Study On P-type Hybrid Organic/Inorganic Metal Base Transistor

In an attempt to facilitate device fabrication processes and the reduction of production costs, a lot of work has been carried out to develop the organic semiconductor optoelectronic devices and hope that the performance of organic devices can reach or be over the traditional monocrystalline inorganic devices. That can be observed in the amounts of publications on totally organic devices or organic/inorganic hybrids devices, which are interested in industries by many large companied such as IBM, Kodak, etc. Devices like organic light-emitting diodes, organic field effect transistors and organic photo detectors, etc. have been produced in laboratories around the world over ten years and some have been achieved in the field of businiess. All those are attributed to the easy processability and simple processing technique.The present work in this thesis will focus on the studies of hybrid organic/ inorganic metal-base transistors based on organic semiconductor as the emitter.Generally the inorganic metal-base transistors can be described as two Schottky junctions in an inorganic semiconductor/metal/inorganic semiconductor structure, and the charge injection occurs via thermionic emission. In order to enhance the device performance, it is necessary to have an excellent interface at semiconductor and metal to reduce the scatter. However, the realization of a high degree of perfection and highly compatible interfaces is fairly difficult due to the effect of technique conditions and environment. The methods available for its production are technologically sophisticated and involve ultrahigh vaccum and/or high temperatures. Comparatively, the deposition of organic materials is much simpler, therefore, the processing of metal-base transistors by using organic semiconductor instead of inorganic semiconductors as the emitter is greatly simplified.In this thesis, two organic molecules, CuPc and NPB, widely utilized in OLEDs, were used as emitter to fabricate metal-base transistors and their electrical and gain characteristics are investigated. This study provides new application direction for these widely used organic semiconductor materials.Our studies show that the current gain depends on the thickness of the organic and the metal layer. The introduction of some buffer layers and multi-layer metal bases results in an excellent device performance. Our experimental results demonstrate that the substitution of the inorganic emitter by an organic one is not only possible but can be very efficient.