Negative characteristic temperature of long wavelength In As ∕ Al Ga In As 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 110 to 140 K . 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.