Rev. Phys. Appl. (Paris) 12, 263-266 (1977)
DOI: 10.1051/rphysap:01977001202026300

Electroabsorption by impurities and defects in semi-insulating CdTe

G. Neu, Y. Marfaing, R. Triboulet et M. Escorne

Laboratoire de Physique des Solides, C. N. R. S., 1, place A. Briand, 92190 Meudon/Bellevue, France

Abstract
Electroabsorption experiments have been conducted on semi-insulating CdTe prepared by THM without intentional doping, and with addition of chlorine. Three groups of optical transitions due to localized levels have been observed in the photon energy range from 1.2 eV to 1.6 eV : - transitions from the valence band to shallow donor levels (Ec - 0.02, 0.03 eV), associated with chlorine or group III donors, - transitions from shallow acceptors (Ev + 0.05 eV) to the conduction band, - transitions from a deep acceptor level (Ev + 0.13 eV) to a shallow donor level. The latter level is usually attributed to a donor-cadmium vacancy complex, which prompted us to undertake a more systematic study of the transition. Various electroabsorption spectra were recorded as a function of temperature, crystal orientation and light polarization. Strong dichroic effects were observed, the analysis of which should allow one to determine the symmetry of the complex involved.

Résumé
Des expériences d'électroabsorption extrinsèque permettent de comparer les spectres des défauts dans CdTe compensé non dopé et dopé au chlore de 1,2 à 1,6 eV. Trois groupes de transitions sont relevés : - des transitions bande de valence-niveaux donneurs semi-profonds (Ec - 0,02 à 0,03 eV) liés à la présence du chlore et d'impuretés du groupe III, - des transitions à partir de niveaux accepteurs peu profonds (Eo + 0,05 eV) vers la bande de conduction, - une transition de basse énergie (Ec + 0,13 eV). Cette dernière est étudiée en fonction de l'orientation du cristal et de la polarisation de la lumière afin de préciser la nature du défaut qu'elle implique, et particulièrement sa symétrie.

PACS
7155F - Impurity and defect levels in tetrahedrally bonded nonmetals.
7820F - Birefringence condensed matter.
7820J - Electro optical effects condensed matter.
7850G - Impurity and defect absorption in semiconductors.

Key words
cadmium compounds -- chlorine -- deep impurities -- dichroism -- II VI semiconductors -- impurity and defect absorption spectra of inorganic solids -- shallow donor levels -- shallow acceptors -- deep acceptor level -- dichroic effects -- semiinsulating CdTe -- CdTe:Cl -- electroabsorption -- II VI semiconductor -- localised defect levels -- travelling heater method -- impurities