Finite Element Model Calculations of Temperature Profiles in Nd:YAG Laser Annealed GaAs/AlGaAs Quantum Well Microstructures

Infra-red (IR) laser induced selective-area quantum well intermixing (QWI) has the potential to yield multi-bandgap quantum well wafers suitable for the fabrication of monolithically integrated photonic devices. Quantitative description of the IR laser-QWI process requires knowledge of temporal and spatial temperature profiles induced by the laser. This requires solving a 3-dimensional heat diffusion equation, which takes into account laser parameters and the irradiation conditions. We report the results of modeling temperature profiles in semiconductor wafers irradiated with a stationary CW Nd:YAG laser beam (λ=1064 nm). The calculations were carried out using a finite element model and taking into account convection, background heating, as well as temperature dependent both heat conductivity and optical absorption. A reasonable agreement has been observed between calculated and measured temporal dependencies of the laser induced temperatures. Our calculations indicate that lines of the GaAs/AlGaAs QWI material could be 50% narrower than the diameter of the laser writing spot if the background temperature of the wafer is increased to about 700 °C.