Transient and steady decay of persistent photoconductivity in Si-dopedAlxGa1−xAs

The decay of persisent photoconductivity (PPC) in bulk ${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As:Si was investigated at 77 K. A transient decay was observed to appear if the light is shut off while the conduction-electron concentration is increasing quickly. The decay of PPC is analyzed based on the negative-U model for the DX center. It is shown that this transient indicates that the decay of the DX center goes via a neutral metastable state of ${\mathit{DX}}^0$ of silicon.