Strategies for the Alignment of Electronic States in Quantum-Dot Tunnel-Injection Lasers and Their Influence on the Emission Dynamics

Tunnel injection (TI) lasers are an appealing concept for the next generation of<br/>semiconductor lasers, as they promise improved modulation rates and better temperature stability.<br/>Moreover, they eliminate a major detrimental effect of quantum dot (QDs) lasers,<br/>which is the gain nonlinearity caused by hot carriers.<br/>In QD-TI lasers, the excited charge carriers are efficiently<br/>captured from the bulk states via an injector quantum well and then transferred<br/>into the QDs via a tunnel barrier.<br/>The introduction of a tunnel barrier for controlling<br/>the coupling of QDs to an injector quantum well (QW) introduces significant<br/>design changes in comparison to conventional QD or QW lasers. As a result,<br/>nanoscale physics and quantum mechanical interaction processes take a more important<br/>role in the device properties.<br/>The alignment of the electronic levels<br/>is crucial for the high efficiency of these processes and especially for the fast<br/>modulation dynamics of these lasers. In particular, the quantum mechanical nature<br/>of the tunneling process must be taken into account in the transition from two-dimensional<br/>quantum well states to zero-dimensional quantum dot states. This results in hybrid states,<br/>from which the scattering into the QD ground states takes place. We combine<br/>electronic state calculations of the tunnel-injection structures with many-body<br/>calculations of the scattering processes and insert this into a complete laser simulator.<br/>This allows us to study the influence of the level alignment and limitations due to<br/>inhomogeneous quantum-dot distributions. We find that the optimal alignment deviates<br/>from a simple picture in which the of the quantum-dot ground state energies are one<br/>LO-phonon energy below the injector quantum well ground state.<br/><br/>We present [1] a theoretical study<br/>of dynamical laser properties inclusing the transport within the device and show the<br/>impact of alignment between the injector quantum well and the QDs on the laser switch-on<br/>process and modulation properties. These are important for the use of these laser<br/>systems in novel telecommunication applications.<br/><br/>[1] arXiv:2402.18165