Electrical Properties of Vertical p‐NiO/n‐Ga₂O₃ and p‐ZnCo₂O₄/n‐Ga₂O₃ pn‐Heterodiodes

Abstract

Vertical β-Ga 2 O 3 -based pn-heterostructures are investigated by currentvoltage measurements and thermal admittance spectroscopy. The β-Ga 2 O 3 thin films are grown by pulsed laser deposition (PLD) on (00.1)ZnO:Ga/(11.0) Al 2 O 3 substrates at 670 C. Two different p-type oxides are used to fabricate pn-heterodiodes which are investigated with respect to rectification, temperature stability, and breakdown behavior. For that, p-NiO and p-ZnCo 2 O 4 are grown by PLD at room temperature on top of a β-Ga 2 O 3 thin film, respectively. The rectification ratio at room temperature is about nine orders of magnitude, the ideality factor is about 2 and the on-resistance is below 1 Ω cm 2 . Both diode types did not show degradation for temperatures up to 100 C. Thermal admittance spectroscopy revealed defects in β-Ga 2 O 3 with thermal activation energy E a of about 200 meV for both diode types. Additionally, a level with E a % 240 meV is detected for the NiO/Ga 2 O 3 diodes only. In general, both diode types are suited to realize pn-heterodiodes with high rectification, but NiO is especially interesting for defect characterization by deep-level optical spectroscopy due to its transparency up to about 3.7 eV.

Electrical Conductivity Studies in Sol–Gel‐Derived Li‐Doped NiO Epitaxial Thin Films

“…[ 13 ] In addition, we reported the epitaxial growth of NiO thin films on β‐Ga 2 O 3 substrates including the crystal orientation relationship between them. [ 15,16 ] Similar rectification characteristics of NiO/β‐Ga 2 O 3 pn heterojunction diodes were also reported by Schlupp et al [ 17 ]…”

“…[13] In addition, we reported the epitaxial growth of NiO thin films on β-Ga 2 O 3 substrates including the crystal orientation relationship between them. [15,16] Similar rectification characteristics of NiO/β-Ga 2 O 3 pn heterojunction diodes were also reported by Schlupp et al [17] Since the electrical properties of the NiO films play an important role in determining device performance, an understanding of the nature of carrier transport in NiO is needed. Highly stoichiometric NiO is a Mott insulator, but excess oxygen atoms in NiO result in the formation of nickel vacancies accompanied by the oxidation of Ni 2þ to Ni 3þ to preserve electrical neutrality.…”

All‐Oxide Transparent Thin‐Film Transistors Based on Amorphous Zinc Tin Oxide Fabricated at Room Temperature: Approaching the Thermodynamic Limit of the Subthreshold Swing

“…Thus, the p ‐type character of NiO has qualitatively been confirmed by performing Seebeck measurements. [ 33 ] Eventually, all gate contacts were capped with a 20 nm thin GZO layer to ensure a homogeneous electric potential distribution.…”

Rectifying Effect of the Sr3Al2O6/Ga2O3 Heterojunction

“…In oxides system, oxides interfaces offer numerous opportunities for researchers to investigate and analyze some exciting and intriguing phenomena due to their discontinuous energy bands . Many significant progresses had been realized by developing oxide heterojunctions . Wu et al developed a deep UV PD based on the Ga 2 O 3 /Ga:ZnO heterojunction grown by laser molecular beam epitaxy (laser‐MBE) technique, and it is a self‐powered mode.…”