The absorption tail of undoped and Si-doped GaN films was investigated at different temperatures and under applied electric field. It was found that the spectral dependence of logarithm of absorption coefficient is combined of two linear functions: In[alpha (hv)] = C-1 + (hv - E-g)/U-1 for hv < 3.42 eV and In[alpha (hv)] = C-2 + (hv - E-g)/ U-2 for 3.44 < hv < 3.5 eV with Urbach energies U-1 =400-470 meV and U-2 =10-20 meV. The influence of an electric field effect on the absorption spectra follows the Dow and Redfield theory. It was shown that the intrinsic electric field about 10(5) V/cm exists in our samples. The implemented analysis of the absorption spectra gives the qualitative method of film characterization. Crown copyright.