Vertical resonator type light-emitting element and light-emitting device

Abstract

The present invention provides a vertical resonator type light-emitting element and a light-emitting device that stabilize the voltage applied between the electrodes of the light-emitting element. [Solution] The substrate comprises a first multilayer reflector, a first semiconductor layer of a first conductivity type, a first electrode formed in a region outside the central region including the center of the first semiconductor layer on the upper surface when viewed from a direction perpendicular to the upper surface of the first semiconductor layer, having an inner surface which is a side close to the central region and an outer surface which is a side far from the central region, a light-emitting layer formed in the central region of the first semiconductor layer, a second semiconductor layer of a second conductivity type, a second electrode, a second multilayer reflector on the second electrode, a first electrode pad on the first electrode and a second electrode pad on the second electrode, wherein the first electrode contains a first metal, the first electrode pad contains a second metal different from the first metal and has an extended portion extending on the outer surface of the first electrode, and a part of the interior region of the first electrode is a resistance region with higher electrical resistance than the surrounding region of the interior region of the first electrode.

Description

Technical Field

[0001] The present invention relates to a vertical cavity surface emitting laser and a light emitting device including the vertical cavity surface emitting laser.

Background Art

[0002] As one type of semiconductor laser, a vertical cavity surface emitting laser is known. For example, Patent Document 1 discloses a vertical cavity surface emitting laser (Vertical Cavity Surface Emitting Laser: VCSEL) that forms an optical resonator with two multilayer film reflectors facing each other and a semiconductor structure layer including an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer disposed therebetween.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the vertical cavity surface emitting laser (hereinafter also referred to as surface emitting laser) disclosed in Patent Document 1, for example, when the surface emitting laser is continuously driven, the voltage applied between the n electrode connected to the n-type semiconductor layer and the p electrode connected to the p-type semiconductor layer may change with time. If such a situation occurs, for example, it may affect the light output of the surface emitting laser.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a vertical cavity surface emitting laser capable of stabilizing the voltage applied between the electrodes of the light emitting element and a light emitting device including the vertical cavity surface emitting laser.

Means for Solving the Problems

[0006] The vertical resonator type light-emitting element according to the present invention comprises a light-transmitting substrate, a first multilayer reflector formed on the substrate, a first semiconductor layer of a first conductivity type formed on the first multilayer reflector, a first electrode formed in a region outside the central region including the center of the first semiconductor layer on the upper surface when viewed from a direction perpendicular to the upper surface of the first semiconductor layer, having an inner surface which is the side closer to the central region and an outer surface which is the side farther from the central region, a light-emitting layer formed in the central region of the first semiconductor layer, a second semiconductor layer of a second conductivity type formed on the light-emitting layer, and a second semi- The device comprises a second electrode formed on a conductive layer, a second multilayer reflector formed on the second electrode, a first electrode pad formed on the first electrode, and a second electrode pad formed on the second electrode, wherein the first electrode contains a first metal, and the first electrode pad contains a second metal which is different from the first metal, and has an extended portion that extends to the outer surface of the first electrode, and at least a portion of the interior of the first electrode is a high-resistance region in which the electrical resistance is relatively higher than the surrounding region inside the first electrode. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of the light-emitting device according to Example 1. [Figure 2] This is a top view of the light-emitting device according to Example 1. [Figure 3] This is a cross-sectional view of the light-emitting device according to Example 1. [Figure 4] This graph shows the change in the rate of change of voltage over time in the light-emitting device according to Example 1. [Figure 5] This diagram shows the flow chart of the manufacturing process for the light-emitting device according to Example 1. [Figure 6] This is a cross-sectional view of a light-emitting device according to a modified example of Example 1. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the drawings, identical components are denoted by the same reference numerals, and descriptions of redundant components are omitted. [Examples]

[0009] The configuration of the light-emitting device 100 according to Embodiment 1 will be explained using Figures 1 to 3. Figure 1 is a perspective view of the light-emitting device 100. Figure 2 is a top view of the light-emitting device 100. Figure 3 is a cross-sectional view of the light-emitting device 100 shown in Figure 2, along line 3-3. In Figure 3, the vertical direction represents the height of the light-emitting device 100.

[0010] The light-emitting device 100 consists of a vertical-cavity type surface-emitting laser EL (hereinafter referred to as the surface-emitting laser EL), which is a vertical-cavity type light-emitting element, and a submount substrate 31 joined to the surface-emitting laser EL. In Figures 1 and 2, the submount substrate 31 is shown by a dashed line, and the element mounting pads formed on the submount substrate 31 and the joining members that join the submount substrate 31 to the surface-emitting laser EL are omitted.

[0011] [Surface-emitting laser EL] First, let's explain the configuration of the surface-emitting laser (EL). The transparent substrate 11 is a flat substrate with a rectangular top surface. The transparent substrate 11 is also a growth substrate on which semiconductor crystals can be grown.

[0012] The transparent substrate 11 is made of a material that is transparent to blue wavelength light, such as undoped gallium nitride (GaN). In the light-emitting device 100 of this embodiment, the dimensions of the transparent substrate 11 are 1 mm square and the thickness is 200 μm.

[0013] In the following description, the central axis CA is defined as the axis passing through the center of the upper surface of the transparent substrate 11 and perpendicular to that upper surface. Furthermore, the direction away from the central axis CA in the radial direction is defined as the outward direction, and the opposite direction is defined as the inward direction.

[0014] The first multilayer film reflector 13 is a multilayer film reflector composed of semiconductor layers formed across the upper surface of the transparent substrate 11. The first multilayer film reflector 13 is a so-called distributed Bragg reflector (DBR) in which a high refractive index semiconductor film with a relatively high refractive index and a low refractive index semiconductor film with a lower refractive index than the high refractive index semiconductor film are alternately laminated on the upper surface of the transparent substrate 11.

[0015] The first multilayer film reflector 13 is formed, for example, by laminating 42 pairs of a high refractive index semiconductor film made of GaN and a low refractive index semiconductor film made of aluminum indium nitride (AlInN) on the upper surface of the transparent substrate 11. A buffer layer (not shown) made of GaN is provided between the transparent substrate 11 and the first multilayer film reflector 13.

[0016] The semiconductor structure layer EM is a laminated structure composed of a plurality of semiconductor layers formed on the first multilayer film reflector 13. The semiconductor structure layer EM is composed of an n-type semiconductor layer 15, a light emitting layer 16, and a p-type semiconductor layer 17.

[0017] The n-type semiconductor layer 15 as the first semiconductor layer having the first conductivity type is a semiconductor layer formed across the upper surface of the first multilayer film reflector 13. The n-type semiconductor layer 15 has a so-called mesa shape structure composed of a flat lower part 15A and a columnar convex part 15B protruding upward along the central axis CA from the center of the lower part 15A. The n-type semiconductor layer 15 is made of, for example, GaN and is doped with silicon (Si) as an n-type impurity.

[0018] The light emitting layer 16 is a semiconductor layer having a multiple quantum well layer (MQW) which is a plurality of quantum well structures in which a well layer made of InGaN and a barrier layer made of GaN are laminated on each other across the convex part 15B of the n-type semiconductor layer 15. The light emitting layer 16 is formed such that its light emitting center is on the central axis CA. The light emitting layer 16 emits blue light having a peak wavelength of, for example, 450 nm.

[0019] The p-type semiconductor layer 17 as the second semiconductor layer having the second conductivity type is a semiconductor layer formed across the upper surface of the light-emitting layer 16. The p-type semiconductor layer 17 has a protruding portion 17P having a circular upper surface shape and protruding upward. The p-type semiconductor layer 17 is made of, for example, AlGaN and is doped with magnesium (Mg) as a p-type impurity.

[0020] Note that, between the light-emitting layer 16 and the p-type semiconductor layer 17, an electron blocking layer for preventing electrons injected from the n-type semiconductor layer 15 into the light-emitting layer 16 from overflowing to the p-type semiconductor layer 17 side or a diffusion preventing layer for preventing diffusion of p-type impurities from the p-type semiconductor layer 17 into the light-emitting layer 16 may be formed.

[0021] The insulating layer 19 is formed in an annular shape on the upper surface of the p-type semiconductor layer 17 excluding the upper surface of the protruding portion 17P, and is a coating layer having electrical insulation and the same thickness as the protruding portion 17P. In other words, the insulating layer 19 is formed so as to expose a central region through which the central axis CA of the upper surface of the p-type semiconductor layer 17 passes. The insulating layer 19 is made of, for example, silicon dioxide (SiO2).

[0022] The p electrode 21 is a light-transmissive conductive film formed to cover the protruding portion 17P of the p-type semiconductor layer 17 and the insulating layer 19. That is, the p electrode 21 is electrically connected to the protruding portion 17P and is insulated from the p-type semiconductor layer 17 around the protruding portion 17P.

[0023] The p electrode 21 is made of, for example, a metal oxide having light transmittance with respect to blue light emitted from the light-emitting layer 16 of the semiconductor structure layer EM described above, such as indium tin oxide (ITO) or indium zinc oxide (IZO).

[0024] The second multilayer film mirror 22 is a multilayer film mirror made of a dielectric layer having a circular upper surface shape formed on the p electrode 21. The second multilayer film mirror 22 is formed so as to cover the upper surface of the protruding portion 17P, that is, the region through which the central axis CA passes, in a top view of the surface-emitting laser EL seen from above.

[0025] The second multilayer reflector 22 is a so-called distributed Bragg reflector (DBR) in which a high refractive index dielectric film with a relatively high refractive index and a low refractive index dielectric film with a lower refractive index than the high refractive index dielectric film are alternately stacked on the upper surface of the p electrode 21.

[0026] The second multilayer reflecting mirror 22 is formed, for example, by stacking 10.5 pairs of high-refractive-index dielectric films made of niobium pentoxide (Nb2O5) and low-refractive-index dielectric films made of SiO2 on the upper surface of the p electrode 21.

[0027] Furthermore, a transparent dielectric layer (not shown) with a circular top surface shape may be formed between the p electrode 21 and the second multilayer reflecting mirror 22, for example, as a phase adjustment layer. This dielectric layer may consist of, for example, Nb2O5, tantalum pentoxide (Ta2O5), zinc oxide (ZrO2), titanium oxide (TiO2), hafnium oxide (HfO2), etc.

[0028] The n-electrode 24 is a metal electrode with an annular upper surface shape formed on the upper surface of the lower part 15A of the n-type semiconductor layer 15 and electrically connected to the n-type semiconductor layer 15. In other words, the n-electrode 24 is formed so as to surround the p-electrode 21 when viewed from above with the surface-emitting laser EL.

[0029] The n electrode 24 is constructed by layering titanium (Ti), aluminum (Al), Ti, platinum (Pt), and gold (Au) in this order on the upper surface of the lower part 15A using a film deposition method such as sputtering or vapor deposition. In the light-emitting device 100 of this embodiment, the film thicknesses of Ti, Al, Ti, Pt, and Au are 10 Å, 0.2 μm, 0.1 μm, 0.1 μm, and 1.5 μm, respectively.

[0030] The n-electrode 24 includes a compound formation region GA where an intermetallic compound is formed. The compound formation region GA extends from the interface between the n-electrode 24 and the lower part 15A of the n-type semiconductor layer 15 to about half the thickness of the n-electrode 24.

[0031] The compound formation region GA is formed continuously along the outer edge of the n electrode 24 when viewed from above with the surface-emitting laser EL. In other words, the compound formation region GA has an annular top surface shape that follows the shape of the n electrode 24.

[0032] The intermetallic compound formed in the compound formation region GA is AuAl or AuAl2. Since such intermetallic compounds have higher electrical resistance than the metals Al and Au, the compound formation region GA inside the n electrode 24 is a high-resistance region with higher electrical resistance than other regions inside the n electrode 24. Alternatively, the compound formation region GA may be an electrically high-resistance region provided with an insulating film, for example, SiO2, instead of an intermetallic compound.

[0033] The n-electrode pad 25 is an electrode pad with an annular upper surface shape formed on the upper surface of the n-electrode 24. The n-electrode pad 25 extends outward from the upper surface of the n-electrode 24 to the outer surface 24S on the side farther from the p-electrode 21, including the central region of the n-electrode 24, and is in contact with the lower part 15A of the n-type semiconductor layer 15. In other words, the n-electrode pad 25 has an extended portion that extends from the upper surface of the p-electrode 21 to the outer surface 24S.

[0034] In other words, the n-electrode pad 25 is formed to hang down from the upper surface of the n-electrode 24 to the outer surface 24S. Here, the n-electrode pad 25 is formed on the upper surface and outer surface 24S of the n-electrode 24, but not on the inner surface of the n-electrode 24, that is, the surface facing the p-type semiconductor layer 17 of the n-electrode 24.

[0035] Furthermore, the n-electrode pad 25 is formed such that, in a top view of the surface-emitting laser EL, its inner edge is located outside the inner edge of the n-electrode 24. In other words, the n-electrode pad 25 covers the top surface of the n-electrode 24 so as to expose the region along the inner edge of the top surface of the n-electrode 24.

[0036] The n-electrode pad 25 is constructed by laminating Ti, Pt, and Au in that order on the upper and outer surfaces 24S of the n-electrode 24 using a film deposition method such as sputtering or vapor deposition. In the light-emitting device 100 of this embodiment, the film thicknesses of Ti, Pt, and Au are 0.1 μm, 0.1 μm, and 1.1 μm, respectively. In addition, in the light-emitting device 100 of this embodiment, the width T (see Figure 3) of the portion of the n-electrode pad 25 formed on the outer surface 24S of the n-electrode 24 is 5 μm.

[0037] The intermetallic compound formed in the compound formation region GA of the n electrode 24 described above is mainly formed by the Al of the n electrode 24 and the Au of the n electrode pad 25 via the interface between the Al layer of the n electrode 24 and the n electrode pad 25 that is in contact with the Al layer.

[0038] Specifically, when the n-electrode pad 25 is joined via the joining member 36 described later, the Au of the n-electrode pad 25 and the Al of the outer surface 24S of the n-electrode 24 diffuse to form an intermetallic compound consisting of Au and Al. Therefore, the compound formation region GA is formed mainly extending inward from the outer surface 24S of the n-electrode 24 when viewed from the central axis CA.

[0039] The p-electrode pad 28 is a metal electrode with a circular top surface shape formed by covering the second multilayer reflecting mirror 22 on the p-electrode 21. The p-electrode pad 28 is electrically connected to the p-type semiconductor layer 17 via the p-electrode 21. The p-electrode pad 28 is formed so that its top surface is at the same height as the top surface of the n-electrode pad 25. The p-electrode pad 28 is formed by stacking Ti, Pt, and Au in that order on the top surface of the p-electrode 21.

[0040] [Submount board 31] Next, the submount substrate 31 will be described. The submount substrate 31 is a flat substrate having a rectangular top surface shape. The submount substrate 31 is made of an insulating material such as aluminum nitride (AlN) or aluminum oxide (Al2O3). In particular, it is preferable to use AlN as the submount substrate 31 from the viewpoint of heat dissipation. In the light-emitting device 100 of this embodiment, the thickness of the submount substrate 31 is 200 μm.

[0041] The submount substrate 31 has a first element mounting pad 33 and a second element mounting pad 34 formed on the lower surface of the submount substrate 31 at a distance from each other. Hereinafter, unless otherwise specified, the first element mounting pad 33 and the second element mounting pad 34 will be referred to as element mounting pads 33 and 34.

[0042] The first element mounting pad 33 is a metal layer with a circular top surface shape formed in the center of the lower surface of the submount substrate 31. The second element mounting pad 34 is a metal layer with an annular top surface shape formed to surround the first element mounting pad 33 when viewed from above on the submount substrate 31.

[0043] The element mounting pads 33 and 34 are formed on the lower surface of the submount substrate 31 by stacking Ti, Pt, Au, and Ti in that order, for example, by a film deposition method such as sputtering or vapor deposition. In the light-emitting device 100 of this embodiment, the film thicknesses of Ti, Pt, Au, and Ti are 0.1 μm, 0.1 μm, 1.3 μm, and 50 Å, respectively.

[0044] The light-emitting device 100 is constructed by joining a surface-emitting laser EL and a submount substrate 31 via a bonding member 36 made of a gold-tin (Au-Sn) eutectic bond. Specifically, the n electrode pad 25 of the surface-emitting laser EL and the second element mounting pad 34 of the submount substrate 31 are joined via the bonding member 36, and the p electrode pad 28 of the surface-emitting laser EL and the first element mounting pad 33 of the submount substrate 31 are joined via the bonding member 36.

[0045] In other words, in the light-emitting device 100 of this embodiment, the surface-emitting laser EL is flip-chip mounted on the submount substrate 31. In the light-emitting device 100, the surface-emitting laser EL is driven by receiving power from an external source via the element mounting pads 33 and 34 on the submount substrate 31.

[0046] Here, the operation of the surface-emitting laser EL will be explained. In the surface-emitting laser EL, the first multilayer reflector 13 and the second multilayer reflector 22 face each other with the p electrode 21 and the semiconductor structural layer EM in between. As a result, the surface-emitting laser EL forms a resonator OC between the first multilayer reflector 13 and the second multilayer reflector 22, with the direction perpendicular to the semiconductor structural layer EM (up and down direction in Figure 3) as the resonator length direction.

[0047] When a voltage is applied to the p electrode 21 and n electrode 24 of the surface-emitting laser EL, and a current flows between the p electrode 21 and the n electrode 24, a current flows in the light-emitting layer 16 of the semiconductor structure layer EM. When this reaches a threshold current, which is a predetermined current value, the intensity of the blue light emitted from the light-emitting layer 16 increases rapidly.

[0048] The blue light emitted from the light-emitting layer 16 upon reaching the threshold current is repeatedly reflected between the first multilayer mirror 13 and the second multilayer mirror 22, that is, within the resonator OC, until it reaches a resonant state (i.e., laser oscillation occurs).

[0049] As described above, an insulating layer 19 is formed in the region of the upper surface of the p-type semiconductor layer 17, excluding the protruding portion 17P. Therefore, on the upper surface of the p-type semiconductor layer 17, only the upper surface of the protruding portion 17P is electrically connected to the p-electrode 21. Thus, in the p-type semiconductor layer 17, most of the current flowing from the p-electrode 21 to the p-electrode 21 is supplied to the semiconductor structural layer EM via the upper surface of the protruding portion 17P, which is a low-resistance region, and flows to the n-electrode 24.

[0050] Therefore, in a surface-emitting laser (EL), current is supplied to the light-emitting layer 16 via the upper surface of the protrusion 17P, and blue light is emitted from this upper surface along the central axis CA. In other words, in a surface-emitting laser (EL), the protrusion 17P and the insulating layer 19 of the p-type semiconductor layer 17 function as current constriction portions that limit the range of current supply to the semiconductor structural layer EM.

[0051] In the surface-emitting laser (EL), the reflectivity of the first multilayer mirror 13 for blue light is slightly lower than that of the second multilayer mirror 22 for blue light. Therefore, a portion of the blue light resonating in the resonator OC is transmitted through the first multilayer mirror 13 and the transparent substrate 11 and extracted to the outside. That is, the light resonating between the first multilayer mirror 13 and the second multilayer mirror 22 is emitted downwards in Figure 3.

[0052] Furthermore, an anti-reflective coating (not shown) is formed on the lower surface of the transparent substrate 11, which consists of Nb2O5 and SiO2 layers. This anti-reflective coating is a so-called AR coating that suppresses the reflection of blue light emitted from the transparent substrate 11 upwards in Figure 3.

[0053] [Stabilization of the voltage applied between electrodes of a surface-emitting laser (EL)] The stabilization of the voltage applied between the p electrode 21 and the n electrode 24 of the surface-emitting laser EL in the light-emitting device 100 of this embodiment will be explained below with reference to Figure 3.

[0054] In the light-emitting device 100, a voltage is applied to the n electrode pad 25 and p electrode pad 28 via the element mounting pads 33 and 34 of the submount substrate 31. The current flowing between the n electrode pad 25 and the p electrode pad 28 then proceeds from the p electrode pad 28 through the p electrode 21, through the p-type semiconductor layer 17, and to the light-emitting layer 16. Subsequently, the current flows through the n-type semiconductor layer 15, through the n electrode 24, and then to the n electrode pad 25.

[0055] In the light-emitting device 100 of this embodiment, as described above, the n electrode 24 includes a compound formation region GA in which an intermetallic compound is formed inside it. Furthermore, as described above, the intermetallic compound formed in the compound formation region GA is a compound composed of Al and Au, and since it has a higher electrical resistance than the metals Al and Au, the compound formation region GA inside the n electrode 24 is a high-resistance region with higher electrical resistance than other regions inside the n electrode 24.

[0056] Now, let's consider the case where a compound formation region GA is not formed inside the n electrode 24. If a compound formation region GA is not formed inside the n electrode 24, that is, if a high-resistance region is not formed in the n electrode 24, then the entire interior of the n electrode 24 will have the same electrical resistance.

[0057] Therefore, the current flowing from the n-electrode pad 25 to the semiconductor structural layer EM is dispersed along the shortest path from the n-electrode pad 25 to the interface between the n-electrode 24 and the lower part 15A of the n-type semiconductor layer 15, and flows into the n-type semiconductor layer 15. In other words, there is a certain amount of current that flows into the n-type semiconductor layer 15 from a position far from the central axis CA of the interface, and due to the electrical resistance within the n-type semiconductor layer 15, the distance it travels from the n-electrode pad 25 to the light-emitting layer 16 is longer.

[0058] In contrast, in the light-emitting device 100 of this embodiment, the compound-forming region GA, which is a high-resistance region, is formed as far away from the central axis CA as possible when viewed from above. In other words, the region of the n-electrode 24 that is relatively close to the central axis CA is a low-resistance region.

[0059] As a result, when current flows from the n electrode pad 25 to the semiconductor structural layer EM, the current path, as shown by the dashed line in Figure 3, preferentially flows through other parts with lower resistance, namely the inner parts closer to the light-emitting layer 16, rather than the compound formation region GA, which has higher resistance.

[0060] Therefore, the current flowing from the n-electrode pad 25 to the semiconductor structure layer EM passes through a path closer to the central axis CA within the n-electrode 24, rather than towards the compound formation region GA. This results in a larger proportion of the current component taking a shorter path from the n-electrode pad 25 to the light-emitting layer 16. In other words, the current path passing through the n-type semiconductor layer 15, which has higher electrical resistance than the n-electrode 24, can be restricted, and the amount of current flowing through the semiconductor structure layer EM per unit time can be increased. From this point of view, it is preferable that the compound formation region GA is formed in contact with the n-type semiconductor layer 15.

[0061] In the light-emitting device 100 of this embodiment, by shortening the current path within the semiconductor structural layer EM and reducing the electrical resistance caused by the path length within the semiconductor structural layer EM, it is possible to suppress an increase in the voltage applied between the p electrode 21 and the n electrode 24.

[0062] Therefore, according to the light-emitting device 100 of this embodiment, by including a compound formation region GA in the n electrode 24 in which an intermetallic compound is formed, the voltage applied between the p electrode 21 and the n electrode 24 can be stabilized.

[0063] Furthermore, in the light-emitting device 100 of this embodiment, the compound formation region GA formed within the n electrode 24 can also serve as a heat dissipation section that releases heat generated in the semiconductor structural layer EM to the outside. Therefore, compared to, for example, the case in which an insulating layer made of resin is formed as a high-resistance region in the compound formation region GA, a greater amount of heat generated in the semiconductor structural layer EM can be released.

[0064] Furthermore, if the proportion of compound formation region GA, which is a high-resistance region, becomes too large inside the n electrode 24, it becomes difficult for current to flow from the n electrode pad 25 to the semiconductor structural layer EM. Therefore, from the viewpoint of controlling the current flow to be directed toward the central axis CA, it is preferable that the radial width of the compound formation region GA is shorter than half the radial width of the n electrode 24.

[0065] In this embodiment, the light-emitting device 100 has an annular top surface shape for the n electrode 24, but it is not limited to this and may have an elliptical or rectangular top surface shape. Furthermore, the compound formation region GA does not necessarily have to follow the shape of the n electrode 24; it is sufficient that the compound formation region GA is formed in at least a part of the interior of the n electrode 24. For example, the compound formation region GA may be formed intermittently inside the n electrode 24 when viewed from above.

[0066] [verification] The verification and results of the light-emitting device 100 of this embodiment will be described below with reference to Figure 4. Figure 4 is a graph showing the rate of change of voltage in the light-emitting device 100 of this embodiment and the light-emitting device of the comparative example. In the graph of Figure 4, the vertical axis represents the rate of change of voltage and the horizontal axis represents time.

[0067] In this verification, the comparative light-emitting device differs from the light-emitting device 100 of this embodiment in that an n-electrode pad 25 is not formed on the outer surface 24S of the n-electrode 24, and a compound formation region GA is not formed inside the n-electrode 24, but it has the same configuration as the light-emitting device 100 of this embodiment in all other respects.

[0068] In this verification, during continuous constant current operation at a current value that results in an initial output of 1 mW, the voltage applied between the p electrode 21 and n electrode 24 of both the light-emitting device 100 and the comparative example light-emitting device was measured, and the rate of change of the voltage was calculated with the voltage at the start of measurement set to 1. The voltage measurement time was from 158h to 1000h. In the graph in Figure 4, the rate of change of the voltage of the light-emitting device 100 in this embodiment is shown by a solid line, and the rate of change of the voltage of the comparative example light-emitting device is shown by a dashed line.

[0069] As shown in the graph in Figure 4, the rate of change of voltage in the light-emitting device 100 of this embodiment remained almost unchanged even after 1000 hours of operation, with a maximum change of less than 2%. On the other hand, the rate of change of voltage in the light-emitting device of the comparative example changed significantly over time, with the voltage changing by up to approximately 10% after 1000 hours of operation.

[0070] Therefore, based on the results of this verification, the light-emitting device 100 of this embodiment can stabilize the voltage applied between the p electrode 21 and the n electrode 24 of the surface-emitting laser EL compared to a light-emitting device in which a compound formation region GA is not formed inside the n electrode 24, and can provide a light-emitting device 100 with a long lifespan.

[0071] [Manufacturing method for light-emitting device 100] The manufacturing method of the light-emitting device 100 will be described below with reference to Figure 5. Figure 5 is a diagram showing an example of the manufacturing flow of the light-emitting device 100. In Figure 5, steps D1 to D4 are preparation steps for the surface-emitting laser EL, and steps S1 and S2 are preparation steps for the submount substrate 31. Step B1 is the mounting step of the surface-emitting laser EL onto the submount substrate 31.

[0072] The following section will focus on the process of forming the compound formation region GA inside the n-electrode 24 described above. Specifically, the n-electrode formation process D2, the electrode pad formation process D3, and the surface-emitting laser bonding process B1 shown in Figure 5 will be explained.

[0073] First, the n-electrode formation process D2 and the electrode pad formation process D3 will be explained. As described above, the n-electrode 24, n-electrode pad 25, and p-electrode pad 28 are formed using film formation methods such as sputtering and vapor deposition.

[0074] When the n-electrode 24 is formed using the above film deposition method, the end faces of each metal layer constituting the n-electrode 24 are exposed on the outer surface 24S of the n-electrode 24. Specifically, the end faces of Ti, Al, Ti, Pt, and Au are exposed.

[0075] Furthermore, when the n-electrode pad 25 is formed using the above-described film formation method, as described above, the n-electrode pad 25 is formed to cover the outer surface 24S of the n-electrode 24, so that the n-electrode pad 25 comes into contact with each metal layer exposed on the outer surface 24S of the n-electrode 24.

[0076] Therefore, in the surface-emitting laser EL manufactured through the n-electrode formation process D2 and the electrode pad formation process D3, the compound formation region GA has not yet been formed inside the n-electrode 24. In other words, at the stage when the surface-emitting laser EL is manufactured, the reaction between Al and Au has not yet occurred inside the n-electrode 24.

[0077] Next, the bonding process B1 of the surface-emitting laser to the submount substrate 31 will be described. As described above, the surface-emitting laser EL is bonded to the submount substrate 31 in a flip-chip mounting manner. Specifically, the n electrode pad 25 of the surface-emitting laser EL and the second element mounting pad 34 of the submount substrate 31 are bonded via a bonding member 36, and the p electrode pad 28 of the surface-emitting laser EL and the first element mounting pad 33 of the submount substrate 31 are bonded via a bonding member 36.

[0078] When mounting the surface-emitting laser EL onto the submount substrate 31, the n electrode pads 25 and p electrode pads 28 are joined to the element mounting pads 33 and 34 by applying a predetermined pressure to the surface-emitting laser EL and melting and curing the bonding member 36 before melting at a temperature of 280 to 450°C.

[0079] At this time, the pressure applied to the surface-emitting laser EL causes strain to occur in the n electrode 24 and the n electrode pad 25, which can result in the Au from the n electrode pad 25 mixing into the Al layer of the n electrode 24 that is in contact with the n electrode pad 25 on the outer surface 24S of the n electrode 24. In other words, the bonding of the surface-emitting laser EL can cause a state in which part of the layer structure of the n electrode 24 and the n electrode pad 25 is disrupted.

[0080] In this state, for example, the heat related to the melting of the joining member 36 is applied to the n electrode 24, and a compound formation region GA is created inside the n electrode 24 by the diffusion of the Au component contained in the n electrode pad 25 and Al from the outer surface 24S direction, forming an intermetallic compound consisting of Al and Au. In this way, a light-emitting device 100 in which a compound formation region GA is formed inside the n electrode 24 is manufactured.

[0081] Furthermore, in order to generate the compound formation region GA, in addition to the above process, a heat treatment may be performed to apply heat to the n electrode 24 after the manufacturing of the light-emitting device 100. In this heat treatment, if the temperature applied to the surface-emitting laser EL becomes too high, it will affect the oscillation state of the light, so it is preferable to control the temperature so that the n electrode 24 is heated to a temperature of 50°C or more and 200°C or less. Heat treatment at temperatures of 300°C or higher is undesirable because the p-type impurities contained in the p-type semiconductor layer 17 will diffuse within the semiconductor layer, causing changes in the oscillation state and narrowing of the oscillation region, which degrades the device characteristics.

[0082] [Differentiation] Below, a modified light-emitting device 110 of Example 1 will be described with reference to Figure 6. This modified light-emitting device 110 differs from Example 1 in that the outer surface 24S of the n electrode 24, the outer surface of the n electrode pad 25, and the compound formation region GA are inclined, but otherwise has the same configuration as the light-emitting device 100.

[0083] In this modified light-emitting device 110, the outer surface 24S of the n electrode 24 is inclined inward with respect to the central axis CA of the surface-emitting laser EL. That is, the diameter of the n electrode 24 gradually decreases as it moves upward along the central axis CA in the figure. Also, in this modified light-emitting device 110, the outer surface of the n electrode pad 25 is inclined to follow the shape of the outer surface 24S of the n electrode 24, as shown in Figure 6.

[0084] In the light-emitting device 110 of this modified example, the compound-forming region GA is formed to follow the shape of the outer surface 24S of the n electrode 24. That is, the diameter of the compound-forming region GA gradually decreases as it moves upward along the central axis CA.

[0085] Because the outer surface 24S of the n electrode 24 is inclined, the surface area of ​​metal exposed per unit area of ​​the n electrode 24 in the light-emitting device 110 of this modified example is larger than that of the n electrode 24 having a rectangular cross-sectional shape in the light-emitting device 100 of Example 1.

[0086] As a result, in the light-emitting device 110 of this modified example, intermetallic compounds are more easily formed in the compound formation region GA compared to the light-emitting device 100 of Example 1. In addition, the height of the compound formation region GA is higher compared to the light-emitting device 100 of Example 1, that is, the thickness from the lower part 15A is slightly larger.

[0087] Therefore, according to the light-emitting device 110 of this modified example, excessive diffusion of the compound-forming region GA in the direction of the central axis CA can be suppressed, thereby stabilizing the voltage within the device and improving reliability. Furthermore, because the compound-forming region GA is an intermetallic compound, it has higher hardness than metal, which can increase the bonding strength when mounted on the submount substrate 31.

[0088] In this modified light-emitting device 110, the inclination angle of the outer surface 24S of the n electrode 24 with respect to the central axis CA may be different from the inclination angle of the outer surface 25 of the n electrode pad 25. For example, the n electrode 24 may be formed such that the inclination angle of the outer surface 24S of the n electrode 24 is greater than the inclination angle of the outer surface 25 of the n electrode pad 25.

[0089] This increases the surface area of ​​the bonding surface between the n-electrode pad 25 and the bonding member 36, which is the upper surface of the n-electrode pad 25. As a result, the current path passing through the n-electrode pad 25 becomes larger, reducing electrical resistance and stabilizing the bonding surface and voltage with the bonding member 36. Furthermore, it increases the bonding strength when mounted on the submount substrate 31.

[0090] Furthermore, when the light-emitting device 100 or light-emitting device 110 is in operation, heat of approximately 60°C may be generated in and around the semiconductor structural layer EM. Consequently, heat of approximately 60°C will also be applied to the n electrode 24. As a result, for example, when the light-emitting device 100 or light-emitting device 110 is driven continuously for a certain period of time, even if the compound formation region GA was not formed at the time of device junction, the compound formation region GA may spontaneously form inside the n electrode 24.

[0091] Therefore, with the light-emitting device 100 and the light-emitting device 110, the heat generated during operation after the device is manufactured can form a compound formation region GA inside the n electrode 24, and the formation of the compound formation region GA inside the n electrode 24 stabilizes the voltage applied between the p electrode 21 and the n electrode 24 of the surface-emitting laser EL, as described above. [Explanation of Symbols]

[0092] 100, 110 Light-emitting devices 11 Transparent substrate 13. First multilayer reflecting mirror 15 n-type semiconductor layer 16. Emitting layer 17 p-type semiconductor layer 19. Insulating layer 21p electrode 22. Second multilayer reflecting mirror 24 n electrode 25 N electrode pads 28 p electrode pads 31 Submount board 33 First element mounted pad 34 Second element-mounted pad 36 Joining members EL (Electroluminescent) Surface-emitting laser (Vertical-cavity light-emitting element) GA compound production area

Claims

1. A light-transmitting substrate, A first multilayer reflecting mirror formed on the substrate, A first semiconductor layer of a first conductivity type formed on the first multilayer reflecting mirror, A first electrode is formed in a region outside the central region including the center of the first semiconductor layer on the upper surface of the first semiconductor layer, as viewed from a direction perpendicular to the upper surface of the first semiconductor layer, and has an inner surface which is the side surface close to the central region and an outer surface which is the side surface farther from the central region, A light-emitting layer formed in the central region of the first semiconductor layer, A second semiconductor layer of a second conductivity type formed on the light-emitting layer, A second electrode formed on the second semiconductor layer, A second multilayer reflecting mirror formed on the second electrode, A first electrode pad formed on the first electrode, A second electrode pad formed on the second electrode, Equipped with, The first electrode comprises a first metal, The first electrode pad includes a second metal which is different from the first metal, and has an extended portion that extends to the outer surface of the first electrode. A vertical resonator type light-emitting element, characterized in that at least a portion of the interior of the first electrode is a high-resistance region in which the electrical resistance is relatively higher than that of the surrounding region inside the first electrode.

2. The vertical resonator type light-emitting element according to claim 1, characterized in that an intermetallic compound consisting of the first metal and the second metal is formed in the high-resistance region.

3. The vertical resonator type light-emitting element according to claim 1, characterized in that the high-resistance region is formed along the outer edge of the first electrode when viewed from above the vertical resonator type light-emitting element.

4. The first electrode has an annular top surface shape when viewed from above the vertical resonator type light-emitting element. The vertical resonator type light-emitting element according to claim 2, characterized in that the high-resistance region is formed continuously along the upper surface shape of the first electrode while in contact with the first semiconductor layer.

5. The vertical resonator type light-emitting element according to claim 1, characterized in that the first metal is Al and the second metal is Au.

6. The vertical resonator type light-emitting element according to claim 1, characterized in that the inner edge of the first electrode is located inward from the inner edge of the first electrode pad when viewed from above the vertical resonator type light-emitting element.

7. The vertical resonator type light-emitting element according to claim 1, characterized in that the second electrode is ITO or IZO.

8. A light-emitting device comprising a vertical resonator type light-emitting element according to any one of claims 1 to 7, A submount substrate having an element mounting pad made of metal on one of its main surfaces, A light-emitting device characterized in that each of the first electrode pad and the second electrode pad is bonded to the element mounting pad of the submount substrate by a bonding member.

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