E. C. Lightowlers

Concentration of atomic hydrogen diffused into silicon in the temperature range 900–1300 °C

Boron-doped Czochralski silicon samples with [B]~1017 cm−3 have been heated at various temperatures in the range 800–1300 °C in an atmosphere of hydrogen and then quenched. The concentration of [H-B] pairs was measured by infrared localized vibrational mode spectroscopy. It was concluded that the solubility of atomic hydrogen is greater than [Hs] = 5.6 × 1018 exp( − 0.95 eV/kT)cm−3 at the temperatures investigated.

Solubility of hydrogen in silicon at 1300 °C

The incorporation of hydrogen in boron doped Czochralski silicon heated to 1300 °C in H2 gas has been studied. The anneal was terminated by a rapid quench to room temperature giving rise to an unknown hydrogen‐related defect as well as H‐B close pairs. All the hydrogen in the crystal can be driven into such pairs by a low temperature (200 °C) anneal, after which the values of [H‐B] [D‐B] are in agreement with the total deuterium concentration, measured by secondary ion mass spectrometry. The estimated solubility of 1.5×1016 cm−3 is not affected by the isotopic mass of the hydrogen nor by the presence of boron or oxygen impurities.

Determination of low levels of carbon in Czochralski silicon

The C(3) vibrational lines at 865 and 1115 cm−1 are shown to correlate in intensity with the 790‐meV vibronic band in irradiated Czochralski silicon. The C(3)/790 meV lines may be used as a sensitive measure of the concentration of carbon in silicon.

The Role of Vacancies in Enhancing Oxygen Diffusion in Silicon

Measurements of optical bands in irradiated Si are combined with numerical modelling of the radiation induced reactions. No evidence is found for appreciable interaction of self-interstitials with O atoms for irradiations carried out at temperatures between 25 and 500°C. The reduction during electron irradiation of stress-induced dichroism in the 9μm oxygen band is shown to occur by sequential capture of a vacancy and a self-interstitial at the oxygen for irradiations carried out between 25 and 280°C. At higher temperatures repetitive capture and release of vacancies at oxygen atoms appears to dominate in the oxygen migration process.

Complex isotope splitting of the no-phonon lines associated with exciton decay at a four-lithium-atom isoelectronic centre in silicon

Abstract Isotope substitution studies and uniaxial stress measurements show that the optical centre responsible for the 1.045 eV luminescence system, produced in Li-doped Si by room temperature irradiation damage, may be identified with four Li atoms arranged in a C 3v molecular complex.

A photoluminescence investigation of local mode vibrations of the beryllium pair centre in silicon

A detailed examination of the spectrum of the isoelectronic bound exciton (IBE) recombination attributed to Be pair centres in Si reveals the presence in the sidebands of a previously unreported sharp local mode phonon of energy 104.7+or-0.5 meV (844+or-4 cm-1). The energy of this local vibrational mode is in excellent agreement with a recent prediction of 860 cm-1 for the vibrational energy of a pair of Be atoms aligned along a (111) crystal direction where one of the atoms occupies a substitutional site and the other an adjacent tetrahedral interstitial site. This result provides the most convincing evidence to date for assigning the IBE spectrum to Be pair centres with this configuration.

A Novel Near-Infrared Vibronic Series in Irradiated Silicon

In spite of the long-recognised ability of lithium to de-activate radiation damage in silicon (1), little is known about the microscopic nature of the various Li-associated complexes responsible. One notable exception is the lithium-saturated vacancy (LSV) for which it has been shown that 4 Li atoms surround the vacant lattice site to form a C3v molecular isoelectronic trap (2). Heat treatments above 400°C result in the disappearance of the LSV luminescence system and its replacement by a wide variety of new luminescence features, as shown in figure 1. We concentrate here on the lines labelled L0-L5. Although the luminescence is relatively weak, spectra from samples with differing impurity contents, irradiation doses and thermal histories reveal that this group of fairly sharp features is independent of the other vibronic luminescence bands shown. The general high purity of the starting material used in these investigations suggests that the optical centre is an intrinsic defect that has complexed with lithium, though carbon may also be involved. Isotope doping results presented later indeed show that Li is unambiguously present in the defect complex. However, here we wish to focus attention on the novel vibronic properties rather than on the nature of the defect responsible.