Superlattices and Microstructures 47 (2010) 103–107 Contents lists available at ScienceDirect Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices Band-mixing and strain effects in InAs/GaAs quantum rings B. Lassen ∗ , M. Willatzen, D. Barettin The University of Southern Denmark, The Mads Clausen Institute, Alsion 2, 6400 Sonderborg, Denmark article info Article history: Available online 8 September 2009 Keywords: Semiconductors Confined systems Quantum rings Band-mixing Strain and piezoelectric effects Absorption abstract We analyze for the first time the coupled influence of band mixing, strain, and piezoelectricity on electronic structure, eigenstates, and optical transition strengths for InAs/GaAs quantum-ring structures. It is shown that band mixing and strain alter the level energies and optical absorption coefficients significantly. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Within the expanding area of nanoscale semiconductor heterostructures of varying shape and size, quantum rings have recently received much attention. In particular, this is due to the observation of the Aharonov–Bohm effect in these structures [1]. Nowadays, it is possible to grow quantum rings with a rather uniform size distribution [2] and some unusual excitation effects [3] have been observed. In the present work, we address InAs/GaAs quantum ring structures characterized by a small bandgap where, in effect, band mixing is expected to be more important. Several theoretical investigations focus on magnetic and/or spin-related effects [4]. To our knowl- edge, the effects of strain and band mixing between the conduction band and the valence bands have so far not been take fully into account. It is well known, however, that especially for narrow bandgap materials, band-mixing effects have a strong impact on the energy spectrum and wavefunctions lead- ing to significant changes in optical properties. In particular, intriguing coupling effects can occur for the upper valence structure and states when combining the effects of strain and band mixing [5]. In this work, we study the importance of band-mixing effects for InAs/GaAs quantum rings. This is done by comparing electronic structure of the lower-conduction and upper-valence states based on a two + six-band model and an eight-band k · p model. In both approaches the effects of strain ∗ Corresponding author. Tel.: +45 65501687. E-mail address: benny@mci.sdu.dk (B. Lassen). 0749-6036/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.spmi.2009.08.005