Comparative Analysis of Ni/Ag and Ni/Au Contacts on GaN/AlGaN/GaN Platform

Herein, the electrical characteristics and Schottky barrier of Ni/Au and Ni/Ag contacts on the GaN/AlGaN/GaN heterojunction are investigated. Both contacts on the p-GaN contact layer (Mg: ≈3 × 10¹⁹cm⁻³) exhibit weak Schottky characteristics. The nonlinear current–voltage (I–V) characteristics are observed, leading to variations in contact resistance (R_C) and sheet resistance (R_sh) with changing bias voltage. The Ni/Ag contact achieves a lower Schottky barrier height calculated by using the I–V method. Furthermore, when employing a p⁺⁺-GaN layer (Mg: ≈1 × 10²⁰cm⁻³) as the contact layer, the Ni/Ag contact forms an Ohmic contact without Schottky characteristics, achieving a satisfactory R_C of 30.31 Ω mm. This result demonstrates its viability as a competitive candidate for p-channel field-effect transistors’ fabrication.