High-quality Mg-doped p-type Ga₂O₃ crystalline thin film by pulsed laser

We investigated the epitaxial growth of Mg-doped Ga₂O₃ thin films on (0001)-sapphire substrates by pulsed laser deposition (PLD). The thin films were grown on sapphire at 900 °C, with a laser energy of ~ 80 mJ/cm², under various oxygen partial pressures (P_O = 0.01 mT, 10 mT, and 200 mT) using a Ga₂O₃:Mg(1 mol%) PLD target. The X-ray diffraction, X-ray photoelectron spectroscopy, kelvin probe force microscopy, photoelectron spectroscopy in atmosphere, ultraviolet–visible absorption spectrum, and transmission electron microscopy (TEM) were used to characterize the crystalline nanostructure and doping profile of the as-deposited thin films. The energy band diagram (obtained from the characterization data) reveals a strong shift in the Fermi level (E_F) of the Ga₂O₃:Mg thin films with respect to the undoped Ga₂O₃ toward the valence band, exhibiting p-type semiconducting behavior. The TEM results show that the films are monocrystalline for both as-deposited pure and Mg-doped Ga₂O₃. Also, comparing the measured optical band gap between the pure Ga₂O₃ (E_BG ~ 4.85 eV) and Ga₂O₃:Mg (E_BG ~ 5.2 eV) indicates a band gap increase (ΔE_BG ~ 0.35 eV) in the doped sample, which can be used for ultraviolet photodetectors and power electronic devices.