JP3903229B2 - 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 a manufacturing method thereof, and more particularly, to a lateral mode control type semiconductor laser device using a stepped substrate that oscillates in a short wavelength in a red region and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, visible light semiconductor lasers in the 0.6 μm band have been used in high-density optical disk devices such as DVDs because the laser spot can be narrowed down.
[0003]
Such a device will use a battery of a notebook personal computer or the like and will be incorporated in a narrow space in the future. Therefore, as a specification required for parts, low power consumption has become a problem.
[0004]
When manufacturing such a visible light semiconductor laser, since AlInP or AlGaInP is a material system having the largest band gap as a III-V group compound semiconductor lattice-matched with GaAs, AlInP or AlGaInP is used as a cladding layer. It is useful to use, in particular, an essential material for red lasers.
[0005]
As a AlGaInP-based visible light semiconductor laser that does not use a buried structure, the present inventors have developed a single-growth semiconductor laser device in which a double heterojunction structure is grown on a stepped substrate, that is, a slope oscillation type semiconductor laser. Since it has been proposed (JP-A-6-45708), this single growth type semiconductor laser device will be described with reference to FIG.
[0006]
The basic structure of the optical waveguide of this single-growth semiconductor laser device is known as a TS (Terraced Substrate) laser, and a step is also formed in the active layer by the step provided on the substrate, so that lateral mode control is performed. Is possible.
[0007]
See Fig. 3 (a)
FIG. 3A is a perspective view of a single-growth type semiconductor laser device. After a step is formed on an n-type GaAs substrate 31 whose main surface is a (100) plane and whose inclined surface is substantially the (311) A plane, The n-type GaAs buffer layer 32, the n-type GaInP intermediate layer 33, the n-type AlGaInP clad layer 34, the MQW (multiple quantum well) active layer 35, the p-type AlGaInP are formed on the top by using the MOVPE method (metal organic vapor phase epitaxy). A clad layer 36, a second clad layer whose peripheral part is an n-type AlGaInP current confinement layer 37 and whose central part is a p-type AlGaInP layer 38, a p-type AlGaInP clad layer 39, a p-type GaInP intermediate layer 40, and a p-type GaAs contact Layer 41 is grown sequentially.
The (311) plane A is a (311) plane in which a group III element (in this case, Ga) appears on the surface.
[0008]
In this case, in the growth process of the second cladding layer in which the peripheral portion is the n-type AlGaInP current confinement layer 37 and the central portion is the p-type AlGaInP layer 38, a single crystal is used by utilizing the crystal plane orientation dependence of impurity doping. Since the current confinement mechanism is formed in the growth process, this situation will be described with reference to FIG.
[0009]
Refer to FIG.
FIG. 3 (b) shows Al and Zn doped simultaneously with Se. _0.35 Ga _0.15 In _0.5 Al when P layer is grown _0.35 Ga _0.15 In _0.5 It is a figure which shows the plane orientation dependence of the carrier density | concentration in P layer, and the horizontal axis represents the off angle from the (100) plane to the (111) A plane direction.
[0010]
In the figure, as represented by white circles and black circles, the carrier concentration is the lowest in the vicinity of the (711) A plane. Therefore, when the same amount of impurities is doped, the n-type in the (n11) A plane where n> 7. A layer is obtained, and a p-type layer is obtained on the (m11) A plane where m ≦ 7, and Al is grown along the slope of the n-type GaAs substrate 31, ie, along the (311) A plane. _0.35 Ga _0.15 In _0.5 The P layer is substantially a (411) A plane and becomes a p-type layer, but the flat surface of the n-type GaAs substrate 31, that is, the portion grown along the (100) plane is the (100) plane, so the n-type. Become a layer.
Since the values of n and m depend on the impurity doping amount, doping ratio, etc., there is no particular critical meaning.
[0011]
Thus, since the conventional slope oscillation type semiconductor laser forms the current confinement mechanism by utilizing the plane orientation dependence of the impurity doping in the MOVPE method, it is possible to perform a single continuous operation without using a buried structure or diffusion. The entire laminated structure can be obtained by the growth process, and therefore can be manufactured at a high yield and at a low price.
[0012]
In addition, since this slope oscillation type semiconductor laser does not have a loss guide structure, that is, a complex refractive index waveguide structure due to light absorption loss, it is not necessary to consider light absorption loss, so it has high efficiency and low power consumption. There is an advantage that low astigmatism characteristics can be obtained.
[0013]
Next, the plane orientation dependence of this impurity doping will be described in detail with reference to FIG.
See Fig. 4 (a)
FIG. 4A is a diagram showing the plane orientation dependency of doping of Zn and Mg, which are p-type impurities, and the off angles from the (100) plane to the (111) A plane direction and the (111) B plane direction. 2 shows the relative incorporation rate of impurities in an AlGaInP layer when an AlGaInP layer is grown from a growth gas containing Zn and Mg on a substrate having GaN.
[0014]
Black circles and black squares indicate relative carrier concentrations measured by CV measurement (capacitance measurement), and white circles and white squares indicate relative impurity concentrations measured by SIMS (Secondary Ion Mass Spectroscopy). In addition, the activation rate of the impurities can be understood from these differences, and the difference in impurity concentration depending on the crystal plane orientation, that is, the dependence of the relative impurity uptake rate on the plane orientation can be understood.
The circle indicates the A direction, and the square indicates the B direction.
[0015]
As is apparent from the figure, in the case of Zn, as the off angle increases in the A direction, that is, as n in (n11) decreases, the impurity concentration and the carrier concentration increase, and the off angle is Although it becomes maximum at 25 °, that is, in the vicinity of the (311) plane and then decreases, the (111) A plane also has a concentration about six times that of the (100) plane.
[0016]
In this case, since there is almost no difference between the impurity concentration and the carrier concentration, that is, the surface activation dependency of the impurity activation rate is not seen, this result shows the surface orientation dependency of the impurity incorporation rate. Will be.
[0017]
On the other hand, in the B direction, the plane orientation dependence of the impurity incorporation rate is not so much seen, and the (111) B plane is half of the (100) plane.
In the case of Mg, a tendency similar to that of Zn is observed, but the surface orientation dependency is smaller than that of Zn.
[0018]
Next, the plane orientation dependency of doping of Se, which is an n-type impurity, will be described with reference to FIG.
Refer to FIG.
As for Se, a tendency opposite to that of the p-type impurity is observed. As the off-angle increases in the A direction, the rate of impurity incorporation decreases, while as the off-angle increases in the B direction. Impurity incorporation rate increases.
[0019]
Therefore, a p-type region and an n-type region can be grown simultaneously by simultaneously doping a semiconductor surface having different plane orientations with a p-type impurity made of Zn or Mg and an n-type impurity made of Se. The result of FIG. 3B can be described.
[0020]
Next, referring to FIG. 5, a conventional heterojunction current confining type semiconductor that conducts current confinement using a discontinuity of an energy band formed at the heterojunction interface due to a difference in electron affinity χ, that is, a spike. The laser device (if necessary, see Ishikawa, et al., Japan Society of Applied Physics 63 Spring Proceedings 31a-ZP-8) will be described.
[0021]
Refer to FIG.
First, an n-type AlGaInP clad layer 52, a GaInP active layer 53, a p-type AlGaInP clad layer 54, and a GaInP spike prevention layer 55 are grown on an n-type GaAs substrate 51 by MOVPE, and then are convex by etching. Next, the p-type GaAs contact layer 56 is grown again by the MOVPE method.
[0022]
Refer to FIG.
FIG. 5B shows the structure of the band edge of the valence band in the one-dot chain lines A and B in FIG. 5A, and the current confinement mechanism is in the peripheral part of the ridge, that is, in the part of the one-dot chain line A. A large spike is formed at the heterojunction interface between the p-type AlGaInP cladding layer 54 and the p-type GaAs contact layer 56 due to the difference in electron affinity χ between the two, and a depletion layer in which carriers are depleted is formed in this portion. At the same time, this spike becomes a barrier against holes, making it difficult for current to flow.
[0023]
On the other hand, since the p-type GaInP spike prevention layer 55 is inserted between the p-type AlGaInP clad layer 54 and the p-type GaAs contact layer 56 in the central portion of the ridge, that is, the portion of the alternate long and short dash line B, a large spike Two small spikes are formed without forming.
[0024]
Such a low energy barrier makes it possible for the number of holes that can be overcome at room temperature to increase considerably, and also allows passage of tunnel current, so that the hole current can easily flow, and the central part of the ridge Current constriction is performed so that current flows.
[0025]
In this case, a loss guide type in which a part of the laser beam is absorbed by the p-type GaAs contact layer 56 is disadvantageous in that the efficiency is low and the threshold current is high, but the stripe width, that is, the ridge width is compared. Therefore, there is an advantage that the light density at the exit end face can be reduced and the output can be easily increased.
[0026]
Next, a conventional ridge type semiconductor laser device will be described with reference to FIG.
See FIG.
First, an n-type GaAs buffer layer 62, an n-type AlGaInP cladding layer 63, a strained MQW active layer 64, a p-type AlGaInP cladding layer 65, a p-type GaInP etching stop layer 66, p on the n-type GaAs substrate 61 by the MOVPE method. After the type AlGaInP cladding layer 67 and the p-type GaInP intermediate layer 68 are grown, a convex ridge is formed by etching, and then an n-type GaAs current confinement layer 69 and a p-type GaAs contact layer 70 are grown.
[0027]
In this case, the strained MQW active layer 64 is made of Al having a thickness of 100 mm. _0.2 Ga _0.3 In _0.5 P guide layer / 60 Å thick GaInP well layer / 40 Å thick Al _0.2 Ga _0.3 In _0.5 P barrier layer / 60 Å thick GaInP well layer / 40 Å thick Al _0.2 Ga _0.3 In _0.5 P barrier layer / 60 Å thick GaInP well layer / 100 Å thick Al _0.2 Ga _0.3 In _0.5 It is composed of a P guide layer.
[0028]
In this case, the current confinement mechanism is formed by the n-type GaAs current confinement layer 69, and the effective current 71 flows through the center of the ridge and emits the laser beam 73, but part of the injected current is the p-type AlGaInP cladding layer 65. , It spreads in the horizontal direction and flows as a reactive current 72 that does not contribute to laser oscillation.
[0029]
[Problems to be solved by the invention]
In order to reduce the power consumption of the laser, it is necessary to reduce the above-mentioned reactive current as much as possible. For this purpose, in the conventional slope oscillation type semiconductor laser of FIG. The thickness of the p-type AlGaInP clad layer 36 immediately below the layer 37, and the thickness of the p-type AlGaInP clad layer 65 directly below the n-type GaAs current confinement layer 69 in the conventional ridge type semiconductor laser device of FIG. However, there is a problem that the current confinement function itself is lost because the depletion layer extending from the pn junction causes punch-through.
[0030]
In the case of the heterojunction current confined semiconductor laser device of FIG. 5A, there is no problem of punch-through, but the manufacturing process is complicated because an etching process is required, and a semiconductor layer containing Al is formed. After processing, a semiconductor layer containing Al must be regrown, but when a semiconductor layer containing Al is processed, a natural oxide film is formed on the surface of the semiconductor layer. There is a problem that it will be very difficult to regrow itself.
[0031]
Therefore, an object of the present invention is to reduce reactive current without reducing the thickness of the p-side cladding layer immediately below the n-type current confinement layer.
[0032]
[Means for Solving the Problems]
FIG. 1 is an explanatory diagram of the principle configuration of the present invention. Means for solving the problems in the present invention will be described with reference to FIG.
See Figure 1
(1) The present invention provides a p-side cladding layer in a semiconductor laser device Prohibited A first p-type cladding layer 4 having a large band gap and a second p-type cladding layer 5 having a small band gap are formed. , P The plane orientation of the first region 9 where the hole concentration of the cladding layer 4 is high is different from the plane orientation of the second region 10 where the hole concentration is low. Thus, the first p-type cladding layer 4 is in contact with the active layer 3, and the second p-type cladding layer 5 is in contact with the n-type current confinement layer 6 in the second region 10. It is characterized by that.
[0033]
In this way, by forming the p-side cladding layer by the first p-type cladding layer 4 and the second p-type cladding layer 5 having different forbidden band widths, an energy barrier against holes, that is, The thickness of the spike can be controlled by forming the spike and setting the hole concentration in the first region 9 and the second region 10 to be different, and blocking the hole in the thick spike In addition, by tunneling holes in a thin spike, current confinement can be performed without using a pn junction, and reactive current in the peripheral portion can be reduced.
[0034]
(2) Further, in the above (1), the present invention is that the surface orientation of the second region 10 is either the (100) plane or the (m11) A plane when m is a real number. The plane orientation of the first region 9 is (m′11) A plane, where m ′ is a real number of m ′ <m.
[0035]
In this way, in the case of a normal p-type impurity, the impurity concentration and the carrier concentration increase as the off angle increases in the A direction, that is, as m decreases, so m ′ <m. Thus, the hole concentration in the first region 9 can be made higher than the hole concentration in the second region 10, thereby reducing the thickness of the spike formed in the first region 9 and tunneling. Current can flow.
The (100) plane corresponds to a plane in which m of the (m11) A plane is infinite.
[0036]
(3) In the present invention, when n is a real number of n> 7, n ′ is a real number of 2 ≦ n ′ ≦ 7, and n ″ is a real number of 3 ≦ n ″ ≦ 7, the (100) plane Alternatively, in the semiconductor laser device using the stepped substrate 1 having either the (n11) A plane as a main surface and the (n′11) A plane as an inclined surface, either the (100) plane or the (n11) A plane is An active layer 3 having a main surface and an (n ″ 11) A plane as an inclined surface is provided, and the hole concentration in the region along the inclined surface is higher than the hole concentration in the region along the main surface on the active layer 3. A side cladding layer and a cladding layer that becomes the n-type current confinement layer 6 on the main surface and becomes the p-type layer 7 on the inclined surface are provided, and the p-side cladding layer has a large forbidden band width at least on the side close to the active layer 3. The p-type cladding layer 4 and the second p-type cladding layer 5 having a small forbidden band width are used. To.
[0037]
As described above, the surface orientation of the stepped substrate 1 is selected as described above, and the first p-type cladding layer 4 and the second p-type cladding layer 5 having different forbidden band widths are used to form a p-side cladding layer. By configuring, a current confinement mechanism using spikes can be configured in the p-side cladding layer, and a current confinement mechanism using the n-type current confinement layer 6 can also be configured.
[0038]
(4) Further, according to the present invention, in any one of the above (1) to (3), the first p-type cladding layer 4 and the second p-type cladding layer 5 are made of AlInP or AlGaInP, and The Al composition ratio of the mold cladding layer 4 is larger than the Al composition ratio of the second p-type cladding layer 5.
[0039]
As described above, by using AlInP or AlGaInP as the first p-type cladding layer 4 and the second p-type cladding layer 5, a good carrier confinement layer for the visible light semiconductor laser and a spike for current confinement are formed. can do.
[0040]
(5) The present invention provides a method for manufacturing a semiconductor laser device using a substrate having a first plane orientation and a second plane orientation. The first method has a large forbidden band width with the p-side cladding layer close to the active layer 3. P-type cladding layer 4 and second p-type cladding layer 5 having a small forbidden band width, and the hole concentration in the first plane orientation portion of the p-side cladding layer is positive in the second plane orientation portion. The plane orientation is selected so as to be higher than the pore concentration.
[0041]
In this way, by appropriately selecting the plane orientation of the substrate, the plane orientation dependence of the impurity incorporation rate is utilized to make the gap between the first p-type cladding layer 4 and the second p-type cladding layer 5. It is possible to control the thickness of the spike formed on the substrate.
[0042]
(6) In the present invention, in the above (5), the second plane orientation is either the (100) plane or the (m11) A plane when m is a real number. The plane orientation is characterized by being a (m′11) A plane where m ′ is a real number of m ′ <m.
[0043]
In this way, in the case of a normal p-type impurity, the impurity concentration and the carrier concentration increase as the off angle increases in the A direction, that is, as m decreases, so m ′ <m. Only the hole concentration in the first region 9 can be made higher than the hole concentration in the second region 10.
[0044]
(7) In the present invention, when n is a real number of n> 7, n ′ is a real number of 2 ≦ n ′ ≦ 7, and n ″ is a real number of 3 ≦ n ″ ≦ 7, the (100) plane Alternatively, in the method of manufacturing a semiconductor laser device using the stepped substrate 1 having any one of the (n11) A plane as a main surface and the (n′11) A plane as an inclined surface, the (100) plane or the (n11) A plane The first p-type cladding layer 4 having a large forbidden band on the side close to the active layer 3 is provided on the active layer 3 with the active layer 3 having one of the principal surfaces and the (n ″ 11) A plane as an inclined surface. A p-side cladding layer constituted by the second p-type cladding layer 5 having a small forbidden band width, a cladding layer which becomes the n-type current confinement layer 6 on the main surface and becomes the p-type layer 7 on the inclined surface, and p The hole concentration in the region along the slope of the side cladding layer is higher than the hole concentration in the region along the main surface. Characterized in that it was.
[0045]
As described above, the surface orientation of the stepped substrate 1 is selected as described above, and the first p-type cladding layer 4 and the second p-type cladding layer 5 having different forbidden band widths are used to form a p-side cladding layer. By configuring, a current confinement mechanism by spike can be formed in the p-side cladding layer only by a normal epitaxial growth process, and a current confinement mechanism using the n-type current confinement layer 6 is also formed by alternate doping or simultaneous doping. can do.
[0046]
(8) Further, according to the present invention, in any one of the above (5) to (7), the first p-type cladding layer 4 and the second p-type cladding layer 5 are made of AlInP or AlGaInP, and The Al composition ratio of the mold cladding layer 4 is larger than the Al composition ratio of the second p-type cladding layer 5.
[0047]
Thus, in the present invention, since an etching process is not used in the middle of the growth process, an oxide film is easily formed, and AlInP or AlGaInP having a large forbidden band width including Al that is difficult to re-grow on the oxide film is formed. It can be used as the first p-type cladding layer 4 and the second p-type cladding layer 5, thereby forming a good carrier confinement layer and a current confinement spike for the visible light semiconductor laser with good reproducibility. Can do.
[0048]
DETAILED DESCRIPTION OF THE INVENTION
Here, an embodiment of the present invention will be described with reference to FIG.
2A is a perspective view of a slope oscillation type semiconductor laser, and FIG. 2B is a valence electron at a heterojunction interface along broken lines A and B in FIG. 2A. It is a figure which shows roughly the structure of the band end of a belt | band | zone.
[0049]
See Fig. 2 (a)
First, the carrier concentration having a main surface that is 6 ° off from the (100) plane to the (111) A plane is 4 × 10. ¹⁸ cm ^-3 A photoresist (not shown) is applied on the Si-doped n-type GaAs substrate 11 and a stripe-like resist pattern having a width of 150 μm is formed at intervals of 150 μm by a photolithography process.
[0050]
Next, by etching using a HF-based etchant using the resist pattern as a mask, a groove having a depth of 0.5 μm having a slope with an inclination angle of about 14 ° with respect to the main surface, that is, an off angle with respect to the (100) plane of 20 ° Form.
In this case, the plane orientation of the slope is approximately (411) A plane, but such orientation can be obtained with good reproducibility by adjusting the composition of the HF-based etchant and the reaction temperature.
[0051]
Next, all layers from the buffer layer to the contact layer are continuously grown by the MOVPE method. In this case, throughout the entire growth process, the growth pressure is 50 Torr, the growth efficiency is about 800 μm / mol, and hydrogen of the carrier gas is added. The total flow rate included is 8000 sccm.
[0052]
First, TMG (trimethylgallium) and AsH are formed on the n-type GaAs substrate 11 on which the step is formed with the substrate temperature set at 680 ° C. _Three Using AsH _Three The source gas is flowed so that the / TMG ratio becomes 100 and the growth rate becomes 1 μm / hour, and Si ₂ H ₆ As a source of impurities, the carrier concentration is 5 × 10 ¹⁷ cm ^-3 The n-type GaAs buffer layer 12 having a thickness of 1.5 μm is grown.
[0053]
Next, TEG (triethylgallium), TMI (trimethylindium), and PH in a state where the substrate temperature is also 680 ° C. _Three Using PH _Three / (TEG + TMI) ratio is 500, the source gas is flowed so that the growth rate is 1 μm / hour, and Si ₂ H ₆ As a source of impurities, the carrier concentration is 1 × 10 ¹⁸ cm ^-3 And an n-type GaInP intermediate layer (Ga _0.5 In _0.5 P) 13 is grown.
[0054]
The n-type GaInP intermediate layer 13 is provided to alleviate the difference in the forbidden band width between the GaAs layer and the AlGaInP layer serving as the cladding layer, and to reduce the energy barrier formed at the heterojunction interface.
[0055]
Next, TMA (trimethylaluminum), TEG, TMI, and PH with the substrate temperature set at 680 ° C. _Three Using PH _Three / (TMA + TEG + TMI) ratio is 110, and the source gas is flowed so that the growth rate is 2.2 μm / hour. ₂ H ₆ As a source of impurities, the carrier concentration is 5 × 10 ¹⁷ cm ^-3 N-type AlGaInP cladding layer (Al _0.35 Ga _0.15 In _0.5 P) 14 is grown.
The reason why Si is used as an impurity in the growth of the n-type layer is that the electron concentration on the slope does not need to be lower than the electron concentration on the main surface.
[0056]
Next, TMA, TEG, TMI, and PH with the substrate temperature set at 680 ° C. _Three Using PH _Three / (TMA + TEG + TMI) ratio is 400, the raw material gas is flowed so that the growth rate is 1 μm / hour, and an undoped Al having a thickness of 500 mm. _0.2 Ga _0.3 In _0.5 P light guide layer is grown.
[0057]
Next, TEG, TMI, and PH with the substrate temperature set at 680 ° C. _Three Using PH _Three / (TEG + TMI) ratio is 400, and the raw material gas is flowed so that the growth rate is 0.8 μm / hour, and the undoped Ga is formed with a thickness of 60 mm. _0.44 In _0.56 Three P-well layers and TMA, TEG, TMI, and PH _Three Using PH _Three / (TMA + TEG + TMI) ratio is 400 and undoped Al having a thickness of 50 mm by flowing the source gas so that the growth rate is 1.0 μm / hour. _0.2 Ga _0.3 In _0.5 Two P barrier layers were grown alternately, and then again undoped Al with a thickness of 500 mm _0.2 Ga _0.3 In _0.5 The strained MQW active layer 15 is formed by growing the P light guide layer.
[0058]
Next, with the substrate temperature set at 680 ° C., TMA, TMI, and PH _Three Using PH _Three The source gas is flowed so that the / (TMA + TMI) ratio becomes 110 and the growth rate becomes 2.2 μm / hour, and DEZn (diethyl zinc) as the impurity source becomes DEZn / (TMA + TMI) ratio 0.1. The carrier concentration in the portion along the slope is 7 × 10 ¹⁷ cm ^-3 And the carrier concentration in the portion along the main surface is 1.2 × 10 ¹⁷ cm ^-3 And a p-type AlInP cladding layer (Al) serving as a first p-type cladding layer on the active layer side having a thickness of 0.15 μm. _0.5 In _0.5 P) 16 is grown.
[0059]
Then TMA, TEG, TMI and PH _Three Using PH _Three By flowing the source gas so that the / (TMA + TEG + TMI) ratio becomes 110 and the growth rate is 2.2 μm / hour, and DEZn as the impurity source is allowed to flow so that the DEZn / (TMA + TMI) ratio becomes 0.1. The carrier concentration along the slope is 7 × 10 ¹⁷ cm ^-3 And the carrier concentration in the portion along the main surface is 1.2 × 10 ¹⁷ cm ^-3 And a p-type AlGaInP clad layer (Al _0.35 Ga _0.15 In _0.5 P) The layer 17 is grown.
[0060]
Next, TMA, TEG, TMI, and PH with the substrate temperature set at 680 ° C. _Three Using PH _Three / (TMA + TEG + TMI) ratio is 110, the source gas is flowed so that the growth rate is 2.2 μm / hour, and DEZn and H as impurity sources ₂ Al is flown by 30 cycles of Se by alternately flowing Se, and the total thickness is 0.30 μm. _0.35 Ga _0.15 In _0.5 A P clad layer is formed.
[0061]
This Al _0.35 Ga _0.15 In _0.5 In the P-clad layer, the layer doped with Se has an n-type carrier concentration of 6 × 10 6 along the main surface. ¹⁷ cm ^-3 The n-type carrier concentration in the portion along the slope is 2 × 10 ¹⁷ cm ^-3 On the other hand, in the layer doped with Zn, the p-type carrier concentration in the portion along the main surface is 2.4 × 10. ¹⁷ cm ^-3 The p-type carrier concentration in the portion along the slope is 1.4 × 10 ¹⁸ cm ^-3 It becomes.
[0062]
In this growth process, the p-type impurities in the portion along the slope enter the n-type layer by the diffusion principle due to the difference in impurity concentration and are 1.4 × 10 6. ¹⁸ cm ^-3 What was was averaged 7 × 10 ¹⁷ cm ^-3 Thus, the entire portion along the slope is converted into the p-type AlGaInP layer 19.
[0063]
On the other hand, in the portion along the main surface, the p-type impurity is blocked by the high-concentration n-type impurity and no diffusion occurs, and almost no diffusion of the n-type impurity occurs, so that the doping profile of the pnpnpn structure. However, since these layers are all thin, the p-type doped portion is depleted by carrier diffusion to form a uniform n-type AlGaInP current confinement layer 18, and current confinement is performed by this n-type AlGaInP current confinement layer 18.
[0064]
Next, TMA, TEG, TMI, and PH with the substrate temperature set at 680 ° C. _Three Using PH _Three / (TMA + TEG + TMI) ratio is 273, the source gas is flowed so that the growth rate is 2.2 μm / hour, and DEZn is flowed as an impurity source, so that the carrier concentration along the slope is 7 × 10 ¹⁷ cm ^-3 And the carrier concentration in the portion along the main surface is 1.2 × 10 ¹⁷ cm ^-3 And a p-type AlGaInP clad layer (Al _0.35 Ga _0.15 In _0.5 P) The layer 20 is grown.
[0065]
Next, TEG, TMI, and PH with the substrate temperature set at 680 ° C. _Three Using PH _Three / (TEG + TMI) ratio is 500, the source gas is flowed so that the growth rate is 1 μm / hour, and DEZn is flowed as an impurity source, so that the carrier concentration along the slope is 1 × 10 ¹⁸ cm ^-3 And a p-type GaInP intermediate layer (Ga _0.5 In _0.5 P) 21 is grown.
[0066]
Next, with the substrate temperature set at 680 ° C., TMG and AsH _Three Using AsH _Three By flowing the source gas so that the / TMG ratio becomes 100 and the growth rate becomes 1 μm / hour and by flowing DEZn as an impurity source, the carrier concentration in the portion along the slope is 2 × 10 ¹⁸ cm ^-3 A p-type GaAs contact layer 22 having a thickness of 1 μm is grown.
[0067]
Next, although not shown, an element isolation region having a width of 100 μm is formed, and then an n-type contact electrode made of Au / Ge / Au and a p-type contact electrode made of Au.Zn / Au are deposited by vapor deposition to obtain a width of 300 μm. Then, cleave into a 700 μm long chip and bond to heat sink with p-side UP.
[0068]
Refer to FIG.
In the inclined oscillation type semiconductor laser of the present invention described above, at the heterojunction interface between the p-type AlInP cladding layer 16 serving as the first p-type cladding layer and the p-type AlGaInP cladding layer 17 serving as the second p-type cladding layer. Due to the difference in electron affinity χ between them, an energy gap corresponding to the difference in electron affinity χ, that is, a spike is formed at the band edge of the valence band.
[0069]
The thickness of the spike depends on the impurity concentration, the thickness of the spike formed in the high impurity concentration portion is thin, and the thickness of the spike formed in the low impurity concentration portion is large.
[0070]
Therefore, since the thickness of the spike formed in the portion indicated by the broken line A in FIG. 2A, that is, the slope portion having a high impurity concentration is thin, holes can tunnel the spike, Current will flow.
[0071]
On the other hand, since the thickness of the spike formed in the broken line B portion of FIG. 2A, that is, the main surface portion having a low impurity concentration, is thick, holes cannot tunnel the spike, and in the peripheral portion. No current flows.
[0072]
That is, in the present invention, since current confinement is performed by the n-type current confinement layer and the heterojunction interface spike, the p-type cladding layer between the n-type current confinement layer and the active layer is thick. In addition, the reactive current can be effectively reduced.
[0073]
In addition, in the present invention, the thickness of the spike at the heterojunction interface is controlled by utilizing the dependence of the impurity doping on the plane orientation, so that a current confinement mechanism with a small reactive current is formed only by a normal epitaxial growth process. Thus, a semiconductor laser device with low power consumption and low heat generation can be manufactured at low cost.
[0074]
In the above embodiment, the current confinement layer is formed by alternately doping p-type impurities and n-type impurities. However, the current confinement layer may be formed by simultaneous doping. In that case, by simultaneously doping the p-type impurity and the n-type impurity, the portion along the main surface becomes an n-type region, as can be seen from FIG. It becomes a constriction layer.
[0075]
In the embodiment of the present invention, an AlInP layer is used as the first p-type cladding layer and an AlGaInP layer is used as the second p-type cladding layer in order to form spikes at the heterojunction interface. The first p-type cladding layer may also be formed of AlGaInP. In that case, the Al ratio of the first p-type cladding layer is made larger than the Al ratio of the second p-type cladding layer, and the electron affinity χ is Smaller and forbidden bandwidth E _g Should be larger.
[0077]
In the embodiment of the present invention, an n-type substrate is used. However, the conductivity type may be reversed using a p-type substrate. In that case, an n-type current blocking layer is provided on the substrate side. The p-side cladding layer provided on the substrate side may be composed of two p-type cladding layers having different forbidden band widths.
[0078]
In the embodiment of the present invention, the active layer is an MQW active layer. However, the active layer is not limited to such an active layer, and may have an SQW (single quantum well) structure or a quantum well. An active layer having no structure may be used.
[0079]
【The invention's effect】
According to the present invention, at least a part of the current confinement structure is formed by using spikes formed at the heterojunction interface when the p-side cladding layer is composed of at least two p-type cladding layers. Therefore, the reactive current can be effectively reduced without reducing the thickness of the p-side cladding layer immediately below the n-type current confinement layer, which greatly contributes to low power consumption of the short wavelength red semiconductor laser device.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a basic configuration of the present invention.
FIG. 2 is an explanatory diagram of an embodiment of the present invention.
FIG. 3 is an explanatory view of a conventional single growth type semiconductor laser device.
FIG. 4 is an explanatory diagram of the plane orientation dependence of doping efficiency.
FIG. 5 is an explanatory diagram of a conventional heterojunction current confined semiconductor laser device.
FIG. 6 is an explanatory diagram of a conventional ridge type semiconductor laser device.
[Explanation of symbols]
1 Step board
2 n-type cladding layer
3 Active layer
4 First p-type cladding layer
5 Second p-type cladding layer
6 n-type current confinement layer
7 p-type layer
8 p-type cladding layer
9 First area
10 Second region
11 n-type GaAs substrate
12 n-type GaAs buffer layer
13 n-type GaInP interlayer
14 n-type AlGaInP cladding layer
15 Strained MQW active layer
16 p-type AlInP cladding layer
17 p-type AlGaInP cladding layer
18 n-type AlGaInP current confinement layer
19 p-type AlGaInP layer
20 p-type AlGaInP cladding layer
21 p-type GaInP intermediate layer
22 p-type GaAs contact layer
31 n-type GaAs substrate
32 n-type GaAs buffer layer
33 n-type GaInP intermediate layer
34 n-type AlGaInP cladding layer
35 MQW active layer
36 p-type AlGaInP cladding layer
37 n-type AlGaInP current confinement layer
38 p-type AlGaInP layer
39 p-type AlGaInP cladding layer
40 p-type GaInP interlayer
41 p-type GaAs contact layer
51 n-type GaAs substrate
52 n-type AlGaInP cladding layer
53 GaInP active layer
54 p-type AlGaInP cladding layer
55 p-type GaInP spike prevention layer
56 p-type GaAs contact layer
61 n-type GaAs substrate
62 n-type GaAs buffer layer
63 n-type AlGaInP cladding layer
64 Strained MQW active layer
65 p-type AlGaInP cladding layer
66 p-type GaInP etching stop layer
67 p-type AlGaInP cladding layer
68 p-type GaInP interlayer
69 n-type GaAs current confinement layer
70 p-type GaAs contact layer
71 Effective current
72 Reactive current
73 Laser light

Claims (8)

The p-side cladding layer, constituted by a small second p-type cladding layer of the large first p-type cladding layer and the bandgap of prohibited system band width, the hole concentration in the pre-Symbol p-type cladding layer becomes high and has the surface orientation of the first region, unlike the surface orientation of the second region which is the hole concentration low, together with the first p-type cladding layer is in contact with the active layer, the second region The semiconductor laser device according to claim 1, wherein the second p-type cladding layer is in contact with the n-type current confinement layer . The plane orientation of the second region is either (100) plane or (m11) A plane when m is a real number, and the plane orientation of the first region is m ′ = m ′. 2. The semiconductor laser device according to claim 1, wherein when it is a real number of m, it is a (m′11) A plane. When n is a real number of n> 7, n ′ is a real number of 2 ≦ n ′ ≦ 7, and n ″ is a real number of 3 ≦ n ″ ≦ 7, either (100) plane or (n11) A plane In the semiconductor laser device using the stepped substrate with the (n′11) A plane as the inclined surface, the (100) plane or the (n11) A plane is the main plane, and (n ″ 11) A An active layer having an inclined surface, a p-side cladding layer having a hole concentration in the region along the inclined surface higher than the hole concentration in the region along the main surface on the active layer; and the main surface A first p-type cladding layer and a forbidden band having a large forbidden band at least on the side close to the active layer. Semiconductor comprising the second p-type cladding layer having a small width Laser device. The first p-type cladding layer and the second p-type cladding layer are made of AlInP or AlGaInP, and the Al composition ratio of the first p-type cladding layer is larger than the Al composition ratio of the second p-type cladding layer. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is a semiconductor laser device. In a method of manufacturing a semiconductor laser device using a substrate having a first plane orientation and a second plane orientation, a p-side cladding layer is formed of a first p-type cladding layer that is close to an active layer and has a large forbidden band width. And a hole concentration in the first plane orientation portion of the p-side cladding layer is higher than a hole concentration in the second plane orientation portion. A method of manufacturing a semiconductor laser device, wherein the plane orientation is selected as described above. The second plane orientation is either a (100) plane or a (m11) A plane when m is a real number, and the first plane orientation is a real number where m ′ is m ′ <m. 6. The method of manufacturing a semiconductor laser device according to claim 5, wherein the surface is a (m′11) A plane. When n is a real number of n> 7, n ′ is a real number of 2 ≦ n ′ ≦ 7, and n ″ is a real number of 3 ≦ n ″ ≦ 7, either (100) plane or (n11) A plane In the method of manufacturing a semiconductor laser device using a stepped substrate having a principal surface of (n′11) A and an inclined surface of (n′11) A, either the (100) plane or the (n11) A plane is the principal surface, and (n ″ 11) An active layer having an A plane as an inclined surface is provided, and a first p-type cladding layer having a large forbidden band and a second p-type cladding layer having a small forbidden band on the side close to the active layer are provided on the active layer. And a clad layer that becomes an n-type current confinement layer on the main surface and becomes a p-type layer on the inclined surface, and holes in a region along the inclined surface of the p-side cladding layer The concentration is higher than the hole concentration in the region along the main surface. The method of manufacturing a semiconductor laser device according to. The first p-type cladding layer and the second p-type cladding layer are made of AlInP or AlGaInP, and the Al composition ratio of the first p-type cladding layer is larger than the Al composition ratio of the second p-type cladding layer. 8. The method of manufacturing a semiconductor laser device according to claim 5, wherein the semiconductor laser device is a semiconductor laser device.

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