The density of states of the valence and conduction bands ofn‐type GaAs has been calculated for a donor density of 1017cm−3at 300 and 20 K. Both the donor‐carrier and carrier‐carrier interactions have been included. Band tails appear on both bands and the energy gap is narrowed. Calculations were also performed for a donor density of 1015cm−3at 300 and 20 K. These results show the formation of an impurity band at 20 K, whereas a band tail exists at 300 K.