Theoretical studies on the optical properties of group-III elements doped SiCNTs

Silicon carbide nanotubes (SiCNTs) have broad application prospects in optoelectronic devices. Based on first principles calculation, the influence of group III elements X (X = B, Al, Ga and In) doping on the optical properties of SiCNTs was studied. At 250–620 nm, because the hole concentration of X_C-SiCNTs (when C is substituted) is less than that of X_Si-SiCNTs (when Si is substituted), the minority carrier lifetime is longer than that of X_Si-SiCNTs, therefore, the absorption peak of X_C-SiCNTs is low and wide, while that of X_Si-SiCNTs is high and narrow. Starting from 400 THz to 500 THz, with the increase of photo-generated carriers, the photoconductivity of X_Si-SiCNTs and X_C-SiCNTs increases, reaching the maximum at 700–800 THz. As the recombination rate increases, the conductivity begins to decrease, and it drops to a minimum near 1000 THz. Both dielectric constant and reflectivity show that SiCNTs doped with Si sites exhibit metallic characteristics at 340–380 nm.