Isoelectronic bound-exciton photoluminescence in strained beryllium-doped Si{sub 0.92}Ge{sub 0.08} epilayers and Si{sub 0.92}Ge{sub 0.08}/Si superlattices at ambient and elevated hydrostatic pressure
- Department of Applied Physics and Columbia Radiation Laboratory, Columbia University, New York, New York 10027 (United States)
- Lucent Technologies, Bell Laboratories, Murray Hill, New Jersey 07974 (United States)
- The Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)
Photoluminescence (PL) from a beryllium-doped Si{sub 0.92}Ge{sub 0.08} epilayer and three different beryllium-doped Si{sub 0.92}Ge{sub 0.08}/Si superlattices (SL{close_quote}s) commensurately grown on Si(100) substrates is examined at 9 K at ambient pressure and, for the epilayer and one SL, as a function of hydrostatic pressure. In each structure, excitons bind to the isoelectronic Be pairs in the strained Si{sub 0.92}Ge{sub 0.08} layers. The zero-phonon PL peaks of the epilayer and the {ital in situ} doped 50-{Angstrom} Si{sub 0.92}Ge{sub 0.08}/100-{Angstrom} Si SL shift linearly with pressure toward lower energy at the rate of 0.68{plus_minus}0.03 and 0.97{plus_minus}0.03 meV/kbar, respectively, which are near the 0.77-meV/kbar value for Si:Be. The PL energies at ambient and elevated pressure are analyzed by accounting for strain, quantum confinement, and exciton binding. A modified Hopfield-Thomas-Lynch model is used to model exciton binding to the Be pairs. This model, in which potential wells bind electrons to a site (that then trap holes), predicts a distribution of electron binding energies when an inhomogeneous distribution of potential-well depths is used. This accounts for the large PL linewidth and the decrease of linewidth with increasing pressure, among other observations. In SL{close_quote}s, the exciton binding energy is shown to depend on the width of the wells as well as the spatial distribution of Be dopants in the superlattice. Also, at and above 58 kbar a very unusual peak is observed in one of the SL{close_quote}s, which is associated with a free-exciton peak in Si, that shifts very fast with pressure ({minus}6.02{plus_minus}0.03 meV/kbar). {copyright} {ital 1996} {ital The American Physical Society}
- OSTI ID:
- 477030
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 55, Issue 11; Other Information: PBD: Mar 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Photoluminescence and stimulated emission in Si- and Ge-disordered Al/sub x/Ga/sub 1-x/As-GaAs superlattices
Electro-and photoluminescence studies from ultrathin Si{sub m}Ge{sub n} superlattices