Contents 1. Introduction
For semiconductors containing shallow impurities, including n-type silicon, the variation of its resistance with temperature obeys . R_{s}=C\Gamma^{3/2}\eqno{\hbox{(1)}}
where C is proportional constant. For single crystal n-type silicon doped with deep impurities, near room temperature, the relationship between its resistance and temperature T satisfies[1]–[3] R_{d}=C\ exp[-(E_{F^{-}}E_{A})/kT]\eqno{\hbox{(2)}}
where k is Boltzmann constant, Fermi level and the deep acceptor level in the band gap of silicon containing deep acceptor impurities. For n-type Si:Au, the anomalous resistance effect of exponential term in Eq.(2) can increase the sensitivity greatly. To compare the effects of and , we take \eqalignno{&\left\vert {{dR_{d}}\over{dR_{s}}} \right\vert =\left\vert{{dR_{d}/dT}\over{dR _{s}/dT}}\right\vert=2T^{1/2}(E_{F}-E_{{\rm A}})B(T) &{\hbox{(3)}}\cr
&B(T)=\exp [-(E_{F}-E_{A})/kT]/3k}
Fermi level and the deep acceptor level of gold impurity are equal to 0.57 eV and 0.54 eV, respectively, below the conduction band in the band gap of our n-type Si:Au material and, thus, . At room temperature , we have \Bigl\vert {{dR_{d}}\over{dR_{s}}} \Bigr\vert =1.3 \times 10^{3} \eqno{\hbox{(4)}}
Our experimental measuring value iS . Therefore, the sensitivity of -breath sensor, made by Wheatstone bridge using n-type Si:Au material as bridge arms, can be increased by times, comparing with containing shallow impurities [4].
