Temperature dependence of Al/Ti-based Ohmic contact to GaN devices: HEMT and MOSFET

In this paper two types of Al/Ti-based Ohmic contacts to Gallium Nitride (GaN) based devices are presented; Implanted N+ GaN (like the ones found in the Source/Drain of GaN Metal Oxide Semiconductor Field Effect Transistors–MOSFET) and heterojunction (HJ) AlGaN/GaN contacts (Source/Drain of High Electron Mobility Transistors–HEMT). Sheet resistance (Rsh) and contact resistance (Rc) have been investigated in the temperature (T) range of 25–250 °C. It was found that the Rsh (850/700 Ω□) (25/250 °C) and Rc (2.2/0.7 Ωmm) decrease with T for Implanted N+ GaN contact and Rsh (400/850 Ω□) and Rc (0.2/0.4 Ωmm) (weakly for Rc) increase with T for HJ AlGaN/GaN contact. Numerical computation based models are used to determine the theoretical Rsh and Rc behavior with T and to fit the experimental values.