  In this work we study the Schottky barrier height (SBH) at the junction
between $\beta$-Ga$_2$O$_3$ and platinum, a system of great importance for the
next generation of high-power and high-temperature electronic devices.
Specifically, we obtain interfacial atomic structures at different orientations
using our structure matching algorithm and compute their SBH using electronic
structure calculations based on hybrid density functional theory. The
orientation and strain of platinum are found to have little impact on the
barrier height. In contrast, we find that decomposed water (H.OH), which could
be present at the interface from Ga$_2$O$_3$ substrate preparation, has a
strong influence on the SBH, in particular in the ($\overline{2}$01)
orientation. The SBH can range from $\sim$2 eV for the pristine interface to
nearly zero for the full H.OH coverage. This result suggests that SBH of
$\sim$2~eV can be achieved for the Ga$_2$O$_3$($\overline{2}$01)/Pt junction
using the substrate preparation methods that can reduce the amount of adsorbed
water at the interface.

Materials Science