1.3-micron high to quantum dot lasers based on charge-controlled active regions

The influence of p-type modulation doping on quantum dot laser performance is studied. Calculations and experimental data are presented to show that laser performance can be greatly enhanced by means of p-doping. A quasiequilibrium model that includes multiple discrete energy levels and the energy levels of the wetting layer is used to show that close energy spacing of the discrete hole levels can severely limit laser performance. The results of the calculations show that with moderate amount of p-doping used to introduce excess holes in the quantum dots, the differential gain and consequently laser frequency response can be dramatically improved. A simple calculation of the linewidth enhancement factor also shows that it can be positive, zero, or negative, with much smaller absolute values than a for a planar quantum well. The p-doping is also shown experimentally to increase the characteristic temperature of the quantum dot lasers. We show experimental data for p-doped lasers with characteristic temperature as high as 213K with CW operation.