Ion beam radiation effects on InAs semiconductor quantum dots
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Ion beam radiation effects on InAs semiconductor quantum dots J. Zhu, M. Thaik, M. Yakimov, S. Oktyabrsky, A. E. Kaloyeros and M. B. Huang Department of Physics and Institute of Materials Research and Applied Sciences, University at Albany, State University of New York, Albany, NY 12222 ABSTRACT Self-assembled quantum dots (QDs) have attracted significant attention because of their potential applications in novel semiconductor devices. In this work, we investigated radiation effects induced by 1.0 MeV proton ion beams on InAs self-assembled quantum dots. In particular, we emphasized the effects of lattice environments of QDs on their luminescence emission after ion beam irradiation. Photoluminescence (PL) spectroscopy was used to characterize the optical properties of QDs subjected to proton irradiation and post-irradiation annealing. Compared to the single-layer QDs grown in GaAs films, the QDs embedded in an AlAs/GaAs superlattice exhibited much higher PL degradation resistance to proton beam bombardment, e.g., at the highest dose (1.0×1014 cm-2) used in this work, a difference of ~ 20fold in PL intensity was found between the QDs configured in these two different lattice structures. After thermal annealing of irradiated QD samples, ion beam enhanced blueshift of PL was observed to be much more pronounced for the single-layer QDs. We discuss mechanisms that may result in the differences in optical response to ion beams between QDs with different lattice surroundings. INTRODUCTION Low-dimensional semiconductor systems have attracted much attention owing to their great potential in the fabrication of novel optoelectronic devices [1]. With the advent of modern deposition techniques (e.g. molecular beam epitaxy (MBE)), tremendous progress has been made in the growth of low-dimensional systems. Of particular interest is the zero-dimensional quantum dot (QD) structure where carriers can be spatially confined in three dimensions. The quantum confinement effects induce interesting modifications to the electrical and optical properties of materials, offering a new platform for semiconductor devices [2]. To optimize the fabrication of QD-based devices (e.g. low-threshold semiconductor lasers), it is important to understand ion beam radiation effects on these devices. During device fabrication processes, ion beams are frequently used to incorporate dopants into materials, generate device patterns or provide a means for electrical isolation. The degradation in luminescence emission from the QDs exposed to ion beams is therefore a concern. In addition, the knowledge of interactions between QDs and ion beams could aid in the use of ion beams for modifying the luminescence properties of QDs. Ion beam radiation effects on self-assembled InAs and InGaAs QDs were recently reported [3-6]. It was found that QD-based structures exhibit a dramatic enhancement in luminescence degradation resistance to ion beam bombardment, relative to quantum well (QW) structures. This was attributed to the highly localized states of carriers in QDs. On
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