JP2006135215A - Process for fabricating semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fabricate a high luminance semiconductor light emitting element by locally reducing the residual quantity of oxygen in a furnace at the time of growth by a convenient method and bringing the concentration of oxygen being mixed in the active layer of a semiconductor light emitting element downward another step. <P>SOLUTION: A light reflecting layer 3 is formed by laying a plurality of pairs of low refractive index film and high refractive index film on a conductive semiconductor substrate 1 by using a vapor phase epitaxial growth system, a light emitting portion consisting of a first clad layer 4, an active layer 5 and a second clad layer 6 is formed on the light reflecting layer 3, and then a current dispersion layer 7 or an ITO film 10 is formed thereon thus fabricating a group III-V semiconductor light emitting element. The V/III ratio of material gas being supplied into a growth furnace at the time of growing the light reflecting layer 3 is set lower than the V/III ratio of material gas being supplied into a growth furnace at the time of growing the first clad layer 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor light emitting device, and more particularly to a method for manufacturing a group III-V high brightness semiconductor light emitting device in which the concentration of impurities contained in an active layer is reduced and the luminance is increased by a very simple method.

  In recent years, the demand for high-intensity semiconductor light-emitting devices manufactured using AlGaInP-based epitaxial wafers, particularly light-emitting diodes (LEDs), has increased significantly. Conventional applications include electronic bulletin boards and display lamps for consumer electronics, but the main applications in recent years are traffic signals, automotive lamps, etc. With the remarkable increase in brightness of LED lamps, the application range has been rapidly expanded. In particular, the AlGaInP-based material is a direct transition type semiconductor having the largest band gap among III-V group compound semiconductors excluding nitrides, and extremely high luminance can be obtained particularly in a light emitting region of 560 nm to 660 nm band. For this reason, research and development are still actively conducted.

  FIG. 4 shows a typical structure of a red band AlGaInP-based LED. All epitaxial layers are grown by metal organic chemical vapor deposition (MOVPE).

In the LED in FIG. 4, a buffer layer 2 made of n-type GaAs is grown on a semiconductor substrate 1 made of n-type GaAs, and an n-type light reflection layer 3 is laminated thereon. The light reflecting layer 3 plays a role of reflecting light traveling from the active layer 5 toward the semiconductor substrate 1 in the opposite direction, thereby increasing the external quantum efficiency of the LED without the light being absorbed by the semiconductor substrate 1. Can do. For example, the light reflecting layer 3 has a structure in which an n-type Al _0.4 Ga _0.6 As layer and an n-type Al _0.5 In _0.5 P layer are laminated as a pair. Here, the film thicknesses of the n-type Al _0.4 Ga _0.6 As layer and the n-type Al _0.5 In _0.5 P layer are λ / (4 × n1) with respect to the emission wavelength λ, where the refractive indexes are n1 and n2, respectively. ), Λ / (4 × n2).

  Here, Patent Document 1 (Japanese Patent Laid-Open No. 10-290026) discloses a measure for solving an infrared emission problem in an LED using GaAs as a part of a light reflection layer in a semiconductor light emitting device. At the same time, by making one of the pair of materials constituting the light reflecting layer the same composition as the light emitting layer side of the active layer, the light reflecting layer is excited by the light emitted from the active layer and emits light. A method is disclosed in which the wavelength of the emitted light is the same as the wavelength emitted by the active layer, and the light emission output is generally increased.

  By the way, as a result of active research and development in AlGaInP-based LEDs, it is a well-known fact that the concentration of impurities mixed into the active layer, particularly oxygen (O), has a great influence on luminance. The influence of oxygen is not a level at which oxygen is intentionally added, but is an extremely important parameter that greatly affects the brightness of the LED even if the concentration of the background level contained in the reactor in the growth apparatus is included. . To that end, each company is working to reduce the oxygen concentration in the reactor by making full use of their respective measures.

For example, as a conventional method for reducing the oxygen concentration in the reaction furnace, there have been repeated annealing of a jig in the reaction furnace, dummy growth, and the like.
Japanese Patent Laid-Open No. 10-290026

  However, the conventional method alone has a limit in reducing the oxygen concentration in the reactor.

  Usually, in a reactor of a growth apparatus, there exists a susceptor for setting a substrate material as a sample. The susceptor and the substrate need to be heated to a very high growth temperature such as 500 ° C. to 1000 ° C., but are usually heated from the viewpoint of heat resistance and safety of other parts constituting the growth apparatus. Is only the susceptor described above and a slight periphery thereof. Therefore, in the annealing by the conventional method described above, only a part of the entire reactor is deoxidized although it is an important part. For this reason, oxygen is still remaining at a portion that is not heated and is not sufficiently deoxidized, for example, on the exhaust side of the susceptor in the growth furnace or at the exhaust port. Simultaneously with annealing and dummy growth, oxygen diffuses from the remaining portion of oxygen into the growth furnace and reaches a certain level again. Therefore, although it is possible to reduce the oxygen concentration to some extent, it can be said that it was not always sufficient.

  Therefore, the object of the present invention is to locally reduce the amount of oxygen remaining in the furnace at the time of growth by a simple method, and by further reducing the oxygen concentration mixed into the active layer of the semiconductor light-emitting element, An object of the present invention is to provide a method for manufacturing a high-luminance semiconductor light emitting device.

  In order to achieve the above object, the present invention is configured as follows.

  According to a first aspect of the present invention, there is provided a method for manufacturing a semiconductor light-emitting device, comprising: stacking a plurality of pairs of low refractive index films and high refractive index films on a conductive semiconductor substrate using a vapor deposition method; And manufacturing a III-V group semiconductor light emitting device in which a light emitting portion composed of a first cladding layer, an active layer and a second cladding layer is formed on the light reflecting layer, and a current spreading layer is formed thereon. In the method, the V / III ratio of the source gas supplied into the growth furnace when growing the light reflecting layer is set to the V / III ratio of the source gas supplied into the growth furnace when growing the first cladding layer. It is characterized by lower than.

  According to a second aspect of the present invention, in the method for manufacturing a semiconductor light emitting device according to the first aspect, the V / III ratio of the source gas supplied into the growth furnace when the light reflecting layer is grown is 5 or more and 50 or less. It is characterized by doing.

  According to a third aspect of the present invention, in the method for manufacturing a semiconductor light emitting device according to the first or second aspect, the semiconductor material constituting the light reflecting layer is selected from GaAs, AlGaAs, AlAs, AlGaInP, GaInP, and AlInP. It is characterized in that a semiconductor material containing Al is used for at least one of the two materials of the low refractive index film and the high refractive index film constituting the light reflecting layer.

According to a fourth aspect of the present invention, in the method of manufacturing a semiconductor light emitting device according to any one of the first to third aspects, the material of the low refractive index film constituting the light reflecting layer is Al _x Ga ₁ -x As (provided that , 0.6 ≦ X ≦ 1.0), (Al _Y Ga _1-Y ) _0.5 In _0.5 P (where 0.6 ≦ Y ≦ 1.0), and a high refractive index film The material is either Al _X Ga _1-X As (where 0 ≦ X ≦ 0.6) or (Al _Y Ga _1-Y ) _0.5 In _0.5 P (where 0 ≦ Y ≦ 0.6) It is characterized by.

  According to a fifth aspect of the present invention, in the method for manufacturing a semiconductor light emitting device according to any one of the first to fourth aspects, the number of pairs of the low refractive index film and the high refractive index film of the light reflecting layer is 8 pairs or more and 30 pairs or less. It is characterized by.

  A sixth aspect of the present invention is the method of manufacturing a semiconductor light emitting device according to any one of the first to fifth aspects, wherein the conductive semiconductor substrate is GaAs or Ge.

  According to a seventh aspect of the present invention, in the method of manufacturing a semiconductor light emitting device according to any one of the first to sixth aspects, at least one semiconductor layer is formed on the light emitting portion, and the current spreading layer is formed thereon. A metal oxide layer is formed.

  According to an eighth aspect of the present invention, in the method for manufacturing a semiconductor light emitting device according to any one of the first to sixth aspects, at least one semiconductor layer is formed on the light emitting portion, and the current spreading layer is formed thereon. A multilayer metal oxide layer is formed.

  The invention of claim 9 is the method of manufacturing a semiconductor light emitting device according to claim 7 or 8, wherein the metal oxide layer of the current spreading layer is made of tin-doped indium oxide, indium oxide, zinc oxide, gallium-doped oxidation. A metal oxide in any one of zinc, aluminum-added zinc oxide, and boron-added zinc oxide is used.

  According to the present invention, in the method for manufacturing a semiconductor light emitting device according to any one of claims 1 to 9, the active layer is composed of a light emitting layer having a narrow band gap and a barrier layer having a wider band gap than the light emitting layer. A structure in which a plurality of layers are stacked is also included.

  The present invention also includes a tin-added indium oxide, an indium oxide, a zinc oxide, a gallium-added zinc oxide, an aluminum-added zinc oxide via at least one semiconductor layer on the second cladding layer or the current spreading layer. A mode in which the current dispersion layer is formed of a metal oxide in any of boron-added zinc oxide is also included.

<Key points of the invention>
The gist of the present invention is that when a III-V semiconductor light emitting device, for example, a light emitting diode structure is epitaxially grown, the growth V / III ratio of the light reflecting layer grown on the semiconductor substrate is determined. By setting a value lower than the growth V / III ratio, for example, a significantly lower value of 50 or less, and further by selecting a material containing aluminum as the semiconductor material constituting the light reflecting layer, the substrate and susceptor in the reaction furnace, Has found that the surrounding oxygen concentration can be locally reduced to a lower level, and that a semiconductor light emitting device with higher brightness than the conventional one can be easily obtained.

  The reason is considered as follows. By reducing the growth V / III ratio of the light reflecting layer, the amount of oxygen from the furnace taken into the crystal of the semiconductor material such as AlAs and AlGaAs constituting the light reflecting layer is increased. In other words, during the growth of the light reflecting layer, which is the previous stage of growing the active layer of the LED structure, a forced oxygen gettering effect is caused, and the amount of oxygen mixed into the active layer grown thereon is larger than in the conventional example. Further lower level. Further, when a material containing a large amount of Al is selected as the semiconductor material constituting the light reflecting layer, the amount of oxygen taken into its own epitaxial layer increases, and the above effect is improved.

  The V / III ratio at the time of growing the light reflecting layer is preferably 5 or more and 50 or less. If the V / III ratio during growth of the light reflecting layer is higher than 50, the oxygen gettering effect in the light reflecting layer becomes thin and the light emission output does not increase. On the other hand, if the V / III ratio during the growth of the light reflecting layer is lower than 5, the crystallinity of the light reflecting layer deteriorates and adversely affects the growth of the active layer. As a result, the light emission output does not increase but rather decreases. There is a tendency. Therefore, the V / III ratio during the growth of the light reflecting layer is preferably in the range of 5-50.

  The advantage of forming a multi-layer metal oxide layer as the current spreading layer is that the crystallinity is deteriorated only by growing the V / III ratio of the source gas to 2 or less only during the growth of the current spreading layer on the outermost surface. As a result, it is possible to improve the light extraction efficiency without impairing the current dispersion effect.

  According to the present invention, the V / III ratio of the source gas when growing the light reflecting layer of the III-V group semiconductor light emitting device, and the V / III ratio of the source gas when growing the first cladding layer thereon Is set to a lower value, preferably 5 or more and 50 or less, and further, a material containing aluminum is selected as the semiconductor material constituting the light reflecting layer, so that the substrate and susceptor in the reactor, and the surroundings thereof, are selected. The oxygen concentration can be reduced locally to a lower level.

  Therefore, according to the manufacturing method of the present invention, it is possible to obtain a semiconductor light emitting device in which the amount of oxygen contained in the active layer portion of the conventional semiconductor light emitting device is suppressed to be lower. A simple semiconductor light emitting device can be obtained.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  FIG. 1 shows a semiconductor light emitting device according to a first embodiment of the present invention. A conductive semiconductor substrate 1 and a light reflection layer 3 provided on the main surface of the substrate with a buffer layer 2 interposed therebetween. And a light emitting part (4, 5, 6) including an active layer 5 having a pn junction grown on the light reflecting layer.

Specifically, the light reflection layer 3 is configured as a DBR (distributed Bragg reflection layer) in which films of a low refractive index portion and a high refractive index portion are combined, and the center wavelength of the emission spectrum of light emitted from the light emitting portion. Reflects light that approximately matches. The semiconductor material constituting the light reflecting layer 3 is selected from GaAs, AlGaAs, AlAs, AlGaInP, GaInP, and AlInP. At least one of the two materials of the low refractive index film and the high refractive index film is used. A semiconductor material containing Al is used for the film. In the case of this embodiment, the light reflection layer 3 has a structure in which n-type AlAs (film thickness: 51 nm) and n-type Al _0.4 Ga _0.6 As (film thickness: 45 nm) are sequentially stacked, and the number of pairs is 20 pairs. ing.

  The light emitting part formed on the light reflecting layer 3 is composed of an n-type cladding layer 4 as a first cladding layer, an undoped active layer 5 and a p-type cladding layer 6 as a second cladding layer.

  In order to obtain the oxygen gettering effect in the light reflecting layer, the growth V / III ratio of the light reflecting layer 3 is formed on the light reflecting layer 3 during the growth of the light reflecting layer, which is a stage before growing the active layer 5 of the LED structure. It is set to 50 or less, which is significantly lower than the growth V / III ratio of the n-type cladding layer 4 to be formed. As a result, in combination with the selection of a material containing aluminum as the constituent material of the light reflecting layer, a forced oxygen gettering effect is caused in the light reflecting layer 3, and oxygen to the active layer 5 grown thereon is increased. The amount of mixing is one level lower than that of the conventional example. Therefore, it is possible to easily obtain a semiconductor light emitting device having higher brightness than conventional ones.

  FIG. 2 shows a second embodiment of the semiconductor light emitting device according to the present invention. FIG. 2 includes a contact layer 11 and a current spreading layer 10 made of an ITO film on a p-type cladding layer 6. It is different in point. The growth V / III ratio of the light reflecting layer 3 is set to 50 or less, which is lower than the growth V / III ratio of the n-type cladding layer 4 formed thereon, and a high-luminance semiconductor light emitting device is thereby obtained. The point of the effect is the same.

  In order to confirm the effect of the present invention, the semiconductor light emitting devices of the conventional example and Examples 1 and 2 were prototyped.

[Conventional example]
As a conventional example, a red band LED having a light emission wavelength of about 630 nm having the structure shown in FIG. 4 (same as FIG. 1 except that the manufacturing method is different) was manufactured.

The manufacturing process consists of an n-type GaAs buffer layer 2, an n-type light reflection layer 3, and an n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P on the semiconductor substrate 1 made of n-type GaAs. An n-type cladding layer 4, an undoped active layer 5, a p-type cladding layer 6 made of p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, and a current spreading layer 7 made of p-type GaP were sequentially grown.

The growth temperature in the MOVPE growth was 650 ° C. from the buffer layer 2 to the p-type cladding layer 6, and the current spreading layer 7 was grown at 660 ° C. Other growth conditions were a growth pressure of 50 Torr, a growth rate of each layer of 0.3 to 1.0 nm / sec, and a V / III ratio of 150 of each layer. However, only the V / III ratio of the current dispersion layer 7 was set to 9. Incidentally, the V / III ratio mentioned here is the ratio (quotient) when the denominator is the number of moles of a group III material such as TMGa or TMAl and the molecule is the number of moles of a group V material such as AsH ₃ or PH _3. Point to.

Examples of raw materials used in the MOVPE growth include organic metals such as trimethylgallium (TMGa), triethylgallium (TEGa), trimethylaluminum (TMAl), and trimethylindium (TMIn), arsine (AsH ₃ ), and phosphine (PH ₃ A hydride gas such as) was used. For example, hydrogen selenide (H ₂ Se) was used as an additive material for an n-type layer such as the buffer layer 2. Diethyl zinc (DEZn) was used as an additive material for the conductivity determining impurities of the p-type layer such as the p-type cladding layer 6. In addition, silane (SiH ₄ ), diethyl tellurium (DETe), and dimethyl tellurium (DMTe) can also be used as an additive material for the conductivity determining impurity of the n-type layer. In addition, dimethyl zinc (DMZn) can also be used as a p-type layer additive raw material.

The light reflecting layer 3 has a structure in which n-type AlAs (film thickness: 51 nm) and n-type Al _0.4 Ga _0.6 As (film thickness: 45 nm) are sequentially stacked, and the number of pairs is 20 pairs. The V / III ratio of the source gas supplied into the growth furnace when growing the light reflecting layer 3 was 150 as described above.

  Then, a circular surface electrode 8 having a diameter of 125 μm was formed in a matrix on the upper surface of the epitaxial wafer by a vacuum deposition method. The surface electrode 8 was formed by sequentially depositing gold / zinc (AuZn) alloy, nickel (Ni), and gold (Au) in thicknesses of 60 nm, 10 nm, and 1000 nm, respectively. Further, a back electrode 9 was formed on the entire bottom surface of the epitaxial wafer. The back electrode 9 was formed by sequentially depositing gold / germanium (AuGe) alloy, nickel (Ni), and gold (Au) in thicknesses of 60 nm, 10 nm, and 500 nm, respectively, and then alloying the electrode as an alloy with nitrogen. The test was carried out at 400 ° C. for 5 minutes in a gas atmosphere.

  Then, this epitaxial wafer was processed into a chip shape having a chip size of 300 μm square by a dicing apparatus or the like, and further, die bonding and wire bonding were performed to manufacture an LED element.

  As a result of evaluating various characteristics of the LED fabricated as described above, the light emission output was 1.63 mW, and the forward operation voltage was 1.94 V (all evaluation results when energizing 20 mA).

[Example 1]
An epitaxial wafer for red LED having an emission wavelength of about 630 nm having the structure shown in FIG. 1 was produced. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED device manufacturing method were basically the same as those in the conventional example. The points different from the conventional example will be listed below, and detailed description will be given accordingly.

The light reflecting layer 3 has a structure in which n-type AlAs (film thickness: 51 nm) and n-type Al _0.4 Ga _0.6 As (film thickness: 45 nm) are sequentially laminated, as in the above-described conventional example, and the number of pairs is 20 pairs. did. However, the V / III ratio of the source gas for growing the light reflecting layer 3 was set to a value lower than 150 of the conventional example. That is, in Example 1, the V / III ratio of the raw material gas supplied into the growth furnace when growing the light reflecting layer 3 was lowered to 100, 50, 25, and 10. In addition, since the carrier concentration of the light reflecting layer fluctuated with each change of the V / III ratio, the amount of hydrogen selenide, which is an n-type conductivity determining impurity, was appropriately adjusted each time, so that the same carrier concentration was obtained. Was set to be.

  The results of evaluating various characteristics of the LED fabricated as described above are shown in Table 1 below. Further, SIMS analysis was performed on each wafer produced at this time, and the oxygen concentration in the light reflection layer was measured. The results are also shown in Table 1.

  From this result, the sample having a V / III ratio of 100 when the light reflecting layer is grown exhibits almost the same characteristics as the conventional example, and no improvement is observed. However, in the sample in which the V / III ratio at the time of growing the light reflecting layer is set to 50, 25, 10 and 50 or less, the light emission output is increased by about 10% to 15% in comparison with the conventional example. It was. Further, as a result of investigating the oxygen concentration in the light reflecting layer by SIMS analysis at this time, the oxygen concentration in the light reflecting layer increases by setting the V / III ratio at the time of growing the light reflecting layer to 50 or less. ing.

This is probably because the V / III ratio is lowered, that is, the As partial pressure referred to in this embodiment is reduced, so that the inside of the furnace incorporated into the crystals of AlAs and Al _0.4 Ga _0.6 As constituting the light reflection layer. It seems that the amount of oxygen from is increased. This is speculative, but there are also SIMS analysis results that it is difficult to increase the oxygen concentration in a semiconductor material that does not contain Al such as GaAs or GaP, or has a low Al content such as Al _0.1 Ga _0.9 As or Al _0.2 Ga _0.8 As. Based on this, it is considered that a material containing a large amount of Al increases the amount of oxygen taken into its own epitaxial layer.

  Therefore, by using a semiconductor material that contains Al, preferably a large amount, in at least one of the light reflecting layers, and sets the V / III ratio when growing the light reflecting layer to 50 or less, the LED structure Before the active layer is grown in the growth lot, a forcible oxygen gettering effect is caused in the light reflecting layer before the active layer is grown, and the amount of oxygen mixed into the active layer grown thereon is further increased than in the conventional example. As a result, the light output is increased.

[Example 2]
An epitaxial wafer for red LED having an emission wavelength of about 630 nm having the structure shown in FIG. 2 was produced. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED device manufacturing method were basically the same as those in the conventional example. The points different from the conventional example will be listed below, and detailed description will be given accordingly.

In Example 2, the current spreading layer 7 made of p-type GaP was not grown after the growth of the p-type cladding layer 6, and the contact layer 11 made of p-type Al _0.1 Ga _0.9 As was grown instead.

Further, after this LED epitaxial wafer was unloaded from the MOVPE apparatus, an ITO film 10 having a thickness of 290 nm was formed on the surface of the wafer, that is, on the surface side of the contact layer 11 by vacuum deposition. In this structure, the ITO film 10 becomes a current dispersion layer. At this time, the glass substrate for evaluation set in the same batch of ITO film deposition was taken out, cut into a size capable of Hall measurement, and the electrical characteristics of the ITO film alone were evaluated. The carrier concentration was 1.21 × 10 ²¹ / cm ³ , mobility 19.6 cm ² / Vs, resistivity 2.35 × 10 ⁻⁴ Ω · cm.

  Further, the V / III ratio of the raw material gas supplied into the growth furnace when growing the light reflecting layer 3 of this example was 25. In addition, since the carrier concentration of the light reflecting layer fluctuates with the change of the V / III ratio, the amount of hydrogen selenide, which is an n-type conductivity determining impurity, is appropriately adjusted each time so that the same carrier concentration is obtained. Set to.

  As a result of evaluating various characteristics of the LED fabricated as described above, the light emission output was 1.81 mW and the forward operation voltage was 1.91 V (all the evaluation results when energizing 20 mA). That is, in the second embodiment, an example in which a current dispersion layer made of an ITO film, which is a general transparent conductive film, is used as the current dispersion layer is shown. However, the V / III in the light reflection layer, which is the issue of the present invention, is shown. By setting the ratio to 25, the luminance of the LED can be increased for the same reason as in the first embodiment.

<About optimum conditions>
First, as shown in the above embodiment, it can be said that there is an optimum value for the V / III ratio during the growth of the light reflecting layer. If the V / III ratio during growth of the light reflection layer is too high, for example, 100, the oxygen gettering effect in the light reflection layer is thin, and the light emission output does not increase. Conversely, if the V / III ratio during the growth of the light reflecting layer is made too low, such as 2, for example, the problem arises that the crystallinity of the light reflecting layer deteriorates, which also affects the growth of the active layer. Will be affected. As a result, the light emission output does not increase but rather tends to decrease. From the above, the V / III ratio during the growth of the light reflecting layer has the optimum value of 5 to 50 described above.

  Secondly, the number of pairs of light reflecting layers may be too small or too bad. The reason is that if the number of pairs is too small, a high light output cannot be obtained because sufficient light reflectance cannot be secured. Next, the case where there are too many pairs is described. The light reflectance basically increases as the number of pairs increases. However, it does not increase indefinitely and shows a saturation tendency from a certain number of pairs. Therefore, if it is too thick, only the raw material cost for monotonous growth increases, which is wasted. From the above, it can be said that there is an optimum value for the number of pairs of light reflecting layers.

  FIG. 3 is a diagram showing the relationship between the number of pairs of light reflecting layers and the light reflectance in the embodiment of the present invention. As can be seen from the figure, the light reflectivity of the light reflecting layer exceeds 70% when the number of pairs is approximately 8 pairs, and exceeds 80% when 13 pairs. And it becomes almost 100% with 25 pairs, and is saturated to the maximum 100% after 30 pairs. Therefore, it can be said that the number of pairs of light reflecting layers is preferably in the range of about 8 to 30 pairs, more preferably in the range of about 13 to 25 pairs.

Third, there are materials suitable for the light reflecting layer. The material used for the light reflecting layer is preferably as wide as possible. However, it is substantially difficult to achieve a large difference in refractive index between materials having a wide band gap. In general, AlGaAs-based materials, AlGaInP-based materials, and the like used for the light reflection layer have a trade-off relationship. Therefore, there is an optimum value for the material and composition of the light reflecting layer to be set in a preferable range, because the material of the low refractive index film constituting the light reflecting layer is Al _X Ga _{1 -X} As (where, 0.6 ≦ X ≦ 1.0), (Al _Y Ga _1-Y ) _0.5 In _0.5 P (where 0.6 ≦ Y ≦ 1.0), and the material of the high refractive index film Is either Al _X Ga _1-X As (where 0 ≦ X ≦ 0.6) or (Al _Y Ga _1-Y ) _0.5 In _0.5 P (where 0 ≦ Y ≦ 0.6). Is preferred. However, considering the oxygen gettering effect in the light reflecting layer, the low refractive index film and the high refractive index film should be made of a semiconductor material containing Al, and if possible, the Al composition ratio Y The value is preferably as large as possible.

Fourth, a current distribution layer made of a metal oxide, for example, an ohmic contact layer in contact with the ITO film, needs to have a conductivity type determining impurity concentration added at a very high concentration. Specifically, in the case of a contact layer to which zinc (Zn) is added, the crystal material is preferably GaAs having an Al mixed crystal ratio of 0 to 0.2, or AlGaAs, and the carrier concentration is 1 ×. 10 ¹⁹ / cm ³ or more is suitable, and the higher the better. In the case of a contact layer using magnesium (Mg) as a conductivity determining impurity, the crystal material is preferably InP with a GaP composition of 0 to 0.2 or GaInP, and the carrier concentration is 1 × 10 ¹⁹ / cm ³ or more is suitable, and the higher the better. The ITO film basically belongs to an n-type semiconductor material, and the LED is generally manufactured by p-side up. For this reason, in the LED in which the ITO film is applied to the current spreading layer, the conductivity type is an n / p / n junction from the substrate side. For this reason, in LED, a large potential barrier is generated at the interface between the ITO film and the p-type semiconductor layer, which usually results in a light emitting diode having a very high operating voltage. In order to solve this problem, a contact layer having a very high carrier concentration is required for the p-type semiconductor layer. Further, the reason why the band gap of the contact layer is narrow depends strongly on the fact that it is easier to increase the carrier.

  Fifth, the thickness of the contact layer described above is preferably in the range of 1 nm to 50 nm. This is because the contact layers all have a band gap that serves as an absorption layer for the light emitted from the active layer, so that the emission luminance (output) decreases as the film thickness increases. . Therefore, the upper limit of the thickness of the contact layer is preferably about 50 nm, more preferably up to 30 nm. In addition, when the contact layer thickness is less than 1 nm, tunnel junction between the ITO film and the contact layer becomes difficult, which makes it difficult to reduce the operating voltage and stabilize the operating voltage. Become. Therefore, there is an optimum value for the thickness of the contact layer in contact with the ITO film, which is 1 nm to 50 nm.

  Sixth, it is desirable that the method of forming the current dispersion layer made of the metal oxide film is a vacuum deposition method. The reason will be described below for each manufacturing method. First, in the sputtering method, the equipment cost of the sputtering apparatus itself is high, and furthermore, the number of charged sheets per batch is small, so that throughput is also a problem. Therefore, it is difficult to significantly reduce the cost for manufacturing the current spreading layer. Next, in the spray method using a MOD solution, first, the resistivity of the ITO film cannot be lowered unless the surface temperature of the substrate is heated to 500 ° C. or higher. A large problem is that the surface of the contact layer is oxidized and a tunnel junction cannot be achieved. Further, since the ITO film is formed at a high temperature, the carrier concentration of the ITO film is lowered, and it is difficult to make a tunnel junction. Furthermore, it is difficult to charge a large number of sheets, that is, to manufacture a manufacturing facility with high throughput, and it is difficult to perform stable mass production. Next, in the coating method, it is very difficult to lower the resistivity as compared with the spray method, the sputtering method, and the vacuum deposition method. This makes it very difficult to make a tunnel junction with the contact layer. Furthermore, since it is necessary to repeatedly perform steps such as coating, drying, and baking in order to form the ITO film from about 100 nm to about 400 nm, the throughput is very poor. For the above reasons, it is preferable to use the vacuum deposition method as a method with a low manufacturing apparatus price, excellent stability, and high throughput.

  Seventh, the thickness of the ITO film is preferably in the range of 100 nm to 500 nm. The reason why the lower limit is 100 nm is that a film thickness of about 100 nm or more is necessary to obtain at least a sufficient current dispersion effect. Next, the reason why the upper limit is 450 nm is that the transparency of the ITO film, that is, the transmittance gradually deteriorates when the film thickness of the ITO film reaches about 500 nm when formed by vacuum deposition. Because there is. In addition, since the ITO film having a film thickness of about 150 nm to about 350 nm can provide a sufficient current dispersion effect, even if it is too thick, it only increases the manufacturing cost. Accordingly, it can be said that the thickness of the ITO film is preferably in the range of 100 nm to 500 nm, more preferably about 200 nm to 350 nm.

[Modification 1]
In Examples 1 and 2 of the present invention, no structure is interposed between the active layer and the p-cladding layer in any structure. However, it is possible to adopt a structure in which, for example, an intrinsic undoped layer is provided, or a pseudo undoped layer is provided that becomes a pseudo undoped layer even if it contains some conductive impurities. Only the effect of improving the reliability of the output of the LED element is produced, and the intended effect of the present invention is still obtained.

[Modification 2]
In the embodiment of the present invention, only a red LED element having a light emission wavelength of 630 nm was used as an example of manufacture. However, in other LED elements manufactured using the same AlGaInP material, for example, LED elements having a light emission wavelength of 560 nm to 660 nm However, the material of each layer used at this time, the carrier concentration, etc. have no significant changes other than the active layer. Therefore, even if the emission wavelength of the LED element is set to a wavelength band different from that of the embodiment of the present invention, the same effect as described above can be obtained.

[Modification 3]
In the examples of the present invention, an LED structure in which a buffer layer is always provided is used as an example of manufacture. However, even if an LED element structure in which the layer is omitted is employed, the intended effect of the present invention can be obtained.

[Example 4]
In the embodiment of the present invention, the conductivity determining impurity added to the p-type layer is zinc (Zn) and the conductivity determining impurity added to the n-type layer is selenium (Se). Even when magnesium (Mg) is used as the impurity or Si or Te is used as the n-type conductivity determining impurity, the effect of the present invention can be obtained.

[Modification 5]
In the embodiments of the present invention, the surface electrode is always circular in shape. However, other shapes such as a square, a rhombus, and a polygon can obtain the intended effect of the present invention. it can.

[Modification 6]
In the embodiment of the present invention, an example in which only an ITO film is used as the current spreading layer has been described. In addition, indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), gallium-doped zinc oxide (GZO) Metal oxides generally known for low resistance, such as aluminum-added zinc oxide (AZO) and boron-added zinc oxide (BZO), can be applied to the current spreading layer. You can get the effect you intended.

[Modification 7]
In the embodiment of the present invention, only an example using GaAs as a semiconductor substrate was given, but in addition to this, an epitaxial wafer for LED using Ge as a starting substrate, or GaAs or Ge as a starting substrate, which will be described later. The effect intended by the present invention can also be obtained in an epitaxial wafer for LED that is removed and uses a metal substrate having a thermal conductivity equal to or higher than that of Si or Si as an alternative free-standing substrate.

[Modification 8]
In the embodiment of the present invention, an example in which AlAs and AlGaAs are used for the light reflecting layer is shown. However, even if this is AlInP and AlGaAs, or AlAs and AlGaAs, only a slight change is caused in the light reflectance resulting from a slight difference in refractive index, and a high Al composition material is used. If the V / III ratio during growth of the reflective layer is set to 50 or less, the intended effect of the present invention can be obtained although it has some device dependency.

It is sectional drawing of the AlGaInP type | system | group red LED element which concerns on one Example of this invention. It is sectional drawing of the AlGaInP type | system | group red LED element which concerns on the other Example of this invention. It is the figure which showed the relationship between the number of pairs of the light reflection layer in the Example of this invention, and light reflectivity. It is sectional drawing of the conventional AlGaInP type red LED element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Buffer layer 3 Light reflection layer 4 N-type cladding layer 5 Active layer 6 P-type cladding layer 7 Current dispersion layer 8 Front surface electrode 9 Back surface electrode 10 ITO film (current dispersion layer)
11 Contact layer

Claims (9)

Using a vapor phase growth method, a plurality of pairs of low refractive index films and high refractive index films are laminated on a conductive semiconductor substrate to form a light reflecting layer, and a first cladding layer on the light reflecting layer, In the method of manufacturing a group III-V semiconductor light emitting device, in which a light emitting portion composed of an active layer and a second cladding layer is formed, and a current spreading layer is formed thereon,
The V / III ratio of the source gas supplied into the growth furnace when growing the light reflecting layer is lower than the V / III ratio of the source gas supplied into the growth furnace when growing the first cladding layer. A method of manufacturing a semiconductor light emitting device. In the manufacturing method of the semiconductor light-emitting device according to claim 1,
A method of manufacturing a semiconductor light emitting device, wherein a V / III ratio of a source gas supplied into a growth furnace when growing the light reflecting layer is set to 5 or more and 50 or less. In the manufacturing method of the semiconductor light-emitting device according to claim 1 or 2,
The semiconductor material constituting the light reflecting layer is selected from GaAs, AlGaAs, AlAs, AlGaInP, GaInP, and AlInP, and two materials, a low refractive index film and a high refractive index film constituting the light reflecting layer A method for manufacturing a semiconductor light emitting element, wherein a semiconductor material containing Al is used for at least one of the films. In the manufacturing method of the semiconductor light-emitting device according to claim 1,
The material of the low refractive index film constituting the light reflecting layer is Al _x Ga _1-x As (provided that 0.6 ≦ X ≦ 1.0), (Al _y Ga _1-y ) _0.5 In _0.5 P (provided that 0.6 ≦ Y ≦ 1.0), and the material of the high refractive index film is Al _X Ga _1-X As (where 0 ≦ X ≦ 0.6), (Al _Y Ga _{1 -Y} ) _0.5 In _0.5 P (where 0 ≦ Y ≦ 0.6). In the manufacturing method of the semiconductor light-emitting device according to claim 1,
The method of manufacturing a semiconductor light emitting element, wherein the number of pairs of the low refractive index film and the high refractive index film of the light reflecting layer is 8 pairs or more and 30 pairs or less. In the manufacturing method of the semiconductor light-emitting device according to claim 1,
A method of manufacturing a semiconductor light emitting device, wherein the conductive semiconductor substrate is GaAs or Ge. In the manufacturing method of the semiconductor light-emitting device according to claim 1,
A method of manufacturing a semiconductor light emitting device, comprising forming at least one semiconductor layer on the light emitting portion, and forming a metal oxide layer thereon as the current spreading layer. In the manufacturing method of the semiconductor light-emitting device according to claim 1,
A method of manufacturing a semiconductor light emitting device, comprising forming at least one semiconductor layer on the light emitting portion and forming a multilayer metal oxide layer thereon as the current spreading layer. In the manufacturing method of the semiconductor light-emitting device according to claim 7 or 8,
The material of the metal oxide layer of the current spreading layer is a metal oxide in any one of tin-added indium oxide, indium oxide, zinc oxide, gallium-added zinc oxide, aluminum-added zinc oxide, and boron-added zinc oxide. A method for manufacturing a semiconductor light emitting device.

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