General goal of investigations is to introduce new solutions and applications in joining technologies of solids (e.g. metal-semiconductor or semiconductor-semiconductor interfaces), develop new solutions and upgrade the theoretical models describing the behavior of semi-wide and wide bandgap materials based Schottky and combined interfaces and structures.
5.1. Investigations on the influence of technological parameters on electrical parameters of semiconductor structures.
Investigations were carried out using both measurement based (TEM, DLTS and Kelvin-Probe techniques) and numerical experiments have been carried out. The results of experimental studies were correlated with model based numerical simulations. The main attention was focused on the design of optimal and high efficient construction of GaAs and SiC diode structures with a better combination of forward, reverse and dynamic characteristics [1, 2].
The research results (method and algorithm) are used in development of on-line technique for characterization of LPE process for GaAs power semiconductor structures and SiC JBS .
PhD theses: Ants Koel (2014); Jana Toompuu (2014).
- Koel, Ants; Rang, Toomas; Rang, Galina (2014). Characterization of the temperature dependent behavior of snappy phenomenon by switch-off of power GaAs diode structures. B. Sundén; C. A. Brebbia (Eds). Heat Transfer XIII (439 - 449). Great Britain: WIT Press.
- Mizsei, János; Korolkov, Oleg; Toompuu, Jana; Mikli, Valdek; Rang, Toomas (2013). Study of surface defects in 4H-SiC Schottky diodes using a scanning Kelvin probe. Materials Science Forum, 740-742, 677 - 680.
5.2. Design of semiconductor structures and materials
A new and original way for creation of sharp hetero-polytype junction based on solid state bonding of two different polytype silicon carbide wafers using DW technique was developed. Two semiconductor wafers with smooth and clean surfaces were forced to couple with each other by Van-der-Waals forces [1, 2]. The following thermal treatment strengthened the connective forces due to transformation into siloxane forces and the next transfer to covalent connections. The first experiments showed that DW wafer-bonding technology acts effectively only then, when we sputter the extremely thin (about two atoms thin) silicon intermediate layer (acts as a clue) between two different polytypic SiC wafers to create the interface behaving like the heterojunction . The results will be used for development of SiC based High Sensitive UV sensors and High Power MOS structures.
- Kaste, Nigol; Filbert, Alexander; Mescheder, Ulrich; Rang, Toomas; Rang, Galina (2014). Process Development for 3D Laser Litography. W.P. Wilde, S.Hernandez, C. A. Brebbia (Eds). High Performance and Optimum Design of Structures and materials (139 - 150). Wessex Institute of Techonology Press (UK).
- Shenkin, Mikhail, Korolkov, Oleg, Rang, Toomas, Rang, Galina (2015). Polytypic heterojunctions for wide bandgap semiconductor materials. 7th International Conference on Computational Methods and Experiments in Materials Characterization. Wessex Institute of Technology (UK), 22-24. April 2015 in Valencia, Spain, 11 pages, (accepted).