Defectoscopia catodoluminescentă a semiconductorilor II-VI

Abstract

În ultimii ani au fost publicate rezultate noi privind utilizarea Bi ca dopant în Si şi GaAs. Noi de asemenea am utilizat Bi în cristalele gazdă de ZnS şi ZnSe, cu toate că raza atomică a Bi este mai mare ca raza Zn şi S. A fost cercetată influenţa tratamentului termic al monocristalelor ZnS:Al şi ZnSe:Al în topituri care conţin Bi, Zn şi Cl asupra proprietăţii luminescente cu ajutorul metodelor de defectoscopie catodoluminescentă.

Control of defect distribution requires a measurement method capable of investigating the defects on a micrometer scale. The proposed method of cathodoluminescence surveys some of the opportunities for the control of the defects in semiconductors by using a combination of different cathodoluminescence (CL) modes including colour cathodoluminescence (CCL) in the scanning electron microscopy (SEM) with computer graphics. Several design improvements including a composite CCL+BSE-contrast in the SEM should help researchers and users better understand how annealing at different thermal environments affects the optical characteristics of materials. The method of cathodoluminescence defectoscopy was applied to microcharacterization of commercial wide-band-gap A2B6 semiconductors (ZnS, ZnSe) as well to the thin diffusion layers formed in these materials in processes of annealing. The host crystals were annealed in different melts: Al, Sb, Bi and Bi+BiCl3 at 1200 K for 100 h with a subsequent tempering in air. In result, a complex characterization of subsurface diffusion layers formed in the annealed crystals has been achieved. It has been established that the process of annealing in the above-mentioned melts leads to a spatial redistribution of the impurity-defects by an extremely irregular way. The CCL image reveals also a good correlation with the CL and PL spectra recorded in different points of sample.