Poster abstract

The group II-element Beryllium is expected to act as a doubly charged acceptor in silicon carbide (SiC). Although two acceptor levels at 0.42 eV and 0.60 eV above the valence band edge have been found in Be-doped SiC [1], Be is, alternatively, known to create compensation when introduced in p-doped crystals [2]. Recently, Deep Level Transient Spectroscopy (DLTS) experiments have been performed using the stable 9-Be isotope [3, 4] revealing several deep band gap states whose assignment to Be-correlated defects is, however, still uncertain. To identify Be-related deep levels in the band gap of SiC, DLTS measurements were performed repeatedly during the elemental transmutation of 7-Be to 7-Li. The radioactive isotope 7-Be was recoil-implanted into p-type as well as n-type 4H-SiC for radiotracer experiments. The DLTS spectra of p-type 4H-SiC exhibit one peak of time-dependent height. It describes the decreasing concentration of the element Be with the half-life of the nuclear decay (T_1/2=53.3d). Thus, one level at 1.06(5) eV above the valence band edge is identified to be Be-correlated. In n-type 4H-SiC, neither Be- nor Li-correlated deep levels have been found in the investigated part of the band gap within the measurement accuracy.

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