JP3316479B2 - Semiconductor device, semiconductor light emitting device, and method of manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a group III-V nitride semiconductor such as BN (boron nitride), GaN (gallium nitride), AlN (aluminum nitride) or InN (indium nitride) or a mixed crystal thereof. The present invention relates to a semiconductor element having a compound semiconductor layer made of a nitride semiconductor), a semiconductor light emitting element, a method of manufacturing a semiconductor element, and a method of forming a nitride semiconductor layer.

2. Description of the Related Art In recent years, GaN-based semiconductor light emitting devices have been put to practical use as semiconductor light emitting devices such as light emitting diodes and semiconductor laser devices that emit blue or violet light. When manufacturing a GaN-based semiconductor light-emitting device, sapphire (Al ₂ O ₃ )
Each layer is epitaxially grown on an insulating substrate. FIG. 18 is a sectional view showing the structure of a conventional GaN-based light emitting diode. The light emitting diode of FIG. 18 is disclosed on pages 92 to 93 of Nikkei Microdevice, February, 1994. In FIG. 18, a GaN buffer layer 62, an n-GaN layer 63, an n-A
lGaN cladding layer 64, InGaN light emitting layer 65, p-
An AlGaN cladding layer 66 and a p-GaN layer 67 are sequentially formed. Part of the region from the p-GaN layer 67 to the n-GaN layer 63 has been removed by etching. A p-electrode 68 is formed on the upper surface of the p-GaN layer 67,
An n-electrode 69 is formed on the exposed upper surface of the n-GaN layer 63. Such a structure of the light emitting diode is called a lateral structure. The light emitting diode of FIG.
It has a double hetero structure pn junction in which the GaN light emitting layer 65 is sandwiched between the n-AlGaN cladding layer 64 and the p-AlGaN cladding layer 66, and can emit blue light.

However, FIG.
In a conventional GaN-based semiconductor light emitting device as shown in FIG.
Due to the difference in lattice constant between aN and a sapphire substrate, a GaN-based semiconductor crystal grown on a sapphire substrate usually has about 10 ⁹ / cm ² lattice defects. Such lattice defects propagate from the surface of the sapphire substrate to the GaN-based semiconductor layer. Due to this lattice defect, in the semiconductor light emitting device including the GaN-based semiconductor layer on the sapphire substrate, the device characteristics and the reliability are deteriorated. As a method for solving the problem of deterioration of device characteristics and reliability due to lattice defects, a lateral growth technique has been proposed. This lateral growth technology is, for example, the Proceedings of The Second Interna
national Conference on Nitride Semiconductors, Octob
er27-31, 1997, Tokushima, Japan, pp.444-446. FIG. 19 is a schematic process sectional view for explaining a conventional lateral growth technique. As shown in FIG. 19A, an AlGaN buffer layer 8 is formed on a sapphire substrate 81.
2 and a GaN layer 83 is grown on the AlGaN buffer layer 82. The GaN layer 83 has a lattice defect 91 extending vertically. On this GaN layer 83, a striped SiO ₂ film 90 is formed. Next, FIG.
As shown in (b), the GaN layer 84 is regrown on the GaN layer 83 exposed between the stripe-shaped SiO ₂ films 90. Also in this case, the lattice defects 91 in the vertical direction extend in the regrown GaN layer 84. As shown in FIG.
When the aN layer 84 is further grown, the GaN layer 84 also grows in the lateral direction, and the GaN layer 84 is formed on the SiO ₂ film 90. The GaN layer 84 on the SiO ₂ film 90 has no lattice defects. As shown in FIG. 19 (d), when the GaN layer 84 is further grown, the SiO ₂ film 90 and S
A GaN layer 84 is formed on the GaN layer 83 between the iO ₂ films 90. Using such a lateral growth technique, SiO 2
_A high-quality GaN crystal without lattice defects can be formed on the _two films 90. However, in a region where the SiO ₂ film 90 does not exist, the lattice defect 91 from the underlying GaN layer 83 extends to the surface of the regrown GaN layer 84, so that the lattice defect on the surface of the GaN layer 84 does not disappear. Therefore, when manufacturing a semiconductor light emitting element, it is necessary to limit the light emitting region on the SiO ₂ film. Therefore, the size of the light emitting region cannot be increased. If the area of the SiO ₂ film is increased in order to increase the area of the high-quality GaN layer, the surface of the laterally grown GaN layer cannot be flattened. The conventional Ga shown in FIG.
In the N-based light emitting diode, since the sapphire substrate 61 is an insulating substrate, the n-electrode 69 cannot be provided on the back surface of the sapphire substrate 61, and the n-electrode 69 is formed on the n-GaN layer 6.
3 must be provided on the exposed surface. Therefore, compared to the case where the n-electrode is provided on the back surface of the conductive substrate, the p-electrode 6
The current path between the gate electrode 8 and the n-electrode 69 becomes longer, and the operating voltage becomes higher. Further, when manufacturing a GaN-based semiconductor laser device, it is difficult to form a resonator surface by a cleavage method as in a semiconductor laser device that generates red light or infrared light using a GaAs substrate. FIG. 20 is a diagram showing the relationship between the crystal orientations of the sapphire substrate and the GaN-based semiconductor layer. In FIG. 20, the solid arrow indicates the crystal orientation of the sapphire substrate, and the broken arrow indicates the crystal orientation of the GaN-based semiconductor layer. As shown in FIG. 20, the a-axis and the b-axis of the GaN-based semiconductor layer formed on the sapphire substrate are shifted by 30 degrees from the a-axis and the b-axis of the sapphire substrate. FIG. 20 is a schematic perspective view of a semiconductor laser device including a GaN-based semiconductor layer formed on a sapphire substrate.
In FIG. 21, a GaN-based semiconductor layer 70 is formed on a (001) plane of a sapphire substrate 61. The stripe-shaped current injection region 71 is formed by the <
1 1 -2 0> direction. In this case, GaN
The {1-100} plane of the system semiconductor layer 70 is a sapphire substrate 61
Is inclined by 30 degrees with respect to the {1 -100} plane. Both the sapphire substrate 61 and the GaN-based semiconductor layer 70 are {1 -10
It is easy to cleave in the 0｝ plane. As described above, since the cleavage direction is shifted between the sapphire substrate 61 and the GaN-based semiconductor layer 70, when manufacturing a GaN-based semiconductor laser device,
It becomes difficult to form a cavity surface by a cleavage method like a semiconductor laser device that generates red light or infrared light formed on a GaAs substrate. In this case, it is necessary to form the resonator surface by etching. However,
When the resonator surface is formed by etching, it is difficult to form an end surface perpendicular to the substrate, so that the operating current of the semiconductor laser device cannot be reduced.
On the other hand, various reports and proposals have been made on a method of controlling a transverse mode of a GaN-based semiconductor laser device. Most of these lateral mode control methods are a ridge waveguide structure and a self-aligned structure employed in a conventional semiconductor laser device that generates red light or infrared light.
However, since the GaN-based semiconductor layer is chemically stable,
Unlike conventional AlGaAs-based semiconductor layers used in semiconductor laser devices that generate red light or infrared light, they cannot be patterned by wet etching.
It is necessary to perform patterning by dry etching such as RIE (reactive ion etching) and RIBE (reactive ion beam etching). Therefore, G
In an aN-based semiconductor laser device, patterning for producing a ridge waveguide structure or a self-aligned structure cannot be performed easily and with good reproducibility. In addition, the element characteristics change greatly depending on the accuracy of the dry etching. An object of the present invention is to provide a nitride-based semiconductor device capable of operating at a low voltage. Another object of the present invention is to provide a nitride-based semiconductor light-emitting device that can operate at a low voltage and can form an end face by cleavage. It is still another object of the present invention to provide a method for manufacturing a nitride semiconductor device in which lattice defects are reduced, low voltage operation is possible, and an end face can be formed by cleavage.

According to a first aspect of the present invention, there is provided a semiconductor device comprising: a boron-containing gas having an n-type layer and a p-type layer laminated thereon;
At least one of lithium, aluminum and indium
N-type gallium arsenide group
The nitride-based semiconductor layer is placed on the plate via the first electrode layer.
The second electrode layer is formed on the upper surface of the n-type layer while being joined from the p-type layer side . In the semiconductor device according to the present invention, the first electrode layer and the second electrode layer are provided on the lower surface and the upper surface of the nitride-based semiconductor layer on the n-type gallium arsenide substrate, respectively. The current path between the first electrode layer and the second electrode layer is shortened. Therefore, the operating voltage of the nitride-based semiconductor device can be reduced. The semiconductor light emitting device according to the second invention is an n-type layer
, Gallium, aluminum laminated with p-type layers
Containing at least one of indium and indium
A first electrode having a semiconductor layer on an n-type gallium arsenide substrate;
The nitride-based semiconductor layer extends from the p-type layer side through a layer
At the same time , the second electrode layer is formed on the upper surface of the n-type layer , and the nitride-based semiconductor layer includes a light emitting layer. In the semiconductor light emitting device according to the present invention, n
Since the first electrode layer and the second electrode layer are provided on the lower surface and the upper surface of the nitride-based semiconductor layer on the type gallium arsenide substrate, the first electrode layer and the second electrode layer are provided between the first electrode layer and the second electrode layer. The current path becomes shorter. Therefore, the operating voltage of the nitride semiconductor light emitting device can be reduced. In particular, the nitride-based semiconductor layer has a stripe-shaped current injection region for injecting current into the light-emitting layer, and the stripe-shaped current injection region is formed along the <1-100> direction of the nitride-based semiconductor layer. A nitride-based semiconductor layer disposed on the gallium arsenide substrate such that the <1-100> direction of the nitride-based semiconductor layer coincides with the <110> direction or the <1-110> direction of the gallium arsenide substrate; {110} plane of arsenic substrate or {1-1}
It is preferable that a pair of resonator surfaces be formed by the {0} plane and the {1-100} plane of the nitride-based semiconductor layer. In this case, since the cleavage direction of the nitride-based semiconductor layer matches the cleavage direction of the gallium arsenide substrate, it becomes possible to form the resonator surface by cleavage. As a result, a semiconductor laser device is realized as a semiconductor light emitting device, and variations in device characteristics are reduced, and reproducibility of device characteristics is improved. According to a third aspect of the invention, there is provided a method of manufacturing a semiconductor device,
Forming a first nitride-based semiconductor layer containing at least one of boron, gallium, aluminum and indium on the insulating substrate; and forming an insulating film in a predetermined region on the first nitride-based semiconductor layer Forming a second nitride-based semiconductor layer containing at least one of boron, gallium, aluminum, and indium on the first nitride-based semiconductor layer and the insulating film using a lateral growth technique; Removing the second nitride-based semiconductor layer except for the region on the insulating film; and removing the upper surface of the second nitride-based semiconductor layer on the insulating film from the gallium arsenide substrate via the first electrode layer. A step of bonding to one surface, a step of removing the insulating substrate and the first nitride-based semiconductor layer from the second nitride-based semiconductor layer by removing the insulating film, and an upper surface of the second nitride-based semiconductor layer To the second electrode layer It is obtained and a step of forming. In the method for manufacturing a semiconductor device according to the present invention, the second nitride-based semiconductor layer is formed on the insulating film on the first nitride-based semiconductor layer by using the lateral growth technique. Lattice defects do not propagate from the first nitride-based semiconductor layer to the second nitride-based semiconductor layer. Therefore, a high-quality second nitride-based semiconductor layer having almost no lattice defects can be obtained. Further, since the first electrode layer and the second electrode layer are provided on the lower surface and the upper surface of the second nitride-based semiconductor layer on the gallium arsenide substrate, respectively, the first electrode layer and the second electrode layer are provided.
Current path between the first and second electrode layers becomes shorter. Therefore, the operating voltage can be reduced. Further, when the upper surface of the second nitride-based semiconductor layer is joined to one surface of the gallium arsenide substrate via the first electrode layer, the crystal orientation of the second nitride-based semiconductor layer and the gallium arsenide substrate may be matched. Therefore, the end face of the semiconductor element can be formed by cleavage. Therefore, variation in element characteristics is reduced, and reproducibility of element characteristics is improved. In particular, the step of forming the second nitride-based semiconductor layer may include a step of forming a light emitting layer. Thereby, a semiconductor light emitting device is manufactured as a semiconductor device. In the step of forming the second nitride-based semiconductor layer, the stripe-shaped current injection region for injecting a current into the light-emitting layer is formed by the step <1-1 of the second nitride-based semiconductor layer.
And bonding the upper surface of the second nitride-based semiconductor layer to one surface of the gallium arsenide substrate via the first electrode layer, the step of forming the second nitride-based semiconductor layer along the second nitride-based semiconductor layer. The <110> direction of the gallium arsenide substrate to the <110> direction or the <1-10> direction of the gallium arsenide substrate, and the {110} plane or the {1-10} plane of the gallium arsenide substrate and the second nitride The method may further include a step of forming a pair of resonator surfaces by cleaving the {1-100} plane of the physical semiconductor layer. In this case, since the cleavage direction of the nitride-based semiconductor layer matches the cleavage direction of the gallium arsenide substrate, it becomes possible to form the resonator surface by cleavage. As a result, a semiconductor laser device is realized as a semiconductor light emitting device, and variations in device characteristics are reduced and reproducibility of device characteristics is improved.

1 to 6 are schematic process sectional views showing a method for manufacturing a semiconductor laser device according to a first embodiment of the present invention. First, an AlGaN buffer layer 2 is formed on a sapphire substrate 1 as shown in FIG.
An undoped GaN layer 3 is grown on the aN buffer layer 2. After a SiO ₂ film 4 having a predetermined width is formed on the GaN layer 3, the SiO ₂ film 4 is formed on the GaN layer 3 and the SiO ₂ film 4 using a lateral growth technique.
_{2 An} n-GaN layer 5 is grown on the film 4. Next, nG
On the aN layer 5, a 0.1 μm-thick n-In _P Ga _{1 -P} N
(P = 0.1) crack preventing layer 6, 1.0 μm thick n
-Al _Y Ga ₁ -YN (Y = 0.7) cladding layer 7, a multiple quantum well light emitting layer (hereinafter referred to as MQW light emitting layer)
8, p-Al _Y Ga ₁ -YN (Y = 0.5 μm) having a thickness of 0.15 μm
07) Cladding layer 9 and 0.20 μm thick nA
The _{l Z Ga 1-Z N (} Z = 0.12) current blocking layer 10 are sequentially formed. FIG. 7 is an energy band structure diagram of the MQW light emitting layer 8. As shown in FIG. 7, the MQW light emitting layer 8
Six In _X Ga _{1 -X} N (X = 0.03) quantum barrier layers 81 having a thickness of 60 ° and five In _X Ga _{1 -X} N (X
= 0.10) including a multiple quantum well structure in which quantum well layers 82 are alternately stacked. Both surfaces of the multiple quantum well structure are sandwiched between GaN optical guide layers 83 having a thickness of 0.1 μm. Subsequently, a stripe-shaped region of the _{n-Al Z Ga 1-Z} N width W0 of the center portion of the current blocking layer 10 is removed by etching. In this case, the stripe-shaped region between _{n-Al Z Ga 1-Z} N current blocking layer 10 becomes the current injection region 19. The width W0 of the current injection region 19 is, for example, 2 μm. This current injection region 19 is formed along the <11-20> direction of GaN. _{Furthermore, n-Al Z Ga 1-} Z N current blocking layer 10 and the _{p-Al Y Ga 1-Y} N having a thickness of 0.4μm on the cladding layer _{9 p-Al Y Ga 1-} Y N (Y =
0.07) Cladding layer 11 and 0.1 μm thick p
-GaN contact layer 12 is formed in order. Note that Si is used as the n-type dopant, and Mg is used as the p-type dopant. As a method of growing each layer, for example, MOCVD (metal organic chemical vapor deposition) or HVPE (hydride vapor deposition) is used. In this case, in a region where the SiO ₂ film 4 does not exist, the GaN layer 3
To the p-GaN contact layer 12 in the vertical direction. No lattice defects exist in the n-GaN layer 5 to the p-GaN contact layer 12 on the SiO ₂ film 4. Next, as shown in FIG. 2, the p-GaN contact layer 12 to the n-GaN layer 5 in the region where the SiO ₂ film 4 does not exist.
Are removed by dry etching such as RIE or RIBE. Thereby, the GaN-based semiconductor layer 18 having no lattice defect remains on the GaN layer 3. Further, in order to activate the p-type dopant, at least 600 ° C., for example, 8
After annealing at 00 ° C. for 30 minutes, as shown in FIG.
Of Ni, Pt having a thickness of 100 °, and Au having a thickness of 1 μm. Next, as shown in FIG. 4, the ohmic electrodes 15a and 15
100 μm thick n-GaAs substrate 14 on which b is formed
Prepare The upper surface of the p-electrode 13 formed on the GaN-based semiconductor layer 18 on the sapphire substrate 1 is bonded to the ohmic electrode 15a of the n-GaAs substrate 14 by thermocompression or fusion. When using thermocompression bonding, it is desirable that the surface of the p-electrode 13 and the surface of the ohmic electrode 15a be covered with Au immediately after vapor deposition. When fusion is used, a thickness of 3 μm is formed on the n-GaAs substrate 14.
It is desirable to form an Au—Sn film of about m. When joining the p-electrode 13 and the ohmic electrode 15a, n-
The crystal orientations of the GaAs substrate 14 and the GaN-based semiconductor layer 18 are adjusted so that the GaAs substrate 14 and the GaN-based semiconductor layer 18 have the relationship shown in FIG. In FIG. 8, n-Ga
GaN-based semiconductor layer 18 on the (001) plane of As substrate 14
Is formed. Striped current injection region 19 corresponds to the region between the _{n-Al Z Ga 1-Z} N current blocking layer 10 of FIG. 4, the light emitting portion 20 is formed in the current injection region 19.
This current injection region 19 is provided along the <1-100> direction. In this case, the GaN-based semiconductor layer 1 is arranged such that the current injection region 19 of the GaN-based semiconductor layer 18 is parallel to the <110> direction or the <1-10> direction of the n-GaAs substrate 14.
8 is bonded on the n-GaAs substrate 14. Next, the SiO ₂ film 4 is removed by immersing the sapphire substrate 1 and the n-GaAs substrate 14 of FIG. 4 in a hydrofluoric acid stock solution, and the sapphire substrate 1 and an AlGa having lattice defects thereon are removed.
The N buffer layer 2 and the GaN layer 3 are removed from the GaN-based semiconductor layer 18 on the n-GaAs substrate 14 by a lift-off method. Thereby, as shown in FIG.
GaN-based semiconductor layer 18 having no lattice defect on substrate 14
Remains. In this case, it is desirable to use a hydrofluoric acid stock solution with surface activation so that the side etching of the SiO ₂ film 4 can easily proceed. Finally, as shown in FIG.
Except for the central region on the n-GaN layer 5, the upper surface and side surfaces of the GaN-based semiconductor layer 18 and the ohmic electrode 15
a, a SiO ₂ film 16 for short-circuit prevention is formed on the surface of the n-GaN layer 5 and the SiO ₂ film 16 on the surface of the SiO ₂ film 16.
An n-electrode 17 made of 00Å Ti and 2000Ａｌ Al is formed. Thereafter, a pair of resonator surfaces are formed by a cleavage method. In this case, as shown in FIG.
The {1-100} plane of the system semiconductor layer 18 and the {110} plane or the {1-110} plane of the n-GaAs substrate 14 are cleavage planes. In the semiconductor laser device of this embodiment, GaN
The p-electrode 13 is provided on the back and front surfaces of the
And the formation of the n-electrode 17, the current path between the p-electrode 13 and the n-electrode 17 is shortened. Further, the GaN-based semiconductor layer 18 has almost no lattice defects. Therefore, low-voltage operation and low-current operation can be performed. Also,
Since the cleavage direction of the GaN-based semiconductor layer 18 and the cleavage direction of the n-GaAs substrate 14 can be matched, the resonator surface can be easily formed by the cleavage method.
In this embodiment, the case where the present invention is applied to a semiconductor laser device has been described, but the present invention is also applicable to other semiconductor light emitting devices such as light emitting diodes and other semiconductor devices. 9 and 10 show a first reference of the present invention.
It is a schematic process sectional view showing the formation method of the GaN system semiconductor layer in an example . The sapphire substrate 21 shown in FIG.
Has an (0001) plane (c-plane). FIG. 9B
As shown in FIG. 2, an AlGaN buffer layer 22 and an undoped Ga layer are formed on the (0001) plane of the sapphire substrate 21.
The N layer 23 is grown in order. The GaN layer 23 has a lattice defect 37 extending vertically. Next, as shown in FIG. 9C, the GaN layer 23 is etched by RIE using a stripe mask 29 made of Ni,
A stripe-shaped uneven pattern is formed on the surface of the N layer 23. The width D of each of the concave and convex portions in the concave and convex pattern is, for example, 5 μm. After removing the stripe-shaped mask 29, an SiO ₂ film 30 is formed on the GaN layer 23 as shown in FIG. Next, as shown in FIG. 10E, the SiO ₂ film 30 formed on the side surface of the uneven pattern of the GaN layer 23 is removed by etching. Thereafter, as shown in FIG. 10F, the GaN layer 24 is regrown. At this time, the G
Since the aN layer 23 is exposed, at the start of the regrowth of the GaN layer 24, the GaN layer 24 does not grow in the vertical direction but grows only in the horizontal direction. The GaN layer 24 growing laterally on the SiO ₂ film 30 has lattice defects 37 of the underlying GaN layer 23.
Does not propagate. Then, as shown in FIG.
As the regrowth of the aN layer 24 progresses, the lower SiO ₂ film 30 of the concavo-convex pattern is filled with the GaN layer 24,
The GaN layer 24 grows in the vertical direction. Then, FIG.
As shown in (h), the GaN layer 24 grows horizontally and vertically on the upper SiO ₂ film 30 of the concavo-convex pattern, and the surface of the GaN layer 24 is planarized. As a result, a high-quality GaN layer 24 having no lattice defects is formed on the SiO ₂ film 30 having the concavo-convex pattern. In order to flatten the surface of the GaN layer 24 to be regrown, the GaN layer 24 needs to have a certain thickness. The thickness required to flatten the surface of the GaN layer 24 is determined by the width of the uneven pattern of the underlying GaN layer 23, G
It depends on the growth conditions such as the substrate temperature when growing the aN layer 24. For example, when the width of each of the concave and convex portions of the concave and convex pattern is about 5 μm, the thickness of the GaN layer 24 is 10 to 10 μm.
About 20 μm is required. Since GaN tends to grow in the <1-100> direction, the GaN layer 24 is likely to grow in the lateral direction in the steps of FIGS. 10 (f), (g) and (h). It is desirable to form the striped mask 29 made of Ni in the step (11) along the <11-20> direction perpendicular to the <1-100> direction of the GaN layer 23. Further, in order to make the surface of the GaN layer 24 regrown in the step of FIG. 10H easier to be flat, the mask width and the stripe mask of the Ni stripe mask 29 used in the step of FIG. The window width of 29 (the width of the region where Ni does not exist) is preferably as small as 10 μm or less, and more preferably 1 to 5 μm. Furthermore, it is preferable that the cross-sectional shape of the convex portion of the concavo-convex pattern of the underlying GaN layer 23 be a rectangular shape having a vertical side surface or an inverted mesa shape (an inverted trapezoidal shape), rather than a regular mesa shape (a trapezoidal shape). . As shown in FIG. 11, the cross-sectional shape of the concavo-convex pattern of the GaN layer 23 is made to be an inverted mesa shape, and the SiO ₂ film 3 is formed by a deposition method such as electron beam evaporation having poor step coverage.
By forming 0 on the GaN layer 23, it is possible to prevent the SiO ₂ film from being deposited on the side surfaces of the uneven pattern. Thereby, the step of removing the SiO ₂ film on the side surface of the concavo-convex pattern by etching can be omitted. FIG.
(A), (b) is a schematic cross-sectional view showing a method of forming a concavo-convex pattern of an inverted mesa shape on the surface of the underlying GaN layer 23. First, as shown in FIG.
After the stripe mask 29 made of Ni is formed thereon, the sapphire substrate 21 is inclined and attached to the etching apparatus during dry etching. In this state, the GaN layer 2
3 is etched by dry etching such as RIE. Next, as shown in FIG. 12B, the sapphire substrate 21 is inclined in the opposite direction. In this state, the GaN layer 23 is
Etching is performed by dry etching such as the IE method. In this way, an inverted mesa-shaped uneven pattern can be formed on the surface of the GaN layer 23. According to the method of manufacturing the GaN-based semiconductor layer of the present reference example , even if the sapphire substrate 21 having a different lattice constant from GaN is used,
It is possible to grow a high-quality GaN layer 24 having no lattice defects on the entire surface of the substrate. Therefore, Ga
When a semiconductor light emitting device such as a light emitting diode or a semiconductor laser device made of a GaN-based semiconductor layer is formed on the N layer 24, it is possible to improve the luminous efficiency and the reliability. FIG. 13 is a schematic cross-sectional view showing one example of a semiconductor laser device manufactured on the GaN layer formed by the method of FIGS. In FIG. 13, FIG. 9 and FIG.
0 on the GaN layer 24 formed by the method
N layer 25, n-InGaN crack prevention layer 26, nA
lGaN cladding layer 27, MQW light emitting layer 28 and p-
AlGaN cladding layers 29 are sequentially formed. p-
An n-AlGaN current block layer 31 is formed except for a stripe-shaped region on the AlGaN cladding layer 29. On p-AlGaN cladding layer 29 and n-AlG
On the aN current block layer 31, a p-AlGaN cladding layer 32 and a p-GaN contact layer 33 are sequentially formed. n-GaN from p-GaN contact layer 33
Part of the region up to the layer 25 has been removed by etching. A p-electrode 34 is formed on the p-GaN contact layer 33, and an n-electrode 35 is formed on the exposed surface of the n-GaN layer 25. In the semiconductor laser device of FIG. 13, the n-GaN layer 25 is connected to the p-GaN contact layer 33.
Since the GaN-based semiconductor layer 36 is formed on the GaN layer 24 having no lattice defects, the GaN-based semiconductor layer 36 has almost no lattice defects. Therefore, a semiconductor laser device capable of low-current and low-voltage operation can be obtained.
In the present embodiment, the case where the method for forming a nitride-based semiconductor layer is applied to a semiconductor laser device has been described. However, the method for forming a nitride-based semiconductor layer according to this embodiment is not limited to other semiconductors such as a light emitting diode. The present invention is also applicable to light emitting elements and other semiconductor elements. Note that in the examples of FIG. 9 and FIG.
As shown in (c), when a stripe-shaped uneven pattern is formed on the surface of the GaN layer 23, Ga
Although the GaN layer 23 is etched so that the N layer 23 remains, the sapphire substrate 21 is exposed at the bottom of the concave portion as shown in FIG. 14 and FIG. 15 when forming an uneven pattern on the surface of the GaN layer 23. The GaN layer 23 may be etched to this extent. As shown in FIGS. 14A and 14B, the sapphire substrate 21 is formed in the same manner as in FIGS. 19A and 19B.
An AlGaN buffer layer 22 and an undoped GaN layer 23 are sequentially grown on the (001) plane. In addition,
The thickness of the GaN layer 23 is, for example, about 0.5 μm to 5 μm. Also in this case, the GaN layer 23 has a lattice defect 37 extending vertically. Next, the SiO ₂ film is formed on the entire surface of the GaN layer 23, to form a stripe-shaped mask of photoresist over the SiO ₂ film, as shown in FIG. 14 (c), the SiO ₂ film using hydrofluoric acid Is etched to form a stripe-shaped SiO ₂ film 30. Thereafter, as shown in FIG. 14 (d), SiO ₂ film 3
GaN layer 23 and AlGaN buffer layer 22 are etched by RIE using chlorine gas until the sapphire substrate 21 is exposed,
A stripe-shaped uneven pattern is formed on the surface of the layer 23. The width D of each of the concave and convex portions in the concave and convex pattern is, for example, 5 μm. Thereafter, as shown in FIG. 15E, the GaN layer 24 is regrown. At this time, since the underlying GaN layer 23 is exposed only on the side surfaces of the concavo-convex pattern, at the start of the regrowth of the GaN layer 24, the GaN layer 24 does not grow in the vertical direction but grows only in the horizontal direction. The GaN layer 24 grown laterally on the sapphire substrate 21 has no lattice defects. As shown in FIG.
As the regrowth of the GaN layer 24 proceeds, the recesses of the concavo-convex pattern are filled with the GaN layer 24, and the GaN layer 24 grows in the vertical direction. Thereafter, as shown in FIG. 15 (g), the GaN layer 24 is made of SiO 2 on the upper surface of the projection of the uneven pattern.
_{The two} films 30 grow in the horizontal and vertical directions, and the surface of the GaN layer 24 is planarized. As a result, the high-quality GaN layer 2 having no lattice defects on the SiO ₂ film 30 and the sapphire substrate 21 having the concavo-convex pattern.
4 are formed. 9 and 10, in order to make the surface of the GaN layer 24 to be regrown flat,
It is necessary that the aN layer 24 has a certain thickness. The thickness required to make the surface of the GaN layer 24 flat depends on the growth conditions such as the width of the uneven pattern of the underlying GaN layer 23 and the substrate temperature during the growth of the GaN layer 24.
For example, when the width of each of the concave and convex portions of the concavo-convex pattern is 5 μm, the thickness of the GaN layer 24 needs to be about 10 to 20 μm. Further, since GaN easily grows in the <1-100> direction, the GaN layer 24 tends to grow in the lateral direction in the steps of FIGS. 15 (e), (f) and (g). In the step of FIG. 14C, the stripe-shaped SiO ₂ film 3 is formed.
0 is <1 1 −2> perpendicular to the <1 −100> direction of the GaN layer 23.
It is desirable to form along the 0> direction. Further, since the surface of the GaN layer 24 regrown in the step of FIG. 15 (g) tends to be flat, the width of the stripe-shaped SiO ₂ film 30 formed in the step of FIG. it is preferred window width of the SiO ₂ film (the SiO ₂ film width of the area does not exist) is small and each 10μm or less,
More preferably, the thickness is 1 to 5 μm or less. Also, Ga
Similar to the examples of FIGS. 9 and 10, the cross-sectional shape of the convex portion of the concave-convex pattern of the N layer 23 is preferably a rectangular shape having a vertical side surface or an inverted mesa shape rather than a normal mesa shape. Although the sapphire substrate 21 is used as the insulating substrate in the examples of FIGS. 14 and 15, another insulating substrate such as a spinel substrate can be used instead of the sapphire substrate 21. 16 and 17 show a second embodiment of the present invention.
It is a typical process sectional view showing the manufacturing method of the semiconductor laser element in a reference example . First, as shown in FIG. 16A, a thickness of 3 is formed on the (0001) plane of the sapphire substrate 41.
0 ° AlGaN buffer layer 42, 2 μm thick undoped GaN layer 43 and 3 μm thick Si doped n
Growing the GaN layer 44a in order; Next, FIG.
As shown in (b), a thickness of about 1 is formed on the n-GaN layer 44a.
After forming the SiO ₂ film 000A, patterning the SiO ₂ film in the region corresponding to the light emitting unit to remove the SiO ₂ film in the region except the light-emitting portion by etching in a stripe shape, a plurality of stripe-shaped SiO ₂ film 45 is formed. In this case, in the next step, a striped SiO ₂ film 45 is formed along the <1-120> direction of the n-GaN layer 44a so that GaN easily grows in the lateral direction. The width of each striped SiO ₂ film 45 is about 0.5 μm, and the pitch of the striped SiO ₂ films 45 is about 1 μm. In order to realize the fundamental transverse mode oscillation, it is preferable that the width W1 of the light emitting portion is about 2 to 5 μm, and the number of the striped SiO ₂ films 45 is about 3 to 5.
Thereafter, as shown in FIG. 16C, the n-GaN layer 44
a-doped n-GaN layer 44 having a thickness of 5 μm
b, 0.1 μm thick Si-doped n-InGaN anti-crack layer 46 and 1 μm thick Si-doped nA
The lGaN cladding layer 47 is grown in order. Furthermore, n
-MQW light emitting layer 48 having the structure shown in FIG. 7 on AlGaN cladding layer 47, Mg-doped p having a thickness of 1 μm
An AlGaN cladding layer 49 and a 0.1 μm thick M
A g-doped p-GaN contact layer 50 is grown in order. In this case, in the region where the stripe-shaped SiO ₂ film 45 is present, the base between the stripe-shaped SiO ₂ film 45 n-
After GaN grows in the vertical direction from the GaN layer 44a, GaN grows in the horizontal direction on the striped SiO ₂ film 45. On the other hand, in the region where the stripe-shaped SiO ₂ film 45 does not exist, the GaN is vertically extended from the underlying n-GaN layer 44a.
Grows. Thereby, the striped SiO ₂ film 45 is formed.
There is a substantial difference in the growth rate of GaN between the region where GaN exists and the region where the striped SiO ₂ film 45 does not exist. That is, in the region where the stripe-shaped SiO ₂ film 45 is present, the growth rate of GaN becomes substantially slower than the region where the stripe-shaped SiO ₂ film 45 is not present. This difference in the growth rate continues until the stripe-shaped SiO ₂ film 45 is completely filled with GaN and the lateral growth is completed. As a result, the surface of the n-GaN layer 44b is formed in a concave shape, and the n-InGaN crack prevention layers 46, n-
AlGaN cladding layer 47, MQW light emitting layer 48, p-A
The lGaN cladding layer 49 and the p-GaN contact layer 50 are formed in a concave shape. The concave portion of the MQW light emitting layer 48 becomes a light emitting portion which is an active region of the device. The GaN-based semiconductor layer 56 on the region where the stripe-shaped SiO ₂ film 45 exists has almost no crystal defects. afterwards,
As shown in FIG. 17D, the p-GaN contact layer 5
A part of the region from 0 to the n-GaN layer 44b is removed by etching to expose the n-GaN layer 44a. Further, as shown in FIG. 17E, except for the upper region of the light emitting portion and the electrode forming region of the n-GaN layer 44a, p-type current confinement and protection of the exposed portion of the pn junction are performed. An SiO ₂ film 51 is formed on the upper and side surfaces of the GaN contact layer 50 and on the upper surface of the n-GaN layer 44a. Finally, as shown in FIG. 17F, a p-electrode 52 is formed on the exposed surface of the p-GaN contact layer 50,
An n-electrode 53 is formed on the exposed surface of the n-GaN layer 44a. It is preferable that the width W2 of the window of the SiO ₂ film 51 to be a current injection region is equal to or slightly smaller than the width W1 of the light emitting unit so that current is injected into the light emitting unit without waste. . According to the method of manufacturing the semiconductor laser device of the present reference example , the crystallinity of the GaN-based semiconductor layer 56 on the region where the stripe-shaped SiO ₂ film 45 exists is improved, and the growth rate generated during the lateral growth of GaN. The MQW light-emitting layer 8 in the light-emitting portion is formed in a concave shape due to the difference.
Thereby, a refractive index difference appears not only in the vertical direction of the sapphire substrate 41 but also in the horizontal direction. As a result, the refractive index waveguide structure can be easily manufactured by performing the crystal growth twice without performing the etching step. Therefore, a semiconductor laser device of a refractive index guided type with no variation in device characteristics and high reproducibility is realized. In this reference example has described the case of applying the present invention to a semiconductor laser device, the present invention is, or other semiconductor light emitting devices such as light emitting diodes, is also applicable to other semiconductor devices. The second
In the reference example , the semiconductor laser device using the sapphire substrate 41 has been described. However, other substrates such as a SiC substrate and a spinel (MgAl ₂ O ₄ ) substrate can be used instead of the sapphire substrate 41. It should be noted that the first implementation
For example, in the first and second reference examples , the SiO ₂ films 4, 30, and 45 are used as insulating films for performing the lateral growth technique, but instead of the SiO ₂ film, an Al ₂ O ₃ film, TiO ₂ Another insulating film such as _two films may be used.

According to the present invention, it is possible to provide a nitride semiconductor device capable of operating at a low voltage. Further, according to the present invention, it is possible to provide a nitride-based semiconductor light-emitting device capable of operating at a low voltage and forming an end face by cleavage. Further, according to the present invention, it is possible to provide a method of manufacturing a nitride-based semiconductor device in which lattice defects are reduced, low-voltage operation is possible, and an end face can be formed by cleavage.

[Brief description of the drawings]

FIG. 1 is a schematic process sectional view showing a method for manufacturing a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a schematic process sectional view illustrating a method for manufacturing a semiconductor laser device according to a first embodiment of the present invention.

FIG. 3 is a schematic process sectional view illustrating a method for manufacturing a semiconductor laser device according to the first embodiment of the present invention.

FIG. 4 is a schematic process sectional view illustrating the method for manufacturing the semiconductor laser device according to the first embodiment of the present invention.

FIG. 5 is a schematic process sectional view illustrating the method for manufacturing the semiconductor laser device according to the first embodiment of the present invention.

FIG. 6 is a schematic process sectional view illustrating the method for manufacturing the semiconductor laser device according to the first embodiment of the present invention.

7 is an MQW in the semiconductor laser device of FIGS. 1 to 6;
FIG. 4 is an energy band structure diagram of a light emitting layer.

FIG. 8 is a perspective view showing a relationship between crystal orientations of a sapphire substrate and a GaN-based semiconductor layer in the semiconductor laser devices of FIGS. 1 to 6;

FIG. 9 is a schematic process sectional view illustrating a method of forming a GaN-based semiconductor layer in the first reference example of the present invention.

FIG. 10 is a schematic process sectional view illustrating a method of forming a GaN-based semiconductor layer in the first reference example of the present invention.

FIG. 11 is a schematic cross-sectional view showing an inverted mesa-shaped concavo-convex pattern formed on the surface of a GaN layer.

FIG. 12 is a schematic cross-sectional view showing a method of forming an inverted mesa-shaped uneven pattern on the surface of a GaN layer.

FIG. 13 shows G formed by the method of FIGS. 9 and 10;
FIG. 4 is a schematic cross-sectional view illustrating an example of a semiconductor laser device manufactured on an aN layer.

FIG. 14 is a schematic process sectional view illustrating another example of the method of forming the GaN-based semiconductor layer.

FIG. 15 is a schematic process sectional view illustrating another example of the method of forming the GaN-based semiconductor layer.

FIG. 16 is a schematic process sectional view illustrating the method for manufacturing the semiconductor laser device according to the second reference example of the present invention.

FIG. 17 is a schematic process sectional view illustrating the method for manufacturing the semiconductor laser device in the second reference example of the present invention.

FIG. 18 is a schematic sectional view of a conventional GaN-based light emitting diode.

FIG. 19 is a schematic process sectional view showing a method of forming a GaN-based semiconductor layer using a conventional lateral growth technique.

FIG. 20 shows a sapphire substrate and G formed thereon.
FIG. 3 is a diagram illustrating a relationship between crystal orientations of an aN-based semiconductor layer.

FIG. 21 shows a sapphire substrate and G formed thereon.
It is a perspective view which shows the relationship of the crystal orientation of an aN-type semiconductor layer.

[Explanation of symbols]

1,21,41 Sapphire substrate 2,22,42 AlGaN buffer layer 3,23,24,43 GaN layer 4,16,30,45,51 SiO ₂ film 5,25,44a, 44b n-GaN layer 7 n- Al _Y Ga _1-Y n cladding layer 8, 28, 48 MQW light emitting layer 9, 11 p-Al _Y Ga _1-Y n cladding layer 12,33,50 p-GaN contact layer 14 n-GaAs substrate 27, 47 n -AlGaN cladding layer 29,32,49 p-AlGaN cladding layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-129984 (JP, A) JP-A-9-8403 (JP, A) JP-A-10-41586 (JP, A) JP-A 8- 274411 (JP, A) JP-A-9-307188 (JP, A) WO 97/11518 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/00-5 / 50 H01L 33/00 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A hoe in which an n-type layer and a p-type layer are stacked.
Low in elemental, gallium, aluminum and indium
N-type gallium having a nitride-based semiconductor layer including at least one
The nitride-based semiconductor on an arsenic substrate via a first electrode layer;
The layer is joined from the p-type layer side and the n-type
A second electrode layer formed on an upper surface of the first layer. 2. A hoe in which an n-type layer and a p-type layer are stacked.
Low in elemental, gallium, aluminum and indium
N-type gallium having a nitride-based semiconductor layer including at least one
The nitride-based semiconductor on an arsenic substrate via a first electrode layer;
The layer is joined from the p-type layer side and the n-type
A second electrode layer is formed on an upper surface of the layer , and the nitride-based semiconductor layer includes a light-emitting layer. 3. The nitride-based semiconductor layer has a stripe-shaped current injection region for injecting a current into the light-emitting layer, and the stripe-shaped current injection region is <1-100> of the nitride-based semiconductor layer. And the <1-100> direction of the nitride-based semiconductor layer coincides with the <110> direction or the <1-110> direction of the gallium arsenide substrate. The {110} plane or {1} of the gallium arsenide substrate is disposed on the gallium arsenide substrate.
3. The semiconductor light emitting device according to claim 2, wherein a pair of resonator surfaces are formed on the {-10} plane and the {1-100} plane of the nitride-based semiconductor layer. 4. A method according to claim 1, wherein the first substrate includes at least one of boron, gallium, aluminum and indium on the insulating substrate.
Forming a nitride-based semiconductor layer, forming an insulating film in a predetermined region on the first nitride-based semiconductor layer, and forming the insulating film on the first nitride-based semiconductor layer and the insulating film. Forming a second nitride-based semiconductor layer containing at least one of gallium, aluminum and indium by using a lateral growth technique; and excluding a region on the insulating film, the second nitride-based semiconductor layer Removing the insulating film; bonding the upper surface of the second nitride-based semiconductor layer on the insulating film to one surface of a gallium arsenide substrate via a first electrode layer; and removing the insulating film. Removing the insulating substrate and the first nitride-based semiconductor layer from the second nitride-based semiconductor layer; and forming a second electrode layer on an upper surface of the second nitride-based semiconductor layer. And a semi-conductor comprising: Manufacturing method for the device. 5. The method according to claim 4, wherein the step of forming the second nitride-based semiconductor layer includes a step of forming a light-emitting layer. 6. The step of forming the second nitride-based semiconductor layer includes forming a stripe-shaped current injection region for injecting a current into the light-emitting layer with <1-10 of the second nitride-based semiconductor layer.
0>, wherein the step of bonding the upper surface of the second nitride-based semiconductor layer to one surface of a gallium arsenide substrate via a first electrode layer includes the step of forming the second nitride-based semiconductor layer. Including the step of matching the <1-100> direction of the semiconductor layer with the <110> direction or the <1-110> direction of the gallium arsenide substrate, wherein the {110} plane or {1-110} of the gallium arsenide substrate is included.
6. The method of manufacturing a semiconductor device according to claim 5, further comprising a step of forming a pair of resonator surfaces by cleaving a surface and a {1-100} surface of the second nitride-based semiconductor layer. Method.