Development of Contacts for Vertical GaSb Nanowires using Transmission Line Measurements

Abstract: A processing method is developed to characterize contacts for vertical nanowire structures. The process is based around optical lithography and an organic spacer material in order to facilitate an easily repeatable processing flow. Substrates with MOVPE grown GaSb nanowires are processed into sets of resistor devices. Variation in resistance of the devices is achieved by adding contacts at different heights to the otherwise similar nanowire devices. Contact resistance RC and specific contact resistivity ρc are extrapolated from a linear approximation of the measured resistance vs contact distance. The process is tested on samples with differently doped and dimensioned nanowires. Rapid thermal annealing is performed at temperatures 150 ◦C to 250 ◦C in order to study its effect on contact resistivity. The resulting ρc values are in the range of 30 Ω µm2 to 158 Ω µm2. Rapid thermal annealing at 150 ◦C to 200 ◦C shows improvement in contact resistivity, while RTA at 250 ◦C instead indicates a deterioration.