Effect of ambient humidity on the electrical conductive properties of polymorphic Ga$_{2}$O$_{3}$ structures

The effect of ambient humidity on the electrical conductive properties of $\alpha$-Ga$_{2}$O$_{3}$ and $\alpha$-Ga$_{2}$O$_{3}$/$\varepsilon$-Ga$_{2}$O$_{3}$ structures has been studied. Polymorphic Ga$_{2}$O$_{3}$ epitaxial layers were deposited by chloride vapor phase epitaxy on sapphire substrates. Pt and Pt/Ti were used as contacts. It was found that the Pt/$\alpha$-Ga$_{2}$O$_{3}$/Pt and Pt/Ti/$\alpha$-Ga$_{2}$O$_{3}$/$\varepsilon$-Ga$_{2}$O$_{3}$/Ti/Pt structures exhibit a high sensitivity of the current – voltage characteristics (I–V characteristics) to atmospheric humidity in the temperature range 25–100$^{\circ}$C. It was found that the effect of water vapor on the I–V characteristics of the structures is reversible and the most significant changes in the current in the samples are observed at a relative humidity RH $\ge$ 60%. With increasing temperature the effect of atmospheric humidity on the I–V characteristics decreases and disappears at $T>$ 100$^{\circ}$C. The experimental results obtained are explained in terms of the Grottguss mechanism.