Reactive Ion Beam Etching of GaN and AlGaN/GaN for Nanostructure Fabrication Using Methane-Based Gas Mixtures

The basic characteristics of ECR-reactive ion beam etching (RIBE) of GaN and AlGaN using methane-based mixtures was studied for nanowire fabrication is studied. Both of GaN and AlGaN/GaN heterostructure can be etched by using a gas mixture of CH4/H2/Ar at a low etching rate of about 10nm/min giving nm accuracy. and line pattern etching showed 0-110 and 11-21 sidewall facets, respectively, indicating its chemical reaction dominant low-damage nature. By conventional CH4-based gas mixture, the etching saturates at a depth of a few 100 nm and roughness of surface increases with time, since the surface reaction produced Ga rich surface and this disturbs the etching process. By adding nitrogen into the gas mixture (CH4/H2/Ar/N2 = 5/15/1. 5/4. 5 sccm), surface stoichiometry is dramatically improved. This also gives smooth etched surface with roughness of 2 nm enough for nanostructure fabrication. By using the optimized etching condition with nitrogen addition to the gas mixture, an AlGaN/GaN nanowire structure with a wire width of 110 nm has been successfully fabricated.