Investigation of light programmable non-volatile memory in an organic phototransistor
Excellent non-volatile memory characteristics have been demonstrated under the optoelectric conditions for organic phototransistors (OPTs). The high photosensitivity shown as reversible shifts in light-induced VTH exhibits a large memory window for programming caused by the excited immobile carriers (electron) trapped as a function of the electrical bias and the light intensity. The long life span of stored electrons also reveals promising behavior with respect to data retention as well as the electrical reliability to serve as a data storage medium with the non-volatile memory characteristic in OPTs. The VTH recovery accelerated by the reversible bias stress for the stored charges under irradiation shows that the erasing behavior is clearly brought by the discharge process of long-lived electrons occupied in deep states. Plausible mechanisms in the energy band are discussed for the programming and erasing process, which provides a fundamental understanding of the intrinsic charge storage behavior in OPTs.