JP2004134772A - Nitride-based semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride-based semiconductor device capable of enhancing light-emitting efficiency by reducing light absorbing loss in a contact layer. <P>SOLUTION: This nitride based semiconductor device comprises an n-type contact layer 4 formed on a sapphire substrate 1, an MQW active layer 5 formed on the n-type contact layer 4 and composed of a nitride-based semiconductor layer, a p-type clad layer 7 formed on the MQW active layer 5, an un-doped contact layer 8 formed on the p-type clad layer 7 and a p-side electrode 9 formed on the un-doped contact layer 8. <P>COPYRIGHT: (C)2004,JPO

Description

<< The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device in which a nitride semiconductor layer is formed on a substrate.

_{Recently, In X Al Y Ga 1-} X-Y N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) nitride nitride semiconductor is used consisting of a semiconductor light emitting diode element (LED) or nitride Nitride-based semiconductor light emitting devices such as semiconductor laser devices (LDs) have been put to practical use.

The basic structure of a conventional nitride semiconductor light emitting device on a substrate, the n-type nitride-based semiconductor layer made of n-type _{Al Y Ga 1-Y N (} 0 ≦ Y ≦ 1), In X Ga 1 _{-X N (0 ≦ X ≦ 1} ) and the active layer made of, p-type _{Al Z Ga 1-Z N (} 0 ≦ Z ≦ 1) p -type nitride semiconductor layer and the hetero to sequentially stacked double consisting Structure. Usually, the semiconductor device further includes an n-type contact layer for realizing ohmic contact with the n-side electrode, and a p-type contact layer for realizing ohmic contact with the p-side electrode. In the case of a nitride-based semiconductor laser device, an n-type light guide layer and a p-type light guide layer may be formed so as to sandwich an active layer.

Further, the n-type and p-type nitride semiconductor layers of the above-described nitride semiconductor light emitting device dope the nitride semiconductor with impurities that generate n-type carriers (electrons) or p-type carriers (holes). Formed by In order to obtain a nitride-based semiconductor light-emitting device having good luminous efficiency, it is indispensable to suppress light absorption in each nitride-based semiconductor layer. However, since impurities doped to obtain a p-type nitride semiconductor have a low activation rate, conventionally, a large amount of impurities are doped to obtain a p-type nitride semiconductor having a predetermined carrier concentration. I needed to. In this case, the absorption of light in the p-type contact layer or the p-type optical guide layer having a small band gap is increased due to the impurity level formed by introducing a large amount of impurities into the p-type nitride semiconductor. was there. Further, there is a disadvantage that light absorption is increased due to crystal defects generated by doping a large amount of impurities.

Therefore, conventionally, a nitride-based semiconductor laser device capable of reducing light absorption due to impurity doping by forming an undoped light guide layer on an active layer instead of the p-type light guide layer has been proposed. (For example, see Non-Patent Document 1).
"IEICE Technical Report" IEICE, June 15, 2002, pp. 63-66

However, in the conventional nitride-based semiconductor laser device proposed above, no measures have been taken to prevent light absorption in the p-type contact layer. That is, the p-type contact layer is doped with a large amount of impurities in order to realize ohmic contact with the p-side electrode. Thereby, even if the light absorption in the undoped light guide layer described above is reduced, it is difficult to suppress the light absorption caused by impurity doping in the p-type contact layer. As a result, there is a problem that it is difficult to improve the luminous efficiency of the nitride-based semiconductor laser device. Further, in a nitride semiconductor light emitting diode device in which light is emitted through a p-type contact layer, if light absorption in the p-type contact layer increases, the effect on the light emitting characteristics of the nitride semiconductor light emitting diode device is greater. There is a problem that becomes.

On the other hand, conventionally, a technique has been proposed in which a contact layer has a modulation-doped superlattice structure in which an undoped nitride-based semiconductor layer and an impurity-doped p-type nitride-based semiconductor layer are alternately stacked. ing. This technique is disclosed, for example, in Japanese Patent Application Laid-Open No. 2001-60720.

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 2001-60720, the undoped nitride-based semiconductor layer is disposed on both sides (upper and lower) of the undoped nitride-based semiconductor layer in the contact layer. In some cases, impurities may diffuse into the nitride-based semiconductor layer. In this case, since an impurity level is formed in the undoped nitride-based semiconductor layer, it is difficult to suppress light absorption in the contact layer. As a result, even if the contact layer has a modulation-doped superlattice structure comprising a stacked structure of an undoped nitride-based semiconductor layer and an impurity-doped p-type nitride-based semiconductor layer, the nitride-based semiconductor There is a problem that it is difficult to improve the luminous efficiency of the light emitting element.

As a method of suppressing light absorption in the p-type contact layer, light absorption in the p-type contact layer is hardly generated by using a p-type nitride-based semiconductor layer having a large band gap as the p-type contact layer. Can be considered. However, by increasing the band gap of the p-type contact layer, the barrier at the interface between the p-side electrode and the p-type contact layer increases, so that a good ohmic contact between the p-side electrode and the p-type contact layer can be achieved. It will be difficult to achieve. This causes a problem that the luminous efficiency is further reduced and the drive voltage is increased.

The present invention has been made to solve the above-described problems, and one object of the present invention is to improve light emission efficiency by reducing light absorption loss in a contact layer. An object of the present invention is to provide a nitride semiconductor light emitting device.

Means for Solving the Problems and Effects of the Invention

In order to achieve the above object, a nitride-based semiconductor light-emitting device according to one aspect of the present invention includes a first conductivity-type first nitride-based semiconductor layer formed on a substrate, and a first nitride-based semiconductor layer. An active layer formed of a nitride-based semiconductor layer formed thereon, a second conductivity-type second nitride-based semiconductor layer formed on the active layer, and an undoped layer formed on the second nitride-based semiconductor layer It has a contact layer and an electrode formed on the undoped contact layer. The “undoped” in the present invention means that impurities are not intentionally doped. Therefore, not only the case where the impurity is not doped at all but also the case where the impurity is unintentionally mixed in a small amount correspond to the “undoped” of the present invention.

In the nitride-based semiconductor device according to this one aspect, as described above, since the impurity level is not formed in the undoped contact layer by providing the undoped contact layer, light absorption due to the impurity level is prevented. Can be. Further, since the undoped contact layer has no crystal defects caused by doping with impurities, the undoped contact layer has good crystallinity. Therefore, light absorption due to crystal defects in the undoped contact layer can also be suppressed. Thereby, light absorption loss in the undoped contact layer can be reduced, so that luminous efficiency can be improved.

に お い て In the nitride semiconductor light emitting device according to the one aspect, preferably, the band gap of the undoped contact layer is smaller than the band gap of the second nitride semiconductor layer. With this configuration, the energy barrier at the interface between the undoped contact layer and the electrode is reduced, so that ohmic contact between the undoped contact layer and the electrode can be easily realized. Thereby, the luminous efficiency can be further improved, and the driving voltage can be reduced.

In the nitride semiconductor light emitting device according to the one aspect, preferably, the first conductivity type first nitride semiconductor layer is an n-type first nitride semiconductor layer, and the second conductivity type second nitride semiconductor layer is a second conductivity type second nitride semiconductor layer. The nitride-based semiconductor layer is a p-type second nitride-based semiconductor layer.

に お い て In the nitride semiconductor light emitting device according to the one aspect, preferably, the undoped contact layer has a thickness of 1 nm or more and 10 nm or less. According to this structure, the contact resistance between the undoped contact layer and the electrode can be reduced, so that good ohmic contact between the undoped contact layer and the electrode can be obtained. Further, the resistance of the undoped contact layer can be reduced.

に お い て In the nitride-based semiconductor light emitting device according to the above aspect, preferably, the undoped contact layer has a band gap larger than the band gap of the active layer. When the active layer is made of a single material, the band gap of the active layer means the band gap of the material. In the case of an active layer having a multilayer structure such as a quantum well structure, the band gap of the active layer means an energy difference between two quantum levels (ground levels) formed in a conduction band and a valence band. I do. With this configuration, light absorption in the undoped contact layer can be easily reduced. In this case, the undoped contact layer preferably contains InGaN. With this configuration, the band gap of the undoped contact layer can be easily made smaller than that of the second nitride-based semiconductor layer.

In the nitride-based semiconductor light-emitting device according to the one aspect, preferably, the undoped contact layer is formed of a single undoped nitride-based semiconductor layer. According to this structure, the impurity is diffused into the undoped contact layer as compared with the modulation-doped superlattice structure contact layer including the undoped nitride-based semiconductor layer and the impurity-doped nitride-based semiconductor layer. Can be suppressed.

In the nitride-based semiconductor light-emitting device according to the one aspect, preferably, it is formed between at least the active layer and the second-conductivity-type second nitride-based semiconductor layer, and has a band gap larger than that of the second nitride-based semiconductor layer. An undoped third nitride-based semiconductor layer made of a nitride-based semiconductor having a small thickness. With this configuration, the third nitride-based semiconductor layer can control light emission characteristics such as light confinement characteristics, and can also suppress light absorption in the third nitride-based semiconductor layer.

In this case, preferably, the undoped third nitride-based semiconductor layer is formed between the active layer and the first conductivity-type first nitride-based semiconductor layer and the second conductivity-type second nitride-based semiconductor layer. Of these, it is formed only between the active layer and the second nitride-based semiconductor layer. With this configuration, a region where the intensity of light generated in the active layer is high is shifted toward the second nitride-based semiconductor layer, so that light absorption in the first conductivity-type first nitride-based semiconductor layer is suppressed. Is done. In this case, even if the region with high light intensity is shifted to the second nitride-based semiconductor layer side, no impurity level or crystal defect is formed in the undoped contact layer on the second nitride-based semiconductor layer, so that light absorption is prevented. Does not increase. As a result, the effect of improving the luminous efficiency of the nitride-based semiconductor light emitting device is increased.

In this case, preferably, the semiconductor device further includes a fourth nitride-based semiconductor layer formed between the active layer and the first conductivity-type first nitride-based semiconductor layer. It has a thickness smaller than the thickness of the nitride-based semiconductor layer. With this configuration, a region where the intensity of light generated in the active layer is high is shifted toward the second nitride-based semiconductor layer, so that light absorption in the first conductivity-type first nitride-based semiconductor layer is suppressed. Is done. In this case, even if the region with high light intensity is shifted to the second nitride-based semiconductor layer side, no impurity level or crystal defect is formed in the undoped contact layer on the second nitride-based semiconductor layer, so that light absorption is prevented. Does not increase. As a result, the effect of improving the luminous efficiency of the nitride-based semiconductor light emitting device is increased.

In the nitride-based semiconductor light emitting device according to the one aspect, the undoped contact layer may include GaN.

In the nitride-based semiconductor light-emitting device according to the above aspect, preferably, the second-conductivity-type second nitride-based semiconductor layer includes a second-conductivity-type clad layer having a convex portion, and the undoped contact layer is The ridge portion is formed on the upper surface of the projection of the second conductivity type cladding layer, and the projection of the second conductivity type cladding layer and the undoped contact layer constitute a ridge. According to this structure, a ridge portion as a current passage region can be easily formed.

In the nitride-based semiconductor light-emitting device according to the one aspect, preferably, an undoped fifth nitride-based semiconductor layer formed between the substrate and the first conductivity-type first nitride-based semiconductor layer is further provided. Prepare. According to this structure, since the undoped fifth nitride-based semiconductor layer has no crystal defects caused by impurity doping, each of the nitride-based semiconductor layers (the first to fifth layers) sequentially formed on the fifth nitride-based semiconductor layer is formed. Generation of crystal defects in the first nitride-based semiconductor layer, the active layer, the second nitride-based semiconductor layer, and the undoped contact layer) can be further suppressed. Thereby, the nitride-based semiconductor layers (first nitride-based semiconductor layer, active layer, second nitride-based semiconductor layer, and undoped contact layer) in which crystal defects are further reduced can be formed. The resulting light absorption can be further suppressed. As a result, a nitride-based semiconductor light-emitting device with higher luminous efficiency can be formed.

In this case, preferably, the undoped fifth nitride-based semiconductor layer is made of a low-dislocation nitride-based semiconductor formed by selective lateral growth. According to this structure, it is possible to easily obtain a low dislocation fifth nitride-based semiconductor layer in which not only crystal defects caused by impurity doping but also other crystal defects are reduced. Generation of crystal defects in nitride semiconductor layers (first nitride semiconductor layer, active layer, second nitride semiconductor layer, and undoped contact layer) sequentially formed on the nitride semiconductor layer be able to.

In the nitride-based semiconductor light-emitting device according to the one aspect, the second-conductivity-type second nitride-based semiconductor layer preferably includes a second-conductivity-type cladding layer made of AlGaN. According to this structure, the band gap of the second nitride-based semiconductor layer can be easily increased, so that light absorption in the clad layer made of the second nitride-based semiconductor layer can be reduced.

In the nitride-based semiconductor light-emitting device according to the one aspect, the undoped contact layer may have a multilayer structure such as a superlattice structure including a plurality of undoped nitride-based semiconductor layers.

In this case, preferably, the second conductivity type second nitride-based semiconductor layer includes a second conductivity type second nitride-based semiconductor layer made of AlGaN, and the undoped third nitride-based semiconductor layer is GaN. And an undoped third nitride-based semiconductor layer made of According to this structure, the band gap of the third nitride-based semiconductor layer can be easily made smaller than the band gap of the second nitride-based semiconductor layer.

In the nitride-based semiconductor light-emitting device according to the above aspect, preferably, the active layer includes an active layer made of a nitride-based semiconductor containing In, is formed on the active layer, and In of the active layer is desorbed. And a protection layer made of a nitride-based semiconductor for preventing the formation. According to this structure, the protective layer prevents In of the active layer from being desorbed, so that deterioration of the crystal of the active layer can be prevented.

Further, in the nitride-based semiconductor light-emitting device according to the above aspect, preferably, the first conductivity-type first nitride-based semiconductor layer includes a first conductivity-type contact layer, and the first conductivity-type contact layer is , Also has a function as a cladding layer of the first conductivity type.

In this case, preferably, the substrate includes an insulating substrate. According to this structure, a nitride-based semiconductor light emitting device having an insulating substrate can be easily obtained by providing an electrode on the contact layer which also functions as a clad layer.

In the nitride-based semiconductor light-emitting device according to the one aspect, preferably, the electrode on the undoped contact layer is formed in a comb shape. With this configuration, light can be emitted through the comb-shaped electrodes.

In the above case, preferably, the semiconductor device further includes a plurality of mask layers having overhang portions formed at predetermined intervals on the substrate, and the undoped fifth nitride-based semiconductor layer is formed by using selective lateral growth. Are formed so as to bury the mask layers. According to this structure, the triangular fifth nitride-based semiconductor layer is formed near the center between the mask layers from the initial stage of growth, and the fifth interlayer between the mask layers is formed below the overhang portion of the mask layer. A triangular fifth nitride-based semiconductor layer smaller than the triangular fifth nitride-based semiconductor layer located near the center is formed. For this reason, since the fifth nitride-based semiconductor layer grows in the lateral direction from the initial growth stage, dislocations generated in the fifth nitride-based semiconductor layer are bent in the horizontal direction from the initial growth stage. Thereby, a fifth nitride-based semiconductor layer having a smaller thickness and a reduced dislocation density can be formed.

In the nitride-based semiconductor light-emitting device according to the above aspect, preferably, the substrate is a GaN substrate of the first conductivity type. With this configuration, the luminous efficiency of the nitride-based semiconductor light-emitting device having the GaN substrate of the first conductivity type can be easily improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(1st Embodiment)
FIG. 1 is a cross-sectional view illustrating a nitride-based semiconductor light emitting diode device (blue LED chip) according to a first embodiment of the present invention, and FIG. 2 is a nitride-based semiconductor according to the first embodiment illustrated in FIG. It is a top view of a light emitting diode element. First, the structure of the nitride-based semiconductor light-emitting diode device according to the first embodiment will be described with reference to FIGS.

In the nitride semiconductor light-emitting diode device according to the first embodiment, as shown in FIG. 1, a low-temperature buffer layer 2 made of AlGaN having a thickness of about 10 nm is formed on a (0001) plane of a sapphire substrate 1. I have. The sapphire substrate 1 is an example of the “substrate” and the “insulating substrate” of the present invention. On the low-temperature buffer layer 2, a high-temperature buffer layer 3 of undoped GaN having a thickness of about 1 μm is formed. An n-type contact layer 4 made of n-type GaN doped with Si and having a thickness of about 5 μm is formed on the high-temperature buffer layer 3. The n-type contact layer 4 is formed in a convex shape by removing a part of the region. This n-type contact layer 4 also has a function as an n-type cladding layer. Note that the n-type contact layer 4 is an example of the “first nitride-based semiconductor layer” of the present invention.

In addition, six undoped In _0.15 Ga _0.85 N barrier layers 5 a having a thickness of about 5 nm, and a film of about 5 nm so as to be in contact with almost the entire surface of the projection of the n-type contact layer 4. An MQW active layer 5 having a multiple quantum well (MQW) structure in which five thick undoped In _0.35 Ga _0.65 N well layers 5 b are alternately stacked is formed. The MQW active layer 5 is an example of the “active layer” of the present invention. On the MQW active layer 5, a protective layer 6 of undoped GaN having a thickness of about 10 nm is formed. The protective layer 6 has a function of preventing crystal of the MQW active layer 5 from being deteriorated by preventing In of the MQW active layer 5 from desorbing.

Here, in the first embodiment, the protective layer 6 has a thickness of about 0.15 μm, a doping amount of about 3 × 10 ¹⁹ cm ⁻³ , and a carrier concentration of about 1 × 10 ¹⁸ cm ^−3. A p-type clad layer 7 made of p-type Al _0.05 Ga _0.95 N doped with Mg is formed. The p-type cladding layer 7 is an example of the “second nitride-based semiconductor layer” and the “cladding layer” of the present invention. In the first embodiment, an undoped contact layer 8 made of undoped In _0.15 Ga _0.85 N and having a thickness of about 1 nm to about 10 nm is formed on the p-type cladding layer 7. The band gap of the undoped contact layer 8 made of In _0.15 Ga _0.85 N is smaller than the band gap of the p-type clad layer 7 made of Al _0.05 Ga _0.95 N, and the undoped In _{0. It} is larger than the band gap of the MQW active layer 5 composed of ₁₅ Ga _0.85 N and undoped In _0.35 Ga _0.65 N. The band gap of the MQW active layer 5 means an energy difference between two quantum levels (ground levels) formed in a conduction band and a valence band, and is In _0.15 Ga _0.85 N and In _0.15 Ga _0.85 N. The energy difference between the quantum levels of the MQW active layer 5 composed of _0.35 Ga _0.65 N is smaller than the band gap of the undoped contact layer 8 composed of In _0.15 Ga _0.85 N.
On the upper surface of the undoped contact layer 8, a comb-shaped p-side electrode composed of a Pd film having a thickness of about 100 nm and an Au film having a thickness of about 100 nm, from bottom to top. 9 are formed. The p-side electrode 9 is an example of the “electrode” of the present invention.

FIG. 3 is a graph showing the contact resistance between the p-side electrode and the contact layer when the material and thickness of the contact layer are changed in the nitride semiconductor light emitting diode device according to the first embodiment shown in FIG. It is. The graph shown in FIG. 3 shows a relative value with respect to contact resistance when a Mg-doped p-type GaN layer having a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ is used as a contact layer. . Note that Mg-doped p-type GaN is a material that is typically used for a contact layer.

As shown in FIG. 3, the contact resistance of the undoped contact layer 8 is reduced by setting the thickness of the undoped contact layer 8 made of undoped In _0.15 Ga _0.85 N to about 1 nm to about 10 nm. It can be seen that the contact resistance of the p-type contact layer made of p-type GaN can be approximated. Also, it can be seen that even when an undoped contact layer made of undoped GaN is provided, the contact resistance can be reduced to some extent by setting the film thickness to about 1 nm to about 10 nm. However, the contact resistance of the undoped contact layer 8 made of undoped In _0.15 Ga _0.85 N can be smaller than that of the undoped contact layer made of undoped GaN. In consideration of the above points, the first embodiment uses the undoped contact layer 8 made of undoped In _0.15 Ga _0.85 N having a thickness of about 1 nm to about 10 nm. It can be seen that the contact resistance of the undoped contact layer made of undoped Al _0.05 Ga _0.95 N is large even when the film thickness is about 1 nm to about 10 nm. Further, it can be seen that the contact resistance of the p-type contact layer made of p-type Al _0.15 Ga _0.85 N is about 10 times as high as the contact resistance of the p-type contact layer made of p-type GaN.

As shown in FIGS. 1 and 2, a Ti film having a thickness of about 30 nm and a Ti film having a thickness of about 500 nm are formed in a partial region on the upper surface of the p-side electrode 9 from bottom to top. A p-side pad electrode 10 composed of an Au film and a Au film is formed. An n-side electrode 11 made of Al and having a thickness of about 500 nm is formed in a part of the surface of the n-type contact layer 4 other than the protrusions.

In the first embodiment, as described above, since the impurity level is not formed in the undoped contact layer 8 by providing the undoped contact layer 8, light absorption due to the impurity level can be prevented. In addition, since the undoped contact layer 8 has no crystal defects caused by doping with impurities, the undoped contact layer 8 has good crystallinity. Therefore, light absorption due to crystal defects in the undoped contact layer 8 can also be suppressed. Thereby, the light absorption loss in the undoped contact layer 8 can be reduced, so that the luminous efficiency of the nitride-based semiconductor light-emitting diode element can be improved.

In the first embodiment, as described above, the energy gap at the interface between the undoped contact layer 8 and the p-side electrode 9 is reduced by making the band gap of the undoped contact layer 8 smaller than the band gap of the p-type cladding layer 7. Since the barrier is reduced, ohmic contact between the undoped contact layer 8 and the p-side electrode 9 can be easily realized. Thereby, the luminous efficiency of the nitride-based semiconductor light-emitting diode element can be further improved, and the driving voltage can be reduced.

In the first embodiment, as described above, the contact resistance between the undoped contact layer 8 and the p-side electrode 9 is reduced by setting the thickness of the undoped contact layer 8 to about 1 nm to about 10 nm. Therefore, good ohmic contact can be obtained between the undoped contact layer 8 and the p-side electrode 9. Further, the resistance of the undoped contact layer 8 can be reduced.

In the first embodiment, as described above, the band gap of the p-type cladding layer 7 is formed by forming the p-type cladding layer 7 with p-type Al _0.05 Ga _0.95 N doped with Mg. Since the size can be easily increased, light absorption in the p-type cladding layer 7 can be reduced. Further, in the first embodiment, the band gap of the undoped contact layer 8 can be easily made smaller than that of the p-type cladding layer 7 by forming the undoped contact layer 8 with In _0.15 Ga _0.85 N. it can. Further, as described above, since the band gap of the undoped contact layer 8 is larger than the band gap of the MQW active layer 5, light absorption in the undoped contact layer 8 can be easily reduced.

FIGS. 4 and 5 are cross-sectional views for explaining the manufacturing process of the nitride-based semiconductor light-emitting diode device according to the first embodiment shown in FIGS. Next, a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the first embodiment will be described with reference to FIGS.

First, as shown in FIG. 4, a low-temperature buffer layer 2, a high-temperature buffer layer 3, and an n-type contact layer 4 are formed on a sapphire substrate 1 by MOVPE (Metal Organic Vapor Phase Epitaxy). , An MQW active layer 5, a protective layer 6, a p-type cladding layer 7, and an undoped contact layer 8 are sequentially grown.

Specifically, with the sapphire substrate 1 kept at a non-single crystal growth temperature of about 600 ° C., a carrier gas (H ₂ : about 50%) composed of H ₂ and N ₂ , NH ₃ , trimethylaluminum (TMAl ) And a source gas of trimethylgallium (TMGa), a low-temperature buffer layer 2 of AlGaN having a thickness of about 10 nm is grown on the (0001) plane of the sapphire substrate 1.

Next, while maintaining the substrate temperature at a single crystal growth temperature of about 1150 ° C., a carrier gas (H ₂ : about 50%) composed of H ₂ and N ₂ and a source gas composed of NH ₃ and TMGa are used. Then, a high-temperature buffer layer 3 made of undoped GaN having a thickness of about 1 μm is grown on the low-temperature buffer layer 2 at a growth rate of about 1 μm / h.

Next, with the substrate temperature kept at a single crystal growth temperature of about 1150 ° C., a carrier gas (H ₂ : about 50%) composed of H ₂ and N ₂ , a source gas composed of NH ₃ and TMGa, and SiH using a dopant gas comprising _4, grown at a growth rate of about 3 [mu] m / h, on the high-temperature buffer layer 3, the n-type contact layer 4 Si having a thickness of about 5μm is n-type GaN doped Let it.

Next, with the substrate temperature kept at a single crystal growth temperature of about 850 ° C., a carrier gas composed of H ₂ and N ₂ (H ₂ : about 1% to about 5%), NH ₃ , triethylgallium (TEGa) ) And a source gas consisting of trimethylindium (TMIn) at a growth rate of about 0.4 nm / s, on the n-type contact layer 4, six undoped In _0.15 Ga layers having a thickness of about 5 nm. Barrier layers 5a made of _0.85 N and five well layers 5b made of undoped In _0.35 Ga _0.65 N having a thickness of about 5 nm are alternately grown. Thereby, MQW active layer 5 is formed on n-type contact layer 4. Subsequently, a protective layer 6 made of undoped GaN having a thickness of about 10 nm is grown on the MQW active layer 5 at a growth rate of about 0.4 nm / s.

Next, while maintaining the substrate temperature at a single crystal growth temperature of about 1150 ° C., a carrier gas comprising H ₂ and N ₂ (H ₂ : about 1% to about 3%) and NH ₃ , TMGa and TMAl are used. Having a thickness of about 0.15 μm on the protective layer 6 at a growth rate of about 3 μm / h, using a source gas consisting of the following and a dopant gas consisting of cyclopentadienyl magnesium (Cp ₂ Mg): A p-type clad layer 7 made of Mg-doped p-type Al _0.05 Ga _0.95 N having a doping amount of about 3 × 10 ¹⁹ cm ⁻³ and a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ is grown. Let it.

At this time, Mg as an acceptor can be activated by reducing the H ₂ composition of the carrier gas to about 1% to about 3%, so that the p-type cladding layer 7 having a high carrier concentration can be obtained. it can.

Next, while maintaining the substrate temperature at a single crystal growth temperature of about 850 ° C., a carrier gas comprising H ₂ and N ₂ (H ₂ : about 1% to about 5%) and NH ₃ , TEGa and TMIn are used. Undoped contact layer made of undoped In _0.15 Ga _0.85 N having a thickness of about 1 nm to about 10 nm on the p-type cladding layer 7 at a growth rate of about 3 μm / h using a raw material gas Grow 8.

Then, as shown in FIG. 5, the undoped contact layer 8, the p-type cladding layer 7, the protective layer 6, the MQW active layer 5, and the n-type contact layer 4 are formed by a reactive ion beam etching (RIBE) method or the like. By removing the partial region, a partial region of the n-type contact layer 4 is exposed.

Next, as shown in FIGS. 1 and 2, a Pd film having a thickness of about 100 nm is formed on the upper surface of the undoped contact layer 8 from bottom to top by using a vacuum deposition method or the like. A comb-shaped p-side electrode 9 composed of an Au film having a thickness of 100 nm is formed. A p-side pad electrode composed of a Ti film having a thickness of about 30 nm and an Au film having a thickness of about 500 nm in a partial region on the upper surface of the p-side electrode 9 from bottom to top. Form 10 Further, on the exposed surface of the n-type contact layer 4, an n-side electrode 11 made of Al having a thickness of about 500 nm is formed.

(4) Thereafter, a heat treatment is performed at a temperature of about 600 ° C. to bring the p-side electrode 9 and the n-side electrode 11 into ohmic contact with the undoped contact layer 8 and the n-type contact layer 4, respectively.

(4) Finally, element separation is performed using a method such as scribing, dicing, and breaking so that, for example, a substantially square chip shape having a side length of about 400 μm is obtained. Thus, the nitride semiconductor light emitting diode device of the first embodiment is formed.

Further, after fixing the nitride-based semiconductor light-emitting diode element (blue LED chip) of the first embodiment formed as described above to a frame (not shown), the resin is heated to about 200 ° C. so as to cover them. By curing at a temperature, an LED lamp including the blue LED chip of the first embodiment may be manufactured.

(2nd Embodiment)
FIG. 6 is a sectional view showing a nitride-based semiconductor laser device (LD chip) according to a second embodiment of the present invention. With reference to FIG. 6, in the second embodiment, an example in which the present invention is applied to a nitride-based semiconductor laser device, unlike the first embodiment in which the present invention is applied to a nitride-based semiconductor light-emitting diode device, will be described. .

In the nitride-based semiconductor laser device according to the second embodiment, as shown in FIG. 6, a film of about 1 μm is formed on an oxygen-doped conductive n-type GaN substrate 21 having a (0001) Ga surface as a surface. An n-type GaN layer 22 doped with Si having a thickness is formed. On the n-type GaN layer 22, an n-type cladding layer 23 made of n-type Al _0.15 Ga _0.85 N doped with Si and having a thickness of about 1 μm is formed. The n-type GaN substrate 21 is an example of the “substrate” of the present invention, and the n-type GaN layer 22 and the n-type cladding layer 23 are examples of the “first nitride-based semiconductor layer” of the present invention.

On the n-type cladding layer 23, an n-type light guide layer 24 of n-type GaN having a thickness of about 100 nm is formed. Then, on the n-type optical guide layer 24, four undoped barrier layers 25a each having a thickness of about 15 nm and made of In _0.05 Ga _0.95 N, and three undoped In ₀ layers each having a thickness of about 4 nm. An MQW active layer 25 having a multiple quantum well structure in which well layers 25b made of _.1 Ga _0.9 N are alternately stacked.

Here, in the second embodiment, a protective layer 26 made of undoped Al _0.3 Ga _0.7 N and having a thickness of about 20 nm is formed on the MQW active layer 25. The protective layer 26 has a function of preventing In of the MQW active layer 25 from desorbing, thereby preventing the crystal of the MQW active layer 25 from deteriorating. On the protective layer 26, a light guide layer 27 made of undoped GaN having a thickness of about 100 nm is formed. The light guide layer 27 made of undoped GaN has a band gap smaller than the band gap of a p-type clad layer 28 made of Al _0.15 Ga _0.85 N described later. The light guide layer 27 is an example of the “third nitride-based semiconductor layer” of the present invention.

Then, on the light guide layer 27, p-type Al _0.15 Ga doped with Mg having a thickness of about 280 nm and having a stripe-shaped convex part having a width of about 1.5 μm near the center. _A p-type cladding layer 28 of _0.85 N is formed. The p-type cladding layer 28 is an example of the “second nitride-based semiconductor layer” and the “cladding layer” of the present invention.

Here, in the second embodiment, an undoped In _0.05 Ga _0.95 N having a thickness of about 5 nm is formed on the protrusion of the p-type cladding layer 28 made of p-type Al _0.15 Ga _0.85 N. An undoped contact layer 29 is formed. The projection of the p-type cladding layer 28 and the undoped contact layer 29 form a ridge portion serving as a current path region. The band gap of the undoped contact layer 29 is smaller than the band gap of the p-type cladding layer 28 and larger than the band gap of the MQW active layer 25. The band gap of the MQW active layer 25 means an energy difference between two quantum levels (ground levels) formed in the conduction band and the valence band, and is In _0.05 Ga _0.95 N and In _0.05 Ga. The energy difference between the quantum levels of the MQW active layer 25 composed of _0.1 Ga _0.9 N is smaller than the band gap of the undoped contact layer 29 composed of In _0.05 Ga _0.95 N.

An insulating film 30 made of SiO ₂ is formed so as to cover the surface of the p-type cladding layer 28 and the side surface of the undoped contact layer 29. A p-side electrode 31 composed of a Pd film, a Pt film, and an Au film is formed on the undoped contact layer 29 from bottom to top. The p-side electrode 31 is an example of the “electrode” of the present invention. Further, a p-side pad electrode 32 is formed so as to cover the surface of the insulating film 30 and the surface of the p-side electrode 31. An n-side electrode 33 composed of a Ti film, a Pt film, and an Au film is formed on the back surface of the n-type GaN substrate 21 from the side near the back surface of the n-type GaN substrate 21.

In the second embodiment, as described above, by providing the undoped contact layer 29, no impurity level is formed in the undoped contact layer 29, so that light absorption due to the impurity level can be prevented. In addition, the undoped contact layer 29 has good crystallinity because there is no crystal defect caused by impurity doping. Therefore, light absorption due to crystal defects in the undoped contact layer 29 can also be suppressed. Thus, the light absorption loss in the undoped contact layer 29 can be reduced, so that the light emitting efficiency of the nitride-based semiconductor laser device can be improved.

In the second embodiment, the energy at the interface between the undoped contact layer 29 and the p-side electrode 31 is reduced by making the band gap of the undoped contact layer 29 smaller than the band gap of the p-type cladding layer 28 as described above. Since the barrier is reduced, ohmic contact between the undoped contact layer 29 and the p-side electrode 31 can be easily realized.

In the second embodiment, as described above, the band gap of the p-type cladding layer 28 is increased by forming the p-type cladding layer 28 with p-type Al _0.15 Ga _0.85 N doped with Mg. Since the size can be easily increased, light absorption in the p-type cladding layer 28 can be easily reduced. Further, in the second embodiment, the band gap of the undoped contact layer 29 can be easily made smaller than that of the p-type cladding layer 28 by forming the undoped contact layer 29 with In _0.05 Ga _0.95 N. it can. Further, as described above, since the band gap of the undoped contact layer 29 is larger than the band gap of the MQW active layer 25, light absorption in the undoped contact layer 29 can be easily reduced.

In the second embodiment, as described above, the undoped light guide layer 27 having a band gap smaller than the band gap of the p-type cladding layer 28 is provided between the MQW active layer 25 and the p-type cladding layer 28. By providing the light guide layer 27, light emission characteristics such as light confinement characteristics can be controlled by the light guide layer 27, and light absorption in the light guide layer 27 can be suppressed.

FIGS. 7 to 9 are cross-sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. Next, the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment will be described with reference to FIGS.

First, as shown in FIG. 7, an n-type GaN layer 22, an n-type cladding layer 23, and an n-type cladding layer 23 are formed on an oxygen-doped n-type GaN substrate A light guide layer 24, an MQW active layer 25, a protective layer 26, a light guide layer 27, a p-type cladding layer 28 and an undoped contact layer 29 are sequentially grown.

Specifically, with the n-type GaN substrate 21 kept at a growth temperature of about 1150 ° C., a carrier gas (H ₂ : about 50%) composed of H ₂ and N ₂ and a source gas composed of NH ₃ and TMGa And a dopant gas comprising SiH _{4 at} a growth rate of about 3 μm / h on an oxygen-doped n-type GaN substrate 21 having a (0001) Ga surface as a surface. The n-type GaN layer 22 doped with Si is grown.

Next, with the substrate temperature kept at a growth temperature of about 1150 ° C., a carrier gas (H ₂ : about 50%) composed of H ₂ and N _2, a source gas composed of NH ₃ , TMGa and TMAl, and SiH _And n-type Al _0.15 Ga _0.85 N doped with Si having a thickness of about 1 μm on the n-type GaN layer 22 at a growth rate of about 3 μm / h using a dopant gas consisting of The n-type cladding layer 23 made of is grown. Subsequently, an n-type light guide layer 24 made of n-type GaN having a thickness of about 100 nm is grown on the n-type cladding layer 23 at a growth rate of about 3 μm / h.

Next, with the substrate temperature kept at a growth temperature of about 850 ° C., a carrier gas (H ₂ : about 1% to about 5%) composed of H ₂ and N ₂ and a raw material composed of NH ₃ , TEGa and TMIn The barrier layer 25a made of four undoped In _0.05 Ga _0.95 N having a thickness of about 15 nm is formed on the n-type light guide layer 24 at a growth rate of about 0.4 nm / s using a gas. And three well layers 25b made of In _0.1 Ga _0.9 N having a thickness of about 4 nm are alternately grown. Thus, the MQW active layer 25 is formed on the n-type light guide layer 24. Subsequently, a protective layer 26 made of undoped Al _0.3 Ga _0.7 N having a thickness of about 20 nm is grown on the MQW active layer 25 at a growth rate of about 0.4 nm / s.

Next, while maintaining the substrate temperature at a growth temperature of about 1150 ° C., a carrier gas composed of H ₂ and N ₂ (H ₂ : about 1% to about 3%), a source gas composed of NH ₃ and TMGa, Is used to grow an optical guide layer 27 made of undoped GaN having a thickness of about 100 nm on the protective layer 26 at a growth rate of about 3 μm / h. Further, a source gas made of TMAl was added, and a dopant gas made of Cp ₂ Mg was added, and Mg having a thickness of about 280 nm was doped on the light guide layer 27 at a growth rate of about 3 μm / h. A p-type cladding layer 28 made of p-type Al _0.15 Ga _0.85 N is grown.

At this time, by reducing the H ₂ composition of the carrier gas to about 1% to about 3%, Mg as an acceptor can be activated, so that the p-type cladding layer 28 having a high carrier concentration can be obtained. it can.

Next, with the substrate temperature kept at a growth temperature of about 850 ° C., a carrier gas (H ₂ : about 1% to about 5%) composed of H ₂ and N ₂ and a raw material composed of NH ₃ , TEGa and TMIn An undoped contact layer 29 made of undoped In _0.05 Ga _0.95 N having a thickness of about 5 nm is grown on the p-type cladding layer 28 at a growth rate of about 3 μm / h using a gas.

Then, as shown in FIG. 8, a Pd film, a Pt film, and an Au film are formed in the vicinity of the center on the undoped contact layer 29 from bottom to top using a vacuum deposition method and a lithography technique. The p-side electrode 31 to be formed is formed in a stripe shape having a width of about 1.5 μm.

Then, as shown in FIG. 9, the undoped contact layer 29 and a part of the p-type cladding layer 28 are removed using the p-side electrode 31 as a mask by a reactive ion beam etching method or the like. As a result, a convex portion (ridge portion) serving as a current injection region is formed.

Next, the surface of the p-type cladding layer 28, the surface of the undoped contact layer 29, and the surface of the p-side electrode 31 are covered by a plasma CVD method (Chemical Vapor Deposition). After forming an insulating film (not shown) made of _2, by removing the insulating film on the surface of the p-side electrode 31, an insulating film 30 having a shape as shown in FIG. 6 is obtained. Then, a p-side pad electrode 32 is formed so as to cover the surface of the insulating film 30 and the surface of the p-side electrode 31.

Finally, the n-type GaN substrate 21 is polished to a predetermined thickness (for example, about 100 μm), and then, on the back surface of the n-type GaN substrate 21, From the near side, an n-side electrode 33 composed of a Ti film, a Pt film, and an Au film is formed. Thus, the nitride-based semiconductor laser device of the second embodiment is formed.

(Third embodiment)
FIG. 10 is a cross-sectional view illustrating a nitride-based semiconductor light emitting diode device (blue LED chip) according to a third embodiment of the present invention. Referring to FIG. 10, in the third embodiment, an example in which a lower dislocation undoped GaN layer 44 is formed instead of the high-temperature buffer layer 3 formed in the first embodiment will be described. Other configurations are the same as those of the first embodiment.

That is, in the nitride-based semiconductor light-emitting diode device according to the third embodiment, as shown in FIG. 10, the cross section made of SiN having a thickness of about 10 nm to about 1000 nm is inverted on the (0001) plane of the sapphire substrate 41. The mesa-shaped (inverted trapezoidal) mask layer 42 is formed in a stripe shape (elongated shape) at a period of about 7 μm. The sapphire substrate 41 is an example of the “substrate” and the “insulating substrate” of the present invention. The mask layer 42 is formed such that the shortest distance between the adjacent mask layers 42 is smaller than the width of the sapphire substrate 41 exposed between the mask layers 42.

{Circle around (4)} On the sapphire substrate 41 exposed between the mask layers 42, a low-temperature buffer layer 43 made of AlGaN or GaN having a thickness of about 10 nm to about 50 nm is formed. Then, on the low-temperature buffer layer 43 and the mask layer 42, a low dislocation undoped GaN layer 44 having a thickness of about 2 μm is formed so as to fill the space between the mask layers 42 by using selective lateral growth. I have. The undoped GaN layer 44 is an example of the “fifth nitride-based semiconductor layer” of the present invention.

Then, the n-type contact layer 4, the MQW active layer 5, the protective layer 6, the p-type cladding layer 7, the undoped contact layer 8, the p-side electrode 9, the p-side pad electrode 10 and the n-type The thickness and composition of the side electrode 11 are the same as in the first embodiment shown in FIG.

In the third embodiment, as described above, the nitride semiconductor layers (4 to 8) are formed on the undoped GaN layer 44 having lower dislocations than the high temperature buffer layer 3 (see FIG. 1) of the first embodiment. Thereby, generation of crystal defects in each of the nitride semiconductor layers (4 to 8) can be further suppressed. Thereby, the nitride-based semiconductor layers (4 to 8) with further reduced crystal defects can be formed, so that light absorption due to crystal defects can be further suppressed. As a result, a blue LED chip with higher luminous efficiency can be formed.

効果 Other effects of the third embodiment are the same as those of the first embodiment.

FIGS. 11 to 13 are cross-sectional views for explaining a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the third embodiment shown in FIG. Next, the manufacturing process of the nitride-based semiconductor light-emitting diode device according to the third embodiment will be described with reference to FIGS.

First, as shown in FIG. 11, after forming an SiN film (not shown) on the entire surface of the sapphire substrate 41, a resist (not shown) is formed on a predetermined region of the SiN film. Then, using the resist as a mask, the SiN film is wet-etched to form a striped mask layer 42. This mask layer 42 is formed in an inverted mesa shape (an inverted trapezoidal shape) so as to have an overhang portion 42a. The opening of the mask layer 42 is preferably formed, for example, in the [11-20] direction of the sapphire substrate 41 or in the [1-100] direction of the sapphire substrate 41. Thereafter, a low-temperature buffer layer 43 made of AlGaN or GaN having a thickness of about 10 nm to about 50 nm is selectively grown on the sapphire substrate 41 exposed between the mask layers 42 at a growth temperature of about 500 ° C. to about 700 ° C. Let it.

Next, an undoped GaN layer 44 (see FIG. 13) is grown laterally on the low-temperature buffer layer 43 at a growth temperature of about 950 ° C. to about 1200 ° C. using the mask layer 42 as a selective growth mask by MOVPE. Let it. In this case, the undoped GaN layer 44 first grows upward on the exposed upper surface of the low-temperature buffer layer 43. Thereby, as shown in FIG. 12, an undoped GaN layer 44a having a triangular facet structure is grown near the center between the mask layers 42 from the initial stage of growth. An undoped GaN layer 44b having a facet structure smaller than the undoped GaN layer 44a is formed below the overhang portion 42a of the mask layer 42. Further, as the growth of the facet composed of the undoped GaN layers 44a and 44b progresses, the undoped GaN layers 44a and 44b grow laterally and unite, and also grow on the mask layer 42. Thereby, as shown in FIG. 13, an undoped GaN layer 44 having a thickness of about 2 μm and formed of a continuous film having a flat top surface is formed.

As described above, since the undoped GaN layer 44 grows in the lateral direction from the initial growth stage, dislocations generated in the undoped GaN layer 44 are bent in the horizontal direction from the initial growth stage. Thereby, an undoped GaN layer 44 having a smaller thickness and a dislocation density reduced to approximately 7 × 10 ⁷ cm ⁻² can be formed.

Thereafter, using the same manufacturing process as in the first embodiment, the n-type contact layer 4, the MQW active layer 5, the protection layer 6, the p-type cladding layer as shown in FIG. After the formation of the undoped contact layer 8 and the undoped contact layer 8 in that order, a part of the undoped contact layer 8 is removed from the n-type contact layer 4. Then, a p-side electrode 9 and a p-side pad electrode 10 are sequentially formed on the undoped contact layer 8. Thereafter, an n-side electrode 11 is formed on the exposed surface of the n-type contact layer 4.

(4) Finally, element separation is performed using a method such as scribing, dicing, and breaking so that, for example, a substantially square chip shape having a side length of about 400 μm is obtained. Thus, the nitride semiconductor light emitting diode device of the third embodiment is formed.

(Fourth embodiment)
FIG. 14 is a sectional view showing a nitride-based semiconductor laser device (LD chip) according to a fourth embodiment of the present invention. In the fourth embodiment, an example in which the n-type light guide layer 24 formed in the second embodiment is not provided will be described with reference to FIG. The other configuration is the same as that of the second embodiment.

That is, in the nitride-based semiconductor laser device according to the fourth embodiment, as shown in FIG. 14, a second embodiment is formed on an oxygen-doped conductive n-type GaN substrate 21 having a (0001) Ga surface as a surface. An n-type GaN layer 22 and an n-type cladding layer 23 having the same thickness and composition as those of the embodiment are sequentially formed.

Here, in the fourth embodiment, an MQW in which four barrier layers 25a and three well layers 25b having the same thickness and composition as in the second embodiment are alternately stacked directly on the n-type cladding layer 23. An active layer 25 is formed. That is, in the fourth embodiment, no n-type light guide layer is provided between the n-type cladding layer 23 and the MQW active layer 25.

Then, the thicknesses of the protective layer 26, the light guide layer 27, the p-type cladding layer 28, the undoped contact layer 29, the insulating film 30, the p-side electrode 31, and the p-side pad electrode 32 formed on the MQW active layer 25 and The composition is the same as that of the second embodiment shown in FIG. The thickness and composition of the n-side electrode 33 formed on the back surface of the n-type GaN substrate 21 are the same as those of the second embodiment shown in FIG.

In the fourth embodiment, as described above, by providing no n-type light guide layer between the n-type cladding layer 23 and the MQW active layer 25, a region where the intensity of light generated by the MQW active layer 25 is high is provided. Is shifted to the p-side, so that light absorption in the n-type cladding layer 23 is suppressed. In this case, even if the region with high light intensity is shifted to the p-side, no impurity level or crystal defect due to doping is formed in the undoped contact layer 29, so that light absorption does not increase. As a result, the effect of improving the luminous efficiency of the nitride-based semiconductor laser device increases.

The other effects of the fourth embodiment are similar to those of the second embodiment.

FIGS. 15 to 17 are cross-sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. Next, the manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment will be described with reference to FIGS.

First, as shown in FIG. 15, an n-type GaN layer 22 and an n-type cladding layer 23 are sequentially formed on an oxygen-doped n-type GaN substrate 21 having a (0001) Ga surface as a surface by MOCVD. Let it grow. Next, in the fourth embodiment, the MQW active layer 25 is formed by alternately growing four barrier layers 25a and three well layers 25b immediately above the n-type cladding layer 23. Thereafter, a protective layer 26, a light guide layer 27, a p-type cladding layer 28, and an undoped contact layer 29 are sequentially grown on the MQW active layer 25. The substrate temperature and the introduced gas when growing the n-type GaN layer 22, the n-type cladding layer 23, the MQW active layer 25, the protective layer 26, the light guide layer 27, the p-type cladding layer 28, and the undoped contact layer 29 are as follows: These are the same as the substrate temperature and the introduced gas of the second embodiment, respectively.

Next, as shown in FIG. 16, as in the second embodiment, a striped p-side electrode 31 is formed near the center of the undoped contact layer 29 using a vacuum deposition method and a lithography technique. Thereafter, the undoped contact layer 29 and a part of the p-type cladding layer 28 are removed by using the p-side electrode 31 as a mask by a reactive ion beam etching method or the like, so that the current path as shown in FIG. A convex ridge serving as a region is formed.

Finally, as shown in FIG. 14, similarly to the second embodiment, an insulating film 30 is formed using a plasma CVD method so as to cover the surface of the p-type cladding layer 28 and the side surface of the undoped contact layer 29. After that, the p-side pad electrode 32 is formed so as to cover the surface of the insulating film 30 and the surface of the p-side electrode 31. Thereafter, the n-type GaN substrate 21 is polished to a predetermined thickness, and then the n-side electrode 33 is formed on the back surface of the n-type GaN substrate 21 by using a vacuum deposition method, thereby obtaining the fourth embodiment. Is formed.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description of the embodiments, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

For example, in the first to fourth embodiments, the sapphire substrate and the n-type GaN substrate are used as the substrate, but the present invention is not limited to this, and the spinel substrate, the Si substrate, the SiC substrate, the GaAs substrate, the GaP A substrate, an InP substrate, a quartz substrate, a ZrB ₂ substrate, or the like may be used.

In the first to fourth embodiments, the undoped contact layer made of a single layer of undoped InGaN is formed. However, the present invention is not limited to this. As shown in FIG. Alternatively, the p-side contact layer 49 having a multilayer structure such as a superlattice structure including a plurality of undoped layers including at least one layer of undoped InGaN having a larger band gap may be formed. The p-side contact layer 49 is an example of the “undoped contact layer” of the present invention. The structure of the superlattice of this case, an undoped _{In Y Ga 1-Y N (} X>Y> 0 having a thickness of undoped _{an In} X _Ga layer and several nm consisting of _1-X N having a thickness of several nm ), And a layered structure of a layer made of undoped InGaN having a thickness of several nm and a layer made of undoped AlGaN (including GaN) having a thickness of several nm.

In the first to fourth embodiments, the layers are stacked such that the surface of each layer of the nitride-based semiconductor is the (0001) plane. However, the present invention is not limited to this, and the surface of each layer of the nitride-based semiconductor may be You may laminate | stack so that it may become another direction. For example, the layers may be stacked such that the surface of each layer of the nitride-based semiconductor is a (H, K, -HK, 0) plane such as a (1-100) or (11-20) plane. In this case, since no piezo electric field is generated in the MQW active layer, it is possible to suppress a decrease in the recombination probability of holes and electrons due to the inclination of the energy band of the well layer. As a result, the luminous efficiency of the MQW active layer can be improved.

In the first to fourth embodiments, examples in which a multiple quantum well (MQW) structure is used as an active layer have been described. However, the present invention is not limited to this, and a single-layer or single-layer thick film having no quantum effect is used. Similar effects can be obtained even with a single quantum well structure.

In the first to fourth embodiments, the undoped contact layer made of InGaN is provided on the p-side. However, the present invention is not limited to this, and the undoped contact layer made of GaN is provided on the p-side. Is also good. For example, when the undoped contact layer made of GaN is provided instead of the undoped contact layer made of InGaN in the structure of the nitride-based semiconductor laser device according to the second embodiment, the structure becomes as shown in FIG. That is, unlike the second embodiment, the undoped contact layer 59 made of GaN is formed on the projection of the p-type cladding layer 28. Thus, even when the undoped contact layer 59 made of GaN is provided, the same effects as those of the second embodiment, such as suppression of light absorption, can be obtained.

Further, in the second embodiment, the n-type light guide layer 24 and the light guide layer 27 having the same thickness (about 100 nm) are provided on the n-side and the p-side, respectively. Alternatively, as shown in FIG. 20, an n-type light guide layer 64 having a smaller thickness (for example, about 50 nm) than the thickness of the light guide layer 27 may be provided. In this case, the same effect as in the fourth embodiment in which the n-type light guide layer is not provided can be obtained. That is, since the thickness of the n-type light guide layer 64 is smaller than the thickness of the p-side light guide layer 27, the region where the light intensity is high is shifted to the p-side, so that the light absorption in the n-type cladding layer 23 is suppressed. Is done. In this case, similarly to the fourth embodiment, the undoped contact layer 29 in which impurity levels and crystal defects due to doping are not formed does not increase light absorption. The effect of improving efficiency is increased.

FIG. 1 is a cross-sectional view illustrating a nitride-based semiconductor light-emitting diode device (blue LED chip) according to a first embodiment of the present invention. FIG. 2 is a top view of the nitride-based semiconductor light-emitting diode device according to the first embodiment shown in FIG. 2 is a graph showing the contact resistance between the p-side electrode and the contact layer when the material and thickness of the contact layer are changed in the nitride-based semiconductor light-emitting diode device according to the first embodiment shown in FIG. FIG. 3 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the first embodiment shown in FIGS. 1 and 2. FIG. 3 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the first embodiment shown in FIGS. 1 and 2. FIG. 5 is a sectional view showing a nitride-based semiconductor laser device (LD chip) according to a second embodiment of the present invention. FIG. 7 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. FIG. 7 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. FIG. 7 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. FIG. 9 is a cross-sectional view illustrating a nitride-based semiconductor light-emitting diode device (blue LED chip) according to a third embodiment of the present invention. FIG. 11 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the third embodiment shown in FIG. FIG. 11 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the third embodiment shown in FIG. FIG. 11 is a cross-sectional view for explaining a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the third embodiment shown in FIG. FIG. 11 is a sectional view showing a nitride-based semiconductor laser device (LD chip) according to a fourth embodiment of the present invention. FIG. 15 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. FIG. 15 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. FIG. 15 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. FIG. 9 is a cross-sectional view illustrating a nitride-based semiconductor laser device (LD chip) according to a modification of the second embodiment. FIG. 9 is a cross-sectional view illustrating a nitride-based semiconductor laser device (LD chip) according to a modification of the second embodiment. FIG. 9 is a cross-sectional view illustrating a nitride-based semiconductor laser device (LD chip) according to a modification of the second embodiment.

Explanation of reference numerals

1,41 sapphire substrate (substrate)
4 n-type contact layer (first nitride-based semiconductor layer)
5, 25 MQW active layer (active layer)
7, 28 p-type cladding layer (second nitride semiconductor layer, cladding layer)
8, 29, 59 Undoped contact layer 9, 31 p-side electrode (electrode)
21 n-type GaN substrate (substrate)
22 n-type GaN layer (first nitride-based semiconductor layer)
23 n-type cladding layer (first nitride-based semiconductor layer)
24, 64 n-type light guide layer 27 light guide layer (third nitride-based semiconductor layer)
49 p-side contact layer (undoped contact layer)

Claims (10)

A first conductivity type first nitride-based semiconductor layer formed on a substrate;
An active layer formed on the first nitride-based semiconductor layer and including the nitride-based semiconductor layer;
A second conductivity type second nitride-based semiconductor layer formed on the active layer;
An undoped contact layer formed on the second nitride-based semiconductor layer;
A nitride-based semiconductor light-emitting device comprising: an electrode formed on the undoped contact layer. The nitride semiconductor light emitting device according to claim 1, wherein the band gap of the undoped contact layer is smaller than the band gap of the second nitride semiconductor layer. The first conductivity type first nitride-based semiconductor layer is an n-type first nitride-based semiconductor layer,
The nitride-based semiconductor light-emitting device according to claim 1, wherein the second conductivity-type second nitride-based semiconductor layer is a p-type second nitride-based semiconductor layer. 4. The nitride-based semiconductor light-emitting device according to claim 1, wherein the undoped contact layer has a thickness of 1 nm or more and 10 nm or less. 5. 5. The nitride-based semiconductor light-emitting device according to claim 1, wherein the undoped contact layer has a band gap larger than a band gap of the active layer. 6. The nitride semiconductor light emitting device according to claim 1, wherein the undoped contact layer contains InGaN. 7. 7. The nitride-based semiconductor light-emitting device according to claim 1, wherein the undoped contact layer includes a single undoped nitride-based semiconductor layer. 8. An undoped third nitride formed at least between the active layer and the second-conductivity-type second nitride-based semiconductor layer and formed of a nitride-based semiconductor having a smaller band gap than the second nitride-based semiconductor layer. The nitride-based semiconductor light-emitting device according to claim 1, further comprising a nitride-based semiconductor layer. The undoped third nitride-based semiconductor layer is formed between the active layer and the first conductivity-type first nitride-based semiconductor layer and the second conductivity-type second nitride-based semiconductor layer. The nitride-based semiconductor light-emitting device according to claim 8, wherein the nitride-based semiconductor light-emitting device is formed only between the active layer and the second nitride-based semiconductor layer. A fourth nitride-based semiconductor layer formed between the active layer and the first conductivity-type first nitride-based semiconductor layer;
The nitride-based semiconductor light-emitting device according to claim 8, wherein the fourth nitride-based semiconductor layer has a thickness smaller than a thickness of the third nitride-based semiconductor layer.

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