Electrothermal Modeling of GaAs Nanoridge Laser Diodes

This article presents an electrothermal model for a InGaAs/GaAs quantum well (QW) nanoridge (NR) laser diode monolithically integrated in a Si photonics wafer. Heat conduction inside the laser is modeled using both the finite element (FE) method and the Boltzmann transport equation (BTE) for phonon transport. The BTE model captures nanoscale thermal effects and is used to calibrate the FE model, which captures large-scale effects, such as heat spreading in the Si substrate. Two methods are used to obtain the power distribution inside the laser: first, electrical TCAD simulation is carried out for the p-i-n structure and second, an equivalent electrical circuit is extracted from measurement data. The simulation results of the different thermal and electrical models are compared and finally experimentally validated using spectral measurements. We conclude that the simulated laser thermal resistance ${R}_{\text {th, {sim}}}={74}\pm {8}.{9}$ mm-K/W is in good agreement with the experiments ${R}_{\text {th, {exp}}}={78}.{2}\pm {15}.{2}$ mm-K/W; furthermore, the model predicts a local hot spot at the p-contact, which is a bottleneck for laser reliability. This insight will drive future design iterations.