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 6×1012 ions/cm2 up to an optimum value of 2.4×1013 ions/cm2, beyond which PL efficiency decreased drastically (up to a fluence of 2.4×1015 ions/cm2). 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 ~90 meV and 30 meV created near the conduction band of GaAs cap layer for the samples implanted with H− of fluence 6×1012 and 2.4×1013 ions/cm2 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 2.4×1015 ions/cm2, caused the degradation in PL efficiency.