M O Henry

Photoluminescence lifetime, absorption and excitation spectroscopy measurements on isoelectronic bound excitons in beryllium-doped silicon

Abstract Photoluminescence lifetime measurements confirm that the intense lines seen in Be-doped Si result from exciton recombination at an isoelectronic binding centre, and in addition reveal that other weaker lines are due to a different isoelectronic binding centre. We suggest that these two binding centres may be related in the same way as are the Group III acceptors and the X-acceptors in Si. A number of excited states of the main isoelectronic bound exciton have been observed in absorption, excitation and luminescence spectra, and the density of the binding centres has been determined.

A new photoluminescence band in silicon lightly doped with copper

Abstract A new photoluminescence band is reported for silicon lightly doped with copper. The spectrum consists of five closely spaced zero-phonon lines, with the lowest energy component at 943.67(5)meV, and a sideband composed of local mode 6.4meV phonon replicas of the zero-phonon lines superimposed on a broad band. The spectrum is always accompanied by, and bears a striking resemblance to, the well-known copper-related spectrum with a zero-phonon line at 1014.7 meV. The relative intensity of the two bands depends strongly on the quench rate following diffusion and on the extent of copper doping. Annealing measurements failed to reveal a direct connection between the two centres.

Bound exciton recombination in beryllium-doped silicon

The low-temperature photoluminescence of beryllium-doped silicon is dominated by a system with sharp no-phonon lines at approximately 1.077 eV with well resolved phonon-assisted replicas at lower energies. The temperature dependence of the relative intensities of the no-phonon lines and of the phonon-assisted structure is similar to that which has been observed for electron-hole recombination at axial isoelectronic traps in gallium phosphide. Using Zeeman spectroscopy the recombination centre in beryllium-doped silicon is shown to have (001) symmetry and is identified with beryllium substitutional-interstitial pairs which are expected to predominate in this material. A weak acceptor-like bound exciton spectrum is also reported.

The isoelectronic centre in beryllium-doped silicon. I. Zeeman study

The luminescence associated with exciton decay at an isoelectronic centre in beryllium-doped silicon has been studied by Zeeman spectroscopy. The centre is shown to have a (001) axis of symmetry and has been identified with a pair of beryllium atoms occupying a substitutional site (an interstitialcy). Unlike previous isoelectronic centres described in the literature, there is strong evidence for significant mixing of the Gamma 7 and Gamma 8 valence-band-derived hole states which is considered to be due to the small spin-orbit splitting of the beryllium atom. This, together with the phonon-assisted structure, suggests that the centre can be identified with an isoelectronic donor. However, it also renders the group theoretical formalism used for the analysis of the Zeeman data incompatible with the usual spin Hamiltonian approach. Nevertheless, it has been possible to derive approximate electron and hole g-values of 2.1 and 1.2, respectively.

Bound exciton recombination at Mn-Zn pair centres in silicon

Abstract The low temperature photoluminescence of silicon doped with manganese and zinc consists of a broad vibronic band with zero-phonon lines at 944.80±0.1meV and 945.8±0.1meV. The spectrum is assigned to isoelectronic bound exciton recombination at neutral Mn-Zn pair centres known to exist in the samples.

A zinc-related isoelectronic bound exciton in silicon

Abstract Photoluminescence (PL), photoluminescence excitation (PLE), and photoluminescence lifetime measurements are reported for a newly-discovered optical centre in a silicon sample diffused with iron and zinc. The PL spectrum consists of two thermalizing no-phonon lines, each with sharp low energy local mode phonon replicas in addition to a broad multi-phonon sideband. The no-phonon lines, at 1059.93±0.05 and 1075.12±0.05meV, are attributed, respectively, to transitions from the spin triplet and singlet states of an isoelectronic bound exciton (IBE). Other states of the IBE are observed at 1108.4±0.5, 1110.0±0.5 and 1133.2±0.5meV in the PLE spectrum, which also shows sharp local mode phonon replicas. The energy level structure is consistent with IBE states formed by a hole and an electron subject to a large ground state valley-orbit splitting, and bound at the centre by ≈82meV.

Uniaxial stress studies of the Be pair bound exciton absorption spectrum in silicon

The authors report the results of preliminary uniaxial stress studies of the beryllium pair isoelectronic bound exciton absorption spectrum in silicon. The results confirm that the exciton behaves as an isoelectronic acceptor.

A uniaxial stress study of a copper-related photoluminescence band in silicon

Abstract The photoluminescence (PL) spectrum of silicon lightly doped with copper and rapidly quenched from 1100°C to room temperature is dominated by a vibronic band with five zero phonon lines in the region of 943 meV. We report the results of a uniaxial stress study on the two lowest energy lines in the spectrum. The behaviour is found to be consistent with T to A transitions occurring at a defect with Td symmetry. The lowest energy line has a J = 1 excited state and the ground state is non-paramagnetic. The results suggest a singly charged positive interstitial copper atom as a possible candidate for the centre.

Excitation density dependence of the luminescence from bound multi-exciton complexes in phosphorus doped silicon

The luminescence associated with bound multi-exciton complexes in phosphorus doped silicon has been investigated as a function of excitation density. The variation of the relative intensities of the luminescence lines with excitation density is in agreement with the predictions of the Kirczenow shell model (1977) but in conflict with recent decay time studies. New features in the luminescence spectrum are also reported.

Fine structure in the bound exciton and multiple bound exciton luminescence from aluminium-doped silicon

A high-resolution investigation has been made of the luminescence associated with the decay of excitons bound to neutral Al acceptors in Si. The principal bound exciton line, associated with the transition A degrees X to A degrees , shows a thermalizing structure due to J-J coupling between the two holes and the electron at the acceptor site. The first satellite line on the low-energy side of the principal bound exciton line shows a doublet structure with a component separation and intensity ratio similar to two of the components of the principal line, identifying it with the transition A degrees XX to A degrees X. The second satellite line is a singlet. These observations support one of the recent models for multiple bound exciton transitions.