Helical dislocations in Sn-doped GaP epitaxial layers and their characterization by transmission electron microscopy

Abstract

A simple and rapid method is proposed for the analysis of helical dislocations by means of their inside-outside contrast behaviour on TEM micrographs and stereomicroscopy. This method can be applied in a straightforward manner to helices resulting originally from both screw dislocations and mixed dislocations. In general, this method corresponds substantially to the method given by Kamejima et al. (1979), although it is based on the conventions proposed by Föll and Wilkens in 1975. A discussion is given of preliminary results obtained by applying this method to helices in heavily Sn-doped GaP layers grown by liquid-phase epitaxy from Sn solution on (001)-oriented GaAs substrates. It was determined experimentally that not only pure screw dislocations but also mixed dislocations had been converted into helices.