We previously reported that it is possible to achieve bias-controllable photocurrent characteristics using planar metal-semiconductor-metal (MSM) structures with depleted and undepleted regions at the active area under optical illumination. To make the structures of this type more sensitive to dc and/or ac optical quantities, interdigitated Schottky-barrier MSM (SB-MSM) structures for visible range having voltage-controllable iris function have been fabricated and examined. By introducing an undepleted region between Schottky barriers on both sides, the depleted region width at the front surface under illumination varies with bias applied, where this region would be more sensitive to optical quantity than the undepleted region to generate the photocurrent. Making use of planar molybdenum n-type silicon molybdenum (Mo/n-Si/Mo) structures, it has been experimentally demonstrated that such a structure exhibits voltage controllability of photocurrents whilst maintaining the inherent function converting optical signal into electronic signal. An appreciable improvement in obtaining output photocurrent was confirmed from both dc and low frequency (1-20) kHz signal measurements. It was found that the experimental results are substantially explained by the simplified model of this structure. (C) 2003 Elsevier Science Ltd. All rights reserved.