Electrical properties of RF-sputtered Zn-doped GaN films and p-Zn-GaN/n-Si hetero junction diode with low leakage current of 10−9 A and a high rectification ratio above 105

Abstract

Zn-doped GaN films have been deposited on Si (100), SiO2/Si (100), and glass substrates by RF reactive sputtering at 100–400°C with single cermet targets. The Zn-GaN films deposited with a 10% Zn cermet target showed the good electrical properties, wurtzite structure, and the p-type behavior without a thermal annealing process. At room temperature (RT), the 400°C-deposited film with mobility (μ) of 17.7cm2/V·s had the highest hole concentration (np) of 6.1×1017cm−3 and electrical conductivity of 1.72S·cm−1. The values of band gap (Eg) for Zn-GaN films were found in the range of 2.83–3.01eV. Furthermore, to prove the p-type behavior of Zn-doped GaN, the p-GaN/n-Si hetero junction diode was also made by RF reactive sputtering. At room temperature, the device showed the leakage current of 1.65×10−9A at −5V, the turn-on voltage of ∼2.3V, and the breakdown voltage above −20V. The high rectification (on/off) ratio of the diode was calculated to be ∼1.08×105 at bias of ±5V and ∼2.3×105 at the bias of ±20V. The electrical characteristics of the diode were also tested at the temperature range of 25–150°C. By using equations based on the standard thermionic-emission (TE) mode and the Cheungs’ method, the barrier height, ideality factor, and series resistance of the diode were also determined.