Highly chemical reactive ion etching of gallium nitride

A highly chemical reactive ion etching process has been developed for MOVPE -grown GaN on sapphire. The key element for the enhancement of the chemical property during etching is the use of a fluorine containing gas in a chlor ine based chemistry. In the perspective of using GaN substrates for homo-ep itaxy of high quality GaN/AlGaN structures we have used the above described RIE process to smoothen Ga-polar GaN substrates. The RMS value, measured b y AFM, went from 20 Angstrom (after mechanical polishing) down to 4 Angstro m after 6 minutes of RIE. Etching N-polar GaN resulted in a higher etch rat e than Ga-polar materials (165 vs. 110 nm/min) but the resulting surface wa s quite rough and suffers from instability problems. Heat treatment and HCl dip showed a partial recovery of Schottky characteristics after RIE.