Papers by Author: Michal Kozubal

Abstract: High-resolution photoinduced transient spectroscopy (HRPITS) has been applied to determining the properties and concentrations of radiation defect centers formed in FZ silicon single crystals subjected to doping with phosphorus in neutron transmutation processes. The studies were performed immediately after the neutron irradiation on the samples with the resistivity of the order of 10⁵ Ωcm. The preset target resistivity was around 2000 Ωcm. The N-doping effect on the material radiation damage has been demonstrated. It is shown that in the N-enriched material, the radiation defect centers with activation energies of 81, 125, 160, 185, and 390 meV are not observed and the concentrations of the defect centers with activation energies of 46, 84, 133, 140, 265, 300, 380, 460, and 546 meV are significantly lower than those in the N-free material. We also show that the majority of defect centers produced by the irradiation of FZ silicon with fast neutrons are also observed after neutron transmutation doping.

Abstract: Results of vanadium doping in PVT SiC bulk growth by the use of the seeding technique with an open seed backside are shown. Structural and electrical properties of 4H and 6H-SiC:V were investigated by a variety of experimental methods. In the crystal studied, the solubility limit of V in SiC was exceeded and structural defects consisting of V-rich precipitates occured. Electrical properties of this crystal were determined by the V3+/V4+ acceptor level. The V3+ charge state of vanadium was formed by compensating shallow donors (mainly nitrogen) and for both 4H and 6H polytypes it was detectable in optical absorption (in the near-IR range) and electron paramagnetic resonance.

Abstract: n- and p-type 6H-SiC single crystals grown by PVT method using different charge materials – poly-SiC sinter or fresh SiC powder – have been studied. An open or closed seed backside during the growth processes have been applied. In the former, a distinct decrease backside etching of the seed was observed. Crystals have been extensively characterized with respect to their purity, quality and electrical properties using complex experimental methods. For the n-type boule an axially and radially homogeneous resistivity ~0.11 cm at 300 K was observed. Electrical properties of the p-type crystal, i.e., high room-temperature resistivity of 239 cm, were affected by compensation effects between residual donors (nitrogen and oxygen) and acceptors (mainly boron).