Study of the structure of a GaAs single crystal doped with tellurium by projection etching

Projection etching is an effective method for studying structure, offering advantages over traditional selective etching due to the «memory» effect. The purpose of this work is to investigate the dislocation structure of a GaAs(Te) single crystal grown by the Czochralski method in the [100] crystallographic direction using the projection etching method. During the experiments, the data from projection etching were compared with those from the more common selective etching in a KOH melt. For projection etching, a so-called AB etchant and a solution without AgNO₃ were used. Etching at room temperature was performed in a «drunk barrel», and at elevated temperatures (85 – 125°C) with manual stirring. The surface of the single crystal was analyzed using optical microscopy. Panoramic images of dislocation structures on GaAs wafers were obtained in a light microscope by stitching together individual frames. By representing the image as a matrix of brightness intensity values I(x, y) ranging from 0 to 255, the effect of silver nitrate on the contrast of etching pits was investigated. A classification of etching pits based on their morphology (grooves, stripes, rectangular pits) is presented. The influence of temperature on the rate of projection etching and the necessity of mechanical stirring are noted. The results obtained can be used in the implementation of the projection etching technique for analyzing the mechanisms of dislocation motion and multiplication depending on growth conditions.

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