Schottky-to-ohmic behavior in annealed Ti/Si/Ti/Al/Ni/Au on AlGaN/GaN

Abstract

Annealing of contact system Ti/Al/Ni/Au for the Ohmic contact formation to the AlGaN/GaN was performed. Method for determining the height of potential barrier in nonrectifying contact using voltage-capacitance characteristic was proposed. Temperature dependencies of the contact resistance for annealed Ti/Al/Ni/Au in temperature range 25÷175°C were obtained. Thermal field emission prevails in rectifying contact, whereas for nonrectifying contact field emission is typical. It is shown that the charge carriers' concentration increase in four times influences on the transition from thermal field emission to field emission. The change of resistance under field emission agrees with the barrier height change. The resulting contact resistance for Ti/Si(6 nm)/Ti/Al/Ni/Au is equal to 0.2 Ω·mm.