Strain tensor, electronic spectra and carrier dynamics in In(Ga)As/GaAs self-assembled quantum dots

The strain tensor in pyramidal Ga(In)As/GaAs self-assembled quantum dots is characterized in detail using a valence force field model and is applied to an eight-band k·p formalism to find the electronic spectra in the highly strained dots. Results obtained for the conduction band spectra using the effective mass approach are shown to have serious errors. The energy difference between the ground and excited states obtained from both eight-band calculations and experimental results indicates phonon bottleneck in these dots which is confirmed by a relatively simple high frequency electrical impedance measurements on quantum dot lasers. The electron capture times of 30-40 ps are obtained compared to 2-5ps in SCH quantum well lasers and 1 ps in tunneling injection lasers, and the modulation band width is found to be limited by the capture times. The time resolved photoluminescence measurements gave decay time constants of ~700 ps and ~200-250 ps for the ground and excited state transitions, respectively