JP2005150646A - Light-emitting element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element in which current diffusing layers can be formed efficiently despite the layers being formed on both main surface sides of an AlGaInP light-emitting layer section, and which can suppress the deterioration of the current diffusing layers caused by the thermal diffusion of the dopant profile of the light-emitting layer. <P>SOLUTION: The light-emitting element 100 comprises the light-emitting layer 24, having a double heterostructure composed of AlGaInP lattice in matching with GaAs, a thick transparent semiconductor layer 90 formed on the second main surface side of the light-emitting layer 24, with a thickness of ≥10 μm by the hydride vapor growth method, and an auxiliary current diffusing layer 91 which is formed, by means of MOVPE method on the first main surface side of the light-emitting layer 24 with a thickness smaller than that of the semiconductor layer 90, has a composition lattice in matching with GaAs, and is constituted of AlGaInP, having a larger Al mixed crystal ratio than the active layer has. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light emitting device and a method for manufacturing the same.

JP-A-5-275740 JP 2001-68731 A

Conventional technology

The light-emitting layer portion is formed of (Al _x Ga _1-x ) _y In _1-y P mixed crystal (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1; hereinafter also referred to as AlGaInP mixed crystal or simply AlGaInP). The light emitting device has a high brightness by adopting a double hetero structure in which a thin AlGaInP active layer is sandwiched between an n-type AlGaInP clad layer having a larger band gap and a p-type AlGaInP clad layer. An element can be realized.

  For example, taking an AlGaInP light emitting device as an example, an n-type GaAs buffer layer, an n-type AlGaInP cladding layer, an AlGaInP active layer, and a p-type AlGaInP cladding layer are formed in this order in a heterogeneous form on an n-type GaAs substrate. The light emitting layer part which laminates | stacks and makes a double hetero structure is formed. Electricity is supplied to the light emitting layer portion through an electrode formed on the element surface. Here, since the electrode acts as a light shielding body, for example, it is formed so as to cover only the central portion of the main surface of the light emitting layer portion, and light is extracted from the surrounding electrode non-formation region.

  In this case, reducing the area of the electrode as much as possible can increase the area of the light extraction region formed around the electrode, which is advantageous from the viewpoint of improving the light extraction efficiency. Conventionally, attempts have been made to increase the light extraction amount by effectively spreading the current in the element by devising the electrode shape, but in this case as well, an increase in the electrode area is unavoidable anyway, and the light extraction area On the contrary, it falls into a dilemma where the amount of light extraction is limited by the decrease. In addition, the carrier concentration of the dopant in the clad layer, and thus the conductivity, is kept somewhat low in order to optimize the light emission recombination of carriers in the active layer, and the current tends not to spread in the in-plane direction. . This leads to concentration of current density in the electrode covering region and a substantial light extraction amount in the light extraction region. Therefore, a method is adopted in which a current diffusion layer made of GaP or the like with a low resistivity and a high carrier concentration is formed between the cladding layer and the electrode. As disclosed in Patent Document 1 and Patent Document 2, the current diffusion layer can also be used as an element substrate by being formed thick.

  The current diffusion layer in the light emitting element as described above is often formed by a metal organic vapor phase epitaxy (hereinafter, also referred to as MOVPE method) together with the light emitting layer portion. In this case, the current diffusion layer is generally formed by setting the layer thickness to a certain extent in order to sufficiently spread the current in the in-plane direction, for example, by making the thickness larger than the light emitting layer portion. However, the MOVPE method has a low layer growth rate, and it takes a very long time to grow a current diffusion layer having a sufficient thickness. This causes a problem that the manufacturing efficiency is lowered and the cost is increased.

  Further, since GaP has a considerably larger lattice constant than GaAs (and hence the AlGaInP light emitting layer portion grown thereon), the AlGaInP light emitting layer portion is epitaxially grown on the GaAs substrate from the viewpoint of improving the quality of the light emitting layer portion, A step of further growing a current diffusion layer made of GaP or the like is employed. However, when the thick current diffusion layer is epitaxially grown by the MOVPE method, the underlying light emitting layer portion is exposed to the high-temperature thermal history of the MOVPE method for a long time, thereby forming a pn junction. The concentration profile of the p-type dopant and n-type dopant in the layer thickness direction collapses due to thermal diffusion, causing a problem that leads to a decrease in internal quantum efficiency of the light-emitting layer portion. More specifically, the dopant from the clad layers on both sides penetrates into the active layer formed by non-doping, and the probability of recombination of electrons / holes decreases, and the emission intensity deteriorates remarkably.

  Further, as disclosed in Patent Document 2, it can be said that providing the current diffusion layer on both surfaces of the light emitting layer portion is more desirable for improving the current diffusion effect and the light extraction efficiency from the side surface of the layer. However, when an attempt is made to grow a current diffusion layer such as GaP having a lattice constant greatly different from both sides of the AlGaInP light emitting layer portion, the first current diffusion layer can be formed after the light emitting layer portion is grown. It is difficult to grow the second current diffusion layer on the GaAs substrate prior to the growth of the light emitting layer portion from the viewpoint of ensuring the quality of the light emitting layer portion as described above. Therefore, the following process is adopted. That is, after the AlGaInP light emitting layer portion is grown on the second main surface of the GaAs substrate by the MOVPE method, the first current diffusion layer made of GaP or the like is grown on the second main surface of the light emitting layer portion by the MOVPE method. . Next, the GaAs substrate is removed from the first main surface side of the light emitting layer portion, and a second current diffusion layer made of GaP or the like is grown on the first main surface of the light emitting layer portion by the MOVPE method. However, when this process is adopted, a thermal history of the MOVPE method for growing the second current diffusion layer is further added to the light emitting layer portion after the GaAs substrate is peeled off, and the dopant profile of the light emitting layer portion is increased. There is a problem that deterioration due to thermal diffusion becomes more significant.

  Therefore, as a method for solving this, it is conceivable to form the second current diffusion layer with AlGaAs having a band gap energy larger than that of the AlGaInP active layer and having a lattice constant close to that of GaAs. In this method, it is possible to grow a second current diffusion layer made of AlGaAs on a GaAs substrate first, and then grow an AlGaInP light emitting layer portion, and then grow the first current diffusion layer. The high-temperature MOVPE thermal history applied to the light emitting layer portion is only required once. However, AlGaAs needs to significantly increase the Al content in order to ensure transparency with respect to the luminous flux from the light emitting layer portion. Therefore, when the GaAs substrate is finally removed by chemical etching, the Al oxide film is formed on the substrate removal surface of the second current diffusion layer made of AlGaAs grown immediately above it because of the high Al content. There is a drawback that the light transmission efficiency of the surface of the current diffusion layer is deteriorated and the light extraction efficiency is lowered. Further, since the first current diffusion layer is still formed by MOVPE, the problem of deterioration due to thermal diffusion of the dopant profile of the light emitting layer is not reduced.

  The problem of the present invention is that the current diffusion layer can be efficiently formed despite the fact that the current diffusion layers are formed on both main surface sides of the AlGaInP light emitting layer portion, and also due to the thermal diffusion of the dopant profile of the light emitting layer portion. An object of the present invention is to provide a light-emitting element capable of suppressing deterioration and a manufacturing method thereof.

Means and actions / effects for solving the problems

In order to solve the above-described problems, the light-emitting element of the present invention includes:
Among compounds represented by the composition formula (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), a compound having a composition that lattice matches with GaAs A light emitting layer portion having a double hetero structure in which a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer each formed in this order are laminated,
III-V having a band gap energy larger than the photon energy corresponding to the peak wavelength of the luminous flux from the light emitting layer portion, with the main surface side formed by the first conductivity type cladding layer of the light emitting layer portion as the first main surface side A transparent thick film semiconductor layer in which a group compound semiconductor is formed to a thickness of 10 μm or more by hydride vapor phase epitaxy on the second main surface side of the light emitting layer portion;
On the first main surface side of the light emitting layer portion, it is formed thinner than the transparent thick film semiconductor layer by the MOVPE method, and the composition formula (Al _{x ′} Ga _{1−x ′} ) _{y ′} In _{1−y ′} P (however, 0 Among the compounds represented by ≦ x ′ ≦ 1, 0 ≦ y ′ ≦ 1), the compound has a composition that lattice-matches with GaAs and has a larger Al mixed crystal ratio x ′ than the active layer. And an auxiliary current diffusion layer.

The method for producing a light emitting device of the present invention is a method for producing the light emitting device of the present invention,
It is thinner than the transparent thick film semiconductor layer and is represented by the composition formula (Al _{x ′} Ga _{1−x ′} ) _{y ′} In _{1−y ′} P (where 0 ≦ x ′ ≦ 1, 0 ≦ y ′ ≦ 1). The auxiliary current diffusion layer made of a compound having a lattice-matching composition with GaAs and having an Al mixed crystal ratio x ′ larger than that of the active layer is formed on the second main surface of the GaAs single crystal substrate by the MOVPE method. An auxiliary current diffusion layer growth step for epitaxial growth on the substrate;
The compound represented by the composition formula (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is formed on the second main surface side of the auxiliary current diffusion layer. Among them, a light emitting layer portion having a double hetero structure in which a first conductivity type clad layer, an active layer, and a second conductivity type clad layer each made of a compound lattice-matched with GaAs are laminated in this order is formed by the MOVPE method. A light emitting layer growth process for epitaxial growth;
On the second main surface side of the light emitting layer portion, a transparent thick film semiconductor layer made of a III-V group compound semiconductor having a band gap energy larger than the photon energy corresponding to the peak wavelength of the luminous flux from the light emitting layer portion is hydride gas. A transparent thick film semiconductor layer growth step of epitaxially growing to a thickness of 10 μm or more by a phase growth method;
And a substrate removal step of removing the GaAs single crystal substrate from the first main surface side of the auxiliary current diffusion layer.

In the present invention, “a compound semiconductor that lattice-matches with GaAs” is assumed to be a bulk crystal state in which no lattice displacement is caused by stress, and the lattice constant of the compound semiconductor is a1, and the lattice constant of GaAs is a0. , {| A1-a0 | / a0} × 100 (%) means a compound semiconductor in which the lattice mismatch rate is within 1%. Further, among the compounds represented by “composition formula (Al _{x ′} Ga _{1−x ′} ) _{y ′} In _{1−y ′} P (where 0 ≦ x ′ ≦ 1, 0 ≦ y ′ ≦ 1), GaAs The compound that is lattice-matched with “AlGaInP that is lattice-matched with GaAs” or the like is described. The active layer may be configured as a single layer of AlGaInP, or may be configured as a quantum well layer in which barrier layers and well layers made of AlGaInP having different compositions are stacked alternately (the entire quantum well layer). Is regarded as a single active layer).

  In the light emitting device of the present invention, the light emitting layer portion is composed of AlGaInP lattice-matched with GaAs, and an auxiliary current diffusion layer is provided on the first main surface side of the light emitting layer portion in order to enhance the current diffusion effect in the in-plane direction. A transparent thick film semiconductor layer functioning as a conductive layer is formed on the second main surface side with a thickness of 10 μm or more. Among them, the auxiliary current diffusion layer is made of AlGaInP lattice-matched with GaAs, like the light emitting layer portion. As a result, the auxiliary current diffusion layer can be epitaxially grown on the GaAs single crystal substrate by the MOVPE method prior to the light emitting layer portion, and the thermal history during the growth of the auxiliary current diffusion layer does not reach the light emitting layer portion. it can.

  On the other hand, the transparent thick film semiconductor layer is grown by hydride vapor phase epitaxy. Hydride Vapor Phase Epitaxial Growth Method (hereinafter referred to as HVPE method) converts Ga (gallium) having a low vapor pressure into GaCl which is easily vaporized by reaction with hydrogen chloride, and uses the GaCl as a medium. This is a method of performing vapor phase growth of a III-V compound semiconductor layer by reacting a group V element source gas with Ga. For example, the growth rate of the III-V compound semiconductor layer by the MOVPE method is as low as about 4 μm / hour, for example, and even if it is suitable for the growth of a thin light emitting layer part, the transparent thick film semiconductor layer having a thickness of 10 μm or more The growth is clearly disadvantageous in terms of efficiency. On the other hand, the layer growth rate of the HVPE method is, for example, about 9 μm / hour, which is more than twice that of the MOVPE method. Therefore, the layer growth rate can be made higher than that of the MOVPE method, the transparent thick film semiconductor layer can be formed with a very high efficiency, and since no expensive organic metal is used, the raw material cost is kept much lower than that of the MOVPE method. Can do.

In addition, although the layer grown using the MOVPE method has a large residual amount of C and H derived from the organic metal, the transparent thick film semiconductor layer employed in the present invention is formed by the HVPE method using no organic metal. Since it is grown, it is difficult for C and H derived from the organic metal to remain, and a high-quality layer with good conductivity can be obtained more easily. Specifically, the C concentration and the H concentration in the transparent thick film semiconductor layer are respectively limited to, for example, 7 × 10 ¹⁷ / cm ³ or less, and thus, below the detection limit (for example, about 1 × 10 ¹⁷ / cm ³ or more The following is also relatively easy.

  Since the transparent thick film semiconductor layer is epitaxially grown on the second main surface side of the light emitting layer portion after the light emitting layer portion is epitaxially grown on the second main surface side of the auxiliary current diffusion layer, the transparent thick film semiconductor layer is grown. The thermal history is also applied to the light emitting layer portion. However, since the auxiliary current diffusion layer made of AlGaInP is grown before the light emitting layer portion, the growth heat history applied to the light emitting layer portion is only required once when the transparent thick film semiconductor layer is grown. In the invention, since this is performed by the HVPE method having a high growth rate, the time during which the light emitting layer portion is exposed to the thermal history of the growth can be relatively short despite the growth of the thick semiconductor layer. As a result, deterioration due to thermal diffusion of the dopant profile of the light emitting layer is greatly reduced.

  The auxiliary current diffusion layer and the light emitting layer portion made of AlGaInP can be formed only by using the MOVPE method having a slow growth rate. However, the thickness of the auxiliary current diffusion layer is thinner than that of the transparent thick film semiconductor layer, so that the production efficiency is lowered. It is hard to cause. Further, the transparent thick film semiconductor layer is provided only on the second main surface side of the light emitting layer portion, and the first main surface side is an auxiliary current diffusion layer thinner than that, thereby reducing the layer thickness of the entire light emitting element. Can do. As a result, heat dissipation in the layer thickness direction against Joule heat generation when the element is light-energized is promoted, and the element life can be improved. In particular, in a high-luminance display element (for example, for traffic signals or a large screen display) or a large current multi-face light-emitting element such as an illumination element, the effect of improving heat dissipation by reducing the element thickness is significant. In this case, when the auxiliary current diffusion layer is grown, if the dopant concentration (effective carrier concentration) is set higher than that of the cladding layer in contact therewith, the sheet resistance finally required as the auxiliary current diffusion layer is secured. Thus, the amount of additional diffusion of the dopant can be reduced, and the efficiency of the additional diffusion step can be improved.

  Further, in the grown state, the GaAs single crystal substrate is bonded to the first main surface side of the auxiliary current diffusion layer. Therefore, it is necessary to remove this by, for example, chemical etching. In the light emitting device of the present invention, the auxiliary current diffusion layer is made of AlGaInP having an Al mixed crystal ratio larger than that of the active layer. The auxiliary current diffusion layer made of AlGaInP has the same band gap energy and has a lower Al content compared to the conventionally used AlGaAs. It is possible to effectively prevent the transparency of the layer surface from being lowered (and consequently the deterioration of the light extraction efficiency).

  The auxiliary current diffusion layer only needs to suppress the absorption of the emitted light beam. In other words, the auxiliary current diffusion layer may be AlGaInP having a higher band gap energy than the active layer. In this case, the cladding layer sandwiching the active layer from both sides is also made of AlGaInP having a higher band gap energy than the active layer. The auxiliary current diffusion layer can be made of AlGaInP having a composition different from that of the first conductivity type cladding layer in contact with the auxiliary current diffusion layer, or can be made of AlGaInP having the same composition. When the auxiliary current diffusion layer is composed of AlGaInP having the same composition as that of the first conductivity type cladding layer, both of them apparently become an integrated AlGaInP layer, but the integrated AlGaInP layer includes an auxiliary current diffusion layer portion. Only thicker than the second conductivity type cladding layer. Therefore, it can be seen that the remaining first main surface side portion of the AlGaInP layer, which is reduced from the second main surface side by the layer thickness of the second conductivity type cladding layer, forms the auxiliary current diffusion layer. . The auxiliary current diffusion layer can make the current diffusion effect more remarkable when the effective carrier concentration is higher than that of the first conductivity type cladding layer.

  By making the Al mixed crystal ratio x ′ of the compound AlGaInP forming the auxiliary current diffusion layer smaller than that of the first conductivity type cladding layer (and the Al mixed crystal ratio x ′ being larger than that of the active layer), the first conductivity type is obtained. A band edge discontinuous structure due to a band gap energy difference from the auxiliary current diffusion layer is generated between the cladding layer and the cladding layer in a form that acts as a barrier against the majority carrier flow during light emission driving. This barrier effect enhances the current diffusion effect at the boundary between the auxiliary current diffusion layer and the first conductivity type cladding layer, and the handicap that the auxiliary current diffusion layer is a thin layer compared to the transparent thick film semiconductor layer. Can be reduced.

  In the case of an element chip having a square planar form, if the dimension of one side is X, an element dimension of X ≧ 150 μm or more is required in order to secure luminance when used as a high-luminance display element or an illumination element. There are many cases. When energizing such a large-area element, the first chip thickness from the second main surface of the active layer to the first main surface of the auxiliary current diffusion layer is Z, and the transparent thickness from the second main surface of the active layer is When the chip thickness reaching the second main surface of the film semiconductor layer is Y (see FIG. 1), 200 μm ≧ Y ≧ 11 μm sufficiently enhances the light extraction effect from the side surface of the transparent thick film semiconductor layer, This is desirable from the viewpoint of improving the integrating sphere brightness.

  In addition, when the transparent thick film semiconductor layer is provided only on the second main surface side of the light emitting layer portion, it is desirable to satisfy Z / Y ≦ 0.2 and Y / X ≦ 0.5, thereby enabling large current conduction. In addition, it is possible to realize a light-emitting element that can withstand a large amount of light and can maintain high light emission performance over a long period of time. When Z / Y> 0.2, the transparent thick film semiconductor layer satisfying the definition of the present invention is surely present only on the second main surface side of the light emitting layer portion, but the first main surface rather than the active layer. The compound semiconductor layer located on the side has a considerably large thickness even if the definition of the transparent thick film semiconductor layer is not satisfied, and the effect of reducing the overall height of the device and improving the heat dissipation by it is sufficiently expected. It becomes impossible. Further, when Y / X ≦ 0.5, the relative thickness of the transparent thick film semiconductor layer having poor heat dissipation with respect to the element area excessively increases, leading to an increase in the forward voltage of the element, resulting in a decrease in lifetime. There is a problem that makes it easy to connect directly.

  In the light emitting device of the present invention, the main light extraction surface is formed on the first main surface side of the auxiliary current diffusion layer, and the light extraction side electrode is disposed so as to cover a part of the first main surface of the auxiliary current diffusion layer. The structure can be made. In this structure, since the transparent thick film semiconductor layer having a thickness of 10 μm or more is disposed on the back side of the element which is the adhesion side of the element chip to the metal stage or the like, the influence of adhesion is affected by the transparent thick film semiconductor layer. There exists an advantage which becomes difficult to reach a light emitting layer part by intervention. For example, when the light emitting element is bonded to the metal stage via the metal paste layer on the transparent thick film semiconductor layer side, the metal paste layer is crushed and deformed during bonding, and the periphery of the transparent thick film semiconductor layer is deformed. May crawl to the side. When this scooped up metal paste reaches the pn junction side surface of the light emitting layer, there may be a problem such as a short circuit of the pn junction. However, as described above, if the thickness of the transparent thick film semiconductor layer provided on the adhesion side is 10 μm or more (desirably 40 μm or more: although there is no upper limit, for example, 200 μm or less), the metal Even if the paste crawls up, the probability of reaching the pn junction is reduced, and problems such as the short circuit can be effectively prevented. The “light extraction surface” of the element refers to the surface of the element from which the luminous flux can be extracted to the outside. The “main light extraction surface” refers to the light extraction surface formed on the main surface of the element chip. It means a surface. In addition to the main light extraction surface, a side surface of a transparent thick film semiconductor layer to be described later can constitute the light extraction surface.

  In order to enhance the current diffusion effect on the first main surface side of the light emitting layer portion provided with the auxiliary current diffusion layer, the following configuration can be adopted. That is, a partial region of the first main surface of the auxiliary current diffusion layer is covered with a current blocking layer, and the light extraction side electrode is electrically connected to the main electrode covering the current blocking layer (a part or all of the current blocking layer). In addition, the auxiliary current diffusion layer is configured to have a sub-electrode that covers a part of the first main surface of the auxiliary current diffusion layer located around the current blocking layer. By providing the sub-electrode as described above, the bias of the electric field distribution in the main light extraction surface can be reduced when a driving voltage is applied, and the voltage can be applied uniformly over the entire main light extraction surface. Therefore, the current spreading effect can be enhanced. Further, by providing the current blocking layer, it is possible to cut off the current directly below the main electrode and increase the amount of current distribution to the background region of the main electrode forming the main light extraction surface, so that the light extraction efficiency can be increased. The current blocking layer may be embedded in the auxiliary current diffusion layer, but when the auxiliary current diffusion layer is formed thin in order to improve heat dissipation, the compound semiconductor layer protrudes from the main light extraction surface position. It is desirable to form a laminate with

  The current blocking layer can be formed as a high-resistance layer made of an insulator layer or a semiconductor layer having a low dopant concentration. However, the current blocking layer is disposed between the auxiliary current diffusion layer and the main electrode, and the auxiliary current diffusion layer and It can also be configured to include an inversion layer having the opposite conductivity type. In this case, when the entire current blocking layer including the inversion layer is formed of a III-V group compound semiconductor, there is an advantage that the current blocking layer can be easily formed by one step of epitaxial growth for manufacturing the semiconductor laminated structure of the light emitting element. . In this case, when the thin auxiliary current diffusion layer is adopted, the current blocking layer is projected from the first main surface of the auxiliary current diffusion layer so as to cover a part of the first main surface. It is advantageous. Further, the main electrode covers the first main surface and the peripheral side surface of the current blocking layer, and the current blocking layer is configured such that the area of the first main surface of the current blocking layer is smaller than the area of the second main surface. It is further desirable to adopt a structure in which the peripheral side surface of the blocking layer is formed as an inclined surface, and the main electrode and the sub electrode forming the light extraction side electrode are formed as an integral metal film. In this case, when a metal film (light extraction side electrode) is formed by a highly directional film formation method such as vapor deposition or sputtering, the peripheral side surface of the current blocking layer is inclined as described above. A metal film can be formed on the peripheral side surface with a sufficient thickness, and the electrical continuity between the main electrode and the sub electrode can be made more reliable.

As another method for enhancing the current spreading effect, it is possible to provide a transparent conductive oxide layer covering the first main surface of the auxiliary current spreading layer. Since the transparent conductive oxide mainly composed of ZnO, SnO ₂ , In ₂ O ₃ or the like can obtain a sufficient current diffusion effect even if the layer thickness is small, the main light extraction surface can be obtained from the second main surface of the active layer. Thus, there is an advantage that the chip first thickness Z reaching the first main surface of the auxiliary current diffusion layer can be further reduced, and the heat dissipation of the element can be further enhanced.

  It is desirable that the transparent thick film semiconductor layer is made of GaP or GaAsP because it has an advantage that it can be easily grown by the HVPE method and a high-quality current diffusion layer can be easily obtained. Further, it is desirable to use a GaAs single crystal substrate having a main axis whose off-angle with respect to the reference direction is 10 ° or more and 20 ° or less with respect to the <100> direction or the <111> direction as a reference direction. In this specification, “having an off-angle” means that the crystal principal axis of the single crystal substrate on which the compound semiconductor layers are stacked is inclined at a certain angle with respect to a reference direction defined as <100> or <111>. Say something.

  When an AlGaInP mixed crystal light emitting layer is grown by the MOVPE method, when a substrate having no off-angle as described above is used, group III atoms are not randomly distributed in the mixed crystal, and an undesirable rule of atomic arrangement And uneven distribution may occur. Such an ordered or biased region has a band gap energy different from that of the originally expected mixed crystal semiconductor, resulting in a distribution in the band gap energy of the entire crystal, resulting in an emission spectrum profile or center. This leads to wavelength variations. However, by imparting an appropriate off-angle to the single crystal substrate, the ordering and bias of the group III elements as described above are greatly reduced, and a light-emitting element with uniform emission spectrum profile and center wavelength can be obtained. . Further, when a transparent thick film semiconductor layer made of a III-V compound semiconductor is formed on the mixed crystal light emitting layer portion grown by such MOVPE method by using the HVPE method, the above-mentioned off-angle is given. In the case of using the single crystal substrate, the facet and surface roughness caused by the crystal hardly occur on the surface of the current diffusion layer finally obtained, and as a result, a transparent thick film semiconductor layer with good quality can be obtained.

  When the above-mentioned off-angle is less than 1 °, the effect of suppressing variation in the emission characteristics (emission spectrum profile and center wavelength) is poor, and when it exceeds 25 °, there is a problem that normal light-emitting layer portion growth becomes impossible. More preferably, it is more desirable to use a GaAs single crystal substrate having a main axis with an off angle of 10 ° to 20 °. When a GaAs single crystal substrate having such a high off-angle is used, the effect of smoothing the surface of the transparent thick film semiconductor layer obtained by the HVPE method is further enhanced. As a result of studies by the present inventors, when a GaAs single crystal substrate having an off angle of 1 ° or more and less than 10 ° is used, the surface of the transparent thick film semiconductor layer obtained by the HVPE method has a small facet-like amplitude. Although the formation of such irregularities is effectively prevented, there are cases where not a few crystal defects with a large amplitude remain, which may lead to defects. However, it has been found that when the off-angle is increased to a range of 10 ° or more and 20 ° or less, the occurrence of such projecting crystal defects can be effectively suppressed.

  In addition, in order to obtain a transparent thick film semiconductor layer having a smooth and good surface state, including prevention of protrusion-like crystal defects, it is also considered in the process to optimize the growth temperature of the transparent thick film semiconductor layer by the HVPE method. It is an important point to be done. One of the important effects is that when the off-angle is set in the range of 10 ° to 20 °, the appropriate growth temperature range of such a transparent thick film semiconductor layer can be lowered to the low temperature side. . If the growth temperature of the transparent thick film semiconductor layer can be lowered, the above-described thermal history applied to the light emitting layer part that forms the base of the transparent thick film semiconductor layer can be further alleviated, and diffusion deterioration of the dopant profile of the light emitting layer part can be reduced. Hard to occur. In the case of a light emitting layer portion having a double hetero structure, there is a demand to reduce the dopant concentration of the active layer as much as possible in order to increase the efficiency of light emission recombination. Therefore, by reducing the growth temperature of the transparent thick film semiconductor layer and suppressing dopant diffusion from the cladding layer side to the active layer side, the internal quantum efficiency of the light emitting device can be increased, and the light emission performance is greatly improved. can do. Moreover, since the layer thickness of the transparent thick film semiconductor layer can be increased while maintaining the above dopant profile well by reducing the growth temperature, the light emission when the transparent thick film semiconductor layer is thickened to 10 μm or more in particular. There is also an advantage that the strength improvement effect is particularly remarkable.

  When the off-angle is less than 10 ° or the off-angle exceeds 20 °, the effect of preventing the occurrence of projection-like crystal defects and the effect of lowering the appropriate growth temperature of the transparent thick film semiconductor layer may be insufficient. . The off-angle is more preferably set to 13 ° to 17 °.

  When a transparent thick film semiconductor layer made of GaAsP is grown by a hydride vapor phase growth method, it is desirable to set the growth temperature to a temperature of 700 ° C. or higher and 800 ° C. or lower. If the growth temperature is less than 700 ° C., the effect of smoothing the surface of the transparent thick film semiconductor layer, particularly the effect of suppressing the occurrence of projection-like crystal defects, cannot be obtained sufficiently. On the other hand, if it exceeds 800 ° C., the effect of preventing the diffusion deterioration of the dopant profile of the light emitting layer portion cannot be sufficiently achieved. The growth temperature is more preferably set to 720 ° C. or higher and 770 ° C. or lower (especially when the off-angle is 13 ° or higher and 17 ° or lower). In addition, with such a temperature setting, the effect of improving the emission intensity is particularly remarkable when the transparent thick film semiconductor layer is thickened to 10 μm or more (200 μm or less).

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing a light emitting device 100 according to an embodiment of the present invention. The light-emitting element 100 includes a light-emitting layer portion 24 made of a III-V group compound semiconductor and a photon energy corresponding to the peak wavelength of the luminous flux emitted from the light-emitting layer portion 24 and formed on the second main surface side of the light-emitting layer portion 24. And a transparent thick film semiconductor layer 90 made of a III-V compound semiconductor having a larger band gap energy.

The light emitting layer portion 24 is lattice-matched with GaAs among the compounds represented by the composition formula (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1). The first conductivity type cladding layer 4, the active layer 5 and the second conductivity type cladding layer 6 each composed of a compound having a composition having the above composition have a double heterostructure laminated in this order. Specifically, the active layer 5 made of a non-doped (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 0.55, 0.45 ≦ y ≦ 0.55) mixed crystal is used. p-type _{(Al z Ga 1-z)} y In 1-y P ( except x <z ≦ 1) p-type cladding layer composed of (second-conductivity-type cladding layer) 6 and n-type _{(Al z Ga 1-z) It} has a structure sandwiched by an n-type cladding layer (first conductivity type cladding layer) 4 made of _y In _1-y P (where x <z ≦ 1). 1, the n-type AlGaInP cladding layer 4 is disposed on the first main surface side (upper side in the drawing), and the p-type AlGaInP cladding layer 6 is disposed on the second main surface side (lower side in the drawing). ing. The term “non-dope” as used herein means “does not actively add dopant”, and contains a dopant component inevitably mixed in a normal manufacturing process (for example, 1 × 10 ¹³ to 1 × The upper limit of about 10 ¹⁶ / cm ³ is not excluded. The light emitting layer portion 24 is grown by the MOVPE method.

  The n-type cladding layer 4 and the p-cladding layer 6 have a thickness of, for example, 0.8 μm or more and 4 μm or less (preferably 0.8 μm or more and 2 μm or less), and the active layer 5 has a thickness of 0.4 μm or more and 2 μm or less, for example. (Desirably 0.4 μm or more and 1 μm or less). The total thickness of the light emitting layer portion 24 is, for example, 2 μm to 10 μm (desirably 2 μm to 5 μm).

The transparent thick film semiconductor layer 90 serves as a support substrate for the thin light emitting layer 24 and also functions as a light extraction layer from the light emitting layer portion 24, and has a thickness of 10 μm to 200 μm (preferably 40 μm to 100 μm). By being formed in a thick film, it plays a role of increasing the extracted light flux from the side surface of the layer and increasing the brightness of the entire light emitting element (integrated sphere brightness). Further, the transparent layer is made of a III-V group compound semiconductor having a band gap energy larger than the photon energy corresponding to the peak wavelength of the luminous flux from the light emitting layer 24, specifically, GaP or GaAsP. Light absorption in the thick semiconductor layer 90 is also suppressed. The transparent thick film semiconductor layer 90 is grown by the HVPE method, and its C and H concentrations can be set smaller than the light emitting layer portion 24 (usually about 15 × 10 ¹⁷ / cm ³ ) by the MOVPE method. In the present embodiment, the transparent thick film semiconductor layer 90 is p-type, and the light-emitting layer portion 24 laminated thereon is p-type cladding layer 6, active layer 5, n-type cladding from the p-type transparent thick film semiconductor layer 90 side. The layers 4 are stacked in this order. However, the transparent thick film semiconductor layer 90 may be n-type, and the stacking order of the light emitting layer portions 24 may be the reverse order described above.

  A connection layer 7 made of a GaP (which may be GaAsP or AlGaAs) layer is provided between the transparent thick film semiconductor layer 90 made of a GaP (or GaAsP or AlGaAs) layer and the light emitting layer 24. Is formed by the MOVPE method. The connection layer 7 is an AlGaInP that gradually changes the lattice constant difference (and hence the mixed crystal ratio) between the light emitting layer portion 24 made of AlGaInP and the transparent thick film semiconductor layer 90 made of GaP (or GaAsP). It is good also as a layer.

Next, an auxiliary current diffusion layer 91 made of AlGaInP having a composition lattice-matched with GaAs is formed on the first main surface side of the light emitting layer portion 24 with a film thickness smaller than that of the transparent thick film semiconductor layer 90 by the MOVPE method. ing. Specifically, the auxiliary current diffusion layer 91 is expressed by a composition formula (Al _{x ′} Ga _{1−x ′} ) _{y ′} In _{1−y ′} P (where 0 ≦ x ′ ≦ 1, 0 ≦ y ′ ≦ 1). Among the compounds represented, the compound is composed of a compound having a lattice matching with GaAs and having an Al mixed crystal ratio x ′ larger than that of the active layer. In the present embodiment, the Al mixed crystal ratio x ′ of the auxiliary current diffusion layer 91 is set smaller than the Al mixed crystal ratio x of the n-type cladding layer 4 constituting the first conductivity type cladding layer.

  For example, when the luminous flux from the active layer 5 emits red light with a center wavelength of 630 nm, the Al content of AlGaInP lattice-matched with GaAs and having a band gap energy corresponding to the center wavelength is about 1 mol%. It is. If the band gap energy of the auxiliary current diffusion layer 91 is higher than this (that is, if the Al content is high: hereinafter referred to as the absorption limit Al content), it is difficult to cause absorption of the luminous flux. On the other hand, when AlGaAs is used as the auxiliary current diffusion layer 91, the absorption limit Al content is about 25 mol%, which is considerably higher than that in the case of being composed of AlGaInP. Similarly, when the luminous flux from the active layer 5 emits yellow light with a central wavelength of 590 nm, if the auxiliary current diffusion layer 91 is made of AlGaAs, the absorption limit Al content is about 50 mol%, whereas the auxiliary current is made of AlGaInP. If the diffusion layer 91 is configured, the absorption limit Al content can be significantly reduced to about 10 mol%.

Specific composition setting examples of each layer in the case of red light emission are shown below:
p-type cladding layer 6: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Active layer 5: (Al _0.04 Ga _0.96 ) _0.5 In _0.5 P
n-type cladding layer 4: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Auxiliary current diffusion layer 91: (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P

Moreover, specific composition setting examples of each layer in the case of yellow light emission are shown below:
p-type cladding layer 6: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Active layer 5: (Al _0.3 Ga _0.7 ) _0.5 In _0.5 P
n-type cladding layer 4: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Auxiliary current diffusion layer 91: (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P

  The auxiliary current diffusion layer 91 functions as a layer that forms a main light extraction surface on the first main surface side of the light emitting layer portion 24. The auxiliary current diffusion layer 91 preferably has an effective carrier concentration (n-type dopant concentration) adjusted to be higher than that of the cladding layer 4, and has a thickness of, for example, 0.5 μm to 30 μm (preferably 1 μm to 15 μm). It is. A light extraction side electrode 9 is formed on the first main surface of the auxiliary current diffusion layer 91 so as to cover a part of the first main surface, and a main light extraction surface EA is formed around the light extraction side electrode 9. The light extraction side electrode 9 is formed of an Au thin film, and one end of the electrode wire 9w is joined. Further, a bonding alloyed layer 9a is formed between the auxiliary current diffusion layer 91 and the light extraction side electrode 9 in order to reduce the contact resistance between them. The bonded alloyed layer 9a is a contact containing Au or Ag as a main component (50% by mass or more), and an appropriate amount of an alloy component for taking ohmic contact according to the type and conductivity type of the semiconductor to be contacted. It is formed by forming a metal film on the semiconductor surface and then performing an alloying heat treatment (so-called sintering process). Here, in order to make contact with the n-type layer, the bonded alloyed layer 9a is formed using an AuGeNi alloy (for example, Ge: 15% by mass, Ni: 10% by mass, balance Au).

  The second main surface side of the transparent thick film semiconductor layer 90 is bonded to the metal stage 52 via the metal paste layer 17 made of Ag paste or the like, and the metal paste layer 17 forms a reflection portion. Further, the bonding alloyed layer 21 is formed in a dispersed manner on the second main surface of the transparent thick film semiconductor layer 90 in the same manner as the light extraction side electrode 9 side, and the bonding alloyed layer 21 is covered with the metal paste layer 17. Yes. Thereby, the light emitting layer part 24 is electrically connected to the metal stage 52 through the metal paste layer 17. On the other hand, the light extraction side electrode 9 is electrically connected to the conductor metal fitting 51 via a current-carrying wire 9w made of Au wire or the like. A light emission driving voltage is applied to the light emitting layer portion 24 via a drive terminal portion (not shown) integrated with the metal stage 52 and the conductor metal fitting 51.

  In this embodiment, the bonding alloyed layer 21 is formed using an AuBe alloy in order to make contact with the p-type layer. Since the bonding alloyed layer 21 has a relatively low reflectance, a transparent thick film semiconductor is considered in consideration of the balance between the effect of increasing the reflected light flux in the region and the effect of reducing the contact resistance with the bonding alloyed layer 21. It is desirable to adjust the ratio of the formation area of the bonding alloying layer 21 to the total area of the second main surface of the layer 90 to 1% or more and 25% or less. The bonded alloying layer 21 is covered with a highly reflective metal reflective layer 32 such as an Au layer, an Ag layer, or an Al layer, and the metal reflective layer 32 is adhered to the metal stage 52 via the metal paste layer 17. Also good.

  When the light emitting element is bonded to the metal stage 52 through the metal paste layer 17 on the transparent thick film semiconductor layer 90 side, the metal paste layer 17 is crushed during the bonding as shown in FIG. In some cases, the transparent thick film semiconductor layer 90 may be deformed and crawl up to the peripheral side surface side. However, if the thickness of the transparent thick film semiconductor layer 90 provided on the bonding side is made as thick as 40 μm or more and 200 μm or less, the probability of reaching the light emitting layer portion (pn junction) 24 even if the metal paste rises. Becomes small, and a pn junction short circuit or the like can be effectively prevented.

  The transparent thick film semiconductor layer 90 and the light emitting layer portion 24 form an element chip having a square planar shape, the dimension of one side of which is X, and the auxiliary current diffusion layer 91 from the second main surface of the active layer 5. X ≧ 150 μm, where Z is the first chip thickness that reaches the first main surface of Y and Y is the second chip thickness from the second main surface of the active layer 5 to the second main surface of the transparent thick film semiconductor layer 90, The dimensions of each part are determined so as to satisfy 200 μm ≧ Y ≧ 11 μm, Z / Y ≦ 0.2, and Y / X ≦ 0.5. The reason why X ≧ 150 μm is that the element is used as a surface light emitting element such as a high-luminance display element or an illumination element, and there is no upper limit, but for example, a large-area element of about X = 40 mm is made. Is also possible. On the other hand, the second chip thickness Y including the transparent thick film semiconductor layer 90 is determined so as to satisfy 200 μm ≧ Y ≧ 11 μm, so that the light extraction effect from the side surface portion 90S of the transparent thick film semiconductor layer 90 is sufficient. This is to improve the brightness of the integrating sphere of the element. In consideration of the formation efficiency of the transparent thick film semiconductor 90 by the HVPE method, the upper limit of the second chip thickness Y is more preferably 100 μm or more.

  Moreover, in the light emitting element 100 of FIG. 1, the transparent thick film semiconductor layer is provided only on the second main surface side of the light emitting layer portion 24, and satisfies Z / Y ≦ 0.2 and Y / X ≦ 0.5. Thus, the dimension X of one side of the element and the first chip thickness Y are respectively determined. In the case of an element having a large area, the current flowing through the element during light emission driving is also considerably large. However, the chip thickness Z is 0.2 on the first main surface side of the element at a relative value Z / Y with respect to the second chip thickness Y. By forming the thin film as follows, Joule heat generated when a large current is applied can be efficiently dissipated, which contributes to the improvement of the element life. Moreover, although it is a large area chip, it contributes to the low profile.

In the configuration of the element, since the thickness of the auxiliary current diffusion layer 91 disposed on the main light extraction surface side is relatively small, the auxiliary current diffusion layer 91 has a relatively small thickness. The dopant concentration of the current diffusion layer 91 (which becomes the majority carrier source) should be higher than the dopant concentration of the transparent thick film semiconductor layer 90 (for example, 2 × 10 ¹⁸ / cm ³ or more and 5 × 10 ¹⁹ / cm ³ or less). desirable.

On the other hand, since the transparent thick film semiconductor layer 90 is sufficiently thick, it is possible to easily obtain a sheet resistance value that does not hinder light emission driving without increasing the dopant concentration so much. Then, as will be described in detail later, when the wafer is diced into element chips, the entire transparent thick film semiconductor layer 90 is promoted in order to promote chemical etching for removing a processing damage layer generated on the side surface portion 90S. Is adjusted to a relatively low level of 5 × 10 ¹⁶ / cm ³ or more and 2 × 10 ¹⁸ / cm ³ or less.

Hereinafter, a method for manufacturing the light emitting device 100 of FIG. 1 will be described.
First, as shown in Step 1 of FIG. 2, an n-type GaAs single crystal substrate 1 provided with an off-angle is prepared as a growth substrate. The substrate 1 has a main axis A with the <100> direction as a reference direction and an off angle with respect to the reference direction of 10 ° to 20 ° (preferably 13 ° to 17 °: 15 ° in the present embodiment). It is. Next, as shown in step 2, an auxiliary current diffusion made of, for example, 0.5 μm of n-type GaAs buffer layer 2 and n-type AlGaInP is formed on the second main surface (shown as the upper surface in the drawing) of the substrate 1. The layer 91 is epitaxially grown, for example, at 5 μm. The dopant concentration at this stage of the auxiliary current diffusion layer 91 is, for example, 1 × 10 ¹⁷ / cm ³ or more and 2 × 10 ¹⁸ / cm ³ or less.

Next, as the light emitting layer portion 24, an n-type cladding layer 4 (n-type dopant is Si) having a thickness of 1 μm, each made of (Al _x Ga _1-x ) _y In _1-y P, and an active layer having a thickness of 0.6 μm. A layer (non-doped) 5 and a p-type cladding layer 6 having a thickness of 1 μm (p-type dopant is Mg: C from organometallic molecules can also contribute as a p-type dopant) are epitaxially grown in this order. Each dopant concentration of the p-type cladding layer 6 and the n-type cladding layer 4 is, for example, 1 × 10 ¹⁷ / cm ³ or more and 2 × 10 ¹⁸ / cm ³ or less. Further, as shown in step 3 of FIG. 3, the connection layer 7 is epitaxially grown on the n-type cladding layer 4.

Epitaxial growth of each of the above layers is performed by a known MOVPE method. The following materials can be used as source gases for the source components of Al, Ga, In (indium), and P (phosphorus);
Al source gas; trimethylaluminum (TMAl), triethylaluminum (TEAl), etc .;
Ga source gas; trimethylgallium (TMGa), triethylgallium (TEGa), etc .;
In source gas; trimethylindium (TMIn), triethylindium (TEIn), etc.
P source gas: trimethyl phosphorus (TMP), triethyl phosphorus (TEP), phosphine (PH ₃ ), etc.

Proceeding to step 4 in FIG. 3, a transparent thick film semiconductor layer 90 made of p-type GaP (or GaAsP may be used) is grown by HVPE. Specifically, in the HVPE method, GaCl, which is a group III element, is heated and held at a predetermined temperature in a container, and hydrogen chloride is introduced onto the Ga, thereby causing GaCl by the reaction of the following formula (1). And is supplied onto the substrate together with H ₂ gas which is a carrier gas.
Ga (liquid) + HCl (gas) → GaCl (gas) + 1 / 2H ₂ (1)
In the case of GaP, the growth temperature is set to, for example, 640 ° C. or more and 860 ° C. or less. Further, P, which is a group V element, supplies PH ₃ onto the substrate together with H ₂ which is a carrier gas. Furthermore, Zn which is a p-type dopant is supplied in the form of DMZn (dimethyl Zn). GaCl is excellent in reactivity with PH _3, and the transparent thick film semiconductor layer 90 can be efficiently grown by the reaction of the following formula (2):
GaCl (gas) + PH ₃ (gas)
→ GaP (solid) + HCl (gas) + H ₂ (gas) (2)

When the transparent thick film semiconductor layer 90 is formed by the HVPE method, a very smooth layer surface can be obtained even though the off-angle is given to the substrate 1. When a GaAs single crystal substrate having a main axis with an off angle of 10 ° to 20 ° (preferably 13 ° to 17 °) is used, a projecting crystal with a large amplitude on the surface of the transparent thick film semiconductor layer 90 is used. An appropriate growth temperature of the transparent thick film semiconductor layer 90 by the HVPE method is 640 ° C. or higher and 750 ° C. or lower (more preferably 680 ° C. or higher and 720 ° And lower the diffusion of dopant from the p-type cladding layer 6 and the n-type cladding layer 4 to the active layer 5, and hence the diffusion degradation of the dopant profile of the light emitting layer portion 24. . On the other hand, when GaAsP (GaAs _1-a P _a : 0.5 ≦ a ≦ 0.9) is employed, AsH ₃ is used together with PH ₃ in the formula (2), and the growth temperature is higher than that of GaP. Set 20-30 ° C lower.

  When the growth of the transparent thick film semiconductor layer 90 is completed, the process proceeds to step 5 in FIG. 4, where the GaAs substrate 1 is removed by chemical etching using an etchant such as an ammonia / hydrogen peroxide mixture, and the auxiliary current diffusion layer is obtained. A wafer with 91 exposed is obtained. When the above steps are completed, the dopant is further diffused into the auxiliary current diffusion layer 91 as necessary, and the first main surface of the auxiliary current diffusion layer 91 and the transparent thick film semiconductor layer 90 are formed by sputtering or vacuum evaporation. A metal layer for forming a bonded alloying layer is formed on each of the second main surfaces, and heat treatment for alloying (so-called sintering process) is performed to form bonded alloyed layers 9a and 21 (see FIG. 1). . The auxiliary current diffusion layer 91 is made of AlGaInP having a lower Al content than AlGaAs having the same band gap energy, and the amount of Al oxide formed on the surface of the layer during the etching is small, and the bonded alloy after sintering treatment It is easy to reduce the junction resistance with the chemical layer 9a. The light extraction surface side electrode 9 and the back surface electrode 15 are formed so as to cover the bonding alloyed layers 9a and 21 respectively. Subsequently, as shown in Step 6, the wafer after electrode formation is separated into individual element chips by dicing.

  As a result of the above dicing, as shown in FIG. 5, a processing damage layer 90 d having a predetermined thickness is formed on the side surface portion 90 </ b> S of the transparent thick film semiconductor layer 90. A large number of crystal defects included in the processing damage layer 90d cause current leakage and scattering when light is applied, so that the processing damage layer 90d is removed by chemical etching. As the etchant, a sulfuric acid-hydrogen peroxide aqueous solution is used. As the aqueous solution, for example, a sulfuric acid: hydrogen peroxide: water weight ratio of 20: 1: 1 can be used, and the liquid temperature is adjusted to 30 ° C. or more and 60 ° C. or more.

  In the transparent thick film semiconductor layer 90, if the processing damage layer 90d forming the side surface is not removed by etching, the extracted light flux from the side surface portion 90S is remarkably reduced. Specifically, when the transparent thick film semiconductor layer 90 is thickened, although the area of the side surface is increased, light extraction from the side surface is hindered by the processing damage layer 90d. As indicated by a broken line, the increase in the integrating sphere luminance of the element with respect to the film thickness reaches a peak at a small film thickness level of about 20 μm. That is, the merit of thickening the transparent thick semiconductor layer 90 is almost lost. This tendency hardly changes even if the dopant concentration of the transparent thick film semiconductor layer 90 changes.

On the other hand, if the chemical etching is performed, the processing damage layer 90d that hinders the light extraction is removed, so that the light extraction from the side surface becomes conspicuous, and the integral sphere brightness increases as the film thickness of the transparent thick film semiconductor layer 90 increases. It is expected to increase. However, when a dopant exceeding 2 × 10 ¹⁸ / cm ³ is added to the transparent thick film semiconductor layer 90, as shown by the one-dot chain line in FIG. I found it not big. This is presumably because the dopant atoms act as solute atoms that pin the dislocation movement, so that the introduction of dislocations into the transparent thick film semiconductor layer during single crystal growth is suppressed, and the progress of chemical etching becomes slow.

As a result, as shown in the lower right of FIG. 5, the processing damage layer 90d cannot be sufficiently removed, and the remaining processing damage layer 90d ′ prevents light extraction, so that the luminance improvement corresponding to the layer thickness of the transparent thick film semiconductor layer 90 is achieved. The effect cannot be obtained (the case where the dopant concentration is 1 × 10 ¹⁹ / cm ³ is illustrated). However, when the dopant concentration of the transparent thick film semiconductor layer 90 is kept at a low value of 2 × 10 ¹⁸ / cm ³ or less, the dislocation pinning effect due to the solute atoms is conversely suppressed. The amount of dislocations introduced into layer 90 increases. Accordingly, since the chemical etching rate is also improved, the damaged layer 90d can be removed smoothly and sufficiently. As a result, when the layer thickness of the transparent thick film semiconductor layer 90 is increased, the light extraction improvement effect from the side surface becomes remarkable, and as shown by the solid line in FIG. 6 (the dopant concentration is 1 × 10 ¹⁸ / cm ³ . Integral sphere brightness after etching is dramatically improved, especially in the region where the layer thickness is 40 μm or more, and the integral sphere brightness is increased by 1.5 to 2 times than without chemical etching. Can be made.

  Hereinafter, various modifications of the light emitting device of the present invention will be described. In addition, since there are many common parts with the light emitting element 100 of FIG. 1, the difference will be described below. Therefore, since parts other than the differences described below have the same configuration as that of the light emitting element 100 of FIG. 1, detailed description thereof will not be repeated here. Also, common reference numerals are assigned to common components.

  In the light emitting device 200 of FIG. 7, a current blocking layer 1r is formed on the first main surface of the auxiliary current diffusion layer 91 so as to cover a partial region of the first main surface. A main electrode 9m that covers the first main surface and the peripheral side surface of the blocking layer 1r, and a partial area of the first main surface of the auxiliary current diffusion layer 91 that covers a part of the first main surface and extends from the outer peripheral edge of the main electrode 9m And an electrode 9b. The current blocking layer 1r is configured to have a conductivity type opposite to that of the auxiliary current diffusion layer 91, for example, from GaAs. In addition, the linear sub-electrode 9b is radially formed on the main light extraction surface EA with the main electrode 9m as the center in the present embodiment. By forming the sub-electrode 9b as described above, the bias of the electric field distribution in the main light extraction surface can be reduced when the drive voltage is applied, and the entire main light extraction surface EA is more uniformly distributed. A voltage can be applied, and the current spreading effect can be enhanced.

  In the present embodiment, the bonding alloyed layer 9a is also formed in a linear shape overlapping with the sub electrode 9b, and no bonding alloyed layer is formed in the current blocking layer 1r located immediately below the main electrode 9m. Therefore, the current blocking layer 1r can block the current directed directly below the main electrode 9m. As a result, the amount of current distribution to the background area of the main electrode 9m that forms the main light extraction surface EA can be increased, and the light extraction efficiency can be increased.

  The peripheral surface of the current blocking layer 1 is formed as an inclined surface 1s so that the area of the first main surface of the current blocking layer 1r is smaller than the area of the second main surface, and the light extraction side electrode 9 is The main electrode 9m and the sub electrode 9b are formed as an integral metal film. When a metal film is formed by a highly directional film forming method such as vapor deposition or sputtering, the peripheral side surface 1s of the current blocking layer 1r is inclined as described above, so that a sufficient metal film is formed on the peripheral side surface 1s. Therefore, electrical connection between the main electrode 9m and the sub electrode 9b can be reliably performed. The main electrode covering the current blocking layer 1 has a large area, and the connection of the energization wire 9w is easy.

  The current blocking layer 1r having the inclined side surface 1s as an inclined surface can be formed as follows. First, as shown in step 1 of FIG. 8, an etch stop layer 1p made of AlInP is formed between the GaAs layer 1 'to be the current blocking layer 1r and the light emitting layer portion 24. Next, as shown in step 2, the region to be left as the current blocking layer 1r in the second main surface of the GaAs layer 1 ′ (with the plane orientation <100>) is covered with the etching resist MSK, and the remaining portion is covered. Then, mesa etching is performed using an ammonia-hydrogen peroxide aqueous solution as an etching solution. The peripheral side surface of the current blocking layer 1r becomes an inclined surface due to the anisotropic etching effect of the etching solution. Then, as shown in step 3, the etch stop layer 1p is removed using hydrochloric acid as an etchant, and the etching resist MSK is further removed.

  In the light emitting device 300 of FIG. 9, the main body layer 1m made of GaAs is formed on the side close to the main body layer 1m, of the p-type layer portion and the n-type layer portion that form a pn junction in the light emitting layer portion 24. (Ie, n-type cladding layer 4) and the same conductivity type (ie, n-type). An inversion layer portion 93 made of a compound semiconductor having a conductivity type opposite to that of the main body layer 1m (that is, p-type) is provided between the light emitting layer portion 24 and the main body layer 1m so as to selectively cover the main body layer 1m. Is inserted. The main body layer 1m and the inversion layer portion 93 constitute a current blocking layer.

  7 and 9, in each case, an inversion pn junction that is reverse-biased during light emission driving is formed between the current blocking layer 1r and the light emitting layer 24, and the current generated by the current blocking layer 1r. The function as a blocking layer can be further enhanced. Therefore, even if the bonding alloyed layer 9a is configured to cover the current blocking layer 1r together with the sub electrode 9b, the current blocking effect can be achieved without any problems due to the interposition of the inverted pn junction. Therefore, if this is utilized, as shown in FIG. 9, the bonding alloyed layer 9a contacts the sub electrode 9b in a shape matched with the light extraction side electrode 9 having the sub electrode 9b and the main electrode 9m. It is possible to form the current blocking layer 1r as well as the bottom surface region of the notch 1j in a lump (in the figure, the portion covering the current blocking layer 1r is represented by reference numeral 9k). Thus, the joining alloying layer 9a (9k) and the light extraction side electrode 9 overlapping in the same shape can be patterned in one photolithography, which contributes to simplification of the process.

In the light emitting element 400 shown in FIG. 10, a transparent conductive oxide layer (ZnO, SnO ₂ , In ₂ O _3, etc.) 96 that forms a light extraction surface is disposed immediately below the light extraction side electrode 9, and the current flows. Increases the diffusion effect. Here, a transparent conductive oxide layer 96 is provided so as to cover the main surface of the thin auxiliary current diffusion layer, and the background of the light extraction side electrode 9 is provided between the transparent conductive oxide layer 96 and the auxiliary current diffusion layer 91. A bonding layer 97 made of GaAs or the like for reducing the contact resistance between the transparent conductive oxide layer 96 and the auxiliary current diffusion layer 91 is dispersedly formed in the region forming

The schematic diagram which shows the 1st example of the light emitting element of this invention by laminated structure. Explanatory drawing which shows the manufacturing process of the light emitting element of FIG. Explanatory drawing following FIG. Explanatory drawing following FIG. The figure explaining a mode that the removal state by the chemical etching of the process damage layer of the side surface of a transparent thick film semiconductor layer changes with the dopant concentration of a transparent thick film semiconductor layer. The graph which illustrates how the integrating sphere brightness | luminance of an element before the removal of a process damage layer and after a removal changes with the thickness and dopant concentration of a transparent thick film semiconductor layer. The schematic diagram which shows the principal part of the 2nd example of the light emitting element of this invention by laminated structure. Process explanatory drawing which shows the formation method of the electric current blocking layer by which the surrounding side surface became the inclined surface. The schematic diagram which shows the principal part of the 3rd example of the light emitting element of this invention by laminated structure. The schematic diagram which shows the principal part of the 4th example of the light emitting element of this invention by laminated structure.

Explanation of symbols

1 GaAs single crystal substrate 4 n-type cladding layer (second conductivity type cladding layer)
5 active layer 6 p-type cladding layer (first conductivity type cladding layer)
9 Light extraction surface side electrode 20, 90 Transparent thick film semiconductor layer 24 Light emitting layer portion 91 Auxiliary current diffusion layer 100, 200, 300, 400 Light emitting element

Claims (9)

Among compounds represented by the composition formula (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), a compound having a composition that lattice matches with GaAs A light emitting layer portion having a double hetero structure in which a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer each formed in this order are laminated,
The main surface side formed by the first conductivity type cladding layer of the light emitting layer portion is the first main surface side, and has a band gap energy larger than the photon energy corresponding to the peak wavelength of the luminous flux from the light emitting layer portion. A transparent thick film semiconductor layer in which a group III-V compound semiconductor is formed to a thickness of 10 μm or more by hydride vapor phase epitaxy on the second main surface side of the light emitting layer portion;
On the first main surface side of the light emitting layer portion, it is formed thinner than the transparent thick film semiconductor layer by the MOVPE method, and the composition formula (Al _{x ′} Ga _{1−x ′} ) _{y ′} In _{1−y ′} P (where, Among compounds represented by 0 ≦ x ′ ≦ 1, 0 ≦ y ′ ≦ 1), the compound has a composition that lattice-matches with GaAs and has a larger Al mixed crystal ratio x ′ than the active layer. An auxiliary current spreading layer,
A light-emitting element including:   2. The light emitting device according to claim 1, wherein an Al mixed crystal ratio x ′ of the compound forming the auxiliary current diffusion layer is smaller than that of the first conductivity type cladding layer.   A main light extraction surface is formed on the first main surface side of the auxiliary current diffusion layer, and a light extraction side electrode is disposed so as to cover a part of the first main surface of the auxiliary current diffusion layer. The light emitting device according to claim 1 or 2.   A partial region of the first main surface of the auxiliary current diffusion layer is covered with a current blocking layer, and the light extraction side electrode is electrically connected to the main electrode covering the current blocking layer and the main electrode and the auxiliary electrode 4. The light emitting device according to claim 3, further comprising: a sub-electrode that covers a part of the first main surface of the current diffusion layer located around the current blocking layer. 5.   5. The current blocking layer includes an inversion layer disposed between the auxiliary current diffusion layer and the main electrode and having a conductivity type opposite to that of the auxiliary current diffusion layer. The light emitting element of description.   The entire current blocking layer including the inversion layer is formed of a III-V group compound semiconductor, and the current blocking layer extends from a first main surface of the auxiliary current diffusion layer to a partial region of the first main surface. The main electrode is formed so as to cover the first main surface and the peripheral side surface of the current blocking layer, and the area of the first main surface of the current blocking layer is larger than the area of the second main surface. The peripheral surface of the current blocking layer is formed as an inclined surface so as to be small, and the main electrode and the sub electrode forming the light extraction side electrode are formed as an integral metal film. The light emitting device according to claim 5.   The light-emitting element according to claim 1, wherein the transparent thick film semiconductor layer is made of GaP or GaAsP.   The auxiliary current diffusion layer, the light emitting layer portion, and the transparent thick film semiconductor layer have a main axis whose off angle with respect to the reference direction is 10 ° or more and 20 ° or less with the <100> direction or the <111> direction as a reference direction. The light emitting device according to any one of claims 1 to 7, wherein the light emitting device is formed by epitaxial growth in this order on a GaAs single crystal substrate. A method for manufacturing a light emitting device according to any one of claims 1 to 8,
It is thinner than the transparent thick film semiconductor layer, and is represented by a composition formula (Al _{x ′} Ga _{1−x ′} ) _{y ′} In _{1−y ′} P (where 0 ≦ x ′ ≦ 1, 0 ≦ y ′ ≦ 1). The auxiliary current diffusion layer made of a compound having a lattice-matching composition with GaAs and having an Al mixed crystal ratio x ′ larger than that of the active layer is formed on the second GaAs single crystal substrate by MOVPE. An auxiliary current diffusion layer growth step for epitaxial growth on the main surface;
Compound represented by the composition formula (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) on the second main surface side of the auxiliary current diffusion layer. A light emitting layer portion having a double hetero structure in which the first conductive type cladding layer, the active layer, and the second conductive type cladding layer, each of which is formed of a compound lattice-matched with GaAs, are stacked in this order. A light emitting layer portion growth step of epitaxially growing the substrate by MOVPE,
The transparent thick film semiconductor layer made of a III-V group compound semiconductor having a band gap energy larger than a photon energy corresponding to a peak wavelength of a luminous flux from the light emitting layer portion on the second main surface side of the light emitting layer portion A transparent thick film semiconductor layer growth step of epitaxially growing the layer to a thickness of 10 μm or more by hydride vapor phase growth method;
A substrate removal step of removing the GaAs single crystal substrate from the first main surface side of the auxiliary current diffusion layer;
A method for manufacturing a light-emitting element, comprising:

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