ZrO2/(Al)GaN metal–oxide–semiconductor structures: characterization and application

Abstract

We investigate the properties of high-k dielectric insulators on GaN. 22 nm thick ZrO2 is deposited on N- or Ga-polarity GaN. Al/ZrO2/GaN metal–oxide–semiconductor and reference Au/Ni/GaN Schottky contact structures are characterized using current–voltage and capacitance–voltage methods. If compared with Schottky contacts, metal–oxide–semiconductor structures show leakage current substantially reduced for the N-polarity GaN while comparable values were obtained for the Ga-polarity GaN. The oxide relative permittivity is found to be in the range of 20–30. Light-assisted capacitance–voltage method shows density of interface states Dit ∼ 1 × 1012 cm−2 eV−1 for Ga-polarity and ∼2 × 1012 cm−2 eV−1 for N-polarity GaN/ZrO2. Finally, we prepared AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistor proving minimal transconductance deterioration and small threshold voltage shift. It is suggested that ZrO2 deposition optimization may further reduce the leakage current.