Rate equation model of the negative characteristic temperature of InAs∕GaAs quantum dot lasers

The negative characteristic temperature of InAs∕GaAs quantum dot lasers is studied using a rate equation model. It is found that the decrease in the total contribution to lasing following a decrease in temperature is the reason for the occurrence of negative characteristic temperature in these lasers. The temperature corresponding to the occurrence of negative characteristic temperature is determined by the carrier escape rate from the quantum dots to the wetting layer or cap layer, carrier recombination lifetime, and rate of carrier loss due to deviation from (quasi-) Fermi equilibrium. The negative characteristic temperature in InAs∕GaAs quantum dot lasers does not occur under conditions of low carrier recombination lifetime and high quantum dot energy level occupation.