Abstract
Low‐frequency oscillations which are light and electric‐field dependent have been observed in a positive resistance I‐V characteristic in Bi12GeO20. The photocurrent‐voltage characteristic has been interpreted in terms of space‐charge‐limited injection current theory and indicates that oscillation begins in the shallow‐trapping regime and ceases in the trap‐free insulator regime. Values for some of the material parameters involved have been calculated for the specific photoinjection conditions used.