Low-Temperature Annealing Studies in Ge

Abstract

Irradiation at ∼10°K using 1.10 Mev electrons produces very different changes in the electrical properties of n-type Ge as compared to those produced in p-type Ge. In n-type Ge, more carriers are removed per incident electron at 10°K than at 78°K. However about 50% of the removed carriers are recovered in two stages of annealing, at 34°K and 64°K, after low temperature irradiation. Irradiation at 0.315 Mev, after a 1.10 Mev irradiation, also produces recovery of about 50% of the carriers removed by the 1.10 Mev irradiation. In p-type Ge, low temperature irradiation is at least 100 times less effective in removing carriers than is the case in n type. Annealing of an irradiated p-type sample to 130°K produces no measurable change. It is concluded that the stability of close-vacancy-interstitial pairs against recombination is less in p type than in n-type Ge. A qualitative argument as to the origin of this difference in stability is presented.

Thermal Conductivity of Electron-Irradiated Germanium

“…The production rate of stable defects in germanium upon electron irradiation has been shown by Klontz and MacKay 11,12 to be dependent on the temperature and charge state of the defects. Electrical measurements, 11 ' 12 length change, 13 and stored-energy measurements 14 have given much larger production rates of defects in degenerate ^-type germanium irradiated at liquid-helium temperatures than in degenerate ^-type germanium.…”

Migration energies of point defects during electron irradiation of hydrogenated Si crystals

“…2͑a͒-͑c͒, the intensities of optical absorptions due to complexes show different dependences on the irradiation temperature. As already mentioned, two models have been proposed, 8,9 both of which assume a metastable configuration of FP's. The issue of those models is whether the charge state of FP's affects the annihilation rate ͑a charge-state-limited model͒ 9 or not ͑a barrier-limited model͒.…”

“…As already mentioned, two models have been proposed, 8,9 both of which assume a metastable configuration of FP's. The issue of those models is whether the charge state of FP's affects the annihilation rate ͑a charge-state-limited model͒ 9 or not ͑a barrier-limited model͒. 8 In any case, the defect production rate depends on the irradiation temperature as ͕1ϩg exp(E/kT)͖ Ϫ1 , where g, E, T, and k are a geometrical factor, an energy, the irradiation temperature and Boltzmann's constant.…”

“…The dependence of the generation rate of point defects, mainly of vacancies, on the irradiation temperature has been studied under another simplified assumption: The concentrations of complexes which include point defects, for example vacancy-oxygen ͑VO͒ pairs, depended only on the generation rate of point defects and not on the mobilities of point defects, since the optical-absorption intensity of VO pairs did not change due to annealing at temperatures higher than irradiation temperatures. 7 To explain those dependences, two models, 8,9 termed metastable V-I pair ͑we term them Frenkel pairs͒ models have been proposed. Both models assume the existence of metastable V-I pairs: The generation rates of point defects depend on the rates of recombination and dissociation of V-I pairs.…”

Low-Temperature Length Change Measurements of Electron-Irradiated Germanium and Silicon

“…Unfortunately at low temperature, the resistivity of pure Ge and Si becomes too large to measure, restricting electrical studies to impure materials. 11 Even at liquid nitrogen temperatures, impurities of as little as 2X 10 15 /cm 3 affect the annealing of electron-irradiated ^-type germanium. 3 Trapping of carriers in nonequilibrium states is observed at these temperatures and may be expected to complicate the interpretation of electrical measurements.…”