Plasma etch-induced conduction changes in gallium nitride

The effect-of plasma-etching damage on carrier transport; properties in GaN has been studied under various plasma conditions by monitoring the changes in sheet resistivity (rho(s)) and mobility (mu(s)) or the resistivity (R). All the etching experiments were performed in an electron cyclotron resona nce microwave plasma reactive ion etching (ECR-RIE) system. Consistent chan ges in the transport properties have been observed with increasing de bias (ion energy) in all plasmas except in those containing chlorine. With noble gas plasmas, the largest change in conductance was created when Ar, the he aviest ion, was accelerated to its highest voltage. In these Ar sputtering cases, substantial surface micro-roughening has been observed. These surfac es also display considerable nitrogen deficiency as measured by Auger elect ron spectroscopy. These observations suggest that preferential sputtering o f nitrogen from the surface of GaN is one form of ion damage. The other is displacement damage. Both of these forms of ion damage are considered to be the direct-cause of the observed changes in the electrical properties.