We demonstrate theoretically that the chemical modification of the bundles and composites containing mixture of semiconducting and metallic single-wall carbon nanotubes (SWNTs) leads to the substantial enhancement of the characteristics of their electromagnetic response in the terahertz (THz) frequency range. Boron and nitrogen doping is used to illustrate the effect. In particular, frequencies of antenna resonances in the bundles containing doped SWNTs are shifted to the blue in comparison to the ones in the bundles containing the same number of pristine SWNTs. Moreover, doping increases the resonant values of the bundles polarizability. Enhancement of the conductivity of the composite containing doped SWNTs is also demonstrated. The origin of the behavior is the metallization of the chemically modified semiconducting SWNTs in the bundles and composites due to the injection of the additional charge carriers.