Photoconductivity and photo-Hall density measurements using an infrared light emitting diode as the light source were carried out on single silicon delta-doped Al0.30Ga0.70As samples as a function of temperature. The samples were grown by molecular beam epitaxy at 530 degrees C and 600 degrees C, We have studied the effect of etching the cap layer on the electrical transport properties. An observed persistent photoconductivity effect is explained using a model of parallel conduction in two nearby spatially separated channels. We will present evidence that the DX center is not active for nearly ideal delta-doped samples. We have proposed that the DX-center level related to the conduction-band minimum is strongly dependent on the silicon delta-doping density and on the growth conditions.