Combination of Reactive-Ion Etching and Chemical Etching as a Method for Optimizing the Surface Relief on AlGaInN Heterostructures

A relief on the surface of GaN previously released from the growth substrate is formed by a combined method in which reactive ion etching is used in combination with liquid etching (in KOH or hydrochloric-acid solutions). The dependence of obtained relief on the sequence of operations used is studied. It is shown that etching in a KOH solution followed by reactive ion etching provides the appearance of truncated hollow cones on the surface. In experiments, the ability of a hydrochloric-acid solution for etching exclusively GaN relief elements formed by reactive ion etching of the surface is also found. As a result, reactive ion etching of the sample followed by immersion into hydrochloric acid forms objects of cylindrical shape on its surface transforming at the base into conical or strongly distorted pyramidal structures. The appearance of this relief can be explained by the predominance of the chemical component in reactive ion etching with increasing distance from the sample surface. Further optimization of the relief parameters obtained as a result of combined etching is possible by varying the modes of operation under use.