The contact doping profile is controlled in the top-contact configuration to clarify a transistor operation based on a current injection process from the metal contact to the organic channel in a submicron channel pentacene field-effect transistor. The molecular doping in the pentacene film underneath the metal contact, in which a thin layer of iron (III) chloride was introduced, drastically changes transistor characteristics. The doping profile control directly revealed the resistive part for current injection. A model to explain the saturation behavior of the top-contact short channel organic transistor is presented.

Short-channel effect in organic thin film transistors with top-contact configuration is effectively suppressed to enhance the performance. The space charge limited current, which prevents the appearance of output saturation behavior, is sufficiently suppressed by reducing the thickness of both the pentacene film and the gate insulator. Molecular doping of the pentacene thin film in the contact reduces the contact resistance and allows a greater increase in field-effect mobility with decreasing channel length. These structural optimizations realize a submicrometer-channel transistor with clear saturation characteristics and low-voltage operation.