Growth evolution of SiGe graded buffers during LPE cooling process

Low-Ge-content (up to 6.4%) SiGe compositionally graded buffers were grown on Si (0 0 1) by liquid phase epitaxy. All growths were grown with the same initial temperature and solution composition but cooled to different final temperatures. The growth transitions from two-dimensional crosshatch morphology into a three-dimensional-type morphology. The composition and strain state as a function of film depth was determined by combining results from the reciprocal space maps and scanning electron microscopy thickness measurements. This study revealed that, at first, the initial film growth is fully strained and during a longer growth process this initial film becomes fully relaxed. As the growth continued with further temperature reductions, the films increase in both Ge content and strain. The threading dislocation density (∼106 cm−2) of the buffers is low and remains roughly constant with increasing thickness for the SiGe buffers studied here.