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

Vertical β‐Ga2O3‐based pn‐heterostructures are investigated by current–voltage measurements and thermal admittance spectroscopy. The β‐Ga2O3 thin films are grown by pulsed laser deposition (PLD) on (00.1)ZnO:Ga/(11.0)Al2O3 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‐ZnCo2O4 are grown by PLD at room temperature on top of a β‐Ga2O3 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 cm2. Both diode types did not show degradation for temperatures up to 100 °C. Thermal admittance spectroscopy revealed defects in β‐Ga2O3 with thermal activation energy Ea of about 200 meV for both diode types. Additionally, a level with Ea ≈ 240 meV is detected for the NiO/Ga2O3 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. Vertical β‐Ga2O3‐based pn‐heterostructures are investigated by current–voltage measurements and thermal admittance spectroscopy. As p‐type materials room temperature fabricated NiO or ZnCo2O4 is used. The vertical device layout is realized using a highly conducting ZnO:Ga back contact layer. High current rectification of nine orders of magnitude is observed. A defect level with an activation energy of about 200 meV is found in the β‐Ga2O3.