Performance improvement in quantum well lasers by optimizing band gap offset at quantum well heterojunctions

We analyze the influence of the band gap offset at the quantum well (QW) heterojunctions on the performance of QW lasers. It is shown that, in addition to the strain, optimization of the band gap offset also leads to improved performance in QW lasers, especially in enabling a simultaneous attainment of ultralow threshold current and high speed. The improvement stems from the reduction of state filling in the QW lasers since the asymmetry between the conduction band and the valence band structures in the optical confining region is compensated by the corresponding optimal band gap offset at the QW heterojunctions. The results provide general guidelines to the design of high performance of QW lasers as well as suggest applications to other active laser devices.