An investigation was made of continuous tuning of the emission wavelength in two types of InAsSb/InAsSbP diode heterolasers: three-layer structures with combined electrical and optical confinement and five-layer structures with separate confinement. In three-layer structures the emission wavelength initially decreases by 2–4 A with increasing current and then increases by 10–15 A. In five-layer structures the emission wavelength mainly decreases. This difference is attributed to the better flow of carriers in the bulk of the active region in five-layer structures as compared with three-layer ones.