Characterization of theDXcenter in the indirectAlxGa1−xAsalloy

The behavior of the $\mathrm{DX}$ center in ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As} (x\sim 0.6)$ doped with Si and Se was investigated through photo-Hall measurements. The simultaneous existence of the shallow (metastable) and deep $\mathrm{DX}$ levels has been proven by the observation of persistent photoconductivity (PPC) whose existence was questioned previously in the indirect-gap region of this alloy. The observed PPC is much smaller in magnitude than that for $x\sim 0.3$, but this was found to be a simple consequence of the deepening of the shallow $\mathrm{DX}$ state, which is responsible for the PPC.