Photoluminescence properties of N-B Co-doped fluorescent SiC

摘要

N-B co-doped SiC, as an excellent candidate for white LEDs, were prepared by the physical vapor transport growth method. Doping type and concentrations of fluorescent SiC crystals were examined by Raman spectroscopy and secondary ion mass spectroscopy measurements. The band-to-band excitation mechanism of donor and acceptor pairs (DAPs) luminescence in f-SiC has been clarified based on excitation spectroscopic measurements. The luminescence intensity of DAPs decreases with the increase of excitation source energy due to the absorption when excitation source energy is greater than 3.7 eV. Moreover, the threshold energy and the optimal excitation wavelength did not change with the carrier concentration, while the photoluminescence emission intensity increased with the decrease of carrier concentration. When the excitation power increased from 2 to 44 mW, the luminescence intensity can be well fitted by the power dependence I = aP(gamma), the higher the B doping concentration, that is, the lower the carrier concentration, the intensity is more sensitive to the excitation power change. At same time, the luminescence peaks of high doping concentration samples shift to the high energy with high excitation power. The shifts and the underlying mechanism have been discussed.