Carrier Recombination Properties of Low-Threshold 1.3 μm Quantum Dot Lasers on Silicon

On-chip lasers are a key component for the realization of silicon photonics. The performance of silicon-based quantum dot (QD) devices is approaching equivalent QDs on native substrates. To drive forward design optimization we investigated the temperature and pressure dependence of intrinsic and modulation p-doped 1.3 μm InAs dot-in-well (DWELL) laser diodes on on-axis silicon substrates for comparison with devices on GaAs substrates. The silicon-based devices demonstrated low room temperature (RT) threshold current densities (J _th ) of 192 Acm ^-2 (538 Acm ^-2 ) intrinsic (p-doped). Intrinsic devices exhibited temperature stable operation from 170-200 K. Above this, J _th increased more rapidly due to increased non-radiative recombination. P-doping increased the temperature at which J _th (T) started to increase to 300 K with a temperature insensitive region close to RT, but with a higher J _th . A strong correlation was found between the temperature dependence of gain spectrum broadening and the radiative component of threshold J _rad (T). At low temperature this is consistent with strong inhomogeneous broadening of the carrier distribution, which is more pronounced in the p-doped devices. At higher temperatures J _th increases due to homogeneous thermal broadening coupled with non-radiative recombination. Hydrostatic pressure investigations indicate that while defect-related recombination dominates, radiative and Auger recombination also contribute to J _th .