  We report on the low-frequency electronic noise in
(Al$_x$Ga$_{1-x}$)$_2$O$_3$ Schottky barrier diodes. The noise spectral density
reveals 1/f dependence, characteristic of the flicker noise, with superimposed
Lorentzian bulges at the intermediate current levels (f is the frequency). The
normalized noise spectral density in such diodes was determined to be on the
order of 10$^{-12}$ cm$^2$/Hz (f=10 Hz) at 1 A/cm$^2$ current density. At the
intermediate current regime, we observed the random telegraph signal noise,
correlated with the appearance of Lorentzian bulges in the noise spectrum. The
random telegraph signal noise was attributed to the defects near the Schottky
barrier. The defects can affect the local electric field and the potential
barrier, and correspondingly, impact the electric current. The obtained results
help to understand noise in Schottky barrier diodes made of ultra-wide-band-gap
semiconductors and can be used for the material and device quality assessment.

Materials Science;Other Condensed Matter