Electron-spin resonance of transparent conductive oxide β-Ga2O3

β-Ga 2 O 3 crystals are one of the transparent conductive oxides (TCOs). The n-type conductivity of β-Ga 2 O 3 is attributed to an oxygen deficit. In order to examine a mechanism of the conductivity, electron-spin resonance (ESR) measurements were carried out for β-Ga 2 O 3 doped with various impurity ions (Mn, Cr, Si, Zr, Hf). A single narrow ESR line with an anisotropic g value (~ 1.96) was observed for Si, Zr, or Hf doped β-Ga 2 O 3 and ascribed to “ motional narrowing ” of electrons trapped around oxygen vacancies, namely, conduction electrons. Extinction of the narrow ESR line for Mn or Cr doped β-Ga 2 O 3 may be due to a decrease of the conduction electron density and/or a strong spin–spin interaction between the conduction electron and the paramagnetic ions. The fine structure of the ESR spectrum for Mn or Cr doped β-Ga 2 O 3 gives evidence that Mn 2 + and Cr 3 + ions substitute for octahedral Ga 3 + ions in the lattice without charge compensators.