Dry etching and metallization schemes in a GaN/SiC heterojunction device process

Dry etching and metallization schemes are described for a GaN/SiC heterojunction. GaN was reactive ion etched in a chlorine based chemistry (Cl-2/Ar), and an ICP etch was used on 4H-SiC using a fluorine based chemistry (SF6/Ar/O-2). The etch rates obtained on GaN was above 400 nm/min. High sample temperature from self heating and large de-bias was the probable cause for the high etch rate. The ICP etch rate on SiC approached 320 nm/min, and the etch selectivity to GaN was >100. The metallization was based on Ti for both n-GaN and p-SiC. TLM and Kelvin structures were used to extract the specific contact resistivity, rho (C). After a 950 degreesC anneal in N-2 rho (C) On the GaN samples were below 1.10(-6) Omega .cm(2) for sputtered contacts in room temperature, and an order of magnitude higher with evaporation. On p-SiC no ohmic behavior was found with a doping of 4.10(18) cm(-3), but the same contact metallization on highly doped areas (>10(20) cm(-3)) showed ohmic behavior with rho (c) below 10(-4) Omega cm(2).