Charge modulation spectroscopy for probing ambipolar carrier injection into pentacene field effect transistors

Ambipolar carrier behavior in pentacene field effect transistor (FET) is studied using charge modulation spectroscopy (CMS) measurement in combination with displacement current measurement. According to the CMS measurement, signal modulation under the positive gate voltage that promotes electron injection into pentacene layer was clearly observed in vacuum, and the modulation disappeared after exposure to air of the device. The displacement current measurement in vacuum suggesting the presence of the electron injection well supported the CMS results.