Preparation, characterization and photoelectronic properties of germanium-substituted Fe2O3 single crystals

Single crystals of germanium-substituted Fe2O3 have been grown using chemical vapour transport with tellurium tetrachloride and their crystallographic, electrical, magnetic and photoelectronic properties have been studied. Germanium-substituted Fe2O3 crystallized with the corundum structure and is an extrinsic n-type semiconductor with a room-temperature resistivity of ca. 5 Ω cm and an impurity ionization energy of 0.12 eV. Low-temperature susceptibility measurements suggest that insertion of GeIV leads to reduction of FeIII to FeII without spinel-phase inclusion. Photoelectrochemical measurements and determinations of the flatband potential by different techniques suggest that the behaviour of Fe2O3 photoanodes may be influenced by energy levels in the bandgap near the conduction band.