- Email: [email protected]
A Raman scattering study of long-wavelength optical phonons in hexagonal ammonium fluoride single crystals
Solid State Communications, Vol. 16, pp. v—x, 1975.
Pergamon Press.
Printed in Great Britain
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids ‘J Phys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article.
1.
A RAMAN SCATTERING STUDY OF LONG.WAVELENGTH OPTICAL PHONONS IN HEXAGONAL AMMONIUM FLUORIDE SINGLE CRYSTALS M. Couzi, Laboratoire de Spectroscopie Infrarouge, associé au C.N.R.S., Université de Bordeaux 1,33405 Talence, France.
and A.M. White, Royal Radar Establishment, Malvern, Worcestershire, England, and P.D. Greene, Standard Telecommunication Lab. oratories, Harlow, Essex, England. A systematic study has been carried out of the incorporation of shallow acceptor dopants in highly refined VPE and LPE gallium arsenide. A detailed study of the bound exciton, free-to.bound and pair luminescence of doped layers has resulted in an identification catalogue for the various elements which has been compared with the assignments of other workers. A survey of layers prepared in various international laboratories has revealed characteristic acceptor cornpositions for the two types of preparation procedure. The first unambiguous characterisation of C in LPE and Zn in VPE layers has been made. A model for the
—
All the predicted Raman active translatory vibrations of wurtzite ammonium fluoride (space group C~)are observed and assigned on the basis of their polarization selections obtained with single crystals. The fundamental ammonium ion librations could not be detected, but a frequency of about 545 cm’ is deduced from the analysis of the observed .second order Raman spectrum. The TO—LO splitting for the A and E1 polar phonons is a lot more important than the A1 —E1 splitting (125 cm~compared to l—3cm’);thus, the effect of long-range electric forces strongly dominates over that of the anisotropy of the short-range interatomic forces. Only very weak directional dispersion could be detected on the quasi-mode spectra. From the observed TO and LO frequencies, one evaluates 3.95 in good agreement with dielectric experimental data.
distribution of Si between gallium and arsenic sites has predicted that the ratio [SIGa] I [S~s] is 0.25 for LPE and 1.6 x l0~for VPE layers which is consistent with the photoluminescence analysis. The bind. ing energies of C, Si, Ge, Zu, Cd, Be, Mg have been accurately established as 26.0, 34.5, 40.4, 30.7, 34.7, 28.0 and 28.4 meV respectively. The data on this ground state and the first excited state show a smooth relationship which approaches the theoretical data of Lipari and Baldereschi (1970).
Received 5 December 1974 Revised 3 February 1975
Received 29 October 1975 3.
2.
THE INCORPORATION AND CHARACTER— ISATION OF ACCEPTORS IN EPITAXIAL
LATTICE DYNAMICS OF HCP METALS J.C. Upadhyaya and H.P. Sinha, Department of Physics, Agra College, Agra 282002, India. —
DJ. Ashen, PJ. Dean, D.TJ. Hurle, J.B. Mullin v
Pergamon Press.
Printed in Great Britain
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids ‘J Phys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article.
1.
A RAMAN SCATTERING STUDY OF LONG.WAVELENGTH OPTICAL PHONONS IN HEXAGONAL AMMONIUM FLUORIDE SINGLE CRYSTALS M. Couzi, Laboratoire de Spectroscopie Infrarouge, associé au C.N.R.S., Université de Bordeaux 1,33405 Talence, France.
and A.M. White, Royal Radar Establishment, Malvern, Worcestershire, England, and P.D. Greene, Standard Telecommunication Lab. oratories, Harlow, Essex, England. A systematic study has been carried out of the incorporation of shallow acceptor dopants in highly refined VPE and LPE gallium arsenide. A detailed study of the bound exciton, free-to.bound and pair luminescence of doped layers has resulted in an identification catalogue for the various elements which has been compared with the assignments of other workers. A survey of layers prepared in various international laboratories has revealed characteristic acceptor cornpositions for the two types of preparation procedure. The first unambiguous characterisation of C in LPE and Zn in VPE layers has been made. A model for the
—
All the predicted Raman active translatory vibrations of wurtzite ammonium fluoride (space group C~)are observed and assigned on the basis of their polarization selections obtained with single crystals. The fundamental ammonium ion librations could not be detected, but a frequency of about 545 cm’ is deduced from the analysis of the observed .second order Raman spectrum. The TO—LO splitting for the A and E1 polar phonons is a lot more important than the A1 —E1 splitting (125 cm~compared to l—3cm’);thus, the effect of long-range electric forces strongly dominates over that of the anisotropy of the short-range interatomic forces. Only very weak directional dispersion could be detected on the quasi-mode spectra. From the observed TO and LO frequencies, one evaluates 3.95 in good agreement with dielectric experimental data.
distribution of Si between gallium and arsenic sites has predicted that the ratio [SIGa] I [S~s] is 0.25 for LPE and 1.6 x l0~for VPE layers which is consistent with the photoluminescence analysis. The bind. ing energies of C, Si, Ge, Zu, Cd, Be, Mg have been accurately established as 26.0, 34.5, 40.4, 30.7, 34.7, 28.0 and 28.4 meV respectively. The data on this ground state and the first excited state show a smooth relationship which approaches the theoretical data of Lipari and Baldereschi (1970).
Received 5 December 1974 Revised 3 February 1975
Received 29 October 1975 3.
2.
THE INCORPORATION AND CHARACTER— ISATION OF ACCEPTORS IN EPITAXIAL
LATTICE DYNAMICS OF HCP METALS J.C. Upadhyaya and H.P. Sinha, Department of Physics, Agra College, Agra 282002, India. —
DJ. Ashen, PJ. Dean, D.TJ. Hurle, J.B. Mullin v