Thermally stimulated dislocation generation in silicon crystals grown by the Float-Zone method

Abstract

Based on own previous studies on dislocation generation in FZ- silicon crystals and in order to verify the location and conditions of dislocation generation and spreading, in the current work we present results from a model experiment using a measurement set-up close to the FZ process. Here, an as-grown dislocation-free FZ crystal with a diameter of 20 mm was exposed to temperature-induced strains. No mechanical surface treatment or sample preparation were applied and no mechanical stress was induced during measurement. The crystal was stepwise heated up in the temperature range from 700 °C till 1180 °C controlled by a pyrometric system. The crystal was cut into several samples and analyzed by Lateral Photovoltage Scanning (LPS), photoluminescence (PL) and etch pit density (EPD) as well as the lifetime (MDP) were measured. Our experimental results show that there is an indication that the dislocation density and the lifetime show an inverse behavior depending on the temperature increase in the investigated range. Therefore, this basic correlation known from the literature was confirmed. The area of dislocations generation and its spreading behavior could be revealed. Possible origins and correlations are discussed.