Susceptors and Boats for Epitaxy
Epitaxy susceptors for gas phase epitaxy are machined from superpure graphite having a particularly homogeneous fine-grained structure (RINGSDORFF®). To seal the graphite porosity, these susceptors are typically coated with silicon carbide (CRYSTA-SIL®). SGL Group has matched the key properties of its graphite grades to the needs of the application concerned, i.e. their use as substrate material for silicon carbide-(SiC)-coated components. The thermal expansion coefficients, for instance, are silicon carbide-compatible. Layer thickness and resistivity are ideally matched to the particular application. We manufacture all common susceptor types. Prior to delivery we check them for tight dimensional tolerances and high purity to ensure their proper performance.
In the III/V gas phase epitaxy process, semiconductor layers are deposited on GaAs or InP substrates through the reaction of gaseous metal organic components.
Silicon carbide-coated graphite susceptors have been used successfully for the purpose, and sometimes also PyC coatings as an alternative to SiC coatings.
The graphite material for LPE boats must be abrasion-resistant, very dense and of high purity. The high density and low porosity of the graphite prevent the melt, and the doping elements it contains, from penetrating the graphite structure.
The design of LPE boats is complex and often very intricate. It demands tight tolerances in the machining process.