Papers by Keyword: Dopant Energy Level

Abstract: Electronic structures of silicon with carbon, indium, or indium-carbon dimers were calculated to investigate the interaction between indium and carbon in X center due to the indium-carbon dimers. Ab initio calculations were carried out mainly for basic Si₇₁H₆₀, C-Si₇₀H₆₀, In-Si₇₀H₆₀, and InC-Si₆₉H₆₀ clusters. The results showed that : (i) the X level was observed at E_HOMO + 0.42 eV in the InC-Si₆₉H₆₀ which was a little bit shallower than E_HOMO + 0.44 eV of the corresponding substitutional In in the In-Si₇₀H₆₀, (ii) dominant constituents of density of states of the X level were the partial densities of states of In and Si, and (iii) the X level had the antibonding nature between In and C.

Abstract: It is known that acceptor-carbon complexes have ionization energies less than those of the corresponding substitutional, separate acceptors in silicon. We present the formation mechanism for a shallower acceptor energy level called an X level that is due to an indium- carbon pair. Ab initio calculation methods were used to evaluate electronic structures and lattice relaxations of silicon with indium, carbon or a carbon-indium dimer. The results shows that the bonding interaction between the 5p orbitals of the indium atom and the 3sp orbitals of the silicon atoms bound with the indium atom mainly determines the ionization energy of the X level, and the ionic bonding interaction of the carbon atomic orbitals with the indium atomic orbitals in the X level enables the bonding interaction of the orbitals between the indium atom and the silicon atom to lower the corresponding indium acceptor level, and then to form the shallower X level.

Abstract: The total energies of donor-acceptor-donor D₂A trimer codopants (D = As and Sb, A = B, Al, Ga, In and Tl) in Si and their electronic geometrically stable structures were studied using ab initio calculations in order to propose new dopants for the formation of ultra shallow junctions with high carrier concentrations in the source/drain regions. The results of the calculations indicated that the trimer codopants were formed in Si and were stable. The trimer codopants are also able to activate the inactive complexes As₂V and Sb₂V by codoping acceptor atoms that occupy vacant sites. In particular, As₂Al, As₂Ga, Sb₂B and Sb₂Ga resulted in both shallower donor levels and higher solid solubility compared to traditional single donor atoms such as As and Sb.