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 to form at least one feature in the semiconductor structure; wherein more than 90% of the etch gas mixture consists of a mixture of silicon tetrachloride (SiCl4) and nitrogen (N2).