JP2003069075A - Gallium nitride compound semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium nitride compound semiconductor light emitting device which is improved in external quantum efficiency by restraining optical interference caused by multiple reflection of light occurring inside a gallium nitride compound semiconductor. SOLUTION: A gallium nitride compound semiconductor is grown on a sapphire substrate, the sapphire substrate is removed by polishing or separating, and the rear of the gallium nitride compound semiconductor is turned to a non-mirror surface by etching for the formation of a gallium nitride compound semiconductor light emitting device. The sapphire substrate is removed, by which optical interference generated at the interface due to a refractive index difference between sapphire and gallium nitride can be eliminated. Furthermore, the surface of the gallium nitride compound semiconductor is turned to a non- mirror surface, by which the light is irregularly reflected at the surface, and therefore this light emitting device can be improved in output with a synergistic effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride compound semiconductor in which a gallium nitride-based compound semiconductor represented by the general formula InXAlYGa1-X-YN (0≤X <1, 0≤Y <1) is laminated on a sapphire substrate. The present invention relates to a gallium nitride-based compound semiconductor device obtained by removing a sapphire substrate from a compound-based semiconductor device.

[0002]

2. Description of the Related Art GaN, GaAlN, InGaN, In
A gallium nitride-based compound semiconductor such as AlGaN has a direct transition, its band gap changes from 1.95 eV to 6 eV, and its emission color ranges from ultraviolet to red. Therefore, a material for a light emitting element such as a light emitting diode or a laser diode. Is seen as promising. The light emitting device made of the gallium nitride compound semiconductor is generally MOCVD, MBE, HV.
After growing into n-type and p-type or i-type on a sapphire substrate using a vapor phase growth method such as PE method and stacking them, the electrode is taken out from the layer where the electrode is to be formed, and then formed into a chip-like lead frame. It is obtained by fixing and finally sealing with a resin such as epoxy.

However, since the gallium nitride-based compound semiconductor element has a so-called heteroepitaxial structure in which a completely different material called a gallium nitride-based compound semiconductor is laminated on the sapphire substrate as described above, other GaAs, GaP, etc. The external quantum efficiency is deteriorated due to the difference in refractive index between the substrate and the epitaxial film, as compared with a light emitting device laminated on the same material. Specifically, due to the difference in the refractive index between the sapphire substrate and the gallium nitride-based compound semiconductor, and the difference in the refractive index between the gallium nitride-based compound semiconductor element and the resin that seals it, the gallium nitride-based compound semiconductor emits However, there is a problem that the reflected light is interfered by being multiply reflected at the interface, and the reflected light is absorbed inside the gallium nitride-based compound semiconductor, so that the emitted light cannot be efficiently extracted to the outside. In particular, the difference in refractive index is fatal in the case of flip-chip bonding, and although the light-emitting area is increased by flip-chip bonding, the emission efficiency cannot be improved with sapphire.
This problem has been improved by thickly stacking a gallium nitride-based compound semiconductor on sapphire, then stacking a device structure, and polishing / removing sapphire. Polishing / removal of sapphire may be performed before stacking element structures.

[0004]

If the multiple reflections of the gallium nitride-based compound semiconductor substrate, the gallium nitride-based compound semiconductor element, and the sealing resin can be suppressed and the interference can be further reduced, the external quantum efficiency can be improved. As a result, the luminous efficiency can be improved. Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to suppress the interference caused by multiple reflection of light inside the gallium nitride-based compound semiconductor, thereby making the gallium nitride-based compound semiconductor device Is to improve the external quantum efficiency of.

[0005]

[Means for Solving the Problems] We have conducted a number of experiments to suppress multiple reflections inside the gallium nitride-based compound semiconductor and to increase the external quantum efficiency. It was newly found that the above problems can be solved by causing diffuse reflection on the surface of the compound semiconductor. Therefore, in a light emitting device in which a gallium nitride compound semiconductor substrate is laminated on a gallium nitride compound semiconductor substrate, the surface of the gallium nitride compound semiconductor substrate facing the element laminating surface has irregularities. . As a result, total reflection of the light emitted in the light extraction surface direction on the extraction surface is suppressed, and the light extraction efficiency is improved. Further, in the gallium nitride-based compound semiconductor element according to the present invention, the irregularities are formed by dry etching and / or wet etching.
Although the sapphire substrate is polished and removed before etching, the interface between the sapphire substrate and the gallium nitride-based compound semiconductor has stress, strain, dislocation, etc., and the etching rate is faster than other surfaces. In particular, a portion having a high dislocation density and poor crystallinity has a high etching rate, so that unevenness is formed on the surface of the gallium nitride-based compound semiconductor substrate. Further, in the gallium nitride-based compound semiconductor light emitting device according to the present invention, the irregularities have {11-20} planes or {11-20}
The plane and the (0001) plane are stepped pits. This shape can be produced by dry etching, but wet etching is easier to produce. In the case of dry etching, it may depend on conditions such as RIE,
In many cases, the etching power is too strong, and etching is performed regardless of whether the surface is stable or metastable. On the other hand, since wet etching has a weak etching force, it is etched along the stable surface and the metastable surface. More specifically, the stable surface is less likely to be etched, and the metastable surface is more easily etched than the stable surface, so that the metastable surface appears. When a gallium nitride-based compound semiconductor device is treated with an etching solution, only the surface of the sapphire substrate that has been polished / removed is significantly etched. This is because when a gallium nitride-based compound semiconductor is stacked on a sapphire substrate, the (0001) plane, which is a stable surface, and the {11-20} plane, which is a metastable surface, grow at the same time due to the mismatch of the lattice constants. When it grows to the film thickness,
It can be considered that only the (0001) plane grows. Taking these into consideration, the shape of the unevenness can be varied depending on the combination of the growth condition of the gallium nitride compound semiconductor on the sapphire substrate and the etching condition, and the optimum value can be selected. The etching can be performed so that only the {11-20} planes appear continuously, or the {11-20} planes can be sparsely present, and of course, a suitable size can be selected. It may be a pit in which the {11-20} plane and the (0001) plane appear in steps. As described above, various characteristics such as the directivity and the viewing angle are improved by forming a specific surface rather than simply roughening the surface to make it rough and making it uneven. Further, the gallium nitride compound semiconductor substrate of the gallium nitride compound semiconductor device according to the present invention is doped with n-type impurities and / or p-type impurities. By doping in this way, the substrate can be made to have conductivity, and variations in the device structure such as forming electrodes on the back surface increase.

Further, in the gallium nitride-based compound semiconductor light emitting device according to the present invention, the n-type impurities are Si, G
At least one of e, Sn, and S is included. In the periodic table
This is because the gallium nitride-based compound semiconductor becomes n-type by adding the group IV and group VI elements. The p-type impurity in the gallium nitride-based compound semiconductor light emitting device according to the present invention contains at least one of Mg, Zn, Ca, and Be. This is because the gallium nitride-based compound semiconductor becomes p-type by adding the IIA group and IIB group elements in the periodic table.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

As a method for growing a gallium nitride-based compound semiconductor in the present invention, a nucleus or a layer made of a first gallium nitride-based compound semiconductor is grown on a substrate 1, and a second step is performed thereon by a hydride vapor phase epitaxial growth method. And a third gallium nitride based compound semiconductor are grown.

According to the present invention, sapphire or SiC (6H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, etc.
H, 3C), spinel, ZnS, ZnO, GaAs, S
i or a gallium nitride-based compound semiconductor or the like is used as the substrate.

These substrates have flat surfaces, but if nuclei or layers made of gallium nitride compound semiconductor can be grown, for example, those having fine roughness due to etching or the like, unevenness on the substrate, It may have a slope or step shape.

Next, a buffer layer (not shown)
Is grown on the substrate 1, the lattice constant mismatch with the substrate 1 can be relaxed. For example, since the lattice mismatch between gallium nitride and sapphire is as large as about 16%, it is difficult to obtain a substrate having good surface morphology and crystallinity. The buffer layer has the effect of alleviating this difference in lattice constant, and as a specific example,
AlN, GaN, AlGaN, InGaN, and InA
1 GaN may be mentioned. Hydrogen is used as a carrier gas and trimethylgallium, trimethylaluminum, trimethylindium, or the like is used as a source gas, and the film is grown at a temperature of 300 ° C. or higher and 900 ° C. or lower and a film thickness of 10 angstrom or more and 0.5 μm or less. The buffer layer may be omitted depending on the type of substrate.

Next, a nucleus or layer made of the first gallium nitride-based compound semiconductor is grown. As a growth method,
Although not particularly limited, it is preferable to use the MOCVD method for controlling the uniformity of the nucleus density of crystals, the orientation characteristics, the size, and the layer thickness.

The first gallium nitride-based compound semiconductor is not particularly limited to a nucleus or a layer formed of a thin film, but the first gallium nitride-based compound semiconductor is a C-axis for growing the second gallium nitride-based compound semiconductor. Those having excellent alignment characteristics are preferable.

As the growth conditions for the first gallium nitride compound semiconductor, the carrier gas and the source gas may be the same as those for the buffer layer, hydrogen is used as the carrier gas, trimethylgallium is used as the source gas, and the growth temperature is 900 ° C
~ 1100 ℃ and grown at a higher temperature than the buffer layer,
Those that grow as nuclei stop growing midway and become nuclei, and those that grow as layers form mirrors by continuing further growth.

The first gallium nitride-based compound semiconductor has a film thickness of 50 when grown as a layer having a mirror surface.
It is 0 angstrom to 50 μm, and has an effect of reducing crystal defects.

Next, hydride vapor phase epitaxial growth (HVP) is performed on the first gallium nitride compound semiconductor.
The gallium nitride compound semiconductor substrate is obtained by growing the second gallium nitride compound semiconductor and the third gallium nitride compound semiconductor by the method E). The halide vapor phase epitaxial growth method is effective for thick film growth of gallium nitride-based compound semiconductors and formation of a single substrate of gallium nitride-based compound semiconductors from which different kinds of substrates have been peeled off, because thick films can be grown in a short time. .

The growth process and growth conditions using the HVPE apparatus are shown below.

A quartz boat containing Ga metal is placed in the HVPE apparatus, and a substrate is placed at a position apart from the quartz boat. Next, an N source supply pipe is provided separately from the halogen gas supply pipe for reacting with the Ga metal and the halogen gas supply pipe.

As the halogen gas, there is HCl or the like, which is introduced together with the carrier gas through the halogen gas pipe. The halogen gas reacts with a metal such as Ga to generate a halide of a Group 3 element, and further reacts with the ammonia gas flown from the N source supply pipe to grow a gallium nitride-based compound semiconductor on the substrate. .

As a growth condition of the second gallium nitride compound semiconductor, the growth rate is 0.5 mm / hour or more, and more preferably 1 to 10 mm / hour.

The thickness of the second gallium nitride-based compound semiconductor is not particularly limited, but is preferably 300.
It is at least μm and is grown under normal pressure or slightly reduced pressure. 300
This is because it is difficult to polish / remove the sapphire substrate or the like unless it is more than μm.

The second gallium nitride-based compound semiconductor is undoped GaN, and n-type impurities are Si and G.
Ga doped with at least one kind of e, Sn and S
GaN or the like doped with N or p-type impurities can be used. Next, after growing the second gallium nitride-based compound semiconductor, a third gallium nitride-based compound semiconductor is grown thereon under the following conditions.

The third gallium nitride-based compound semiconductor is the second
It is preferable to grow at the same temperature as or higher than that of the gallium nitride-based compound semiconductor, and the temperature is 1000 ° C. or higher. However, the third gallium nitride-based compound semiconductor and the third
If the temperature difference from the gallium nitride-based compound semiconductor is large, the substrate warps, so the smaller temperature difference is preferable. The film thickness of the third gallium nitride-based compound semiconductor 4 is not particularly limited as long as the uppermost surface is a mirror surface, and is 30 μm.
It may be m or more. Therefore, the third gallium nitride-based compound semiconductor can be formed by the MOCVD method, the MBE method, or the like as long as it is a vapor growth method capable of growing the film thickness to about 30 μm.

As the third gallium nitride-based compound semiconductor, for example, undoped GaN, n-type impurities such as Si, or GaN doped with p-type impurities such as Mg can be used.

The composition formulas of the second gallium nitride compound semiconductor and the third gallium nitride compound semiconductor are as follows:
Is not particularly limited, the general formula _{In x Al y Ga 1-x} -y N
It can be represented by (0 ≦ x, 0 ≦ y, x + y <1).

However, these may have different compositions, and may be undoped, n-type impurity doped, and / or p-type.
It may be a gallium nitride-based compound semiconductor doped with a type impurity. The n-type impurities are Si, Ge, S, etc., and the p-type impurities are Mg, Be, Cr, M.
n, Ca, Zn etc. are mentioned.

The gallium nitride-based compound substrate obtained by the above growth method is a gallium nitride-based compound semiconductor substrate having a flat top surface and a wide range of low-defect portions which are mirror surfaces.

The device according to the present invention may be a light emitting device or an electronic device as long as it uses a gallium nitride compound semiconductor.

In the present invention, the gallium nitride-based compound substrate obtained by the above growth method is polished and removed from the sapphire substrate and then etched. The order is to epitaxially grow the light emitting device and then remove the sapphire substrate. Etching may be performed, the sapphire substrate may be removed, and the light emitting device may be epitaxially grown and then etched. Alternatively, the sapphire substrate may be removed and etched, and then the light emitting device may be epitaxially grown.

As shown in these figures, in order to make the back surface of the gallium nitride-based compound semiconductor non-mirror surface, that is, a state where fine irregularities are formed, the gallium nitride-based compound semiconductor substrate is grown or grown by a chemical or physical method. There is a method to make it a non-mirror surface. The method is a method in which the surface of the gallium nitride-based compound semiconductor on the back surface having a mirror surface is etched or polished to form fine irregularities to make it a non-mirror surface. There are two types of etching, for example, wet etching using a mixed acid of phosphoric acid and sulfuric acid and dry etching using an apparatus such as RIE (reactive ion etching), but either method may be used. By selecting an appropriate polishing agent, even a very hard gallium nitride compound semiconductor having a Mohs hardness of about 9 can be polished to make its surface non-mirror surface.

Wet etching is most suitable for obtaining the effects of the present invention, followed by dry etching and finally polishing. Whichever method is used, as described above, the sapphire substrate is polished and removed, and then etched, but stress, strain, dislocations, etc. exist at the interface between the sapphire substrate and the gallium nitride-based compound semiconductor. The etching rate is faster than the surface. In particular, a portion having a high dislocation density and poor crystallinity has a high etching rate, so that unevenness is formed on the surface of the gallium nitride-based compound semiconductor substrate. In addition, in the gallium nitride-based compound semiconductor light emitting device according to the present invention, the irregularities have {11-20} planes or {11-
The 20} plane and the (0001) plane are stepped pits. This shape can be produced by dry etching or polishing, but wet etching is easier. In the case of dry etching, although it depends on conditions such as RIE, the etching force is too strong, and etching is often performed regardless of whether the surface is stable or metastable. In addition, when the particles of the polishing agent, the hardness, etc. are mistakenly selected for polishing, the back surface of the gallium nitride-based compound semiconductor substrate is simply roughened, and the {11-20} plane or the {11-20} plane is obtained. And the (0001) plane does not appear in steps. The effect is obtained even with a simple rough surface, but the effect is further enhanced by forming the pits having the specific surface. On the other hand, since wet etching has a weak etching force, it is etched along the stable surface and the metastable surface. More specifically, the stable surface is less likely to be etched, and the metastable surface is more easily etched than the stable surface, so that the metastable surface appears. When a gallium nitride-based compound semiconductor device is treated with an etching solution, only the surface of the sapphire substrate that has been polished / removed is significantly etched. This is a stable surface due to the mismatch of lattice constants when the gallium nitride compound semiconductor is stacked on the sapphire substrate (0
When the (001) plane and the {11-20} plane, which is a metastable plane, grow at the same time and grow to a certain thickness, (000
1) It can be considered that only the faces grow. Taking these into consideration, the shape of the unevenness can be varied depending on the combination of the growth condition of the gallium nitride compound semiconductor on the sapphire substrate and the etching condition, and the optimum value can be selected. The etching can be performed so that only the {11-20} planes appear continuously, or the {11-20} planes can be sparsely present, and of course, a suitable size can be selected. It may be a pit in which the {11-20} plane and the (0001) plane appear in steps. As described above, various characteristics such as the directivity and the viewing angle are improved by forming a specific surface rather than simply roughening the surface to make it rough and making it uneven.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] As shown in FIG. 1, a sapphire substrate having a C surface as a main surface and an orientation flat surface as an A surface is used as a substrate 1, and M
It was set in an OCVD device and subjected to thermal cleaning at a temperature of 1050 ° C. for 10 minutes to remove water and adhered substances on the surface.

Next, at a temperature of 510 ° C., hydrogen was used as a carrier gas, ammonia and trimethylgallium were used as source gases, and a buffer layer made of GaN was grown to a thickness of 200 Å.

Then, a layer having flatness made of GaN as a first gallium nitride compound semiconductor is grown at a growth temperature of 1
It was formed with a film thickness of 20 μm at 050 ° C. In this example, 20.5 L / min of hydrogen was supplied as a carrier gas during growth, 5 L / min of ammonia was supplied as a source gas, and 25 cc / min of trimethylgallium was supplied as a source gas.

After growing the first gallium nitride-based compound semiconductor, it was set in a hydride vapor phase epitaxial growth apparatus, Ga metal was prepared in a quartz boat, and HCl gas was used as halogen gas to generate GaCl ₃ , and then GaCl ₃ was produced. , A second gallium nitride-based compound semiconductor 3 made of undoped GaN by reacting with ammonia gas that is N gas
Has grown up.

The growth temperature of the second gallium nitride compound semiconductor is 1000 ° C., and the growth rate is 1 mm / h.
The growth was performed with a film thickness of 300 μm. This plane photograph is shown in FIG. Next, a third gallium nitride compound semiconductor was grown on the second gallium nitride compound semiconductor in a hydride vapor phase epitaxial growth method apparatus.

The growth conditions at this time are that the growth temperature is the same as that of the second gallium nitride-based compound semiconductor 3 and the growth rate of the third gallium nitride-based compound semiconductor 4 is 50 μm /
Hour was grown to a film thickness of 50 μm. FIG. 4 shows a plane photograph which is flat and has a mirror surface.

Third gallium nitride-based material obtained as described above
The surface of the compound semiconductor 4 is flat and mirror-finished, as shown in FIG.
According to CL observation, the threading dislocation density is about 1 × 10.⁶
cm ^-2And a low-defect gallium nitride compound semi-
A conductor substrate can be provided. Obtained by the above method
The obtained gallium nitride compound semiconductor substrate 1 by MOVPE
Set it in the reaction vessel of and heat the substrate while flowing hydrogen.
Temperature to 1050 ° C to clean the substrate.
U (Buffer layer 2) Then, the temperature is lowered to 510 ° C.
Hydrogen as carrier gas and ammonia and TMG (source gas as source gas)
Limemethylgallium) and GaN on the substrate 1
Buffer layer 2 with a film thickness of about 100 Å.
Make it longer. (Undoped GaN layer 3) After growth of the buffer layer 2, TMG
Stop and raise the temperature to 1050 ° C. 105
When the temperature reaches 0 ° C, TMG and ammonia are also used as source gas.
Gas is used to form the undoped GaN layer 3 with a thickness of 1.5 μm.
Grow with. (N-type contact layer 4) Then, at 1050 ° C.,
TMG as a source gas, ammonia gas, and silane as an impurity gas
4.5 × 10 Si using gas¹⁸/cm³Doped G
The n-type contact layer 4 made of aN has a film thickness of 2.265 μm.
Grow thick. (N-type first multilayer film layer 5) Next, stop the silane gas only, and 1
At 050 ° C, using TMG and ammonia gas,
The lower layer 5a made of GaN has a thickness of 2000 angstroms.
Of the same thickness, and then added silane gas at the same temperature.
Si Si 4.5 × 10¹⁸/cm³From doped GaN
The intermediate layer 5b having a thickness of 300 angstroms.
Then, stop the silane gas only, and keep it at the same temperature.
50 angstroms of upper layer 5c made of doped GaN
With a total thickness of 2350 Å
Growing the first multilayer 5 of strom. (N-type second multilayer film layer 6) Next, at the same temperature,
40 angstroms of fourth nitride semiconductor layer of GaN
Trom growth, then temperature to 800 ° C., TM
Undoped In using G, TMI, and ammonia_0.13G
a_0.8720 angstroms of third nitride semiconductor layer made of N
Grow troms. And repeat these operations,
10 layers are alternately stacked in the order of 4th + 3rd, and finally G
The fourth nitride semiconductor layer made of aN has a thickness of 40 angstroms.
N-type second multilayer consisting of layer-grown superlattice structure multilayer film
The film layer 6 is grown to a film thickness of 640 Å. (Active layer 7) Next, a barrier layer made of undoped GaN is formed.
Grow to a thickness of 200 Å, then
To 800 ° C and use TMG, TMI, and ammonia
Undoped In_0.4Ga_0.630 layers of N well layer
Grow with a thickness of Gstrom. And barrier + well +
Barrier + well ... 5 barrier layers in the order of + barrier, well layer
4 layers are alternately laminated to give a total film thickness of 1120 angstroms.
Grow an active layer 7 of a quantum well structure
It (Medium-concentration-doped multilayer p-type cladding layer 8) Next, temperature
TMG, TMA, ammonia, Cp2Mg at 1050 ℃
(Cyclopentadienyl magnesium)
5 x 10¹⁹/cm³Doped p-type Al_0.2Ga_0.8From N
A first nitride semiconductor layer having a thickness of 40 Å
Thick, followed by a temperature of 800 ° C., TMG,
5x10 Mg using TMI, ammonia and Cp2Mg
¹⁹/cm³Doped In_0.03Ga_0.97The second consisting of N
Nitride semiconductor layer grown to a thickness of 25 Å
Let Then, these operations are repeated until the first and second order.
By alternately stacking 5 layers each, and finally, the first nitride semiconductor layer
Structure grown with a thickness of 40 Å
The p-side multilayer clad layer 8 consisting of
Grow with a thickness of Gstrom. (Lightly-doped p-type lightly-doped layer 9) Subsequently, 10
Undoped G using TMG and ammonia at 50 ° C
2,000 angstroms of p-type lightly doped layer 9 made of aN
Grow at troth thickness. This lightly doped layer 9
Grows undoped during growth, but
Doped in the p-type clad layer 8
Diffuses during the growth of the lightly doped layer 9, and
The heavily doped p-type contact layer 10 is grown.
At this time, Mg diffuses and the low-concentration doped layer 9 exhibits p-type.

The Mg concentration of the low concentration doped layer 9 is 2 × 10 ¹⁸ / cm ^{3 in the} lowest concentration portion. Further, as shown in FIG. 2, the change in the Mg concentration of the low-concentration doped layer 9 is almost the same as the Mg concentration of the p-type cladding layer in the portion in contact with the p-type cladding layer 8, but The Mg concentration gradually decreases with increasing distance from the layer 8, and the Mg concentration in the vicinity of the p-type contact layer 10 (immediately before the growth of the p-type contact layer 10) shows a substantially minimum value.

(Highly-doped p-type contact layer 10)
Then, at 1050 ° C, TMG, ammonia, Cp2M
Using g, a p-type contact layer 10 made of GaN doped with 1 × 10 ²⁰ / cm ^{3 of} Mg is grown to a film thickness of 1200 Å.

After completion of the reaction, the temperature was lowered to room temperature, and the wafer was further heated in a nitrogen atmosphere in a reaction vessel at 700 ° C.
Annealing is performed at 0 ° C. to further reduce the resistance of the p-type layer.

After the annealing, the wafer is taken out of the reaction vessel, the sapphire substrate is polished and removed, and the back surface side of the gallium nitride compound semiconductor substrate is etched. (Etching treatment of gallium nitride compound semiconductor substrate)
A mixed acid of phosphoric acid and sulfuric acid is used. Phosphoric acid: sulfuric acid = (1.
Mix at a molar ratio of 7: 5.9). Phosphoric acid is 8.5mo
1 / l and sulfuric acid having a concentration of 9.8 mol / l are used, and when the etching treatment is performed for 15 minutes, {11-20} planes and (0001) planes form stepwise pits having a width of 10 μm.

After etching, the N-type film having a film thickness of 200 angstrom is formed on almost the entire surface of the p-type contact layer 10 as the uppermost layer.
Translucent p-electrode 11 containing i and Au, and its p-electrode 10
P pad electrode 12 made of Au for bonding
Is formed with a film thickness of 0.5 μm. On the other hand, the n-type electrode 12 containing W and Al was formed on the surface of the n-type contact layer 4 exposed by etching to obtain an LED element.

This LED element emitted pure green light of 520 nm at a forward current of 20 mA.

[Example 2] The same procedure as in Example 1 was carried out except that the gallium nitride compound semiconductor substrate was dry-etched. The characteristics were almost the same. [Example 3] The same procedure as in Example 1 was carried out except that the gallium nitride compound semiconductor substrate was etched by polishing. For the surface plate used for polishing, tin, tin-lead, resin tin,
Resin copper or the like was used, and diamond was used as an abrasive. The characteristics were almost the same as in Example 1.

[0046]

As described above, the gallium nitride-based compound semiconductor device of the present invention has a back surface having a specific shape, so that light interference due to multiple reflection in the gallium nitride-based compound semiconductor layer can be suppressed. . Therefore, the light emission of the gallium nitride-based compound semiconductor can be effectively extracted to the outside, and the external quantum efficiency of the light emitting device is improved. Further, since peaks due to interference other than the intended emission peak do not appear in the emission spectrum, the color purity can be improved when a blue light emitting diode is manufactured using a gallium nitride-based compound semiconductor.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a gallium nitride-based compound semiconductor showing an embodiment of the present invention.

FIG. 2 is a partial perspective view of a gallium nitride-based compound semiconductor showing an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a gallium nitride-based compound semiconductor showing an embodiment of the present invention.

FIG. 4 is a partial perspective view of a gallium nitride-based compound semiconductor showing an embodiment of the present invention.

FIG. 5 is an enlarged photograph of a pit portion of a gallium nitride-based compound semiconductor showing an embodiment of the present invention.

FIG. 6 is an enlarged photograph of a pit portion of a gallium nitride-based compound semiconductor showing an embodiment of the present invention.

FIG. 7 is an enlarged photograph of a pit portion of a gallium nitride-based compound semiconductor showing an embodiment of the present invention.

[Simple explanation of symbols]

1 ... Substrate 2 ... Epi 3 ... Electrode 4 ... Electrode 5 ... pit

Claims (6)

[Claims] 1. A light emitting device comprising a gallium nitride compound semiconductor substrate on which a gallium nitride compound semiconductor is laminated, wherein a surface of the gallium nitride compound semiconductor substrate facing the element laminating surface has irregularities. A characteristic gallium nitride compound semiconductor device. 2. The unevenness is formed by dry etching and / or wet etching.
2. A gallium nitride-based compound semiconductor device described in. 3. The unevenness has a {11-20} plane or a {11-20} plane.
The gallium nitride-based compound semiconductor device according to claim 1 or 2, which is a pit in which the −20} plane and the (0001) plane appear in steps. 4. The gallium nitride compound semiconductor device according to claim 1, wherein the gallium nitride compound semiconductor substrate is doped with n-type impurities and / or p-type impurities. 5. The n-type impurity is Si, Ge, Sn,
The gallium nitride-based compound semiconductor device according to claim 4, containing at least one of S. 6. The p-type impurity is Mg, Zn, Ca,
The gallium nitride-based compound semiconductor device according to claim 4, containing at least one of Be.