Tungsten donors doping in β-gallium oxide single crystal

Abstract

Crystal structure, Raman spectra, electrical properties, and photoluminescence of unintentionally doped (UID) and W-doped β-Ga2O3 (W:β-Ga2O3) crystals grown using the optical floating zone technique were investigated. Based on the experimental data, W6+ ions substitute Ga3+ ions mainly in the octahedral lattice site, as revealed by the Raman spectroscopic assessment of W:β-Ga2O3 crystals. The carrier concentration of 0.10 mol. % W:β-Ga2O3 (3.92 × 1018 cm3) is more than forty times that of UID crystal (9.55 × 1016 cm3). In addition, the resistivity and mobility of 0.10 mol. % W: β-Ga2O3 decreased from 0.603 to 0.032 Ω cm and 153.1 to 126 cm−2 V−1 s−1, respectively. The transmittance of W:β-Ga2O3 crystals decreases with increasing W content (0.01, 0.05, and 0.10 mol. %) but remains high in the visible wavelength range. Three distinct emissions are observed in the photoluminescence spectra: two blue emissions and a UV band emission. These bands are owing to the −1 charge states of Ga(I) vacancies (VGa1−) at the octahedral site, the −1 charge states of gallium and oxygen vacancy pairs (VGa + VO)1−, as well as the recombination of self-trapped holes (STHs) are confined between two O(II)-s sites, respectively.