Optical Spectroscopic Study of Carrier Processes in Self-Assembled In(Ga)As-Ga(Al)As Quantum Dot Lasers

Carrier processes in InAs–GaAs self-assembled quantum dot lasers are investigated via the measurement of the temperature dependence of the current versus integrated spontaneous emission intensity. At high temperatures the rapid increase in threshold current is shown to be due to the non-radiative recombination of carriers at defects or impurities. At low temperatures the threshold current initially decreases with increasing temperature (negative-T0 regime), a behaviour previously attributed to a transition from a non-thermal to quasi-thermal carrier distribution within the dot ensemble. However, the optical results suggest a more complicated behaviour.