A separate confinement heterostructure laser device has an optical guiding region, an active region in the optical guiding region, and p-type and n-type cladding regions on opposite sides of the optical guiding region. At least one barrier layer is present within the p-type cladding region. The composition of the barrier layer is such that it has an X-minimum higher than that of adjacent parts of the p-type cladding region. The composition and/or thickness of the barrier layer is also such that it has a .GAMMA.-minimum which is higher than the X-minima of the adjacent parts of the p-type, cladding region. The thickness of the barrier layer is such as to prevent electron tunneling between the X-bands of the adjacent parts of the p-type cladding region on opposite sides of the barrier layer, and/or the compositions of the adjacent parts of the p-type cladding region on opposite sides of the barrier layer are sufficiently different from one another to prevent such tunneling.