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.For example, Harada et al. published their work on Schottky diodes fabricated on n-type Ga2O3 with PdCoO2 as the metal [2]. They claimed that their Schottky diodes have a very large Schottky barrier height of 1.8 eV. Other scientists using metals like W, Au, Ir, Pd or Pt cannot achieve such a large value of the Schottky barrier height. However, they did not propose any physical mechanism regarding the reverse leakage current in their Schottky diodes. One possible mechanism of reverse leakage current in Schottky diodes fabricated on n-type Ga2O3 is image force barrier lowering at the metal-Ga2O3 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 [3]. 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 [4], where n is the refractive index of the semiconductor in the infrared or visible light range. The theory of Sze et al. quickly became the dominating theory whereas Krömer’s theory essentially became a forgotten theory. For Ga2O3, n is approximately equal to 2 [5] and so n2 is about 4. The author performed an analysis on the experimental data published by Harada et al. [2] and found that Krömer’s theory fit the experimental data from Harada et al. much better than the theory of Sze et al. Similarly, the author noticed that Krömer’s theory is better than the theory of Sze et al. for diamond Schottky diodes.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.