Chromium mask for plasma-chemical etching of [Al.sub.x][Ga.sub.1 - x]N layers

The influence of the mask material used for formation of GaN mesa-structures using plasmachemical etching in a B[Cl.sub.3] : Ar : [N.sub.2] atmosphere is studied. It is shown that a bilayer Si[O.sub.2]/Cr mask in which the thickness of the chromium layer is six to seven times smaller than a desired etch depth provides effective protection of the surface and allows the formation of structures with a flat surface for an etch depth of up to 2.5 µm. When the mask is produced by conventional lithography, the slope of the side walls is no more than 10° and decreases when liftoff lithography is applied. DOI: 10.1134/S1063784214090242