Structural and electrical characteristics of atomic layer deposited high κ HfO₂ on GaN

High κ HfO₂ was deposited on n-type GaN (0001) using atomic layer deposition with Hf(NCH₃C₂H₅)₄ and H₂O as the precursors. Excellent electrical properties of TiN/HfO₂/GaN metal-oxide-semiconductor diode with the oxide thickness of 8.8 nm were obtained, in terms of low electrical leakage current density (∼10^-6A/cm² at V_FB+1 V), well behaved capacitance-voltage (C-V) curves having a low interfacial density of states of 2×10¹¹ cm^-2 eV^-1 at the midgap, and a high dielectric constant of 16.5. C-V curves with clear accumulation and depletion behaviors were shown, along with negligible frequency dispersion and hysteresis with sweeping biasing voltages. The structural properties studied by high-resolution transmission electron microscopy and x-ray reflectivity show an atomically smooth oxide/GaN interface, with an interfacial layer of GaON ∼1.8 nm thick, as probed using x-ray photoelectron spectroscopy.