Temperature dependent characteristics of Ni/Au vertical Schottky diode based on mechanically exfoliated beta-Ga2O3 single crystal

Abstract

In this paper, a Ni/Au vertical structure Schottky diode based on mechanically exfoliated β-Ga₂O₃ is fabricated. The temperature dependent characteristics of <i>I</i>-<i>V</i> curves are measured. The device shows a good rectifying behavior. As the temperature increases from 300 K to 473 K, the barrier height increases from 1.08 eV to 1.35 eV, and the ideal factor decreases from 1.32 to 1.19. Both of them show strong temperature dependence, which indicates that the Schottky barrier of the device is inhomogeneous. The device has a double exponential forward I-V characteristic curve, which may be related to crystal defects, surface states, surface energy band bending and the effect of mechanical exfoliation from the crystal surface. Through Cheung's method and Norde's method, the series resistances and barrier heights of the device at different temperatures are extracted. It is found that the parameters extracted by the Norde's method are in good agreement with the values obtained from the forward <i>I</i>-<i>V</i> curve. The series resistance decreases with temperature increasing, which is mainly caused by the increase of the concentration of thermally excited carriers. In this paper, the temperature characteristics of the device are modified by the Gauss distribution of the barrier height. The corrected barrier height is 1.54 eV and Richardson's constant is 26.35 A·cm^–2·K^–2, which is closer to the theoretical value. It shows that the <i>I</i>-<i>V</i> temperature characteristics of Au/Ni/β-Ga₂O₃ Schottky diodes can be described by the thermionic emission model of the Gauss distribution barrier height accurately. There are a lot of surface states on the surface of Ga₂O₃ single crystal obtained by Mechanical exfoliation, which has a great influence on the Schottky contact of the device and may lead to the inhomogeneity of Schottky barriers. At the same time, due to mechanical exploiation, the surface of gallium oxide single crystal material is not completely continuous, and the single crystal surface has layered or island structure. This will also cause the inhomogeneous Schottky barrier height. Considering the influence of inhomogeneous barrier on Schottky diode, the method of measuring the temperature characteristics is more suitable to extracting the electrical parameters of β-Ga₂O₃ Schottky diodes than the method of fitting <i>I</i>-<i>V</i> forward curve by TE model.