Direct energy gap group IV semiconductor alloys and quantum dot arrays in SnxGe1-x/Ge and SnxSi1-x/Si alloy systems

Citation
R. Ragan et al., Direct energy gap group IV semiconductor alloys and quantum dot arrays in SnxGe1-x/Ge and SnxSi1-x/Si alloy systems, MAT SCI E B, 87(3), 2001, pp. 204-213
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY
ISSN journal
0921-5107 → ACNP
Volume
87
Issue
3
Year of publication
2001
Pages
204 - 213
Database
ISI
SICI code
0921-5107(200112)87:3<204:DEGGIS>2.0.ZU;2-X
Abstract
The narrow gap semiconductor alloys SnxGe1-x and SnxSi1-x offer the possibi lity for engineering tunable direct energy cap Group IV semiconductor mater ials. For pseudomorphic SnxGe1-x alloys grown on Ge (001) by molecular beam epitaxy, an indirect-to-direct bandgap transition with increasing Sn compo sition is observed, and the effects of misfit on the bandgap analyzed in te rms of a deformation potential model. Key results are that pseudomorphic st rain has only a very slight effect on the energy gap of SnxGe1-x alloys gro wn on Ge (001) but for SnxGe1-x alloys grown on Ge (111) no indirect-to-dir ect gap transition is expected. In the SnxSi1-x system, ultrathin pseudomor phic epitaxially-stabilized alpha -SnxSi1-x alloys are grown on Si (001) su bstrates by conventional molecular beam epitaxy. Coherently strained alpha -Sn quantum dots are formed within a defect-free Si (001) crystal by phase separation of the thin SnxSi1-x layers embedded in Si (001). Phase separati on of the thin alloy film, and subsequent evolution occurs via growth and c oarsening of regularly-shaped alpha -Sn quantum dots that appear as 4-6 nm diameter tetrakaidecahedra with facets oriented along elastically soft < 10 0 > directions. Attenuated total reflectance infrared absorption measuremen ts indicate an absorption feature due to the alpha -Sn quantum dot array wi th onset at similar to 0.3 eV and absorption strength of 8 x 10(3) cm(-1), which are consistent with direct interband transitions. (C) 2001 Elsevier S cience B.V. All rights reserved.