Temperature Dependence of the Iron Acceptor Level in Aluminum Oxide

Optical absorption measurements were performed on undoped and iron‐doped Al 2 O 3 single‐crystal samples cut from the same wafer. Measurements were made in the ultraviolet spectral range at 7=25° to 500°C. A shoulder observed at 4.8 eV in the absorption spectrum of the iron‐doped sample at 25°C was attributed to a valence band‐to‐iron acceptor level transition. This structure shifted to lower energies as the temperature increased at a rate of 5.6°lO −4 eV/°C.