Micron thick Gd₂O₃ films for GaN/AlGaN metal-oxide-semiconductor heterostructures

One micron thick Gd₂O₃ films were grown on GaN/AlGaN heterostructures by reactive electron beam physical vapor deposition. The films were of cubic bixbyite phase with strong (222) out-of-plane and in-plane textures. The films showed a columnar microstructure with feather-like growth. Transmission electron microscopy analysis and selected area diffraction showed highly oriented single crystal like growth near the film interface which degraded as the film thickness increased. Capacitance-voltage (C-V) characteristics show that the Gd₂O₃ device results in a negative threshold shift of approximately 1.9 V. Hysteresis of 0.9 V was extracted from the C-V curve corresponding to a trapped charge density of 6.9 × 10¹⁰ cm^{- 2}. The conduction mechanisms were found to be dominated by Poole-Frenkel conduction between 50 and 100 °C and Schottky emission between 125 and 200 °C. The trap height for Poole-Frenkel conduction was 0.46 eV and the Schottky barrier height was 0.79 eV.