JP3801410B2 - Semiconductor laser device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser device, and more particularly to a structure of a semiconductor laser device in which an impurity distribution in an active region is controlled and a manufacturing method thereof.
[0002]
[Prior art]
Development of an end-face window type laser with a window structure that does not absorb laser light at and near the end face to suppress deterioration of the light exit end face of the high-power laser for optical disks and achieve high reliability at high output. Has been actively conducted. The element structure of a conventional end window type laser is disclosed in IEEE J. Quantum Electron. , Vol. 29, pp. 1874-1879, 1993.
[0003]
FIG. 16 shows a perspective view of a conventional element structure. FIG. 17 is a cross-sectional view taken along the line GG ′ of FIG. 16, and FIG. 18 shows the n-type from the surface of the p-type (hereinafter referred to as p-) upper cladding layer 6 inside the ridge stripe 7 of the conventional semiconductor laser device. (Hereinafter referred to as n-) is a diagram showing the concentration distribution of p-type impurities (Zn) in the cladding layer 2.
[0004]
In FIG. 16, an n-AlGaInP lower cladding layer 2, an undoped guide layer 3, a DQW (Double Quantum Well) active layer 4, an MQB (Multi Quantum Barrier) layer 5, and a p-AlGaInP upper cladding layer 6 are formed on an n-GaAs substrate 1. To grow. Thereafter, a ZnO stripe film is selectively formed on the surface of the growth layer corresponding to the light emitting end face and the vicinity thereof, and a SiN film is formed on the other surface. N ₂ When thermal annealing is performed at 600 ° C. for 3 hours in the atmosphere, Zn diffuses from ZnO into the crystal, and the band gap of the active layer increases. The ZnO film and the SiN film are removed, a ridge stripe 7 is formed in the direction perpendicular to the ZnO stripe direction, and the ridge stripe is buried and grown by the n-GaAs current blocking layer 8.
[0005]
At the same time, the current blocking layer 8 is formed so as to cover the top of the ridge in the region where the band gap is increased by Zn diffusion. Thereafter, a p-GaAs contact layer 9 is formed on the growth layer surface. Electrodes 10 and 11 are formed on the substrate side and the growth layer side, and cleavage is performed so that the active layer whose band gap is increased by Zn diffusion becomes the emission end face. A window region 21 in which the band gap of the active layer is increased and an active region 22 inside the resonator are formed at and near the light emitting end face. Here, Si is used for the n-dopant and Zn is used for the p-dopant.
[0006]
As shown in FIG. 17, in the active region 22 inside the resonator, no current blocking layer is formed above the ridge stripe, and current is injected into the active layer inside the resonator to cause laser oscillation.
[0007]
In the conventional semiconductor laser device, a maximum light output of 150 mW is obtained at a wavelength of 670 nm, and end face deterioration is suppressed by the window effect. Furthermore, reliability exceeding 1500 hr at a high output of 50 ° C. and CW of 50 mW has been reported.
[0008]
FIG. 18 shows the concentration distribution of p-impurity (Zn) from the surface of the p-upper cladding layer 6 inside the ridge stripe 7 of the conventional semiconductor laser device to the n-cladding layer 2.
[0009]
FIG. 18A shows the concentration distribution of the window region, and FIG. 18B shows the concentration distribution of the active region. In the window region, Zn in ZnO diffuses in a large amount not only in the active layer but also in the middle of the n-cladding layer. This diffusion of Zn into the active layer causes an increase in the band gap. Also in the active region, Zn in the p-cladding layer 6 diffuses into the active layer 4 and further into the n-cladding layer 2 due to thermal annealing at the time of window formation.
[0010]
[Problems to be solved by the invention]
However, the conventional semiconductor laser device has the following problems.
[0011]
In the conventional semiconductor laser device, when thermal annealing is performed to form the window region, Zn in the p-cladding layer in the active region diffuses into the active layer. Since the Zn causes defects in the active layer, there arises a problem that the operating current increases. Furthermore, when Zn in the p-cladding layer in the active region diffuses to the n-type cladding layer, a pn junction is formed in the n-type cladding layer, resulting in an increase in operating voltage.
[0012]
The present invention has been made in view of the above. A desired window region can be formed by thermal annealing at a low temperature or in a short time, and an increase in operating current and operating voltage is prevented, thereby providing a highly reliable end window type high output. It is an object of the present invention to provide a laser element structure and a manufacturing method thereof.
[Means for Solving the Problems]
In order to solve the above-described problems, in the semiconductor laser device of the present invention, a resonator end face having an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type cap layer on a semiconductor substrate and perpendicular to each semiconductor layer. And a semiconductor laser device having a window region in which the band gap of the active layer in the vicinity of at least one end surface of the resonator is larger than the band gap of the active layer inside the resonator, and the p-type cladding layer in the window region Is a mixture of a first dopant and a second dopant having a larger diffusion constant than the first dopant, The The first dopant is present in a higher concentration than the second dopant in the p-type cladding layer in the active region other than the window region And the combination of the first dopant and the second dopant is beryllium and zinc, beryllium and magnesium, or zinc and magnesium, respectively, and has a current blocking layer on the ridge above the window region, and its length Is longer than the length of the window area It is configured.
[0013]
[0014]
[0015]
In the semiconductor laser device of the present invention, the second dopant is mainly disposed near the cap layer side of the p-type cladding layer in the window region, and the first dopant is mainly disposed near the active layer side of the p-type cladding layer in the window region. The dopant is arranged.
[0016]
[0017]
In the semiconductor laser device of the present invention, the concentration of the second dopant in the vicinity of the cap layer side of the p-type cladding layer in the window region is 1 × 10 ¹⁸ cm ^-3 1 × 10 ¹⁹ cm ^-3 The configuration is as follows.
[0018]
In the semiconductor laser device of the present invention, the concentration of the first dopant in the vicinity of the active layer side of the p-type cladding layer is 5 × 10 5. ¹⁷ cm ^-3 3 × 10 ¹⁸ cm ^-3 The configuration is as follows.
[0019]
[0020]
[0021]
In the semiconductor laser device of the present invention, the semiconductor constituent material includes at least indium, gallium, and phosphorus.
[0022]
Also, in the method of manufacturing a semiconductor laser device of the present invention, a step of growing an n-type cladding layer, an active layer, a p-type cladding layer having a first dopant and a p-type cap layer on a semiconductor substrate, and a resonator thereon A step of forming a diffusion source serving as a second dopant having a diffusion constant larger than that of the first dopant only in a portion corresponding to the vicinity of the end face, and then, a second dopant is diffused into the p-type cladding layer by thermal annealing to form a p-type And promoting diffusion of the first dopant in the cladding layer into the active layer to increase the band gap of the active layer more than inside the resonator to form a window region. The combination of the first dopant and the second dopant is beryllium and zinc, beryllium and magnesium, or zinc and magnesium, respectively. It is configured.
[0023]
[0024]
DETAILED DESCRIPTION OF THE INVENTION
1 to 15 are diagrams of a semiconductor laser device according to an embodiment of the present invention.
[0025]
[First Embodiment]
FIG. 1 is a perspective view of the structure of an end window semiconductor laser device according to the first embodiment of the present invention, FIG. 2 is a sectional view taken along line AA ′ of FIG. 1, and FIG. This is illustrated in FIG. 3 and described. 2 is a cross-sectional view in a direction parallel to the longitudinal direction of the ridge stripe in the center of the ridge stripe, and FIG. 3 is a cross-sectional view in a direction perpendicular to the longitudinal direction of the ridge stripe in the center of the resonator. It is.
[0026]
In FIG. 1, n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first lower cladding layer 101 (thickness 2 μm, carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Si), non-doped multiple quantum well active layer 102, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first upper cladding layer 103 (thickness 0.2 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be), p-In _0.5 Ga _0.5 P etching stop layer 104 (thickness 50 mm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be) is formed. The ridge stripe 105 (width 5.0 μm) is p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 Second upper cladding layer 106 made of P (thickness 1.2 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be) and p-GaAs cap layer 107 (thickness 0.3 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be)).
[0027]
Here, the non-doped multiple quantum well active layer 102 is composed of two In layers. _0.5 Ga _0.5 P well layer (thickness 80 mm) and one layer (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer (thickness 50mm) and sandwich them (Al _0.5 Ga _0.5 ) _0.5 In _0.5 It is composed of a P guide layer (thickness 300 mm).
[0028]
The light emitting end face and the vicinity thereof are configured such that the band gap of the active layer is larger than the band gap of the active layer inside the resonator.
[0029]
The side surface of the ridge stripe 105 has an n-GaAs current blocking layer 108 (thickness 1.2 μm, carrier concentration 1 × 10 ¹⁸ cm ^-3 N-GaAs current blocking layer 108 is formed on the ridge stripe at and near the light emitting end face. The I'm here. However, the current blocking layer 108 is not formed on the ridge stripe inside the resonator.
[0030]
A p-GaAs contact layer 109 (thickness 3 μm, carrier concentration 2 × 10 6) is formed on the ridge stripe and the current blocking layer. ¹⁸ cm ^-3 , Dopant Be) is formed. The length of the resonator of the semiconductor laser device of the present invention is 600 μm. Electrodes 110 and 111 are formed on the substrate side surface and the growth layer side surface.
[0031]
In addition, as shown in FIG. 1, the edge window type semiconductor laser device according to the first embodiment of the present invention has a window region 121, an active region 122, and a window region in a direction perpendicular to each layer of the semiconductor. 121.
[0032]
Therefore, for the window region 121 of the present invention, W indicating the window region is given to each layer of the semiconductor, the n-first lower cladding layer 101W in the window region, the quantum well active layer 102W in the window region, the window region. The p-first upper cladding layer 103W in the window region, the ridge stripe 105W in the window region, the p-second upper cladding layer 106W in the window region, and the p-cap layer 107W in the window region.
[0033]
Similarly, for the active region 122 of the present invention, an A indicating the active region is given to each layer of the semiconductor, the n-first lower cladding layer 101A in the active region, the quantum well active layer 102A in the active region, the active region The p-first upper cladding layer 103A in the region, the ridge stripe 105A in the active region, the p-second upper cladding layer 106A in the active region, and the p-cap layer 107A in the active region will be referred to.
[0034]
The window region 121 is a region near the end face of the end face window type semiconductor laser device, and the band gap of the active layer (102W) in the window region 121 is larger than the band gap of the active layer (102A) in the active region 122. Has been.
[0035]
Therefore, the quantum well active layer (active layer) 102 includes an active layer (102W) in the window region 121, an active layer (102A) in the active region 122, and an active layer (102W) in the window region 121.
[0036]
The first lower cladding layer 101 adjacent to the active layer 102 includes a first lower cladding layer (101W) in the window region 121, a first lower cladding layer (101A) in the active region 122, and a first lower cladding in the window region 121. Layer (101W).
[0037]
Similarly, the first upper cladding layer 103 adjacent to the active layer 102 includes the first upper cladding layer (103W) in the window region 121, the first upper cladding layer (103A) in the active region 122, and the first upper cladding layer in the window region 121. And a clad layer (103W).
[0038]
Here, the active region 122 is mainly used as a term composed of the first lower cladding layer (101A), the active layer (102A), the first upper cladding layer (103A), and the ridge stripe 105.
[0039]
Further, the window region 121 is mainly used as a term including the first lower cladding layer (101W), the active layer (102W), the first upper cladding layer (103W), and the ridge stripe 105. 1 to 3, the window regions 121 are disposed on both sides of the active region 122, but function as a semiconductor laser element having a window region as long as it is on at least one end face.
[0040]
As shown in FIG. 2, the current blocking layer 108 is formed on the second upper cladding layer 106 longer than the window region so as to cover the window region above the window region 121.
[0041]
As shown in FIG. 3, in the active region 122 inside the resonator, no current blocking layer is formed on the ridge stripe upper portion 105 (106 and 107).
[0042]
1 to 3, the p-GaAs cap layer 107W in the window region contains the first dopant Be having a small diffusion constant and the second dopant Zn having a large diffusion constant, and the concentration of Be is about. 5 × 10 ¹⁸ cm ^-3 Zn concentration is ~ 5x10 ¹⁸ cm ^-3 (Zn concentration)> (Be concentration) and (Concentration of second dopant having a large diffusion constant)> (Concentration of first dopant having a small diffusion constant).
[0043]
1 to 3, in the p-cladding layer 106A inside the resonator other than the window region, a first dopant having a small diffusion constant (for example, Be) and a second dopant having a large diffusion constant (for example, Zn) are used. And the concentration of the first dopant exists predominantly, and the relationship is (Be concentration)> (Zn concentration), and (the concentration of the first dopant having a small diffusion constant)> (diffusion constant) (Concentration of the second dopant having a large value).
[0044]
Next, terms such as “quantum well active layer”, “active layer”, “disordering of quantum well active layer”, and the like will be described.
[0045]
In the end face window type semiconductor laser device of the present invention, the band gap of the active layer in the vicinity of the end face of the resonator is larger than the band gap of the active layer inside the resonator. When the active layer is a quantum well active layer (the thickness of each layer is 0.02 μm or less (200 μm or less)), the band gap can be changed by changing the active layer. Used.
[0046]
In the case of a bulk active layer (thickness greater than 0.02 μm) thicker than the quantum well active layer, the band gap does not change only by diffusion of impurities or the like. However, when the composition of the active layer is changed, the band gap changes, and a bulk active layer can be used as the active layer of the present invention.
[0047]
The quantum well active layer is obtained by a structure in which a quantum well layer having a thickness of 0.02 μm or less and a barrier layer having a composition different from that of the quantum well layer are alternately stacked. This composition or a structure in which atoms are arranged in order is called an ordered structure. The destruction of the ordered structure due to diffusion of impurities (for example, p-dopant Be, Zn, Mg, etc.) and vacancies, changes in atomic arrangement, etc. is called “disordering of the quantum well active layer”. Due to the disordering of the quantum well active layer, the band gap of the active layer increases and a window region is formed. By arranging the band gap increasing region on the end face of the resonator, a highly reliable high-power laser without end face deterioration can be realized.
[0048]
Also, in the bulk active layer, what is arranged in an ordered manner can be called “disordering of the active layer” to change the composition and destroy the order.
[0049]
Next, a manufacturing method of the end face window type semiconductor laser device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4A shows the process from the n-GaAs substrate to the p-cap layer, and FIG. 4B shows the ZnO. _X From the formation of stripes to SiO ₂ FIG. 4C shows a process for forming a window region and an active region, and FIG. 4D shows a process for forming a ridge stripe.
[0050]
In FIG. 4A, n- (Al is formed on an n-GaAs substrate 100 by molecular beam epitaxy (MBE). _0.7 Ga _0.3 ) _0.5 In _0.5 P first lower cladding layer 101 (carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Si), (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P guide layer and two layers of In _0.5 Ga _0.5 P well layer and one layer (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer and (Al _0.5 Ga _0.5 ) _0.5 In _0.5 Non-doped multiple quantum well active layer 102 composed of a P guide layer, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first upper cladding layer 103 (carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be), p-In _0.5 Ga _0.5 P etching stop layer 104 (carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be), p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second upper cladding layer 106 (carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be) and p-GaAs cap layer 107 (thickness 0.3 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 The dopant Be) is grown.
[0051]
In FIG. 4B, ZnO _X A film is deposited on the surface of the p-cap layer 107 and ZnO having a period of 600 μm and a length of 50 μm is formed by photolithography and lift-off. _X A stripe 131 is formed, and SiO is formed thereon. ₂ A cap 132 is formed.
[0052]
In FIG. 4C, annealing was performed at 500 ° C. for 3 hours to obtain ZnO. _X The dopant Be of the first upper cladding layer 103 and the second upper cladding layer 106 is diffused into the quantum well active layer 102 immediately below the stripe row 131 to form a band gap increasing region of the active layer, that is, a window region 121. At the same time, an active region 122 is formed in a portion where there is no ZnO stripe row.
[0053]
By diffusing the dopant Be (first dopant) into the active layer, the band gap of the active layer is increased. It is considered that the dopant Zn (second dopant having a larger diffusion constant than the first dopant) serves to promote diffusion of the dopant Be (first dopant) into the active layer.
[0054]
By this step, the active layer 102 becomes the active layer (102W) of the window region 121, the active layer (102A) of the active region 122, and the active layer (102W) of the window region 121. Similarly, the first upper cladding layer 103 adjacent to the active layer 102 includes the first upper cladding layer (103W) in the window region 121, the first upper cladding layer (103A) in the active region 122, and the first upper cladding layer in the window region 121. It becomes a clad layer (103W). Similarly, the first lower cladding layer 101 adjacent to the active layer 102 includes the first lower cladding layer (101W) in the window region 121, the first lower cladding layer (101A) in the active region 122, and the first lower cladding layer in the window region 121. It becomes a clad layer (101W).
[0055]
In FIG. 4D, ZnO _X Stripe 131 and SiO ₂ The cap 132 is removed, and the ridge stripe 105 is formed by photolithography and etching.
[0056]
An n-GaAs current blocking layer 108 is buried and grown by the second MBE method on the side surface of the ridge stripe and on the ridge stripe in the window region, and a p-GaAs contact layer 109 (thickness 3 μm) is formed on the upper portion thereof. Growth is performed by the second MBE method, and electrodes are formed on the substrate side and the contact layer surface (here, details of these manufacturing methods are not shown).
[0057]
Cleaving is performed on the surface orthogonal to the ridge stripe so that the window region becomes the end face of the resonator, and the light emitting side end face is coated with a reflectance of 8% and the back face is coated with 95%. Here, the resonator length is 600 μm, and the length of the window region is 25 μm.
[0058]
By applying a voltage to the n-electrode 111 and the p-electrode 112 of the semiconductor laser device of the present invention and injecting current into the ridge stripe of the active region 122 and the corresponding active layer, the laser is emitted from the light emitting end face. Oscillation light is obtained. A maximum light output of 250 mW is obtained at a wavelength of 655 nm, and end face deterioration is suppressed by the window effect. Furthermore, high reliability exceeding 5000 h was obtained at an operating temperature of 60 ° C. and a high output of continuous oscillation of 70 mW.
[0059]
Whereas the oscillation threshold current of the conventional semiconductor laser element is 53 mA, the oscillation threshold current of the semiconductor laser element of the present invention can be reduced to 45 mA. Further, the operating voltage of the semiconductor laser device of the present invention can be reduced to 2.3V, while the operating voltage of the conventional semiconductor laser device having an optical output of 50 mW is 2.5V. Due to the current reduction and voltage reduction, the semiconductor laser device of the present invention can achieve high reliability and higher output than the conventional semiconductor laser device.
[0060]
FIG. 5 shows the concentration distribution of p-impurities (Zn, Be) from the surface of the p-cap layer 107 to the n-cladding layer 101 of the edge window type semiconductor laser device according to the first embodiment of the present invention. In FIG. 5, the vertical axis represents the concentration of p-impurities (Zn, Be), and the horizontal axis represents the region of each layer. FIG. 5A shows the concentration distribution of each layer in the window region 121, and FIG. 5B shows the concentration distribution of each layer in the active region 122.
[0061]
In the window region of FIG. 5A, Zn (second dopant) is formed on the surface of the p-GaAs cap layer 107W (5 × 10 5). ¹⁸ cm ^-3 ) To the p-cladding layer 106W, ˜1 × 10 ¹⁷ cm ^-3 It is as follows.
[0062]
Further, Be (first dopant) is formed on the surface of the p-GaAs cap layer 107W (1.5 × 10 5 ¹⁸ cm ^-3 ) To the second upper cladding layer 106W, the first upper cladding layer 103W, the non-doped multiple quantum well active layer 102W, and the first lower cladding layer 101W. In each layer, the Be concentration is 1.5 × 10 6. ¹⁸ cm ^-3 The density distribution is almost constant. By this Be diffusion, the band gap of the active layer 102W in the window region 121 is increased.
[0063]
In the active region of FIG. 5B, Zn hardly diffuses and distribution, while Be is the surface of the p-GaAs cap layer 107A (˜1.5 × 10 6). ¹⁸ cm ^-3 ) To the second upper cladding layer 106A and the first upper cladding layer 103A, and hardly diffuses into the non-doped multiple quantum well active layer 102A and the first lower cladding layer 101 (˜1 × 10). ¹⁷ cm ^-3 The following):
[0064]
From the results shown in FIGS. 5A and 5B, the following can be clearly understood. In the window region of the end face window type semiconductor laser device according to the first embodiment of the present invention, p-dopant Be (first dopant) and p-dopant Zn (second dopant) are mixed. On the other hand, in the active region, the p-dopant Be (first dopant) is present at a higher concentration than the p-dopant Zn (second dopant). The first dopant is mainly present in the vicinity of the active region side of the p-cladding layer in the window region.
[0065]
From the results shown in FIGS. 5A and 5B, the following can be clearly understood. The concentration of the first dopant is predominantly present in the p-cladding layer in the active region of the edge window type semiconductor laser device according to the first embodiment of the present invention. Further, the first dopant is hardly present in the active layer or the n-cladding layer in the active region.
[0066]
For example, the diffusion constant of Zn is 4 × 10 4 at 700 ° C. in GaAs. ^-14 cm ^-2 The diffusion constant of Be is, for example, 4 × 10 4 at 725 ° C. in GaAs. ^-16 cm ^-2 The diffusion constant of Zn is about two orders of magnitude greater than the diffusion constant of Be. In addition, it is considered that the magnitude relationship of the diffusion constant is the same for a semiconductor material containing at least indium, gallium, and phosphorus (see JP-A-8-102567). In other words, the Al—In—Ga— of the present invention. Also in each of the P-based semiconductor layers 107, 106, 103, 102, 101, the diffusion constant of the second dopant Zn is larger than the diffusion constant of the first dopant Be. Further, in this system, the magnitude relationship of the diffusion constants of Mg, Zn, and Be is presumed to be Mg>Zn> Be.
[0067]
Whereas the conventional semiconductor laser device is annealed at 600 ° C. for 3 hours, the window region formation of the end face window type semiconductor laser device according to the first embodiment of the present invention is performed at a low temperature of 500 ° C. for 3 hours. It could be formed by annealing. This is presumably because Zn having a large diffusion constant diffused from the surface of the cap layer into the p-clad layer, which acted to promote diffusion of the dopant Be in the p-clad layer into the active layer. . As the Be diffuses into the active layer, the band gap of the active layer increases and a window region is formed.
[0068]
In the end face window type semiconductor laser device according to the first embodiment of the present invention, since the window region can be formed by low-temperature annealing as compared with the conventional semiconductor laser device, the dopant (Be) in the p-cladding layer is formed in the active region. Diffusion to the active layer can be suppressed, an increase in operating current and operating voltage can be prevented, and a highly reliable high-power laser can be obtained.
[0069]
Further, by arranging Be having a small diffusion constant in the dopant of the p-cladding layer in the active region, it is possible to prevent the Be in the active region from diffusing into the active layer due to thermal annealing at the time of forming the window region. This is more effective for increasing the operating voltage. In the end face window type semiconductor laser device according to the first embodiment of the present invention, the Zn concentration of the p-dopant in the window region is set higher than the Be concentration of the dopant in the p-cladding layer. With this configuration, the effect of Zn diffusion promoting Be diffusion in the p-cladding layer is further increased.
[0070]
The Zn concentration in the vicinity of the cap layer in the window region of the edge window type semiconductor laser device or the p-clad layer on the cap layer side according to the first embodiment of the present invention is 1 × 10. ¹⁸ cm ^-3 1 × 10 ¹⁹ cm ^-3 It is as follows. Zn concentration is 1 × 10 ¹⁸ cm ^-3 If it is smaller than 1, the effect of promoting Be diffusion of the p-cladding layer becomes small.
[0071]
The Zn concentration is 1 × 10 ¹⁹ cm ^-3 Is larger than that, a large amount of Zn diffuses in the p-cladding layer near the p-cap layer to generate carriers. Therefore, the free carrier absorption of the p-cladding layer with respect to the laser light increases. In addition, a large amount of Zn diffusion tends to cause crystal defects in the p-cladding layer, which causes absorption of laser light.
[0072]
In addition, the Be concentration in the p-cladding layer is usually 1 to 3 × 10 6 in order to reduce device resistance and reduce free carrier absorption. ¹⁸ cm ^-3 Set to degree. Accordingly, the Zn concentration near the cap layer side is 1 × 10 5. ¹⁸ cm ^-3 If the above is set, the Zn concentration becomes equal to or higher than the Be concentration, so that Zn easily diffuses into the p-cladding layer, which causes the diffusion of Be in the p-cladding layer into the active layer. And can increase the band gap of the active layer in the window region.
[0073]
Further, the Be concentration in the vicinity of the active layer of the p-cladding layer of the semiconductor laser device of the present invention is about 5 × 10 5. ¹⁷ cm ^-3 3 × 10 ¹⁸ cm ^-3 It is as follows. Be concentration is ~ 5x10 ¹⁷ cm ^-3 If it becomes smaller than this, the diffusion of Be into the active layer in the window region is reduced, and the effect of increasing the band gap of the active layer in the window region is reduced. Be concentration is 3 × 10 ¹⁸ cm ^-3 Is larger, Be diffusion to the active layer in the active region increases, and the operating current and operating voltage increase.
[0074]
The length of the current blocking layer above the window region is preferably set to be longer than the window region so as to cover the window region. In the window region, the second dopant is diffused from the p-cap layer to the p-cladding layer to form a mixed region with the first dopant. By making the length of the current blocking layer longer than the length of the window region, it is possible to suppress a current from flowing through the mixed region. When a current is passed through the mixed region, diffusion is further promoted during the operation of the device, resulting in a change in device characteristics. Therefore, it is desirable to optimize the length of the current blocking layer for stable operation.
[0075]
Further, the material system of the end face window type semiconductor laser device according to the embodiment of the present invention contains at least In, Ga, and P. In this case, in the thermal annealing at the time of forming the window region, the diffusion of the second dopant particularly effectively acts on the increase in the diffusion of the first dopant, which is suitable for the desired window region formation.
[0076]
[Second Embodiment]
FIG. 6 is a perspective view of the structure of the end face window type semiconductor laser device according to the second embodiment of the present invention, FIG. 7 is a sectional view taken along the line CC ′ of FIG. 6, and FIG. This is illustrated in FIG. 8 and described. 7 is a cross-sectional view in the direction parallel to the longitudinal direction of the ridge stripe at the center of the ridge stripe, and FIG. 8 is a cross-sectional view in the direction perpendicular to the longitudinal direction of the ridge stripe at the center of the resonator. It is.
[0077]
In the edge window type semiconductor laser device according to the first embodiment, Be is selected as the first dopant having a small diffusion constant, and Zn is selected as the second dopant having a large diffusion constant. However, the edge window according to the second embodiment of the present invention The main difference in the type semiconductor laser device is that Be is selected as the first dopant having a small diffusion constant and Mg is selected as the second dopant having a large diffusion constant. Description will be made by paying attention to this difference.
[0078]
In FIG. 6, n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first lower cladding layer 201 (thickness 2 μm, carrier concentration 1.0 × 10 ¹⁸ cm ^-3 , Dopant Si), non-doped multiple quantum well active layer 202, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first upper cladding layer 203 (thickness 0.2 μm, carrier concentration 1.0 × 10 ¹⁸ cm ^-3 , Dopant Be), p-In _0.5 Ga _0.5 P etching stop layer 204 (thickness 50 mm, carrier concentration 1.0 × 10 ¹⁸ cm ^-3 , Dopant Be). The ridge stripe 205 (width 2.5 μm) is p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second upper cladding layer 206 (thickness 1.2 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be) and p-GaAs cap layer 207 (thickness 0.3 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be).
[0079]
Here, the non-doped multiple quantum well active layer 202 is composed of two In layers. _0.5 Ga _0.5 P well layer (thickness 80 mm) and one layer (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer (thickness 50mm) and sandwich them (Al _0.5 Ga _0.5 ) _0.5 In _0.5 It is composed of a P guide layer (thickness 300 mm).
[0080]
At and near the light emitting end face, the band gap of the active layer is larger than the band gap of the active layer inside the resonator. The side surface of the ridge stripe 205 is n-Al _0.5 In _0.5 P current blocking layer 208 (thickness 1.2 μm, carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Si), and has a current blocking layer 208 on the ridge stripe at and near the light emitting end face, and no current blocking layer is formed on the ridge stripe inside the resonator. A p-GaAs contact layer 209 (thickness 3 μm, carrier concentration 2 × 10 6) is formed on the ridge stripe and the current blocking layer. ¹⁸ cm ^-3 , Dopant Be) is formed. The length of the resonator of the semiconductor laser device of the present invention is 600 μm.
[0081]
Electrodes 210 and 211 are formed on the substrate side surface and the growth layer side surface. Here, a region having a large active layer band gap near the end surface is defined as a window region 221, and a region having a small active layer band cap inside the resonator is defined as an active region 222.
[0082]
As described in the active region 122, the window region 121 of the edge window type semiconductor laser device according to the first embodiment of the present invention, and the small region of the active layer band cap inside the resonator are described as the active region 122, the first lower cladding. The layer 201, the first upper cladding layer 203, and the like are provided with reference numerals corresponding to the window region 221 and the active region 222.
[0083]
The active layer 202 includes an active layer (202W) in the window region 221, an active layer (202A) in the active region 222, and an active layer (202W) in the window region 221.
[0084]
The first lower cladding layer 201 adjacent to the active layer 202 includes a first lower cladding layer (201 W) in the window region 221, a first lower cladding layer (201 A) in the active region 222, and a first lower cladding in the window region 221. Layer (201W).
[0085]
The first upper cladding layer 203 adjacent to the active layer 202 includes a first upper cladding layer (203W) in the window region 221, a first upper cladding layer (203A) in the active region 222, and a first upper cladding layer (in the window region 221). 203W).
[0086]
As shown in FIG. 7, a current blocking layer 208 is formed on the window region 221 so as to cover the window region. As shown in FIG. 8, no current blocking layer is formed on the ridge stripe in the active region inside the resonator.
[0087]
Next, a method for manufacturing an end face window type semiconductor laser device according to the second embodiment of the present invention will be described with reference to FIG. FIG. 9A shows the process from the n-GaAs substrate to the p-cap layer, and FIG. ₂ FIG. 9C shows a process for forming a window region and an active region, and FIG. 9D shows a process for forming a ridge stripe.
[0088]
In FIG. 9A, n- (Al is formed on an n-GaAs substrate 200 by molecular beam epitaxy (MBE). _0.7 Ga _0.3 ) _0.5 In _0.5 P first lower cladding layer 201 (carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Si), (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P guide layer and two layers of In _0.5 Ga _0.5 P well layer and one layer (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer and (Al _0.5 Ga _0.5 ) _0.5 In _0.5 Non-doped multiple quantum well active layer 202 composed of a P guide layer, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first upper cladding layer 203 (carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Be), p-In _0.5 Ga _0.5 P etch stop layer 204 (carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Be), p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second upper cladding layer 206 (carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Be) and p-GaAs cap layer 207 (thickness 0.3 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 The dopant Be) is grown.
[0089]
In FIG. 9B, SiO ₂ A mask 231 is deposited on the surface of the p-cap layer 207, and a SiO2 mask 231 having a period of 600 μm and a length of 560 μm is formed by photolithography and lift-off.
[0090]
Next, in FIG. 9C, SiO 2 is formed by metal organic vapor phase epitaxy (MOCVD) or liquid phase epitaxy (LPE). ₂ In addition to the mask, a selectively high-concentration p-GaAs diffusion layer 232 (thickness 2 μm, carrier concentration 5 × 10 ¹⁸ cm ^-3 , Dopant Mg or Zn).
[0091]
In FIG. 9D, annealing is performed at 500 ° C. for 2.5 hours, Mg is diffused immediately below the GaAs diffusion layer 232, and the diffusion leads to the quantum well active layer 202 of the dopant Be of the p-cladding layers 203 and 206. Is diffused to form a band gap increasing region of the active layer, that is, a window region 221. At the same time, the portion without the GaAs diffusion layer 232 becomes the active region 222. Finally, GaAs diffusion layer, SiO ₂ The mask is removed, and a ridge stripe 205 is formed by photolithography and etching.
[0092]
N-Al on the side of the ridge stripe and on the top of the ridge stripe in the window region _0.5 In _0.5 The P current blocking layer 208 is buried and grown by the second MBE method, and the p-GaAs contact layer 209 (thickness 3 μm) is grown by the third MBE method on the upper part thereof, and the substrate side and the contact layer surface are grown. An electrode is formed on the substrate (here, details of these manufacturing methods are not shown).
[0093]
Cleaving is performed on the surface orthogonal to the ridge stripe so that the window region becomes the end face of the resonator, and the light emitting side end face is coated with a reflectance of 8% and the back face is coated with 95%. Here, the resonator length is 600 μm, and the length of the window region is 20 μm.
[0094]
By applying a voltage to the electrodes 210 and 211 of the semiconductor laser element of the present invention and injecting a current into the ridge stripe of the active region 222 and the corresponding active layer, laser oscillation light can be obtained from the light emitting end face. A maximum light output of 300 mW is obtained at a wavelength of 650 nm, and end face deterioration is suppressed by the window effect. Furthermore, high reliability exceeding 5000 h was obtained at an operating temperature of 60 ° C. and a high output of continuous oscillation of 85 mW.
[0095]
Whereas the oscillation threshold current of the conventional semiconductor laser element is 53 mA, the oscillation threshold current of the semiconductor laser element of the present invention can be reduced to 35 mA. Also, the operating voltage of the semiconductor laser device of the present invention can be reduced to 2.2V, while the operating voltage of the conventional semiconductor laser device with an optical output of 50 mW is 2.5V. Due to the current reduction and voltage reduction, the semiconductor laser device of the present invention can achieve high reliability and higher output than the conventional semiconductor laser device.
[0096]
FIG. 10 shows the concentration distribution of p-impurities (Mg, Be) from the surface of the p-cap layer 207 to the n-cladding layer 201 of the semiconductor laser device of the present invention. FIG. 10A shows the concentration distribution of the window region, and FIG. 10B shows the concentration distribution of the active region.
[0097]
In the window region, Mg diffuses from the cap layer surface into the p-cladding layer. On the other hand, Be in the p-cladding layer diffuses in a large amount not only in the active layer but also in the middle of the n-cladding layer. This Be diffusion increases the band gap of the active layer in the window region. On the other hand, in the active region, Be in the p-cladding layer hardly diffuses into the active layer in the active region.
[0098]
In the window region of the end face window type semiconductor laser device according to the second embodiment of the present invention, p-dopant Mg (second dopant) and p-cladding layer Dopan Be (first dopant) are mixed. . In the active region, the p-cladding layer dopant Be is present. Here, the diffusion constant of the dopant is larger in Mg than in Be.
[0099]
In the semiconductor laser device of the present invention, the window region was formed by annealing at a lower temperature and in a shorter time than the conventional semiconductor laser device. Mg having a large diffusion constant diffused from the cap layer surface into the p-cladding layer. Is presumed to act to promote diffusion of dopant Be in the p-cladding layer into the active layer. As the Be diffuses into the active layer, the band gap of the active layer in the window region increases, and a window region is formed.
[0100]
In the edge window type semiconductor laser device according to the second embodiment of the present invention, diffusion of the dopant (Be) in the p-cladding layer into the active layer can be suppressed in the active region, and an increase in current and voltage can be prevented. A highly reliable high-power laser can be obtained.
[0101]
Furthermore, by arranging Be having a small diffusion constant in the dopant of the p-cladding layer in the active region, it is possible to further prevent the Be in the active region from diffusing into the active layer by thermal annealing at the time of forming the window region. It is effective against increase.
[0102]
In the end face window type semiconductor laser device according to the first and second embodiments of the present invention, a p-GaAs diffusion layer (ZnO) is used. _X Stripe 131, SiO ₂ The same effect was obtained when the dopant of the cap 132 or the like was Mg or Zn. In particular, when the dopant is Mg, the window region can be formed by annealing at a lower temperature for a shorter time. This is presumably because Mg has a greater effect of promoting diffusion of Be in the p-cladding layer into the active layer than Zn.
[0103]
[Third Embodiment]
FIG. 11 is a perspective view of an element structure of an end face window type semiconductor laser according to the third embodiment of the present invention. 12 is a cross-sectional view in the direction parallel to the ridge stripe at the center of the ridge stripe as indicated by EE ′ in FIG. 11, and FIG. 13 is a ridge at the center of the resonator as indicated by FF ′ in FIG. It is sectional drawing of a perpendicular direction to a stripe.
[0104]
The main difference between the end face window type semiconductor laser devices relating to the first to third embodiments of the present invention is that in the first embodiment, Be is a first dopant having a small diffusion constant, and a second is a large diffusion constant. In the second embodiment, Zn is selected as the dopant. In the second embodiment, Be is selected as the first dopant, and Mg is selected as the second dopant. In the third embodiment, the first dopant is Zn, This is that Mg is selected as the second dopant. In FIG. 11, n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first lower cladding layer 301 (thickness 2 μm, carrier concentration 1.0 × 10 ¹⁸ cm ^-3 , Dopant Si), two layers of In _0.5 Ga _0.5 P well layer (thickness 80 mm) and one layer (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer (thickness 50mm) and sandwich them (Al _0.5 Ga _0.5 ) _0.5 In _0.5 Non-doped multiple quantum well active layer 302 composed of a P guide layer (thickness 300 mm), p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first upper cladding layer 303 (thickness 0.2 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Zn), p-In _0.5 Ga _0.5 P etching stop layer 304 (thickness 50 mm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Zn). The ridge stripe 305 (width 2.5 μm) is p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second upper cladding layer 306 (thickness 1.2 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Zn) and p-GaAs cap layer 307 (thickness 0.3 μm, carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Mg). At and near the light emitting end face, the band gap of the active layer is larger than the band gap of the active layer inside the resonator. The side surface of the ridge stripe 305 is n-Al _0.5 In _0.5 P current blocking layer 208 (thickness 1.2 μm, carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Si), and has a current blocking layer 308 above the ridge stripe at and near the light emitting end face, and no current blocking layer is formed above the ridge stripe inside the resonator. A p-GaAs contact layer 309 (thickness 3 μm, carrier concentration 2 × 10 10) is formed on the ridge stripe and the current blocking layer. ¹⁸ cm ^-3 , Dopant Zn). The length of the resonator of the semiconductor laser device of the present invention is 600 μm. Electrodes 310 and 311 are formed on the substrate side surface and the growth layer side surface. Here, a region having a large active layer band gap near the end face is defined as a window region 321, and a region having a small active layer band cap inside the resonator is defined as an active region 322.
[0105]
As shown in FIG. 12, a current blocking layer 308 is formed on the window region 321 so as to cover the window region. As shown in FIG. 13, the current blocking layer is not formed on the ridge stripe in the active region inside the resonator.
[0106]
FIG. 14 shows a manufacturing method of an end face window type semiconductor laser device according to the third embodiment of the present invention, which will be described.
[0107]
Next, referring to FIG. 14A, a method for manufacturing the semiconductor laser device of the present invention will be described. FIG. 14 shows an element manufacturing method. On the n-GaAs substrate 300, by metal organic chemical vapor deposition (MOCVD), n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first lower cladding layer 301 (carrier concentration 1 × 10 ¹⁸ cm ^-3 , Dopant Si), (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P guide layer and two layers of In _0.5 Ga _0.5 P well layer and one layer (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer and (Al _0.5 Ga _0.5 ) _0.5 In _0.5 Non-doped multiple quantum well active layer 302 composed of a P guide layer, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first upper cladding layer 303 (carrier concentration 1.5 × 10 18 cm −3, dopant Zn), p-In _0.5 Ga _0.5 P etching stop layer 304 (carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Zn), p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second upper cladding layer 306 (carrier concentration 1.5 × 10 ¹⁸ cm ^-3 , Dopant Zn) and high-concentration p-GaAs cap layer 307 (thickness 3 μm, carrier concentration 6 × 10 ¹⁸ cm ^-3 , Dopant Mg).
[0108]
In FIG. 14B, SiO ₂ A mask 331 is vapor-deposited on the surface of the p-cap layer 307, and a SiOμ having a period of 600 μm and a length of 60 μm is formed by photolithography and lift-off. ₂ A mask 331 is formed, and the thickness of the p-cap layer other than the mask is reduced to 0.2 μm by etching.
[0109]
In FIG. 14C, annealing is performed at 600 ° C. for 2 hours to diffuse Mg in the thick part of the p-cap layer, and the diffusion causes the dopant Zn to the quantum well active layer 202 of the p-cladding layers 303 and 306. The band gap increasing region of the active layer, that is, the window region 321 is formed. At the same time, the thin portion of the p-cap layer has less Mg diffusion, and therefore the diffusion of Zn in the p-cladding layer to the active layer is also reduced, and the active layer 322 has an almost unchanged band gap.
[0110]
In FIG. 14 (d), SiO ₂ The mask 331 is removed, the thickness of the p-cap layer 307 is adjusted, and the ridge stripe 305 is formed by photolithography and etching.
[0111]
N-Al on the side of the ridge stripe and on the top of the ridge stripe in the window region _0.5 In _0.5 The P current blocking layer 308 is buried and grown by the second MOCVD method, and the p-GaAs contact layer 309 (thickness 3 μm) is grown by the third MOCVD method on the upper part thereof, and the substrate side and the contact layer surface are grown. An electrode is formed on the substrate. (The details of these manufacturing methods are not shown here.) Cleaving is performed on a plane orthogonal to the ridge stripe so that the window region becomes the end face of the resonator, and the light emitting side end face is coated with a coating with a reflectance of 8%. 95% coating on the back side. Here, the resonator length is 600 μm, and the length of the window region is 20 μm.
[0112]
Light is emitted by applying a voltage to the electrodes 310 and 311 of the edge window type semiconductor laser device according to the third embodiment of the present invention and injecting current into the ridge stripe in the active region and the corresponding active layer. Laser oscillation light can be obtained from the end face. A maximum light output of 300 mW is obtained at a wavelength of 650 nm, and end face deterioration is suppressed by the window effect. Furthermore, high reliability exceeding 5000 h was obtained at an operating temperature of 60 ° C. and a high output of 75 mW continuous oscillation.
[0113]
Whereas the oscillation threshold current of the conventional semiconductor laser element is 53 mA, the oscillation threshold current of the end face window type semiconductor laser element according to the third embodiment of the present invention is about 40 mA, and the oscillation threshold current is about It was possible to reduce 13 mA. Further, the operating voltage of the conventional semiconductor laser device with an optical output of 50 mW is 2.5 V, whereas the operating voltage of the end face window type semiconductor laser device of the present invention is 2.3 V, which can be reduced to 2.3 V. It was. Due to the current reduction and voltage reduction, the end face window type semiconductor laser device of the present invention can achieve higher output and higher reliability than the conventional semiconductor laser device. FIG. 15 shows the concentration distribution of p-impurities (Mg, Zn) from the surface of the p-cap layer 307 to the n-cladding layer 301 of the edge window type semiconductor laser device according to the third embodiment of the present invention. FIG. 15A shows the concentration distribution of the window region, and FIG. 15B shows the concentration distribution of the active region. In the window region, Mg diffuses from the cap layer surface into the p-cladding layer. Zn in the p-cladding layer diffuses in a large amount not only in the active layer but also in the middle of the n-cladding layer. This Zn diffusion causes an increase in the band gap. On the other hand, in the active region, Mg in the p-cap layer is hardly diffused, and Zn in the p-cladding layer is hardly diffused in the active layer.
[0114]
This embodiment is characterized in that the window region and the active region can be formed by changing the thickness of the p-cap layer formed by the first crystal growth, which is simple in manufacturing.
[0115]
As described above, the InGaAlP-based material has been described in the present embodiment, but the same effect can be obtained in the case of an AlGaAs-based material.
[0116]
【The invention's effect】
As described above, according to the semiconductor laser device of the present invention, the resonator end face has an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type cap layer on the semiconductor substrate, and is perpendicular to each semiconductor layer. And a semiconductor laser element having a window region in which the band gap of the active layer in the vicinity of at least one end surface of the resonator is larger than the band gap of the active layer inside the resonator, and the p-type cladding layer in the window region Has a configuration in which a first dopant and a second dopant having a larger diffusion constant than the first dopant are mixed, and the first dopant is present in a higher concentration than the second dopant in the p-type cladding layer in the active region other than the window region. .
[0117]
Accordingly, when the window region is formed, the p-type dopant (second dopant) having a large diffusion constant promotes the diffusion of the p-type dopant (first dopant) having a small diffusion constant, thereby disordering the active layer. A desired window region can be formed by short-time annealing. As a result, an increase in operating current and operating voltage due to diffusion of the p-type dopant into the active layer in the active region can be prevented, and a semiconductor laser device with high output and high reliability can be obtained.
[0118]
In addition, according to the semiconductor laser device of the present invention, the second dopant concentration in the p-type cap layer in the window region is higher than the first dopant concentration. Therefore, when the window region is formed, the p-type dopant (second dopant) having a large diffusion constant promotes the diffusion of the p-type dopant (first dopant) having a small diffusion constant. A window region can be formed. As a result, an increase in operating current and operating voltage due to diffusion of the p-type dopant into the active layer in the active region can be prevented, and a semiconductor laser device with high output and high reliability can be obtained.
[0119]
In addition, according to the semiconductor laser device of the present invention, the concentration of the first dopant is preferentially present in the p-type cladding layer inside the resonator other than the window region.
[0120]
Therefore, by disposing a dopant having a small diffusion constant (first dopant) in the active region, it is possible to prevent the p-type second dopant from diffusing into the active layer in the active region by thermal annealing when forming the window region. As a result, an increase in operating current and operating voltage can be prevented, and a high output and high reliability semiconductor laser device can be obtained.
[0121]
According to the semiconductor laser device of the present invention, the second dopant is mainly disposed near the cap layer side of the p-type cladding layer in the window region, and mainly near the active layer side of the p-type cladding layer in the window region. The first dopant is arranged.
[0122]
Therefore, the second dopant having a large diffusion constant effectively promotes the diffusion of the first dopant having a small diffusion constant into the active layer in the thermal annealing at the time of forming the window region. Therefore, the annealing temperature can be further lowered, and an increase in operating current and operating voltage can be prevented. As a result, an increase in operating current and operating voltage can be prevented, and a high output and high reliability semiconductor laser device can be obtained.
[0123]
In addition, according to the semiconductor laser device of the present invention, the first dopant is hardly present in the active layer or the n-type cladding layer in the active region.
[0124]
Therefore, by suppressing the diffusion of the first dopant into the active layer or the n-type cladding layer in the active region by thermal annealing at the time of forming the window region, it is possible to prevent an increase in operating current and operating voltage, and a high output and high power. A reliable semiconductor laser element can be obtained.
[0125]
According to the semiconductor laser device of the present invention, the concentration of the second dopant in the vicinity of the cap layer side of the p-type cladding layer in the window region is 1 × 10 ¹⁸ cm ^-3 1 × 10 ¹⁹ cm ^-3 The configuration is as follows.
[0126]
Therefore, by setting the concentration of the second dopant within a predetermined range, it is possible to prevent the deterioration of characteristics due to the thermal annealing at the time of forming the window region.
[0127]
According to the semiconductor laser device of the present invention, the concentration of the first dopant in the vicinity of the active layer side of the p-type cladding layer is 5 × 10 5. ¹⁷ cm ^-3 3 × 10 ¹⁸ cm ^-3 The configuration is as follows.
[0128]
Therefore, by setting the concentration of the first dopant within a predetermined range, it is possible to prevent the deterioration of characteristics due to the thermal annealing at the time of forming the window region.
[0129]
According to the semiconductor laser device of the present invention, the combination of the first dopant and the second dopant is beryllium and zinc, beryllium and magnesium, or zinc and magnesium, respectively.
[0130]
Therefore, a combination of the first dopant and the second dopant can be selected as necessary, and a desired window region can be formed with good control.
[0131]
According to the semiconductor laser device of the present invention, the current blocking layer is provided on the ridge above the window region, and the length thereof is longer than the length of the window region.
[0132]
Therefore, it is possible to suppress the deterioration of the characteristics of the semiconductor laser device due to the current leakage to the p-type cladding layer in the window region, which is suitable for stabilizing the characteristics.
[0133]
Further, according to the semiconductor laser device of the present invention, the semiconductor constituent material includes at least indium, gallium, and phosphorus.
[0134]
Therefore, the range of selection of semiconductor constituent materials is increased, and a semiconductor laser element having a desired oscillation wavelength can be obtained.
[0135]
According to the method for manufacturing a semiconductor laser device of the present invention, a step of growing an n-type cladding layer, an active layer, a p-type cladding layer having a first dopant and a p-type cap layer on a semiconductor substrate, A step of forming a diffusion source serving as a second dopant having a diffusion constant larger than that of the first dopant only in a portion corresponding to the vicinity of the end face of the resonator, and then diffusing the second dopant into the p-type cladding layer by thermal annealing, and promoting the diffusion of the first dopant in the p-type cladding layer into the active layer to increase the band gap of the active layer more than the inside of the resonator to form a window region. The combination of the first dopant and the second dopant is beryllium and zinc, beryllium and magnesium, or zinc and magnesium, respectively. It is configured.
[0136]
Therefore, it is possible to obtain a manufacturing method excellent in controllability for obtaining a semiconductor laser device having high output and high reliability.
[0137]
[0138]
[Brief description of the drawings]
FIG. 1 is a perspective view of a semiconductor laser device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1 of the present invention, and is a cross-sectional view in a direction parallel to the longitudinal direction of the ridge stripe at the center of the ridge stripe.
3 is a cross-sectional view taken along the line BB ′ of FIG. 1 according to the present invention, and is a cross-sectional view in a direction perpendicular to the longitudinal direction of the ridge stripe at the center of the resonator.
4A and 4B are diagrams relating to a method of manufacturing a semiconductor laser device according to the first embodiment of the present invention, in which FIG. 4A is a diagram illustrating a process from an n-GaAs substrate to a p-cap layer, and FIG. _X From the formation of stripes to SiO ₂ FIG. 4C is a diagram illustrating a process until a cap is formed, FIG. 4C is a diagram illustrating a process of forming a window region and an active region, and FIG. 4D is a diagram illustrating a process of forming a ridge stripe.
FIG. 5 is a diagram showing the concentration distribution of p-type impurities (Zn, Be) from the surface of the p-cap layer 107 to the n-cladding layer 101 of the semiconductor laser device according to the first embodiment of the present invention; (a) is a diagram showing the concentration distribution of each layer in the window region 121, and (b) is a diagram showing the concentration distribution of each layer in the active region 122.
FIG. 6 is a perspective view of a semiconductor laser device according to a second embodiment of the present invention.
7 is a cross-sectional view taken along the line CC ′ of FIG. 6 of the present invention, and is a cross-sectional view in a direction parallel to the longitudinal direction of the ridge stripe at the center of the ridge stripe.
8 is a cross-sectional view taken along the line DD ′ of FIG. 6 of the present invention, and is a cross-sectional view in a direction perpendicular to the longitudinal direction of the ridge stripe at the center of the resonator.
FIGS. 9A and 9B are diagrams relating to a method of manufacturing a semiconductor laser device according to a second embodiment of the present invention, wherein FIG. 9A is a diagram showing steps from an n-GaAs substrate to a p-cap layer, and FIG. _X From the formation of stripes to SiO ₂ FIG. 4C is a diagram illustrating a process until a cap is formed, FIG. 4C is a diagram illustrating a process of forming a window region and an active region, and FIG. 4D is a diagram illustrating a process of forming a ridge stripe.
FIG. 10 is a diagram showing the concentration distribution of p-type impurities (Mg, Be) from the surface of the p-cap layer 207 to the n-cladding layer 201 of the semiconductor laser device according to the second embodiment of the present invention; (a) is a diagram showing the concentration distribution of each layer in the window region 221, and (b) is a diagram showing the concentration distribution of each layer in the active region 222.
FIG. 11 is a perspective view of a semiconductor laser device according to a third embodiment of the present invention.
12 is a cross-sectional view taken along the line CC ′ of FIG. 6 of the present invention, and is a cross-sectional view in a direction parallel to the longitudinal direction of the ridge stripe at the center of the ridge stripe.
13 is a cross-sectional view taken along the line DD ′ of FIG. 6 of the present invention, and is a cross-sectional view in a direction perpendicular to the longitudinal direction of the ridge stripe at the center of the resonator.
14A and 14B are diagrams relating to a method of manufacturing a semiconductor laser device according to a third embodiment of the present invention, in which FIG. 14A is a diagram showing steps from an n-GaAs substrate to a p-cap layer, and FIG. _X From the formation of stripes to SiO ₂ FIG. 4C is a diagram illustrating a process until a cap is formed, FIG. 4C is a diagram illustrating a process of forming a window region and an active region, and FIG. 4D is a diagram illustrating a process of forming a ridge stripe.
FIG. 15 is a diagram showing the concentration distribution of p-type impurities (Mg, Zn) from the surface of the p-cap layer 307 to the n-cladding layer 301 of the semiconductor laser device according to the third embodiment of the present invention; (a) is a diagram showing the concentration distribution of each layer in the window region 321, and (b) is a diagram showing the concentration distribution of each layer in the active region 322.
FIG. 16 is a perspective view of a conventional semiconductor laser device.
FIG. 17 is a cross-sectional view taken along the line GG ′ of FIG. 16 of the conventional example.
18 is a diagram showing the concentration distribution of p-type impurity (Zn) on the surface of the p-upper cladding layer 6 inside the ridge stripe 7 or the n-cladding layer 2 in the ridge stripe 7 of the conventional semiconductor laser device. It is a figure which shows concentration distribution of Zn of a window area | region, (b) is a figure which shows concentration distribution of Zn of an active region.
[Explanation of symbols]
100, 200, 300 n-GaAs substrate
101, 201, 301 n-first lower cladding layer
101A, 201A, 301A n-first lower cladding layer in the active region
101W, 201W, 301W n-first lower cladding layer in window region
102, 202, 302 Quantum well active layer (active layer)
102A, 202A, 302A Quantum well active layer (active layer) in active region
102W, 202W, 302W Quantum well active layer (active layer) in window region
103, 203, 303 p-first upper cladding layer
103A, 203A, 303A p-first upper cladding layer in the active region
103W, 203W, 303W p-first upper cladding layer in window region
104, 204, 304 p-etch stop layer
105, 205, 305 Ridge stripe
105A, 205A, 305A Ridge stripe in active region
105W, 205W, 305W Ridge stripe in window area
106, 206, 306 p-second upper cladding layer
106A, 206A, 306A p-second upper cladding layer in the active region
106W, 206W, 306W p-second upper cladding layer in window region
107, 207, 307 p-cap layer
107A, 207A, 307A p-cap layer in active region
107W, 207W, 307W p-cap layer in window region
108, 208, 308 n-current blocking layer
109, 209, 309 p-contact layer
110, 210, 310 n-electrode
111, 211, 311 p-electrode
121, 221 and 321 Window area
122, 222, 322 active region
131 ZnO stripe
132 SiO ₂ cap
231 and 331 SiO ₂ mask
232 diffusion layer

Claims (6)

The semiconductor substrate has an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type cap layer, and has a resonator end face perpendicular to each semiconductor layer, and is located in the vicinity of at least one end face of the resonator end face. In the semiconductor laser device having a window region in which the band gap of the active layer is larger than the band gap of the active layer inside the resonator,
In the p-type cladding layer of the window region, a first dopant and a second dopant having a diffusion constant larger than that of the first dopant are mixed,
The first dopant is present in a higher concentration than the second dopant in the p-type cladding layer in the active region other than the window region ,
A combination of the first dopant and the second dopant is beryllium and zinc, beryllium and magnesium, or zinc and magnesium, respectively;
A semiconductor laser device comprising a current blocking layer on a ridge above the window region, the length of which is longer than the length of the window region . The semiconductor laser device according to claim 1,
Wherein in the vicinity of the cap layer side of the p-type cladding layer window area is disposed mainly second dopant DOO, primarily the first dopant is provided in the vicinity of the active layer side of the p-type cladding layer of said window region A semiconductor laser device characterized by the above. The semiconductor laser device according to claim 2, wherein
Wherein the concentration of the second dopant than 1 × 10 ¹⁸ cm ^-3 in the cap layer side near the window area p-type cladding layer, 1 × 10 ¹⁹ cm ^-3 semiconductor laser device characterized der Rukoto below. The semiconductor laser device according to claim 2, wherein
concentration of the first dopant definitive near the active layer side of the p-type cladding layer is 5 × 10 ¹⁷ cm ^-3 or more, 3 × 10 ¹⁸ cm ^-3 semiconductor laser device characterized der Rukoto below. The semiconductor laser device according to claim 1,
A semiconductor laser element , wherein the semiconductor material contains at least indium, gallium, and phosphorus . On a semi-conductor substrate, n-type cladding layer, active layer, growing a p-type cladding layer and the p-type cap layer having a first dopant, only a portion corresponding to the vicinity of the cavity end face thereon, a first dopant Forming a diffusion source serving as a second dopant having a larger diffusion constant than the second dopant, and then diffusing the second dopant into the p-type cladding layer by thermal annealing so that the first dopant in the p-type cladding layer is applied to the active layer. Facilitating diffusion to increase the band gap of the active layer more than inside the resonator to form a window region, and
A method of manufacturing a semiconductor laser device , wherein the combination of the first dopant and the second dopant is beryllium and zinc, beryllium and magnesium, or zinc and magnesium, respectively .

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