Semiconducting characteristics of lithium-doped MgO crystals

A wide band-gap crystal, appropriately doped, is shown to exhibit semiconducting properties. The electrical properties of lithium-doped MgO single crystals at moderate temperatures (373-600 K) are shown to behave like to that of a semiconductor at low temperatures: When a de voltage was applied, negative differential resistance, self-excited current oscillations, and filament-driven current were observed. The conductivity increase and the non-linear behavior of the I-V characteristics are described by an impact ionization mechanism. Avalanche breakdown can be produced with low electric fields (similar to 300 V/cm) after one hour. These conditions are much less severe than those required to produce electrical breakdown in MgO crystals at much higher fields and temperatures. We conclude that filamentary semiconducting inclusions containing [Li](0) centers imbedded in the insulator matrix are responsible for the electrical degradation.