Electrical properties of InAs/InGaAs quantum-dot laser heterostructures: A threshold effect

We present differential current—voltage characteristics of InGaAs/GaAs laser structures with InAs quantum dots in a quantum well and without dots. In both cases, there is a drop in differential resistance at the lasing threshold, but in the case of the quantum-dot laser the drop is incomplete, without saturation of the voltage applied to the nonlinear part of the diode. The observed current voltage behaviour is interpreted qualitatively in terms of series-connected barriers (series barriers model).