Neues Thema: Diamant FET Strukturen, Analyse ausstehender Basisprobleme Altes Thema:Entwicklung von Feldeffekt-Tansistorstrukturen auf Diamantbasis
Final Report Abstract
The aim of this investigation has been to improve the characteristics of diamond FET structures on H-terminated surface. These are the only diamond FET structures with microwave gain, low microwave noise and high output power (2.1 W/mm at 1 GHz) [1, 2]. Unfortunately, these devices show long term degradation and limited thermal stability. However they have also been unpassivated. Therefore the main focus of this project has been to identify a suitable passivation for the H-terminated surface and to implement subsequently field plates onto this passivation layer to improve stability and power density. In addition, despite many investigations, it has not been possible up to now to identify the physical/chemical nature of the surface acceptor, responsible for the surface channel securely, to satisfy all physical, electrochemical and electronic results uniquely. Thus, the FET structures developed on the basis of the passivation scheme developed were also designed to investigate the electronic surface properties. The following technological processing steps have been developed: - Refractory metal ohmic contacts on localized highly boron doped and oxygen terminated surface. This has substituted Au contacts on H-terminated surface with limited adhesion due to van der Waals bonding. - Passivation of the free surface by polyimides. The stability of polyimide passivation is still limited to the glass transition temperature of the film, which has been at approx. 250 °C for the PMGI used. - Passivation by ALD Al2O3 with a temperature as low as 100 °C. To enable these experiments an experimental ALD deposition apparatus was constructed. As a result of this 2 year project, first field plate and dual gate FET structures (in a MESFET/MOSFET configuration) could be realized and characterized, using this novel ALD Al2O3 oxide as passivation. In future work such field plate/dual gate structures are the basis to identify a unified electronic surface model, which is thought to be a heterojunction model. In addition, these investigations should also lead to improved power densities and improved stability.
Publications
- "Surface-channel MESFET with boron doped contact layer". NDNC 2007, Osaka, 28-31 May, Japan, paper 12-4
D. Kueck, H. El-Hajj, A. Kaiser, E. Kohn
- "Surface-channel MESFET with borondoped contact layer". Diamond Relat. Mater. 17 (2008) 732ff
D. Kueck, H. El-Hajj, A. Kaiser, E. Kohn
