Modulation doping in organic thin films
July 2017
The field of organic electronics has attracted great interest from the industry within the past years. Flexible, light-weight, efficient and low-cost electronic devices such as organic light-emitting diodes or solar cells have created a growing multi-billion euro market. However, organic electronics are also still a highly relevant topic for fundamental research since a basic understanding of how molecular properties can be translated into device properties is still missing.
Almost 40 years ago the concept of modulation doping has been demonstrated for GaAs transistors and nowadays literally all ultra-high-frequency devices in application are based on this so-called high electron mobility transistor (HEMT) idea. In such HEMT devices, the charge carrier mobility can be increased by orders of magnitudes since charge carrier transport occurs at a GaAs/GaAlAs heterostructure where the impu-rity scattering can be suppressed significantly. Furthermore, in such HEMT devices, the threshold-voltage can be controlled by doping of the wide gap GaAlAs layer without sacrificing the charge carrier mobility in the GaAs channel. Even if the charge carrier mobility in organic semiconductors is significantly lower than in GaAs, the charge carrier transport is also often limited by impurity scattering at the interface between the organic semiconductor and the gate insulator material. Also here the concept of modulation doping can help to improve the charge carrier transport substantially. The challenge, however, lies in the realization of ultra-clean organic heterostructures and a controlled doping in order to adjust the threshold voltage.
The aim of this work is to realize an organic heterostructure system and demonstrate the concept of modulation doping for an organic thin-film transistor device. After selecting a group of promising semiconductor materials, the formation of the heterostructure between a doped wide band gap material and an undoped lowband gap material will be studied by various techniques (e.g. current-voltage measurements, impedance spectroscopy, ultra-violet photoelectron spectroscopy ,...). In a second step, this knowledge of the heterostructure formation will be used to build an organic thin-film transistor and the ultimate target is to study the temperature dependent charge carrier transport within such a organic HEMT device.
The IAPP is a place where more than 120 physicists, chemists and engineering are working together on virtually all topics related to organic electronics – fundamentals and applications. Hence, the IAPP provides a perfect platform for the application to interact with other scientists in order to get a broad overview on otherresearch topics on organic electronics
Contact person:
© Kai Schmidt/IAP
Dr. Hans Kleemann
ODS group (Organic Devices and Structures)
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