Low-doped 6H-SiC n-type epilayers grown by sublimation epitaxy

Sublimation epitaxy has not yet been a technique of prime importance to grow epitaxial 6H-SiC layers because grown layers have always shown a residual net doping level higher than 1016 cm-3 and a high compensation level. We present here results obtained with an optimized technology of sublimation epitaxial growth, which can be used to obtain structurally perfect layers with a concentration of uncompensated donors as low as 1015 cm-3. These layers have been both physically and electrically characterized. Deep level transient spectroscopy indicates that the concentration of deep levels is greatly reduced. As a consequence the hole diffusion length is significantly increased up to about 2.5 μm, as confirmed by electron beam induced current measurements. So these optimized layers are envisaged for the fabrication of high voltage diodes or bipolar transistors.