Abstract: An improved semiconductor laser of the type composed of a sequence of semiconductor layers forming a heterostructure diode including a substantially homogeneously doped layer defining a laser active zone having a laser radiation exit face perpendicular to the layers, two respectively differently doped semiconductor layers disposed at respectively opposite sides of the active zone, a monocrystalline outer layer located in the layer sequence and spaced from one of the differently doped semiconductor layers by an additional layer, a trough-shaped recess extending essentially perpendicularly to the radiation exit face formed in the outer major surface of the monocrystalline layer, and means disposed adjacent the recess for constricting the current flow in the forward direction of the diode to a narrow strip-shaped region in the laser active zone.

Abstract: A semi-conductor laser comprising a crystal having a sequence of layers forming a heterostructure diode and which includes a laser active zone interposed between a pair of semiconductor layers. Each of these semi-conductor layers has a band gap which is greater than that of the layers within the laser active zone. The laser active zone includes a first semiconductor layer having a given band gap, and at least second and third semiconductor layers each having a band gap which is greater than that of the first layer. The first layer is contiguous with and interposed between semiconductor layers each having a band gap which is greater than that of said first layer and forms a pn-junction with one of those contiguous layers. A strip-shaped region of a uniform conductivity type diffused from the surface of the crystal penetrates into at least one layer of the laser active zone but does not penetrate into the first layer.

Abstract: In a semiconductor laser composed of a sequence of layers forming a heterostructure diode and including a substantially homogeneously doped layer defining a laser active zone having a laser radiation exit face perpendicular to the layers, the current flowing in the forward direction of the diode is constricted to a narrow, strip-shaped region in the laser active zone by providing a monocrystalline layer located in the layer sequence to be spaced from the active zone by at least one intervening, doped semiconductor layer, providing the surface of the monocrystalline layer directed away from the active zone with a trough-shaped recess extending essentially perpendicularly to said radiation exit face, and diffusing, via the surface provided with the recess, and toward the active zone, doping material which produces a doped region of same conductivity type as the intervening, doped layer, the doped region being delimited by a diffusion front substantially parallel, and corresponding in contour, to the surface pro