Electronic and optical properties of Zn-doped β-Ga2O3 Czochralski single crystals

beta-Ga2O3 has several soluble deep acceptors that impart insulating behavior. Here, we investigate Zn doping (0.25 at. %) in bulk Czochralski and vertical gradient freeze beta-Ga2O3. Representative crystals were assessed for orientation (electron backscatter diffraction and Raman spectroscopy), purity (glow discharge mass spectrometry and secondary ion mass spectrometry), optical properties (ultraviolet to near infrared absorption), and electrical properties (resistivity and current-voltage). Purity measurements indicate that Zn evaporation is insufficient to inhibit doping of Zn into beta-Ga2O3. Hybrid functional calculations show Zn substitutes nearly equally on tetrahedral and octahedral sites, with less than similar to 0.1 eV preference for the octahedral (Ga-II) site. Furthermore, calculations show that Zn-Ga acts as a deep acceptor with trapping levels similar to 1.3 and similar to 0.9 eV above the valence band for one and two holes, respectively. The solubility and electronic behavior of Zn dopants are consistent with measured concentrations >1 x 10(18) atoms/cm(3) and electrical measurements that show resistivity 10(11)-10(13) omega cm, with no p-type conduction.