Methods for the reduction of the micropipe density in SiC single crystals

• Published in: Journal of materials science 2007-08, Vol.42 (15), p.6148-6152
• Main Authors: Liu, Jun Lin, Gao, Ji Qiang, Cheng, Ji Kuan, Yang, Jian Feng, Qiao, Guan Jun
• Format: Article
• Language: English
• Subjects: Activated carbon; Carbon; Condensed matter: structure, mechanical and thermal properties; Crucibles; Crystal growth; Crystals; Defects and impurities in crystals; microstructure; Density; Devices; Dislocation density; Edge dislocations; Exact sciences and technology; High voltages; Inclusions; Linear defects: dislocations, disclinations; Liquid phases; Materials science; Mathematical analysis; Physics; Reduction; Screw dislocations; Silicon carbide; Single crystals; Structure of solids and liquids; crystallography; Van Arkel process
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-006-1166-5

Micropipes are very harmful for SiC devices. Even one micropipe in the active area can destroy a high-voltage SiC device. Therefore, it is necessary to reduce the density of micropipes in SiC single crystals. In the present paper, we proposed methods for reducing micropipes. Restriction of screw dislocations and decrease of inclusions are the key factors to reduce the number of micropipes. (0 0 0 1) Si-face,\[ (11\bar 20) \] and \[ (1\bar 100) \] crystal faces acted as growth surface in different experiments. Active carbon was appended to act as carbon source. The crucible and active carbon were subjected to X-ray diffraction investigation before and after growth. The experimental results indicate that the activity of the graphite crucible was low, and it decreased with the progressing crystal growth, which increased the probability of micropipe formation. Appending active carbon can act as ample carbon source for crystal growth. The reduction of micropipes was achieved by the restrained formation of Si liquid phase. Using \[ (11\bar 20) \] and \[ (1\bar 100) \] crystal faces as the growth surfaces the generation of micropipes was restricted, as no new micropipe generated on the \[ (11\bar 20) \] and \[ (1\bar 100) \] crystal faces. At the same time, the density of edge dislocations is reduced considerably.