DATA STORAGE MEDIUM HAVING LAYERS ACTING AS TRANSISTOR

A re-recordable data storage medium of one embodiment includes a substrate layer, a phase-changeable layer, and an intermediate layer. The substrate layer has a semiconductor type selected from p-type and n-type. The phase-changeable layer has a first phase corresponding to a first storable logical value, and a second phase corresponding to a second storable logical value. The phase-changeable layer has a semiconductor type identical to that of the substrate layer. The intermediate layer is between the phase-changeable layer and the substrate layer, and has a semiconductor type opposite to that of the phase-changeable and substrate layer. The substrate, phase-changeable, and intermediate layers act as a transistor under selective illumination of the phase-changeable layer.