Direct probing of selective electron and hole accumulation processes along the channel of an ambipolar double-layer field-effect transistor by optical modulation spectroscopy

摘要

By using optical modulation spectroscopy, the electronic state and selective carrier accumulation processes in the channel region of unipolar and ambipolar organic field effect transistors (OFETs) were directly probed. The modulated spectra of unipolar single-layer pentacene and C_(60) OFETs corresponding well with their I-V characteristics were understood in terms of the injected carrier induced effect. On the other hand, for the double-layer C_(60)/pentacene OFETs, it is indicated that the modulated spectra under both hole and electron accumulation cases generated mainly from the pentacene layer but with different characteristics, implying that the injected carriers accumulated at spatially separated locations.