Semiconductor light-emitting element

Abstract

[Problem] To provide a semiconductor light-emitting element in which damage by heat can be suppressed. [Solution] A semiconductor light-emitting element according to one embodiment of the present disclosure comprises: a first nitride semiconductor layer of a first conductivity type; an active layer which is provided on the first semiconductor layer; a second nitride semiconductor layer which is of a second conductivity type and which is provided on the active layer; a tunnel junction layer which is provided on the second semiconductor layer; a third nitride semiconductor layer which is of a first conductivity type and which is provided on the tunnel junction layer; and a trench which extends in a first direction from the third nitride semiconductor layer to the first nitride semiconductor layer. The second nitride semiconductor layer has a recess which extends in a second direction that intersects the first direction. One end of the recess is open and is in communication with the trench, and the other end of the recess terminates in the second nitride semiconductor layer.

Description

Semiconductor light emitting device

[0001] The present disclosure relates to semiconductor light emitting devices.

[0002] In semiconductor light-emitting devices containing nitrides, hydrogen is typically desorbed by heat treatment to activate and reduce the resistance of the p-type semiconductor. Furthermore, in tunnel junction structures with a stacked structure of n / p / n-type semiconductors, the presence of an upper n-type semiconductor layer makes it difficult for hydrogen to escape from the p-layer. Therefore, a technique for forming a trench in a semiconductor layer containing a p-type semiconductor is known for such semiconductor light-emitting devices. This technique allows hydrogen to be desorbed from the side of the trench.

[0003] Japanese Patent Application Laid-Open No. 2017-204579

[0004] If the exposed area of ​​the side surface of the p-type semiconductor is small when a trench is simply formed in the semiconductor layer as in the above technique, a high temperature and long time heat treatment is required to desorb hydrogen, making the semiconductor light emitting device susceptible to heat damage.

[0005] The present disclosure provides a semiconductor light emitting device capable of suppressing thermal damage.

[0006] A semiconductor light-emitting device according to an embodiment of the present disclosure includes a first nitride semiconductor layer of a first conductivity type, an active layer provided on the first semiconductor layer, a second nitride semiconductor layer of a second conductivity type provided on the active layer, a tunnel junction layer provided on the second semiconductor layer, a third nitride semiconductor layer of the first conductivity type provided on the tunnel junction layer, and a trench extending in a first direction from the third nitride semiconductor layer to the first nitride semiconductor layer. The second nitride semiconductor layer has a recess extending in a second direction intersecting the first direction, one end of the recess opening and communicating with the trench, and the other end of the recess terminating within the second nitride semiconductor layer.

[0007] The semiconductor light-emitting element may be a light-emitting diode (LED), a laser diode (LD), or a vertical cavity surface emitting laser (VCSEL).

[0008] The recess may be provided at the interface between the active layer and the second nitride semiconductor layer.

[0009] The depression may have a height of 10 nm or more in the first direction and a depth of 10 nm or more in the second direction.

[0010] The other end of the recess may have an inclined surface that is inclined with respect to the second direction.

[0011] The depth of the depression may be greater than the maximum height difference in the second direction, which indicates the surface roughness of the side surface of the trench.

[0012] The second nitride semiconductor layer may have a plurality of depressions.

[0013] At least one of the height in the first direction and the depth in the second direction may be different among the plurality of recesses.

[0014] The semiconductor light emitting device may further include a dielectric film that covers the side surfaces of the trench and fills the recess.

[0015] The semiconductor light emitting device may further include a hydrogen absorbing metal film containing at least palladium (Pd) or nickel (Ni) on a side surface of the dielectric film covering the side surface of the trench.

[0016] The semiconductor light emitting device may further include a dielectric film that covers a side surface of the trench and closes one end of the depression.

[0017] The side surface of the trench and the surface of the recess may have either a crystalline plane or a non-crystalline plane.

[0018] The surface of the depression may have a crystal plane (0001) and a crystal plane (000-1), and the surface roughness of the crystal plane (000-1) may be greater than the surface roughness of the crystal plane (0001).

[0019] The surface of the recess may comprise the elements silicon (Si), carbon (C), fluorine (F), chlorine (Cl), or boron (B), or compounds of these elements.

[0020] The semiconductor light-emitting element may further include a first optical reflection layer and a second optical reflection layer facing each other with the active layer sandwiched in the first direction, and the tunnel junction layer may be provided only within the optical path of an optical resonator consisting of the first optical reflection layer and the second optical reflection layer.

[0021] the tunnel junction layer is composed of a p-type GaN layer and an n-type GaN layer, and the p-type impurity concentration of the p-type GaN layer and the n-type impurity concentration of the n-type GaN layer are each 5×10 １９ cm ２ It may be more than that.

[0022] The tunnel junction layer may include a p-type GaN layer, an n-type GaN layer, and an InGaN layer provided between the p-type GaN layer and the GaN layer.

[0023] 1. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a first embodiment. 2. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a second embodiment. 3. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a third embodiment. 4. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a modification of the third embodiment. 5. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a fourth embodiment. 6. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a fifth embodiment. 7. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a sixth embodiment. 8. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a seventh embodiment. 9. A cross-sectional view showing the structure of a semiconductor light-emitting device according to an eighth embodiment. 10. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a ninth embodiment. 11. A cross-sectional view showing the structure of a semiconductor light-emitting device according to an eleventh embodiment. 12. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a thirteenth embodiment. 14. A cross-sectional view showing the structure of a semiconductor light-emitting device according to a fourteenth embodiment.

[0024] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0025] First Embodiment FIG. 1 is a cross-sectional view showing the structure of a semiconductor light-emitting device according to a first embodiment. In the following description, the stacking direction of each layer is referred to as the Z direction (first direction), one of two directions intersecting (orthogonal to) the Z direction is referred to as the X direction (second direction), and the other is referred to as the Y direction. The semiconductor light-emitting device described in each of the following embodiments can be applied to an LED (light-emitting diode) or an LD (laser diode). Furthermore, in a specific embodiment, the semiconductor light-emitting device according to the present disclosure can also be applied to a VCSEL (vertical cavity surface emitting laser).

[0026] 1 includes a substrate 100, a first nitride semiconductor layer 110, an active layer 120, a second nitride semiconductor layer 130, a tunnel junction layer 140, and a third nitride semiconductor layer 150. The substrate 100 is, for example, a GaN substrate, a silicon substrate, or a sapphire substrate. The first nitride semiconductor layer 110 is provided on the substrate 100.

[0027] The first nitride semiconductor layer 110 is, for example, an n-type (first conductivity type) GaN layer. An active layer 120 is provided on the first nitride semiconductor layer 110.

[0028] The active layer 120 emits and amplifies spontaneously emitted light due to carrier recombination. The active layer 120 is made of, for example, InGaN, AlGaN, InGaP, or AlGaInP. A second nitride semiconductor layer 130 is provided on the active layer 120.

[0029] 1, the second nitride semiconductor layer 130 is composed of, for example, a p-type AlGaN layer 131 and a p-type (second conductivity type) GaN layer 132. The second nitride semiconductor layer 130 contains, for example, magnesium (Mg) as a p-type impurity.

[0030] The AlGaN layer 131 is provided on the active layer 120. The GaN layer 132 is provided on the AlGaN layer 131. The thickness of the AlGaN layer 131 is thinner than the thickness of the GaN layer 132, and is, for example, 10 nm or more. In this case, the total thickness of the second nitride semiconductor layer 130 is, for example, 100 nm or less. A tunnel junction layer 140 is provided on the GaN layer 132.

[0031] The tunnel junction layer 140 is composed of, for example, a p-type GaN layer 141 and an n-type GaN layer 142. The GaN layer 141 is provided on the GaN layer 132. The GaN layer 142 is provided on the GaN layer 141. The p-type impurity concentration of the GaN layer 141 and the n-type impurity concentration of the GaN layer 142 are each 5×10 １９ cm ２ The lower limit of the impurity concentration is 5×10 １９ cm ２ This reduces the electrical resistance of the tunnel junction layer 140, making it possible to drive the semiconductor light emitting device 1 at a low voltage. On the GaN layer 142, a third nitride semiconductor layer 150 is provided.

[0032] The third nitride semiconductor layer 150 is, for example, an n-type GaN layer. The upper surface of the third nitride semiconductor layer 150 is the surface from which light generated in the active layer 120 is emitted.

[0033] The semiconductor light emitting device 1 configured as described above can be formed by sequentially depositing the first to third nitride semiconductor layers 110 to 150 on the substrate 100. When the second nitride semiconductor layer 130 is deposited by epitaxial growth using a carrier gas containing hydrogen, a heat treatment is performed to remove hydrogen from the second nitride semiconductor layer 130 in order to activate and reduce its resistance. However, because the conductivity type of the third nitride semiconductor layer 150 disposed on the first nitride semiconductor layer 110 is n-type, hydrogen cannot pass through the third nitride semiconductor layer 150. Therefore, the semiconductor light emitting device 1 according to this embodiment is provided with a trench 200.

[0034] For example, by performing anisotropic etching such as RIE (Reactive Ion Etching) on ​​the stacked structure from the first nitride semiconductor layer 110 to the third nitride semiconductor layer 150, a trench 200 extending in a first direction from the third nitride semiconductor layer 150 to the first nitride semiconductor layer 110 can be formed. Hydrogen is desorbed from the side surfaces of the trench 200 that expose the second nitride semiconductor layer 130. However, if the area of ​​the exposed surface of the second nitride semiconductor layer 130 is small, a high-temperature, long-time heat treatment may be required to desorb the hydrogen. In this case, the semiconductor light-emitting device 1 becomes susceptible to heat damage.

[0035] Therefore, the second nitride semiconductor layer 130 of the semiconductor light emitting device 1 according to this embodiment is further provided with a recess 210. As described above, the second nitride semiconductor layer 130 has a two-layer structure made up of the AlGaN layer 131 and the GaN layer 132. Therefore, for example, the recess 210 can be formed at the interface between the active layer 120 and the second nitride semiconductor layer 130 by selectively etching the AlGaN layer 131 relative to the GaN layer 132 using an etching solution containing tetramethylammonium hydroxide (TMAH).

[0036] 1 , the recess 210 extends in the X direction. One end of the recess 210 is open and communicates with the trench 200. Meanwhile, the other end of the recess 210 terminates within the AlGaN layer 131. The height of the recess 210 in the Z direction and the depth of the recess 210 in the X direction depend on the thickness of the AlGaN layer 131. When the thickness of the AlGaN layer 131 is, for example, 10 nm or more, the recess 210 has a height of 10 nm or more and a depth of 10 nm or more.

[0037] According to the above-described embodiment, after forming the trench 200, a portion of the second nitride semiconductor layer 130 is removed to form the recess 210. The recess 210 increases the unevenness of the side surface of the second nitride semiconductor layer 130, thereby increasing the surface area of ​​the exposed surface of the second nitride semiconductor layer 130. This makes it easier for hydrogen to desorb from the second nitride semiconductor layer 130, thereby avoiding high temperature and long time heat treatment. As a result, thermal damage can be suppressed, and therefore, deterioration in light emission efficiency and reliability can be alleviated. Furthermore, the process time can be shortened, and processing costs can be reduced.

[0038] Furthermore, the recesses 210 not only contribute to hydrogen desorption but also contribute to, for example, stability of the transverse mode, polarization control, improvement of cleavage guiding, reduction of element stress, and assistance in element isolation.

[0039] Furthermore, in this embodiment, anisotropic etching such as RIE is performed to expose amorphous surfaces when forming trench 200, and wet etching is performed to expose crystalline surfaces when forming recess 210. In this way, in semiconductor light-emitting element 1, multiple types of surfaces, such as amorphous surfaces and crystalline surfaces, are exposed, which makes it possible to eliminate differences in hydrogen desorption due to surface conditions and to effectively desorb hydrogen.

[0040] Second Embodiment Fig. 2 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a second embodiment. The following description will focus on the differences from the first embodiment.

[0041] 2 , a plurality of AlGaN layers 131 are provided in the second nitride semiconductor layer 130. An AlGaN layer 131 is provided between the plurality of AlGaN layers 131. The plurality of AlGaN layers 131 are each provided with the recess 210 described in the first embodiment. That is, in this embodiment, a plurality of recesses 210 are provided in the second nitride semiconductor layer 130. The plurality of recesses 210 all have the same height in the Z direction and the same depth in the X direction.

[0042] According to the present embodiment described above, similarly to the first embodiment, after the trench 200 is formed, the recess 210 is formed in the second nitride semiconductor layer 130. The recess 210 increases the surface area of ​​the exposed surface of the second nitride semiconductor layer 130, making it easier for hydrogen to desorb from the second nitride semiconductor layer 130. As a result, it is possible to avoid high temperature and long time heat treatment, and suppress thermal damage.

[0043] In particular, in this embodiment, the number of recesses 210 is greater than in the first embodiment. This further increases the surface area of ​​the second nitride semiconductor layer 130, making it easier for hydrogen to be desorbed. Therefore, it is possible to further suppress thermal damage.

[0044] 3 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a third embodiment. The following description will focus on the differences from the second embodiment.

[0045] 3, AlGaN layers 131a, 132b, and 132c are provided in the second nitride semiconductor layer 130. The AlGaN layer 131a is provided at the interface with the active layer 120. The AlGaN layer 131b faces the AlGaN layer 131a with the AlGaN layer 131 sandwiched therebetween. The AlGaN layer 131c faces the AlGaN layer 131b with the AlGaN layer 131 sandwiched therebetween. In these AlGaN layers, the aluminum (Al) composition ratio increases in the order of the AlGaN layer 132c, the AlGaN layer 131b, and the AlGaN layer 131a. That is, of the multiple AlGaN layers, the AlGaN layer 131a provided at the interface with the active layer 120 has the highest aluminum (Al) composition ratio.

[0046] Recesses 210a, 210b, and 210c are provided in the AlGaN layers 131a, 132b, and 132c, respectively. Each recess is formed by etching the AlGaN layer with an etching solution having a selectivity with respect to the GaN layer 132, as in the first embodiment. At this time, the etching rate increases as the aluminum composition ratio increases. Therefore, in this embodiment, the depths in the X direction increase in the order of recess 210c, recess 210b, and recess 210a. That is, of the multiple recesses, recess 210a formed in the AlGaN layer 131a disposed at the interface with the active layer 120 is the deepest.

[0047] According to the above-described embodiment, after the trenches 200 are formed, a plurality of depressions are formed in the second nitride semiconductor layer 130. Each depression increases the surface area of ​​the exposed surface of the second nitride semiconductor layer 130, making it easier for hydrogen to desorb from the second nitride semiconductor layer 130. As a result, it is possible to avoid high temperature and long time heat treatment, and suppress thermal damage.

[0048] In particular, in this embodiment, the recess 210a formed in the AlGaN layer 131a disposed at the interface with the active layer 120 is the deepest. A relatively large amount of hydrogen remains in the second nitride semiconductor layer 130 near the interface with the active layer 120. Therefore, by making the depth of the recess 210a the largest, the surface area of ​​the AlGaN layer 131a becomes the largest. As a result, hydrogen desorption is promoted compared to the second embodiment. Therefore, it is possible to further suppress thermal damage compared to the second embodiment.

[0049] In this embodiment, the depth of the recess is adjusted by the aluminum composition ratio contained in each AlGaN layer. However, the depth of the recess can also be adjusted by the thickness of each AlGaN layer. The etching rate increases as the thickness of the AlGaN layer increases. Therefore, for example, if the thicknesses of the AlGaN layers 131c, 131b, and 131a are reduced in this order, the depths of the recesses 210c, 210b, and 210a decrease in this order. In this case, the height in the Z direction depends on the thickness of each AlGaN layer, and therefore decreases in this order: recess 210c, recess 210b, and recess 210a. In this case, the surface area of ​​the AlGaN layer 131a is the largest, which promotes hydrogen desorption and further reduces thermal damage.

[0050] (Modification) Figure 4 is a cross-sectional view showing the structure of a semiconductor light-emitting device according to a modification of the third embodiment. In the semiconductor light-emitting device 3a shown in Figure 4, the aluminum composition ratio increases in the order of the AlGaN layer 132a, the AlGaN layer 131b, and the AlGaN layer 131c. Therefore, the depth in the X direction increases in the order of the recess 210a, the recess 210b, and the recess 210c. Note that in this modification, the thickness may be decreased in the order of the AlGaN layer 131a, the AlGaN layer 131b, and the AlGaN layer 131c. In this case, the depth in the X direction increases in the order of the recess 210a, the recess 210b, and the recess 210c, and the height in the Z direction decreases in the order of the recess 210a, the recess 210b, and the recess 210c.

[0051] In this modification, similarly to the second and third embodiments, a plurality of recesses are provided in the second nitride semiconductor layer 130. Therefore, the surface area of ​​the exposed surface of the second nitride semiconductor layer 130 is increased compared to the first embodiment, and hydrogen is more likely to be desorbed from the second nitride semiconductor layer 130. As a result, it is possible to further suppress thermal damage.

[0052] 5 is a cross-sectional view showing the structure of a semiconductor light-emitting device according to a fourth embodiment. In the semiconductor light-emitting device 4 shown in FIG. 5, a lower surface 211 of a recess 210 is a crystal plane (0001), and an upper surface 212 of the recess 210 is a crystal plane (000-1).

[0053] In this embodiment, when forming the recess 210, the crystal plane (000-1) of the AlGaN layer 131 is etched with an alkaline solvent. In this case, the crystal plane (10-1-1) is exposed, and the surface area of ​​the crystal plane (000-1) increases. As a result, the surface roughness of the crystal plane (000-1) becomes greater than the surface roughness of the crystal plane (0001).

[0054] According to the present embodiment described above, the surface area of ​​the crystal plane (000-1) exposed from the depression 210 is increased, and therefore the surface area of ​​the exposed surface of the second nitride semiconductor layer 130 is increased compared to the first embodiment. This makes it easier for hydrogen to be desorbed from the second nitride semiconductor layer 130, and therefore makes it possible to further suppress thermal damage.

[0055] 6 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a fifth embodiment. The following description will focus on the differences from the first embodiment.

[0056] 6 , the semiconductor light emitting device 5 according to this embodiment is further provided with a dielectric film 220. The dielectric film 220 covers the side and bottom surfaces of the trench 200. The recess 210 is also filled with the dielectric film 220.

[0057] The dielectric film 220 is formed by depositing silicon nitride (SiN) or silicon oxide (SiO) using, for example, sputtering, CVD (Chemical Vapor Deposition), or ALD (Atomic Layer Deposition). ２ ) film.

[0058] According to the present embodiment described above, as in the first embodiment, the surface area of ​​the second nitride semiconductor layer 130 is increased by the recess 210, which makes it easier for hydrogen to be desorbed from the second nitride semiconductor layer 130. This makes it possible to avoid high temperature and long time heat treatment, thereby suppressing thermal damage. Note that the recess 210 in this embodiment is filled with a dielectric film 220, which is made of silicon nitride or silicon oxide and does not prevent hydrogen from being desorbed. Therefore, not only the recess 210 but also the trench 200 may be filled with the dielectric film 220.

[0059] Furthermore, according to this embodiment, the dielectric film 220 can protect the side surfaces of the trench 200 and reduce leakage current.

[0060] 7 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a sixth embodiment. The following description will focus on the differences from the fifth embodiment.

[0061] 7 , the semiconductor light-emitting device 6 according to this embodiment further includes a hydrogen-absorbing metal film 230. The hydrogen-absorbing metal film 230 covers the side surface of the dielectric film 220. The hydrogen-absorbing metal film 230 contains at least a metal that absorbs hydrogen, such as palladium (Pd) or nickel (Ni). Therefore, the trench 200 may be filled with the hydrogen-absorbing metal film 230.

[0062] According to the above-described embodiment, as in the fifth embodiment, a dielectric film 220 is provided that covers the side surfaces of the trench 200 and fills the recess 210, thereby making it possible to suppress thermal damage, protect the side surfaces of the trench 200, and reduce leakage current.

[0063] Furthermore, in this embodiment, the hydrogen storage metal film 230 is also provided, which promotes desorption of hydrogen from the second nitride semiconductor layer 130. This enables heat treatment to be performed in a short time at a low temperature, thereby further suppressing thermal damage to the semiconductor light emitting element 6.

[0064] 8 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a seventh embodiment. The following description will focus on the differences from the fifth embodiment.

[0065] 8, the semiconductor light emitting element 7 according to this embodiment also has a dielectric film 220, similar to the fifth embodiment. However, in this embodiment, the dielectric film 220 is formed on the side and bottom surfaces of the trench 200 but does not fill the recess 210. Therefore, one end of the recess 210 is closed by the dielectric film 220, and the inside of the recess 210 is a void. The dielectric film 220 can be formed by, for example, vapor deposition or sputtering, only on the side and bottom surfaces of the trench 200 without filling the inside of the recess 210.

[0066] Even with the above structure, the recesses 210 promote desorption of hydrogen from the second nitride semiconductor layer 130, so that the heat treatment time and temperature can be shortened, thereby making it possible to suppress thermal damage to the semiconductor light emitting element 7.

[0067] In particular, in this embodiment, the inside of the recess 210 is a void, so that the stress generated inside the semiconductor light emitting element 7 can be reduced.

[0068] 9 is a cross-sectional view showing the structure of a semiconductor light emitting device according to an eighth embodiment. The following description will focus on the differences from the first embodiment.

[0069] 9, the structure of the tunnel junction layer 140 is different from that of the semiconductor light emitting device 1 according to the first embodiment. In the semiconductor light emitting device 1 according to the first embodiment, as shown in FIG. 1, the tunnel junction layer 140 has a two-layer structure in which a p-type GaN layer 141 and an n-type GaN layer 142 are stacked in the Z direction. On the other hand, in the semiconductor light emitting device 8 according to this embodiment, as shown in FIG. 9, the tunnel junction layer 140 has a three-layer structure in which an InGaN layer 143 is stacked between the GaN layer 141 and the GaN layer 142.

[0070] According to this embodiment, the three-layer structure including the InGaN layer 143 makes the tunnel junction layer 140 more conductive than a two-layer structure consisting of the GaN layer 141 and the GaN layer 142. That is, the electrical resistance of the tunnel junction layer 140 is reduced. This makes it possible to lower the driving voltage for causing the semiconductor light emitting element 8 to emit light.

[0071] In this embodiment, as in the first embodiment, the recesses 210 are formed in the second nitride semiconductor layer 130. This increases the surface area of ​​the second nitride semiconductor layer 130, making it easier for hydrogen to be desorbed. This makes it possible to suppress thermal damage to the semiconductor light emitting element 8.

[0072] 10 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a ninth embodiment. The following description will focus on the differences from the first embodiment.

[0073] 10 , the shape of the other end of the recess 210 differs from that of the semiconductor light emitting device 1 according to the first embodiment. In the semiconductor light emitting device 1 according to the first embodiment, the other end of the recess 210 has a vertical surface that is perpendicular to the X direction. On the other hand, in the semiconductor light emitting device 9 according to this embodiment, the other end of the recess 210 has an inclined surface that is inclined with respect to the X direction. Specifically, this inclined surface is inclined obliquely downward with respect to the X direction.

[0074] According to the present embodiment, the surface area of ​​the other end of the recess 210 is increased compared to the first embodiment, which further promotes desorption of hydrogen from the second nitride semiconductor layer 130. This makes it possible to further suppress thermal damage to the semiconductor light emitting element 8.

[0075] 11 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a tenth embodiment. The following description will focus on the differences from the above-described ninth embodiment.

[0076] 11 , the shape of the other end of the recess 210 differs from that of the semiconductor light emitting device 1 according to the ninth embodiment. In the semiconductor light emitting device 1 according to the ninth embodiment, the other end of the recess 210 has an inclined surface that is inclined obliquely downward with respect to the X direction, as described above. On the other hand, in the semiconductor light emitting device 10 according to this embodiment, the other end of the recess 210 has an inclined surface that is inclined obliquely upward with respect to the X direction, as shown in FIG.

[0077] In this embodiment, the surface area of ​​the other end of the recess 210 is also increased compared to the first embodiment, which further promotes desorption of hydrogen from the second nitride semiconductor layer 130. This makes it possible to further suppress thermal damage to the semiconductor light emitting element 10.

[0078] 12 is a cross-sectional view showing the structure of a semiconductor light emitting device according to an eleventh embodiment. The following description will focus on the differences from the above-described ninth embodiment.

[0079] 12, the shape of the other end of the recess 210 differs from that of the semiconductor light emitting device 1 according to the ninth embodiment. In the semiconductor light emitting device 1 according to the ninth embodiment, the other end of the recess 210 has an inclined surface that is inclined obliquely downward with respect to the X direction, as described above. On the other hand, in the semiconductor light emitting device 11 according to this embodiment, the other end of the recess 210 has an inclined surface that is inclined obliquely downward and an inclined surface that is inclined obliquely upward with respect to the X direction, as shown in FIG.

[0080] In this embodiment, the surface area of ​​the other end of the recess 210 is also increased compared to the first embodiment, which further promotes desorption of hydrogen from the second nitride semiconductor layer 130. This makes it possible to further suppress thermal damage to the semiconductor light emitting element 11.

[0081] 12th Embodiment Fig. 13 is a cross-sectional view showing the structure of a semiconductor light emitting device according to a 12th embodiment. As shown in Fig. 13, when a trench 200 is formed in the semiconductor light emitting device 12 by RIE, the side surface of the trench 200 may become uneven rather than flat.

[0082] Therefore, in this embodiment, the surface roughness of the side surface of trench 200 is defined as the maximum height difference Δh in the X direction, and recess 210 is formed in second nitride semiconductor layer 130 so that the depth D in the X direction is greater than the maximum height difference Δh. In other words, recess 210 is formed so as to extend further inward than the convex portion on the side surface of trench 200. This increases the surface area of ​​second nitride semiconductor layer 130.

[0083] Therefore, according to this embodiment, hydrogen is easily desorbed from the second nitride semiconductor layer 130, so that the heat treatment can be avoided from being performed for a long time and at a high temperature, thereby making it possible to suppress thermal damage to the semiconductor light emitting element 12.

[0084] 13th Embodiment Fig. 14 is a cross-sectional view showing the structure of a semiconductor light-emitting device according to a 13th embodiment. The semiconductor light-emitting device 13 shown in Fig. 14 is a type of VCSEL. Specifically, the semiconductor light-emitting device 13 further includes a first light-reflecting layer 160 and a second light-reflecting layer 170 in addition to the components of the semiconductor light-emitting device 1 according to the first embodiment.

[0085] The first light reflecting layer 160 is laminated on the back surface side (opposite to the light irradiation direction) of the substrate 100. The first light reflecting layer 160 functions as a DBR (Distributed Bragg Reflector) that reflects specific color light. In the first light reflecting layer 160, two types of layers with different optical refractive indices are alternately laminated along the Z direction. For example, one layer is Ta ２ O ５ layer, and the other layer is SiO ２ It is a layer.

[0086] The second light reflecting layer 170 is laminated on the upper surface of the third nitride semiconductor layer 150. The second light reflecting layer 170 also functions as a DBR, similar to the first light reflecting layer 160. The second light reflecting layer 170 has two types of layers with different optical refractive indices laminated alternately along the Z direction. For example, one layer is made of Ta ２ O ５ layer, and the other layer is SiO ２ It is a layer.

[0087] The first light reflecting layer 160 and the second light reflecting layer 170 are configured as an optical resonator that reflects light generated in the active layer 120 back and forth in the Z direction. In this embodiment, the tunnel junction layer 140 is formed only within the optical path of this optical resonator. This forms a current confinement structure, making it easier for the current flowing through the tunnel junction layer 140 to be concentrated within the optical resonator.

[0088] In the semiconductor light emitting element 13 configured as described above, as in the other embodiments, the recess 210 is formed in the second nitride semiconductor layer 130. This increases the surface area of ​​the second nitride semiconductor layer 130. This makes it possible to avoid prolonged heat treatment times and high temperatures, thereby suppressing thermal damage to the semiconductor light emitting element 13.

[0089] 14th Embodiment Fig. 15 is a cross-sectional view showing the structure of a semiconductor light-emitting device according to a 14th embodiment. The semiconductor light-emitting device 14 shown in Fig. 15 is a type of VCSEL, similar to the semiconductor light-emitting device 13 according to the 14th embodiment described above. However, the structures of the substrate 100 and the first light-reflecting layer 160 differ from those of the 13th embodiment.

[0090] The substrate 100 according to this embodiment has a lens 101. The lens 101 has a convex shape that protrudes from the rear surface of the substrate 100. The lens 101 can be formed, for example, by etching the substrate 100 using a resist as an etching mask.

[0091] On the other hand, the first light reflecting layer 160 according to this embodiment has a concave mirror 161. The concave mirror 161 has a concave shape that faces the convex shape of the lens 101 of the substrate 100. The lens 101 and the concave mirror 161 are formed at a position facing the tunnel junction layer 140 in the Z direction, that is, in the optical path of the optical resonator. As a result, the resonator length L is shorter than that of the fourteenth embodiment. ＯＲ becomes longer. Here, the resonator length L ＯＲ 15 , is the distance between the inner surface of the concave mirror 161 and the inner surface of the second light reflecting layer 170. The inner surface of the concave mirror 161 is the surface that contacts the lens 101. On the other hand, the inner surface of the second light reflecting layer 170 is the surface that faces the inner surface of the concave mirror 161 in the Z direction.

[0092] In the semiconductor light emitting element 14 configured as described above, as in the other embodiments, the recess 210 is formed in the second nitride semiconductor layer 130. This increases the surface area of ​​the second nitride semiconductor layer 130. This makes it possible to avoid prolonged heat treatment times and high temperatures, thereby suppressing thermal damage to the semiconductor light emitting element 13.

[0093] Furthermore, in this embodiment, the lens 101 and the concave mirror 161 make the resonator length L ＯＲ In the semiconductor light emitting element 14, the wavelength that can be oscillated is determined by the resonator length L ＯＲ The individual oscillation modes that can oscillate are called longitudinal modes. The spacing between longitudinal modes is determined by the resonator length L ＯＲ Therefore, the longer the resonator length L ＯＲ If the wavelength is long, it is possible to oscillate at the wavelength with the highest gain.

[0094] The present technology can be configured as follows:

[0095] (1) A semiconductor light-emitting device comprising: a first nitride semiconductor layer of a first conductivity type; an active layer provided on the first semiconductor layer; a second nitride semiconductor layer of a second conductivity type provided on the active layer; a tunnel junction layer provided on the second semiconductor layer; a third nitride semiconductor layer of the first conductivity type provided on the tunnel junction layer; and a trench extending in a first direction from the third nitride semiconductor layer to the first nitride semiconductor layer, wherein the second nitride semiconductor layer has a recess extending in a second direction intersecting the first direction, one end of the recess being open and communicating with the trench, and the other end of the recess terminating within the second nitride semiconductor layer.

[0096] (2) The semiconductor light-emitting element according to (1), wherein the semiconductor light-emitting element is a light-emitting diode (LED), a laser diode (LD), or a vertical cavity surface emitting laser (VCSEL).

[0097] (3) The semiconductor light emitting device according to (1) or (2), wherein the recess is provided at the interface between the active layer and the second nitride semiconductor layer.

[0098] (4) The semiconductor light-emitting element according to any one of (1) to (3), wherein the recess has a height of 10 nm or more in the first direction and a depth of 10 nm or more in the second direction.

[0099] (5) The semiconductor light-emitting element according to any one of (1) to (4), wherein the other end of the recess has an inclined surface inclined with respect to the second direction.

[0100] (6) The semiconductor light-emitting element according to (4), wherein the depth of the recess is greater than the maximum height difference in the second direction that indicates the surface roughness of the side surface of the trench.

[0101] (7) The semiconductor light emitting device according to any one of (1) to (6), wherein the second nitride semiconductor layer has a plurality of recesses.

[0102] (8) The semiconductor light-emitting element according to (7), wherein at least one of the height in the first direction and the depth in the second direction differs among the plurality of recesses.

[0103] (9) The semiconductor light-emitting element according to any one of (1) to (8), further comprising a dielectric film that covers the side surface of the trench and fills the depression.

[0104] (10) The semiconductor light-emitting element according to (9), further comprising a hydrogen-absorbing metal film containing at least palladium (Pd) or nickel (Ni) on a side surface of the dielectric film covering the side surface of the trench.

[0105] (11) The semiconductor light-emitting element according to any one of (1) to (8), further comprising a dielectric film covering the side surface of the trench and closing one end of the depression.

[0106] (12) The semiconductor light-emitting element according to any one of (1) to (11), wherein the side surface of the trench and the surface of the depression have both a crystalline plane and a non-crystalline plane.

[0107] (13) The semiconductor light-emitting element according to any one of (1) to (12), wherein the surface of the depression has a crystal plane (0001) and a crystal plane (000-1), and the surface roughness of the crystal plane (000-1) is greater than the surface roughness of the crystal plane (0001).

[0108] (14) The semiconductor light-emitting element according to any one of (1) to (13), wherein the surface of the depression has an element selected from the group consisting of silicon (Si), carbon (C), fluorine (F), chlorine (Cl), and boron (B), or a compound of these elements.

[0109] (15) The semiconductor light-emitting element according to any one of (1) to (14), further comprising a first optical reflection layer and a second optical reflection layer facing each other with the active layer sandwiched in the first direction, wherein the tunnel junction layer is provided only within an optical path of an optical resonator formed by the first optical reflection layer and the second optical reflection layer.

[0110] (16) The tunnel junction layer is composed of a p-type GaN layer and an n-type GaN layer, and a p-type impurity concentration of the p-type GaN layer and an n-type impurity concentration of the n-type GaN layer are each 5×10 １９ cm ２ The semiconductor light-emitting element according to any one of (1) to (15) above.

[0111] (17) The semiconductor light-emitting device according to any one of (1) to (15), wherein the tunnel junction layer includes a p-type GaN layer, an n-type GaN layer, and an InGaN layer provided between the p-type GaN layer and the GaN layer.

[0112] 1 to 14: Semiconductor light emitting element 110: First nitride semiconductor layer 120: Active layer 130: Second nitride semiconductor layer 140: Tunnel junction layer 141: P-type GaN layer 142: N-type GaN layer 143: InGaN layer 150: Third nitride semiconductor layer 160: First light reflective layer 170: Second light reflective layer 200: Trench 210: Recess 220: Dielectric film 230: Hydrogen storage metal film

Claims

1. A semiconductor light-emitting device comprising: a first nitride semiconductor layer of a first conductivity type; an active layer provided on the first semiconductor layer; a second nitride semiconductor layer of a second conductivity type provided on the active layer; a tunnel junction layer provided on the second semiconductor layer; a third nitride semiconductor layer of the first conductivity type provided on the tunnel junction layer; and a trench extending in a first direction from the third nitride semiconductor layer to the first nitride semiconductor layer, wherein the second nitride semiconductor layer has a depression extending in a second direction intersecting the first direction, one end of the depression is open and communicates with the trench, and the other end of the depression terminates within the second nitride semiconductor layer.

2. The semiconductor light-emitting device according to claim 1, wherein the semiconductor light-emitting device is an LED (Light-Emitting Diode), an LD (Laser Diode), or a VCSEL (Vertical Cavity Surface Emitting Laser).

3. The semiconductor light-emitting device according to claim 1, wherein the depression is provided at an interface between the active layer and the second nitride semiconductor layer.

4. The semiconductor light-emitting device according to claim 1, wherein the depression has a height of 10 nm or more in the first direction and a depth of 10 nm or more in the second direction.

5. The semiconductor light-emitting device according to claim 1, wherein the other end of the depression has an inclined surface inclined with respect to the second direction.

6. The semiconductor light-emitting device according to claim 4, wherein the depth of the depression is greater than a maximum height difference in the second direction indicating surface roughness on a side surface of the trench.

7. The semiconductor light-emitting device according to claim 1, wherein the second nitride semiconductor layer has a plurality of depressions.

8. The semiconductor light-emitting device according to claim 7, wherein at least one of a height in the first direction and a depth in the second direction is different between the plurality of depressions.

9. The semiconductor light-emitting device according to claim 1, further comprising a dielectric film covering a side surface of the trench and filling the depression.

10. The semiconductor light-emitting device according to claim 9, further comprising a hydrogen storage metal film containing at least palladium (Pd) or nickel (Ni) on a side surface of the dielectric film covering the side surface of the trench.

11. The semiconductor light-emitting device according to claim 1, further comprising a dielectric film covering a side surface of the trench and closing one end of the depression.

12. The semiconductor light-emitting device according to claim 1, wherein the side surface of the trench and the surface of the depression have both a crystal plane and an amorphous plane.

13. The semiconductor light-emitting device according to claim 1, wherein the surface of the depression has a crystal plane (0001) and a crystal plane (000-1), and the surface roughness of the crystal plane (000-1) is greater than the surface roughness of the crystal plane (0001).

14. The semiconductor light-emitting device according to claim 1, wherein the surface of the depression has an element of silicon (Si), carbon (C), fluorine (F), chlorine (Cl), or boron (B), or a compound of these elements.

15. The semiconductor light-emitting device according to claim 1, further comprising a first light reflection layer and a second light reflection layer that face each other with the active layer sandwiched therebetween in the first direction, wherein the tunnel junction layer is provided only within the optical path of an optical resonator composed of the first light reflection layer and the second light reflection layer.

16. The tunnel junction layer is composed of a p-type GaN layer and an n-type GaN layer, and the p-type impurity concentration of the p-type GaN layer and the n-type impurity concentration of the n-type GaN layer are each 5×10 １９ cm ２ or more. The semiconductor light-emitting device according to claim 1.

17. The semiconductor light-emitting device according to claim 1, wherein the tunnel junction layer includes a p-type GaN layer, an n-type GaN layer, and an InGaN layer provided between the p-type GaN layer and the n-type GaN layer.

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