Papers by Author: Jana Toompuu

Abstract: In the present work, the kinetics of low-temperature annealing (400 °C) of 4H-SiC JBS diodes irradiated by electrons with an energy of 0.9 MeV and with a dose of 1E16 cm^-2 was studied. The dynamics of changes in I-V, C-V characteristics, as well as DLTS spectra are shown. In the course of the work, a thermal cycling effect was discovered, i.e., effect of multiple rapid cooling to the temperature of liquid nitrogen and heating of the samples. As a result of thermal cycling, the barrier capacity increases and the on-resistance (Rs) decreases. In the DLTS spectrum, a level of - 0.38 eV appears, absent in the as-irradiated diodes.

Abstract: The influence of 15 MeV proton irradiation temperatures (room temperature (RT) - 700 ° C) on the processes of defect formation in commercially available 4H-SiC JBS structures has been studied. It has been shown that the carrier removal rate does not depend on the irradiation temperature. At the same time, the irradiation temperature affected on the spectrum of introduced radiation defects. The conclusion about the possible influence of SiC crystal lattice structural defects on the processes of radiation defect formation has been made.

Abstract: This paper is a summary of the experimental study of deep levels in a SiC crystal lattice caused by diffusion welding (DW). Investigations were carried out by DLTS and Kelvin Probe methods. Investigations revealed that DLTS method is not applicable for identification of surface states. Research conducted by the Kelvin Probe method has shown an increase in the density of surface states after the diffusion welding from 2x10¹⁵ cm^-2 to 3.5x10¹⁶ cm^-2.

Abstract: In the present paper, 4H-SiC JBS diodes with "boron" p–n junctions have been investigated by means of deep-level transient spectroscopy (DLTS). The sign of the DLTS signal for all the 4H-SiC diodes under study, was positive. The "anomaly" of the DLTS spectra measured is apparently connected with the properties of "boron" p–n junctions. In particular, is presented the role of deep D-centers in recompensation of donors in the JBS diodes.