Modification of Semiconductor-Dielectric Interface in Organic Light-emitting Field-effect Transistors
- PDF / 567,484 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 215 Views
1154-B05-93
Modification of Semiconductor-Dielectric Interface in Organic Light-emitting Field-effect Transistors
Yan Wang,1 Ryotaro Kumashiro,1 Naoya Komatsu,1 and Katsumi Tanigaki1,2 1 Department of Physics, Graduate school of Science, Tohoku University, Sendai, 980-8578, Japan. 2 World Premier International Research Center, Tohoku University, Sendai, 980-8578, Japan.
ABSTRACT In this work, ambipolar rubrene single crystal field-effect transistors (FETs) with PMMA modification layer and Au/Ca as electrodes were fabricated. The electron mobility was studied in these devices. PMMA modification layer on the surface of SiO2 is necessary for electron behavior. We found that the device with PMMA modified insulator and Au-Ca asymmetric metals possessed hole mobility and electron mobility of 1.27 and 0.017 cm-2/V s, respectively. Furthermore, the shift of light emitting with applied gate voltage was observed in this device. INTRODUCTION Light-emitting field-effect transistors (LE-FETs) are attracting much attention due to their applications in lighting, displays and circuits [1-3]. Light-emitting FETs on Si-based transistors are difficult to be achieved because of the very weak light emitting probability from the excitonic states in silicon due to its inherent indirect band gap; while organic semiconductors are known to be able to show very efficient electro-luminescence. In addition, ambipolar characteristics are possible in organic semiconductors, i.e., both electrons and holes can simultaneously be injected into a uniform semiconducting layer to create excitonic states, which enables strong light emission [4]. These recent results have triggered scientific community to have further intensive studies on exploring organic light-emitting field-effect transistors (OLEFETs). However, the charge carriers, especial electrons, are easily trapped when they are injected from electrodes or during their transportation and accumulation in the interface between the semiconductor and the dielectric layer [5, 6]. The inefficient electron transportation in the interfaces and injection from electrodes result in the low electro-luminescence quantum efficiency. In order to improve the electro-luminescence quantum efficiency, many researches are being carried out to increase the injection efficiency of electron from electrode as well as the transport efficiency in the channel. In this work, we studied the electron mobility in the FET devices with PMMA modification layer and Au/Ca as electrodes. Also, we chose the rubrene single crystals as the organic semiconductor due to its high hole mobility [7]. EXPERIMENT
The rubrene single crystals were grown by physical vapor deposition in a stream of argon gas [8]. A heavily doped silicon wafer with a 200-nm thermally grown SiO2 layer (ε= 3.9) was used as the substrate. The 100-nm polymethylmethacrylate (PMMA) film (ε= 3.7) was spin coated onto the SiO2 surface. Rubrene single crystals were laminated on these substrates by electrostatic interaction. The top contact electrodes were deposited by
Data Loading...
