Semiconductor laser element and light-emitting device

Abstract

According to the semiconductor laser element and the light emitting device, an electron providing layer is inserted between a first cladding layer and a first waveguide layer, the thickness of the electron providing layer is smaller than or equal to 100 nm, and the n-type doping concentration of the electron providing layer is larger than or equal to 3 * 1018 atom / cm < 3 >. The electron concentration is improved through high Si doping, and effective injection of electrons from the n-type layer to the active region is promoted, so that the recombination probability of carriers in the laser active region is effectively increased, and the overall efficiency of the laser is further improved. And meanwhile, the thickness of the electron providing layer is thinned and accurately controlled, so that the negative influence of high Si doping on the photoelectric property of the laser device is reduced as much as possible while the limitation factor is improved, the probability of generating crystal structure defects is reduced, the performance stability of the laser element is ensured, and the purpose of improving the brightness of emergent light is finally achieved.

Description

[0001] This application is a divisional application of the application for invention patent with application number 202411088629.6, application date 2024-08-09, and invention name "Semiconductor Laser Element and Light Emitting Device", filed by the applicant "Xiamen Sanan Optoelectronics Co., Ltd.". TECHNICAL FIELD

[0002] The present application relates to the technical field of semiconductor manufacturing, in particular to a semiconductor laser element and a light emitting device. BACKGROUND

[0003] III-nitride represented by gallium nitride is a direct transition type wide band gap semiconductor material, which has a wide energy band and is an ideal material for making laser elements from ultraviolet light band to green light band. Gallium nitride-based blue-green laser element has the advantages of small size, high integration, high brightness and high resolution. The distribution of light field and the ability of photon confinement are key factors affecting the performance of gallium nitride-based blue-green laser element.

[0004] In laser products, in order to improve the confinement factor and reduce the problem of laser being absorbed in the waveguide layer due to doping, the structure design of laser products is simpler than that of traditional LED epitaxial structure. The waveguide layer of laser product can be used to confine the light field. The doping in the waveguide layer will cause the gain coefficient to decrease. For example, the doping elements may cause uneven distribution of carriers, affecting the injection efficiency and radiation recombination efficiency of carriers, or bring more non-radiative recombination, or introduce too many crystal defects due to high doping, thereby causing SE to decrease, which will have a great negative impact on the photoelectric properties of laser devices.

[0005] Therefore, it is necessary to provide an improved technical solution to overcome the above-mentioned deficiencies in the prior art. SUMMARY

[0006] In view of the defects and deficiencies in the prior art, the purpose of the present application is to provide a semiconductor laser element and a light emitting device to solve one or more of the above problems.

[0007] According to one aspect of the present application, a semiconductor laser element is provided, comprising at least: a semiconductor stack, the semiconductor stack comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence; the first semiconductor layer comprises a first cladding layer and a first waveguide layer stacked in sequence, and the first waveguide layer is located on the side close to the active layer; wherein, the first cladding layer and the first waveguide layer further comprise an electron-providing layer, the thickness of the electron-providing layer is less than or equal to 100 nm, and the n-type doping concentration of the electron-providing layer is greater than or equal to 3x10 18 atom / cm 3 .

[0008] According to an aspect of the present application, the present application also provides a semiconductor laser element, comprising at least: a semiconductor stack comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence; wherein, the first semiconductor layer contains n-type impurities, the n-type impurities form a concentration curve along the growth direction of the semiconductor stack, the concentration curve comprises a first segment, a second segment and a third segment connected in a loop, the first segment corresponds to the region of the first semiconductor layer away from the active layer, and the third segment corresponds to the region of the first semiconductor layer close to the active layer; the first segment has a first concentration, the third segment has a peak concentration, the first concentration is greater than the peak concentration, and the first concentration of the first segment is between 8*10 18 atom / cm 3 1.5*10 19 atom / cm 3 .

[0009] According to an aspect of the present application, the present application also provides a light emitting device, comprising the semiconductor laser element described in the above technical solution.

[0010] Compared with the prior art, the semiconductor laser element and the light emitting device provided by the present application at least have the following beneficial effects: In the technical solution of the present application, an electron-providing layer is inserted between the first cladding layer and the first waveguide layer, the thickness of the electron-providing layer is less than or equal to 100 nm, and the n-type doping concentration of the electron-providing layer is greater than or equal to 3*10 18 atom / cm 3 By high Si doping to improve the electron concentration, the effective injection of electrons from the n-type layer to the active region is promoted, thereby effectively increasing the recombination probability of carriers in the laser active region, and further improving the overall efficiency of the laser. At the same time, the thickness of the electron-providing layer is thinned and accurately controlled to ensure that the confinement factor is improved while the negative impact of high Si doping on the photoelectric performance of the laser device is minimized, the probability of generating crystal structure defects is reduced, and the performance stability of the laser element is ensured.

[0011] In addition, the light emitting device provided by the present application comprises the semiconductor laser element provided by the above technical solution, therefore, the light emitting device also has the above good technical effects. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to make the technical solutions of the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative effort based on these drawings. In the following description, the positional relationship described in the drawings is the direction of the components drawn in the drawings as the reference, unless otherwise specified.

[0013] For convenience or clarity, the thickness and size of each layer shown in the drawings can be exaggerated, omitted or roughly drawn. In addition, the size of the light emitting device does not completely reflect the actual size.

[0014] Figure 1 A cross-sectional structure schematic diagram of a semiconductor laser element according to an embodiment of the present application is shown. Figure 2 A cross-sectional structure schematic diagram of a stress release layer according to an embodiment of the present application is shown. Figure 3 A graph showing the relationship between the element ion intensity and the depth of a semiconductor laser element according to an embodiment of the present application is shown. Figure 4 A partial enlarged schematic diagram of Figure 3 is shown.

[0015] List of reference numerals: DETAILED DESCRIPTION

[0016] The embodiments of the present application will be described in detail by the following specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the description. The present application can also be implemented or applied by different specific embodiments, and each detail in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0017] The composition and dopant of each layer included in the semiconductor laser element of the present application can be analyzed by any suitable method, such as secondary ion mass spectrometer (SIMS). The thickness of each layer included in the semiconductor laser element described in the present application can be analyzed by any suitable method, such as transmission electron microscope (TEM) or scanning electron microscope (SEM), for the depth position of each layer in cooperation with, for example, the SIMS spectrum.

[0018] In the present application, the term "peak shape" refers to a line profile comprising two line segments with slopes of opposite signs to each other, i.e. one line segment has a positive slope and the other line segment has a negative slope. The "peak concentration" refers to the highest concentration value between the two line segments with slopes of opposite signs of the peak shape.

[0019] For the purpose of description, the growth direction of the semiconductor stack is defined as upward, and the opposite direction is defined as downward.

[0020] As shown in Figures 1-2 , the present embodiment provides a semiconductor laser element, which includes at least a substrate 100 and a semiconductor stack above the substrate 100, the semiconductor stack comprising a first semiconductor layer, an active layer 300 and a second semiconductor layer which are sequentially stacked. The first semiconductor layer in the present embodiment is an N-type semiconductor layer, and the second semiconductor layer is a P-type semiconductor layer. The semiconductor laser element is a facet emitting laser element having a light exit facet and a light reflection facet which cross a main surface of the semiconductor layer such as the active layer 300, and the semiconductor stack has a ridge portion of a mesa structure at the top, the ridge portion being formed in a region above a second cladding layer 430 of the second semiconductor layer, and the extension direction of the ridge portion is the propagation direction of the laser light. An insulating layer 600 is provided on the side surface of the ridge and the surface of the second semiconductor layer which is continuous from the side surface of the ridge.

[0021] The substrate 100 has an upper surface and a lower surface, and the lower surface is provided with a first electrode 800 which forms an electrical contact with the first semiconductor layer. In addition, the upper surface of the ridge is provided with a contact electrode 500 which forms an ohmic contact with the second semiconductor layer. The semiconductor laser element further includes a second electrode 700 provided on the upper surface of the contact electrode 500, and the second electrode 700 forms an electrical connection with the contact electrode 500. The first electrode 800 and the second electrode 700 jointly act on the PN junction, and energy is released by the recombination of electrons and holes to generate photons, and the photons are reflected and amplified by the resonant cavity to form a laser beam, thereby realizing the laser emission function of the laser diode.

[0022] Continuing to refer to Figures 1-2 , the substrate 100 can be a growth substrate, including but not limited to a nitride semiconductor, SiC or a high-resistance substrate such as a sapphire substrate. The substrate containing a nitride semiconductor can improve the heat dissipation efficiency due to the higher thermal conductivity than sapphire, thereby reducing defects such as dislocations and achieving good crystallinity. In an optional embodiment, the substrate 100 can be a support substrate, and the growth substrate used to grow the semiconductor stack by epitaxy can be selectively removed according to the needs of the application, and then the semiconductor stack is transferred to the aforementioned support substrate. Further, the thickness of the substrate 100 ranges between 40 μm and 400 μm, for example, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm and 300 μm.

[0023] Continuing to refer to Figures 1-2 , the first semiconductor layer can be configured in a multi-layer structure of nitride semiconductors such as GaN, InGaN, AlGaN, etc. The first semiconductor layer includes a buffer layer 210, a first cladding layer 220, an electron-providing layer 230, a first waveguide layer 240, and a stress release layer 250, which are sequentially stacked on the substrate 100. The first semiconductor layer can also include other layers in addition to the above-mentioned layers, and some of the layers can be omitted.

[0024] In one embodiment, the buffer layer 210 is formed on the substrate 100, and is located between the substrate 100 and the first cladding layer 220. The buffer layer 210 is an n-type material layer made of a III-V nitride semiconductor based on GaN, or an undoped material layer, and the material thereof can be InGaN, which is used to adjust the warping of the substrate to improve the uniformity of the wavelength.

[0025] In one embodiment, the first cladding layer 220 is formed on the buffer layer 210, and is located between the buffer layer 210 and the electron-providing layer 230 or the first waveguide layer 240. The material of the first cladding layer 220 can be AlGaN, and by adjusting the refractive index and thickness of the first cladding layer 220, the restriction of the optical field is achieved, so that the optical field is mainly concentrated between the waveguide layers of the laser to increase the gain, thereby improving the efficiency and performance of the laser. The first cladding layer 220 needs a certain thickness to effectively limit the carriers and prevent electron overflow, and the thickness thereof is usually between 100 nm and 500 nm.

[0026] In one embodiment, the electron-providing layer 230 is formed on the first cladding layer 220, and is located between the first cladding layer 220 and the first waveguide layer 240. The n-type doping concentration of the electron-providing layer 230 is greater than or equal to 3×10 18 atom / cm 3 , so as to effectively increase the electron injection efficiency and improve the recombination efficiency of the carriers in the active layer 300. The thickness of the electron-providing layer 230 is less than or equal to 100 nm, specifically, the thickness of the electron-providing layer 230 is between 10 nm and 100 nm, preferably between 10 nm and 50 nm, and the doping concentration is between 8×10 18 atom / cm 3 ~1.5×10 19 atom / cm 3The n-type impurity doping concentration of the electron-providing layer 230 is generally greater than the n-type impurity doping concentration of the first cladding layer 220. It can be understood that, since the laser will cause the gain coefficient to decrease due to the doping in the waveguide layer, affecting the carrier recombination efficiency, and then affecting the luminous brightness, the insertion of the electron-providing layer 230 can effectively inject electrons from the first cladding layer 220 into the active layer 300, so as to accumulate sufficient non-equilibrium carrier concentration in the well layer of the active layer 300, optimize the number and distribution of carriers in the active layer 300, and improve the quantum efficiency of the laser. In addition, the electron-providing layer 230 can also limit the horizontal diffusion of electrons, reduce electron overflow, reduce non-radiative recombination of carriers, and ensure that they are mainly concentrated in the active region, thereby improving the efficiency of the laser.

[0027] In the above embodiment, the thickness of the electron-providing layer 230 is less than the thickness of the first waveguide layer 240. The relatively thin electron-providing layer 230 can reduce defects caused by crystal growth in the layer, ensure better light confinement capability, and also provide a relatively flat surface as the growth basis for the first waveguide layer 240, which is conducive to improving the crystal quality of the first waveguide layer 240. The thickness of the electron-providing layer 230 is between 10 nm and 30 nm, for example, it can be 10 nm, 15 nm, 20 nm, 25 nm or 30 nm. A layer that is too thick can introduce more defects or stress in the subsequent material deposition process, affecting the reliability and stability of the device, while a layer that is too thin cannot withstand the stress or temperature changes in the subsequent process, resulting in layer structure rupture or failure, and higher requirements for the accuracy of the doping process. Further, the thickness of the electron-providing layer 230 is between 15 nm and 25 nm, for example, 20 nm, to achieve a good balance between the electron-providing capability and the quality of the layer structure.

[0028] In the above embodiment, the electron-providing layer 230 is a GaN material with high Si element doping, and the doping concentration is greater than the doping concentration of the first cladding layer 220 and the first waveguide layer 240. By setting a higher Si doping concentration, the electron concentration is increased to ensure sufficient carrier recombination in the active layer 300. For a relatively thin electron-providing layer 230, the doping concentration of the electron-providing layer 230 is also greater than the peak doping concentration of the Si element in the stress release layer 250. Specifically, the doping peak concentration of the stress release layer 250 is less than or equal to 1.2×10 19 atom / cm 3 , and the doping concentration of the electron-providing layer 230 is between 8×10 18 atom / cm 3 and 1.5×10 19 atom / cm 3The doping concentration of the electron-providing layer 230 is between the doping concentration of the first waveguide layer 240 and the doping concentration of the stress release layer 250, so as to provide sufficient electrons to the quantum well layer for effective recombination. Further, along the growth direction of the semiconductor stack, the Si element in the electron-providing layer 230 is equally doped, and the initial doping concentration at the lower surface to the doping concentration at the upper surface is always kept consistent. The constant doping concentration is beneficial to simplify the preparation process, and also makes the electron concentration in the electron-providing layer 230 stable, thereby improving the performance stability of the semiconductor laser element.

[0029] In the above embodiment, the stress release layer 250 is further included between the first waveguide layer 240 and the active layer 300. The stress release layer 250 includes a first sub-layer 251, a second sub-layer 252 and an intermediate layer 253 between the first sub-layer 251 and the second sub-layer 252, which are sequentially stacked. The intermediate layer contains In component, for example, the stress release layer can be a GaN / InGaN / GaN multilayer structure. The Si element is doped in the stress release layer 250. Along the growth direction of the semiconductor stack, the doping concentration of the Si element is kept constant or gradually doped. The stress release layer 250 has at least one doping peak concentration, which is generated in any sub-layer in the stress release layer 250, for example, the first sub-layer 251, the second sub-layer 252 or the intermediate layer 253.

[0030] Through experiments, under the condition that other semiconductor layer parameters are the same, when the thickness of the electron-providing layer is 100 nm and the doping concentration is 3×10 18 atom / cm 3 , the confinement factor of the laser is improved from 0.71 to 0.74, and the confinement ability of the laser is obviously improved. 18 atom / cm 3 , the confinement factor of the laser is improved from 0.71 to 0.74, and the confinement ability of the laser is obviously improved.

[0031] In one embodiment, the first waveguide layer 240 is formed on the electron-providing layer 230, and is located between the electron-providing layer 230 and the stress-releasing layer 250. The material of the first waveguide layer 240 can be InGaN. By doping different proportions of Al components in the InGaN, the refractive index and band gap of the waveguide layer are adjusted, so that the refractive index of the first waveguide layer 240 is higher than that of the first cladding layer 220. The optical signal can be totally reflected at the interface between the waveguide layer and the cladding layer, so as to be confined in the waveguide layer for propagation, thereby achieving effective optical gain effect. Meanwhile, the electron-providing layer 230 below the first waveguide layer 240 can also play a certain role in reducing electron overflow. The thickness of the first waveguide layer 240 is between 50 nm and 500 nm, so as to balance the electron injection efficiency, the refractive index and the layer structure strength. Further, the thickness of the first waveguide layer 240 is between 200 nm and 400 nm. In an optional embodiment, the In component in the first waveguide layer 240 gradually increases as it approaches the active layer 300, which can more effectively disperse the deformation of the well layer, improve the crystal quality of the active layer 300, and improve the carrier recombination efficiency.

[0032] In the above embodiment, the Si doping concentration of the first waveguide layer 240 is less than the peak doping concentration of the stress-releasing layer 250, and the Si doping concentration of the first waveguide layer 240 is less than the doping concentration of the electron-providing layer 230.

[0033] In one embodiment, the stress-releasing layer 250 is formed on the first waveguide layer 240, and is located between the first waveguide layer 240 and the active layer 300. Part of the stress-releasing layer 250 contains an In component, for example, InGaN. See FIG. 2B. Figure 3The In component forms an ion intensity curve L along the semiconductor stack growth direction. The peak concentration of the ion intensity curve L is less than the maximum concentration of the In component in the first waveguide layer 240, so as to reduce lattice defects caused by lattice constant mismatch. The lattice constant is effectively transferred from the GaN substrate to the InGaN quantum well layer in the active layer 300, which significantly improves the interface flatness of the active layer 300 and provides a better growth environment for the quantum well layer, thereby improving the crystal quality of the active layer 300. The setting of the stress relief layer 250 can also effectively reduce the influence of the polarization field, increase the hole barrier, reduce the overflow probability and improve the carrier recombination efficiency, while reducing the generation of the peak wavelength twin peak phenomenon. By controlling the process parameters such as the material and structure of the stress relief layer 250, the quantum well lattice and polarization field are affected, thereby affecting the effective recombination probability and position of carriers, which can bring good effects on the optoelectronic performance and structural performance of semiconductor lasers. The In content within the In-containing portion of the stress relief layer 250 remains constant, or the In content varies uniformly or gradually from bottom to top within the stress relief layer 250. In an optional embodiment, the thickness of the stress relief layer 250 is between 100 Å and 300 Å, for example, 160 Å, 170 Å, 185 Å, 200 Å, 250 Å, or 280 Å. Excessive thickness affects the efficiency of carrier injection from the first waveguide layer 240 to the active layer 300, causing localized light absorption, a decrease in gain coefficient, and consequently, reduced device brightness; while insufficient thickness fails to provide an effective lattice constant transition and thus inadequate stress relief. Further, the thickness of the stress relief layer 250 is between 180 Å and 190 Å to achieve a more balanced stress relief effect.

[0034] The stress relief layer 250 is doped with Si to reduce the polarization field of the active layer 300, thereby increasing the electron-hole recombination efficiency. The doping concentration is between 5 × 10⁻⁶. 18 atom / cm 3 ~1×10 19 atom / cm 3 Meanwhile, the Si doping concentration of the electron-providing layer 230 is greater than that of the stress-relieving layer 250, and its doping concentration is between 8 × 10⁻⁶. 18 atom / cm 3 ~5×10 19 atom / cm 3 In this configuration, sufficient electron supply is ensured. In an optional embodiment, the Si doping concentration of the electron providing layer 230 is less than or equal to the doping concentration of the stress relief layer 250, and the doping concentration of the electron providing layer 230 is adjusted accordingly based on the crystal quality of the waveguide layer.

[0035] The stress release layer 250 comprises a first sub-layer 251, a second sub-layer 252 and an intermediate layer 253 between the first sub-layer 251 and the second sub-layer 252, the first sub-layer 251 is in contact with the first waveguide layer 240, the second sub-layer 252 is in contact with the active layer 300, the intermediate layer 253 contains In component, and the thickness of the intermediate layer 253 is between 50 Å and 150 Å. In an optional embodiment, the first sub-layer 251 and the second sub-layer 252 comprise GaN, the intermediate layer 253 comprises InGaN, the stress release layer 250 forms a GaN / InGaN / GaN stack structure, that is, the peak concentration of the ion intensity curve L caused by the In component is generated at the intermediate layer 253, and the In ion intensity curve peak concentration of the InGaN material of the intermediate layer 253 is less than the maximum concentration of the In component in the first waveguide layer 240. If the In component content of the intermediate layer 253 is too high, it is easy to cause a double-peak phenomenon, the laser wavelength half-width becomes larger, the gain effect is poor, the electron overflow reduces the recombination efficiency, and the brightness of the laser product is affected. The In component content of the intermediate layer 253 is relatively lower than the In ion peak intensity of the first waveguide layer 240, which can reduce the lattice mismatch and reduce the structural defects, and the lower In component content of the intermediate layer 253 also means that the lattice constant of the layer and the second sub-layer 252 and the first well layer of the active layer 300 is closer, which is more conducive to realizing the stress release effect from the N-type semiconductor layer to the active layer 300. The In component content of the intermediate layer 253 remains constant from bottom to top, or the In component is in a uniform gradient or gradient gradient form in the intermediate layer 253.

[0036] In an embodiment, the intermediate layer 253 can be composed of a GaN / InGaN superlattice structure, and the thickness of the intermediate layer 253 is between 80 Å and 120 Å, or the stress release layer 250 can also be composed of a GaN / InGaN superlattice structure.

[0037] In an embodiment, the thickness of the intermediate layer 253 is greater than the thickness of the first sub-layer 251, the thickness of the intermediate layer 253 is greater than the thickness of the second sub-layer 252, and the thickness of the first sub-layer 251 is less than the thickness of the second sub-layer 252, thereby facilitating the release of stress. Specifically, the thickness of the first sub-layer 251 is between 20 Å and 70 Å, for example, 25 Å, 30 Å, 35 Å, 45 Å, 50 Å or 70 Å. The thickness of the second sub-layer 252 is between 20 Å and 70 Å, for example, 25 Å, 30 Å, 35 Å, 45 Å, 50 Å or 70 Å. The thickness of the intermediate layer 253 is between 80 Å and 120 Å, for example, 80 Å, 90 Å, 100 Å, 110 Å or 120 Å.

[0038] In one embodiment, the active layer 300 is formed on the first semiconductor layer 210, and is located between the stress relief layer 250 and the second waveguide layer 410. The active layer 300 can be a multi-layer structure composed of GaN, InGaN, or other nitride semiconductor. The active layer 300 can have a single quantum well structure or a multiple quantum well structure. The multiple quantum well structure is more likely to achieve sufficient gain than the single quantum well structure. In the case where the active layer 300 includes a multiple quantum well structure, the first and last layers can be either a well layer or a barrier layer if the well layers and barrier layers are alternately stacked. Further, the multiple quantum well structure includes 2 to 3 pairs of alternately arranged potential barrier layers and potential well layers, the thickness of the second sub-layer 252 defining the stress relief layer 250 is H2, and the thickness of the first barrier layer in the active layer 300 close to the stress relief layer 250 is Ll, where 0.8≤H2 / Ll≤1.2. That is, the thickness of the second sub-layer 252 is similar to the thickness of the first barrier layer, and the doping elements are similar. The second sub-layer 252 is inserted between the intermediate layer 253 and the active layer 300 in the form of a pre-potential barrier layer, so as to play a role of stress relief between the active layer 300 and the first semiconductor layer. As an example, the thickness of the first barrier layer can be 40Å, 45Å, or 50Å, and the thickness of the second sub-layer 252 can also be 40Å, 45Å, or 50Å. The thickness of the first sub-layer 251 is less than the thickness of the second sub-layer 252 and the first barrier layer, for example, can be 25Å, 30Å, or 35Å. In an optional embodiment, the thickness of each barrier layer in the active layer 300 can be the same or different, and the thickness of each well layer can also be the same or different.

[0039] Further, for the semiconductor laser element emitting blue-green light, the active layer 300 in contact with the stress relief layer 250 is a first well layer, and a first barrier layer, a second well layer, and a second barrier layer are sequentially stacked upward from the first well layer. The potential well layer includes In x Al y Ga 1-x-y N (0 < x < 1, 0≤y<1, 0 < x + y < 1), and more preferably InGaN. The emission wavelength of the laser element can be controlled by adjusting the In content of the well layer, so that the laser element emits blue light or green light. The emission wavelength ranges from 430 nm to 550 nm.

[0040] Further, for the semiconductor laser element emitting blue-green light, the active layer 300 in contact with the stress relief layer 250 is a first well layer, and a first barrier layer, a second well layer, and a second barrier layer are sequentially stacked upward from the first well layer. The potential well layer includes In x Al y Ga 1-x-yN (0 < x < 1, 0 ≤ y < 1, 0 < x + y < 1), more preferably InGaN, the light-emitting wavelength of the laser element can be controlled by adjusting the In content of the well layer, so that it emits purple light, and the light-emitting wavelength ranges from 370 nm to 450 nm.

[0041] In one embodiment, a second semiconductor layer is formed on the active layer 300, which is a P-type semiconductor layer, and can be formed using a single layer or a multi-layer structure formed of a nitride semiconductor layer. As the p-type nitride semiconductor layer contained in the second semiconductor layer, a layer formed of a nitride semiconductor containing a p-type impurity such as Mg can be given. The second semiconductor layer includes a second waveguide layer 410, an electron blocking layer 420, a second cladding layer 430, and an ohmic contact layer 440, which are sequentially stacked. The second semiconductor layer can also include other layers in addition to the above-mentioned layers, and some of the layers can be omitted.

[0042] In one embodiment, a second waveguide layer 410 is formed on the active layer 300, and the material thereof can be InGaN. The addition of In component can buffer the deformation of the well layer, and the maximum content of In component in the second waveguide layer 410 is greater than the peak intensity of the In component ion intensity curve L in the stress release layer 250, so as to achieve a good transition of the lattice constant of the active layer 300 to the second semiconductor layer. The thickness of the second waveguide layer 410 is similar to that of the first waveguide layer 240, and is between 50 nm and 500 nm, so as to achieve a balance between the carrier injection efficiency, the refractive index, and the layer structure strength. Further, the thickness of the second waveguide layer 410 is between 100 nm and 300 nm. In an optional embodiment, the In component in the second waveguide layer 410 gradually increases as it approaches the active layer 300, which can more effectively disperse the deformation of the well layer, improve the crystal quality of the active layer 300, and improve the carrier recombination efficiency.

[0043] In one embodiment, an electron blocking layer 420 is formed on the second waveguide layer 410, and the material thereof can be a wide-bandgap material such as AlN or AlGaN, so as to effectively block the leakage of electrons from the second semiconductor layer to the active layer 300, while allowing holes to pass through. The second waveguide layer 410 and the electron blocking layer 420 work together in the laser to jointly achieve the confinement of the optical field and the carriers, which helps to more effectively recombine the electrons and holes in the active region, thereby improving the light-emitting efficiency.

[0044] In one embodiment, a second cladding layer 430 is formed on the electron blocking layer 420, which can be a wide bandgap material such as AlGaN, and the second cladding layer 430 limits the propagation of light within the waveguide layer by providing a lower refractive index than the second waveguide layer 410. The thickness of the second cladding layer 430 is between 100 nm and 500 nm to effectively limit the diffusion of carriers while not being too thick to increase the series resistance too much.

[0045] In one embodiment, an ohmic contact layer 440 is formed on the second cladding layer 430, which can be GaN or InGaN, and matches the lattice constant of the second cladding layer 430 and can increase the conductivity by high doping to reduce the resistance of the contact with the metal electrode, form a good ohmic contact, and promote uniform injection of current.

[0046] In one embodiment of the present application, the semiconductor laser element can form a ridge by etching part of the second semiconductor layer. The width of the ridge is adjusted to be between 1 μm and 5 μm. A contact electrode 500 is provided on the upper surface of the ridge. Specifically, the main role of the contact electrode 500 is to increase the lateral expansion capability and expand the area of the current action, and the material of the contact electrode 500 can be a transparent conductive film such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), gallium oxide (GaO3), and the like, and the material of the contact electrode 500 can also be a metal such as nickel, gold, and the like. The contact electrode 500 is a transparent conductive film having a smaller refractive index than the active layer 300. Further, an insulating layer 600 is formed on the side surface of the exposed ridge, the side surface of the contact electrode 500, and the surface of the second cladding layer 430 exposed by etching. The film thickness of the insulating layer 600 is between 100 nm and 500 nm, and it can be formed of a single layer or a multilayer of a material such as an oxide or a nitride of Si, Al, Zr, Ti, Nb, Ta, and the like.

[0047] In one embodiment, a second electrode 700 is formed on the ridge and contacts the contact electrode 500 to electrically connect with the second semiconductor layer. The thickness of the second electrode 700 is between 0.1 μm and 2 μm, and it is generally a thickness that functions as an electrode of a semiconductor laser element, and the material can be a metal or an alloy such as Ni, Rh, Cr, Au, W, Pt, Ti, Al, and the like.

[0048] In one embodiment, a first electrode 800 is provided on the lower surface of the substrate 100 and electrically connects with the first semiconductor layer. The material of the first electrode 800 includes any one or a combination of two or more of Ni, Ti, Pd, Pt, Au, Al, TiN, ITO, IGZO, and the like, but is not limited thereto.

[0049] As Figures 3-4The diagram shows the relationship between elemental concentration or ion intensity and depth for a portion of a semiconductor laser element provided in an embodiment of this application. This relationship can be obtained using a secondary ion mass spectrometer.

[0050] from Figure 3 It can be seen that the In component has an ion intensity curve L along the semiconductor stack growth direction. The ion intensity curve L includes a first part S1, a second part S2, a third part S3, and a fourth part S4 connected in sequence. Among them, the In component ion intensity of the first part S1 gradually increases in the semiconductor growth direction and reaches the maximum value at the connection with the second part S2. The second part S2 includes a first trough T1, a second trough T2, and an intermediate segment T3 located between the first trough T1 and the second trough T2. The ion intensity of the intermediate segment T3 is greater than the ion intensity of the first trough T1 and the second trough T2. The first trough T1 is connected to the first part S1, and the second trough T2 is connected to the third part S3. The In component ion intensity of the third part S3 has two significant peaks. The In component ion intensity of the fourth part S4 is at its maximum value at the initial intensity at the connection with the third part S3 and gradually decreases along the semiconductor growth direction.

[0051] In the above embodiment, the In component ion intensity of the second part S2 is less than the maximum In component ion intensity of the first part S1, and the In component ion intensity of the middle section T3 is less than the maximum ion intensity of the fourth part S4, to avoid carrier overflow caused by excessive In component content in the middle section. Specifically, for the second part S2, the In ion intensity of the middle section T3 is greater than the In ion intensity of the first trough T1 and the second trough T2. The semiconductor material corresponding to the middle section T3 can be, for example, InGaN, while the two troughs contain a small amount of In component or no In component. The semiconductor material corresponding to the two troughs can be, for example, GaN. It can be understood that the signal duration of the In component ion intensity corresponds to different semiconductor layer thicknesses to some extent. The layer thickness of the first part S1 is greater than the layer thickness corresponding to the second part S2; for the second part S2, the layer thickness of the middle section T3 is greater than the layer thickness corresponding to the first trough T1, and also greater than the layer thickness corresponding to the second trough T1.

[0052] In this embodiment, the first waveguide layer 240 corresponds to Figure 1 The first part S1 of the ion intensity curve L is shown. The stress relief layer 250 corresponds to the second part S2 of the ion intensity curve L. The active layer 300 corresponds to the third part S3 of the ion intensity curve L. The second waveguide layer 410 corresponds to the fourth part S4 of the ion intensity curve L.

[0053] In one embodiment, the In component ion intensity of the stress release layer 250 is less than the maximum In ion intensity of the first waveguide layer 240 and the second waveguide layer 410, reducing lattice mismatch and lowering structural defects. A lower In component content also means that the lattice constant of the layer is closer to that of the first well layer of the active layer 300, which is more conducive to achieving a stress release effect from the N-type semiconductor layer to the active layer 300. The thickness of the first waveguide layer 240 corresponding to the first portion S1 is between 50 nm and 500 nm, in order to achieve a balance between electron injection efficiency, refractive index, and layer structure strength. Further, the thickness of the first waveguide layer 240 is between 200 nm and 400 nm.

[0054] In one embodiment, the In content of the stress release layer 250 corresponding to the second portion S2 is between 1:8 and 1:4 of the maximum In content of the first waveguide layer 240 or the second waveguide layer 410. The In content percentage of the first waveguide layer 240 and the second waveguide layer 410 is between 4% and 8%, and the In content percentage of the stress release layer 250 corresponding to the second portion S2 is between 0.5% and 2%. Further, the In content percentage of the stress release layer 250 is about 1%, and the In content in the stress release layer 250 fluctuates within a range of 20% around 1%, which is preferable. The lattice constant of the stress release layer 250 is between the first well layer in the active layer 300 and the substrate 100, achieving effective lattice transition and good lattice matching, so that interlayer stress is released, surface pits in the active layer 300 are reduced, interface flatness is improved, the crystal growth quality of the active layer 300 is improved, and the negative impact of the polarization field on carrier recombination efficiency is reduced.

[0055] Through experiments, under the same conditions of other semiconductor layer parameters, when the In content percentage in the active layer is 10% and the maximum In content percentage of the first waveguide layer 240 and the second waveguide layer 410 is within the range of 4% to 8%, the light confinement ability of the sample with an In content of 8% in the stress release layer 250 is basically the same as that of the product provided in the present embodiment with an In content of 1% in the stress release layer 250. However, the active layer of the product with an In content of 1% has better quality and the crystal surface grows more smoothly, so that the light brightness of the product is improved.

[0056] In optional embodiments, the semiconductor layer corresponding to the middle section T3 of the second section S2 is InGaN, and the semiconductor layers corresponding to the first and second troughs T1 and T2 are GaN, that is, the In ion intensity curve of the second section S2 is formed by a three-layer stack structure of GaN / InGaN / GaN. Specifically, the middle section T3 corresponds to the middle layer 253 in the stress release layer 250, and the first and second troughs T1 and T2 correspond to the first and second sub-layers 251 and 252 in the stress release layer 250, respectively. The thickness of the first sub-layer 251 is between 20 Å and 70 Å, preferably between 20 Å and 50 Å, the thickness of the second sub-layer 252 is between 20 Å and 70 Å, preferably between 20 Å and 50 Å, the thickness of the middle layer 253 is between 50 Å and 150 Å, preferably between 80 Å and 120 Å, and the overall thickness of the stress release layer 250 corresponding to the second section S2 is between 100 Å and 300 Å, preferably between 180 Å and 190 Å, so as to achieve a more balanced stress release effect. In optional embodiments, the middle layer 253 can be composed of a superlattice structure of GaN / InGaN, or the stress release layer 250 can also be composed of a superlattice structure of GaN / InGaN, which will not be described here.

[0057] Further, the In content percentage in the semiconductor layer corresponding to the third section S3, that is, the quantum well layer, is between 10% and 15%. The In content in the stress release layer 250 should not be too high. When a higher content of In component is doped, for example, more than 2%, the stress release layer 250 to a certain extent plays a similar role as the well layer in the active layer 300, which easily causes the overflow and composite position offset of the carriers. The carriers originally combined in the well layer are offset towards the stress release layer 250, causing the problem of double or multiple peaks, the half-width of the laser wavelength becomes larger, the light shape becomes wider, and the light brightness of the active layer 300 is lost. Similarly, the In content in the stress release layer 250 should not be too low, for example, less than 0.5%, which cannot play a good role in reducing the lattice mismatch degree, and cannot effectively improve the surface flatness of the active layer 300.

[0058] It can be understood that for semiconductor lasers of other wavelengths, the emission wavelength can be adjusted by adjusting the In content in the active layer 300, so as to realize light emission of different colors. Taking a green semiconductor laser element as an example, the green wavelength is greater than the blue wavelength, and the In content in the active layer 300 thereof is also relatively high. In order to confine the light between the waveguide layers, the difference between the refractive indices of the waveguide layers and the cladding layers should also be large, and therefore the In content in the waveguide layers is also relatively high compared with the blue element, and the In content of the stress release layer of the green element is also relatively high, so as to effectively realize the lattice constant matching between the first semiconductor layer and the active layer 300. For the green semiconductor laser, the In ion intensity in the stress release layer 250 is also less than the In component content in the first waveguide layer 240 and the second waveguide layer 410. Further, the stress release layer structure of the green semiconductor laser can also include a first sub-layer 251, a second sub-layer 252 and an intermediate layer 253 located between the first sub-layer 251 and the second sub-layer 252, which are sequentially stacked. Similarities with the structure and parameters of the above-mentioned blue semiconductor laser will not be described again.

[0059] Continuing to refer to Figures 3-4 It can be seen that the Si element has a concentration curve n along the growth direction of the semiconductor stack, the concentration curve n including a first segment D1, a second segment D2 and a third segment D3 connected in sequence; wherein the first segment D1 corresponds to a region of the first semiconductor layer away from the active layer 300, the third segment D3 corresponds to a region of the first semiconductor layer close to the active layer 300, the concentration value of the second segment D2 is lower than that of the first segment D1, the Si element has a peak concentration at the third segment D3, and the concentration of the first segment D1 is greater than the peak concentration. The first segment D1 has a first concentration, the second segment D2 has a second concentration, and the third segment D3 has a peak concentration. The first concentration of the first segment D1 is greater than the peak concentration of the third segment D3, and the first concentration is between 8x10 18 atom / cm 3 ~1.5x10 19 atom / cm 3 , so as to effectively increase the electron injection efficiency and improve the quantum efficiency of the laser.

[0060] In one embodiment, the peak concentration of the third segment D3 is less than or equal to 1.2x10 19 atom / cm 3The third section D3 is a semiconductor layer close to the active layer 300, and the peak concentration thereof is defined to avoid defects caused by too high doping concentration, and to reduce the polarization field in the stress release layer 250. It can be understood that the third section D3 can have more than one peak concentration by optimizing the distribution of Si element, so as to optimize the performance of the semiconductor laser element. In an optional embodiment, when the third section D3 corresponds to a plurality of stacked structures of different material compositions, such as a GaN / InGaN / GaN multilayer structure, the doping peak concentration can be generated in any semiconductor sublayer corresponding to the third section D3, and the first concentration of the first section D1 is greater than the highest peak concentration of the third section D3.

[0061] In the embodiment, the electron supply layer 230 corresponds to the first section D1 of the concentration curve n, the first waveguide layer 240 corresponds to the second section D2 of the concentration curve n, and the stress release layer 250 corresponds to the third section D3 of the concentration curve n. Figure 2 The first section D1 of the concentration curve n corresponds to the electron supply layer 230, the second section D2 of the concentration curve n corresponds to the first waveguide layer 240, and the third section D3 of the concentration curve n corresponds to the stress release layer 250.

[0062] In the above embodiment, the first section D1 can be an AlGaN material with high Si element doping, and the concentration thereof is greater than 3×10 18 atom / cm 3 , and specifically, the doping concentration is between 3×10 18 atom / cm 3 ~1.5×10 19 atom / cm 3 . By inserting the high-doped first section D1 before the second section D2, sufficient electron concentration is provided, the electron-hole recombination efficiency is improved, and the luminous brightness is improved. Further, the doping concentration of the first section D1 is between 1×10 19 atom / cm 3 ~1.2×10 19 atom / cm 3 . The concentration of the second section D2 is between 5×10 17 atom / cm 3 ~5×10 18 atom / cm 3 , and the peak concentration of the third section D3 is between 1×10 18 atom / cm 3 ~5×10 19 atom / cm 3 , but less than the doping concentration of the first section D1. The stress release layer 250 corresponding to the third section D3 is relatively high-doped, so as to reduce the influence of the polarization field on the carrier recombination efficiency in the active layer 300. Further, the peak concentration of the third section D3 is less than or equal to 1.2×10 19 atom / cm 3 .

[0063] In one embodiment, the third section D3, i.e. the stress release layer 250, is doped relatively high to inhibit the polarization field to improve the carrier recombination efficiency, for example, doped with Si, but the high-doped semiconductor layer will cause serious light absorption, reduce the gain effect, and result in the performance degradation of the semiconductor laser element, therefore the thickness of the stress release layer 250 should not be too large. It can be understood that the Si concentration signal duration corresponds to the thickness of the different semiconductor layers to a certain extent, and the thickness of the third section D3, i.e. the stress release layer 250, is preferably 150 Å ~ 250 Å, and further, the thickness of the stress release layer 250 is between 80 Å ~ 120 Å.

[0064] In the above embodiment, the Si concentration of the first section D1, i.e. the electron-providing layer 230, is greater than the peak concentration in the third section D3, i.e. the stress release layer 250, and along the growth direction of the semiconductor stack, the Si element is uniformly doped, and the initial doping concentration at the lower surface to the doping concentration at the upper surface is always consistent, and the constant doping concentration is beneficial to simplify the preparation process, and also makes the electron concentration in the electron-providing layer 230 stable, which can improve the performance stability of the semiconductor laser element. The insertion of the electron-providing layer 230 can optimize the number and distribution of carriers in the active layer 300, and improve the quantum efficiency of the laser, and the doping concentration in the layer is between 8 × 10 18 atom / cm 3 ~ 1.5 × 10 19 atom / cm 3 , to provide sufficient electrons to the quantum well layer for effective recombination. In an optional embodiment, the doping concentration of the first section D1 can also be uniform gradient doping or gradient gradient doping.

[0065] In one embodiment, the thickness of the electron-providing layer 230 is less than the thickness of the first waveguide layer 240, and the relatively thin electron-providing layer 230 can reduce the defects generated by the crystal growth in the layer, ensure a high gain coefficient, and also provide a relatively flat surface as the growth basis of the first waveguide layer 240, which is beneficial to improve the crystal quality of the first waveguide layer 240, and the thickness of the electron-providing layer 230 is 10 nm ~ 50 nm. Further, the thickness of the electron-providing layer 230 is between 15 nm ~ 25 nm, for example, 20 nm, to achieve a good balance between the electron-providing capability and the layer structure quality.

[0066] The present embodiment also provides a light emitting device, which comprises the semiconductor laser element of any one of the above embodiments, and therefore the light emitting device also has the above excellent effects.

[0067] In summary, the semiconductor laser element and the light emitting device provided by the present application effectively overcome the various shortcomings in the prior art and have a high industrial utilization value.

[0068] The above embodiments are only illustrative of the principles of the present application and its effects, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A semiconductor laser element, characterized by comprising: At least comprising: A semiconductor stack, comprising a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially stacked; the first semiconductor layer comprises a first cladding layer and a first waveguide layer which are sequentially stacked, the first waveguide layer is located on the side close to the active layer; wherein, The first cladding layer and the first waveguide layer further comprise an electron-providing layer; the thickness of the first waveguide layer is between 50 nm and 500 nm, and the thickness of the electron-providing layer is less than the thickness of the first waveguide layer; the n-type doping concentration of the electron-providing layer is greater than or equal to 3×10 18 atom / cm 3 , and greater than the doping concentration of the first waveguide layer.

2. The semiconductor laser device according to claim 1, characterized by The doping concentration of the electron-providing layer is between 8 x 1018 18 atom / cm 3 ~1.5 x 1018 19 atom / cm 3 .

3. The semiconductor laser device according to claim 1, wherein The electron-providing layer contains GaN, and the doping concentration in the electron-providing layer is greater than the doping concentration of the first cladding layer.

4. The semiconductor laser device according to claim 1, wherein The thickness of the electron-providing layer is between 10 nm and 100 nm.

5. The semiconductor laser device according to claim 1, wherein The first waveguide layer and the active layer further comprise a stress release layer, the stress release layer has a peak concentration of n-type doping, and the n-type doping concentration of the electron-providing layer is greater than the peak concentration of the stress release layer.

6. The semiconductor laser device according to claim 5, wherein The stress release layer comprises a first sub-layer, a second sub-layer and an intermediate layer between the first sub-layer and the second sub-layer, the intermediate layer contains In component; along the growth direction of the semiconductor stack, the peak concentration of n-type doping of the stress release layer is generated in any sub-layer in the stress release layer.

7. The semiconductor laser device according to claim 1, wherein Along the thickness growth direction of the semiconductor stack, the doping concentration of the electron-providing layer remains constant.

8. A semiconductor laser device, characterized by comprising: At least comprising: A semiconductor stack, comprising a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially stacked; wherein, The first semiconductor layer contains n-type impurities, the n-type impurities form a concentration curve along the growth direction of the semiconductor stack, the concentration curve comprises a first segment, a second segment and a third segment which are sequentially connected, the first segment corresponds to the region of the first semiconductor layer away from the active layer, and the third segment corresponds to the region of the first semiconductor layer close to the active layer; The first concentration of the first section is greater than a second concentration of the second section, and the first concentration of the first section is between 8 x 1010atoms / cm2and 2 x 1011atoms / cm2. 18 atoms / cm2 3 atoms / cm2 19 atoms / cm2 3 .

9. The semiconductor laser device according to claim 8, wherein the peak concentration of the third segment is less than or equal to 1.2 x 10 19 atoms / cm 3 .

10. The semiconductor laser device according to claim 8, wherein The third segment has a peak concentration, and the peak concentration is greater than the second concentration of the second segment.

11. The semiconductor laser device according to claim 8, wherein Along the thickness growth direction of the semiconductor stack, the first concentration of the first segment remains constant.

12. The semiconductor laser device according to claim 1 or 8, wherein The n-type impurities of the first semiconductor layer are Si elements.

13. The semiconductor laser device according to claim 1 or 8, wherein The active layer is a multiple quantum well structure, the multiple quantum well structure comprises 2-3 pairs of alternately arranged barrier layers and well layers, the well layer contains In x Al y Ga 1-x-y N (0 < x < 1, 0 ≤ y < 1, 0 < x + y < 1).

14. A light-emitting device, characterized in that, The light emitting device comprises the semiconductor laser element according to any one of claims 1 to 13.

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