A study of the lasing and spontaneous emission fromp+‐n‐n+heterojunction lasers with lightly dopedn‐type active regions shows that the stimulated emission is not due to a simple band‐to‐band recombination process. It is further shown that the 300 K gain coefficient dependence on the junction current differs greatly from that predicted on the basis of band‐to‐band lasing involving a parabolic density‐of‐states distribution.