Tungsten donor

Crystal structure, Raman spectra, electrical properties, and photoluminescence of unintentionally doped (UID) and W-doped b-Ga2O3 (W:b-Ga2O3) crystals grown using the optical floating zone technique were investigated. Based on the experimental data, W6þ ions substitute Ga3þ ions mainly in the octahedral lattice site, as revealed by the Raman spectroscopic assessment of W:b-Ga2O3 crystals. The carrier concentration of 0.10 mol. % W:b-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: b-Ga2O3 decreased from 0.603 to 0.032 X cm and 153.1 to 126 cm2 V1 s1, respectively. The transmittance of W:b-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 þ VO)1, as well as the recombination of self-trapped holes (STHs) are confined between two O(II)-s sites, respectively.