Demonstration of Annealing-free Metal-Insulator-Semiconductor (MIS) Ohmic Contacts on a GaN Substrate using Low Work-function Metal Ytterbium (Yb) and Al2O3 Interfacial Layer

Abstract

In this letter, the Metal-Insulator-Semiconductor (MIS) contacts are fabricated on the GaN substrates and compared to the Metal-Semiconductor (MS) contacts. To alleviate the Fermi level pinning effect at the Metal-Semiconductor interface, an Al 2 O 3 interfacial layer (IL) (1 ~ 3 nm) is used to form the MIS contacts. By comparing the electrical characteristics, the contact with 0nm Al 2 O 3 layer, i.e., MS contact, shows a lowest current compared to the contacts with an Al 2 O 3 IL, i.e., MIS contact. Furthermore, the current at 0.5V in the fabricated Transmission Line Measurement (TLM) device with 1nm Al 2 O 3 IL is 103 times higher the one without an Al 2 O 3 IL. This proves that inserting an Al 2 O 3 IL could mitigate the Fermi level pinning, resulting in a low Schottky barrier height. Finally, based on the TLM analysis, the resistivity of 5.1×10−4 Ω.cm2 is demonstrated in the MIS contact with 1nm Al 2 O 3 IL.