Hot-wall epitaxy (HWE) has been used to grow heterostructure lead-salt materials from which low-threshold tunable diode lasers have been made. A new HWE structure consisting of a Pb(Se, Te) layer sandwiched between two lattice-matched (Pb, Sn)Te layers has resulted in lasers of good electrical and material quality, and threshold current densities as low as 200 A∙cm−2 (at 40 K). This occurred even though this structure is expected to be nonconfining to both light and electrical carriers. This result is due to the very rapid interdiffusion of dopant atoms between the epilayers during the growth process. Dopant interdiffusion has been investigated using an etch-back technique combined with hot-point probe measurements to observe changes in the doping profiles of the structures. Very large values for the diffusion constants of dopants have been deduced from these measurements: 2.3 × 10−15 and 1.1 × 10−15 cm2∙s−1 for Bi and Tl, respectively.