The emission and capture rates of DX-related centers have been studied by junction space-charge techniques at various reverse biases in silicon-doped ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As alloys for six different values of x. It is shown that for modest changes in the reverse bias, the thermal-emission rate decreases by more than an order of magntiude and the enthalpy increases by more than a factor of 2. Possible explanations for these observations are discussed.

• Received 23 June 1992

DOI:https://doi.org/10.1103/PhysRevB.47.1858