Au‐Free ohmic contacts and their impact on sub contact charge carrier concentration in AlGaN/GaN heterostructures

The impact of an Au-free Ti/Al/Ti/TiN (20/100/20/80 nm) ohmic contact metallization on Al0.21Ga0.79N/GaN heterostructure is investigated. Using the transfer length method and Hall measurements, sheet resistance carrier concentration below are analyzed, depending post-deposition annealing temperature. It shown that with increasing temperature, density enhanced. This caused by formation mechanism, leading to extremely low end sub-contact region 0.04 Ω mm. However, while semiconductor low, (front) device channel 0.74 mm after at 900 °C, indicating a depletion 2D electron gas because alloy formation.