X-ray crystallographic study of the optically active semiconductor (GaxIn1-x)(2)Se-3

Citation
J. Ye et al., X-ray crystallographic study of the optically active semiconductor (GaxIn1-x)(2)Se-3, PHYS REV B, 62(24), 2000, pp. 16549-16554
Citations number
12
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHYSICAL REVIEW B
ISSN journal
0163-1829 → ACNP
Volume
62
Issue
24
Year of publication
2000
Pages
16549 - 16554
Database
ISI
SICI code
0163-1829(200012)62:24<16549:XCSOTO>2.0.ZU;2-B
Abstract
Crystal structures of two kinds of optically active semiconductors (Ga0.60I n0.40)(2)Se-3 and (Ga0.40In0.60)(2)Se-3, both of which are defect wurtzite structures but show different reduced c(w)/a(w) ratios, have been studied u sing powder X-ray diffraction and Rietveld analysis. The final reliability factors are as follows: R-wp = 10.00%, S = 2.4234, R-F = 4.19% for (Ga0.60I n0.40)(2)Se-3 and R-wp = 10.48%, S = 2.4324, R-F = 2.78% for (Ga0.40In0.60) (2)Se-3. The structure of (Ga0.60In0.40)(2)Se-3 with c(w)/a(w) = 1.633 is c alled the ideal defect wurtzite structure; the bond lengths are nearly the same and the bond angles are almost to be the ideal bond angle of tetrahedr al bonding 109.47 degrees. Meanwhile, the structure of (Ga0.40In0.60)(2)Se- 3 with c(w)/a(w) = 1.565 is called the layered defect wurtzite structure; t he nearest (001)(group III) and (001)(Se) layers are waved and very close t o each other as if they merged into one atomic layer. The average bond leng th along the c axis is 5.89% longer than that between the atoms in the merg ed (001)(group III) and (001)(Se) layers; the average bond angle whose one side is the bond along the c axis is 13.11% smaller than 109.47 degrees. Ba sed on these structural results, the anomalous dependence of the optical ba nd gap on composition is discussed from the view of bonding nature. The add itional ionic bonding between the merged (001) layers in the layered defect wurtzite structure makes the c parameter smaller but the band gap larger t han those of the ideal defect wurtzite structure although the ionic bonding nature is dominant for the both defect wurtzite structures.