Specific heat of silicon in the millidegree region

The low lattice specific heat of silicon in the cryogenic regime makes it eminently suitable for particle bolometry. In fact, the lattice specific heat becomes so low in the millidegree regime that electronic contributions from ${10}^{14}$ ${\mathrm{cm}}^{\mathrm{-}3}$ electrically active impurities can exceed it. Various mechanisms that can produce an electronic specific heat are discussed quantitatively and compared with the lattice specific heat. It is concluded that with moderate care the electronic effects can be reduced to a level that will not interfere with particle bolometry in the millidegree range.