ABSTRACT
We report electrical measurements on four different metal contacts which formed Schottky barriers to lightly doped complementary n- and p-type Al0.48In0.52As epitaxial material grown by molecular beam epitaxy on semi-insulating InP substrates. The Schottky contact metals studied were Au, Al, Pt and the tri-layer Ti/Pt/Au. Schottky barrier heights were determined by current versus voltage and capacitance versus voltage measurements. The Schottky barrier heights obtained from current versus voltage measurements varied from 0.560 eV for Al on n-type Al0.48In0.52As to 0.905 eV for Al on p-type Al0.48In0.52As, with intermediate values for the other metals studied. The sum of the n- and p-type Schottky barrier heights for each metal contact ranged from 1.440 to 1.465 eV, in good agreement with the accepted Al0.48In0.52AS band-gap value of 1.45 eV. The agreement between the sum of the n- and p-type Schottky barrier heights obtained from capacitance versus voltage measurements and the accepted Al0.4In0.52As band-gap value were not as good as those obtained from current versus voltage measurements. An anomalously large enhanced Schottky barrier height was observed for the Al on p-type Al0.48In0.52AS system from capacitance versus voltage measurements.
