Device fabrication and DC characteristics of AlGaAs/GaAs high electron mobility transistors

Abstract

We report the successful fabrication of functional AlGaAs/GaAs high electron mobility transistors using standard photolithography techniques. The fabrication process involved three lithography steps: (a) ohmic contact formation, (b) etch trench and (c) gate formation. AuGe/Ni/Au was utilized for the source and drain ohmic contacts and Al for the Schottky gate contact. Thermal annealing of AuGe/Ni/Au to form ohmic contacts was first optimized to obtain the lowest contact resistance prior to actual HEMT fabrication. Transmission line measurement was used to determine contact resistance. The lowest ρ_c value of 8.06 x 10⁻⁵ Ωcm² was obtained at an annealing temperature of 480°C. Finally, the DC characteristics of the device at room temperature were investigated. A transconductance of 300 μS and I_DSS of 554 μA were measured for the device.