Effects of growth temperature of partial GaAs cap on InAs quantum dots in In-flush process for single dot spectroscopy

We have investigated effects of growth temperature of partial GaAs cap (T_cap) on InAs quantum dots (QDs) in indium-flush (In-flush) process with atomic force microscopy (AFM) and micro photoluminescence (μ-PL) measurements. T_cap in In-flush process are varied from 385 °C to 485 °C as an experimental parameter. In order to investigate the effects of T_cap on structural property of single InAs QD, shape of QD in initial capping process are characterized by AFM measurements in air at room temperature. While isotropic shape of QDs is kept in low T_cap conditions below about 440 °C, in-plane anisotropy of initial shape of QDs are increased with increasing of T_cap due to elongation to the [1̄0] direction. μ-PL measurements are performed at 7K for the investigation of the effects of T_cap on optical property in single InAs QDs. In low T_cap conditions from 410 °C to 435 °C, distinct emissions from excitonic states in single QDs are observed. In the same T_cap range, the AFM result shows that isotropic shape of QDs is kept. On the other hand, in high T_cap conditions above about 440 °C, indefinite peaks and broad emissions appear remarkably. Excitonic emissions which are observed in low T_cap range are hardly observed in this high T_cap range.