The ferroelectric orthorhombic phase formation of Hf0.5Zr0.5O2 thin films on (−201) β-Ga2O3 substrate by atomic layer deposition

Abstract The orthorhombic (O) phase formation process of Hf 0.5 Zr 0.5 O 2 (HZO) thin films on Ga 2 O 3 substrate is demonstrated. As deposited HZO thin film has the O and tetragonal (T) phases together with an amorphous phase and post-metallization annealing suppresses the crystallization into the T phase and promotes the O phase compared to annealing without a top electrode. Positive-up-negative-down measurement reveals that remanent polarization for the downwards (accumulation side) only originates from the ferroelectricity in HZO films on Ga 2 O 3 substrate. Using normal capacitance–voltage ( C–V ) measurements, a clear capacitance change from accumulation to depletion was observed. However, the C–V results also show clockwise hysteresis by charge injection from the semiconductor. High-speed C–V measurements at a voltage sweep frequency above 3 Hz show counterclockwise hysteresis, and hysteresis width saturates as the applied voltage increases. Based on these results, HZO thin films with O phase on Ga 2 O 3 substrates have ferroelectricity.