A New Method for Revealing Striations in High-Resistive Floating-Zone Silicon Crystals

Striations were revealed by preferential etching of preannealed longi-tudinal crystal slices taken from high-resistive floating-zone silicon crystals. The required preannealing treatment was carried out at a temperature between 1000 ~ and 1200 ~ in a tubular furnace. A model for the mechanism of striation revealing is proposed. The influence of such striations on the performance of planar diodes is briefly discussed. Several methods have been developed during the past decade for revealing impurity striations in silicon crystals. These striations, which reflect the shape of the solid-liquid interface present during crystal growth, can easily be made visible in heavily doped material by means of the pulsed copper-plating tech-nique (1) or by preferential etching (2). For interme-diate resistivities (1-100 ohm-cm) some special etchin