Electrical and optical properties and defects of (100)- and (001)-oriented V-doped β-Ga2O3 crystals grown by EFG

Altering the n-type conductivity and optical properties of ultra-wide bandgap β-Ga 2 O 3 by impurity doping has been a topic of research interest in the semiconductor field. Simultaneously, β-Ga 2 O 3 with a monoclinic structure has exhibited interesting anisotropy. In this study, (100) and (001) V-doped β-Ga 2 O 3 crystals were synthesized by the edge-defined film-fed growth (EFG) method, and their structural, electrical and optical properties, and defects were systematically investigated. V-doped β-Ga 2 O 3 crystals with a (100) plane have a better crystalline quality and flatter surface than those with a (001) plane. Compared with undoped crystals (∼10 16 cm −3 ), the carrier concentration of the (100) and (001) V-doped β-Ga 2 O 3 substrates only increased to 4.30 × 10 17 cm −3 and 1.92 × 10 17 cm −3 , respectively, which was related to the V x O y clusters formed by excess V as trapping traps and the carbon DX center as an electron capture trap formed by the relaxation of C atoms in the direction opposite to that of the C–O bond. The generation of absorption peaks and flat regions in the transmittance spectra was attributed to the introduction of V doping. The etch pit morphology and Raman peak intensity on the surfaces of the (100) and (001) V-doped β-Ga 2 O 3 substrates were different owing to the anisotropy of the monoclinic lattice structure. These results contribute to the understanding of the influence of V and anisotropy on β-Ga 2 O 3 crystals and expand their applications in electrical and optical fields. • The (100) and (001) V-doped β-Ga 2 O 3 crystals were fabricated using the EFG technique. • The abnormality in the crystal electrical properties was related to impurity C and excess V. • The optical properties and etch pit morphology of the (100) and (001) V-doped β-Ga 2 O 3 substrates differed owing to the anisotropy of the monoclinic structure.