Voltage-controlled of photocurrent in silicon planar metal-semiconductor-metal structures

Abstract

The bias-controllable photocurrent characteristic by using planar MSM structures with both depleted and undepleted regions under dc and ac optical illumination condition has been proposed at the active area. The structure has two co-planar Mo/n-Si Schottky-barrier junctions on silicon of resistivity 9-12 Ω-cm and the electrode separation is 20 m. 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. Therefore, this structure is expected to show the output photocurrent as the function of not only optical illumination intensity but applied bias due to laterally spreading of space-charge-region (SCR). 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 100Hz-100 kHz photoresponse properties. It was found that this structure shown an appreciable voltage controllability of the photocurrent of this structure.