Vertical resonator-type light-emitting element and method for manufacturing vertical resonator-type light-emitting element

Abstract

This method comprises steps for: forming a first reflector; forming a first semiconductor layer on the first reflector; forming a multiple quantum well layer that includes first to n-th well layers (n being an integer of 3 or more) on the first semiconductor layer; forming a final barrier layer on the n-th well layer, which is the final well layer of the multiple quantum well layer; forming an electron barrier layer on the final barrier layer; forming a second semiconductor layer on the electron barrier layer; and forming a second reflector on the second semiconductor layer. The first to n-th well layers have In in the composition, and are grown by using nitrogen (N2) as a carrier gas. In the step for forming the final barrier layer, the growth temperature is raised, and hydrogen (H2) is added to the carrier gas for growth.

Description

Vertical resonator type light-emitting element and method for manufacturing a vertical resonator type light-emitting element

[0001] The present invention relates to a vertical resonator type light-emitting element and a method for manufacturing a vertical resonator type light-emitting element, and more particularly to a vertical resonator type light-emitting element having a multiple quantum well active layer and a method for manufacturing a vertical resonator type light-emitting element.

[0002] Conventionally, vertical cavity surface-emitting lasers (VCSELs) and other vertical cavity-type light-emitting devices are known, which have a structure that resonates light perpendicular to the substrate surface and emits light in a direction perpendicular to the substrate surface.

[0003] In vertical-cavity light-emitting devices, a multiple quantum well (MQW) structure is generally employed in the active layer to obtain low threshold current and highly efficient light emission characteristics.

[0004] For example, Patent Document 1 describes an end-emitting nitride semiconductor laser element having a structure aimed at improving internal quantum efficiency by lowering the electron and hole concentrations in the p-side optical guide layer between the final quantum well layer and the electron barrier layer.

[0005] Furthermore, Patent Documents 2 and 3 describe a mechanism for improving characteristics while considering standing waves in a resonator.

[0006] Furthermore, Non-Patent Documents 1 and 2 describe an effect called CPE (Compositional pulling effect) in crystal growth, and the segregation of InGaN / GaN and AlGaN / AlN, respectively.

[0007] Japanese Patent Publication No. 2014-131019, Japanese Patent Publication No. 2024-131244, Japanese Patent Publication No. 2023-43084

[0008] S. Pereira et al., Physical Review B, vol.64, 205311(2001)B. Liu et al., Applied Physics Letters 98, 261916(2011)

[0009] In conventional vertical resonator light-emitting devices, further reduction of the threshold current and improvement of luminous efficiency were challenges.

[0010] The inventors of this invention have found that even when each quantum well layer of a multiple quantum well active layer is formed through a manufacturing process under the same conditions (e.g., growth temperature, growth time, raw material gas phase ratio, etc.), non-uniformity occurs in the peak gain wavelength (band gap) of each quantum well layer, leading to a decrease in threshold current and luminous efficiency. The present invention is based on this finding and aims to provide a vertical resonator type light-emitting element with a low threshold current density and high luminous efficiency, as well as a method for manufacturing a vertical resonator type light-emitting element.

[0011] A method for manufacturing a vertical resonator type light-emitting element according to one embodiment of the present invention comprises the steps of: forming a first reflector; forming a first semiconductor layer on the first reflector; forming a multiple quantum well layer on the first semiconductor layer, which includes first to n well layers (where n is an integer of 3 or more); forming a final barrier layer on the nth well layer, which is the final well layer of the multiple quantum well layer; forming an electron barrier layer on the final barrier layer; forming a second semiconductor layer on the electron barrier layer; and forming a second reflector on the second semiconductor layer, wherein the first to n well layers have a composition of In and nitrogen (N ２ The final barrier layer is formed by growing the material with hydrogen (H) as the carrier gas, and the growth temperature is increased and the carrier gas is changed to hydrogen (H) ２ ) is added to promote growth.

[0012] A vertical resonator light-emitting element according to another embodiment of the present invention comprises: a first reflector; a first semiconductor layer formed on the first reflector; an active layer formed on the first semiconductor layer and comprising a multiple quantum well layer including first to n well layers (where n is an integer of 3 or more) and a final barrier layer formed on the nth well layer which is the final well layer of the multiple quantum well layer; an electron barrier layer formed on the final barrier layer; a second semiconductor layer formed on the electron barrier layer; and a second reflector formed on the second semiconductor layer, wherein the first to n well layers have In in their composition, the nth well layer has a smaller In composition than the (n-1)th well layer, and when the peak gain wavelengths of the first to n well layers are λp(1), ..., λp(n-1), λp(n), the peak gain wavelengths are: The equation (1) satisfies λp(1) < ... < λp(n-1) and λp(1) < λp(n) < λp(n-1).

[0013] This is a schematic cross-sectional view showing the structure of a vertical-cavity surface-emitting laser (VCSEL) according to the first embodiment of the present invention. This is a schematic diagram showing the band structure of the conduction band of the vertical-cavity surface-emitting laser. This is a flowchart showing the manufacturing method of the vertical-cavity surface-emitting laser. This is a schematic diagram showing the gain profile and combined gain profile of each quantum well layer of a multiple quantum well active layer (CMP) grown under the same growth conditions for all well layers and all barrier layers. This is a schematic diagram showing the gain profile and combined gain profile of each quantum well layer of the active layer (EMB) of the first embodiment. This is a diagram showing the results of In composition analysis of the well layers (QW1 to QW4) of the active layer (EMB) of the first embodiment by EDX. This is a table showing the experimental results of the final barrier layer thickness, average Al composition of the electron barrier layer, and internal quantum efficiency of Examples 1 and 2 of the vertical-cavity surface-emitting laser of this embodiment, compared with the experimental results of Comparative Examples 1 and 2. N as the carrier gas ２ H ２ Example 1, in which N was added as a carrier gas, ２ This graph shows the temperature characteristics of Comparative Example 1, which uses [the specified method / technology].

[0014] Preferred embodiments of the present invention will be described below, but these may be modified and combined as appropriate. In the following description and accompanying drawings, substantially identical or equivalent parts will be denoted by the same reference numerals.

[0015] [First Embodiment] (1) Structure of a Vertical Cavity Surface Emitting Laser Figure 1 is a schematic cross-sectional view showing the structure of a vertical cavity surface emitting laser 10 (VCSEL) according to the first embodiment of the present invention. In this embodiment, the vertical cavity surface emitting laser 10 is a nitride surface emitting laser made of a GaN (gallium nitride) semiconductor layer.

[0016] The vertical-cavity surface-emitting laser 10, which is a vertical-cavity light-emitting element, is constructed by sequentially forming a semiconductor DBR (Distributed Bragg Reflector) 12 (first reflector), an n-type semiconductor layer 13 (first semiconductor layer), an active layer 15 consisting of multiple quantum wells, an electron barrier layer (EBL: Electron Blocking Layer) 17, and a p-type semiconductor layer 18 (second semiconductor layer) on a substrate 11 in this order. The active layer 15 is composed of a multiple quantum well layer 15Q and a final barrier layer 15L.

[0017] Furthermore, the vertical-cavity surface-emitting laser 10 includes an insulating film 21 (current constriction layer) for current and light confinement formed in the recesses surrounding a p-type semiconductor layer 18 having a circular convex portion, a transparent conductive film 22 provided on the p-type semiconductor layer 18 and the insulating film 21, a spacer layer 24 provided on the transparent conductive film 22, and a dielectric DBR 25 (second reflector) provided on the spacer layer 24. Note that the spacer layer 24 may be omitted, and the dielectric DBR 25 may be formed on the transparent conductive film 22.

[0018] Furthermore, the vertical cavity surface-emitting laser 10 has an n electrode 27 electrically connected to the n-type semiconductor layer 13 and a p electrode 28 electrically connected to the transparent conductive film 22.

[0019] The first reflector 12 and the second reflector 25 constitute a resonator, and the light emitted from the active layer 15 is emitted through the circular aperture of the insulating film 21 (the convex portion of the p-type semiconductor layer 18) (emitted light LE).

[0020] The thicknesses of the n-type semiconductor layer 13 (first semiconductor layer) and the p-type semiconductor layer 18 (second semiconductor layer) can be appropriately adjusted according to the design values ​​of the position of the active layer 15 and insulating film 21 (current constriction layer) and the resonator length relative to the intensity distribution of standing waves within the resonator. The distance between the first reflector 12 and the second reflector 25 is preferably a natural number multiple of the wavelength λ within the medium (n × λ, where n is a natural number).

[0021] To efficiently confine light in the light emission (vertical) direction, it is preferable to design the active layer 15 to be located in the region corresponding to the antinode of the standing wave intensity distribution.

[0022] Furthermore, it is preferable that at least one antinode of a standing wave is located within the final barrier layer 15L. From this perspective, it is preferable that the thickness of the final barrier layer 15L is 40 nm or more.

[0023] Figure 2 schematically shows the band structure of the conduction band of the vertical-cavity surface-emitting laser 10. Note that the band structure from the n-type semiconductor layer 13 to the p-type semiconductor layer 18 is shown.

[0024] The active layer 15 consists of a multiple quantum well layer 15Q and a final barrier layer 15L formed on the final well layer 15WL of the multiple quantum well layer 15Q. The multiple quantum well layer 15Q consists of four well layers 15W labeled QW1 to QW4 and a barrier layer 15B provided between them.

[0025] Here, the final well layer (QW4) of the four well layers 15W will be specifically referred to as the final well layer 15WL. The final well layer 15WL (QW4) is a well layer adjacent to the final barrier layer 15L (LB).

[0026] The barrier layer 15B and the final barrier layer 15L have the same crystal composition. Also, the final barrier layer 15L is an intermediate layer between the final well layer 15WL and the electron barrier layer 17. The final barrier layer 15L is a layer thicker than the barrier layer 15B, which has a function of preventing the leakage of electrons contained in the multiple quantum well layer 15Q and preventing the intrusion of impurities (for example, impurities in the semiconductor layer such as the intrusion of excess In in the crystal growth atmosphere) into the multiple quantum well layer 15Q. Note that the final barrier layer 15L may have a layer with a composition different from that of the barrier layer 15B in addition to the layer with the same composition as the barrier layer 15B between the layer with the same composition and the electron barrier layer 17.

[0027] The final barrier layer 15L has a layer thickness t1, the electron barrier layer 17 formed on the final barrier layer 15L has a layer thickness t2, and the p-type semiconductor layer 18 has a layer thickness t3.

[0028] (2) Method for manufacturing a vertical cavity surface emitting laser Hereinafter, a method for manufacturing the vertical cavity surface emitting laser 10 will be described with reference to the manufacturing flowchart shown in FIG. 3.

[0029] (Step S11) Crystal growth of a semiconductor stacked structure was performed by metalorganic vapor phase epitaxy (MOVPE). First, an underlying GaN layer 11B having a layer thickness of about 1 μm was grown on the substrate 11. The substrate 11 is a GaN substrate, which is a C-plane GaN substrate inclined 0.5° in the direction from the C-plane to the M-plane and 0 ± 0.1° in the A-plane direction.

[0030] Note that the case of manufacturing using the MOVPE method will be described as an example, but it can also be manufactured by other known crystal growth methods such as molecular beam epitaxy (MBE).

[0031] Subsequently, a semiconductor DBR 12, which is a distributed Bragg reflector, was formed on the underlying GaN layer​​(Step S12) An n-type semiconductor layer 13 (first semiconductor layer), which is an n-type GaN layer doped with Si (silicon), was grown on the semiconductor DBR12 to a layer thickness of 350 nm.

[0033] (Step S13) Subsequently, barrier layers (barrier layers) 15B and quantum well layers (well layers) 15W were alternately formed on the n-type semiconductor layer 13 to form a multiple quantum well layer 15Q having four well layers 15W. That is, growth was performed up to the final well layer 15WL of the multiple quantum well layer 15Q. Note that only nitrogen (N ２ ) was used as the carrier gas.

[0034] The crystal growth of the four well layers 15W was performed under the same growth conditions, that is, the growth temperature, raw material gas ratio, growth time, etc. were made the same. Also, crystal growth of each of the barrier layers 15B was performed under the same growth conditions.

[0035] The well layer 15W is made of GaInN (layer thickness: 3 nm), and the barrier layer 15B is made of GaN (layer thickness: 4 nm). Note that the composition and layer thickness of the barrier layer 15B and the four well layers 15W can be appropriately selected according to the desired emission wavelength, emission characteristics, etc.

[0036] In this specification, the four well layers 15W will be described in order of growth as the first well layer QW1, the second well layer QW2, the third well layer QW3, and the fourth well layer QW4 (final well layer).

[0037] (Step S14) Next, undoped GaN was grown as the final barrier layer 15L to a layer thickness of 120 nm on the final well layer 15WL (QW4) of the multiple quantum well layer 15Q.

[0038] More specifically, first, a thin GaN layer (not shown) was grown under the same growth conditions as the barrier layer 15B. The GaN layer functions as a cap layer and has a layer thickness of 1 - 10 nm. Note that it is preferable to grow the cap layer, but it may not be grown.

[0039] Subsequently, the growth temperature was increased by 50°C, and hydrogen (H ２ ) was added to nitrogen (N ２was added to grow the final barrier layer 15L. When growing the final barrier layer 15L, it is preferable to increase the growth temperature within the range of 25 to 200 °C. Also, the growth temperature of the final barrier layer 15L is preferably within the range of 1000 to 1500 °C.

[0040] The hydrogen (H ２ ) partial pressure in the growth gas, that is, (hydrogen flow rate) / (hydrogen flow rate + nitrogen flow rate + NH ３ flow rate) was 35%. Here, NH ３ (ammonia) is a Group V source gas.

[0041] By increasing the growth temperature and also increasing the hydrogen partial pressure, the In composition of the final well layer 15WL can be reduced, and the peak gain wavelength of the final well layer 15WL can be reduced.

[0042] Note that the hydrogen partial pressure when growing the final barrier layer 15L is preferably 10% or more, more preferably 35% or more. Also, the hydrogen partial pressure is preferably 87.5% or less. Regarding the nitrogen flowing as a sub-flow (counter-flow), it may be changed to hydrogen. Also, by forming a cap layer, it is preferable in that it can suppress a rapid reduction in the In composition of the final well layer 15WL when the growth temperature is increased and the final barrier layer 15L is grown by adding hydrogen to the carrier gas. Thereby, it becomes easier to form the final well layer 15WL that emits a desired peak gain wavelength.

[0043] (Step S15) Next, an EBL layer (electron barrier layer) 17 made of AlGaN doped with Mg (magnesium) and having a total layer thickness of 10 nm was grown. As shown in FIG. 2, the electron barrier layer 17 was formed as a two-stage electron barrier layer. More specifically, the electron barrier layer 17 includes a first electron barrier layer 17A made of AlGaN doped with Mg (Al composition: 0.42) and having a layer thickness of 6 nm, and a second electron barrier layer 17B made of AlGaN doped with Mg (Al composition: 0.30) and having a layer thickness of 4 nm.

[0044] Furthermore, a vertical-cavity surface-emitting laser 10 was also fabricated in which the electron barrier layer 17 consists of a single layer of Mg-doped AlGaN (Al composition: 0.30) and has a layer thickness of 10 nm.

[0045] (Step S16) Next, a p-GaN layer was grown on the electron barrier layer 17 (p-AlGaN) as a p-type semiconductor layer 18 (second semiconductor layer) with a wavelength of 83 nm.

[0046] (Step S17) The wafer grown in the manner described above was etched at its outer periphery to reach the interior of the n-type semiconductor layer 13, thereby forming a cylindrical mesa-shaped semiconductor stacked structure.

[0047] Next, the outer periphery of the p-type semiconductor layer 18, which is the uppermost semiconductor layer of the mesa structure, was etched to a depth of approximately 20 nm by dry etching to form recesses, thereby forming a p-type semiconductor layer 18 having cylindrical mesa protrusions.

[0048] In the recesses of the p-type semiconductor layer 18 formed by etching, an insulating film (SiO₂) is used for lateral current and photoconfinement. ２ ) 21 was deposited to a thickness of 20 nm. As a result, the recesses of the p-type semiconductor layer 18 were flattened, a current-constricting structure was formed, and a cylindrical (central axis: ZC) current injection region was formed. Here, the insulating film 21 may be formed to extend to the side surface of the cylindrical mesa-shaped semiconductor structure layer or to the upper surface of the n-type semiconductor layer 13 (not shown).

[0049] Next, an ITO (indium tin oxide) film with a thickness of 20 nm was deposited on the p-type semiconductor layer 18 and the insulating film 21 as a transparent conductive film 22.

[0050] (Step S18) Next, a dielectric (Nb) is used as the spacer layer 24. ２ O ５ A film was deposited with a thickness of 38 nm. The spacer layer 24 functions as a phase adjustment layer.

[0051] Furthermore, a dielectric DBR25 (second reflector) was deposited on the spacer layer 24. Dielectric DBR25 is SiO ２ (11 layers) and Nb ２ O ５It consists of 10.5 pairs of (10 layers). Preferably, the dielectric DBR 25 is formed coaxially with the cylindrical mesa of the p-type semiconductor layer 18.

[0052] (Step S19) Next, an n electrode 27 was formed on the recess on the outer periphery of the n-type semiconductor layer 13, and a p electrode 28 was formed on the transparent conductive film 22. The back surface of the substrate 11 was polished, and Nb ２ O ５ / SiO ２ An AR (anti-reflective) coating 29 consisting of two layers was formed. With this, the formation of the vertical cavity surface-emitting laser 10 was completed.

[0053] Furthermore, the final barrier layer 15L described above is not limited to GaN. That is, although the final barrier layer 15L was described as a GaN layer, nitride semiconductor layers of other compositions, such as InGaN, AlGaN, InAlGaN, etc., may also be used. In addition, although the final barrier layer 15L was described as an undoped layer, it may contain dopants diffused from the electron barrier layer 17 or the p-type semiconductor layer 18.

[0054] Furthermore, the composition and thickness of the electron barrier layer 17 are merely examples. The electron barrier layer 17 may have a thickness of, for example, 3 to 30 nm, and the Al composition may be adjusted within the range of 10 to 70%.

[0055] Although the electron barrier layer 17 was described as a p-type semiconductor layer (p-AlGaN), it may also be a p-type semiconductor layer that was grown as an i-layer and contains dopants diffused from the p-type semiconductor layer 18.

[0056] Furthermore, although the example given shows that the active layer 15 has four well layers 15W, it is sufficient to have three or more well layers.

[0057] Furthermore, the p-type semiconductor layer 18 may be composed of multiple semiconductor layers, including layers with different compositions and / or doping concentrations, and an undoped layer. Similarly, the n-type semiconductor layer 13 may also be composed of multiple semiconductor layers.

[0058] The dielectric DBR25 is SiO ２ Membrane and Nb ２ O ５Although the example given illustrates the case where the material consists of films, it may also be composed of dielectric films with different refractive indices in other combinations. Alternatively, it may be composed of semiconductor DBRs made up of semiconductor films with different refractive indices.

[0059] (3) Multiple quantum well active layer and peak gain wavelength In the vertical cavity surface-emitting laser 10 described above, the active layer 15 has four well layers 15W (QW1 to QW4). The present invention has been made in view of the problems that arise when crystal growth is performed on all barrier layers, including the final barrier layer, under the same growth conditions.

[0060] Figure 4A schematically shows the gain profiles (dashed lines) and combined gain profile GAc (solid lines) of each well layer (QW1c to QW4c) and all barrier layers, including the final barrier layer, of a comparative example of a multiple quantum well active layer (CMP) having four well layers (QW1c to QW4c) grown under the same growth conditions. Figure 4B schematically shows the gain profiles (dashed lines) and combined gain profile GA (solid lines) of each well layer (QW1 to QW4) of the active layer 15 (EMB) of this embodiment.

[0061] Figure 5 also shows the results of the analysis of the In composition (z) of each well layer (QW1 to QW4) of the active layer 15 (EMB) in this embodiment using EDX (energy-dispersive X-ray analysis).

[0062] When all well layers of a multiple quantum well active layer are grown under the same growth conditions, and all barrier layers are grown under the same growth conditions (comparative example), that is, even if the growth temperature, raw material gas phase ratio, growth time, etc. are the same, when driven by current, the peak gain wavelengths will not be the same, and the gain profiles will be separated, as shown in Figure 4A.

[0063] This is due to a growth mechanism called CPE (Compositional Pulling Effect) when growing quantum well layers (see Non-Patent Documents 1 and 2). More specifically, the amount of atoms (In: indium) incorporated changes depending on the amount of strain on the growth surface.

[0064] Furthermore, because the amount of strain differs in each quantum well layer, the band structure is deformed by the piezoelectric effect. In addition, since the effective mass of electrons and holes is larger compared to other material systems, a spatial distribution occurs in the carrier density during operation.

[0065] These three main factors occur in a complex manner, resulting in the phenomenon where the peak gain wavelength differs for each quantum well layer.

[0066] In a growth method for multiple quantum well active layers, where the quantum well layers (well layers) and barrier layers are grown under the same growth conditions, the peak gain wavelength increases in the order of well layers QW1c to QW4c, i.e., in the growth order, as schematically shown in Figure 4A. Therefore, the combined gain profile GAc is broad, and the combined peak gain is small. The interval between the peak gain wavelengths of each well layer was approximately 3.6 nm.

[0067] On the other hand, as shown in Figure 4B, in the active layer 15 of this embodiment (EMB), the peak gain wavelength of the fourth well layer QW4 (final well layer) is smaller than the peak gain wavelength of the preceding third well layer QW3; that is, it has a peak gain on the shorter wavelength side than the third well layer QW3. Therefore, the combined gain profile GA is narrower and the combined peak gain is larger.

[0068] Furthermore, for ease of understanding, the In composition (z1 to z4, dashed line) of the first well layer QW1 to the fourth well layer QW4 has been added to the EDX measurement results in Figure 5. The horizontal axis of the figure represents the position of the first well layer QW1 to the fourth well layer QW4.

[0069] As shown in Figure 5, the In composition (z1 to z3) increases in the order from the first well layer QW1 to the third well layer QW3, but the In composition (z4) of the fourth well layer QW4 is smaller than the In composition (z3) of the third well layer QW3, and larger than the In composition (z1) of the first well layer QW1.

[0070] In other words, the energy band gap of the fourth well layer QW4 is larger than that of the third well layer QW3, and the peak gain wavelength of the fourth well layer QW4 is at a shorter wavelength than that of the third well layer QW3.

[0071] Therefore, the composite gain profile GA in the active layer 15 of this embodiment (EMB) is narrower than that of the multiple quantum well active layer (CMP) of the comparative example, resulting in a larger peak gain and a higher luminescence gain. Furthermore, the increased peak gain allows for a lower threshold current density.

[0072] In other words, in the active layer 15 of this embodiment (EMB), when the peak gain wavelengths of the well layers QW1 to QW4 are λp(1), λp(2), λp(3), and λp(4), respectively, λp(1) < λp(2) < λp(3) and λp(1) < λp(4) < λp(3).

[0073] Although the example given was that the active layer 15 consists of four well layers, in general, the active layer 15 may consist of n well layers (QW(1) to QW(n) in order of growth, where n is an integer of 3 or more). In this case, the peak gain wavelength of the nth well layer QW(n), which is the final well layer 15WL, should be smaller than the peak gain wavelength of the immediately preceding (n-1)th well layer QW(n-1), but larger than that of the first well layer QW(1).

[0074] In other words, the peak gain wavelength of the nth well layer QW(n) should be between the peak gain wavelengths of the first well layer QW(1) and the (n-1)th well layer QW(n-1).

[0075] That is, when the peak gain wavelengths of the n well layers are λp(1), ..., λp(n-1), λp(n), the peak gain wavelengths of the n well layers satisfy the following relationship (1).

[0076] λp(1) < ... < λp(n-1), and λp(1) < λp(n) < λp(n-1) Equation (1) Furthermore, when expressed in terms of energy band gaps, if the energy band gaps of n well layers are Eg(1), ..., Eg(n-1), Eg(n), then the energy band gaps of these n well layers satisfy the following relationship: Equation (2).

[0077] Eg(1) > ... > Eg(n-1), and Eg(1) > Eg(n) > Eg(n-1) Equation (2) This configuration is achieved, as described above, by increasing the growth temperature and raising the hydrogen partial pressure to grow the final barrier layer 15L, thereby reducing the In composition of the final well layer 15WL. In other words, the In composition of the final well layer 15WL, which is the layer immediately preceding it, can be modulated by the growth conditions of the final barrier layer 15L.

[0078] In other words, the energy band gap (inter-quantum level energy) of the final well layer 15WL becomes smaller than the energy band gap of the preceding well layer, thereby suppressing the broadening of the composite gain profile due to the factors mentioned above.

[0079] It should be noted that, instead of following the above method, it is also conceivable to grow the final well layer under growth conditions that reduce the In composition, such as by reducing the supply amount of In raw material. However, this method presents problems in that it is difficult to control the reproducibility of In composition, lattice consistency, etc., due to reasons such as the short growth times of the well layer and barrier layer.

[0080] (4) Evaluation of the vertical cavity surface-emitting laser Figure 6 is a table showing the experimental results of the final barrier layer 15L thickness, the average Al composition of the electron barrier layer 17, and the internal quantum efficiency, which is the injection efficiency into the well layer (QW), for Examples 1 and 2 (EX1 and EX2) of the vertical cavity surface-emitting laser 10 of this embodiment, in comparison with the experimental results of Comparative Examples 1 and 2 (CX1 and CX2).

[0081] In Examples 1 and 2, as described above, the growth temperature was increased by 50°C, and nitrogen (N) was used as the carrier gas. ２ ) with hydrogen (H ２) was added to grow the final barrier layer 15L. On the other hand, in Comparative Examples 1 and 2 (CX1 and CX2), nitrogen (N) was used as the carrier gas without changing the growth temperature. ２ Crystal growth was performed using only ).

[0082] The thickness of the electron barrier layer 17 in Example 1 (EX1) and the electron barrier layers in Comparative Examples 1 and 2 (CX1 and CX2) is 10 nm. In Example 2 (EX2), the electron barrier layer 17 has a two-stage electron barrier layer consisting of a first electron barrier layer 17A and a second electron barrier layer 17B, and the total thickness of the first electron barrier layer 17A and the second electron barrier layer 17B is 10 nm.

[0083] In Comparative Examples 1 and 2 (CX1 and CX2), the Al composition of the electron barrier layer was fixed at 15%, and the thickness of the final barrier layer was set to 40 and 130 nm, respectively. From the results of Comparative Examples 1 to 3 (CX1 to CX3), it was found that as the thickness of the final barrier layer increased, the internal quantum efficiency decreased, which is consistent with theoretical calculations.

[0084] As shown in Figure 6, in Example 1 (EX1), where the thickness of the final barrier layer 15L was 130 nm and the average Al composition of the electron barrier layer 17 (EBL, thickness: 10 nm) was 30%, the internal quantum efficiency was 71%. This is a significant improvement in internal quantum efficiency compared to Comparative Example 1 (CX1), where the thickness of the final barrier layer was 130 nm and the internal quantum efficiency was 40%. Furthermore, in Example 1 (EX1), the internal quantum efficiency was significantly improved compared to Comparative Example 2 (CX2), where the thickness of the final barrier layer was 40 nm.

[0085] Furthermore, in Example 2 (EX2), which has a final barrier layer 15L with a thickness of 130 nm and a two-stage electron barrier layer 17 (EBL, thickness: 58 nm, average Al composition: 30%), an internal quantum efficiency of 75% was obtained, indicating a significant improvement in internal quantum efficiency compared to Comparative Examples 1 and 2. Here, it was found that in the electron barrier layer 17 of Example 2, by making the Al composition ratio of the first electron barrier layer 17A, which is the electron barrier layer on the active layer side, that is, the electron barrier layer on the most active layer side (multiple quantum well layer side) within the electron barrier layer, higher than that of the second electron barrier layer 17B, the electron (carrier) confinement efficiency is increased and the injection efficiency is improved. Also, increasing the Al composition of the electron barrier layer 17 increases the possibility of crystal defects (cracks) occurring. Here, according to Example 2, by maintaining the average Al composition of the electron barrier layer 17 and adopting a two-stage electron barrier layer 17 structure, it is possible to further improve the injection efficiency while preventing cracks. Therefore, it is possible to drive with a low threshold current and improve reliability. Furthermore, it is preferable that the first electron barrier layer is thicker than the second electron barrier layer. This prevents the occurrence of cracks due to interstitial stress between semiconductor layers, even when the Al composition is high.

[0086] Figure 7 shows N as the carrier gas. ２ H ２ Example 1 (EX1) of the vertical-cavity surface-emitting laser 10 with added N as the carrier gas, and ２ This graph shows the temperature characteristics of the vertical-cavity surface-emitting laser of Comparative Example 1 (CX1) using [the specified method].

[0087] The threshold current density of the vertical cavity surface-emitting laser 10 in Example 1 (EX1) is 2.7 kA / cm². ２ Therefore, the threshold current density of the vertical-cavity surface-emitting laser in Comparative Example 1 (CX1) is 4.9 kA / cm². ２ In Example 1 (EX1), the threshold current was significantly reduced compared to Comparative Example 1 (CX1), and the temperature characteristics were greatly improved. This is thought to be due to the increase in peak gain in the vertical-cavity surface-emitting laser 10 of this embodiment, achieved by narrowing the gain profile as described above.

[0088] As described in detail above, this disclosure provides a vertical resonator type light-emitting element having a low threshold current density and high luminous efficiency, and a method for manufacturing a vertical resonator type light-emitting element.

[0089] 10: Vertical-cavity surface-emitting laser 11: Substrate 11B: Underlying GaN layer 12: Semiconductor DBR (first reflector) 13: n-type semiconductor layer (first semiconductor layer) 15: Active layer 15B: Barrier layer 15L: Final barrier layer 15Q: Multiple quantum well layer 15W: Well layer 15WL: Final well layer 17: Electron barrier layer 17A: First electron barrier layer 17B: Second electron barrier layer 18: p-type semiconductor layer (second semiconductor layer) 21: Insulating film 22: Transparent conductive film 24: Spacer layer 25: Dielectric DBR (second reflector) 27: n-electrode 28: p-electrode QW1-QW4: Well layers

Claims

1. The process comprises: forming a first reflector; forming a first semiconductor layer on the first reflector; forming a multiple quantum well layer on the first semiconductor layer, including first to n well layers (where n is an integer of 3 or more); forming a final barrier layer on the nth well layer, which is the final well layer of the multiple quantum well layer; forming an electron barrier layer on the final barrier layer; forming a second semiconductor layer on the electron barrier layer; and forming a second reflector on the second semiconductor layer, wherein the first to n well layers have a composition of In and nitrogen (N ２ The final barrier layer is formed by growing the material with hydrogen (H) as the carrier gas, and the growth temperature is increased and the carrier gas is changed to hydrogen (H) ２ A method for manufacturing a vertical resonator type light-emitting element, which involves adding () and performing growth.

2. The method for manufacturing a vertical resonator type light-emitting element according to claim 1, wherein the step of forming the final barrier layer is to raise the growth temperature within the range of 25 to 200°C.

3. The step of forming the final barrier layer is to ensure that the hydrogen partial pressure is 10% or more and that hydrogen (H ２ A method for manufacturing a vertical resonator type light-emitting element according to claim 1, wherein the carrier gas is added to the above carrier gas.

4. When the peak gain wavelengths of the first to nth well layers are λp(1), ..., λp(n-1), λp(n), the peak gain wavelengths satisfy equation (1): λp(1) < ... < λp(n-1) and λp(1) < λp(n) < λp(n-1). A method for manufacturing a vertical resonator type light-emitting element according to any one of claims 1 to 3.

5. The method for manufacturing a vertical resonator type light-emitting element according to claim 1, wherein the thickness of the final barrier layer is 40 nm or more.

6. The method for manufacturing a vertical resonator type light-emitting element according to claim 1, wherein the vertical resonator type light-emitting element is a nitride surface-emitting laser made of a GaN (gallium nitride) semiconductor.

7. The device comprises: a first reflector; a first semiconductor layer formed on the first reflector; an active layer formed on the first semiconductor layer and comprising a multiple quantum well layer including first to n well layers (where n is an integer of 3 or more) and a final barrier layer formed on the nth well layer which is the final well layer of the multiple quantum well layer; an electron barrier layer formed on the final barrier layer; a second semiconductor layer formed on the electron barrier layer; and a second reflector formed on the second semiconductor layer, wherein the first to n well layers have In in their composition, the nth well layer has a smaller In composition than the (n-1)th well layer, and when the peak gain wavelengths of the first to n well layers are λp(1), ..., λp(n-1), λp(n), the peak gain wavelengths are: A vertical resonator type light-emitting element that satisfies equation (1) λp(1) < ... < λp(n-1) and λp(1) < λp(n) < λp(n-1).

8. The vertical resonator type light-emitting element according to claim 7, wherein the thickness of the final barrier layer is 40 nm or more.

9. The vertical resonator type light-emitting element according to claim 7, wherein the electron barrier layer comprises Al (aluminum), and the electron barrier layer comprises a first electron barrier layer and a second electron barrier layer having a lower Al composition than the first electron barrier layer.

10. The vertical resonator type light-emitting element according to claim 9, wherein the first electron barrier layer is thicker than the second electron barrier layer.

11. The vertical resonator type light-emitting element according to any one of claims 7 to 10, wherein the vertical resonator type light-emitting element is a nitride surface-emitting laser made of a GaN (gallium nitride) semiconductor.

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