Quantification of nitrogen in heavily doped silicon carbide by soft X-ray emission spectroscopy

Abstract

Nitrogen (N) is a crucial component in silicon carbide (SiC) crystals to control conductivity. It acts as an electron carrier that offers n-type conduction, and it is also employed for growing low-resistivity p-type SiC by co-doping with aluminum (Al). In this study, we quantified the N content in 4H-SiC using soft X-ray emission spectroscopy (SXES) combined with a scanning electron microscope (SEM). SXES analyses of 4H-SiC crystals with different N concentrations successfully quantified N concentration of 1.5 × 1019 cm−3 or higher, which fall within the range for heavily N-doped SiC crystals. Further, N concentration mapping was performed, and Al concentration in the same region was evaluated by a wavelength dispersive spectrometer (WDS) attached to the SEM. High concentrations of Al and N were identified and both dopants tended to increase with crystal growth, suggesting that their incorporation correlated with the Al-N interactions. Therefore, SXES and its combination with WDS are promising non-destructive technologies that can be employed to study the growth mechanism of SiC.