JP2004031657A - Semiconductor light emitting element, method of manufacturing the same, and semiconductor light emitting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize, in the level of practical use, a semiconductor light emitting element, using a nitride based semiconductor, such as a vertical resonator type semiconductor laser in which the polarizing direction is controlled, a vertical resonator type semiconductor laser which ensures higher efficiency and a resonant cavity type light emitting element and also realize a semiconductor light emitting apparatus using such semiconductor light emitting element. <P>SOLUTION: The vertical resonator type semiconductor light emitting element comprises a nitride semiconductor n-GaN layer 102 including the plane (1-101) as the main surface formed on a silicon substrate 1, a spacer layer 104 as a lower clad layer formed on the n-GaN layer 102, a quantum well active layer 105 formed on the spacer layer 104, and a spacer layer 107 as an upper clad layer formed on the quantum well active layer 105. The plane orientation of the main surface of the quantum well active layer 105 is (1-101). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor light emitting device, a method for manufacturing the same, and a semiconductor light emitting device having the semiconductor light emitting device.
[0002]
[Prior art]
Light emitting devices such as LEDs and semiconductor lasers have been realized using semiconductors having a hexagonal structure, such as nitride semiconductor materials including GaN, InN, AlN, and their mixed crystal semiconductors. Structures have also been proposed for type surface emitting lasers (VCSELs).
[0003]
For example, in a vertical cavity surface emitting laser disclosed in Japanese Patent Application Laid-Open No. 10-135576, a <0001> direction of a nitride semiconductor is arranged in a stacked surface of an epitaxial layer such as an active layer, and a direction perpendicular to the stacked surface. In the <1-100> direction.
[0004]
In the semiconductor laser of this conventional example, the active layer has a (1-100) plane, unlike the conventional semiconductor laser in which the main layer of the active layer has a (0001) plane. Vertically emitted laser light is polarized in a particular direction. This solves the problem that the polarization direction of the laser light of the conventional vertical cavity surface emitting laser is difficult to determine.
[0005]
[Problems to be solved by the invention]
In the above-mentioned conventional example, it is stated that the semiconductor laser can be realized by manufacturing a laser using, for example, a GaN (1-100) plane substrate, but such a substrate has not been widely marketed. . Since a nitride semiconductor has a property of easily growing a crystal in the <0001> direction, it is difficult to stably manufacture a (1-100) plane substrate made of a nitride semiconductor. Therefore, a GaN (1-100) plane substrate could not be supplied stably.
[0006]
In the case where another substrate is used, the nitride semiconductor easily grows in crystal such that the main surface becomes the (0001) plane, and it has been difficult to obtain a semiconductor laser having the above crystal orientation. Therefore, it was impossible to realize the above-described conventional vertical cavity semiconductor laser at a practical level.
[0007]
The present invention solves such problems, and uses a nitride-based semiconductor, a vertical cavity semiconductor laser in which the polarization direction is controlled, a highly efficient vertical cavity semiconductor laser, and a resonant cavity semiconductor laser. It is an object to realize a semiconductor light emitting element such as a light emitting element and a semiconductor light emitting device having the semiconductor light emitting element at a practical level.
[0008]
[Means for Solving the Problems]
In one aspect, the semiconductor light emitting device of the present invention has an active layer containing a nitride semiconductor and a clad layer sandwiching the active layer, and has a resonator in the direction in which the active layer and the clad layer are stacked. Then, the plane orientation of the main surface of the active layer is set to (1-101).
[0009]
By controlling the plane orientation of the main surface of the active layer to (1-101) as described above, it is possible to improve the controllability of the polarization direction in a semiconductor light emitting device having a resonator in the stacking direction of the active layer and the cladding layer. Can be. The (1-101) plane can be stably obtained during crystal growth by using a specific substrate.
[0010]
In another aspect, a semiconductor light emitting device of the present invention includes a substrate, and a compound semiconductor layer formed of a nitride semiconductor formed on the substrate. The substrate has a groove having a surface inclined at 62 degrees from the main surface of the substrate or a surface inclined within 3 degrees in an arbitrary direction from this surface as a slope, and the compound semiconductor layer is formed on the slope. Is done. An active layer containing a nitride semiconductor and a clad layer sandwiching the active layer are provided on the compound semiconductor layer, and a resonator is provided in a direction in which the active layer and the clad layer are stacked. The active layer has a plane orientation substantially coincident with the main surface of the substrate.
[0011]
By forming a compound semiconductor layer using the above substrate, the plane orientation of the main surface of the compound semiconductor layer can be set to (1-101). Therefore, the plane orientation of the main surface of the active layer formed on the compound semiconductor layer can be set to (1-101) substantially coincident with the main surface of the substrate, and resonance occurs in the stacking direction of the active layer and the cladding layer. The controllability of the polarization direction can be improved in a semiconductor light emitting device having a cavity. Further, by using the above substrate, the (1-101) plane can be obtained stably during crystal growth.
[0012]
In still another aspect, a semiconductor light emitting device of the present invention includes a silicon substrate and a compound semiconductor layer formed on the silicon substrate and formed of a nitride semiconductor. The compound semiconductor layer is constituted by a plane obtained by rotating the (100) plane by 7.3 degrees around the [01-1] axis, or a plane that is inclined within 3 degrees in an arbitrary direction from this plane. It is formed using a silicon substrate having a main surface, and the silicon substrate includes a groove having a (111) plane as a slope. The compound semiconductor layer is formed on the slope. The semiconductor device has an active layer containing a nitride semiconductor and a clad layer sandwiching the active layer, and has a resonator in the stacking direction of the active layer and the clad layer.
[0013]
Even when a compound semiconductor layer is formed using a silicon substrate as described above, a compound semiconductor layer in which the plane orientation of the main surface is (1-101) can be obtained. Therefore, the plane orientation of the main surface of the active layer formed on the compound semiconductor layer can also be (1-101), and the polarization direction of the semiconductor light emitting device having a resonator in the lamination direction of the active layer and the cladding layer Controllability can be improved. Further, by using the above substrate, the (1-101) plane can be obtained stably during crystal growth.
[0014]
The plane orientation of the main surface of the cladding layer or the active layer is preferably (1-101). The <0001> direction of the compound semiconductor layer is preferably substantially perpendicular to the slope. The groove preferably extends along the [11-20] direction of the nitride semiconductor forming the active layer. The semiconductor light emitting device is preferably a semiconductor laser device, and laser light emitted from the semiconductor laser device is polarized in a direction parallel or perpendicular to the groove. Further, it is preferable that a film on which the growth of the nitride semiconductor is suppressed is formed on at least a part of the surface of the substrate other than the slope.
[0015]
A semiconductor light-emitting device according to the present invention includes the above-described semiconductor light-emitting element and a wavelength conversion material that absorbs light emitted from the semiconductor light-emitting element and emits light having a different wavelength from the emitted light.
[0016]
In one aspect, a method for manufacturing a semiconductor light emitting device according to the present invention includes the following steps. On the main surface of the substrate, a groove having a surface inclined at 62 degrees from the main surface or a surface inclined within 3 degrees in an arbitrary direction from this surface as a slope is formed. A nitride semiconductor is crystal-grown on the slope to form a compound semiconductor layer having a plane substantially parallel to the main surface of the substrate. On the compound semiconductor layer, a lower cladding layer, an active layer, and an upper cladding layer, each composed of a nitride semiconductor, are laminated in this order.
[0017]
By crystal-growing a nitride semiconductor on the slope of the groove provided in the substrate, a compound semiconductor layer having a plane substantially parallel to the main surface of the substrate can be formed. That is, a compound semiconductor layer having the (1-101) plane as a main surface can be formed stably. By stacking a lower clad layer, an active layer, and an upper clad layer made of a nitride semiconductor on the compound semiconductor layer, a lower clad layer, an active layer, and an upper clad having a (1-101) plane as a main surface are laminated. A layer can be formed stably, and a semiconductor light-emitting element having excellent control of the polarization direction can be obtained.
[0018]
In another aspect, a method for manufacturing a semiconductor light emitting device of the present invention includes the following steps. A lower clad layer, an active layer, and an upper clad layer each composed of a nitride semiconductor are stacked in this order on a main surface of a compound semiconductor layer having a (1-101) plane of a nitride-based semiconductor as a main surface.
[0019]
Also in the case of this aspect, the lower clad layer, the active layer, and the upper clad layer having the (1-101) plane as the main surface can be formed stably, and a semiconductor light emitting device excellent in control of the polarization direction can be obtained. be able to.
[0020]
In this specification, a nitride semiconductor is a compound semiconductor mainly composed of a group III element and an N element. _x In _y Ga _1-xy In addition to N (0 ≦ x, y ≦ 1), a crystal in which a part of the group III element (about 20% or less) is replaced by another element such as B or Tl, or a part of the N element (10% Or less) is substituted with another element such as As, P, Sb.
[0021]
In addition, in the present specification, when a specific surface or direction is indicated, only the surface or direction that is mathematically strictly defined should not be interpreted as the scope of the present invention. The effects of the present invention are not lost even if they slightly deviate from those planes / directions. Specifically, even if deviated by about 3 degrees, it should be understood that the present invention is within the applicable range. .
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described below with reference to embodiments.
[0023]
<Embodiment 1>
FIG. 1 is a conceptual diagram for forming a (1-101) facet surface 70 of a nitride semiconductor film (compound semiconductor layer) according to the present embodiment, and FIG. 2 is a nitride semiconductor light emitting device according to the present embodiment. FIG. 3 is a schematic cross-sectional view illustrating a structure of an element.
[0024]
The nitride semiconductor light emitting device of the present embodiment is formed on a (001) silicon substrate 1 which is 7.3 ° off in the [0-1-1] direction. The silicon substrate 1 has a stripe-shaped groove having a (111) facet surface 61 having an inclined surface at an angle of 62 degrees from the main surface, and is sequentially flattened from the facet surface 61 as described below. It has an n-AlGaInN layer 10 and an n-GaN layer 102 that are stacked in layers. It should be noted that a surface inclined from the facet surface 61 in an arbitrary direction within 3 degrees may be a slope.
[0025]
The upper surface of the n-GaN layer 102 is substantially parallel to the main surface of the substrate and is a (1-101) plane. Then, as shown in FIG. 2, the n-InAlN / GaN multilayer reflective film 103, the n-AlGaN spacer layer 104, and the _w Ga _1-w N (0 <w <1) well layer and In _v Ga _1-v Each nitride of the multiple quantum well active layer 105 (oscillation wavelength: 400 nm), the AlGaN cap layer 106, the p-AlGaN spacer layer 107, and the p-GaN contact layer 108 having an alternate multilayer structure with an N (0 ≦ v <w) barrier layer An object semiconductor layer is formed. The plane orientation of the main surface of each nitride semiconductor layer including the active layer (multi-quantum well active layer 105) and the spacer layer serving as a cladding layer is (1-101), and the main surface of the silicon substrate 1 is Substantially coincides with the plane orientation.
[0026]
Further, on the upper surface of the p-GaN contact layer 108, a metal electrode 110 is formed in a mesh shape, and a dielectric multilayer reflective film 111 is formed so as to cover the upper surface including the metal electrode 110. Each layer is etched from the upper surface so that the n-GaN layer 102 is exposed, and a metal electrode 109 is provided on the n-GaN layer 102. Thus, a vertical resonator structure is provided in which the active layer and the spacer layer serving as a cladding layer for confining carriers in the active layer are provided on both sides thereof, and a reflecting mirror is further provided outside the spacer layer. .
[0027]
In the present embodiment, the shape of the light output portion of the vertical resonator is a circle having a diameter d = 50 μm, which is defined by an opening for light output. An insulating protective film 112 is provided on a side surface of the vertical resonator. Although not shown, a pad electrically connected to the metal electrode 110 is provided as appropriate for forming a wire for electrical connection to the outside. The distance between the reflectors, that is, the distance between the multilayer reflective film 103 and the dielectric multilayer reflective film 111 is 3λ, and the active layer is located at the center.
[0028]
As a dopant for forming an n-type semiconductor, Si, Ge, O, S, and Se are preferable, and as a dopant for forming a p-type semiconductor, Be, Cd, and Mg are preferable. It is also preferable to add any of Si, Ge, O, S, and Se at the same time as Be, Cd, and Mg in order to obtain a p-type layer having low resistance and low dopant diffusion.
[0029]
Next, a method for manufacturing the semiconductor light emitting device (semiconductor laser device) of the present embodiment will be described with reference to FIGS.
[0030]
First, the (001) silicon substrate (wafer) 1 which has been turned off by 7.3 ° in the [0-1-1] direction is washed, and a silicon oxide film is formed thereon by sputtering or CVD (Chemical Vapor Deposition). A mask 52 made of an insulating film such as a silicon nitride film or the like is deposited to a thickness of 100 nm. Thereafter, as shown in FIG. 4, the mask 52 is removed in a stripe shape by using a photolithography technique. At this time, the direction of the stripe is along the Si [01-1] direction.
[0031]
Further, the silicon substrate 1 is etched with an alkali etchant such as KOH or an acid etchant such as buffered hydrofluoric acid to form a groove having a Si (111) facet surface 61 as shown in FIG. This groove is a stripe-shaped groove extending in the Si [01-1] direction (<11-20> direction of the nitride-based semiconductor). As shown in FIG. 1, the (111) facet surface 61 has a relationship of 62 degrees with respect to the main surface 60 of the silicon substrate 1 because the main surface 60 has the predetermined plane orientation. This surface is a flat facet surface obtained by the above-described etching, and can be easily obtained by appropriately adjusting the etchant temperature and the etching rate.
[0032]
At this time, the shape of the groove itself is a V-shape or a deformed V-shape in which the bottom region is flat, and the other slope is a (1-1-1) facet surface. Since the silicon substrate 1 is an off-substrate, the V-shape is not bilaterally symmetric, and the (111) slope is a plane inclined at about 62 ° with respect to the main surface 60, but the (1-1-1) slope is Is a surface inclined by about 47 °. By placing the silicon substrate 1 in an inclined state in the sputtering apparatus, a film is formed while preventing the film from being attached to the (111) facet surface 61, and the (1-1-1) facet surface is covered. A mask 52 made of a silicon oxide film or a silicon nitride film is applied to the state shown in FIG. This is used as a nitride semiconductor film or a substrate for producing a nitride semiconductor substrate.
[0033]
Then, a nitride semiconductor film is grown by MOCVD (metal organic chemical vapor deposition) under the following growth conditions. 7A to 7C are obtained by crystal-growing the n-AlGaInN intermediate layer 10 and the n-GaN layer 102 (compound semiconductor layer) shown in FIG. 1 on the facet surface 61 of the silicon substrate 1 subjected to the above process. Through the growth process as shown in b), a GaN crystal film having a flat GaN (1-101) facet surface 70 on the upper surface can be manufactured.
[0034]
Here, the n-AlGaInN intermediate layer 10 is a thin film having a thickness of about several hundred nm or less, which serves as a buffer layer. As shown in FIG. 7A, the crystal growth starts on the exposed (111) facet surface 61. The growing nitride semiconductor is oriented so that the <0001> direction is perpendicular to the slope. On the upper surface of the grown crystal, a GaN (1-101) facet surface 70 appears substantially parallel to the main surface of the substrate. Therefore, as shown in FIG. It becomes a crystal with a triangular prism shape. FIG. 1 is a diagram showing the crystal orientation and the like using the cross-sectional view in the state of FIG. 7B.
[0035]
As shown in FIG. 7C, as the crystal growth proceeds, the diameter of the triangular columnar crystal made of the nitride semiconductor increases, and finally, the adjacent triangular columnar crystals come into contact with each other. When the growth is further continued, the separated triangular columnar crystals are united to form a continuous film made of a GaN crystal having a flat GaN (1-101) facet surface 72 on the surface as shown in FIG. Is obtained.
[0036]
Similar results were obtained by using an AlInN intermediate layer, an AlGaN intermediate layer, and an AlN intermediate layer as the intermediate layers used in the initial stage of growth. If the intermediate layer is made of a nitride-based semiconductor crystal having a composition containing Al, the surface roughness of the Si substrate can be prevented.If the intermediate layer is made of a nitride-based semiconductor crystal having a composition containing In, By adding the n-type impurity, a low-resistance film can be formed.
[0037]
As described above, according to the present invention, when the silicon substrate 1 is used, the nitride semiconductor film is liable to grow c-axis oriented crystals on the substrate, and the relationship between the facet plane and the off angle of the substrate is 62 °. By using the silicon substrate 1, a crystal film having flat (1-101) facet surfaces 70 and 72 of a nitride semiconductor can be manufactured with high productivity.
[0038]
Subsequently, the respective nitride semiconductor layers from the n-InAlN / GaN multilayer reflective film 103 to the p-GaN contact layer 108 are sequentially stacked by MOCVD (metal organic chemical vapor deposition). Thereafter, etching is performed in a columnar shape until the n-GaN layer is exposed, and a mesh-shaped metal electrode 110 is provided on the upper surface of the p-GaN contact layer 108. As the metal electrode 110, Pd / Ag / Au, Ag / Pd / Au, Pd / Pt / Au, Pd / Mo / Au, or the like may be used. In order to be able to take out, a mesh having a line width of about 2 μm and individual openings of about 2 μm square was formed.
[0039]
Thereafter, a metal electrode 109 is provided around the columnar light emitting region of the n-GaN layer. Further, a dielectric multilayer film 111 is provided on the upper surface of the light emitting region. This includes TiO ₂ And SiO ₂ Or alternate multilayer films of ₂ O ₅ And SiO ₂ Are preferably used, and the reflectivity is set to about 80% or more for the laser oscillation operation. In addition, for LED operation (resonant cavity type LED), the reflectance may be about 50% or more.
[0040]
The silicon substrate 1 used here was tilted from the (001) plane in the 7.3 ° [0-1-1] direction, that is, rotated 7.3 degrees about the [01-1] axis from the (001) plane. The active layer has a plane orientation of (1-101), which has substantially the same plane orientation as the main plane 60 of the silicon substrate 1. Even when the silicon substrate 1 has, as a main surface, a surface inclined within 3 degrees in an arbitrary direction from the main surface 60, an extremely flat nitride semiconductor having a plane orientation close to the (1-101) plane An interface is obtained.
[0041]
When the characteristics of the manufactured semiconductor laser device were measured, an optical output of 0.5 W was obtained at an operating current of 300 mA. The polarization direction was, in many cases, the direction of the nitride semiconductor <11-20> constituting the active layer and the like. The direction was perpendicular to <11-20> depending on the state of the strain applied to the active layer by changing the growth temperature and the like of the clad layer. In each case, the polarization direction was stable because the active layer had in-plane crystallographic anisotropy.
[0042]
These results indicate that the presence of the active layer having the predetermined plane orientation provided a quantum well structure with extremely high flatness and a small fluctuation in the layer thickness. By tilting from the layer surface, the electric field generated by the piezo effect at the interface between the well and the barrier layer in the active layer is reduced, so that the carrier recombination probability of electron-hole pairs is increased and the luminous efficiency is improved. Since the main surface is not crystallographically isotropic, the laser oscillation light is polarized in one direction, so that the luminous efficiency is high, and the crystal growth direction is (1-1-) The change in the direction 101) is considered to be due to combined effects such as the fact that threading dislocations extending from the vicinity of the substrate interface did not reach the active layer and non-radiative recombination was reduced.
[0043]
In addition, in order to make the main surface of the active layer a non-isotropic (1-101) plane, a simple method of forming a predetermined groove-shaped structure on the substrate in advance is used. Could be realized. Furthermore, in the present invention, generation of cracks could be effectively suppressed. This is because the crystal growth of the AlGaN cladding layer proceeds in the [1-101] direction, and the growth of the nitride semiconductor is started on a slope that is considerably inclined from the main surface of the substrate, and the growth direction is changed from the middle ((1-101)). It is thought to be due to the effect of changing in the 101) direction.
[0044]
Normally, when a laser layer structure similar to that of the present embodiment is formed on the silicon substrate 1, several hundred cracks / mm are generated, but almost no cracks are generated by the present invention. Cracks are less likely to occur than in the case where a laser structure similar to that of the present embodiment is formed on a sapphire substrate, and the effect of suppressing cracks is remarkable.
[0045]
As described above, in the semiconductor laser device, the threshold value was reduced, cracks and defects were suppressed, and the device life was improved. Note that the effects described here can also be seen in the light-emitting elements described in other embodiments.
[0046]
In addition, the present invention has a resonator in the stacking direction having a (1-101) plane as a main surface, as compared with the case where the main surface of the active layer is a (1-100) plane as in the conventional technique. In the semiconductor light emitting device of (1), since the (1-101) plane is a surface formed as a stable surface during crystal growth, flatness of the active layer is easily obtained. In addition, since the threshold current density is small and the number of defects is small, there is an advantage that the life characteristics are excellent. In particular, in a vertical cavity type light emitting element, it is necessary to form a multilayer reflecting film as a reflecting mirror, and as in the present invention, the (1-101) plane in which a flat surface can be obtained in each semiconductor layer is used as a main surface. The technique of growing directly as described above directly relates to the flatness of such a multilayer reflective film, and makes it easy to obtain a desired reflectance.
[0047]
In the following embodiments, including this embodiment, as the intermediate layer used in the initial stage of growth, in addition to the AlGaInN intermediate layer, an AlInN intermediate layer, an AlGaN intermediate layer, or AlN may be used. . In selecting the composition of the intermediate layer, it is preferable to reduce the Ga composition in order to suppress the roughness of the silicon substrate 1 at the beginning of growth, and to reduce the resistance of the interface when a current flows through the silicon substrate 1. In order to reduce the amount of Al, the Al composition is reduced and n-type impurities such as Si are reduced by 10%. ¹⁷ cm ^-3 It is desirable to perform the above high doping.
[0048]
Alternatively, an n-side metal electrode may be provided on the silicon substrate 1 so that a current flows from the nitride semiconductor through the silicon substrate 1. In this case, a voltage drop occurs at the interface between the nitride semiconductor and the silicon substrate 1. However, it is also effective to provide an electrode for short-circuiting the n-type nitride semiconductor and the silicon substrate 1 to reduce a voltage drop, and this can also be used as a growth suppressing film.
[0049]
Furthermore, in the semiconductor element of the present embodiment, the interval between the grooves provided in the silicon substrate is of the same order as the size of the semiconductor element, and in FIG. Although a groove is formed, application of the present invention is not limited to such a case, and a groove may be provided more sparsely, and conversely, several tens to several hundreds are formed in the element. It is also effective to provide grooves densely as described above. The interval between the grooves may be 1 μm to 1000 μm, and the depth of the 62-degree slope, which is the slope of the groove, may be 0.1 μm to 100 μm.
[0050]
<Embodiment 2>
In the first embodiment, the light emitting element structure is directly manufactured on the silicon substrate 1 inclined by 7.3 degrees from the (001) plane. However, this silicon substrate 1 is used as a base substrate for manufacturing a GaN substrate. It is also possible to form a semiconductor laser device after producing a GaN substrate composed of a continuous film.
[0051]
The wafer in the state shown in FIG. 7D described in the manufacturing process of the first embodiment is introduced into an HVPE (hydride VPE) apparatus. N ₂ Carrier gas and NH ₃ Are respectively flown at 5 (l / min.), And the temperature of the substrate is raised to about 1050 ° C. After that, GaCl is applied on the substrate at 100 (cm). ³ / Min. ) To start the growth of a thick GaN film. GaCl is generated by flowing HCl gas through Ga metal maintained at about 850 ° C. In addition, by doping an impurity gas using an impurity doping line which is independently piped to the vicinity of the substrate, the impurity can be arbitrarily doped during the growth. In the present embodiment, for the purpose of doping with Si, at the same time as the growth is started, monosilane (SiH ₄ ) Is supplied at 200 (nmol / min.) (Si impurity concentration is about 3.8 × 10 ¹⁸ cm ^-3 ) To grow a Si-doped GaN film.
[0052]
By the above method, growth is performed for 8 hours, and GaN having a total thickness of about 350 μm is grown on the silicon substrate 1. After the growth, the silicon substrate 1 is removed by polishing or etching to obtain an extremely flat GaN substrate having a (1-101) facet surface 70. Thus, according to the present embodiment, it is possible to obtain a nitride semiconductor (GaN) substrate having facet (1-101) plane 70 on the surface.
[0053]
By sequentially forming the vertical cavity surface emitting laser structure of the first embodiment on this n-GaN substrate (100 μm thick) by the same method as that of the first embodiment, the semiconductor laser of this embodiment is formed. An element (wafer) is obtained. However, an n-side metal electrode is formed on the back surface of the n-GaN substrate. The obtained semiconductor laser device is placed on a base such as a stem or a lead frame with a metal electrode facing down, and is operated by supplying power from the outside.
[0054]
As described above, using the silicon substrate 1 as a starting substrate, an extremely flat GaN substrate having a (1-101) facet surface 70 was manufactured, and then a semiconductor laser device was manufactured. Thus, a semiconductor light emitting device having a low oscillation threshold was obtained. Was done.
[0055]
When the characteristics of the manufactured semiconductor laser device were measured, a laser output with an optical output of 1 W was obtained at a drive current of 0.6 A. Compared with the first embodiment, the substrate was made of GaN having excellent heat conduction, so that the light output was less likely to be saturated up to a higher current region.
[0056]
<Embodiment 3>
In the first embodiment, the groove slope inclined at about 62 degrees from the silicon main surface is obtained by utilizing the property that the Si (111) plane is easily formed by an etching method using an etchant (wet etching). The slope obtained in this way is a so-called crystal facet, and has not only stable processing accuracy but also excellent flatness, and is extremely excellent as a base for growing a nitride semiconductor.
[0057]
However, the scope of the present invention is not limited to this. According to various experiments performed by the inventors of the present application, the silicon substrate 1 is not only used when the surface inclined by 7.3 degrees from the (001) plane is used as the main surface but also when another surface is used as the main surface. A groove having an inclined surface of 62 degrees with respect to the main surface can be formed by partially applying a mask 52 on the main surface in the same manner as in the first embodiment and changing the etching temperature and speed. It became.
[0058]
Then, when the examination was performed using the surface, the same result was obtained. That is, similar to the first embodiment, crystal growth can be performed such that the GaN (1-101) facet surface 70 is substantially parallel to the main surface of the silicon substrate 1, and as a result of continuing such growth, A continuous crystal film having a flat GaN (1-101) facet surface 70 on the surface was obtained.
[0059]
GaN is a crystal having a strong orientation, and in a normal method, c-axis is oriented perpendicular to the main surface, and thus, the obtained crystal has only a C-plane as a main surface and has a different plane from the C-plane. Although it was difficult to obtain a crystal, the present invention has made it easy to obtain a crystal having a GaN (1-101) facet surface 70 on the surface.
[0060]
For example, by forming a stripe-shaped groove extending in the [01-1] direction on the silicon substrate 1 which is 8.6 ° off in the [100] direction from the (2-1-1) plane, the (211) facet surface is formed. A GaN crystal film having a flat surface similar to the above could be obtained as a slope inclined at 62 ° from the main surface. This is because a nitride semiconductor crystal is grown with its c-axis perpendicular to the (211) facet plane, and in this case also, a silicon-off substrate having an angle of 62 ° from the (211) plane. It is considered that a flat GaN substrate can be obtained by using No. 1.
[0061]
As described above, according to the present invention, when the silicon substrate 1 is used, the nitride semiconductor film is liable to undergo c-axis oriented crystal growth with respect to the substrate, and the relationship between the facet surface and the off-angle of the substrate main surface is 62 °. By using a certain substrate, a crystal film having a flat (1-101) facet surface 70 of a nitride semiconductor can be obtained.
[0062]
By forming a semiconductor light emitting element on a nitride semiconductor film formed of a continuous film obtained by growing this crystal film in the same manner as in the first and second embodiments, high brightness and high efficiency on the silicon substrate 1 are obtained. It becomes possible to manufacture the semiconductor light emitting device of the above.
[0063]
In the semiconductor light emitting device thus obtained, the light emitting layer (active layer) has a (1-101) facet surface as a main surface. This is different from an element formed conventionally using a sapphire substrate, a SiC substrate, or a Si (111) substrate, in which the (0001) plane is used as the main surface.
[0064]
A thin film whose main surface is a (0001) plane of a nitride semiconductor which is a wurtzite structure crystal is equivalent in a band structure in a direction parallel to the main surface, but as in the present invention, (1-101) A thin film having a facet surface as a main surface is not equivalent in band structure even in a direction parallel to the main surface. Therefore, the present invention is not limited to this embodiment, and the light-emitting element to which the present invention is applied has a degenerate band in the direction parallel to the light-emitting layer (active layer), and thus has high luminous efficiency. When applied to, a significantly lower threshold value and higher efficiency can be realized.
[0065]
Further, the substrate is not limited to silicon. For example, a semiconductor laser device can be formed in the same manner by using another cubic crystal substrate such as GaAs and setting the plane orientation relationship to the same as in the first embodiment. However, the silicon substrate 1 is relatively stable to the growth atmosphere when growing the nitride semiconductor, and it is easy to keep the growth surface flat during the crystal growth, and it is easy to obtain the effect of the present invention stably. There are advantages. In addition, the material is not limited to the cubic crystal, and any material may be used as the substrate and the shape of the groove may be processed as specified in this specification. However, in the method of forming a groove in the silicon substrate 1 described in the first embodiment and the like, since a so-called facet surface is used as a slope, the flatness and stability to a growth atmosphere when growing a nitride semiconductor are excellent. Therefore, there is an advantage that the effect of the present invention is easily obtained stably.
[0066]
<Embodiment 4>
This embodiment is a modification of the first embodiment. The diameter d of the resonator region of the semiconductor laser of the first embodiment is 3 μm, the reflectivity of the multilayer reflective film 103 is 99%, and the dielectric multilayer reflective film is The reflectance of 111 is set to about 95%. As a result, a short-wavelength semiconductor laser having an oscillation threshold of 0.5 mA and an ultra-low threshold can be realized. In addition, when an operation test was performed at a light output of 5 mW for 1000 hours, there was no change in the polarization direction, and the oscillation was extremely stable. Turned out to be. Thus, a semiconductor laser having an ultra-low threshold value and a stable polarization direction can be realized, and is optimal as a light source for an optical disk system.
[0067]
It is to be noted that the idea of the present embodiment can be combined with the idea of Embodiment 2 or Embodiment 3, and similar results are obtained when applied to each.
[0068]
<Embodiment 5>
This embodiment is a modification of the first embodiment, in which the mesh-like metal electrode 110 of the semiconductor laser of the first embodiment is changed to a flat ITO film, and a dielectric multilayer serving as a reflecting mirror is formed thereon. A film 111 is provided. Other configurations are the same as in the first embodiment.
[0069]
When the semiconductor laser device of the present embodiment was manufactured and the characteristics of the semiconductor laser device were measured, an optical output of 0.6 W was obtained at an operating current of 300 mA. The polarization direction is often the direction of the nitride semiconductor <11-20> constituting the active layer or the like, and depending on the state of strain applied to the active layer, the direction of polarization is perpendicular to the <11-20>. there were. In each case, since the active layer had crystallographic anisotropy in the plane, the polarization direction was stable, and the same effect as in the first embodiment was obtained.
[0070]
Note that this embodiment can also be combined with the technology described in the other embodiments, and similar results are obtained when applied to each of the embodiments.
[0071]
<Embodiment 6>
This embodiment is a modification of the first embodiment, in which the dielectric multilayer film 111 and the metal electrode 110 of the semiconductor laser of the first embodiment are changed to a Pd thin film (thickness: 2 to 10 nm), and the electrode and the reflection are changed. Have a role as a mirror at the same time. Other configurations are the same as in the first embodiment.
[0072]
In the case of the present embodiment, the effect of confining light in the resonator was weak because the reflectance was only 50% or less, and the device operated as a resonant cavity LED when current was injected. When the characteristics of the manufactured LED element were measured, an operating current of 300 mA and an optical output of 0.3 W were obtained. The polarization direction is often the direction of the nitride semiconductor <11-20> constituting the active layer or the like, and depending on the state of strain applied to the active layer, the direction of polarization is perpendicular to the <11-20>. there were. In each case, since the active layer had crystallographic anisotropy in the plane, the polarization direction was stable, and the same effect as in the first embodiment was obtained.
[0073]
Note that this embodiment can also be combined with the technology described in any of the other embodiments, and similar results have been obtained by applying each of them.
[0074]
<Embodiment 7>
FIG. 3 is a schematic sectional view showing the structure of the nitride semiconductor light emitting device of the present embodiment. The semiconductor laser device of the present embodiment is different from that of the first embodiment in that a part of the silicon substrate 1 is removed so that output light is extracted from the substrate side. The point is that a metal electrode 310 made of Ag is used instead of the multilayer reflective film 111. Other configurations are the same as in the first embodiment.
[0075]
With the structure of the present embodiment, the reflectance can be approximately 90%. Further, the silicon substrate 1 under the resonator region is removed, and a hole 320 reaching the mask 52 or the n-GaN layer 102 is formed. Such a hole 320 can be formed by selectively etching only silicon. If a selective etching solution such as a mixed solution of hydrofluoric acid, nitric acid, and acetic acid is used, a mirror surface of n- This is preferable because the GaN layer 102 is exposed.
[0076]
The reflectivity of the multilayer reflective film 103 was set to about 80% or more. Since the semiconductor light emitting device of the present embodiment can be mounted with the metal electrode 310 side fixed to the heat sink, the heat dissipation is extremely high. Therefore, heat generation during high current injection is suppressed, and an extremely high operating current can be realized. When the characteristics of the manufactured semiconductor laser device were measured, an optical output of 1.5 W was obtained at an operating current of 1 A.
[0077]
<Embodiment 8>
This embodiment is a modification of the seventh embodiment, in which the metal electrode 310 made of Ag is replaced with an ITO thin film serving as a transparent electrode and a dielectric multilayer film formed thereon. Other configurations are the same as those of the seventh embodiment.
[0078]
According to the above configuration, it is possible to make the reflectance of the reflecting mirror on the upper surface to be 98% or more, and it is possible to further reduce the oscillation threshold value as compared with the semiconductor laser device of the seventh embodiment.
[0079]
<Embodiment 9>
FIG. 8 is a diagram illustrating the semiconductor light emitting device of the present embodiment. As shown in FIG. 8, the semiconductor light emitting device includes a metal package 801, a semiconductor light emitting element 802, a cap glass 803, and a wavelength conversion material 804.
[0080]
The semiconductor light emitting element (semiconductor laser, LED) 802 is as described in Embodiment Modes 1 to 8, and is mounted on the metal package 801. The package is provided with a cap glass 803 from which an output from the semiconductor light emitting element 802 is taken out. Outside the cap glass 803, a wavelength conversion material (wavelength conversion material) 804 such as a phosphor is formed.
[0081]
In this embodiment mode, the semiconductor light-emitting element 802 is mounted on a metal package and has good heat dissipation, and suppresses light output saturation even when the light-emitting element is driven by a large current of 100 mA or more. Can be.
[0082]
The wavelength conversion material 804 absorbs light emitted from the semiconductor light emitting element 802 and emits light having a different wavelength from the emitted light. Since the wavelength conversion material 804 is formed at a distance from the light emitting element, deterioration due to heat generation of the semiconductor light emitting element 802 and deterioration of the material in a high light density region such as a light extraction portion of the light emitting element are suppressed. It is supposed to be.
[0083]
In this embodiment mode, since the light-emitting element of the above embodiment mode is used, a light-emitting device using a wavelength conversion material with extremely high luminous efficiency can be realized. As the best.
[0084]
As described above, the embodiments of the present invention have been described. However, the embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0085]
【The invention's effect】
According to the present invention, in a so-called vertical cavity semiconductor light emitting device having a resonator in the stacking direction of the active layer and the cladding layer, the plane orientation of the main surface of the active layer is set to (1-101), so that the polarization direction control is performed. It is possible to provide a light emitting element excellent in the above. Further, since the (1-101) plane can be stably obtained by using a predetermined substrate, a semiconductor light emitting device can be realized at a practical level. In addition, the semiconductor light emitting device of the present invention has excellent characteristics such as luminous efficiency and oscillation threshold reduction.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a crystal orientation in a light emitting device of the present invention.
FIG. 2 is a sectional view showing a nitride semiconductor light emitting device (semiconductor laser device) according to the first embodiment of the present invention.
FIG. 3 is a sectional view showing a nitride semiconductor light emitting device (semiconductor laser device) according to a seventh embodiment of the present invention.
FIG. 4 is a view showing a first step of a manufacturing process of the nitride semiconductor light emitting device of the present invention.
FIG. 5 is a view showing a second step in the manufacturing process of the nitride semiconductor light emitting device of the present invention.
FIG. 6 is a view showing a third step of the manufacturing process of the nitride semiconductor light emitting device of the present invention.
FIGS. 7A to 7D are diagrams showing a growth process of a nitride semiconductor film of the present invention.
FIG. 8 is a diagram showing a semiconductor light emitting device of the present invention.
[Explanation of symbols]
1 silicon substrate, 10 n-AlGaInN intermediate layer, 52 mask, 60 main surface ((001) surface of silicon), 61 (111) facet surface, 70, 72 (1-101) facet surface, 102 n-GaN layer, 103,111 multilayer reflective film, 104,107 spacer layer, 105 quantum well active layer, 106 AlGaN cap layer, 108 contact layer, 109,110,310 metal electrode, 320 hole, 801 metal package, 802 semiconductor light emitting element, 803 cap Glass, 804 wavelength conversion material.

Claims (11)

In a semiconductor light emitting device having an active layer containing a nitride semiconductor and a clad layer sandwiching the active layer, and having a resonator in a stacking direction of the active layer and the clad layer, a plane orientation of a main surface of the active layer is (1-101) A semiconductor light-emitting element characterized by the above-mentioned. A semiconductor light-emitting device comprising a substrate and a compound semiconductor layer formed of a nitride semiconductor formed on the substrate,
The substrate has a groove having a surface inclined at 62 degrees from the main surface of the substrate or a surface inclined within 3 degrees in an arbitrary direction from this surface as a slope, and the compound semiconductor layer is formed on the slope. Having an active layer containing a nitride semiconductor and a clad layer sandwiching the active layer on the compound semiconductor layer, and having a resonator in a stacking direction of the active layer and the clad layer, A semiconductor light emitting device, wherein the active layer has a plane orientation substantially coincident with a main surface of the substrate. A semiconductor light emitting device having a silicon substrate and a compound semiconductor layer formed of a nitride semiconductor formed on the silicon substrate,
The compound semiconductor layer is composed of a plane obtained by rotating the (100) plane by 7.3 degrees around the [01-1] axis, or a plane that is inclined within 3 degrees in an arbitrary direction from this plane. It is formed using a silicon substrate having a main surface, the silicon substrate includes a groove having a (111) plane as a slope, and the compound semiconductor layer is formed on the slope and includes a nitride semiconductor. A semiconductor light emitting device comprising: an active layer to be formed; and a clad layer sandwiching the active layer, and a resonator in a direction in which the active layer and the clad layer are stacked. 4. The semiconductor light emitting device according to claim 2, wherein a plane orientation of a main surface of the cladding layer or the active layer is (1-101). 5. 5. The semiconductor light emitting device according to claim 2, wherein a <0001> direction of said compound semiconductor layer is substantially perpendicular to said slope. The semiconductor light emitting device according to claim 2, wherein the groove extends along a [11-20] direction of a nitride semiconductor forming the active layer. The semiconductor light emitting device is a semiconductor laser device,
7. The semiconductor light emitting device according to claim 2, wherein the laser light emitted from the semiconductor laser device is polarized in a direction parallel or perpendicular to the groove. The semiconductor light emitting device according to claim 2, wherein a film that suppresses growth of a nitride semiconductor is formed on at least a part of the surface of the substrate other than the slope. A semiconductor light-emitting device according to claim 1,
A semiconductor light-emitting device, comprising: a wavelength conversion substance that absorbs light emitted from the semiconductor light-emitting element and emits light having a wavelength different from that of the emitted light. A method for manufacturing a semiconductor light emitting device having a lower cladding layer, an active layer, and an upper cladding layer, and having a resonator in a stacking direction thereof,
Forming a groove in the main surface of the substrate, the surface having a surface inclined at 62 degrees from the main surface or a surface inclined within a range of 3 degrees in an arbitrary direction from the surface,
Crystal growing a nitride semiconductor on the slope, forming a compound semiconductor layer having a plane substantially parallel to the main surface of the substrate,
Laminating a lower cladding layer, an active layer, and an upper cladding layer each composed of a nitride semiconductor in this order on the compound semiconductor layer. A method for manufacturing a semiconductor light emitting device having a lower cladding layer, an active layer, and an upper cladding layer, and having a resonator in a stacking direction thereof,
The lower clad layer, the active layer, and the upper clad layer each composed of a nitride semiconductor are laminated in this order on the main surface of the compound semiconductor layer having the (1-101) plane of the nitride-based semiconductor as the main surface. A method for manufacturing a semiconductor light emitting device, comprising the steps of:

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