Carrier transport in silicon-rich oxide (SRO) was studied under illumination using the standard current versus voltage and capacitance versus voltage measurements. Al/SRO/Si metal-oxide-semiconductor (MOS)-like structures were used, and SRO layers with different thickness and excess Si concentration were deposited by low-pressure chemical vapor deposition (CVD) technique. In reverse bias condition, two conduction regimes were observed. The photocurrent in low-voltage regime is limited by the transport mechanism of carriers; while in the high-voltage regime, it is limited by the density of photogenerated carriers. The Poole-Frenkel conduction mechanism was found to dominate the carrier transport in SRO under illumination. It was also demonstrated that high photosensitivity was achieved in this structure that is a potential visible optical sensor. (C) 2004 Elsevier B.V. All rights reserved.