Negative characteristic temperature of long wavelength InAs∕AlGaInAs quantum dot lasers grown on InP substrates

InAs quantum dot lasers grown on (311)B InP substrates with AlGaInAs barriers have been fabricated and studied. A large decrease of the threshold current with temperature was observed from 110to140K. In the same temperature range, electroluminescence spectra showed a shape change, an energy shift with temperature, which cannot be fitted with a Varshni law, and a large decrease of the laser linewidth. These results can be related to a delayed thermalisation of carriers within quantum dot ensemble.