COMPARISON OF OHMIC METALLIZATION SCHEMES FOR INGAALN

W, WSi0.44, and Ti/Al contacts were examined on n(+)In(0.65)Ga(0.35)N, InN, and In0.75Al0.25N. W Was found to produce low specific contact r esistance (Q(c) similar to 10(-7) Omega cm(2)) ohmic contacts to InGaN , while WSis showed an as-deposited Q(c) of 4 x 10(-7) Omega cm(2) but this degraded significantly with subsequent annealing, reaching 10(-5 ) Omega cm(2) at 700 degrees C. Ti/Al contacts on InGaN were stable to similar to 600 degrees C (Q(c) similar to 4 x 10(-7) Omega cm(2) at l ess than or equal to 600 degrees C). InN contacted with W and Ti/Al pr oduced ohmic contacts with Q(c) similar to 10(-7) Omega cm(2) and for WSix Q(c) similar to 10(-6) Omega cm(2) and all three metallization sc hemes retained values less than or equal to 10(-6) Omega cm(2) up to 6 00 degrees C. The contact resistances for all of the metals were great er than or equal to 10(-4) Omega cm(2) on InAlN, and degraded with sub sequent annealing. WSix contacts on InN grown graded from In0.6Al0.4N were also examined. The specific contact resistance was an order of ma gnitude lower (Q(c) similar to 10(-5) Omega cm(2)) after 500 degrees C anneal than that measured for WSix deposited directly on In0.6Al0.4N. Measurements of the temperature dependence of these contact structure s showed that field emission was generally the most important conducti on mechanism. (C) 1997 American Vacuum Society.