Search for a Suitable Ohmic Metallization Scheme to GaN/AlGaN Heterostructures for Sub-Micron Devices
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 3.47x10-5 Ω.cm2 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 400oC. The less Al amount in the contact composition and Mo barrier layer contribute to the smoother surface and better edge acuity.
Lilyana Kolakieva and Roumen Kakanakov
L. Kolaklieva et al., "Search for a Suitable Ohmic Metallization Scheme to GaN/AlGaN Heterostructures for Sub-Micron Devices", Solid State Phenomena, Vol. 159, pp. 81-86, 2010