Thermally stimulated current studies of electron and hole traps in single crystal Al2O3

The method of thermally stimulated conductivity (TSC) is applied to the study of electron and hole traps in synthetic single crystalline Al2O3 from various sources with 100 keV X-rays being used to populate the trapping states in the crystals. Samples from a given source had a characteristic TSC spectrum but there is considerable variation among the various sources with only a peak at 273 K being common to all samples. Optical bleaching and optical trap repopulation techniques are combined with the TSC studies to aid in center identification. Once a sample is exposed to X-rays the repopulation of some of the traps with low energy photons becomes possible and sequential thermal and optical stimulation may be used to cycle carriers between the deep and shallow levels without additional X-irradiation for several weeks. A tentative assignment is made of the observed TSC peaks to known lattice defects. The importance of these defects in silicon on sapphire microelectronics technology is briefly discussed.