Mechanism of Reverse Leakage Current in Schottky Diode Fabricated on Large Bandgap Semiconductors like Ga2O3 or Diamond Part II

Abstract

The bandgap of Ga2O3 (4.5-4.9 eV) is larger than the bandgap of GaN (3.4 eV). In addition, single crystal bulk Ga2O3 wafers can be more easily manufactured than GaN wafers. Therefore, Ga2O3 has strong potential for applications in high power semiconductor devices [1]. Schottky diodes fabricated on n-type Ga2O3 have strong potential as fast high-power switching devices. Similarly, the bandgap of diamond (5.5 eV) is very large and diamond Schottky diodes have good potential.One possible mechanism of reverse leakage current in Schottky diodes is image force barrier lowering at the metal-semiconductor interface. Historically, there were 2 theories regarding the image force barrier lowering effect. In 1953, Krömer published his theory that the image force dielectric constant in the equation for Schottky emission should be equal to 1 [2]. Subsequently in 1964, Sze et al. published their theory that the image force dielectric constant in the equation for Schottky emission should be equal to n2 [3], where n is the refractive index of the semiconductor in the infrared or visible light range. In 1969, Sze published a book which has influenced many scientists [4]. Sze’s theory [3]-[4] quickly became the dominating theory whereas Krömer’s theory essentially became a forgotten theory. In 2020, the author pointed out that Krömer’s theory is quite frequently more compatible with experimental results for Ga2O3 or diamond Schottky diodes [5]. In 2021, the author attempted to propose a new theory involving the concept of electron velocity overshoot to unify Krömer’s theory and Sze’s theory, as shown in Fig. 1 [6]; Krömer’s theory is better than Sze’s theory for high reverse bias voltage.In conclusion, the author pointed out that it is necessary to resurrect an old and forgotten theory from Krömer in order to explain the experimental data on the reverse leakage current of Schottky diodes fabricated on large bandgap semiconductors like Ga2O3 and diamond, etc. A theoretical basis based on quasi-ballistic transport will be provided.