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

In this paper, current conduction mechanisms in HfO2/beta-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 (Delta Ec) of HfO2/beta-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 x 10(13) cm(-2) is induced at the oxide layer and/or HfO2/beta-Ga2O3 interface. A low C-V hysteresis of 0.76 V, low interface state density (D-it) close to 1 x 10(12) eV(-1) cm(-2), and low leakage current density of 2.38 x 10(-5) A cm(-2) at a gate voltage of 7 V has been obtained, suggesting the great electrical properties of HfO2/beta-Ga2O3 MOSCAP. According to the above analysis, ALD-HfO2 is an attractive candidate for high voltage beta-Ga2O3 power devices.