H− ion implantation induced ten-fold increase of photoluminescence efficiency in single layer InAs/GaAs quantum dots

We demonstrate a ten-fold increase in photoluminescence (PL) efficiency from 50 keV H- ion-implanted InAs/GaAs quantum dots (QDs) at a temperature of 8 K and/or 145 K. Enhancement occurred without post-annealing treatment. PL efficiency increased with increasing implantation fluence from 6 x 10(12) ions/cm(2) up to an optimum value of 2.4 x 10(13) ions/cm(2), beyond which PL efficiency decreased drastically (up to a fluence of 2.4 x 10(15) ions/cm(2)). Passivation of non-radiative recombination centres (due to direct interaction of H- ions with lattice defects) and de-excitation of photo-generated carriers to QDs through quantum mechanical tunnelling via H- ion-induced defects (e-traps) that are created near the QD-cap layer interface, resulted in PL efficiency enhancement. Shallow e-traps with activation energy similar to 90 meV and 30 meV created near the conduction band of GaAs cap layer for the samples implanted with H- of fluence 6 x 10(12) and 2.4 x 10(13) ions/cm(2) respectively are identified using low temperature PL study. Contribution of de-trapped electrons from the e-traps to the QDs enhanced the PL efficiency at 145 K. Cross-section transmission electron microscopy and X-ray diffraction study revealed that the structural damage created by H- ions at the high fluence level of 2.4 x 10(15) ions/cm(2), caused the degradation in PL efficiency. (C) 2014 Elsevier B.V. All rights reserved.