The Eq.(4.49) concentration relationships are valid for any conceivable positioning of the Fermi level. Nc and Nv, the effective density of states, are of course readily computed for a given material and temperature: the 300 K values of these constants for Ge, Si, and GaAs are listed in Table 4.2A.[At 300 K, Nc,v = (2.510 × 1019/cm3) (m*n,p/m0)3/2.]F1/2(η), on the other hand, is obtained from literature tabulations, through direct computation, or by the use of analytical approximations.