Abstract: A nitride semiconductor laser device includes an n-type AlGaN clad layer, a GaN layer, a first InGaN light guide layer, a light-emitting layer, a second InGaN light guide layer, a nitride semiconductor inter mediate layer, a p-type AlGaN layer, and a p-type AlGaN clad layer stacked in this order on a nitride semiconductor substrate, wherein the n-type AlGaN clad layer has an Al composition ratio of 3-5% and a thickness of 1.8-2.5 ?m; the first and second InGaN light guide layers have an In composition ratio of 3-6%; the first light guide layer has a thickness of 120-160 nm and greater than that of the second light guide layer; and the p-type AlGaN layer is in contact with the p-type clad layer and has an Al composition ratio of 10-35% and greater than that of the p-type clad layer.

Abstract: A nitride semiconductor laser device includes an n-type AlGaN clad layer, a GaN layer, a first InGaN light guide layer, a light-emitting layer, a second InGaN light guide layer, a nitride semiconductor inter mediate layer, a p-type AlGaN layer, and a p-type AlGaN clad layer stacked in this order on a nitride semiconductor substrate, wherein the n-type AlGaN clad layer has an Al composition ratio of 3-5% and a thickness of 1.8-2.5 ?m; the first and second InGaN light guide layers have an In composition ratio of 3-6%; the first light guide layer has a thickness of 120-160 nm and greater than that of the second light guide layer; and the p-type AlGaN layer is in contact with the p-type clad layer and has an Al composition ratio of 10-35% and greater than that of the p-type clad layer.

Abstract: A nitride semiconductor laser device includes an n-type AlGaN clad layer, a GaN layer, a first InGaN light guide layer, a light-emitting layer, a second InGaN light guide layer, a nitride semiconductor intermediate layer, a p-type AlGaN layer, and a p-type AlGaN clad layer stacked in this order on a nitride semiconductor substrate, wherein the n-type AlGaN clad layer has an Al composition ratio of 3-5% and a thickness of 1.8-2.5 ?m; the first and second InGaN light guide layers have an In composition ratio of 3-6%; the first light guide layer has a thickness of 120-160 nm and greater than that of the second light guide layer; and the p-type AlGaN layer is in contact with the p-type clad layer and has an Al composition ratio of 10-35% and greater than that of the p-type clad layer.

Abstract: A nitride semiconductor laser device includes an n-type AlGaN clad layer, a GaN layer, a first InGaN light guide layer, a light-emitting layer, a second InGaN light guide layer, a nitride semiconductor intermediate layer, a p-type AlGaN layer, and a p-type AlGaN clad layer stacked in this order on a nitride semiconductor substrate, wherein the n-type AlGaN clad layer has an Al composition ratio of 3-5% and a thickness of 1.8-2.5 ?m; the first and second InGaN light guide layers have an In composition ratio of 3-6%; the first light guide layer has a thickness of 120-160 nm and greater than that of the second light guide layer; and the p-type AlGaN layer is in contact with the p-type clad layer and has an Al composition ratio of 10-35% and greater than that of the p-type clad layer.

Abstract: In a semiconductor laser device, a p-side electrode (114) of a multilayer structure put in contact with the surface of a ridge portion (130) of a second conductive type semiconductor layer group (p-AlGaAs first upper cladding layer (108), p-AlGaAs second upper cladding layer (109), p-GaAs etching stop layer (110), p-AlGaAs third upper cladding layer (111), p-GaAs contact layer (112) and p+-GaAs contact layer (113)) is formed. The p-side electrode (114) has one or a plurality of high refractive index layers and low refractive index layers formed successively from the side put in contact with the surface of the semiconductor layer group of the second conductive type. The high refractive index layers have a refractive index of not lower than 2.5 with respect to the wavelength band of the emission laser light and a total thickness of not greater than 75 nm, while the low refractive index layers have a refractive index of not higher than 1.0 with respect to the wavelength band of the emission laser light.

Abstract: A 780 nm band semiconductor laser device has an InGaAsP well layer, phosphorous composition of which is 0.51 smaller than 0.55 to prevent spinodal decomposition in growing InGaAsP. A compressive strain of 0.65% less than 1% and more than 0.25% is introduced into the well layer to reduce threshold current thereof. Thus, the 0.78-?m band semiconductor laser device having the InGaAsP well layer stably operates for a long time even in outputting a high optical power of 100 mW or more. A tensile strain of 1.2% is also introduced into barrier layers within the active region so as to compensate the stress due to the compressive strain of the well layer. As a result, the reliability of the semiconductor laser device is further increased during a high output operation.

Abstract: In a semiconductor laser device, a p-side electrode (114) of a multilayer structure put in contact with the surface of a ridge portion (130) of a second conductive type semiconductor layer group (p-AlGaAs first upper cladding layer (108), p-AlGaAs second upper cladding layer (109), p-GaAs etching stop layer (110), p-AlGaAs third upper cladding layer (111), p-GaAs contact layer (112) and p+-GaAs contact layer (113)) is formed. The p-side electrode (114) has one or a plurality of high refractive index layers and low refractive index layers formed successively from the side put in contact with the surface of the semiconductor layer group of the second conductive type. The high refractive index layers have a refractive index of not lower than 2.5 with respect to the wavelength band of the emission laser light and a total thickness of not greater than 75 nm, while the low refractive index layers have a refractive index of not higher than 1.0 with respect to the wavelength band of the emission laser light.

Abstract: A semiconductor laser device has an n-type AlGaAs first cladding layer 2, a multiple quantum well active layer 3, and a p-type AlGaAs second cladding layer 4 formed in this order and supported by an n-type GaAs substrate 1. The multiple quantum well active layer 3 has two quantum well layers 3a and barrier layers 3b provided on both sides of each quantum well layer 3a. The quantum well layers 3a are each made of In1-v1Gav1As1-w1Pw1, while the barrier layers 3b are each made of In1-v2Gav2As1-w2Pw2. Here, v1 and v2 satisfy v1<v2, while w1 and w2 satisfy w1<w2. The barrier layers have a tensile strain with respect to the GaAs substrate, while the well layers have a compressive strain with respect to the GaAs substrate.

Abstract: A 780 nm band semiconductor laser device has an InGaAsP well layer, phosphorous composition of which is 0.51 smaller than 0.55 to prevent spinodal decomposition in growing InGaAsP. A compressive strain of 0.65% less than 1% and more than 0.25% is introduced into the well layer to reduce threshold current thereof. Thus, the 0.78-?m band semiconductor laser device having the InGaAsP well layer stably operates for a long time even in outputting a high optical power of 100 mW or more. A tensile strain of 1.2% is also introduced into barrier layers within the active region so as to compensate the stress due to the compressive strain of the well layer. As a result, the reliability of the semiconductor laser device is further increased during a high output operation.

Abstract: There is provided a semiconductor laser device, which has an oscillation wavelength that is greater than 760 nm and smaller than 800 nm, high reliability, long operating life and a high output, and an optical disk reproducing and recording apparatus that employs the semiconductor laser device. At least first and second lower clad layers 103 and 133, a quantum well active layer 105 constructed of well layers and barrier layers, first and second upper clad layers 107 and 109 are laminated on a GaAs substrate 101. The well layer is made of InGaAsP. The well layer has a great layer thickness d of 160 Å, and assuming that an optical confinement coefficient in one layer of the well layer is &Ggr;, then &Ggr;/d is set at a great value of 2.2×10−4 Å−1.

Abstract: A semiconductor laser device has an n-type AlGaAs first cladding layer 2, a multiple quantum well active layer 3, and a p-type AlGaAs second cladding layer 4 formed in this order and supported by an n-type GaAs substrate 1. The multiple quantum well active layer 3 has two quantum well layers 3a and barrier layers 3b provided on both sides of each quantum well layer 3a. The quantum well layers 3a are each made of In1−v1Gav1As1−w1Pw1, while the barrier layers 3b are each made of In1−v2Gav2As1−w2Pw2. Here, v1 and v2 satisfy v1<v2, while w1 and w2 satisfy w1<w2. The barrier layers have a tensile strain with respect to the GaAs substrate, while the well layers have a compressive strain with respect to the GaAs substrate.

Abstract: There is provided a semiconductor laser device, which has an oscillation wavelength that is greater than 760 nm and smaller than 800 nm, high reliability, long operating life and a high output, and an optical disk reproducing and recording apparatus that employs the semiconductor laser device. At least first and second lower clad layers 103 and 133, a quantum well active layer 105 constructed of well layers and barrier layers, first and second upper clad layers 107 and 109 are laminated on a GaAs substrate 101. The well layer is made of InGaAsP. The well layer has a great layer thickness d of 160 Å, and assuming that an optical confinement coefficient in one layer of the well layer is &Ggr;, then &Ggr;/d is set at a great value of 2.2×10−4 Å−1.