Study of Pd/Au metallisation and surface characteristics on Mg-doped GaN induced by low power inductively coupled plasma etching

Abstract

We report on the surface morphology and electrical characterisation of p-GaN layers etched using inductively coupled plasma reactive ion etching (ICP-RIE). The use of ICP-RIE etching at low ICP and RF powers of 150 and 75 W, respectively has produced a smooth surface, with a root-mean-square (RMS) amplitude of 1.80 nm. Etching was performed for 3 min with an etching rate of 175 nm/min. However, despite the low power and the resultant smooth surface with a good etch rate, current–voltage measurements indicated that the qualities of ohmic contacts were poor after the dry etching process. Thus, even the use of low power ICP-RIE has resulted in significant damage to the p-GaN surface, causing a poor of the quality of the contact near the surface layer region. Use of rapid thermal annealing and boiling NaOH as post-treatments on the etched p-GaN were not successful in restoring the pre-etched ohmic characteristics of the contacts compared to those on unetched materials.