Electrical Properties, Deep Levels and Luminescence Related to Fe in Bulk Semi-Insulating β-Ga2O3 Doped with Fe

Electrical properties, deep trap spectra, microcathodoluminescence (MCL) and photoluminescence (PL) spectra of bulk semi-insulating Fe doped β-Ga2O3 crystals with ohmic and Schottky contacts were studied. The Fermi level in these crystals is pinned by the Fe acceptor level near Ec-0.8 eV. This level is also dominant in high-temperature admittance spectra and in photo-induced current transient spectroscopy (PICTS) and determines the space charge region width in Schottky diodes. The concentration of the Fe acceptors filled with electrons is (1.3–1.5) × 1017 cm−3 from high-temperature/low-frequency capacitance-voltage C-V profiling and is considerably lower than the Fe concentration introduced by doping, suggesting that a considerable portion of Fe acceptors are not filled with electrons. This is important when considering the possible role of Fe centers in charge trapping in transistors. MCL and PL spectra measurements also revealed the presence of sharp lines near 1.8 eV corresponding to the 4T1→6A1 intracenter transition in Fe3+. Additional deep centers observed in photocurrent spectra had optical ionization thresholds near 1.5 eV and 2.3 eV.