Semiconductor laser device and method of fabricating the same

1. A semiconductor laser device comprising:

a first cavity and a second cavity formed apart from each other over a semiconductor substrate, wherein

the first cavity includes a first buffer layer and a first semiconductor layer on the first buffer layer, the first semiconductor layer including a first lower cladding layer, a first active layer, and a first upper cladding layer, and the first semiconductor layer being formed with a stripe structure,

the second cavity includes a second buffer layer and a second semiconductor layer on the second buffer layer, the second semiconductor layer including a second lower cladding layer, a second active layer, and a second upper cladding layer, and the second semiconductor layer being formed with a stripe structure,

a window structure is provided in a region near an end face of each of the first semiconductor layer and the second semiconductor layer, the window structure being formed by diffusing an impurity,

a band gap of the first buffer layer is greater than that of the first active layer,

a band gap of the second buffer layer is greater than that of the second active layer, and

each of the first buffer layer and the second buffer layer is a layered element formed by alternately stacked n-type AlGaInAs layers and n-type AlGaInP layers.

2. The semiconductor laser device of claim 1 , wherein

the semiconductor substrate is formed of GaAs, and

a layer of the layered element closest to the semiconductor substrate is one of the AlGaInAs layers.

3. The semiconductor laser device of claim 2 , wherein the AlGaInAs layers are greater in lattice constant than the semiconductor substrate, and the AlGaInP layers are lower in lattice constant than the semiconductor substrate.

4. The semiconductor laser of claim 2 , wherein

the first cavity and the second cavity are respectively a cavity for outputting a red laser beam or a cavity for outputting an infrared laser beam, and

each of the first buffer layer and the second buffer layer is formed of a compound represented by a general formula Al a Ga b In 1-a-b As(where 0<a<1, 0 <b<1, b≦-2.4a+1.32, a+b≦1) and a compound represented by a general formula Al c Ga d In 1-c-d P(where 0<c<1, 0<d<1, d≧-c +0.53, c+d≦1).

5. A semiconductor laser device comprising:

a first cavity and a second cavity formed apart from each other over a semiconductor substrate, wherein

the first cavity includes a first buffer layer and a first semiconductor layer on the first buffer layer, the first semiconductor layer including a first lower cladding layer, a first active layer, and a first upper cladding layer, and the first semiconductor layer being formed with a stripe structure,

the second cavity includes a second buffer layer and a second semiconductor layer on the second buffer layer, the second semiconductor layer including a second lower cladding layer, a second active layer, and a second upper cladding layer, and the second semiconductor layer being formed with a stripe structure,

a window structure is provided in a region near an end face of each of the first semiconductor layer and the second semiconductor layer, the window structure being formed by diffusing an impurity,

a band gap of the first buffer layer is greater than that of the first active layer,

a band gap of the second buffer layer is greater than that of the second active layer, and

each of the first buffer layer and the second buffer layer is formed of a material represented by a general formula Al e Ga f In 1-e-fAs g P 1-g (where 0<e<1, 0<f<1, e+f<1, 0<g<1).

6. The semiconductor laser device of claim 1 , wherein

the first active layer is formed of a material represented by a general formula Al g Ga h In 1-g-l P(where 0≦g<1, 0<h≦1, g+h<1), and

the second active layer is formed of a material represented by a general formula Al i Ga 1-i As(where 0+i<1).

7. The semiconductor laser device of claim 5 , wherein the first active layer is formed of a material represented by a general formula Al g Ga h In 1-g-h P(where 0≦g<1,0<h≦1, g+h<1), and the second active layer is formed of a material represented by a general formula Al iGa 1-i As(where 0≦i<1).