TEMPERATURE-DEPENDENCE OF THE THRESHOLD CURRENT-DENSITY OF A QUANTUM-DOT LASER

Detailed theoretical analysis of the temperature dependence of thresho ld current density of a semiconductor quantum dot (QD) laser is given. Temperature dependences of the threshold current density components a ssociated with the radiative recombination in QD's and in the optical confinement layer (OCL) are calculated. Violation of the charge neutra lity in QD's is shown to give rise to the slight temperature dependenc e of the current density component associated with the recombination i n QD's, The temperature is calculated (as a function of the parameters of the structure) at which the components of threshold current densit y become equal to each other. Temperature dependences of the optimum s urface density of QD's and the optimum thickness of the OCL, minimizin g the threshold current density, are obtained. The characteristic temp erature of QD laser T-0 is calculated for the first time considering c arrier recombination in the OCL (barrier regions) and violation of the charge neutrality in QD's, The inclusion of violation of the charge n eutrality is shown to be critical for the correct calculation of T-0. The characteristic temperature is shown to fall off profoundly with in creasing temperature, A drastic decrease in T-0 is shown to occur in p assing from temperature conditions wherein the threshold current densi ty is controlled by radiative recombination in QD's to temperature con ditions wherein the threshold current density is controlled by radiati ve recombination in the OCL, The dependences of T-0 on the root mean s quare of relative QD size fluctuations, total losses, and surface dens ity of QD's are obtained.