Semiconductor etching methods

A method of etching into a one or more epitaxial layers of respective semiconductor material(s) in a vertical cavity surface emitting laser (VCSEL) semiconductor structure, wherein the or each semiconductor material is a III-V semiconductor material, a III-N semiconductor material, or a II-VI semiconductor material is disclosed. The method comprises placing a substrate having the semiconductor structure thereon onto a support table in a plasma processing chamber, the semiconductor structure carrying a patterned mask on the surface of the semiconductor structure distal from the support table. The method also includes process steps of establishing a flow of an etch gas mixture through the plasma processing chamber and generating a plasma within the plasma processing chamber and simultaneously applying a radio frequency (RF) bias voltage to the support table; whereby the portion(s) of the semiconductor structure not covered by the patterned mask are exposed to the etch gas mixture plasma and are thereby etched t