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

Abstract

Abstract The orthorhombic (O) phase formation process of Hf0.5Zr0.5O2 (HZO) thin films on Ga2O3 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 Ga2O3 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 Ga2O3 substrates have ferroelectricity.