Crystal growth and design of Sn-doped β-Ga2O3: Morphology, defect and property studies of cylindrical crystal by EFG

Abstract

The cylindrical Sn: β-Ga2O3 crystal with high crystalline quality was successfully designed and grown by the innovative edge-defined film-fed growth (EFG) method equipped with a cylindrical Iridium die. The challenges for the growth of Sn: β-Ga2O3 crystals were overcome by optimizing the design of an afterheater. The growth morphology of cylindrical β-Ga2O3 crystal was studied using a theoretical model and the results from experimental crystal growth. The order of importance of growth conditions affecting β-Ga2O3 crystal growth morphology was examined, based on the morphological features of cylindrical β-Ga2O3 crystals obtained by the EFG and Czochralski methods. The iridium inclusions with three shapes were observed in bulk β-Ga2O3 crystal, and the formation mechanism was carefully discussed. The optical bandgap and valence band maximum (VBM) of Sn: β-Ga2O3 crystal were calculated to be 4.74 eV and 3.49 eV by absorption spectra and X-ray photoelectron spectroscopy (XPS), respectively. The corresponding surface barrier height (Φsurf) was 1.25 eV. The carrier concentration of 5.95 × 1018 cm−3 was characterized by capacitance-voltage (C-V) measurement. By the Hall measurement, the carrier mobility and resistivity were estimated to be around 51 cm2 V−1 s−1 and 3.55 × 10–2 Ω cm, respectively.