Growth of 4H-SiC epilayers with low surface roughness and morphological defects density on 4° off-axis substrates

摘要

In situ etching and epitaxial growth have been performed on 4H-SiC 4° off-axis substrates with 100 mm diameter. In situ etching process optimizations lead to obtain step-bunching free epilayer surfaces with roughnesses of 0.2 nm and 0.8 nm, which were grown on the substrates with and without chemical mechanical polishing, respectively. Yet the epilayer surfaces free of step-bunching are more likely to suffer from various types of morphological defects than the ones with step-bunching. An increase in chlorine/silicon ratio during epitaxy can effectively suppress the appearance of defects on the step-bunching free epilayer surfaces. Using optimized epitaxial processes, we can obtain the total morphological defects density lower than 1 cm~(-2) on 4H-SiC epilayers with surface roughness of 0.2 nm.