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Unintentionally doped (001)‐oriented orthorhombic κ‐Ga2O3 epitaxial films on c‐plane sapphire substrates are characterized by the presence of ≈ 10 nm wide columnar rotational domains that can severely inhibit in‐plane electronic conduction. Comparing the in‐ and out‐of‐plane resistance on well‐defined sample geometries, it is experimentally proved that the in‐plane resistivity is at least ten times higher than the out‐of‐plane one. The introduction of silane during metal‐organic vapor phase epitaxial growth not only allows for n‐type Si extrinsic doping, but also results in the increase of more than one order of magnitude in the domain size (up to ≈ 300 nm) and mobility (highest µ ≈ 10 cm2V−1s−1, with corresponding lowest ρ ≈ 0.2 Ωcm). To qualitatively compare the mean domain dimension in κ‐Ga2O3 epitaxial films, non‐destructive experimental procedures are provided based on X‐ray diffraction and Raman spectroscopy. The results of this study pave the way to significantly improved in‐plane conduction in κ‐Ga2O3 and its possible breakthrough in new generation electronics. The set of cross‐linked experimental techniques and corresponding interpretation here proposed can apply to a wide range of material systems that suffer/benefit from domain‐related functional properties. [ABSTRACT FROM AUTHOR]

The interfacial properties of a planar SnO/κ-Ga 2 O 3 p-n heterojunction have been investigated by capacitance-voltage ( C - V ) measurements following a methodological approach that allows consideration of significant combined series resistance and parallel leakage effects. Single-frequency measurements were carried out in both series- and parallel-model measurement configurations and then compared to the dual-frequency approach, which permits us to evaluate the depletion capacitance of diode independently of leakage conductance and series resistance. It was found that in the bias region, where the dissipation factor was low enough, they give the same results and provide reliable experimental C - V data. The doping profile extracted from the C - V data shows a nonuniformity at the junction interface that was attributed to a depletion of subsurface net donors at the n-side of the diode. This attribution was corroborated by doping profiles and carrier distributions in the n and p sides of the heterojunction obtained from the simulation of the measured C - V data by the Synopsys Sentaurus-TCAD suite. Hall effect measurements and Hg-probe C - V investigation on single κ-Ga 2 O 3 layers, either as-grown or submitted to thermal treatments, support the hypothesis of the subsurface donor reduction during the SnO deposition. This study can shed light on the subsurface doping density variation in κ-Ga 2 O 3 due to high-temperature treatment. The investigation of the SnO/κ-Ga 2 O 3 heterointerface provides useful hints for the fabrication of diodes based on κ-Ga 2 O 3 . The methodological approach presented here is of general interest for reliable characterization of planar diodes.