Fabrication of dry etched mirrors for In_0.20Ga_0.80As/GaAs waveguides using an electron cyclotron resonance source

High quality In_0.20Ga_0.80As/GaAs total internal reflecting mirrors have been demonstrated. The mirrors were fabricated by dry etching using a Cl₂/Ar plasma generated with an electron cyclotron resonance source. The etched mirrors have smooth sidewalls and vertical profile. Mirror reflectivities up to 93% have been measured. The mirror reflectivity has been studied as a function of etch conditions including ion energy and ion flux. The effects of etch profile on reflectivity were also investigated. It was found that the reflectivity of the etched mirrors was not sensitive to either the ion energy or the ion flux used for the etching. As long as a vertical profile and smooth surface morphology are maintained, the reflectivity remains at ∼90% even when high radio‐frequency power (200 W) and high microwave power (150 W) were used for etching. However, significant degradation of the mirror reflectivity to only 47% was found on mirrors with a slight undercut profile and rougher sidewalls. The results suggest that mirror reflectivity is much more sensitive to etch profile. Triangular ring lasers with etched mirrors were also fabricated, and threshold current as low as 3.7 mA has been demonstrated, showing the high quality of the etched mirrors.