Papers by Author: Erik Janzén

Abstract: Shallow N donors in n-type 4H-SiC were studied by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR). For the N donor at the cubic site (Nk) in 4H-SiC, the hyperfine (hf) constants of the interaction with the nearest neighbour (NN) 29Si atom along the c axis were determined as A = 41.07 MHz and A^ = 41.31 MHz. For other three NN Si atoms in the basal plane, the hf tensor has C1h symmetry and the principal values Axx = 5.94 MHz, Ayy = 5.06 MHz and Azz = 14.25 MHz. Our EPR and ENDOR observations unambiguously confirm that the N donor occupies the C site in 4H-SiC lattice and also reveal a considerable amount of the spin density of Nk (~23.9%) which was not obtained in previous studies.

Abstract: Deep levels in 4H- and 6H-SiC are characterized by FTIR spectroscopy. Vanadium, chromium and the silicon vacancy related center are listed together with the unidentified defects with emission and absorption in the near IR region. We suggest the UD-1, UD-3 and I-1 to be impurity related while the UD-2 and UD-4 to be intrinsic defects based on annealing behavior and the possibility to create the defect with irradiation. We have also tentatively assigned a new defect center around 1.0 eV to the carbon vacancy-antisite pair instead of the earlier assignment to the UD- 2 defect in 4H-SiC. We have shown that to get more information about the SiC samples a combination of absorption and luminescence techniques are very useful. Further, the use of below bandgap selective excitation is necessary to obtain more information about the defects present in the sample. FTIR absorption and luminescence measurements are useful tools to characterize deep levels important for both semi-insulating material as well as low doped conducting material where the free carrier lifetime is limited by deep levels.

Abstract: The Hot-Wall CVD reactor was developed for the thick epitaxial SiC layers needed for high voltage power devices but its inherent better properties – better cracking efficiency of the precursor gases and better lateral and vertical temperature homogeneity – should also influence the growth of other materials such as the III-nitrides. We will give some examples of thick SiC layers grown on either off- or on-axis substrates with this technique. We will also show that high-quality III-nitride materials can be grown.