Papers by Keyword: Sublimation Method

Abstract: In this paper, the effects of hydrogen concentration on growth rate, micropipe density and nitrogen concentration of 4H-SiC crystals were discussed. It was shown that the growth rate is a linear function of the hydrogen concentration, which can be explained not only by C/Si ratio but also the temperature gradient. It was also found that the micropipe density was increased rapidly when the hydrogen concentration exceed a critical value, because the defects such as Si droplets, carbon inclusions and polytype formation were generated at that time. The results of secondary ion mass spectroscopy (SIMS) showed that with increasing the hydrogen concentration, the nitrogen concentration falls down but reaches a constant value which meets the requirements for high purity semi-insulating (HPSI) SiC single crystal growth. Finally, the HPSI 4H-SiC crystals were obtained using 15% hydrogen concentration, the resistivities of wafers cut from these crystals were more than 10⁹Ω•cm, micropipe densities were less than 5cm^-2, the full width at the half-maximum (FWHM) were between 30-40 arcsec, making these wafers suitable for microwave devices fabrication.

Abstract: We found that the polarity of the 4H-SiC is reversed from Si-face to C-face by high Al doping during the physical vapor transport (PVT) growth. KOH etching and deep ultraviolet (DUV) Raman spectroscopy were used to confirm the polarity of the grown crystals. The results show the polarity inversion is occurred in the samples grown on Si-face SiC with using Al doped SiC source material.

Abstract: p-type SiC crystals doped with aluminum and nitrogen were grown by the sublimation method. We found that Al and N co-doping is effective for stabilized growth of p-type 4H-SiC polytype. We studied the relationship of polytype of grown crystals and the condition of Al and N feeding during the crystal growth. p-type 4H-SiC with p~1 x 10¹⁸ cm^-3 are stably-obtained with this method.

Abstract: The nitrogen (N) and aluminum (Al) co-doped growth of n-type 4H-SiC bulk crystals were performed by sublimation method. In the co-doping growth, we achieved the lowest resistivity of 6.9mWcm, and we also confirmed phenomenon of stacking faults suppression in spite of high N concentration more than 8 x 10¹⁹cm^-3.

Abstract: In this study, we suggest the effective enlargement method of (0001) 4H-SiC bulk crystals grown by the sublimation method using long length growth technique (LLG). This method could achieve low thermal strain and rapid enlargement growth comparing with conventional c-axis growth technique. We also demonstrated high quality enlargement growth from 2inch to  4inch of (0001) 4H-SiC by LLG.