Utilizing Ge interlayer and patterned substrate to improve the contact resistance of n-GaN

This paper is demonstrated the effect of Ge interlayer and patterned substrate to form low resistance Ohmic contact of n-GaN. The Ge interlayer is acted as heavily n-type dopant atoms at the interface of metal and n-GaN to enhance carrier tunneling. The patterned substrate is designed to increase the annealing temperature at the interface of the metal and n-GaN. Contact resistances were derived from the plot of the measured resistance versus gap spacing by TLM (Transmission Line Model). After annealing at 400 °C for 5mins, It is shown that, Al (300nm)/Ti (30nm)/Ge (10nm)/ pit-patterned n-GaN substrate scheme exhibit ohmic contact behavior with a resistivity of 3.49×10-5 Ω-cm2. The low contact resistance is formed by Al (300nm)/Ti (30nm)/Ge (10nm)/pit-patterned n-GaN substrate scheme, and it is compare with Al (300nm)/Ti (30nm)/n-GaN substrate. Therefore, this results show that utilizing Ge interlayer and patterned substrate could serve as an important processing tool for forming low-resistance Ohmic contacts of n-GaN.