High Quality Epitaxial Piezoelectric and Ferroelectric Wurtzite Al_1‐xSc_xN Thin Films

Abstract

Piezoelectric and ferroelectric wurtzite are promising to reshape modern microelectronics because they can be easily integrated with mainstream semiconductor technology. Sc doped AlN (Al1‐xScxN) has attracted much attention for its enhanced piezoelectric and emerging ferroelectric properties, yet the commonly used sputtering results in polycrystalline Al1‐xScxN films with high leakage current. Here, the pulsed laser deposition of single crystalline epitaxial Al1‐xScxN thin films on sapphire and 4H‐SiC substrates is reported. Pure wurtzite phase is maintained up to x = 0.3 with ≤0.1 at% oxygen contamination. Polarization is estimated to be 140 µC cm−2 via atomic scale microscopy imaging and found to be switchable via a scanning probe. The piezoelectric coefficient is found to be five times of the undoped one when x = 0.3, making it desirable for high‐frequency radiofrequency (RF) filters and 3D nonvolatile memories.