A semiconductor light emitting device and a preparation method thereof, and an electronic product

Abstract

The application discloses a semiconductor light-emitting device and a preparation method thereof and an electronic product. The epitaxial structure of the semiconductor light-emitting device comprises, from bottom to top, an n-type DBR, an active layer and a p-type DBR. The reflectivity of the p-type DBR is higher than that of the n-type DBR, and the p-type DBR comprises a first part grown first and a second part grown later. The first part is provided with a first cap layer at the last layer. The application can realize intermediate detection in the growth process to accurately confirm the resonant wavelength, thereby improving the wavelength yield of products, and provides a reliable manufacturing scheme for the n-side light-emitting semiconductor light-emitting device.

Description

Technical Field

[0001] This invention belongs to the technical field of semiconductors, specifically relating to a semiconductor light-emitting device and its preparation method, as well as electronic products. Background Technology

[0002] Semiconductor light-emitting devices, such as resonant cavity light-emitting diodes (RCLEDs), form a resonant cavity by placing distributed Bragg reflectors (DBRs) on both sides of the active layer of a multiple quantum well (MQW). Unlike VCSELs, RCLEDs do not require reaching the lasing threshold and have better tolerance to temperature variations and driving current fluctuations; however, compared to ordinary LEDs, their light intensity, light extraction efficiency, and spectral linewidth are significantly improved. This makes RCLEDs particularly suitable for applications requiring high spectral width and directionality, such as plastic fiber optic communication, visible light wireless communication, high-resolution displays, and military sights.

[0003] Existing RCLED designs mostly employ p-side emission, with p-side electrodes typically positioned around the emitter aperture. To increase emission power, the emitting area needs to be increased. However, as the emitting area increases, the spacing between the p-side electrodes also increases. Due to the low hole carrier mobility, the injected carriers in the MQW are non-uniform, leading to reduced luminous efficiency. To address this carrier non-uniformity issue, the p-side electrodes are usually improved by adding multiple electrode structures, such as... Figure 1a As shown, the p-electrode 5 has several parallel and connected strip electrodes 51 on the light-emitting aperture. However, this results in a high power density in and around the area where the strip electrodes 51 are located. As the distance from the strip electrodes 51 increases, the power density decreases, eventually reaching its lowest point in the middle region between the two strip electrodes 51. Overall, it exhibits a non-uniform power distribution with multiple peaks and valleys, as shown in the figure. Figure 1b As shown; in addition, these additional electrode strips are still located above the light-emitting holes, which block the light emitted by the active layer to a certain extent, limiting the improvement of output light power. This makes RCLED face a performance bottleneck in large-area, high-power applications. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a semiconductor light-emitting device, its fabrication method, and electronic products, thereby achieving a more uniform power distribution and higher luminous efficiency, and improving the wavelength yield of epitaxial structures.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A semiconductor light-emitting device includes an epitaxial structure comprising an n-type digital light-emitting diode (DBR), an active layer, and a p-type DBR stacked vertically from bottom to top, wherein the reflectivity of the p-type DBR is higher than that of the n-type DBR; the p-type DBR has a first portion grown first and a second portion grown later, the second portion being located above the first portion, and a first cap layer is provided at the junction of the first portion and the second portion, the optical thickness of the first cap layer being 1 / 16 λ0 to 3 / 16 λ0, where λ0 is the target emission wavelength of the semiconductor light-emitting device; the total logarithm of the p-type DBR is A, the logarithm of the first portion is B, and 0.1 ≤ B / A ≤ 0.5.

[0007] Optionally, the reflectivity of the n-type DBR is 50% to 70%, the total reflectivity of the p-type DBR is greater than 98%, and the reflectivity of the first part is 50% to 90%.

[0008] Optionally, the n-type DBR has 5 to 7 pairs; the first part of the p-type DBR has 5 to 15 pairs, and the second part has 25 to 35 pairs.

[0009] Optionally, the thickness of the first cap layer is 10~30 nm.

[0010] Optionally, the first part and the second part respectively include alternating low refractive index layers and high refractive index layers, the refractive index of the first cap layer is higher than the refractive index of the low refractive index layer; the first cap layer is disposed on the low refractive index layer, the second part starts as the bottom high refractive index layer, and the sum of the optical thicknesses of the first cap layer and the bottom high refractive index layer is C×1 / 4 λ0, where the value of C ranges from 0.95 to 1.05.

[0011] Optionally, the material system of the low-refractive-index layer / high-refractive-index layer is Al. x Ga 1-x As / Al y Ga 1-y As, where 0.7 ≤ x < 1, 0 < y ≤ 0.2; the material of the first cap layer is GaAs or In. z Ga 1-z P, where 0.45 ≤ z ≤ 0.55;

[0012] Alternatively, the material system of the low refractive index layer / high refractive index layer is AlInAs / GaInAs, and the material of the first cap layer is GaInAs;

[0013] Alternatively, the material system of the low refractive index layer / high refractive index layer is AlInN / GaN, and the material of the first cap layer is GaN.

[0014] Optionally, it further includes an n-electrode and a p-electrode, wherein the p-electrode is located above the epitaxial structure and the n-electrode is located below the epitaxial structure; the n-electrode has an opening to form a light-emitting aperture, and the area of ​​the light-emitting aperture is 0.9~0.95 times the area of ​​the semiconductor light-emitting device; the projection of the p-electrode on the horizontal plane covers the projection of the light-emitting aperture on the horizontal plane.

[0015] The horizontal plane mentioned here refers to a plane perpendicular to the vertical direction, and the projection is an orthographic projection.

[0016] Optionally, the epitaxial structure further includes a limiting aperture layer having limiting apertures for laterally limiting current and optical field; the projection of the limiting aperture on the horizontal plane is located within the projection of the light-emitting aperture on the horizontal plane.

[0017] Optionally, the aperture of the limiting hole is 200~500 μm, and the ratio of the aperture of the light-emitting hole to the aperture of the limiting hole is 1.02~1.15:1.

[0018] Optionally, it also includes a conductive substrate disposed between the n-type DBR and the n-electrode, wherein the bandgap of the conductive substrate material is greater than the photon energy corresponding to the emission wavelength of the semiconductor light-emitting device.

[0019] Optionally, it also includes an n-type contact layer disposed between the n-type DBR and the n-electrode.

[0020] A semiconductor light-emitting device includes an n-type diode-driven light-emitting diode (DBR), a p-type diode-driven light-emitting diode (DBR), and an active layer sandwiched between the n-type DBR and the p-type DBR; the p-type DBR includes a plurality of pairs of first DBRs and a pair of second DBRs located between the plurality of pairs of first DBRs, wherein the first DBRs are composed of a low-refractive-index layer and a high-refractive-index layer, and the second DBRs are composed of a first layer, a second layer, and a third layer stacked sequentially; wherein...

[0021] The first layer is made of the same material as the low-refractive-index layer, and its optical thickness is 0.237λ0~0.2625λ0.

[0022] The third layer is made of the same material as the high refractive index layer, and the refractive index of the second layer is higher than that of the third layer;

[0023] The optical thickness of the second layer is 1 / 16 λ0 to 3 / 16 λ0, and the sum of the optical thicknesses of the second and third layers is 0.237λ0 to 0.2625λ0; where λ0 is the target emission wavelength of the semiconductor light-emitting device.

[0024] An electronic product comprising the aforementioned semiconductor light-emitting device.

[0025] A method for fabricating a semiconductor light-emitting device includes sequentially epitaxially growing an n-type digital light-emitting diode (DBR), an active layer, and a p-type DBR on a substrate, wherein the reflectivity of the p-type DBR is higher than that of the n-type DBR; wherein the logarithm of the p-type DBR is A, and it is grown using a two-stage epitaxial growth method, including the following steps:

[0026] 1) First, grow the first part of the p-type DBR, the logarithm of the first part is B, 0.1≤B / A≤0.5; the last layer of the first part is the first cap layer, the optical thickness of the first cap layer is 1 / 16λ0 to 3 / 16λ0, λ0 is the target emission wavelength of the semiconductor light-emitting device;

[0027] 2) Perform reflection spectrum testing on the epitaxial wafer with the first cap layer to obtain the current center resonant wavelength of the reflection spectrum;

[0028] 3) Continue to grow the second part of the p-type DBR on the first cap layer.

[0029] Optionally, in step 3), before the second portion is grown, the surface of the first cap layer is further treated, the treatment including at least one of wet cleaning, heat treatment, dry etching or plasma cleaning.

[0030] The beneficial effects of this invention are as follows:

[0031] p-type DBR has two parts grown sequentially with a first cap layer in between, which can realize intermediate detection during the growth process to accurately confirm the resonant wavelength, thereby improving the wavelength yield of the product and providing a reliable manufacturing solution for n-side light-emitting semiconductor light-emitting devices.

[0032] By placing the light-emitting aperture on the n-side and having the p-electrode cover the effective light-emitting area on the p-side, uniform hole injection is obtained. Since the electron mobility is much higher than that of the hole carriers, the electron carriers can be injected efficiently and uniformly on the n-side. There is no need to make extra electrodes on the light-emitting aperture on the n-side, resulting in a more uniform power distribution, higher luminous efficiency, and improved overall luminous performance. This is suitable for applications of large-aperture, high-power semiconductor light-emitting devices.

[0033] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0034] Figure 1a This is a top view of the p-electrode in a p-side emitting RCLED of the prior art;

[0035] Figure 1b This is a schematic diagram of the luminous power distribution of a p-side emitting RCLED in the prior art;

[0036] Figure 2This is a bottom view of the RCLED device in Example 1;

[0037] Figure 3 for Figure 4 Cross-sectional view along the a-a' direction;

[0038] Figure 4 This is a schematic diagram of the active layer of the RCLED device in Example 1;

[0039] Figure 5 This is a schematic diagram of the epitaxial wafer with a first cap layer grown in the method for fabricating the epitaxial structure of the RCLED device in Example 1.

[0040] Figure 6 Schematic diagram of the epitaxial structure of the RCLED device in Example 2;

[0041] Figure 7 This is a schematic diagram of the RCLED device structure in Example 2;

[0042] Figure 8a The reflection spectrum test pattern of the epitaxial wafer before the growth of the second part of the p-type DBR in the fabrication method of the 940 nm RCLED epitaxial structure in the example;

[0043] Figure 8b The reflection spectrum test pattern after the second part of the p-type DBR is grown in the fabrication method of the 940 nm RCLED epitaxial structure in the example;

[0044] Figure label:

[0045] 10. First substrate; 10'. Second substrate; 21. n-type DBR; 22. Active layer; 221. n-type confinement layer; 222. Quantum well structure; 2221. Barrier layer; 2222. Well layer; 223. p-type confinement layer; 23'. Confinement hole epitaxial layer; 23. Confinement hole layer; 231. Oxidized region; 232. Unoxidized region; 24. p-type DBR; 241. First part of p-type DBR; 2411. Low refractive index layer of the first part; 2411'. Top low refractive index layer. Layers; 2412, High refractive index layer of the first part; 2413, First cap layer; 242, Second part of p-type DBR; 2421, Low refractive index layer of the second part; 2422, High refractive index layer of the second part; 2422', Bottom high refractive index layer; 25, Second cap layer; 26, Etching barrier layer; 27, n-type contact layer; 31, p electrode; 32, n electrode; 32a, Ring structure; 321, Pad; A, Light exit hole; B, Confinement hole; 5, p electrode; 51, Strip electrode. Detailed Implementation

[0046] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are merely illustrative to facilitate a better understanding of the invention, and their specific proportions can be adjusted according to design requirements. The "upper" and "lower" relationships of relative elements and the definitions of "front" and "back" in the graphics described herein should be understood by those skilled in the art to refer to the relative positions of the components; therefore, they can all be flipped to present the same component, and all of this should fall within the scope disclosed in this specification.

[0047] In this invention, unless otherwise expressly specified and limited, "above" or "below" a second feature can include direct contact between the first and second features, or contact between the first and second features not in direct contact but through another feature between them. Furthermore, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. In the description of this invention, the term "comprising" and any variations thereof mean "at least comprising."

[0048] The semiconductor light-emitting device of Example 1, such as Figure 2 and Figure 3 As shown, the structure includes a first substrate 10 and an epitaxial structure disposed on the first substrate 10. From bottom to top, the epitaxial structure includes an n-type DBR 21, an active layer 22, a confinement aperture layer 23, a p-type DBR 24, and a second cap layer 25. The p-type DBR 24 includes a first portion 241 grown first and a second portion 242 grown later. The second portion 242 is located above the first portion 241, and a first cap layer 2413 is provided at the junction of the first portion 241 and the second portion 242. A p-electrode 31 is provided on the second cap layer 25, and an n-electrode 32 is provided on the back side of the first substrate 10. The p-electrode 31 and the n-electrode 32 provide injection pathways for holes and electrons, respectively, forming a forward bias to drive the active layer 22 to emit light. The active layer 22 resonates and enhances the light through a resonant cavity formed by the upper and lower DBRs, thereby improving luminous efficiency and spectral purity.

[0049] In this embodiment, the semiconductor light-emitting device is exemplified by an RCLED device. The p-type DBR 24 has a higher total reflectivity than the n-type DBR 21, and the n-side is the light-emitting surface. The n-electrode 32 has an opening forming a light-emitting aperture. Specifically, the n-electrode 32 has a ring structure 32a, and the inner side of the ring structure 32a forms the light-emitting aperture A. The ring structure mentioned here refers to the n-electrode having a structure enclosed by a closed curve, with a blank area (not covered by electrode material) in the middle; this blank area is the light-emitting aperture. The ratio of the area of ​​the light-emitting aperture A to the area of ​​the RCLED device is 0.9~0.95. When the ratio is too low, the luminous efficiency per unit chip area is low, and the cost is high. When the ratio is greater than 0.95, the n-electrode area needs to be compressed, leading to an increase in the contact resistance on the n-side and a decrease in device performance. The limiting hole layer 23 has a limiting hole B for lateral limiting of current and light field. The diameter of the limiting hole B is smaller than the diameter of the light-emitting hole A. Specifically, the surface of the first substrate 10 is a horizontal plane. The orthographic projection of the limiting hole B on the surface of the first substrate 10 (hereinafter referred to as the projection) is located within the projection range of the light-emitting hole A, so that the current limiting and the optical mode are spatially coincided to improve the light extraction efficiency.

[0050] The n-type DBR 21 is composed of alternating layers of low-refractive-index and high-refractive-index materials, each with an optical thickness of 1 / 4λ0 (λ0 being the target emission wavelength of the RCLED device). For different emission wavelengths, different aluminum (Al) content compounds such as AlGaAs, AlInN / GaN, and AlInAs / GaInAs can be selected, and n-type doping is performed. Doping elements can be silicon (Si), germanium (Ge), tellurium (Te), etc., allowing electron carriers to be efficiently injected into the active layer 22 under the influence of an applied electric field. The n-type DBR 21 serves as the light-emitting side, with a reflectivity of 50%–70% and a pair number of dopant layers of 5–7.

[0051] The active layer 22 includes a light-emitting structure for generating self-emitting radiation, including one or more combinations of pn junctions, pin junctions, quantum well structures, superlattice structures, and quantum dot light-emitting structures. As an optional implementation, such as... Figure 4As shown, the active layer 22, from bottom to top, includes an n-type confinement layer 221, a quantum well structure 222, and a p-type confinement layer 223. The quantum well structure 222 consists of alternating stacks of barrier layers 2221 and well layers 2222. The material combination of the well layers 2222 and barrier layers 2221 is selected from one of the following systems: GaInP / AlGaInP, GaAs / AlGaAs, InGaAs / GaAsP, InGaAs / AlGaAs, AlGaInAs / AlGaAsP, AlGaInAs / AlGaInAs, InGaAsP / InGaAsP, InGaN / GaN, etc. Electron carriers and hole carriers are injected into the quantum well structure 222, respectively, and photons are generated through radiative recombination. Different wavelengths of light emission can be achieved by selecting materials and controlling the composition. The n-type confinement layer 221 and the p-type confinement layer 223 are made of materials with a bandgap wider than the adjacent quantum well active layers to form an effective carrier barrier, prevent carrier escape, and achieve high-efficiency photoelectric conversion.

[0052] In this embodiment, the confining hole layer 23 is disposed between the active layer 22 and the first portion 241 and is p-type doped; in other embodiments, a confining hole layer can also be disposed between the active layer 22 and the n-type DBR 21 and is n-type doped.

[0053] The first part 241 and the second part 242 of the p-type DBR 24 respectively include alternating low-refractive-index layers and high-refractive-index layers. Corresponding to different emission wavelengths, they can be selected from compound semiconductor material pairs such as AlGaAs, AlInN / GaN, and AlInAs / GaInAs with different aluminum (Al) contents, and are p-type doped. The doping elements can be selected from carbon (C), zinc (Zn), magnesium (Mg), etc., with a doping concentration of 0.5E18cm⁻¹. -3 ~5E18cm -3 This allows hole carriers to be efficiently injected into the active layer 22 under the influence of an applied electric field. The p-type DBR 24, as the high-reflectivity side, has a total reflectivity ≥98%. If the total number of pairs of p-type DBR 24 is A, and the number of pairs of the first part 241 is B, then 0.1 ≤ B / A ≤ 0.5, meaning the first part does not exceed half of the total. Preferably, the reflectivity of the first part 241 is 50%~90%, and the number of pairs is 5~15, while the number of pairs of the second part 242 is 25~35.

[0054] The first cap layer 2413 is located at the junction of the first portion 241 and the second portion 242, i.e., at the very end of the first portion 241. It serves as a surface protection layer for performance testing during the intermediate growth stage of the epitaxial wafer when it reaches the first portion 241, and also enhances the wavelength depth characteristics of the resonant cavity during reflectance spectroscopy testing. Preferably, it is a compound semiconductor material with lattice matching to the low-refractive-index and high-refractive-index layer materials selected for the p-type DBR and possessing oxidation resistance properties, with a refractive index higher than that of the low-refractive-index layer. The first cap layer 2413 is also p-type doped with a doping concentration of 0.5 E18cm⁻¹. -3 ~5E18cm -3 It is preferred that it be homologous to the low-refractive-index layer and the high-refractive-index layer, and the doping concentration is similar, in order to maintain electrical continuity, ensure smooth injection of hole carriers from the p side, and avoid impurity diffusion or interface barriers.

[0055] Specifically, the first part 241 includes alternating low-refractive-index layers 2411 and 2412 with optical thicknesses of 1 / 4λ0, ending with a top low-refractive-index layer 2411', which also has an optical thickness of 1 / 4λ0. A first cap layer 2413 is disposed on the top low-refractive-index layer 2411'. The second part 242 begins with a bottom high-refractive-index layer 2422', followed by alternating low-refractive-index layers 2421 and 2422 with optical thicknesses of 1 / 4λ0. The sum of the optical thicknesses of the bottom high-refractive-index layer 2422' and the first cap layer 2413 is 1 / 4λ0, forming a DBR pair with the top low-refractive-index layer 2411'.

[0056] It should be noted that in actual engineering, the sum of the optical thicknesses of the first cap layer 2413 and the bottom high-refractive-index layer 2422' is usually controlled to be C×1 / 4 λ0, where C ranges from 0.95 to 1.05.

[0057] The optical thickness of the first cap layer 2413 is between 1 / 16 λ0 and 3 / 16 λ0. The smaller the optical thickness of the first cap layer 2413, the stronger its effect on enhancing the wavelength depth characteristic of the epitaxial layer reflection spectrum test resonant cavity; however, a thickness greater than 3 / 16 λ0 is insufficient to achieve this effect. Conversely, when the optical thickness of the first cap layer 2413 is less than 1 / 16 λ0, it fails to protect the semiconductor stack. Preferably, the thickness of the first cap layer 2413 is 20~30 nm.

[0058] In a preferred embodiment, the material system of the low-refractive-index layer / high-refractive-index layer in the first and second parts of the p-type DBR is Al. x Ga 1-x As / Al y Ga 1-y As, where 0.7 ≤ x < 1, 0 < y ≤ 0.2; the material of the first cap layer is GaAs or In.z Ga 1-z P, where 0.45 ≤ z ≤ 0.55. GaAs or In z Ga 1-z P can prevent Al oxidation and other damage when AlGaAs-based DBRs are exposed to atmospheric testing environments, and its lattice matching with AlGaAs facilitates control over the epitaxial quality of the grown material during reflow.

[0059] Thus, the formed p-type DBR 24 includes a first DBR formed by several pairs of low-refractive-index layers / high-refractive-index layers, and a pair of second DBRs located between the pairs of first DBRs. The second DBR is composed of a first layer, a second layer, and a third layer stacked sequentially. The first layer is made of the same material as the low-refractive-index layer, with an optical thickness of 0.237λ0~0.2625λ0. The third layer is made of the same material as the high-refractive-index layer, and the refractive index of the second layer is higher than that of the third layer. The optical thickness of the second layer is 1 / 16 λ0 to 3 / 16 λ0, and the sum of the optical thicknesses of the second and third layers is 0.237λ0~0.2625λ0. In the above embodiment, the first layer, the second layer, and the third layer are respectively Al x Ga 1-x As top low-refractive-index layer 2411', GaAs or In z Ga 1-z P first cap layer 2413 and Al y Ga 1-y As the bottom high-refractive-index layer 2422'.

[0060] In another preferred embodiment, the material system of the low refractive index layer / high refractive index layer of the first part and the second part of the p-type DBR is AlInAs / GaInAs, and the material of the first cap layer is GaInAs.

[0061] In yet another preferred embodiment, the material system of the low refractive index layer / high refractive index layer of the first part and the second part of the p-type DBR is AlInN / GaN, and the material of the first cap layer is GaN.

[0062] The second cap layer 25 is a p-type contact layer of GaAs, which achieves good electrical contact with the p-electrode through heavy doping, with a doping concentration of 2E19-8E19 cm⁻¹. -3 .

[0063] The method for fabricating the epitaxial structure of the aforementioned RCLED device first involves sequentially epitaxially growing an n-type DBR 21, an active layer 22, and a confinement via epitaxial layer 23' on a first substrate 10 in an epitaxial growth apparatus, followed by the growth of a p-type DBR 24, which employs a two-stage epitaxial growth process, including the following steps:

[0064] 1) First, the first part 241 of the p-type DBR is grown, including alternating low-refractive-index layers 2411 and high-refractive-index layers 2412, with the last alternation being the top low-refractive-index layer 2411'. A first cap layer 2413 is grown on the top low-refractive-index layer 2411', resulting in an epitaxial wafer with the first cap layer, such as... Figure 5 As shown;

[0065] 2) Remove the epitaxial wafer with the first cap layer from the growth equipment, perform a reflectance spectrum test, obtain the current center resonant wavelength of the reflectance spectrum, and confirm whether the position of the resonant wavelength deviates from the preset value;

[0066] 3) Return the epitaxial wafer to the epitaxial growth equipment and continue to grow the second part 242 of the p-type DBR on the first cap layer 2413. First, grow the bottom high refractive index layer 2422', and then alternately grow the low refractive index layer 2421 and the high refractive index layer 2422 until the set log number is reached.

[0067] Finally, the second cap layer 25 is grown.

[0068] Conventionally, to improve the quality of epitaxial growth, a buffer layer or other known structures can be grown on the first substrate before the n-type DBR. These will not be elaborated upon and are simplified in the figure.

[0069] In step 3), after returning the epitaxial wafer to the growth equipment, the surface of the first cap layer 2413 is further treated. This treatment includes at least one of wet cleaning, heat treatment, dry etching, or plasma cleaning. The treatment removes the oxide layer or other contaminants generated during oxidation in the atmospheric environment, thereby improving growth quality.

[0070] The center resonant wavelength of the reflection spectrum (also known as the cavity mode wavelength) refers to the longitudinal mode position determined by the Fabry-Perot resonant cavity, which is composed of the active layer and the distributed Bragg mirrors (DBRs) on both sides. On the reflectivity-wavelength (R-λ) test curve, this wavelength corresponds to a minimum reflectivity point located between the high reflectivity plateaus of the two DBRs. Physically, this means the resonant cavity has minimal reflectivity at this wavelength. In RCLED device design, when this resonant wavelength is precisely aligned with the emission center wavelength of the active layer, the device achieves the highest light extraction efficiency and the narrowest emission spectrum. Therefore, accurately acquiring and controlling this resonant wavelength during manufacturing is crucial for achieving wavelength consistency and high yield in RCLEDs. However, for n-side RCLEDs, the p-type DBR, after growth, acts as the high-reflectivity side, causing most of the probe light incident from the front of the epitaxial wafer to be directly reflected by the p-type DBR. This results in the cavity mode signal in the reflection spectrum being submerged in the strong reflective background of the p-type DBR itself, making it difficult to measure. Therefore, when the high reflectivity on the p-side is not fully constructed during the p-type DBR growth process, utilizing the process window provided by the first cap layer for resonant wavelength testing can effectively improve the product wavelength yield. Furthermore, the first cap layer can enhance the wavelength depth characteristics of the resonant cavity during epitaxial reflection spectrum testing, which is beneficial for accurately confirming the resonant wavelength during reflection spectrum testing.

[0071] The RCLED device constructed using the aforementioned epitaxial structure will achieve n-side light emission. The confinement hole epitaxial layer 23' can be formed into the confinement hole B through processes such as lateral oxidation. For example, the material of the confinement hole epitaxial layer 23' is AlGaAs, InAlGaAs, or InAlAs with a high Al content, the Al content is 0.95–1, and the thickness is 10–30 nm. Its high aluminum content can be used to form an alumina insulating region at the edge through lateral wet oxidation, thereby forming a confinement hole in the unoxidized central region for lateral confinement of current and light field.

[0072] In this embodiment, as Figure 2 As shown, the confinement hole layer 23 has an oxidized region 231 on the periphery and an unoxidized region 232 in the center. The resistivity of the oxidized region 231 is higher than that of the unoxidized region 232, and its refractive index is lower than that of the unoxidized region 232. The unoxidized region 232 forms the confinement hole B. In terms of current confinement, it enables the current to converge into the conduction channel of the confinement hole B region, which significantly improves the carrier injection efficiency and avoids lateral diffusion and non-radiative recombination losses. In terms of the optical field, the low-refractive-index outer layer and the high-refractive-index center form a refractive index transition waveguide, which provides strong lateral confinement to the optical field and makes the optical mode peak coincide with the current injection center, thereby improving the external quantum efficiency.

[0073] The projection of the p-electrode 31 at least covers the projection of the aperture A, and more preferably covers the entire surface, to achieve uniform and efficient carrier injection. The p-electrode 31 is composed of gold (Au), silver (Ag), aluminum (Al), nickel (Ni), platinum (Pt), titanium (Ti), or other metal electrode materials with good conductivity, or a stack of different metal materials. Its full-surface coverage can further achieve rapid heat dissipation and improve operational reliability.

[0074] In this embodiment, both the limiting hole B and the light-emitting hole A are square holes, preferably concentrically arranged. The aperture diameter refers to their width. The aperture diameter d1 of the limiting hole B is 200~500 μm, and the aperture diameter d2 of the light-emitting hole A is larger than the aperture diameter d1 of the limiting hole B. The ratio d2 / d1 can be selected as 1.02~1.15, more preferably 1.03~1.06, to reduce diffraction and coupling losses and support high-power output. Specifically, for the light-emitting platform of a single device, the width d3 of the oxide region 231 (i.e., the distance extending horizontally inward from the edge of the platform) is 10~20 μm; the n-electrode 32 is located in the edge region, and the width d4 of its annular structure 32a (i.e., the distance extending horizontally inward from the edge of the platform) is 5~10 μm. The pad 321 of the n-electrode 32 can be set at the edge of the platform, connected to the annular structure 32a, with the aim of avoiding obstruction of the light-emitting hole A as much as possible. Furthermore, the shapes of the limiting aperture B and the light-emitting aperture A are not restricted; they preferably have the same shape, for example, they can be circular, with the aperture diameter referring to the diameter of the circle; for other shapes, the aperture diameter can refer to the diameter of the circumcircle. Since the electron mobility on the n-side is much greater than that of the hole carriers, the lateral diffusion resistance is small. A ring structure on the n-electrode 32 can achieve uniform and efficient carrier injection. The light-emitting aperture A is unobstructed, resulting in a large luminous area and improved light output power for large-aperture emission. The n-electrode 32 can also be constructed from gold (Au), silver (Ag), aluminum (Al), nickel (Ni), platinum (Pt), titanium (Ti), or other metal electrode materials with good conductivity, or a stack of different metal materials.

[0075] In this embodiment, light is emitted through the first substrate 10, which is a conductive substrate, such as an n-doped GaAs substrate. Its bandgap is greater than the photon energy corresponding to the emission wavelength of the resonant cavity light-emitting diode, making it suitable for emission wavelengths in the range of 870~1300nm. During device fabrication, the confinement hole layer 23' of the epitaxial structure of the above-mentioned RCLED device is formed by a wet oxidation process. After thinning the first substrate 10, an n-electrode 32 and a p-electrode 31 are fabricated on the back side of the first substrate 10 and the top surface of the epitaxial structure, respectively.

[0076] The semiconductor light-emitting device of Example 2 has the following epitaxial structure: Figure 6As shown, the substrate includes, in sequence, an etch barrier layer 26, an n-type contact layer 27, an n-type DBR 21, an active layer 22, a confinement via epitaxial layer 23', a p-type DBR 24, and a second cap layer 25 disposed on a second substrate 10'. The p-type DBR 24 has a first portion 241 grown earlier and a second portion 242 grown later. The second portion 242 is located above the first portion 241, and a first cap layer 2413 is provided at the junction of the first portion 241 and the second portion 242. The specific configuration of the p-type DBR 24 is described in Example 1 and will not be repeated here. The reflectivity of the n-type DBR 21 is less than the total reflectivity of the p-type DBR 24, and the n-side is the light-emitting side. Its fabrication method is as follows:

[0077] First, in an epitaxial growth apparatus, a barrier layer 26, an n-type contact layer 27, an n-type DBR 21, an active layer 22, a confinement via layer epitaxial layer 23' are sequentially epitaxially grown on the second substrate 10'. Then, a p-type DBR 24 is grown, employing a two-stage epitaxial growth process, including the following steps:

[0078] 1) The first part 241 of the p-type DBR is first grown, and the last part of the first part 241 is the first cap layer 2413;

[0079] 2) Remove the epitaxial wafer with the first cap layer from the growth equipment, perform a reflectance spectrum test, obtain the current center resonant wavelength of the reflectance spectrum, and confirm whether the position of the resonant wavelength deviates from the preset value;

[0080] 3) Return the epitaxial wafer to the epitaxial growth equipment and continue growing the second part of the p-type DBR on the first cap layer 243.

[0081] Conventionally, to improve the quality of epitaxial growth, a buffer layer or other known structures can be grown on the second substrate 10' first, which will not be elaborated upon and are simplified in the figure.

[0082] Example of a semiconductor light-emitting device in Embodiment 2 is an RCLED device. The difference from Embodiment 1 is that its second substrate 10' is a peelable structure, and the n-type contact layer 27 is, for example, heavily n-type doped GaAs with a thickness of 10~40nm and a doping concentration of 1-5E18cm. -3 The n-type contact layer 27 forms a low-resistance ohmic contact with the n-electrode 32 on the back side, further providing a high-mobility electron channel, reducing power consumption and improving external quantum efficiency. An etch barrier layer 26 is disposed between the n-type contact layer 27 and the second substrate 10'. The etch barrier layer 26 and the n-type contact layer 27 have different etching selectivity to facilitate subsequent removal by selective etching. Since the second substrate 10' is removed in subsequent devices, a wider range of substrates can be selected for different epitaxial material systems and emission wavelengths; for example, it can be a GaAs substrate, InP substrate, sapphire substrate, silicon substrate, etc., without limitations on its conductivity and bandgap.

[0083] An RCLED device was fabricated using the epitaxial structure of Example 2. The confinement hole layer 23' of the aforementioned epitaxial structure was formed using a wet oxidation process. The second substrate 10' and the etching barrier layer 26 were removed by etching. An n-electrode 32 and a p-electrode 31 were fabricated on the back side of the n-type contact layer 27 and the top surface of the epitaxial structure, respectively. The resulting RCLED device is shown below. Figure 7 As shown, its epitaxial structure, from bottom to top, includes an n-type contact layer 27, an n-type DBR 21, an active layer 22, a confinement aperture layer 23, a p-type DBR 24, and a second cap layer 25. A p-electrode 31 is disposed on the second cap layer 25, and an n-electrode 32 is disposed on the back side of the n-type contact layer 27. The total reflectivity of the p-type DBR 24 is higher than that of the n-type DBR 21, and the n-side is the light-emitting surface. Similarly, as in Embodiment 1, the n-electrode 32 forms a light-emitting aperture A, and the confinement aperture layer 23 has a confinement aperture B, the diameter of which is smaller than the diameter of the light-emitting aperture A.

[0084] When the photon energy corresponding to the emission wavelength of the device is greater than the bandgap of the substrate material, the substrate side serves as the light-emitting surface, and the substrate material will absorb the emitted light, thus reducing the luminous efficiency. In this embodiment, the second substrate 10' is stripped in the final device structure, avoiding its influence on light emission and thus broadening the range of substrate materials that can be selected. For example, for devices with emission wavelengths of 630nm-1300nm, GaAs substrates can still be used, and subsequent stripping will not affect the device's luminous efficiency.

[0085] The following details the 940 nm RCLED device and its fabrication method. The fabrication of the device's epitaxial structure includes:

[0086] The MOCVD process was employed, using an n-type GaAs substrate. The substrate was placed in a growth chamber to grow an n-type GaAs buffer layer. Subsequently, the following layers were grown sequentially: an etch barrier layer of 20 nm thick InGaP; and an n-type contact layer of 30 nm thick with an n-type doping concentration of 4E18 cm⁻¹. -3 GaAs; n-type DBR, 8 pairs of Al 0.9 Ga 0.1 As / Al 0.1 Ga 0.9 As, n-type doping concentration is 2E18cm⁻¹ -3 The active layers, in order, include: n-type confinement layers (Al). 0.9 Ga 0.1 As, thickness 60nm, n-type doping concentration 1E18cm⁻¹ -3 ), quantum well structure (3 sets of In) 0.16 Ga 0.84 As / Al 0.2 Ga 0.8As quantum well, with a thickness of 5nm / 6nm), p-type confinement layer (Al 0.9 Ga 0.1 As, thickness 60nm, p-type doping concentration 1E18cm⁻¹ -3 ); confined hole epitaxial layer, Al 0.99 Ga 0.01 As, thickness 20nm, p-type doping concentration 2E18cm⁻¹ -3 The first part of the p-type DBR, 10 pairs of Al 0.9 Ga 0.1 As / Al 0.1 Ga 0.9 As+1 layer Al 0.9 Ga 0.1 As, p-type doping concentration is 2E18cm⁻¹ -3 The first cap layer has a thickness of 25 nm and a p-type doping concentration of 2E18 cm⁻¹. -3 GaAs.

[0087] The growth process was interrupted, and the epitaxial wafer was removed for reflectance spectroscopy testing. The probe light was incident from the front side (i.e., the side of the first cap layer). For example... Figure 8a As shown, the central resonant wavelength of its reflection spectrum is 940 nm, which matches the central emission wavelength of the target at 940 nm.

[0088] Afterwards, the epitaxial wafer is returned to the growth chamber, where it undergoes high-temperature pretreatment, followed by the introduction of H2 and AsH3 to remove the surface oxide film. The second part of the p-type DBR growth then continues: first, Al is grown. 0.1 Ga 0.9 As a bottom high-refractive-index layer, with its optical thickness summed with that of the first cap layer being 1 / 4λ0, 30 pairs of Al are then regrown. 0.9 Ga 0.1 As / Al 0.1 Ga 0.9 As, p-type doping concentration is 2E18cm⁻¹ -3 Finally, a second cap layer of p-type GaAs is grown, with a p-type doping concentration of 5E19cm⁻¹. -3 This yields the complete epitaxial structure of the RCLED device.

[0089] The reflection spectrum of the complete RCLED device epitaxial structure was measured, with the probe light incident from the front (i.e., the p-type DBR side). Figure 8b As shown, due to the high reflectivity of the p-type DBR, the central resonant wavelength of the reflection spectrum cannot be observed.

[0090] After mesa etching of the prepared 940nm RCLED epitaxial structure, wet oxidation was performed on the confinement hole epitaxial layer to obtain a confinement hole with a diameter of approximately 300 μm. After etching to remove the substrate and etch barrier layer, metal was deposited on the back side of the n-type contact layer and the top surface of the epitaxial structure to fabricate n-electrodes and p-electrodes, respectively. The p-electrode was deposited over the entire surface, and the n-electrode had a light-emitting hole with a diameter of 310 μm, which was concentrically positioned with the confinement hole. Since there were no additional electrode structures on the light-emitting hole, the power density in the light-emitting hole region remained essentially consistent and uniformly distributed, ensuring light extraction efficiency and beam quality.

[0091] The semiconductor light-emitting device in the above embodiment is an example of an RCLED device. In other embodiments, the semiconductor light-emitting device can also be an LED / VCSEL, etc. Its epitaxial structure also includes an n-type DBR, an active layer and a p-type DBR stacked vertically from bottom to top, and has a similar structural arrangement to the above RCLED device. The size of the light-emitting aperture and the number of DBR pairs are adjusted according to the device type.

[0092] The semiconductor light-emitting devices described above, when applied to electronic products, can achieve large aperture, high-power light emission, and possess uniform power distribution and high luminous efficiency. These electronic products include, but are not limited to, pulse oximeters, multi-parameter monitors, vehicle-mounted head-up displays (HUDs), and miniature projectors.

[0093] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of this application can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0094] The above embodiments are only used to further illustrate a semiconductor light-emitting device and its preparation method and electronic products according to the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A semiconductor light-emitting device, characterized in that: The device includes an epitaxial structure comprising an n-type DBR, an active layer, and a p-type DBR stacked vertically from bottom to top, wherein the reflectivity of the p-type DBR is higher than that of the n-type DBR; the p-type DBR has a first portion grown first and a second portion grown later, the second portion being located above the first portion, and a first cap layer being provided at the junction of the first portion and the second portion, wherein the optical thickness of the first cap layer is 1 / 16 λ0 to 3 / 16 λ0, where λ0 is the target emission wavelength of the semiconductor light-emitting device; The total number of logarithms of the p-type DBR is A, and the number of logarithms of the first part is B, where 0.1 ≤ B / A ≤ 0.

5.

2. The semiconductor light-emitting device according to claim 1, characterized in that: The reflectivity of the n-type DBR is 50%~70%, and the total reflectivity of the p-type DBR is greater than 98%, wherein the reflectivity of the first part is 50%-90%.

3. The semiconductor light-emitting device according to claim 2, characterized in that: The n-type DBR has 5 to 7 pairs; the first part of the p-type DBR has 5 to 15 pairs, and the second part has 25 to 35 pairs.

4. The semiconductor light-emitting device according to claim 1, characterized in that: The thickness of the first cap layer is 10~30nm.

5. The semiconductor light-emitting device according to claim 1, characterized in that: The first part and the second part respectively include alternating low refractive index layers and high refractive index layers, the refractive index of the first cap layer is higher than the refractive index of the low refractive index layer; the first cap layer is disposed on the low refractive index layer, the second part starts as the bottom high refractive index layer, and the sum of the optical thicknesses of the first cap layer and the bottom high refractive index layer is C×1 / 4 λ0, where C ranges from 0.95 to 1.

05.

6. The semiconductor light-emitting device according to claim 5, characterized in that: The material system of the low-refractive-index layer / high-refractive-index layer is Al. x Ga 1-x As / Al y Ga 1-y As, where 0.7 ≤ x < 1, 0 < y ≤ 0.2; the material of the first cap layer is GaAs or In. z Ga 1-z P, where 0.45 ≤ z ≤ 0.55; Alternatively, the material system of the low refractive index layer / high refractive index layer is AlInAs / GaInAs, and the material of the first cap layer is GaInAs; Alternatively, the material system of the low refractive index layer / high refractive index layer is AlInN / GaN, and the material of the first cap layer is GaN.

7. The semiconductor light-emitting device according to claim 1, characterized in that: It also includes an n-electrode and a p-electrode, wherein the p-electrode is located above the epitaxial structure and the n-electrode is located below the epitaxial structure; the n-electrode has an opening to form a light-emitting aperture, and the area of ​​the light-emitting aperture is 0.9~0.95 times the area of ​​the semiconductor light-emitting device; the projection of the p-electrode on the horizontal plane covers the projection of the light-emitting aperture on the horizontal plane.

8. The semiconductor light-emitting device according to claim 7, characterized in that: The epitaxial structure further includes a confining aperture layer having confining apertures for laterally confining current and optical field; the projection of the confining aperture on the horizontal plane is located within the projection of the light-emitting aperture on the horizontal plane.

9. The semiconductor light-emitting device according to claim 8, characterized in that: The aperture of the limiting hole is 200~500μm, and the ratio of the aperture of the light-emitting hole to the aperture of the limiting hole is 1.02~1.15:

1.

10. The semiconductor light-emitting device according to claim 7, characterized in that: It also includes a conductive substrate disposed between the n-type DBR and the n-electrode, wherein the band gap of the conductive substrate material is greater than the photon energy corresponding to the emission wavelength of the semiconductor light-emitting device.

11. The semiconductor light-emitting device according to claim 7, characterized in that: It also includes an n-type contact layer disposed between the n-type DBR and the n-electrode.

12. A semiconductor light-emitting device, characterized in that: It includes an n-type DBR, a p-type DBR, and an active layer sandwiched between the n-type DBR and the p-type DBR; the p-type DBR includes several pairs of first DBRs and a pair of second DBRs located between the several pairs of first DBRs, wherein the first DBRs are composed of a low-refractive-index layer and a high-refractive-index layer, and the second DBRs are composed of a first layer, a second layer, and a third layer stacked sequentially; wherein, The first layer is made of the same material as the low-refractive-index layer, and its optical thickness is 0.237λ0~0.2625λ0. The third layer is made of the same material as the high refractive index layer, and the refractive index of the second layer is higher than that of the third layer; The optical thickness of the second layer is 1 / 16 λ0 to 3 / 16 λ0, and the sum of the optical thicknesses of the second and third layers is 0.237λ0 to 0.2625λ0; where λ0 is the target emission wavelength of the semiconductor light-emitting device.

13. An electronic product, characterized in that, The electronic product includes the semiconductor light-emitting device according to any one of claims 1 to 12.

14. A method for fabricating a semiconductor light-emitting device, characterized in that, This includes the sequential epitaxial growth of an n-type DBR, an active layer, and a p-type DBR on a substrate, where the reflectivity of the p-type DBR is higher than that of the n-type DBR. The P-type DBR has a logarithm of A and is grown using a two-segment epitaxial growth method, including the following steps: 1) First, grow the first part of the p-type DBR, the logarithm of the first part is B, 0.1≤B / A≤0.5; the last layer of the first part is the first cap layer, the optical thickness of the first cap layer is 1 / 16λ0 to 3 / 16λ0, λ0 is the target emission wavelength of the semiconductor light-emitting device; 2) Perform reflection spectrum testing on the epitaxial wafer with the first cap layer to obtain the current center resonant wavelength of the reflection spectrum; 3) Continue to grow the second part of the p-type DBR on the first cap layer.

15. The method for fabricating a semiconductor light-emitting device according to claim 14, characterized in that: In step 3), prior to the growth of the second portion, the surface of the first cap layer is further treated, the treatment including at least one of wet cleaning, heat treatment, dry etching or plasma cleaning.

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