Effect of process parameters on dislocation density in thick 4H-SiC epitaxial layers grown by chloride-based CVD on 4° off-axis substrates

摘要

The effect of process parameters such as growth temperature, C/Si ratio, etching time, and Si/H_2 ratio on dislocation density was investigated by performing KOH etching on 100 μm thick epitaxial layers grown on 4° off axis 4H-SiC substrates at various growth conditions by a chemical vapor deposition (CVD) process using a chloride-based chemistry to achieve growth rates exceeding 100 μm/h. We observe that the growth temperature and the growth rate have no significant influence on the dislocation density in the grown epitaxial layers. A low C/Si ratio increases the density of threading screw dislocations (TSD) markedly. The basal plane dislocation (BPD) density was reduced by using a proper in-situ etch prior to growth.