System of localized excitons on oxygen complexes in CdS

Abstract

Intense CdS luminescence in the blue and green spectral regions is widely used in all areas of optoelectronics. In this spectrum band are working on lasers CdS. This paper presents the results of a study of the exciton region of the CdS spectrum based on the theory of anti-intersecting bands (bands anticrossing theory-BAC) with the involvement of broader initial data for the analysis of optical properties. Depending on the growth conditions, the presence and change of oxygen concentration and intrinsic point defects determining the composition of crystals are taken into account. The concept of the nonuniform distribution of isoelectronic oxygen centers in the bulk of CdS due to their predominant segregation on compensating stacking faults is introduced. Cathodoluminescence (CL) spectra were studied using various recording methods, excitation intensity and temperature, as well as pulsed CL at high excitation intensities. In a scanning electron microscope from local registration and a high excitation density, the emission of the edge luminescence components of CdS was detected at 300 K. To analyze the optical data, we used the capabilities of the method for constructing band models based on the BAC theory, which collects extensive and multilateral information about specific samples. A model of a CdS · O multizone with stacking faults, which determines the spectrum of edge emission is presented. An explanation of the nature of the green edge emission of cadmium sulfide as excitons localized on oxygen-containing complexes in SF layers has been obtained for the first time. It was found that the system of levels of localized excitons at stacking faults does not change either with temperature up to 300 K, or with a change in the oxygen solubility in the crystal to the limiting one. It is shown that the presence of isoelectronic oxygen centers appear itself in the electro-physical properties of crystals. Recommendations are given for the diagnostics of crystals suitable for the creation of luminescent systems or lasers that are stable in operation. Keywords: isoelectronic centers, bands anticrossing theory, localized exciton, stacking faults, point defects, stimulated radiation.