Time Resolved Studies of Proton Irradiated Quantum Dots
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Time Resolved Studies of Proton Irradiated Quantum Dots Saulius Marcinkevičius Department of Microelectronics and Information Technology, Royal Institute of Technology, Electrum 229, 16440 Kista, Sweden Rosa Leon Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, U.S.A. Charlene Lobo Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, U.K. Brian Magness and William Taylor Department of Physics and Astronomy, California State University, Los Angeles, CA 90032, U.S.A. ABSTRACT The effects of proton irradiation on carrier dynamics were measured by time-resolved photoluminescence on InGaAs/GaAs quantum dot structures with different dot density and substrate orientation, as well as on InAlAs/AlGaAs quantum dots. Results were compared to irradiation effects on carrier dynamics in thin InGaAs quantum wells. We find that carrier lifetimes in QDs are much less affected by proton irradiation than in quantum wells, which can be attributed to the three-dimensional carrier confinement in quantum dots. INTRODUCTION Proton irradiation can induce structural defects and creates carrier-trapping centers in semiconductors. These defects have been used to an advantage when fabricating semi-insulating layers and ultrafast microwave devices. However, since protons have sufficient mass to cause displacement damage, their effects may be detrimental to the device performance when nonradiative carrier recombination is not desired, as is the case in most optoelectronic device applications. Studies of steady-state optical properties in proton-irradiated quantum dot (QD) structures [1] and in proton-irradiated QD lasers [2] showed that the QDs structures and QD based devices are much more resistant to irradiation than bulk semiconductors or quantum wells (QW). These studies showed not only better radiation tolerance, but also an increase in either photoluminescence (PL) intensities [1] or laser performance [3] with low proton or ion fluences. In the present work we have extended these investigations by studying carrier dynamics in irradiated QD structures. In order to obtain a better understanding of the effects of proton induced displacement damage on QD carrier dynamics, several types of structures were investigated: different materials compositions, surface QD densities, and substrate orientations. EXPERIMENTAL DETAILS InGaAs/GaAs (100), InAlAs/AlGaAs (100) and InGaAs/GaAs (311)B QDs were grown by metal-organic chemical-vapor deposition in a horizontal reactor cell operating at 76 Torr. Trimethylgallium, trimethylindium, trimethylaluminum (for growth of InAlAs and AlGaAs) and K11.6.1 Downloaded from https://www.cambridge.org/core. University of Arizona, on 27 Jul 2018 at 06:49:28, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-722-K11.6
Table I. Data summary for investigated QD and QW structures. Surface density (in dots/cm2)
Average diameter (nm)
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1 nm width
Average
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