Semiconductor laser

An InGaAlN-based semiconductor laser device, comprising a first layer of a first conductivity type, an active layer having a smaller forbidden band than that of the first layer, and a second layer of a second conductivity type having a larger forbidden band than that of the active layer, wherein the second layer includes a flat region and a stripe-shaped projecting structure;

• a stripe-shaped optical waveguide forming layer of the second conductivity type having a larger refractive index than that of the second layer is formed on the stripe-shaped projecting structure;
• a current-constricting layer of the first conductivity type or of a high resistance is formed for covering a top surface of the flat region of the second layer, a side surface of the projecting structure of the second layer, and a side surface of the optical waveguide forming layer;
• and
• a difference between a thermal expansion coefficient of the current, constricting layer and a thermal expansion coefficient of the second layer is in a range of −4×10−9/° C. to +4×10−9/° C.,
• wherein the second layer and the current-constricting layer are formed of an InGaALN-based semiconductor material of a same composition,
• wherein the second layer is formed of A1xGa1−x N, the current-constricting layer is formed of AlyGa1−yN, and −0.08≦x−y≦0.08, and
• wherein an angle made between the flat region and a ridge corner formed by the stripe-shaped projection structure is 90 degrees or between 90 degrees and 100 degrees, and −0.04≦x−y≦0.04.

An InGaAlN-based semiconductor laser device, comprising a first layer of a first conductivity type, an active layer having a smaller forbidden band than that of the first layer, and a second layer of a second conductivity type having a larger forbidden band than that of the active layer, wherein the second layer includes a flat region and a stripe-shaped projecting structure;

• a stripe-shaped optical waveguide forming layer of the second conductivity type having a larger refractive index than that of the second layer is formed on the stripe-shaped projecting structure;
• a current-constricting layer of the first conductivity type or of a high resistance is formed for covering a top surface of the flat region of the second layer, a side surface of the projecting structure of the second layer, and a side surface of the optical waveguide forming layer;
• and
• a difference between a thermal expansion coefficient of the current-constricting layer and a thermal expansion coefficient of the second layer is in a range of −4×10−9/° C. to +4×10−9/° C.,
• wherein the second layer and the current-constricting layer are formed of an InGaALN-based semiconductor material of a same composition, and
• wherein the optical waveguide forming layer is formed of InuGa1−uN, u is between 0.02 and 0.18 inclusive and is 90% or less of an In-mix crystal ratio of a well layer included in the active layer.

An InGaAlN-based semiconductor laser device, comprising a first layer of a first conductivity type, an active layer having a smaller forbidden band than that of the first layer, and a second layer of a second conductivity type having a larger forbidden band than that of the active layer, wherein the second layer includes a flat region and a stripe-shaped projecting structure;

• a stripe-shaped optical waveguide forming layer of the second conductivity type having a larger refractive index than that of the second layer is formed on the stripe-shaped projecting structure;
• a current-constricting layer of the first conductivity type or of a high resistance is formed for covering a top surface of the flat region of the second layer, a side surface of the projecting structure of the second layer, and a side surface of the optical waveguide forming layer;
• and
• a difference between a thermal expansion coefficient of the current-constricting layer and a thermal expansion coefficient of the second layer is in a range of −4×10−9/° C. to +4×10−9/° C.,
• wherein at least one of the second layer and the current-constricting layer is formed of an InGaAlN-based super-lattice structure, and the second layer and the current-constricting layer have the same average mix crystal ratio.

An InGaAlN-based semiconductor laser device, comprising

• a first layer of a first conductivity type,
• an active layer having a smaller forbidden band than that of the first layer, and
• a second layer of a second conductivity type having a larger forbidden band than that of the active layer, wherein
• the second layer includes a flat region and a stripe-shaped projecting structure;
• a stripe-shaped optical waveguide forming layer of the second conductivity type having a larger refractive index than that of the second layer is formed between the flat region and the stripe-shaped projecting structure;
• a current-constricting layer of the first conductivity type or of a high resistance is formed for covering a top surface of the flat region of the second layer, a side surface of the projecting structure of the second layer, and a side surface of the optical waveguide forming layer;
• and
• a difference between a thermal expansion coefficient of the currentconstricting layer and thermal expansion coefficient of the second layer is in a range of −4×10−9/° C. to +4×10−9/° C., wherein an InGaAlN layer included in a super-lattice structure forming the second layer or the current-constricting layer has a thickness of 50 nm or less.