The influence of quantum-well composition on the performance of quantum dot lasers using InAs/InGaAs dots-in-a-well (DWELL) structures

The optical performance of quantum dot lasers with different dots-in-a-well (DWELL) structures is studied as a function of the well number and the indium composition in the InGaAs quantum well (QW) surrounding the dots. While keeping the InAs quantum dot density nearly constant, the internal quantum efficiency eta (i), modal gain, and characteristic temperature of 1-DWELL and 3-DWELL lasers with QW indium compositions from 10 to 20% are analyzed. Comparisons between the DWELL lasers and a conventional In0.15Ga0.85As strained QW laser are also made. A threshold current density as low as 16 A/cm(2) is achieved in a 1-DWELL laser, whereas the QW device has a threshold 7.5 times larger. It is found that eta (i) and the modal gain of the DWELL structure are significantly influenced by the quantum-well depth and the number of DWELL layers. The characteristic temperature T-0 and the maximum modal gain of the ground-state of the DWELL structure are found to improve with increasing indium in the QW It is inferred from the results that the QW around the dots is necessary to improve the DWELL laser's eta (i) for the dot densities studied.