Papers by Author: Lia Trapaidze

Abstract: Fe-implanted n-/p-type 4H-SiC samples were investigated by deep level transient spectroscopy (DLTS). In order to be able to separate Fe-related defect centers from defects caused by implantation damage, a corresponding Ar-profile was implanted. No Fe-related defects were observed in n-type 4H-SiC, while two Fe-related centers could be identified in p-type 4H-SiC. The electrical behavior of these centers is donor-like.

Abstract: Intrinsic defects in 3C-SiC are generated by implantation of H+- and He+-ions or irra¬diation with high energy electrons. The defect parameters and the thermal stability of the observed defects are determined. The capture-cross-section of the W6-center is directly measured by variation of the filling pulse length. The charge state of the W6-center is obtained from double-correlated DLTS investigations according to the Poole-Frenkel effect.

Abstract: The authors investigated the effect of preannealing on N-/Al-coimplanted and over-oxidized Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs). The preannealing process causes a decrease of the Hall mobility and the effective mobility, and an increase of the interface state density. Secondary ion mass spectroscopy (SIMS) measurements revealed that the N concentration at the SiO2/SiC interface in preannealed samples is lower than in not-preannealed samples, which might be the reason for in the increase of the interface state density. In MOSFETs without preannealing, more N atoms are piled up at the SiO2/SiC interface, leading to the lower interface state density and higher mobility.

Abstract: 3C-SiC/SiO2-capacitors are fabricated by over-oxidation of an implanted Gaussian nitrogen (N) profile and investigated by conductance spectroscopy. A double peak structure is observed in the conductance spectra indicating two types of traps, which change their charge state at identical time constant, however, which are located at different energy positions in the bandgap of 3C-SiC. The experimental G/w-V and C-V characteristics are simulated and the existence of two types of traps is verified in the framework of a theoretical model.