Ab initio study of substitutional impurity atoms in 4H-SiC

Abstract

We have investigated the formation energies, ionization energies, and chemical natures of substitutional group-II, III, V, and VI impurity atoms in 4H-SiC. It is shown that the impurity atoms have lower formation energies on a carbon site than on a silicon site for nitrogen, oxygen, and sulfur regardless of the crystal growth conditions, whereas the favorable sites for boron and selenium depend on the composition. With the exception of the above elements, impurity atoms always substitute on a silicon site. The cluster calculations suggest that antimony introduces a much shallower donor level than those of conventional n-type dopants such as nitrogen and phosphorus. However, its high energy of formation will make it difficult to dope SiC with a high impurity concentration. These results suggest that antimony is a good candidate for an extremely shallow n-type dopant.

Fine structure in electronic transitions attributed to nitrogen donor in silicon carbide

“…The spectra are dominated by two steplike drops in the capacitance that correspond to electronic levels with activation enthalpies of 57 and 105 meV. In accordance with literature, [4][5][6][7][8][9][10][11] we identify these levels as N(h) and N(k). Notably, the drop in capacitance due to the N(k) freeze out is relatively small: from $56 to $52 pF, see Fig.…”

“…A more recent investigation of the deeper N(k) by the donor-acceptor pair luminescence resulted in an ionization energy of 125.5 meV. 8 The findings and assignments mentioned above correlate with the trend observed in density functional theory (DFT) calculations, 9 where the ionization energies for N(h) and N(k) are estimated as 0.081 and 0.261 eV, respectively.…”

A new model for in situ nitrogen incorporation into 4H-SiC during epitaxy

“…For SiC, which belongs to the IV-IV semiconductor compounds, though the incorporation site of each dopant will not affect the doping type since all the atoms of the matrix have the same valence, it may have some secondary effects like change in dopant concentration or even in dopant ionization energy. This is the case with boron or aluminum impurities which were shown to have different ionization energies whether they incorporate on Si or C site 3 4 5 . Furthermore, polytypism renders the picture more complex since the impurities can incorporate either on cubic or hexagonal sites (noted respectively k and h in Fig.…”

X-ray Absorption Fine Structural Study of Atomic Structures and Chemical States of Dopants in 4H-SiC(0001)

“…In order to clarify the atomic structure of the active dopant site for Al-doped 4H-SiC(0001), we performed XANES simulations. Based on a previous study, Si substitutional (Al Si ) and C substitutional (Al c ) sites were proposed as the Al dopant structures in 4H-SiC, which is shown in Figure (b) and (c), respectively . Therefore, for the simulations with Al-doped 4H-SiC(0001), we used cluster sizes of ∼350 and ∼200 atoms for Al Si and Al c , respectively.…”