Removal of strain relaxation induced defects by flushing of InAs quantum dots

We report the effect of indium flushing on the electrical and optical properties of strain-relaxed InAs quantum dots (QDs) embedded in GaAs Schottky diodes. The InAs QDs were intentionally grown beyond the critical thickness to induce plastically relaxed QDs. The samples were fabricated by molecular beam epitaxy on GaAs(1 0 0) substrates using continuous and cycled InAs deposition. Deep level transient spectroscopy (DLTS) experiments show broad dislocation-induced defects in non-flushed samples. We show by DLTS that indium flushing after QD deposition decreases remarkably the amount of electron traps in the QD layer and suppresses the defect formation into GaAs capping layer. Using capacitance-voltage measurements we observed that the flushed samples exhibit a recovery of electron confinement in the QD states. Furthermore, we used photoluminescence experiments to analyse the effects of direct versus cycled InAs deposition and indium flushing steps.