Effects of modulation p doping in InAs quantum dot lasers on silicon

We investigate, both experimentally and theoretically, the gain characteristics of modulation p-doped 1.3 μm quantum dot lasers epitaxially grown on silicon. Gain spectra and transparency points are measured for structurally identical lasers with varying levels of p doping in the active region. A many-body model is employed to facilitate understanding of the material gain characteristics. It has been found that appropriate p doping greatly reduces transparency and improves differential gain. It is also found that the improvements saturate with excessive doping because of the increase in nonradiative carrier recombination.