 2006; Yamagiwa et al. 2006; Lee et al. 2006). Laterally aligned self-assembled QDs have been grown either by the conventional Stranski–Krastanow (S–K) mode or droplet epitaxy technique (Ledentsov et al. 1996; Wang et al. 2006; Yamagiwa et al. 2006). The latter method has shown great potential to achieve well controlled and high-quality QDMs. The laterally J. Wu Á Z. M. Wang (&) Á V. G. Dorogan Á Y. I. Mazur Á S. Li Á G. J. Salamo Arkansas Institute for Nanoscale Materials Science and Engineering, University of Arkansas, Fayetteville, AR 72701, USA e-mail: zmwang@uark.edu 123 J Nanopart Res (2011) 13:947–952 DOI 10.1007/s11051-010-0219-5