NiZnAl-based p-type ohmic contacts on AlGaAs/InGaAs heterostructures

p-type ohmic contacts based on Ni/Zn/Al/TiWN metallization were evaluated for application to self-aligned p-channel heterostructure FETs. Low-resistance, stable ohmic contacts were achieved on Al/sub x/Ga/sub 1-x/As/InGaAs heterostructures with aluminum composition (x) as high as 0.75. Following short-term annealing of 30 s in the temperature range of 500 degrees C to 600 degrees C, contact resistances less than 0.6 Omega -mm and specific resistivities under 5*10/sup -6/ Omega -cm/sup 2/ were achieved. Further anneal at 500 degrees C for 10 min resulted in a minimum contact resistance of 0.06 Omega -mm and a specific resistivity of 3.2*10/sup -8/ Omega -cm/sup 2/. Contact morphology was mirror-smooth and specular and the contacts were found to be stable at 500 degrees C for anneal times as long as 40 min, with contact resistance remaining below 1 Omega -mm.<
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