Results are presented to show that at threshold the normalized current density increases and the spontaneous electron lifetime decreases, with increasing acceptor concentration in the active region of double heterostructure stripe geometry lasers. It is shown that, regardless of the acceptor concentration in the range from 2×1017to 3×1019cm−3, an injected electron density of about 2×1018cm−3is needed in order to achieve lasing in a 12‐&mgr;m‐wide stripe laser. Our threshold data confirm earlier experimental results of higher optical loss and a theoretical prediction of lower gain at a given current for heavily doped material. Variations in threshold current density and spontaneous lifetime as a function of acceptor concentration indicate that the laser transition proceeds by a band‐to‐band recombination mechanism rather than by a band‐to‐acceptor mechanism.