The electrical properties of epitaxial β-Ga2O3 doped with Sn (1016–9 × 1018 cm−3) and grown by metalorganic chemical vapor deposition on semi-insulating β-Ga2O3 substrates are reported. Shallow donors attributable to Sn were observed only in a narrow region near the film/substrate interface and with a much lower concentration than the total Sn density. For heavily Sn doped films (Sn concentration, 9 × 1018 cm−3), the electrical properties in the top portion of the layer were determined by deep centers with a level at Ec-0.21 eV not described previously. In more lightly doped layers, the Ec-0.21 eV centers and deeper traps at Ec-0.8 eV were present, with the latter pinning the Fermi level. Low temperature photocapacitance and capacitance voltage measurements of illuminated samples indicated the presence of high densities (1017–1018 cm−3) of deep acceptors with an optical ionization threshold of 2.3 eV. Optical deep level transient spectroscopy (ODLTS) and photoinduced current transient spectroscopy (PICTS) detected electron traps at Ec-0.8 eV and Ec-1.1 eV. For lightly doped layers, the compensation of film conductivity was mostly provided by the Ec-2.3 eV acceptors. For heavily Sn doped films, deep acceptor centers possibly related to Ga vacancies were significant. The photocapacitance and the photocurrent caused by illumination at low temperatures were persistent, with an optical threshold of 1.9 eV and vanished only at temperatures of ∼400 K. The capture barrier for electrons causing the persistent photocapacitance effect was estimated from ODLTS and PICTS to be 0.25–0.35 eV.

The Fermi level in bulk semi-insulating β-Ga2O3 doped with Fe (∼5 × 1018 cm−3) is found to be pinned near Ec − 0.85 eV. At temperatures ≥400 K, Ni Schottky diodes showed good rectification and measurable low frequency capacitance, allowing the measurement of capacitance-frequency (C-f), capacitance-voltage (C-V), and capacitance-temperature (C-T) characteristics. The activation energy and the electron capture cross section obtained were (0.75–0.82) eV and (2–5) × 10−15 cm2, in good agreement with the reported signature of the E2 electron trap assigned to Fe. The concentration of the filled centers determined from C-V was close to the concentration of residual shallow donors in undoped materials. Photoinduced current transient spectroscopy measurements showed that Fe doping does not promote the generation of high densities of deep traps other than those related to Fe.

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