The impact of <i>P</i>-type doping level and profile on performance of InAs quantum dot lasers

The impact of P-type doping level on InAs quantum dot (QD) lasers grown on GaAs (001) was investigated through the device performance characterization, i.e., measurements of threshold current, output slope efficiency, and temperature characteristics of lasers. The lasers are characterized under continuous wave operation with a ridge waveguide of 6 × 4000 μm2. In comparison to un-doped lasers, it has been demonstrated that an appropriate P-type doping level in the entire spacer can reduce the threshold current density of lasers from 215 to 86.8 A/cm2 for a doping concentration of 10 holes per QD at room temperature. Additionally, an improvement in output power slope efficiency from 0.108 to 0.191 W/A has been obtained, along with an enhanced characteristic temperature from 34.4 to 67.5 K (20–100 °C). Moreover, modulation doping has been explored to further reduce the threshold current density down to 77.9 A/cm2 at room -temperature and raise the output power, while entire spacer doping may enhance device performance at high operating temperatures. By optimization of P-type doping, remarkable enhancements in the performance of QD lasers can be achieved, which might have potential applications in cost-effective high-performance photonic integrated circuits.