Microanalysis of the Ti/Al and Ti/Al/Mo/Au ohmic contacts metallization to AlGaN/GaN heterostructures

摘要

The article presents the comparative study of two metallization schemes, Ti/Al bilayer and Ti/Al/Mo/Au multilayer to AlGaN/ GaN heterostructures. The influence of thermal annealing on the topography and sheet resistance R_(sh) of the metallization was investigated. At the temperature of annealing up to 805 ℃ Ti/Al metallization morphology changed but the metallization continuity was sufficient to obtain the sheet resistance below 2Ω/□. Annealing at 820 ℃ caused the strong increase of sheet resistance up to 254Ω/□. These results clearly indicated on very large heterogeneity of Ti/Al layers, material phase segregation, and the separation into individual islands. The annealing of Ti/Al/Mo/Au metallization also resulted in rise of sheet resistance. But the continuity of Ti/Al/Mo/Au layers did not deteriorate the sheet resistance value and homogeneity so significantly as for Ti/Al layers. In this case the changes were much lower, R_(sh) increased only to 1.15Ω/□.