The high-temperature Staebler-Wronski effect in undoped high-resistance $a$-Si:H films

At temperatures $T>400$ K the anomalous Staebler-Wronski effect in undoped high-resistance $a$-Si:H films, a monotonous increase in dark conductivity and photo conductivity on illumination and nonmonotonous variation of conductivity after illumination, has been detected. Nonmonotonous relaxation of conductivity is described by the sum of two extended exponential curves with different parameters $\tau$ and $E$. It has been shown that the detected effect can be explained by the formation of two types of metastable states, the broken bonds in silicon and electrically active atoms of uncontrolled donor impurity.