Dependence of the excitation energies of boron in diamond on isotopic mass

Abstract

Kim et al. have reported a dependence of the infrared excitation energies of boron acceptors in diamond on the isotopic mass of the carbon atoms. We show that this change can be quantitatively interpreted as induced by a change in the hole effective mass.

Dependence of the ionization energy of shallow donors and acceptors in silicon on the host isotopic mass

“…As observed for B in diamond, 9 and expected from the model, 10 the isotopic shift in the transition energies increases with the energies of the transitions, or in other words, with decreasing final state binding energy. In order to give an accurate value for the shift in the ground state binding energy, the highest observable lines for each impurity ͑B7 for the B acceptor and 3p Ϯ for the P donor͒ were used, together with a simple extrapolation assuming that the size of the isotope shift scales linearly with the binding energy of the state involved, giving shifts of the ground state binding energy of 0.73Ϯ0.1 cm Ϫ1 for the B acceptor and 0.32 Ϯ0.1 cm Ϫ1 for the P donor ͑in both cases the binding energies are larger in 30 Si than in 28 Si).…”

“…For acceptors in diamond, the effect due to 0 has been shown to be negligible compared with the effect due to m*. 10 …”

Fundamentals and Applications of Isotope Effect in Modern Technology

“…At present time such dependence of E B $ f ðxÞ (x-isotope concentration) was found for different bound excitons in semiconductors. 20,21) The simplest approximation, in which crystals of mixed isotopic composition are treated as crystals of identical atoms having the average isotopic mass is referred to as virtual crystal approximation (VCA). 15) Going beyond the VCA, in isotopically mixed crystals one would also expect local fluctuations in the band-gap energy from statistical fluctuations in local isotopic composition within some effective volume, such as that of an exciton (see, e.g.…”

Impurity absorption spectroscopy of the deep double donor sulfur in isotopically enriched silicon

“…This has been explained as a result of the dependence of the binding energy E B on the effective mass m: and the static dielectric constant fa [20]. In the case of diamond the contribution of fa to the energy shift was found to be negligible, but for the silicon host it has to be included in the model, as it has been shown for the shallow donor phosphorus and acceptor boron [8].…”

“…Both were then kept in the furnace for 20 hours at 1100 0 e. In contrast to the normal procedure, the ampule with 34S was backfilled with argon (Ar) at a pressure of 250 mmHg. This technique has proven to successfully reduce vapour transport and thus it reduces the amount of erosion and potential causes of strain fields.…”