Surface morphology and electrical properties of Au/Ni/$\langle$C$\rangle$/$n$-Ga$_2$O$_3$/$p$-GaSe$\langle$KNO$_3\rangle$ hybrid structures fabricated on the basis of a layered semiconductor with nanoscale ferroelectric inclusions

Features of the formation of Au/Ni/$\langle$C$\rangle$/$n$-Ga$_2$O$_3$ hybrid nanostructures on a Van der Waals surface (0001) of “layered semiconductor–ferroelectric” composite nanostructures ($p$-GaSe$\langle$KNO$_3\rangle$) are studied using atomic-force microscopy. The room-temperature current-voltage characteristics and the dependence of the impedance spectrum of hybrid structures on a bias voltage are studied. The current-voltage characteristic includes a resonance peak and a portion with negative differential resistance. The current attains a maximum at a certain bias voltage, when electric polarization switching in nanoscale three-dimensional inclusions in the layered GaSe matrix occurs. In the high-frequency region ($f >$ 10$^6$ Hz), inductive-type impedance (a large negative capacitance of structures, $\sim$10$^{-6}$ F/mm$^2$) is detected. This effect is due to spinpolarized electron transport in a series of interconnected semiconductor composite nanostructures with multiple $p$-GaSe$\langle$KNO$_3\rangle$ quantum wells and a forward-biased “ferromagnetic metal–semiconductor” polarizer (Au/Ni/$\langle$C$\rangle$/$n^+$-Ga$_2$O$_3$/$n$-Ga$_2$O$_3$). A shift of the maximum (current hysteresis) is detected in the current-voltage characteristics for various directions of the variations in bias voltage.