Infrared Absorption Spectra due to Localized Vibration in the II-VI Compounds

Open Access
Publisher Website
Google Scholar
Abstract
The infrared absorption specra due to localized vibration of Al in ZnS, ZnSe and ZnTe, Be and Mg in ZnSe, and Li and ZnSe and CdS are measured. Aluminium shows five or six bands in zinc chalcogenides. This complexity arises from the charge compensation mechanism of Al donors in the host crystals. From the measurements of concentration dependency, of doubly doped crystal (e.g. ZnSe:Al, Li) and of heat treatment effect one of the bands is assigned to the localized mode of the unassociated Al donor: 438 (ZnS: Al), 359 (ZnSe: Al) and 313 cm-1 (ZnTe: Al). The remaining bands are due to aluminium-defect (presumably Zn vacancy) complexes, but a definite model of the complexes is yet to be determined. No such compexity arises for Be and Mg and the localized mode bands are observed at 450 for ZnSe: Be, 352, 345 and 334 cm-1 for 24Mg, 25Mg and 26Mg in ZnSe respectively. Lithium in CdS shows a very broad band at 474 (6Li) and 457 cm-1 (7Li). Lithium acts as an acceptor in doubly doped crystal: ZnSe: Al, Li. When the concentration of Li is much smaller than that of Al, the spectrum is simply the super-position of Al bands and Li band. The localized mode band of the unassociated Li acceptor appears at 412 (6Li) and 383 cm-1 (7Li) respectively. As the concentrations of both impurities become comparable, the charge compensation is established between Al donors and Li acceptors and the spectrum changes drastically. This result can be interpreted by considering the pair formation between the Al donor and the Li acceptor. The heat-treatment effect on some of the doped crystals are also described.

This publication has 0 references indexed in Scilit: