Sc-rich monocrystalline ScGaN grown by MBE exhibits attractive ferroelectric properties

Abstract

The rapid and continuous evolution of Sc-based ferroelectric nitrides in recent years has necessitated the exploration of monocrystalline thin films with ever-increasing Sc composition to yield greatly enhanced ferroelectric, piezoelectric, and optical properties. ScGaN presents as a natural choice due to the predicted solubility of ScN being greater in GaN than in AlN. Thus, we report the MBE growth of monocrystalline phase-pure ScGaN films on GaN, with Sc compositions of up to 48%. Detailed characterization reveals that, despite large lattice mismatch with GaN, high surface and crystal quality can be obtained. Coercive fields ranging from 3 to 1.2 MV cm−1, among the lowest reported for ferroelectric nitrides, are observed. Moreover, the fatiguing characteristics of Sc-rich ScGaN show non-zero polarization remaining after 109 bipolar cycles. These results highlight the potential of Sc-rich ferroelectric nitrides to harness outstanding ferroelectric, piezoelectric, and photonic properties all on a nitride platform.