Resistive Switching in Epitaxial AlN and AlScN Thin Films on Si(111)

We report the growth of smooth AlN and AlScN thin films on Si(111) using reactive sputtering. X-ray diffraction shows that both AlN and AlScN films are epitaxial single crystals with a [0001] out-of-plane orientation. We report a suite of characterization results, including X-ray reflectivity, atomic force microscopy, Raman spectroscopy, and instrumented nanoindentation. Our study of conductivity switching in these materials is motivated by recent interests in AlScN for ferroelectric random access memory applications. We found that applying electric fields in excess of 2×10⁶ V/cm resulted in more than one thousand-fold increase in conductivity. However, applying an electric field with a similar magnitude but the reverse polarity caused the conductivity to revert to the initial state. In AlN, this effect was observed stably in excess of 100 cycles, and in AlScN, we report up to 10 manual switching cycles. Epitaxial AlScN/Si offers the opportunity for epitaxial integration of resistive and ferroelectric random access memory on Si(111) with the possibility of additional epitaxial layers.