JP3602932B2 - Semiconductor laser diode and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor laser diode capable of emitting light in a short wavelength side in a visible region, particularly in a blue region to an ultraviolet region.
[0002]
[Prior art]
2. Description of the Related Art A semiconductor laser diode is used for various purposes as a light emitting element, and there is a structure in which a laser element composed of a semiconductor multiple layer is formed on a surface of a single crystal sapphire plate.
[0003]
As shown in FIG. 1, a semiconductor laser diode is formed by forming a semiconductor multi-layer 3 forming a laser element on the surface of a single-crystal sapphire plate 1 via a buffer layer 2 as shown in FIG. In this semiconductor laser diode, the oscillation efficiency of the laser can be improved by making the back end faces 3a and 3a forming the resonator of the laser light smooth and increasing the parallelism.
[0004]
As a method of manufacturing this semiconductor laser diode, Japanese Patent Application Laid-Open No. 7-297495 discloses a method of forming a multi-layer 3 on the A-plane (11-20) of a single-crystal sapphire substrate, and then moving the single-crystal sapphire substrate to the C-axis <0001>. It has been proposed to cleave along and divide the multi-layer 3 so that the back end faces 3a, 3a of the multi-layer 3 are precise mirror surfaces to improve the oscillation efficiency of the semiconductor laser diode.
[0005]
[Problems to be solved by the invention]
However, when the single crystal sapphire is cleaved along the C-axis as shown in the above-mentioned JP-A-7-297495, a stable cleavage plane cannot be obtained, and as a result, the surface accuracy of the facing end faces 3a, 3a of the multi-layer 3 is not obtained. However, since the degree of parallelism cannot be increased, a laser diode with good yield and high oscillation efficiency cannot be obtained.
[0006]
Therefore, the present invention improves the accuracy of the cleavage plane of sapphire, thereby improving the parallelism and surface accuracy of the back-facing end faces of the multiple layers constituting the resonator to a favorable state, and improving the laser oscillation efficiency. It is an object to obtain a semiconductor laser diode with good yield.
[0007]
[Means for Solving the Problems]
In view of the above-described problems, the present invention provides a laser device on a single-crystal sapphire plate, which is a step-like divided surface whose end surface is inclined in a direction inclined from the R-plane, on the A-plane or the C-plane. A multi-layer of a gallium nitride-based compound semiconductor to be formed, and two end faces forming a resonator of laser light in the multi-layer are tilted from the C plane of the single crystal sapphire plate by 59.5 to 60.5 ° and from the R plane. It is characterized by being composed of cleavages inclined at 2.5 to 3.5 °.
In addition, the end face is divided in a direction inclined from the R plane, and a single crystal sapphire plate having a stepwise division plane is used as a principal plane, the A plane or the C plane as a main surface. After the formation of the multilayer, grooves are formed in the single crystal sapphire substrate in a direction inclined from the C plane of the sapphire by 59.5 to 60.5 ° and inclined by 2.5 to 3.5 ° from the R plane. And a step of dividing into a large number along the groove.
[0008]
Further, the single-crystal sapphire substrate having the A-plane as the main surface and the multi-layer having the C-plane are tilted by 59.5 to 60.5 ° from the C-plane of sapphire and 2.5 to 3.5 ° from the R-plane. The method is characterized in that a groove is formed in an inclined direction, and a step of dividing the groove into a large number along the groove is provided.
[0009]
[Action]
Generally, the cleavage plane of the gallium nitride-based compound semiconductor and the R plane of single crystal sapphire are inclined by 2.5 to 3.5 °. Therefore, according to the present invention, after forming the multiple layers of the semiconductor, the single crystal sapphire substrate is tilted by 59.5 to 60.5 ° from the C plane and by 2.5 to 3.5 ° from the R plane. , This direction coincides with the cleavage plane of the gallium nitride-based compound semiconductor, so that the divided plane can be made a smooth plane. For this reason, if this division surface is the back end face forming the resonator, the laser oscillation efficiency of the semiconductor laser diode can be improved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The following as an embodiment of the present invention, a gallium nitride-based compound of the active layer heterojunction structure than its band gap to double sandwiched between a layer having a wider band gap semiconductor _{((Al x Ga 1-x} ) y In _1-y N: 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) will be described.
[0011]
As shown in a perspective view in FIG. 1 and a sectional view in FIG. 2, the semiconductor laser diode of the present invention includes a buffer layer 2 made of an AlN layer on a main surface 11 of a single-crystal sapphire plate 1. On top of this is provided a semiconductor multilayer 3 forming a laser element.
[0012]
The multi-layer 3 is provided on an n ⁺ layer 31 made of a Si-doped n-type GaN layer provided on the entire surface of the buffer layer 2, an electrode 41 provided on the n ⁺ layer 31, and a portion other than the electrode 41. An n layer 32 composed of a Si-doped Al _0.1 Ga _0.9 N layer, an active layer 33 composed of a silicon-doped GaN layer, and a p-layer 34 composed of a magnesium-doped Al _0.1 Ga _0.9 N layer; a SiO ₂ layer 35 which covers and is configured from an electrode 42 provided in the window portion of the SiO ₂ layer 35.
[0013]
Then, as shown in FIG. 1, both end faces 12, 12 of the single crystal sapphire plate 1 facing the rear face are inclined by 59.5 to 60.5 ° from the C plane, and inclined by 2.5 to 3.5 ° from the R plane. And the rear facing end faces 3a, 3a of the multi-layer 3 are coplanar with the end faces 12, 12, respectively.
[0014]
Further, as will be described in detail later, the semiconductor laser diode of the present invention, after forming the multi-layer 3 on the single crystal sapphire substrate, is tilted by 59.5 to 60.5 ° from the C plane and 2. By dividing along the direction inclined by 5 to 3.5 °, it is possible to manufacture efficiently.
[0015]
At this time, as shown in the schematic diagram of FIG. 3, the single crystal sapphire plate 1 is divided along a direction inclined from the R-plane, so that the divided surface 12 has a minute step shape. However, since the cleavage plane of the gallium nitride-based compound semiconductor exactly coincides with the above-described division direction, the back-facing end faces 3a, 3a of the multi-layer 3 can be extremely smooth and highly parallel. As a result, when a voltage is applied between the two electrodes 41 and 42 to oscillate the laser light, a resonator is formed between the rear facing end faces 3a and 3a, so that the oscillation efficiency of the laser light can be improved. .
[0016]
Hereinafter, a method for manufacturing the semiconductor laser diode shown in FIGS.
[0017]
First, as shown in FIG. 5, a single-crystal sapphire substrate 10 whose main surface 11 is A-plane (11-20) is prepared.
[0018]
Here, the crystal structure of the single crystal sapphire is hexagonal as shown in FIG. 4, and has a C-axis forming a central axis thereof and a C-plane (0001) perpendicular thereto, and A extending radially from the C-axis in three directions. axis _{(a 1} axis, _{a 2} axis, _{a 3-axis)} perpendicular a plane, respectively (11-20), the vertical axis R R surface (1-102) to have a constant angle to the C axis Exists. That is, as shown in FIG. 5, in the case of the single crystal sapphire substrate 10 having the main surface 11 as the A surface, the R surface exists as a cross section perpendicular to the main surface 11. The directions of these planes and axes can be analyzed by X-ray diffraction.
[0019]
After the single crystal sapphire substrate 10 is organically washed, it is set in a crystal growth unit of a crystal growth apparatus. After evacuating the inside of the apparatus, hydrogen is supplied, and the temperature is raised to about 1200 ° C. in a hydrogen atmosphere to remove the hydrocarbon-based gas attached to the surface of the single crystal sapphire substrate 10.
[0020]
Next, the temperature of the single-crystal sapphire substrate 10 is lowered to about 600 ° C., trimethylaluminum (TMA) and ammonia (NH ₃ ) are supplied, and an AlN layer is grown on the substrate to a thickness of about 50 nm to form a buffer layer. Let it be 2. Next, only the supply of TMA is stopped, the temperature of the substrate is raised to 1040 ° C., trimethylgallium (TMG) and silane (SiH ₄ ) are supplied, and the n ⁺ layer 31 composed of the Si-doped n-type GaN layer is grown. .
[0021]
Once the single crystal sapphire substrate 10 is taken out of the growth furnace, a part of the surface of the n ⁺ layer 31 is masked with SiO ₂ , returned to the growth furnace again, evacuated and supplied with hydrogen and NH ₃ , and Heat to ° C. Next, TMA, TMG and SiH ₄ are supplied, and a 0.5 μm-thick Si-doped Al _0.1 Ga _0.9 N layer is formed on a portion not masked with SiO ₂ to form an n layer 32. .
[0022]
Next, TMG and SiH ₄ are supplied, and a silicon-doped GaN layer having a thickness of 0.2 μm is formed to form an active layer 33. Next, TMA, TMG, and Cp ₂ Mg (biscyclopentadienyl magnesium) are supplied to form a 0.5 μm-thick magnesium-doped Al _0.1 Ga _0.9 N p-layer 34.
[0023]
Next, after removing SiO ₂ used as a mask with a hydrofluoric acid-based etchant and depositing an SiO ₂ layer 35 on the p-layer 34, a rectangular window of 1 mm long and 80 μm wide was opened and transferred to a vacuum chamber. The p-layer 34 is irradiated with an electron beam. By this electron beam irradiation, the p layer 34 showed p conduction.
[0024]
Next, metal electrodes 41 and 42 are formed on the portion corresponding to the window of the p layer 34 and on the n ⁺ layer 31, respectively.
[0025]
A large number of multiple layers 3 forming the above laser element are formed on one single crystal sapphire substrate 10. Then, by dividing the single crystal sapphire substrate 10 and the multilayer 3 at the same time, individual semiconductor laser diodes shown in FIGS. 1 and 2 can be obtained.
[0026]
When performing this division, the back facing end faces 3a, 3a of the multi-layer 3 and the end faces 12, 12 of the single crystal sapphire plate 1 are inclined from the C plane by 59.5 to 60.5 ° as shown in FIG. And it is divided along the direction (two-dot chain line) inclined by 2.5 to 3.5 ° from the R surface, and the other end surface is cut by a diamond cutter or the like to be divided.
[0027]
In addition, the method of dividing in the above-described direction is as follows. A crack line is drawn on the surface of the single-crystal sapphire substrate 10 along the above-mentioned direction by a diamond pen, and a pre-stress is applied in a direction in which the crack line is expanded, so that the crack line grows. , Can be split. Alternatively, division may be performed by inducing thermal stress in a cleavage direction by a laser beam or a heating wire (including a heating wire such as a nichrome wire). Alternatively, a groove having a depth of 10 to 200 μm may be formed on the back surface of the single-crystal sapphire substrate 10 and divided along the groove.
[0028]
In this manner, by dividing along the direction inclined at 59.5 to 60.5 ° from the C plane and at 2.5 to 3.5 ° from the R plane, the back of the multilayer 3 forming the semiconductor laser diode is formed. The end faces 3a, 3a just coincide with the cleavage plane of the gallium nitride compound, and can be extremely smooth and highly parallel. As a result, a semiconductor laser diode with high oscillation efficiency can be obtained.
[0029]
Actually, the main surface 11 of the single-crystal sapphire substrate 10 having a thickness of 225 to 275 μm is defined as an A-plane, and GaN is grown on the main surface 11. When divided along a direction inclined by 5 ° and inclined by 2.5 to 3.5 ° from the R plane, it can be easily divided, and the opposing single surfaces 3a, 3a of the multilayer 3 are extremely smooth and highly parallel surfaces. And could be. However, if this substrate is divided in a direction other than the above, it is difficult to divide the substrate with high accuracy, and it is extremely difficult to obtain cleavage planes in parallel.
[0030]
Note that the main surface 11 of the sapphire substrate 10 does not necessarily need to be the A surface. For example, as shown in FIG. 7, the main surface 11 may be a C surface. In this case, the R plane is not perpendicular to the main surface 11 but has an angle of about 57.62 °, but is also tilted 59.5 to 60.5 ° from the C plane and 2.5 to 2.5 ° from the R plane. By dividing along the direction inclined by 3.5 °, division can be easily performed, and the opposing single surfaces 3a, 3a of the multi-layer 3 can be made smooth surfaces.
[0031]
Further, the main surface 11 may be a surface other than the A-plane and the C-plane, and in any case, the GaN crystal direction was not affected.
[0032]
Further, the sapphire substrate 10 can be obtained by various growing methods. By growing the sapphire substrate 10 by the EFG method, it is possible to easily obtain a substrate in which a cleavage plane is efficiently set.
[0033]
For example, the single-crystal sapphire substrate 10 shown in FIG. 8 is a disk-shaped substrate having an orientation flat forming a reference plane 10a in a part of the periphery, and forming the reference plane 10a perpendicular or parallel to the R plane. is there. Further, the single-crystal sapphire substrate 1 shown in FIG. 9 is rectangular, and has one reference plane 10a formed parallel to the R plane and the other reference plane 10b formed perpendicular to the R plane.
[0034]
By forming the reference planes 10a and 10b perpendicular or parallel to the R plane in this manner, the direction of the R plane can be identified, and the area of the substrate can be maximized when dividing. Can be.
[0035]
【The invention's effect】
As described above, according to the present invention, in a semiconductor laser diode including a multi-layer of a gallium nitride-based compound semiconductor forming a laser element on a main surface of a single-crystal sapphire plate, a resonator of laser light in the multi-layer is formed. The two back-facing end faces are formed of cleavage planes along a direction inclined from the C plane of the single crystal sapphire plate by 59.5 to 60.5 ° and inclined by 2.5 to 3.5 ° from the R plane. As a result, the surface accuracy and parallelism of the rear facing end surface of the multilayer can be increased, and the laser oscillation efficiency can be improved.
[0036]
Further, according to the present invention, after forming a multi-layer of a semiconductor constituting a laser element on a single-crystal sapphire substrate, the single-crystal sapphire substrate and the multi-layer are separated from the C-plane of sapphire by 59.5 to 60.5. By manufacturing a semiconductor laser diode from a process of dividing into a plurality of pieces along a direction inclined at an angle of 2.5 to 3.5 from the R plane, a high performance semiconductor laser diode can be manufactured in an extremely simple process. Can be manufactured.
[0037]
According to the present invention, it is possible to obtain a high-performance semiconductor laser diode capable of emitting light in the short wavelength side in the visible region, particularly in the blue region to the ultraviolet region.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a semiconductor laser diode of the present invention.
FIG. 2 is a sectional view taken along line XX in FIG.
FIG. 3 is a schematic view showing an end face of the semiconductor laser diode of the present invention.
FIG. 4 is a diagram showing a basic crystal structure of single crystal sapphire.
FIG. 5 is a perspective view showing a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention.
FIG. 6 is a perspective view showing a dividing direction when manufacturing the semiconductor laser diode of the present invention.
FIG. 7 is a perspective view showing a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention.
8A and 8B show a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention, wherein FIG. 8A is a plan view and FIG. 8B is a side view.
9A and 9B show a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention, wherein FIG. 9A is a plan view and FIG. 9B is a side view.
[Explanation of symbols]
1: Single crystal sapphire plate 11: Main surface 12: End surface 2: Buffer layer 3: Multilayer 3a: Backward end surface 10: Single crystal sapphire substrate

Claims (2)

A single layer of a single crystal sapphire plate, which is a step-like divided surface in which the end surface is divided in a direction inclined from the R surface, has a main surface of the A surface or the C surface, and a multi-layer of a gallium nitride-based compound semiconductor forming a laser element is formed. The two end faces forming the resonator of the laser beam in the multi-layer are inclined by 59.5 to 60.5 ° from the C plane of the single crystal sapphire plate and inclined by 2.5 to 3.5 ° from the R plane. A semiconductor laser diode comprising cleavage. The end face is divided in a direction inclined from the R plane, and a multi-layer of a gallium nitride-based compound semiconductor forming a laser element is formed on the main plane of the A plane or the C plane of the single crystal sapphire plate having a stepped division plane. After the formation, a groove is formed in the single crystal sapphire substrate in a direction inclined at 59.5 to 60.5 ° from the C plane of sapphire and at an angle of 2.5 to 3.5 ° from the R plane. A method for manufacturing a semiconductor laser diode, comprising a step of dividing into a plurality of pieces along a groove.

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