Temperature and excitation dependence of photoluminescence from In 0.4Ga0.6As quantum dots on GaAs(001) substrates with large surface coverage

The photoluminescence (PL) measurements for In_0.4Ga_0.6As quantum dots (QDs) have been performed at different temperatures and excitations. The QD array is formed on GaAs(001) substrates and has a large surface coverage of ~90%. An unusual decrease of the PL linewidth with increasing temperature (for T<50 K) is found, This “abnormal” behaviour has been reported previously but no reasonable explanation is available up to now. Moreover, a slight increase followed by a dramatic decrease of the linewidth at higher temperatures (50-150 K) is observed for the first time. Different mechanisms including relaxation, dissociation and tunneling, which are responsible for the anomalies observed in the PL spectra are identified