Technology CAD-based design of vertical-cavity surface-emitting lasers

Abstract

This work deals with the TCAD (technology computer aided design) based design of VCSEL (vertical-cavity surface emitting laser) devices. A comprehensive 2D electro-thermo-optical device model is presented. Furthermore, as examples, a micromechanical, electrostatically actuated vertical optical resonator is investigated, a procedure for optimising the higher order mode suppression in a VCSEL is presented, and a coupled electro-thermo-optical simulation of a VCSEL is performed. The laser device model employs the photon rate equation approach. It is based on the assumption that the shapes of the optical modes depend on the instantaneous value of the time-dependent dielectric function. The optical fields in the VCSEL cavity are expanded into modes obtained from the complex frequency representation of the homogeneous vectorial Helmholtz equation for an arbitrary complex dielectric function. The 3D problem is transformed into a set of 2D finite element (FE) problems by using a Fourier series expansion of the optical field in azimuthal direction. For the bulk electro-thermal transport a 2D thermodynamic model is employed in a rotationally symmetric body. Heterojunctions are modeled using a thermionic emission model. Quantum wells are treated as scattering centres for carriers. The optical gain and absorption model in the quantum well active region is based on Fermi's Golden Rule. The sub-bands in the quantum well are determined by solving the stationary effective mass Schroedinger equation with parabolic band approximation for the electrons, light and heavy holes.