Low-resistance Ohmic contact on undoped AlGaN∕GaN heterostructure with surface treatment using CCl2F2 reactive ion etching

Abstract

The effects of the surface treatments on the performance of Ti∕Al∕Ti∕Au Ohmic contacts to undoped AlGaN∕GaN heterostructure are investigated. Contact resistance and specific contact resistivity as low as 0.25Ωmm and 5.85×10−7Ωcm2, respectively, have been achieved through pretreatment in CCl2F2 plasma followed by buffered oxide etch solution, with rapid thermal annealing at 900°C for 30s in a N2 ambient. The electrical quality and annealing temperature dependence of the metallization scheme are illustrated. Furthermore, excellent edge acuity is also demonstrated for this annealed Ti∕Al∕Ti∕Au Ohmic contact.