Laser device

Abstract

An embodiment discloses a vertical cavity surface emission laser comprising a substrate, a first reflective layer disposed on the substrate, a first light-emitting part disposed on the first reflective layer, a tunnel junction layer disposed on the first light-emitting part, a second light-emitting part disposed on the tunnel junction layer, a first current injection layer disposed on the second light-emitting part, and a second reflective layer disposed on the second light-emitting part.

Description

Technology Field

[0001] The embodiment relates to a vertical cavity surface emission laser. Background Technology

[0002] A Vertical Cavity Surface Emitting Laser (VCSEL) is a type of laser that emits light in a direction perpendicular to the substrate surface.

[0003] Vertical Cavity Surface Emitting Lasers (VCSELs) are the most suitable core components for light sources for ultra-small 3D sensors for the Fourth Industrial Revolution that require high precision, and are being applied to various devices ranging from mobile phones to displays and automotive distance measuring systems (Light Detection and Ranging; LiDAR systems).

[0004] Recently, research is being conducted on a technology to realize ultra-small high-power VCSEL devices by integrating the light-emitting part in the vertical direction in the epitaxial structure during epitaxial structure formation without increasing the size of the vertical cavity surface emission laser (VCSEL). The problem to be solved

[0005] The embodiment can provide a high-power vertical cavity surface emission laser without increasing the device size.

[0006] The embodiment can provide a vertical cavity surface emission laser with improved luminous efficiency.

[0007] The embodiment can provide a vertical cavity surface emission laser capable of reducing leakage current.

[0008] The problems intended to be solved in the embodiments are not limited thereto, and may also include objectives or effects that can be identified from the means of solving the problems or the forms of implementation described below. means of solving the problem

[0009] The vertical cavity surface emission laser element of the present invention comprises a substrate, a first reflective layer disposed on the substrate, a first light-emitting part disposed on the first reflective layer, a tunnel junction layer disposed on the first light-emitting part, a second light-emitting part disposed on the tunnel junction layer, a first current injection layer disposed on the second light-emitting part, and a second reflective layer disposed on the first current injection layer.

[0010] The tunnel junction layer comprises a first tunnel junction layer disposed on the first active layer and a second tunnel junction layer disposed on the first tunnel junction layer, wherein the first tunnel junction layer may be doped with a p-type dopant and the second tunnel junction layer may be doped with an n-type dopant.

[0011] The first light-emitting part may include a first n-type conductive semiconductor layer disposed on a first reflective layer, a first active layer disposed on top of the first n-type conductive semiconductor layer, and a first p-type conductive semiconductor layer disposed on top of the first active layer, and the second light-emitting part may include a second n-type conductive semiconductor layer disposed on a tunnel junction layer, a second active layer disposed on top of the second n-type conductive semiconductor layer, and a second p-type conductive semiconductor layer disposed on top of the second active layer.

[0012] The energy level of the tunnel junction layer may be greater than the emission energy level of the first active layer and the emission energy level of the second active layer.

[0013] The first current injection layer may include a current blocking region formed at the edge and a central current injection region.

[0014] The above current blocking region is an oxidized region in which the aluminum of the first current injection layer is oxidized, and the above current injection region may be an opening region.

[0015] It may include a second current injection layer disposed between the first light-emitting part and the second light-emitting part.

[0016] The diameter of the current injection region of the first current injection layer may be different from the diameter of the current injection region of the second current injection layer.

[0017] The diameter of the current injection region of the first current injection layer may be smaller than the diameter of the current injection region of the second current injection layer.

[0018] The number of well layers of the second active layer may differ from the number of well layers of the first active layer. Effects of the invention

[0019] According to the embodiment, a high-output device can be realized by integrating the active layer in the vertical direction without increasing the device size of the vertical cavity surface emission laser. In addition, leakage current can be reduced, thereby improving luminous efficiency.

[0020] The various and beneficial advantages and effects of the present invention are not limited to those described above and may be more easily understood in the process of explaining specific embodiments of the present invention. Brief explanation of the drawing

[0021] FIG. 1 is a cross-sectional view of a laser element according to a first embodiment of the present invention. FIG. 2 is an energy band diagram of a laser element according to a first embodiment of the present invention. Figure 3 is a graph showing the horizontal diffusion distance of electrons in an InGaAs quantum well layer according to temperature. FIG. 4 is a diagram showing the flow of carriers when current is injected into a laser element according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view of a laser element according to a second embodiment of the present invention. FIG. 6 is an energy band diagram of a laser element according to a second embodiment of the present invention. FIG. 7 is a diagram showing the flow of carriers when current is injected into a laser element according to a second embodiment of the present invention. Figure 8 is a current density table according to the size of the current injection area of ​​the current injection layer. FIG. 9a is a cross-sectional view of a laser element according to a third embodiment of the present invention. FIG. 9b is a cross-sectional view of a laser element according to a fourth embodiment of the present invention. Specific details for implementing the invention

[0022] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated and described in the drawings. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0023] Terms including ordinal numbers, such as second, first, etc., may be used to describe various components, but said components are not limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be named the first component, and similarly, the first component may be named the second component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0024] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0025] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0026] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0027] Hereinafter, embodiments will be described in detail with reference to the attached drawings, provided that identical or corresponding components are given the same reference number regardless of the drawing symbols, and redundant descriptions thereof will be omitted.

[0028] FIG. 1 is a cross-sectional view of a laser element according to a first embodiment of the present invention.

[0029] Referring to FIG. 1, a vertical cavity surface emission laser according to an embodiment comprises a substrate (100), a first reflective layer (200) disposed on the substrate (100), a first emitting part (1000) disposed on the first reflective layer (200), a tunnel junction layer (600) disposed on the first emitting part (1000), a second emitting part (2000) disposed on the tunnel junction layer (600), a first current injection layer (720) disposed on the second emitting part (2000), and a second reflective layer (800) disposed on the first current injection layer (720).

[0030] The substrate (100) may be a semi-insulating or conductive substrate. For example, the substrate (100) is a GaAs substrate with a high doping concentration, wherein the doping concentration is 1×10⁻⁶ 17 cm -3 Up to 1×10 19 cm -3 It may be to that extent. If necessary, a semiconductor buffer layer such as an AlGaAs or GaAs thin film may be further placed on the substrate (100), but is not necessarily limited thereto.

[0031] The first reflective layer (200) may include a distributed Bragg reflector (DBR) with an n-type superlattice structure. The first reflective layer (200) may be epitaxially deposited on a substrate (100) by techniques such as MOCVD and MBE.

[0032] The first reflective layer (200) can perform an internal reflection function in the VCSEL structure. The first reflective layer (200) may be formed by alternately stacking a plurality of first-1 sublayers (not shown) and a plurality of first-2 sublayers (not shown). Both the first-1 sublayers and the first-2 sublayers may be AlGaAs, but the aluminum composition of the first-1 reflective layer may be higher.

[0033] The first-1 sublayer and the first-2 sublayer forming the first reflective layer (200) preferably have an effective optical thickness of about 1 / 4 of the light wavelength generated by the VCSEL, and also, for high internal reflection of the VCSEL, it is preferable to have a reflectivity of about 100% overall if possible.

[0034] The 1-1 sublayer and the 1-2 sublayer may have an effective optical thickness of about 1 / 4 of the optical wavelength generated by the VCSEL (effective optical thickness = target optical wavelength / (4 x refractive index of the material)). In addition, it is desirable to have a reflectance of about 100% for high internal reflection to have good VCSEL characteristics.

[0035] The reflectivity of the first reflective layer (200) may depend on the difference in refractive index between the first-1 sublayer and the first-2 sublayer constituting the interior, and the number of layers of the first-1 sublayer and the first-2 sublayer. Therefore, in order to increase the reflectivity and lower the resistance, it may be better to have a large difference in refractive index between the first-1 sublayer and the first-2 sublayer and a small number of layers.

[0036] In addition, to reduce electrical resistance, an Al-graded AlGaAs layer may be placed between the 1-1 sublayer and the 1-2 sublayer, in which the Al composition ratio of the 1-1 sublayer and the 1-2 sublayer is continuously varied in one dimension or two dimensions.

[0037] A first light-emitting part (1000) disposed on top of a first reflective layer (200) includes a first n-type conductive semiconductor layer (310) disposed on the first reflective layer (200), a first active layer (410) disposed on top of the first n-type conductive semiconductor layer (310), and a first p-type conductive semiconductor layer (510) disposed on top of the first active layer (410).

[0038] The first n-type conductivity semiconductor layer (310) can be implemented as a compound semiconductor such as a III-V group or a II-VI group, and the first dopant can be doped into the first n-type conductivity semiconductor layer (310). The first n-type conductivity semiconductor layer (310) is A x B y C (1-x-y) D z E (1-z) It may be a semiconductor material having the compositional formula (0≤x≤1, 0≤y≤1, 0≤x+y≤1, 0≤z≤1). Here, A, B, and C are one of Al, Ga, and In, and D and E are one of As, P, N, and Sb.

[0039] For example, the first n-type conductive semiconductor layer (310) may be formed from one or more of GaN, InGaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, AlGaInP, InGaAsP, InAlGaAs, InAlGaAsP, and InGaAsSb, but is not limited thereto. The first dopant may be an n-type dopant such as Si, Ge, Sn, Se, Te, etc.

[0040] The first active layer (410) disposed on top of the first n-type conductive semiconductor layer (310) may be composed of one or more quantum well layers and a barrier layer. The quantum well layer may be selected from GaAs, AlGaAs, AlGaAsSb, InAlGaAs, AlInGaP, GaAsP, or InGaAsP, and the barrier layer may be selected from AlGaAs, InAlGaAs, InAlGaAsP, AlGaAsSb, GaAsP, GaInP, AlInGaP, or InGaAsP.

[0041] The first active layer (410) may be designed to provide sufficient optical gain for the laser element. For example, the first active layer (410) according to the embodiment may have a quantum well layer at its center having an appropriate thickness and composition ratio to emit light in the wavelength range of about 800 nm or 900 nm. However, the wavelength range of the laser output by the quantum well layer is not specifically limited.

[0042] A first p-type conductivity semiconductor layer (510) may be disposed on the upper portion of the first active layer (410), and the first p-type conductivity semiconductor layer (510) may be implemented as a compound semiconductor such as a III-V group or a II-VI group, and a second dopant may be doped into the first p-type conductivity semiconductor layer (510). The first p-type conductivity semiconductor layer (510) is A x B y C (1-x-y) D z E (1-z) It can be formed from a semiconductor material having the compositional formula (0≤x≤1, 0≤y≤1, 0≤x+y≤1, 0≤z≤1). Here, A, B, and C are one of Al, Ga, and In, and D and E can be one of As, P, N, and Sb.

[0043] A tunnel junction layer (600) may be disposed on top of the first p-type conductive semiconductor layer (510). The tunnel junction layer (600) is formed in the form of a thin film to facilitate a tunneling effect between the first and second active layers (410, 420). The tunneling effect refers to the ability of carriers to pass through the thin film material with a certain probability when the carrier energy is relatively low and the thickness of the thin film itself is very thin. The tunnel junction layer (600) is formed by combining a first tunnel junction layer (610), which is a P-type semiconductor layer with a high doping concentration, and a second tunnel junction layer (620), which is an N-type semiconductor layer. The thickness of each layer is preferably 5 to 10 nm to ensure smooth tunneling effects, but is not limited thereto. In the embodiment, the tunnel junction layer (600) is exemplified as being composed of the first tunnel junction layer (610) and the second tunnel junction layer (620), but the number of tunnel junction layers (600) is not necessarily limited thereto.

[0044] FIG. 2 is an energy band diagram of a laser element according to a first embodiment of the present invention.

[0045] Referring to FIG. 2, carriers (e.g., electrons) that have moved from the first reflective layer (200) can participate in light emission by falling from the conduction band of the first active layer (410) to the valence band, and then move to the conduction band of the second active layer (420) due to the tunneling effect in the tunnel junction layer (600), and additionally participate in light emission by falling again from the conduction band of the second active layer to the valence band. Due to this tunneling effect, a multi-junction VCSEL device can be driven with the same injection current relative to a specified power demand compared to a single-junction VCSEL device, and a high-output VCSEL device can be realized without increasing the size of the device by forming multiple light-emitting parts vertically.

[0046] Since the high doping concentration semiconductor layer (610, 620) of the tunnel junction layer (600) may have a reduced luminescence effect when the energy bandgap is similar to that of the active layers (410, 420), it may be made of a material that is higher than the energy bandgap of the well layer and barrier layer of the active layers (410, 420) and equal to or lower than the energy bandgap of the reflection layer (800).

[0047] When the active layers (410, 420) are formed of InAlGaAs or AlGaAs, the tunnel junction layer (600) may preferably be formed of GaAs, but is not limited thereto.

[0048] Referring again to FIG. 1, a second light-emitting unit (2000) is disposed on the upper part of the tunnel junction layer (600), and the second light-emitting unit (2000) may be formed of a second n-type conductive semiconductor layer (320), a second active layer (420), and a second p-type conductive semiconductor layer (520). The constituent materials of the second n-type conductive semiconductor layer (320), the second active layer (420), and the second p-type conductive semiconductor layer (520) may be the same as the first n-type conductive semiconductor layer (310), the first active layer (410), and the first p-type conductive semiconductor layer (510), respectively.

[0049] A first current injection layer (720) may be disposed on the second p-type conductivity semiconductor layer (520). The first current injection layer (720) has a relatively high Al composition ratio (Al composition ratio of 80% or more) and A x B y C (1-x-y) D z E (1-z)The semiconductor material may have a compositional formula of (0≤x≤1, 0≤y≤1, 0≤x+y≤1, 0≤z≤1) (wherein A, B, C are one of Al, Ga, In, and D, E are one of As, P, N, Sb). The first current injection layer (720) may be formed of one or more of AlGaN, InAlGaN, AlGaAs, AlAsP, AlGaP, AlGaAsP, AlGaInP, InAlGaAs, InAlGaAsP, and AlInGaAsSb.

[0050] The first current injection layer (720) may have a higher aluminum composition compared to the first and second reflective layers (200, 800) and the first and second active layers (410, 420). The aluminum composition may be 80% to 100%. Therefore, when in contact with water vapor, oxidation may proceed from the side of the first current injection layer (720).

[0051] According to the embodiment, the side of the first current injection layer (720) can be exposed to water vapor to form an unoxidized central region and an oxidized edge region. The edge region undergoes oxidation and may have a higher resistance and a lower refractive index compared to the central region. Thus, the edge region can function as a current shielding region (721), and the central region can function as a current injection region (722).

[0052] However, it is not necessarily limited to this, and the current injection region (722) may be a region in which a hole is formed in the center of the first current injection layer (720). In this case, the region other than where the hole is formed may be oxidized to form a current shielding region (721).

[0053] The second reflective layer (800) may be placed on top of the second light-emitting part (2000). The second reflective layer (800) may include a distributed Bragg reflector (DBR) with a p-type super lattice structure.

[0054] The second reflective layer (800) may include a second-1 sublayer (not shown) and a second-2 sublayer (not shown), and may be AlGaAs, and the aluminum composition of the second-1 sublayer may be higher. The second-1 sublayer and the second-2 sublayer may have an effective optical thickness of about 1 / 4 of the light wavelength generated by the VCSEL.

[0055] The first electrode (not shown) can be electrically connected to the first reflective layer (200). The second electrode (910) can be placed on the second reflective layer (800) and electrically connected to the second reflective layer (800).

[0056] The first electrode and the second electrode may be formed by including at least one of ITO (indium tin oxide), IZO (indium zinc oxide), IZTO (indium zinc tinoxide), IAZO (indium aluminum zinc oxide), IGZO (indium gallium zinc oxide), IGTO (indium gallium tinoxide), AZO (aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zinc oxide), IZON (IZO Nitride), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO), ZnO, IrOx, RuOx, NiO, RuOx / ITO, Ni / IrOx / Au, Ni / AuGe / Au, and Ti / Pt / Au, but are not limited to these materials. For example, the first electrode and the second electrode may be Ni / AuGe / Au and Ti / Pt / Au, but are not limited thereto.

[0057] Figure 3 is a graph showing the carrier diffusion distance of an InGaAs quantum well layer according to temperature.

[0058] Referring to Fig. 3, the horizontal diffusion distance of electrons in the InGaAs quantum well layer at room temperature is approximately 8 μm, which is significantly larger than the diameter of the current injection region of a typical current injection layer of a VCSEL, which is 5 to 15 μm. Carrier diffusion causes lateral current leakage of carriers, and it is important to minimize lateral current leakage caused by carrier diffusion to improve the optical properties of the VCSEL.

[0059] FIG. 4 is a diagram showing the flow of carriers when current is injected into a laser element according to the first embodiment of the present invention.

[0060] Referring to FIG. 4, the first current injection layer (720) has a high aluminum composition, so the energy bandgap within the laser element can be the largest. Therefore, by blocking the flow (CL1) of carriers supplied from the second reflection layer (800) escaping to the side, the probability of electrons and holes recombining within the active layer (410, 420) can be increased.

[0061] The first current injection layer (720) may include an unoxidized central region and an oxidized edge region. The edge region may have higher resistance and a lower refractive index compared to the central region due to oxidation. Therefore, the injected carriers may be blocked by the high-resistance current blocking region (721) and unable to move along the side of the laser element, and may instead bend toward the low-resistance current injection region (722). Thus, the leakage current to the side can be reduced.

[0062] According to the embodiment, the resistance and refractive index are changed by oxidizing the edge region of the first current injection layer (720), but this is not necessarily limited thereto, and various methods can be applied to control the resistance and refractive index of the current injection region (722) and the current blocking region (721) differently. For example, the composition of the central region and the edge region may be controlled differently, or the central region may be removed to form them.

[0063] When there is only one current injection layer on the upper part of the second emitting part (2000) of the laser element, the leakage current due to lateral spreading of carriers in the first active layer (410) may be greater. Due to the lateral spreading of carriers, the carrier concentration per unit volume of the first active layer (410) becomes lower than that of the second active layer (420), and thus the optical coupling efficiency of the first active layer (410) may be lowered.

[0064] FIG. 5 is a cross-sectional view of a laser element according to a second embodiment of the present invention, FIG. 6 is an energy band diagram of a laser element according to a second embodiment of the present invention, and FIG. 7 is a diagram showing the flow of carriers when current is injected into a laser element according to a second embodiment.

[0065] Referring to FIGS. 5, 6 and 7, in addition to the first current injection layer (720) which is disposed on the second p-type conductivity semiconductor of the second light-emitting part (2000), a second current injection layer (710) may be disposed on the first p-type conductivity semiconductor (510) of the first light-emitting part (1000).

[0066] After the carriers that have moved from the first reflective layer (200) participate in light emission in the first active layer (410), they move to the second active layer (420) due to the tunneling effect in the tunnel junction layer (600) and can additionally participate in light emission in the second active layer (420) as well.

[0067] When a current injection layer is placed in each of the first and second light-emitting parts (1000, 2000), the flow of carriers injected from the second reflection layer (800) into the active layer (410, 420) as well as the flow of carriers injected from the first reflection layer (200) (CL2) can be concentrated into a central region, thereby increasing the probability of electrons and holes recombining within the active layer (410, 420).

[0068] FIG. 8 is a current density table according to the size of the current injection area of ​​the current injection layer, and FIG. 9a and 9b are cross-sectional views of a laser element according to the third and fourth embodiments of the present invention.

[0069] Referring to FIGS. 8, 9a, and 9b, the current density within the active layer (410, 420) changes according to the diameter (W1, W2) of the current injection area of ​​the current injection layer; therefore, the diameter (W1, W2) of the current injection area of ​​the current injection layer is preferably 9㎛ to 14㎛, but is not limited thereto.

[0070] The diameters (W1, W2) of the current injection areas of the second current injection layer (710) and the first current injection layer (720) may be formed differently from each other. As shown in FIG. 9a, the diameter (W1) of the current injection area (712) of the second current injection layer (710) may be manufactured to be larger than the diameter (W2) of the current injection area (722) of the first current injection layer (720). Additionally, as shown in FIG. 9b, the diameter (W2) of the current injection area (722) of the first current injection layer (720) may be manufactured to be larger than the diameter (W1) of the current injection area (712) of the second current injection layer (710).

[0071] Since the current density in the active layer (410, 420) varies depending on the diameter (W1, W2) of the current injection area, the number of well layers in the active layer (410, 420) adjacent to each current injection area can be adjusted to equalize the current density of the well layers in each active layer (410, 420), thereby ensuring a constant light output and improving the light efficiency of the VCSEL device. In addition, by making the current density applied to each well layer equal, the degree of degradation of individual well layers can be made uniform, which can be effective in improving the durability of the device.

[0072] Preferably, when the ratio of the diameters (W2:W1) of the current injection area (722) of the upper first current injection layer (720) and the current injection area (712) of the lower second current injection layer (710) is 1:1.1 or greater and less than 1:1.3, the ratio of the number of well layers of each adjacent active layer is 4:3, and when the ratio of the diameters (W2:W1) of the upper and lower current injection areas is 1:1.3 or greater and less than 1.4, it is preferable to set it to 2:1, but is not limited thereto.

[0073] According to the embodiment, the diameter of the current injection region (722) of the first current injection layer (720) may be smaller than the diameter of the current injection region (712) of the second current injection layer (710), and in this case, the number of well layers of the second active layer (420) may be greater than the number of well layers of the first active layer (410). With this configuration, the current density applied to each well layer is made equal, thereby making the degree of degradation of individual well layers uniform and improving the durability of the device.

[0074] Although the invention has been described above with reference to embodiments, this is merely illustrative and does not limit the invention. Those skilled in the art will understand that various modifications and applications not exemplified above are possible within the scope of the essential characteristics of the embodiments. For example, each component specifically shown in the embodiments may be modified and implemented. Furthermore, differences related to such modifications and applications should be interpreted as being included within the scope of the invention as defined in the appended claims. Explanation of the symbols

[0075] 100: Substrate 200: First reflective layer 600: Tunnel Junction Layer 720: First current injection layer 800: Second reflective layer 1000: First light-emitting part 2000: Second light-emitting part

Claims

Claim 1 A substrate; a first reflective layer disposed on the substrate; a first light-emitting part disposed on the first reflective layer; a tunnel junction layer disposed on the first light-emitting part; a second light-emitting part disposed on the tunnel junction layer; a first current injection layer disposed on the second light-emitting part; a second reflective layer disposed on the first current injection layer; A laser element comprising a first light-emitting part and a second current injection layer disposed between the first light-emitting part and the second light-emitting part, wherein the first reflection layer comprises a plurality of first-1 sublayers and a plurality of first-2 sublayers, and the optical thickness of the first-1 sublayer and the first-2 sublayer is disposed to be approximately 1 / 4 of the light wavelength generated from the laser element, and the first and second current injection layers comprise a current blocking region formed by the oxidation of aluminum at the edge and a current injection region which is an opening region in the center, and wherein the diameter of the current injection region of the first current injection layer is disposed differently from the diameter of the current injection region of the second current injection layer. Depending on the difference in diameter between the current injection region of the first current injection layer and the current injection region of the second current injection layer, the number of well layers of the first active layer of the first light-emitting part and the second active layer of the second light-emitting part are different from each other, and the energy level of the tunnel junction layer is greater than the light-emitting energy level of the first active layer and the light-emitting energy level of the second active layer. Claim 2 A laser device according to claim 1, wherein the tunnel junction layer comprises a first tunnel junction layer disposed on the first light-emitting part and a second tunnel junction layer disposed on the first tunnel junction layer, wherein the first tunnel junction layer is doped with a p-type dopant and the second tunnel junction layer is doped with an n-type dopant. Claim 3 A laser device according to claim 1, wherein the first light-emitting part comprises a first n-type conductive semiconductor layer disposed on a first reflective layer, a first active layer disposed on top of the first n-type conductive semiconductor layer, and a first p-type conductive semiconductor layer disposed on top of the first active layer, and the second light-emitting part comprises a second n-type conductive semiconductor layer disposed on a tunnel junction layer, a second active layer disposed on top of the second n-type conductive semiconductor layer, and a second p-type conductive semiconductor layer disposed on top of the second active layer. Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 A laser element according to claim 1, wherein the diameter of the current injection region of the first current injection layer is smaller than the diameter of the current injection region of the second current injection layer. Claim 10 In claim 9, the laser element in which the number of well layers of the second active layer is different from the number of well layers of the first active layer.

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