  Terahertz (THz) technology is rapidly evolving, and the advancement of data
and information processing devices is essential. Silicon THz microresonators
provide perfect platforms to develop compact and integrated devices that could
transform THz technology. Here we present a systematic study on the key figure
of merit of silicon THz disc microresonators - the quality factor (Q-factor) -
in dependence on the substrate's resistivity. Our results show that the
Q-factor depends linearly on the resistivity and a variation in resistivity
from 10k$\Omega$cm to 15k$\Omega$cm changes the Q-factor from 50k to 76k at
0.6THz. Moreover, we experimentally determine that the silicon material
absorption is inversely proportional to the substrate's resistivity. In
general, the presented methodology is ideally suited to precisely measure the
material absorption of low-loss materials in the THz domain, which is
challenging using conventional THz spectroscopy.
