Search for a Suitable Ohmic Metallization Scheme to GaN/AIGaN Heterostructures for Sub-micron Devices

摘要

Ohmic properties, thermal stability and surface morphology of Al-based and non-aluminium metallizations are investigated in dependence on the annealing temperature and initial composition. Non-aluminium contacts show poor ohmic properties, while contact resistivity of 3.47×10~(-5)Ω.cm~2 is achieved for Ti/Al/Ti/Au metallization with a former-Ti/Al ratio of (30 wt.% /70 wt.%).Thermal properties of the Al-based metallization are improved by application of Mo layer as a barrier under the upper Au film of the contact structure. These contacts show excellent thermal stability at operating temperatures as high as 400℃. The less Al amount in the contact composition and Mo barrier layer contribute to the smoother surface and better edge acuity.