CHARGE NEUTRALITY VIOLATION IN QUANTUM-DOT LASERS

Theory of quantum-dot (QD) lasers is augmented to include, in a self-c onsistent manner, the QD-layer charge, The electron- and hale-level oc cupancies in QD's are obtained through the solution of the problem for the electrostatic-field distribution across the junction. They are sh own to differ from each other, As a result, the local neutrality is br oken down in each QD, i.e., the QD layer Is charged, The key dimension less parameters controlling the difference of the hole- and electron-l evel occupancies are revealed, The detailed analysis of the gain and s pontaneous radiative recombination current density is Siren, having re gard to the bet of violation of the charge neutrality in QD's, The gai n-current density dependence is calculated, The voltage dependences of the electron- and hole-level occupancies, gain, and current density a re obtained, Particular emphasis is given to the transparency and lasi ng threshold characteristics. Optimization of the QD-laser structure i s carried out. The optimum surface density of QD's, minimizing the thr eshold current density, is shown to be distinctly higher than that cal culated without regard for the lack of the charge neutrality in QD's.