In order to go deeper in the knowledge of the fundamentals of Organic Field Effect Transistors (OFETs), we have characterized different typologies of OFETs using rubrene single crystals. The latter are highly ordered organic semiconductors with which high mobility transistors can be fabricated. First we have obtained a detailed picture about the properties of a rubrene single crystal, by analyzing the current-voltage (I-V) characteristics of symmetric diodes with the Space Charge Limited Current (SCLC) theory. A low density of defects and a low density of intrinsic thermally generated carriers have been found to characterize this material. On this basis, we have analyzed metal-semiconductor-field-effect-transistors (MESFETs). These non-conventional devices have been proved to be efficient organic FETs, in which the process of charge carrier injection from the ohmic source contact is controlled by the voltage applied to a non-ohmic gate electrode. Finally, metal-insulator-semiconductor field effect transistors (MISFETs) have been considered. The (I-V) trend below the threshold voltage is not exponential, as predicted by the inorganic theory; instead, it is linear with the gate voltage and it follows a pseudo-exponential behaviour only in a narrow transition region. An alternative semi-analytical description has been provided here by taking into account the effect of a localized trap level on the distribution of free charges. The presence of this discrete trap level was highlighted by the previously conducted SCLC analysis.

(2009). Charge transport properties of organic semiconductors: application to fiels effect transistors. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2009).

Charge transport properties of organic semiconductors: application to fiels effect transistors

BRAGA, DANIELE
2009-12-18

Abstract

In order to go deeper in the knowledge of the fundamentals of Organic Field Effect Transistors (OFETs), we have characterized different typologies of OFETs using rubrene single crystals. The latter are highly ordered organic semiconductors with which high mobility transistors can be fabricated. First we have obtained a detailed picture about the properties of a rubrene single crystal, by analyzing the current-voltage (I-V) characteristics of symmetric diodes with the Space Charge Limited Current (SCLC) theory. A low density of defects and a low density of intrinsic thermally generated carriers have been found to characterize this material. On this basis, we have analyzed metal-semiconductor-field-effect-transistors (MESFETs). These non-conventional devices have been proved to be efficient organic FETs, in which the process of charge carrier injection from the ohmic source contact is controlled by the voltage applied to a non-ohmic gate electrode. Finally, metal-insulator-semiconductor field effect transistors (MISFETs) have been considered. The (I-V) trend below the threshold voltage is not exponential, as predicted by the inorganic theory; instead, it is linear with the gate voltage and it follows a pseudo-exponential behaviour only in a narrow transition region. An alternative semi-analytical description has been provided here by taking into account the effect of a localized trap level on the distribution of free charges. The presence of this discrete trap level was highlighted by the previously conducted SCLC analysis.
BORGHESI, ALESSANDRO
HOROWITZ, GILLES
rubrene, space charge limited current (SCLC), organic field effect transistor (OFET), metal-semiconductor field effect transistor (MESFET)
FIS/03 - FISICA DELLA MATERIA
English
Scuola di dottorato di Scienze
SCIENZA DEI MATERIALI - 08R
22
2008/2009
(2009). Charge transport properties of organic semiconductors: application to fiels effect transistors. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2009).
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10281/8009
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