JP4162560B2 - Nitride semiconductor light emitting device - Google Patents

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.

In recent years, nitride-based semiconductor light-emitting diode elements (LEDs) and nitride-based semiconductors using nitride-based semiconductors composed of In _X Al _Y Ga _1- XYN (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) are used. Nitride-based semiconductor light emitting devices such as semiconductor laser devices (LD) have been put into practical use.

The basic structure of a conventional nitride-based semiconductor light-emitting device is that an n-type nitride-based semiconductor layer made of n-type Al _Y Ga ₁ -YN (0 ≦ Y ≦ 1) and In _X Ga ₁ are formed on a substrate. _{-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 It is a structure. Usually, 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 are further provided. 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 the active layer.

  Each of the n-type and p-type nitride semiconductor layers of the nitride-based semiconductor light-emitting element described above is doped 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 essential to suppress light absorption in each nitride-based semiconductor layer. However, since the impurity doped to obtain the p-type nitride semiconductor has a low activation rate, conventionally, a large amount of impurity is doped to obtain the p-type nitride semiconductor having a predetermined carrier concentration. There was a need to do. In this case, the light absorption is increased in the p-type contact layer and the p-type light guide layer having a small band gap due to the impurity level formed by introducing a large amount of impurities into the p-type nitride semiconductor. was there. In addition, there is a disadvantage that light absorption increases due to crystal defects generated by doping a large amount of impurities.

Therefore, conventionally, a nitride-based semiconductor laser device that can reduce light absorption caused by impurity doping by forming an undoped light guide layer on the active layer instead of the p-type light guide layer has been proposed. (For example, refer nonpatent literature 1).
“Technical Research Report of the Institute of Electronics, Information and Communication Engineers” IEICE, June 15, 2002, pp. 63-66

  However, the proposed conventional nitride-based semiconductor laser device does not take measures 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 achieve ohmic contact with the p-side electrode. Thereby, even if light absorption in the undoped light guide layer described above is reduced, it is difficult to suppress 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 light emission efficiency of the nitride-based semiconductor laser device. In addition, in a nitride semiconductor light emitting diode element in which light is emitted through the p type contact layer, if the light absorption in the p type contact layer is increased, the light emission characteristics of the nitride semiconductor light emitting diode element are more greatly affected. There is a problem of becoming.

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

  However, in the technique disclosed in the above Japanese Patent Application Laid-Open No. 2001-60720, in the contact layer, from the nitride-based semiconductor layer doped with impurities arranged on both sides (upper and lower) of the undoped nitride-based semiconductor layer, the undoped Impurities may diffuse into the nitride-based semiconductor layer. In this case, since impurity levels are 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 composed of a laminated structure of an undoped nitride semiconductor layer and a p-type nitride semiconductor layer doped with impurities, the nitride semiconductor There is a problem that it is difficult to improve the light emission efficiency of the light emitting element.

  Further, as a method for suppressing light absorption in the p-type contact layer, a p-type nitride semiconductor layer having a large band gap is used as the p-type contact layer, thereby making it difficult for light absorption in the p-type contact layer to occur. Can be considered. However, since the barrier at the interface between the p-side electrode and the p-type contact layer is increased by increasing the band gap of the p-type contact layer, good ohmic contact can be achieved between the p-side electrode and the p-type contact layer. It becomes difficult to realize. As a result, the luminous efficiency is further lowered 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 the light emission efficiency by reducing the light absorption loss in the contact layer. A nitride-based semiconductor light-emitting device is provided.

Means for Solving the Problems and Effects of the Invention

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

  In the nitride-based semiconductor device according to this aspect, by providing the undoped contact layer as described above, since no impurity level is formed in the undoped contact layer, light absorption caused by the impurity level is prevented. Can do. Further, since the undoped contact layer has no crystal defects due to impurity doping, the undoped contact layer has good crystallinity. For this reason, the light absorption resulting from the crystal defect of an undoped contact layer can also be suppressed. Thereby, the light absorption loss in the undoped contact layer can be reduced, so that the light emission efficiency can be improved.

  In the nitride-based semiconductor light-emitting device according to the aforementioned aspect, the band gap of the undoped contact layer is preferably smaller than the band gap of the second nitride-based semiconductor layer. If comprised in this way, since the energy barrier in the interface of an undoped contact layer and an electrode becomes small, it can make it easy to implement | achieve ohmic contact with an undoped contact layer and an electrode. Thereby, the luminous efficiency can be further improved and the drive voltage can be lowered.

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

  In the nitride semiconductor light emitting device according to the above aspect, the undoped contact layer preferably has a thickness of 1 nm or more and 10 nm or less. If comprised in this way, since the contact resistance between an undoped contact layer and an electrode can be reduced, a favorable ohmic contact can be obtained between an undoped contact layer and an electrode. In addition, the resistance of the undoped contact layer can be reduced.

  In the nitride semiconductor light emitting device according to the aforementioned aspect, the undoped contact layer preferably has a band gap larger than the band gap of the active layer. When the active layer is composed 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 (base levels) formed in the conduction band and the valence band. To do. If comprised in this way, the light absorption in an undoped contact layer can be reduced easily. 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 semiconductor layer.

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

  In the nitride-based semiconductor light-emitting device according to the aforementioned aspect, the band gap is preferably formed between at least the active layer and the second-conductivity-type second nitride-based semiconductor layer and more than the second nitride-based semiconductor layer. An undoped third nitride semiconductor layer made of a small nitride semiconductor. With this configuration, light emission characteristics such as light confinement characteristics can be controlled by the third nitride semiconductor layer, and light absorption in the third nitride semiconductor layer can also be suppressed.

  In this case, preferably, the undoped third nitride semiconductor layer is between the active layer and the first conductivity type first nitride semiconductor layer and the second conductivity type second nitride semiconductor layer. Among these, it is formed only between the active layer and the second nitride semiconductor layer. If comprised in this way, since the high intensity | strength area | region of the light produced | generated in an active layer will shift | deviate to the 2nd nitride type semiconductor layer side, the light absorption in the 1st conductivity type 1st nitride type semiconductor layer will be suppressed. Is done. In this case, even if the region with high light intensity is shifted to the second nitride semiconductor layer side, no impurity levels or crystal defects are formed in the undoped contact layer on the second nitride semiconductor layer. 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 semiconductor layer formed between the active layer and the first conductivity type first nitride semiconductor layer, and the fourth nitride semiconductor layer includes a third nitride semiconductor layer. The film thickness is smaller than that of the nitride-based semiconductor layer. If comprised in this way, since the high intensity | strength area | region of the light produced | generated in an active layer will shift | deviate to the 2nd nitride type semiconductor layer side, the light absorption in the 1st conductivity type 1st nitride type semiconductor layer will be suppressed. Is done. In this case, even if the region with high light intensity is shifted to the second nitride semiconductor layer side, no impurity levels or crystal defects are formed in the undoped contact layer on the second nitride semiconductor layer. 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 semiconductor light emitting device according to the aforementioned aspect, the undoped contact layer may contain GaN.

  In the nitride semiconductor light emitting device according to the aforementioned aspect, the second conductivity type second nitride semiconductor layer preferably 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 convex portion of the second conductivity type cladding layer, and the convex portion of the second conductivity type cladding layer and the undoped contact layer. If comprised in this way, the ridge part as a current path area | region can be formed easily.

  In the nitride semiconductor light emitting device according to the aforementioned aspect, preferably, an undoped fifth nitride semiconductor layer formed between the substrate and the first conductivity type first nitride semiconductor layer is further provided. Prepare. According to this structure, the undoped fifth nitride-based semiconductor layer does not have crystal defects due to impurity doping, and thus each nitride-based semiconductor layer (first layer) sequentially formed on the fifth nitride-based semiconductor layer. The occurrence of crystal defects in the first nitride semiconductor layer, the active layer, the second nitride semiconductor layer, and the undoped contact layer can be further suppressed. Thereby, each nitride-based semiconductor layer (first nitride-based semiconductor layer, active layer, second nitride-based semiconductor layer, and undoped contact layer) with further reduced crystal defects can be formed. The resulting light absorption can be further suppressed. As a result, a nitride-based semiconductor light-emitting element with higher luminous efficiency can be formed.

  In this case, preferably, the undoped fifth nitride-based semiconductor layer is composed of a low-dislocation nitride-based semiconductor formed by selective lateral growth. With this configuration, it is possible to easily obtain a low dislocation fifth nitride-based semiconductor layer in which not only crystal defects due to impurity doping but also other crystal defects are reduced. Further suppressing the occurrence of crystal defects in each nitride-based semiconductor layer (first nitride-based semiconductor layer, active layer, second nitride-based semiconductor layer, and undoped contact layer) sequentially formed on the physical-based semiconductor layer be able to.

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

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

  In this case, preferably, the second conductivity type second nitride semiconductor layer includes a second conductivity type second nitride semiconductor layer made of AlGaN, and the undoped third nitride semiconductor layer is GaN. And an undoped third nitride-based semiconductor layer. If comprised in this way, the band gap of a 3rd nitride type semiconductor layer can be easily made smaller than the band gap of a 2nd nitride type semiconductor layer.

  In the nitride-based semiconductor light-emitting device according to the aforementioned aspect, the active layer preferably includes an active layer made of a nitride-based semiconductor containing In, and is formed on the active layer, and In from the active layer is desorbed. A protective layer made of a nitride-based semiconductor is further provided to prevent this. According to this structure, since the protective layer prevents In from being separated from the active layer, it is possible to prevent deterioration of the crystal of the active layer.

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

  In this case, preferably, the substrate includes an insulating substrate. If comprised in this way, the nitride-type semiconductor light-emitting device which has an insulating substrate can be obtained easily by providing an electrode on the contact layer which also has a function as a clad layer.

  In the nitride semiconductor light emitting device according to the aforementioned aspect, the electrode on the undoped contact layer is preferably formed in a comb shape. If comprised in this way, light can be discharge | released through the electrode formed in the comb shape.

  In the above case, preferably, the semiconductor device further includes a plurality of mask layers having overhang portions formed on the substrate at predetermined intervals, and the undoped fifth nitride-based semiconductor layer is formed using selective lateral growth. The mask layer is formed so as to be embedded. With this configuration, the triangular fifth nitride-based semiconductor layer is formed in the vicinity of the center between the mask layers from the initial stage of growth, and between the mask layers below the overhang portion of the mask layer. A triangular fifth nitride semiconductor layer smaller than the triangular fifth nitride semiconductor layer located near the center is formed. For this reason, since the fifth nitride-based semiconductor layer grows laterally from the initial stage of growth, dislocations generated in the fifth nitride-based semiconductor layer are bent laterally from the initial stage of growth. As a result, a fifth nitride-based semiconductor layer with a reduced thickness and a reduced dislocation density can be formed.

  In the nitride-based semiconductor light-emitting device according to the aforementioned aspect, the substrate is preferably a first conductivity type GaN substrate. If comprised in this way, the light emission efficiency of the nitride-type semiconductor light-emitting device which has a 1st conductivity type GaN board | substrate can be improved easily.

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

(First embodiment)
FIG. 1 is a cross-sectional view showing 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 shown in FIG. It is a top view of a light emitting diode element. First, with reference to FIGS. 1 and 2, the structure of the nitride-based semiconductor light-emitting diode device according to the first embodiment will be described.

  In the nitride-based 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 the (0001) plane of a sapphire substrate 1. Yes. The sapphire substrate 1 is an example of the “substrate” and “insulating substrate” in the present invention. On the low-temperature buffer layer 2, a high-temperature buffer layer 3 made of undoped GaN having a thickness of about 1 μm is formed. On the high temperature buffer layer 3, an n-type contact layer 4 made of n-type GaN doped with Si and having a thickness of about 5 μm is formed. The n-type contact layer 4 is formed in a convex shape by removing a part of the region. The n-type contact layer 4 also has a function as an n-type cladding layer. The n-type contact layer 4 is an example of the “first nitride semiconductor layer” in the present invention.

Further, six undoped In _0.15 Ga _0.85 N barrier layers 5 a having a film 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 n-type contact layer 4 on the convex portion. An MQW active layer 5 having a multiple quantum well (MQW) structure in which well layers 5b made of five undoped In _0.35 Ga _0.65 N having a thickness are alternately stacked is formed. The MQW active layer 5 is an example of the “active layer” in the present invention. A protective layer 6 made of undoped GaN having a thickness of about 10 nm is formed on the MQW active layer 5. The protective layer 6 has a function of preventing the crystal of the MQW active layer 5 from deteriorating by preventing the In from the MQW active layer 5 from desorbing.

Here, in the first embodiment, the protective layer 6 has a film 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 cladding 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” in the present invention. In the first embodiment, an 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 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 cladding layer 7 made of Al _0.05 Ga _0.95 N, and undoped In _{0. It} is larger than the band gap of the MQW active layer 5 made 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 (base levels) formed in the conduction band and the valence band, and includes In _0.15 Ga _0.85 N and In 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 made of In _0.15 Ga _0.85 N.
Further, on the upper surface of the undoped contact layer 8, a comb-like 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 the bottom to the top. 9 is formed. The p-side electrode 9 is an example of the “electrode” in 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-based 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 the contact resistance when a p-type GaN layer doped with Mg having a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ is used as a contact layer. . Note that p-type GaN doped with Mg is a standard material used for the contact layer.

As shown in FIG. 3, 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, the contact resistance of the undoped contact layer 8 is doped with Mg. It can be seen that the contact resistance of the p-type contact layer made of p-type GaN can be approached. It can also 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 made smaller than that of the undoped contact layer made of undoped GaN. Considering the above points, in the first embodiment, the undoped contact layer 8 made of undoped In _0.15 Ga _0.85 N having a film thickness of about 1 nm to about 10 nm is used. It can be seen that an undoped contact layer made of undoped Al _0.05 Ga _0.95 N has a large contact resistance even when the film thickness is about 1 nm to about 10 nm. It can also 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 the contact resistance of the p-type contact layer made of p-type GaN.

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

  In the first embodiment, as described above, by providing the undoped contact layer 8, no impurity level is formed in the undoped contact layer 8, so that light absorption due to the impurity level can be prevented. Moreover, since the undoped contact layer 8 has no crystal defects due to impurity doping, the undoped contact layer 8 has good crystallinity. For this reason, the light absorption resulting from the crystal defect of 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 light emission efficiency of the nitride-based semiconductor light-emitting diode element can be improved.

  In the first embodiment, as described above, the energy 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 light emission efficiency of the nitride-based semiconductor light-emitting diode element can be further improved, and the drive voltage can be lowered.

  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, a good ohmic contact can be obtained between the undoped contact layer 8 and the p-side electrode 9. In addition, the resistance of the undoped contact layer 8 can be reduced.

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

  4 and 5 are cross-sectional views for explaining a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the first embodiment shown in FIGS. A manufacturing process for the nitride-based semiconductor light-emitting diode device according to the first embodiment is now 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 the sapphire substrate 1 using a MOVPE method (Metal Organic Vapor Phase Epitaxy). The MQW active layer 5, the protective layer 6, the p-type cladding layer 7 and the undoped contact layer 8 are grown sequentially.

Specifically, with the sapphire substrate 1 held 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 made of trimethylgallium (TMGa), a low-temperature buffer layer 2 made of AlGaN having a thickness of about 10 nm is grown on the (0001) plane of the sapphire substrate 1.

Next, a carrier gas composed of H ₂ and N ₂ (H ₂ : about 50%) and a source gas composed of NH ₃ and TMGa are used with the substrate temperature maintained at a single crystal growth temperature of about 1150 ° C. Thus, the 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 maintained at a single crystal growth temperature of about 1150 ° C., a carrier gas composed of H ₂ and N ₂ (H ₂ : about 50%), 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

Next, with the substrate temperature maintained 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 , triethyl gallium (TEGa) And 6 undoped In _0.15 Ga having a film thickness of about 5 nm on the n-type contact layer 4 at a growth rate of about 0.4 nm / s using a source gas composed of trimethylindium (TMIn). Barrier layers 5a made of _0.85 N and five undoped In _0.35 Ga _0.65 N well layers 5b having a thickness of about 5 nm are grown alternately. Thereby, the MQW active layer 5 is formed on the 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, with the substrate temperature maintained at a single crystal growth temperature of about 1150 ° C., a carrier gas composed of H ₂ and N ₂ (H ₂ : about 1% to about 3%) and NH ₃ , TMGa and TMAl And having a film thickness of about 0.15 μm on the protective layer 6 at a growth rate of about 3 μm / h, using a raw material gas and a dopant gas made of cyclopentadienylmagnesium (Cp ₂ Mg), Growing a p-type cladding layer 7 made of p-type Al _0.05 Ga _0.95 N doped with Mg having a doping amount of about 3 × 10 ¹⁹ cm ⁻³ and a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ Let

At this time, Mg as an acceptor can be activated by lowering 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, with the substrate temperature maintained 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 , TEGa and TMIn And an 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. Grow 8

  Then, as shown in FIG. 5, one of 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 is formed by using a reactive ion beam etching (RIBE) method or the like. A partial region of the n-type contact layer 4 is exposed by removing the partial region.

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

  Thereafter, the p-side electrode 9 and the n-side electrode 11 are brought into ohmic contact with the undoped contact layer 8 and the n-type contact layer 4, respectively, by heat treatment at a temperature of about 600 ° C.

  Finally, element separation is performed using a method such as scribing, dicing, and braking so as to form a substantially square chip having a side length of about 400 μm, for example. Thus, the nitride-based semiconductor light-emitting diode element of the first embodiment is formed.

  Furthermore, 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), a resin is coated at around 200 ° C. so as to cover them. An LED lamp including the blue LED chip of the first embodiment may be manufactured by curing at a temperature.

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

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 a conductive n-type GaN substrate 21 having a (0001) Ga surface as a surface and doped with oxygen. 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 having a thickness of about 1 μm is formed. The n-type GaN substrate 21 is an example of the “substrate” in the present invention, and the n-type GaN layer 22 and the n-type cladding layer 23 are examples of the “first nitride semiconductor layer” in the present invention.

On the n-type cladding layer 23, an n-type light guide layer 24 made of n-type GaN having a thickness of about 100 nm is formed. On the n-type light guide layer 24, four undoped In _0.05 Ga _0.95 N barrier layers 25a having a thickness of about 15 nm and three undoped In ₀ layers having a thickness of about 4 nm are formed. 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 is formed.

Here, in the second embodiment, the protective layer 26 made of undoped Al _0.3 Ga _0.7 N having a thickness of about 20 nm is formed on the MQW active layer 25. The protective layer 26 has a function of preventing the crystal of the MQW active layer 25 from deteriorating by preventing the In from the MQW active layer 25 from desorbing. 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 cladding 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” in the present invention.

On the light guide layer 27, p-type Al _0.15 Ga doped with Mg having a film thickness of about 280 nm and a stripe-shaped convex portion having a width of about 1.5 μm near the center. _A p-type cladding layer 28 made 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” in the present invention.

Here, in the second embodiment, undoped In _0.05 Ga _0.95 N having a film thickness of about 5 nm on the convex portion of the p-type cladding layer 28 made of p-type Al _0.15 Ga _0.85 N. An undoped contact layer 29 made of is formed. The convex portion of the p-type cladding layer 28 and the undoped contact layer 29 constitute a ridge portion that becomes 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 (base levels) formed in the conduction band and the valence band, and includes In _0.05 Ga _0.95 N and In 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 made 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. On the undoped contact layer 29, a p-side electrode 31 composed of a Pd film, a Pt film, and an Au film is formed from bottom to top. The p-side electrode 31 is an example of the “electrode” in the present invention. 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 close to 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 due to impurity doping. For this reason, the light absorption resulting from the crystal defect of the undoped contact layer 29 can also be suppressed. Thereby, the light absorption loss in the undoped contact layer 29 can be reduced, so that the light emission efficiency of the nitride-based semiconductor laser device can be improved.

  In the second embodiment, as described above, 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. 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 p-type cladding layer 28 is formed of p-type Al _0.15 Ga _0.85 N doped with Mg, thereby reducing the band gap of the p-type cladding layer 28. Since it can be easily increased, light absorption in the p-type cladding layer 28 can be easily reduced. Furthermore, 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 of 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, and light absorption in the light guide layer 27 can also be suppressed.

  7 to 9 are cross-sectional views for explaining a manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. A manufacturing process for the nitride-based semiconductor laser device according to the second embodiment is now described with reference to FIGS.

  First, as shown in FIG. 7, an n-type GaN layer 22, an n-type cladding layer 23, an n-type cladding layer 23 are formed on an n-type GaN substrate 21 doped with oxygen having a (0001) Ga surface as a surface by using the MOVPE method. A type optical guide layer 24, an MQW active layer 25, a protective layer 26, an optical 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 held 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 made of SiH ₄ and having a growth rate of about 3 μm / h, a film thickness of about 1 μm is formed on the n-type GaN substrate 21 doped with oxygen having the (0001) Ga surface as a surface. An n-type GaN layer 22 doped with Si is grown.

Next, with the substrate temperature maintained at a growth temperature of about 1150 ° C., a carrier gas composed of H ₂ and N ₂ (H ₂ : about 50%), a source gas composed of NH ₃ , TMGa and TMAl, and SiH using a dopant gas comprising _4, at a growth rate of about 3 [mu] m / h, on the n-type GaN layer 22, n-type Si doped with a thickness of about 1μm _Al 0.15 _{Ga 0.85} n An 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, in a state where the substrate temperature is maintained at a growth temperature of about 850 ° C., a carrier gas (H ₂ : about 1% to about 5%) made of H ₂ and N ₂ and a raw material made of NH ₃ , TEGa and TMIn And a barrier layer 25a made of four undoped In _0.05 Ga _0.95 N having a thickness of about 15 nm on the n-type light guide layer 24 at a growth rate of about 0.4 nm / s. And three well layers 25b made of three undoped In _0.1 Ga _0.9 N having a thickness of about 4 nm are alternately grown. Thereby, 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, with the substrate temperature maintained at a growth temperature of about 1150 ° C., a carrier gas consisting of H ₂ and N ₂ (H ₂ : about 1% to about 3%), a source gas consisting of NH ₃ and TMGa, The light guide layer 27 made of undoped GaN having a thickness of about 100 nm is grown on the protective layer 26 at a growth rate of about 3 μm / h. Furthermore, a source gas made of TMAl and a dopant gas made of Cp ₂ Mg were added, and Mg having a film 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, Mg as an acceptor can be activated by lowering the H ₂ composition of the carrier gas to about 1% to about 3%, so that the p-type cladding layer 28 having a high carrier concentration can be obtained. it can.

Next, in a state where the substrate temperature is maintained at a growth temperature of about 850 ° C., a carrier gas (H ₂ : about 1% to about 5%) made of H ₂ and N ₂ and a raw material made 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 central portion on the undoped contact layer 29 from the bottom to the 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.

  Thereafter, as shown in FIG. 9, a partial region of the undoped contact layer 29 and the p-type cladding layer 28 is removed using a reactive ion beam etching method or the like using the p-side electrode 31 as a mask. Thereby, 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 with a plasma CVD method (Chemical Vapor Deposition). After forming the insulating film (not shown) made of ₂ , the insulating film on the surface of the p-side electrode 31 is removed, whereby the insulating film 30 having a shape as shown in FIG. 6 is obtained. Then, 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.

  Finally, after polishing the n-type GaN substrate 21 to a predetermined thickness (for example, about 100 μm), it is applied on the back surface of the n-type GaN substrate 21 and on the back surface of the n-type GaN substrate 21 by vacuum evaporation. From the near side, an n-side electrode 33 composed of a Ti film, a Pt film, and an Au film is formed. In this way, the nitride semiconductor laser element 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 an undoped GaN layer 44 having a lower dislocation 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 in the first embodiment.

  That is, in the nitride-based semiconductor light-emitting diode device according to the third embodiment, the cross section made of SiN having a film thickness of about 10 nm to about 1000 nm on the (0001) plane of the sapphire substrate 41 is reversed as shown in FIG. A mesa-shaped (inverted trapezoidal) mask layer 42 is formed in a stripe shape (elongated shape) with a period of about 7 μm. The sapphire substrate 41 is an example of the “substrate” and “insulating substrate” in the present invention. The mask layer 42 is formed such that the shortest distance between adjacent mask layers 42 is smaller than the width of 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 on the sapphire substrate 41 exposed between the mask layers 42. 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 be embedded between the mask layers 42 using selective lateral growth. Yes. The undoped GaN layer 44 is an example of the “fifth nitride semiconductor layer” in the present invention.

  Then, the n-type contact layer 4, MQW active layer 5, protective layer 6, p-type cladding layer 7, undoped contact layer 8, p-side electrode 9, p-side pad electrode 10 and n formed on the undoped GaN layer 44. The thickness and composition of the side electrode 11 are the same as those in the first embodiment shown in FIG.

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

  The remaining effects of the third embodiment are similar to those of the first embodiment.

  11 to 13 are cross-sectional views illustrating a manufacturing process of the nitride-based semiconductor light-emitting diode device according to the third embodiment shown in FIG. A manufacturing process for the nitride-based semiconductor light-emitting diode device according to the third embodiment is now described with reference to FIGS.

  First, as shown in FIG. 11, after a SiN film (not shown) is formed 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 stripe-shaped mask layer 42. The mask layer 42 is formed in an inverted mesa shape (inverted trapezoidal shape) so as to have an overhang portion 42a. Moreover, it is preferable to form the opening part of the mask layer 42 in the [11-20] direction of the sapphire substrate 41 or the [1-100] direction of the sapphire substrate 41, for example. 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

  Next, using the MOVPE method, the undoped GaN layer 44 (see FIG. 13) is laterally grown 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. Let In this case, the undoped GaN layer 44 is first grown upward on the exposed upper surface of the low-temperature buffer layer 43. As a result, as shown in FIG. 12, an undoped GaN layer 44a having a facet structure with a triangular cross section 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 that of the undoped GaN layer 44a is formed below the overhang portion 42a of the mask layer 42. Further, when the growth of the facet composed of the undoped GaN layers 44a and 44b progresses, the undoped GaN layers 44a and 44b grow in the lateral direction and merge and grow on the mask layer 42 as well. As a result, as shown in FIG. 13, an undoped GaN layer 44 made of a continuous film having a flat top surface and a film thickness of about 2 μm is formed.

Thus, since the undoped GaN layer 44 grows laterally from the initial stage of growth, dislocations generated in the undoped GaN layer 44 are bent laterally from the early stage of growth. Thereby, the undoped GaN layer 44 having a thinner thickness and a reduced dislocation density of about 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 protective layer 6, and the p-type cladding layer as shown in FIG. 10 are formed on the undoped GaN layer 44. 7 and the undoped contact layer 8 are sequentially formed, and then a partial region of the undoped contact layer 8 is removed from the n-type contact layer 4. Then, the p-side electrode 9 and the p-side pad electrode 10 are sequentially formed on the undoped contact layer 8. Thereafter, the n-side electrode 11 is formed on the exposed surface of the n-type contact layer 4.

  Finally, element separation is performed using a method such as scribing, dicing, and braking so as to form a substantially square chip having a side length of about 400 μm, for example. In this way, the nitride-based semiconductor light-emitting diode element of the third embodiment is formed.

(Fourth embodiment)
FIG. 14 is a cross-sectional view showing a nitride-based semiconductor laser device (LD chip) according to the fourth embodiment of the present invention. With reference to FIG. 14, 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. Other configurations are the same as those of the second embodiment.

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

  Here, in the fourth embodiment, an MQW in which four barrier layers 25a and three well layers 25b having the same film thickness and composition as in the second embodiment are alternately stacked immediately above 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.

  The film 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 film thickness and composition of the n-side electrode 33 formed on the back surface of the n-type GaN substrate 21 are also the same as those in 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 in the MQW active layer 25 is high. 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, impurity levels and crystal defects due to doping are not formed in the undoped contact layer 29, so that light absorption does not increase. As a result, the effect of improving the light emission efficiency of the nitride-based semiconductor laser device is increased.

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

  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. A manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment is now 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. Grow. Next, in the fourth embodiment, the MQW active layer 25 is formed by alternately growing the four barrier layers 25 a and the three well layers 25 b directly on 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: Each is the same as the substrate temperature and the introduced gas in the second embodiment.

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

  Finally, as shown in FIG. 14, the insulating film 30 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 using the plasma CVD method as in the second embodiment. 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, after polishing the n-type GaN substrate 21 to a predetermined thickness, an n-side electrode 33 is formed on the back surface of the n-type GaN substrate 21 by using a vacuum evaporation method, thereby allowing the fourth embodiment. Nitride-based semiconductor laser elements are formed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

For example, in the first to fourth embodiments, the sapphire substrate and the n-type GaN substrate are used as the substrate. However, the present invention is not limited to this, and the spinel substrate, Si substrate, SiC substrate, GaAs substrate, 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, an undoped contact layer made of a single layer of undoped InGaN is formed. However, the present invention is not limited to this, and as shown in FIG. A 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 including undoped InGaN having a larger band gap may be formed. The p-side contact layer 49 is an example of the “undoped contact layer” in the present invention. The superlattice structure in this case includes a layer made of undoped In _X Ga _1-X N having a thickness of several nm and an undoped In _Y Ga _1-Y N having a thickness of several nm (X>Y> 0). 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.

  Moreover, in the said 1st-4th embodiment, it laminated | stacked so that the surface of each layer of a nitride-type semiconductor might become a (0001) plane, but this invention is not limited to this, The surface of each layer of a nitride-type semiconductor is You may laminate | stack so that it may become another direction. For example, the nitride semiconductor layers may be stacked such that the surface of each layer is a (H, K, -HK, 0) plane such as a (1-100) or (11-20) plane. In this case, since no piezoelectric field is generated in the MQW active layer, it is possible to suppress a decrease in the recombination probability between 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, an example in which a multiple quantum well (MQW) structure is used as the active layer has been described. However, the present invention is not limited to this, and the present invention is not limited to this. 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. Also good. For example, in the structure of the nitride-based semiconductor laser device according to the second embodiment, when an undoped contact layer made of GaN is provided instead of the undoped contact layer made of InGaN, the structure shown in FIG. 19 is obtained. That is, unlike the second embodiment, an undoped contact layer 59 made of GaN is formed on the convex portion of the p-type cladding layer 28. Thus, even when the undoped contact layer 59 made of GaN is provided, it is possible to obtain the same effects as those of the second embodiment, such as the ability to suppress light absorption.

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

1 is a cross-sectional view illustrating a nitride-based semiconductor light-emitting diode element (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. 1. 2 is a graph showing contact resistance between a p-side electrode and a 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. 5 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 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. It is sectional drawing which showed the nitride type semiconductor laser element (LD chip) by 2nd Embodiment of this invention. FIG. 7 is a cross-sectional view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the second embodiment shown in FIG. 6. FIG. 7 is a cross-sectional view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the second embodiment shown in FIG. 6. FIG. 7 is a cross-sectional view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the second embodiment shown in FIG. 6. It is sectional drawing which showed the nitride-type semiconductor light-emitting diode element (blue LED chip) by 3rd Embodiment of this 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. It is sectional drawing which showed the nitride type semiconductor laser element (LD chip) by 4th Embodiment of this invention. FIG. 15 is a cross-sectional view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 14. FIG. 15 is a cross-sectional view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 14. FIG. 15 is a cross-sectional view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 14. It is sectional drawing which showed the nitride type semiconductor laser element (LD chip) by the modification of 2nd Embodiment. It is sectional drawing which showed the nitride type semiconductor laser element (LD chip) by the modification of 2nd Embodiment. It is sectional drawing which showed the nitride type semiconductor laser element (LD chip) by the modification of 2nd Embodiment.

Explanation of symbols

1, 41 Sapphire substrate (substrate)
4 n-type contact layer (first nitride 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 semiconductor layer)
23 n-type cladding layer (first nitride semiconductor layer)
24, 64 n-type light guide layer 27 Light guide layer (third nitride semiconductor layer)
49 p-side contact layer (undoped contact layer)

Claims (11)

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 made of a nitride-based semiconductor layer;
A second conductivity type second nitride semiconductor layer formed on the active layer;
An undoped contact layer made of a nitride semiconductor formed on the second nitride semiconductor layer;
A nitride-based semiconductor light-emitting device comprising an electrode formed on the undoped contact layer ,
The undoped contact layer is a nitride-based semiconductor light-emitting device containing InGaN.   2. The nitride semiconductor light emitting device according to claim 1, wherein a band gap of the undoped contact layer is smaller than a band gap of the second nitride semiconductor layer. The first conductivity type first nitride semiconductor layer is an n-type first nitride semiconductor layer;
3. The nitride-based semiconductor light-emitting element 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 semiconductor light emitting device according to claim 1, wherein the second conductivity type second nitride semiconductor layer includes AlGaN. 5. The undoped contact layer has a 10nm or less thick than 1 nm, the nitride-based semiconductor light-emitting device according to any one of claims 1-4. The undoped contact layer has a band gap larger than the band gap of the active layer, the nitride-based semiconductor light-emitting device according to any one of claims 1-5. The undoped contact layer is composed of a nitride-based semiconductor layer of a single undoped nitride-based semiconductor light-emitting device according to any one of claims 1-6.   The nitride-based semiconductor light-emitting element according to claim 1, further comprising an electrode including a Pd film on an upper surface of the undoped contact layer. Undoped third nitridation formed of a nitride semiconductor formed between at least the active layer and the second conductivity type second nitride semiconductor layer and having a smaller band gap than the second nitride semiconductor layer. -BASED further comprising a semiconductor layer, a nitride-based semiconductor light-emitting device according to any one of claims 1-8. The undoped third nitride-based semiconductor layer is 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 element according to claim 9 , which is formed only between the active layer and the second nitride-based semiconductor layer. A fourth nitride semiconductor layer formed between the active layer and the first conductivity type first nitride semiconductor layer;
11. The nitride-based semiconductor light-emitting element according to claim 9, wherein the fourth nitride-based semiconductor layer has a thickness smaller than that of the third nitride-based semiconductor layer.

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