Effects of spacer growth temperature on the optical properties of quantum dot laser structures

Electroluminescence (EL) and its temperature dependence of InAs quantum dots embedded in In0.15Ga0.85As quantum well [dots in a well (DWELL)] have been investigated as functions of the growth temperature of the GaAs spacer layer. The EL intensity at room temperature increases as the spacer growth temperature increases. The integrated EL intensity as a function of injection current at room temperature for all samples shows that at low currents, the gradients are superlinear but this superlinearity decreases as the spacer growth temperature is increased. From a simple analysis of the generation-recombination rate equations, it can be shown that the superlinearity stems from the nonradiative recombination being the dominant recombination process. As the spacer growth temperature is increased, this nonradiative recombination become less dominant. An Arrhenius plot of the temperature dependence of the EL intensity gives an activation energy of ~300 ± 15 meV at high temperature. The dominant loss mechanism is therefore concluded to be the electron escape from the quantum dot ground state to the GaAs barrier.