We apply the nonlinearized Thomas-Fermi approximation for the calculation of the electronic structure of n-i-p-i doping superlattices at finite temperatures. A comparison with the solutions determined by the self-consistent Hartree model shows that the deviations are negligibly small even for the extreme cases of delta-doped n-i-p-i and uniformly doped n-p-n-p doping structures at any degree of excitation, whereas the computing time is reduced by orders of magnitude.