Study of Beryllium and Beryllium-Lithium Complexes in Single-Crystal Silicon

Abstract

Professor of Physics, VPI and S.U. AbstractWhen beryllium is thermally diffused into silicon, it gives rise to acceptor levels 191 meV and 145 meV above the valence band. Quenching and annealing studies indicate that the 145-meV level is due to a more complex beryllium configuration than the 191-meV level. When Hthium is thermally diffused into a beryllium-doped silicon sample, it produces two new acceptor levels at 106 meV and 81 meV. Quenching and annealing studies indicate that these new levels are due to lithium forming a complex with the defects responsible for the 191-meV and 145-meV beryllium levels, respectively. Electrical measurements imply that the lithium impurity ions are physically close to the beryllium impurity atoms. The ground state of the 106-me V beryllium-lithium level is split into two levels, presumably by internal strains. Tentative models are proposed to explain these results. SUMMARYWhen beryllium is thermally diffused into silicon, it gives rise to acceptor levels 191 meV and 145 meV above the valence band. Quenching and annealing studies indicate that the 145-meV level is due to a more complex beryllium configuration than the 191-meV level. When lithium is thermally diffused into a beryllium-doped silicon sample, it produces two new acceptor levels at 106 meV and 81 meV. Quenching and annealing studies indicate that these new levels are due to lithium forming a complex with the defects responsible for the 191-meV and 145-meV beryllium levels, respectively. Electrical measurements imply that the lithium impurity ions are physically close to the beryllium impurity atoms. The ground state of the 106-meV beryllium-lithium level is split into two levels, presumably by internal strains. Tentative models are proposed to explain these results.

Multiple neutral and singly ionized magnesium donors in silicon

“…This interstitial behavior for magnesium impurities is very interesting since all the group-III and group-V chemical impurities occupy substitutional lattice sites in silicon. Even beryllium, another group-II element, has also been shown to be a substitutional impurity in silicon [3]. Such an unusual behavior of magnesium makes its two 3s valence electrons available as donor electrons and, thus, makes magnesium a divalent donor impurity in silicon.…”

Effect of Be segregation on NiSi/Si Schottky barrier heights

“…Here, we assume full activation of dopants. In single crystalline bulk Si Be activation has been estimated at only 10% [13]. However, the percentage of activated Be has not been studied for the temperatures used here.…”

“…Be is therefore a fast diffuser in Si. It has been proposed that Be diffuses interstitially and is trapped by vacancies [13]. Hence, Be is not suitable for high temperature processing, but the NiSi silicidation process is done at low temperature (T=500-700 °C), making it worthwhile to evaluate the DS properties of Be.…”

Peculiar Doping Behavior of Si:Be.

“…Furthermore it is believed that the inactive defects are neutral Be pairs [2] that behave as "isoelectronic centers". The isoelectronic Be center in Si has been studied experimentally with infrared absorption [3], photoluminescence [4,5], Zeeman measurements [6], and light absorption while under uniaxial stress [7].…”