文档介绍：Exercise problem E Determine the phosphorus doping concentration in silicon atK 300 such that 1 percent of the donor electrons are still in the donor states. (Ans. 13 1610 49 .2 ??? cm N d ) At room temperature, then, the donor states are pletely ionized and, for a typical doping of3 16 10 ? cm , almost all donor impurity atoms have donated an electron to the conduction band. At room temperature , there is also plete ionization of the acceptor atoms. This means that each acceptor atom has accepted an electron form the valence band so that aP is zero. At typical acceptor doping concentrations, a hole is created in the valence band for each acceptor atom. This ionization effect and the creation of electrons and holes in the conduction band and valence band, respectively, are shown in Figure . The opposite plete ionization occurs atKT0?.At absolute zero degrees, all electrons are in their lowest possible energy state; that is, for an n-type semiconductor, each donor state must contain an electron, therefore ddNn? or0??dN .We must have, then, from Equation() that exp???? 0/?? kT EE fd .Since KT0?,this will occur for exp?? 0???,which means that fE >dE . The Fermi energy level must be above the donor energy level at absolute zero. In the case ofa p-type semiconductor at absolute zero temperature, the im purity atoms will not contain any electrons, so that the Fermi energ