Leakage current conduction mechanisms and electrical properties of atomic-layer-deposited HfO2/Ga2O3 MOS capacitors

Abstract

In this paper, current conduction mechanisms in HfO2/β-Ga2O3 metal–oxide–semiconductor (MOS) capacitors under positive and negative biases are investigated using the current–voltage (I–V) measurements conducted at temperatures from 298 K to 378 K. The Schottky emission is dominant under positively biased electric fields of 0.37–2.19 MV cm−1, and the extracted Schottky barrier height ranged from 0.88 eV to 0.91 eV at various temperatures. The Poole–Frenkel emission dominates under negatively biased fields of 1.92–4.83 MV cm−1, and the trap energy levels are from 0.71 eV to 0.77 eV at various temperatures. The conduction band offset (ΔEc) of HfO2/β-Ga2O3 is extracted to be 1.31 ± 0.05 eV via x-ray photoelectron spectroscopy, while a large negative sheet charge density of 1.04 × 1013 cm−2 is induced at the oxide layer and/or HfO2/β-Ga2O3 interface. A low C–V hysteresis of 0.76 V, low interface state density (Dit) close to 1 × 1012 eV−1 cm−2, and low leakage current density of 2.38 × 10−5 A cm−2 at a gate voltage of 7 V has been obtained, suggesting the great electrical properties of HfO2/β-Ga2O3 MOSCAP. According to the above analysis, ALD-HfO2 is an attractive candidate for high voltage β-Ga2O3 power devices.