Dry etching of anisotropic microstructures for distributed Bragg reflectors in AlGaInP/GaAs laser structures

A process for anisotropically etching AlGaInP/GaAs laser structures in a high-temperature (180 degrees C), single-step BCl(3)/Cl(2)/Ar plasma process is demonstrated. The etch rate is shown to be stable over the duration of the etch due to its insensitivity to temperature,. However, this etch. process is unsuitable for etching high-aspect-ratio features due to the strong aspect ratio dependence of the GaAs etch rate at 180 degrees C. A two-step etch where the GaAs is etched at 25 degrees C and the AlGaInP layers are etched at 180 degrees C is demonstrated that etches both materials anisotropically. The relative amount of Ar in the plasma has a strong effect on both the sidewall quality and the aspect-ratio-dependent etch rate. Finally, a process to etch anisotropic microstructures with a weak etch rate dependence on aspect ratio,is reported.