Electrical properties of SiN/GaN MIS diodes formed by ECR-CVD

Abstract

Silicon nitride (SiN) film was deposited at 300 °C as the insulating layer of a GaN-based metal–insulator–semiconductor (MIS) diode by using electron cyclotron resonance chemical vapor deposition (ECR-CVD) with silane-to-nitrogen (SiH 4/N 2) flow ratio of 5/45. The deposited film had the refractive index of 1.9–2.0 and the relative dielectric constant of 6. Capacitance–voltage ( C– V) characteristics were measured at 1 MHz and interface state densities were obtained by Terman's method. The negative fixed charge density of the SiN film was 1.1×10 11 cm −2 and its breakdown field was greater than 5.7 MV/cm even at 350 °C. The value of the interface state density was less than 4×10 11 cm −2 around the mid-gap and its minimum was 5×10 10 cm −2 eV −1 at 0.6 eV below the conduction band edge. From these results, the SiN film deposited by ECR-CVD is a promising gate dielectric for high temperature GaN-MISFET application.