A semi-polar light emitting device and a preparation method thereof

Abstract

The application relates to the technical field of semiconductor photoelectric devices, and discloses a semi-polar light-emitting device and a preparation method. The semi-polar light-emitting device comprises a first substrate, the first substrate comprises a ridge-shaped structure and a wing-shaped structure formed on the top of the ridge-shaped structure, the wing-shaped structure has inclined side walls extending from the center line of the top of the wing-shaped structure to both sides, and the inclined side walls are semi-polar surfaces; and a device layer, the device layer is grown on the inclined side walls of the wing-shaped structure and comprises, from bottom to top, an electron-providing layer, an active region comprising at least one quantum well, and a hole-providing layer. According to the application, the semi-polar gallium nitride substrate comprising the ridge-shaped structure and the wing-shaped structure can effectively inhibit quantum confinement Stark effect, the semi-polar surface makes the direction of the polarization electric field and the growth direction form a certain angle, thereby greatly weakening the harmful electric field along the growth direction, and the electron and hole wave function overlap degree is significantly increased.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device technology, specifically to a semi-polar light-emitting device and its fabrication method. Background Technology

[0002] Gallium nitride (GaN), as a core material of third-generation semiconductors, holds an irreplaceable position in the field of high-efficiency optoelectronic devices and is widely used in solid-state lighting, displays, ultraviolet detection, and sterilization. Conventional GaN-based devices are typically epitaxially grown on polar c-plane (0001) GaN substrates due to the maturity, low cost, and ease of obtaining large-size wafers. However, using the c-plane as the epitaxial surface presents an inherent physical defect: strong spontaneous polarization and piezoelectric polarization effects exist along the

[0001] direction (c-axis). In the active region of a quantum well, these polarization effects generate a strong built-in electric field, namely the quantum confinement Stark effect (QCSE). This electric field causes spatial separation of electrons and holes in the quantum well structure due to band tilt, significantly reducing radiative recombination efficiency and causing a redshift in the emission wavelength with increasing injection current. This effect is particularly severe in long-wavelength (such as green and yellow) InGaN quantum wells, becoming a major bottleneck restricting the development of high-brightness, high-efficiency green light and longer-wavelength light-emitting devices.

[0003] To fundamentally eliminate or mitigate quantum well recombination efficiency (QCSE), researchers have proposed growing GaN devices on nonpolar surfaces (such as the a-plane {11-20}, m-plane {10-10}) or semipolar surfaces (such as {11-22}, {10-11}, {20-21}, etc.). On these crystal surfaces, the direction of the polarization electric field is perpendicular to or at a certain angle to the epitaxial growth direction of the device, thereby effectively suppressing or eliminating harmful electric fields along the growth direction, greatly improving the radiative recombination efficiency of the quantum well, and enhancing wavelength stability. Although nonpolar / semipolar surfaces have significant theoretical advantages, their industrialization faces enormous challenges. The main obstacle is that the preparation of high-quality nonpolar or semipolar bulk GaN single-crystal substrates is extremely difficult, costly, and limited in size. Currently, these substrates are usually obtained by oblique cutting from large c-plane GaN ingots, which not only makes it difficult to increase the size (usually much smaller than 2 inches) but also makes them extremely expensive, failing to meet the needs of large-scale commercial production. Furthermore, directly epitaxially growing nonpolar / semipolar GaN films on heterogeneous substrates (such as sapphire) introduces extremely high dislocation densities (typically >10). 9 cm -2 Severe defects can negate the performance advantages of reducing the polarization field, resulting in a decrease in device efficiency.

[0004] Therefore, how to prepare a high-quality light-emitting active region with low defect density and effective suppression of polarization electric field has become a key technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a semi-polar surface substrate light-emitting device and its fabrication method.

[0006] This invention provides a semi-polar light-emitting device, comprising: A first substrate includes a ridge structure and a wing structure formed on top of the ridge structure, the wing structure having inclined sidewalls extending from its top centerline to both sides, the inclined sidewalls being semi-polar surfaces; The device layer, grown on the inclined sidewall of the wing-shaped structure, includes, from bottom to top, at least an electron-providing layer, an active region including at least one quantum well, and a hole-providing layer.

[0007] In some embodiments, a second substrate is further included, wherein the first substrate is grown on the second substrate.

[0008] In some embodiments, it also includes: A mask layer disposed on the second substrate, comprising at least two parallel strip masks, wherein a strip window exposing the second substrate is formed between the at least two strip masks; The ridge structure fills the strip window, and the wing structure is located on top of the ridge structure and extends to both sides to cover part of the mask layer.

[0009] In some embodiments, the material of the first substrate is GaN, AlN, InN, AlGaN, InGaN, or AlInGaN, and the material of the second substrate is GaN, sapphire, Si, SiC, GaAs, or InP.

[0010] In some embodiments, the first substrate is an N-type substrate, and the top of the semi-polar light-emitting device is exposed above the first substrate, with the exposed area of ​​the first substrate used to provide an N-type electrode.

[0011] In some embodiments, the hole-providing layer and the active region are physically and electrically isolated to define at least two independent light-emitting units that share the first substrate and an N-type electrode, wherein the first substrate provides electrons to the at least two independent light-emitting units.

[0012] This invention also provides a method for fabricating a semi-polar light-emitting device, comprising the following steps: A mask layer is prepared on a second substrate, the mask layer comprising at least two parallel strip masks arranged at equal intervals, and a strip window is formed between adjacent strip masks to expose the substrate, the strip window exposing the second substrate below; In the substrate area exposed by the strip window, a first substrate is formed by longitudinal growth, and the first substrate is grown vertically upward until it fills the window and covers the sidewall of the strip mask, forming a ridge structure. After the first substrate extends beyond the strip window, the growth process parameters are changed so that the first substrate grows laterally from the top of the ridge structure to above the mask. The growth conditions are controlled so that the semi-polar surface is exposed and expanded as a stable growth surface, thereby forming a wing structure on the first substrate. The wing structure has inclined sidewalls extending from its top centerline to both sides, and the inclined sidewalls are semi-polar surfaces. A device layer comprising at least an electron-providing layer, an active region comprising at least one quantum well, and a hole-providing layer is epitaxially grown on the inclined sidewall of the wing-shaped structure.

[0013] In some embodiments, the spacing between adjacent strip masks of the mask layer is configured to be 10-100 μm, and the width of the strip mask is configured to be 100-500 μm.

[0014] In some embodiments, the first substrate is an N-type substrate, and the fabrication method further includes: The light-emitting device is longitudinally etched to expose the first substrate, and an N-type electrode is fabricated in the exposed area of ​​the first substrate.

[0015] In some embodiments, the preparation method further includes: The light-emitting device is longitudinally etched to physically and electrically isolate the hole-providing layer and the active region, thereby defining at least two independent light-emitting units that share the first substrate and an N-type electrode. The first substrate provides electrons to the at least two independent light-emitting units.

[0016] In some embodiments, the preparation method further includes: A P-type electrode is prepared on the surface of the hole-providing layer of the at least two independent light-emitting units.

[0017] In some embodiments, the spacing between adjacent strip masks of the mask layer is greater than the width of the wing-like structure of the semi-polar surface nitride substrate.

[0018] In some embodiments, the material of the first substrate is GaN, AlN, InN, AlGaN, InGaN, or AlInGaN, and the material of the second substrate is GaN, sapphire, Si, SiC, GaAs, or InP.

[0019] Compared with the prior art, the present invention provides a semi-polar light-emitting device and its fabrication method, which has the following beneficial effects: This invention effectively suppresses the quantum confinement Stark effect (QCSE) by constructing a semi-polar growth surface on a conventional substrate. The semi-polar surface causes the polarization electric field direction to form a certain angle with the growth direction, thereby significantly weakening the harmful electric field along the growth direction and significantly increasing the overlap of electron and hole wave functions. This not only improves the internal quantum efficiency of green light-band devices but also reduces the wavelength blue shift phenomenon in InGaN quantum wells, improving the stability of the output wavelength. Furthermore, the semi-polar surface facilitates the introduction of higher indium (In) content into the quantum well without causing severe lattice relaxation or phase separation, making it possible to overcome the "green gap" and realize high-efficiency green and even yellow-orange lasers.

[0020] This invention avoids the direct use of expensive and size-limited semi-polar substrates. Instead, it achieves the growth of semi-polar surfaces in localized areas through patterning and lateral epitaxy on low-cost, large-size conventional substrates. This makes high-performance semi-polar surface devices compatible with existing mature c-plane GaN epitaxial production lines, significantly reducing manufacturing costs and providing a cost-effective and feasible path for the commercial application of semi-polar surface GaN light-emitting devices. Attached Figure Description

[0021] Figure 1 A cross-sectional view of an epitaxial wafer for a semi-polar light-emitting device is disclosed. Figure 2 A cross-sectional view of a semi-polar light-emitting device is disclosed; Figure 3 A three-dimensional view of a semi-polar light-emitting device is disclosed; Figure 4 A three-dimensional magnified view of a semi-polar light-emitting device is disclosed; Figure 5 A cross-sectional view of a single semi-polar light-emitting device has been disclosed. Figure 6 A flowchart of a method for fabricating a semi-polar gallium nitride laser is disclosed; Figure 7 A flowchart of a method for fabricating a semi-polar gallium nitride light-emitting diode is disclosed.

[0022] Reference numerals: First substrate: 1; Second substrate: 2; Ridge structure: 11; Wing structure: 12; Device layer: 3; Electron providing layer: 31; Active region: 32; Hole providing layer: 33; Mask layer: 4; Strip mask: 41; N-type electrode: 51; P-type electrode: 52. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Most GaN-based light-emitting devices in the industry are epitaxially grown along the

[0001] direction (i.e., the polarization direction) on heterogeneous or homogeneous substrates. This polar c-plane GaN exhibits significant spontaneous polarization and piezoelectric polarization effects, leading to a strong built-in electric field (quantum confinement Stark effect, QCSE) within the active region of the quantum well. This electric field tilts the energy band of the quantum well, causing spatial separation of the wave functions of electrons and holes, resulting in reduced radiative recombination efficiency. This effect intensifies with increasing injection current and is one of the main causes of the "efficiency doop" problem in LED devices. For lasers, the energy band tilt (QCSE) caused by the polarization electric field leads to a "redshift" of the effective emission wavelength of the quantum well, reduced optical gain, and increased threshold current.

[0025] Therefore, based on the above problems, the present invention provides a semi-polar light-emitting device and its fabrication method. The core of the method is: on a conventional substrate, a gallium nitride substrate with a semi-polar slope is grown by patterning mask and epitaxial technology, and the structure of the light-emitting device is directly epitaxially grown on the semi-polar slope of this substrate, thereby effectively suppressing the quantum confinement Stark effect.

[0026] Example 1: A method for fabricating a semi-polar substrate laser The fabrication steps of the semi-polar substrate laser in this embodiment are as follows: Figure 6 As shown.

[0027] S100: A mask layer 4 is prepared on the second substrate 2.

[0028] A second substrate 2 is provided, and the material of the second substrate 2 can be GaN, sapphire, Si, SiC, GaAs or InP.

[0029] In some embodiments, before growing the first substrate 1 on the second substrate 2, a buffer layer may be grown on the second substrate 2 to solve problems such as lattice compatibility, stress buffering and / or thermal mismatch between the first substrate and the second substrate. For example, if the second substrate is Si and the first substrate is GaN, AlN may be deposited on the second substrate first to solve the lattice mismatch and thermal mismatch between the first substrate 1 and the Si material.

[0030] A mask layer 4 is grown on the second substrate 2 (if a buffer layer was grown on the second substrate 2 in the previous step, the mask layer 4 is grown on the buffer layer). For example, a thin film of about 50 nm thickness composed of one or more of SiO or SiNx is grown as the mask layer 4 by plasma-enhanced chemical vapor deposition (PECVD).

[0031] Then, periodic window patterns are etched onto the mask layer 4, such as... Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the mask layer 4 includes multiple parallel strip masks 41 arranged at equal intervals. A strip window is formed between adjacent strip masks 41 to expose the second substrate 2. The strip window exposes the second substrate 2 or the buffer layer below.

[0032] The width of the strip window directly determines the initial width of the ridge structure 11 of the first substrate 1 that is subsequently grown. The width of the ridge structure 11 will affect the slope angle and slope width of the wing structure 12 during the subsequent lateral growth.

[0033] The material of the first substrate 1 can be GaN, AlN, InN, AlGaN, InGaN, or AlInGaN. The following description will use GaN as the material of the first substrate 1.

[0034] Under specific growth conditions (V / III ratio, temperature), the wider the strip window, the gentler the slope of the top of the grown wing-shaped structure 12 (the smaller the angle with the substrate), and the wider the lateral dimension of the slope region. Therefore, it is necessary to match the specific semi-polar crystal plane of the target growth (such as the {10-11} or {20-21} plane, each with a fixed crystal angle), and ensure a sloped platform with a sufficiently large effective area for subsequent epitaxial high-quality active regions.

[0035] The spacing between the strip masks 41 can be configured to be 10-100 μm, and the width of the strip mask 41 can be configured to be 100-500 μm.

[0036] In addition, the center-to-center spacing between the strip masks 41 of the mask layer can be greater than the width of the wing structure 12 of the first substrate 1, so as to avoid the connection and merging of the wing structures of adjacent light-emitting devices during the epitaxial process.

[0037] The first substrate 1 includes a ridge structure 11 and a wing structure 12 formed on the top of the ridge structure 11. The first substrate 1 can be an N-type substrate, i.e., silicon-doped gallium nitride. The N-type electrode 51 can be disposed on the first substrate, which can reduce resistance and generate more electrons, thereby improving the performance of the light-emitting device. The subsequent steps are described in detail and will not be repeated here.

[0038] S200: The first substrate 1 is grown longitudinally within the strip window to form a ridge structure 11.

[0039] First, longitudinal growth is performed in a low-temperature nucleation stage. Nucleation points for the first substrate 1 are formed on the surface of the substrate or buffer layer exposed by the window of the mask layer 4. Then, island-shaped atomic clusters are formed around the nucleation points. Afterward, the temperature is increased, and growth is carried out under GaN material growth parameters. Under these conditions, the first substrate 1 mainly starts from the windowed area (exposed polar surface substrate) of the SiO2 mask (mask layer 4) and grows longitudinally along the c-axis

[0001] direction within the windowed area. Growth continues until the height of the GaN pillars is slightly higher than the thickness of the mask layer 4, for example, 0.5-2 micrometers higher, forming a ridge structure 11, such as... Figure 1 , Figure 2 and Figure 4 As shown.

[0040] S300: It grows laterally from the top of the ridge structure 11 towards the mask to form the wing structure 12.

[0041] The second step involves oblique lateral growth, using lateral epitaxy (ELOG technology). The growth conditions are dynamically adjusted; for example, compared to the conditions during longitudinal growth, the V / III ratio can be reduced, the growth temperature slightly increased, and the pressure increased.

[0042] Under these conditions, the growth kinetics of the first substrate 1 change. When the longitudinal growth front extends beyond the mask window edge, growth no longer primarily occurs along the c-plane, but preferentially extends laterally along certain semi-polar crystal planes with faster growth rates, such as the {10-11} or {20-21} planes. From the top of each GaN pillar, GaN grows rapidly outward and obliquely upward along a pair of symmetrical semi-polar planes. Ultimately, as... Figure 1 , Figure 2 As shown, above a single window, a wing-like structure 12 with a flat, sloping top is formed on the ridge structure 11 of the first substrate. This wing-like structure 12 has inclined sidewalls extending from the top centerline to both sides. The upper surfaces of the two inclined sidewalls are semi-polar planes, such as {10-11} planes, {20-21} planes, or {11-22} planes, etc., which are not limited in this invention. The inclined sidewalls formed above all windows have the same crystal orientation, forming a continuous platform composed of regular semi-polar inclined planes on the entire substrate. Each wing-like structure 12 includes two semi-polar inclined planes, one on the left and one on the right.

[0043] Furthermore, different growth parameters can be set for oblique lateral growth depending on the required semi-polarity surface. For example, when growing the {10-11} surface, the growth temperature is 950-1000℃, the reaction chamber pressure is 300-500 Torr, and the V / III ratio is 80-120; when growing the {11-22} surface, the growth temperature is 950-975℃, the reaction chamber pressure is 80-500 Torr, and the V / III ratio is 120-180.

[0044] S400: The device layer 3 of the laser is epitaxially grown on the semi-polar inclined surface of the wing structure 12. The device layer 3 of the laser is epitaxially grown on the two semi-polar inclined surfaces of the wing-shaped structure 12 formed in step S300, and the following laser structures are grown sequentially: The lower confinement layer, such as growing a Si-doped n-AlGaN layer, is used to confine the optical field and charge carriers within the active region.

[0045] The lower waveguide layer, for example, a 100nm thick layer of unintentionally doped GaN, is used to guide the optical mode.

[0046] The lower confinement layer and the lower waveguide serve as electron supply layers 31, used to supply electrons.

[0047] An active region 32 is grown, which can be a multi-quantum-well active region 32. For example, 5-10 cycles of InGaN / GaN multi-quantum-wells are grown, with the InGaN quantum well thickness being 2-5 nm and the GaN quantum barrier thickness being 5-15 nm. Since the growth surface is a semi-polar surface, the polarization electric field within the quantum well is greatly weakened, and the indium composition of the quantum well layer can be increased; for example, the quantum well layer can be In0. 30 Ga0. 70 N.

[0048] An upper waveguide layer, such as an unintentionally doped GaN layer, is used to guide the optical mode.

[0049] Electron blocking layers, such as Mg-doped p-AlGaN layers, are used to prevent electron leakage.

[0050] Upper confinement layer: For example, growing a Mg-doped p-AlGaN layer to confine the optical field and charge carriers within the active region.

[0051] Among them, the electron blocking layer and the upper confinement layer serve as hole-providing layers 33, providing holes.

[0052] At this time, the device layer 3 that has grown is as follows Figure 1As shown, device layer 3 is grown on the two semi-polar surfaces of the wing-shaped structure 12, appearing triangular when viewed from the front. Subsequent etching steps can further etch the contact area between the two device layers 3 until the first substrate 1 is exposed, ensuring that the active regions 32 of device layer 3 on the two semi-polar surfaces are electrically insulated from the hole-providing layer 33, as shown. Figure 2 As shown, the subsequent steps are explained in detail, and will not be repeated here.

[0053] It should be noted that in conventional polarized substrate schemes, to fabricate light-emitting devices with longer wavelengths, it is often achieved by increasing the In content in the InGaN / GaN quantum well. However, increasing the In content not only increases the lattice mismatch (thus increasing piezoelectric polarization), but also changes the spontaneous polarization characteristics of the material itself. The combination of these two factors results in an extremely strong polarization electric field in the high In content quantum well, leading to a severe quantum confinement Stark effect.

[0054] In this embodiment of the invention, the device layer is grown on a semi-polar surface, and the growth direction is at a certain angle to the polarization direction, thereby weakening and effectively suppressing the quantum confinement Stark effect (QCSE), thus breaking through the "green gap" and realizing a high-efficiency green light or even yellow-orange light laser.

[0055] S500: Photolithography, etching, fabrication of laser electrodes, and cleavage of cavity surfaces After the laser structure is grown, photolithography and etching processes are required to form the laser's electrodes and other structures.

[0056] Cleaning. Remove particulate matter, organic matter, inorganic impurities, and oxide layers from the surface of the wafer (the wafer refers to an epitaxial wafer prepared using the above-mentioned masking technology and on which a high-quality GaN material structure required for the laser has been grown).

[0057] After completing the growth of the laser epitaxial structure (including electron-providing layer 31, active region 32, hole-providing layer 33, etc.), the following is obtained: Figure 1 The structure shown is such that, at this time, the device layer 3 continuously covers the entire semi-polar inclined surface formed by the first substrate 1, and the wing-shaped structure 12 of the first substrate 1 has an isosceles triangular cross-section.

[0058] Subsequent etching steps can also etch the contact area between the two device layers 3 until the first substrate 1 (the first substrate 1 is an N-type substrate) is exposed, and the exposed first substrate 1 is used as the area for setting the N-type electrode, as follows: Photoresist coating and exposure: Photoresist is spin-coated onto the surface of the epitaxial wafer, and then exposure is performed using a photomask. The photomask is designed in a strip shape, and its position is aligned with the center line of the lower wing-shaped structure 12, that is, aligned with the connection between the device layers on the two lower semi-polar inclined surfaces.

[0059] Development: After development, an open strip window is formed on the photoresist, which fully exposes the area where the two device layers 3 below need to be etched away.

[0060] Etching enables device isolation and platform shaping: a continuous device structure is divided into two parts to form a shared mechanical support platform.

[0061] Etching is performed using a photoresist strip window as a mask. For example, dry etching can be used, with chlorine-based gases (such as Cl2 / BCl3) or a mixture of chlorine-based gases and argon as the etching gas.

[0062] The etching first penetrates the uppermost hole-providing layer 33, the multi-quantum-well active region 32, and the electron-providing layer 31, and continues downwards to the first substrate 1, etching the first substrate 1 but not exceeding it. Figure 2 As shown, the goal is to expose the first substrate 1 and to deposit an insulating layer at the etched area of ​​the platform to ensure that the hole-providing layer 33 and the active region 32 at the top are electrically isolated, forming two separate light-emitting device units on the left and right, each containing its own independent pn junction and active region 32.

[0063] like Figure 2 As shown, the etched first substrate 1 is exposed, forming a shared, platform-shaped electrical contact layer. This platform is the area for subsequent fabrication of the common n-type electrode. The p-type regions and active regions 32 of the two laser units are etched and isolated, electrically insulated from each other. However, they are electrically connected on the n-side through the shared n-type platform and the shared substrate below. At this time, the first substrate 1 can also act as an electron-providing layer to provide electrons. This structure enables the integrated device application where two light-emitting device units share the same n-electrode.

[0064] This etching scheme allows for the fabrication of two parallel laser units on a single substrate through a single epitaxial growth and subsequent patterning, achieving a high level of integration. The etching ensures electrical isolation of the active region 32, effectively preventing crosstalk between units. Simultaneously, the shared n-type platform and substrate provide an excellent heat dissipation path.

[0065] It is understandable that by also using the first substrate 1 as an electron-providing layer, the number of electrons can be increased, the recombination process of electrons and holes in the active region can be strengthened, and the large volume of the first substrate 1 can reduce resistance and improve the performance of the light-emitting device.

[0066] This embodiment of the invention also includes ridge etching. The upper confinement layer and upper waveguide layer in the hole-providing layer 33 are etched to form ridge strips, for example, by ultraviolet lithography and ICP etching to form ridge strips with a width of 2µm-50µm. This is shallow etching, with the etching depth approaching that of the quantum well, but without damaging it. Specifically, the process includes spin coating, photolithography, development, fixing, hardening, ICP etching, and resist removal to form the ridge strips.

[0067] A p-type electrode 52 is formed on the ridge strip. For example, a window with a width of approximately 2–4 μm is first etched on the ridge strip using ICP. Then, a Ni / Au thin electrode (or a Pd / Pt metal electrode, or ITO indium tin oxide) is evaporated using an electron beam as the contact electrode for hole injection. The alloy is then annealed in an O2 atmosphere to form an ohmic contact, ultimately forming the p-type electrode 52. Figure 2 As shown, the hole-providing layers 33 of the two device layer structures on the two semi-polar inclined surfaces of the same substrate both include p-shaped electrodes 52.

[0068] like Figure 5 As shown, an n-type electrode 51 is formed on the n-type electrode contact region formed in the above steps. For example, an n-type ohmic electrode 51 of the Ti / Al / Ni / Au system is fabricated by evaporation and stripping processes. This electrode 51 simultaneously provides electron injection for two laser units. Specifically, a Ti / Al / Ti / Au multilayer metal is used as the contact electrode for the electron injection end by electron beam evaporation, and good ohmic contact is formed by alloy annealing in an N2 atmosphere.

[0069] In some embodiments, the n and p electrodes can be thickened. Thicker electrodes provide better heat dissipation and wire bonding packaging; therefore, it is necessary to thicken both the electron and hole injection electrodes simultaneously. It is important to note that the thickened electrode must have good adhesion to the original electrode to prevent electrode detachment during subsequent packaging.

[0070] It is also necessary to cleave along the specific crystal orientation of the gallium nitride crystal to form a smooth laser resonator mirror surface, and to deposit a partial reflective film (e.g., reflectivity of 30%) on the front cavity surface and a high reflective film (e.g., reflectivity >95%) on the rear cavity surface.

[0071] In some embodiments, the dicing method may involve a hidden cut followed by dicing, and then subsequent processes such as grinding, polishing, cutting, sorting, and other standard packaging processes to fabricate a laser, such as... Figure 5 As shown.

[0072] Example 2: A method for fabricating a semi-polar substrate light-emitting diode The fabrication steps of the semi-polar substrate light-emitting diode in this embodiment are as follows: Figure 7As shown. In this embodiment, the steps for preparing the semi-polar gallium nitride substrate are the same as in Example 1. In both cases, GaN is laterally grown on the second substrate 2 by designing periodic alternating SiO2 masks to obtain the first substrate 1, and finally a wing-shaped structure with a semi-polar upper surface is obtained. For details, refer to steps S100-300 of Example 1.

[0073] S600: A device layer for growing light-emitting diodes is epitaxially grown on a semi-polar inclined surface of a wing-shaped structure.

[0074] The following structures are grown sequentially on the two semi-polar surfaces of the wing-like structure: Electron-providing layer: A Si-doped n-GaN layer is grown.

[0075] Active region: The active region 31 is grown. The active region can be multiple InGaN / GaN quantum wells with multiple periods. Since the growth surface is a semi-polar surface, the polarization electric field in the quantum well is greatly weakened, and the indium composition of the quantum well layer can be increased. For example, the quantum well layer can be In0. 30 Ga0. 70 N.

[0076] Electron blocking layers, such as Mg-doped p-AlGaN layers, are used to suppress electron leakage.

[0077] Hole-providing layer: A Mg-doped p-GaN layer is grown to provide holes.

[0078] In this embodiment of the invention, the device layer is grown on a semi-polar surface, and the growth direction is at a certain angle to the polarization direction, thereby weakening and effectively suppressing the quantum confinement Stark effect (QCSE), providing a possibility for solving the "efficiency droop" problem of light-emitting diode devices.

[0079] S700: Photolithography, Electrode Fabrication and Packaging Processes After completing the growth of the light-emitting diode epitaxial structure (including electron-providing layer 31, active region 32, hole-providing layer 33, etc.), the following is obtained: Figure 1 The structure shown is such that, at this time, the device layer 3 continuously covers the entire semi-polar inclined surface formed by the semi-polar gallium nitride substrate 1, and the wing-shaped structure 12 of the semi-polar gallium nitride substrate 1 has an isosceles triangular cross-section.

[0080] The etching step also requires etching the contact area between the two device layers 3, etching down to the exposed electron-providing layer 31, so that the active regions 32 of the device layers 3 on the two half-polar surfaces are electrically insulated from the hole-providing layer 33, and the electron-providing layer 31 is electrically connected, such as... Figure 2 As shown, please refer to the description of Example 1, which will not be repeated here.

[0081] A transparent conductive layer is prepared by depositing an indium tin oxide thin film on the surface of the hole-providing layer as a transparent conductive layer, and then performing an annealing treatment to optimize the ohmic contact.

[0082] Electrode fabrication: p-type electrodes were fabricated on ITO, and n-type electrodes were fabricated on exposed n-GaN. The electrode material was a Cr / Pt / Au stack.

[0083] Subsequent processes include grinding, polishing, cutting, and sorting, all part of standard chip packaging technology, to produce light-emitting diodes.

[0084] Example 3: A semi-polar light-emitting device like Figure 5 As shown, the semi-polar light-emitting device includes: The system comprises a first substrate 1, a second substrate 2, and a device layer 3. The first substrate 1 is grown on the second substrate 2 and includes a ridge structure 11 and a wing structure 12 formed on top of the ridge structure 11. The upper surface of the wing structure 12 is a semi-polar surface. The material of the second substrate 2 is GaN. The material of the second substrate 2 can be GaN, sapphire, Si, SiC, GaAs, or InP. The device layer 3 is grown on the upper surface of the wing structure 12 and, from bottom to top, includes at least an electron-providing layer 31, an active region 32 including at least one quantum well, and a hole-providing layer 33.

[0085] In this embodiment of the invention, the light-emitting device may further include a mask layer 4, which is composed of one or more of SiO or SiNx. The mask layer 4 is located on the second substrate 2 and includes two parallel strip masks 41. A strip window exposing the substrate is formed between the two strip masks 41, and the strip window exposes the underlying second substrate 2.

[0086] The first substrate 1 grows longitudinally along the strip window to form a ridge structure 11, and grows laterally above the mask layer 4 to form a wing structure 12.

[0087] Those skilled in the art will understand that the second substrate 2 can be peeled off according to actual conditions, such as laser peeling, and the present invention does not limit this.

[0088] It should be noted that the semi-polar light-emitting device in the embodiments of the present invention can be a laser, in which case the device layer 3 includes, from bottom to top: The lower confinement layer, such as growing a Si-doped n-AlGaN layer, is used to confine the optical field and charge carriers within the active region.

[0089] The lower waveguide layer, for example, a 100nm thick layer of unintentionally doped GaN, is used to guide the optical mode.

[0090] The lower confinement layer and the lower waveguide serve as electron supply layers 31, used to supply electrons.

[0091] An active region 32 is grown, which can be a multi-quantum-well active region 32. For example, 5-10 cycles of InGaN / GaN multi-quantum-wells are grown, with the InGaN quantum well thickness being 2-5 nm and the GaN quantum barrier thickness being 5-15 nm. Since the growth surface is a semi-polar surface, the polarization electric field within the quantum well is greatly weakened, and the indium composition of the quantum well layer can be increased; for example, the quantum well layer can be In0. 30 Ga0. 70 N.

[0092] The upper waveguide layer, for example, is a layer of GaN grown without intentional doping.

[0093] Electron blocking layers, such as Mg-doped p-AlGaN layers.

[0094] Upper confinement layer: For example, growing a Mg-doped p-AlGa0N layer.

[0095] The semi-polar light-emitting device in this embodiment of the invention can also be a light-emitting diode, in which case the device layer from bottom to top includes: Electron-providing layer: A Si-doped n-GaN layer is grown.

[0096] Active region: The active region 31 is grown. The active region can be multiple InGaN / GaN quantum wells with multiple periods. Since the growth surface is a semi-polar surface, the polarization electric field in the quantum well is greatly weakened, and the indium composition of the quantum well layer can be increased. For example, the quantum well layer can be In0. 30 Ga0. 70 N.

[0097] Electron blocking layers, such as Mg-doped p-AlGaN layers, are used to suppress electron leakage.

[0098] Hole-providing layer: Growing a Mg-doped p-GaN layer.

[0099] In embodiments of the present invention, such as Figure 1 , Figure 2 As shown, etching can also be performed on the connection points of device layers 3 on both sides of the wing-shaped structure 12. The etching first penetrates the uppermost p-type GaN layer and the multi-quantum-well active region 32, and continues downwards to the first substrate 1, etching the first substrate 1, but not exceeding the first substrate 1, as shown. Figure 2 As shown, the goal is to expose the first substrate 1 and to deposit an insulating layer at the etched area of ​​the platform to ensure that the hole-providing layer 33 and the active region 32 at the top are electrically isolated, forming two separate light-emitting device units on the left and right, each containing its own independent pn junction and active region 32.

[0100] like Figure 2As shown, the etched first substrate 1 is exposed, forming a shared, platform-shaped n-type electrode contact region, which is the region of the common n-type electrode 51. The p-type regions and active regions 32 of the two laser units are etched and isolated, electrically insulated from each other, and the p-type electrodes of the laser units are located in the hole-providing layer. However, they are electrically connected on the n-side through the shared n-type platform and the shared substrate below. This structure enables the integrated device application of two light-emitting device units sharing the n-electrode.

[0101] Advantages of this invention: In this invention, the active region of the device is located in a semi-polar plane with a low polarization electric field, thereby achieving higher internal quantum efficiency and lower efficiency degradation than conventional polar plane (c-plane) devices, which is beneficial for the realization of high-performance green lasers.

[0102] Solving QCSE at its source: The polarization electric field is weakened directly on the active region of the device by growing a semi-polar surface, which fundamentally improves the luminous efficiency.

[0103] Compatible with mainstream processes: It can be implemented directly on a general polar surface substrate without the need for expensive semi-polar bulk substrates, resulting in significant cost advantages.

[0104] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A semi-polar light-emitting device, characterized in that, include: A first substrate includes a ridge structure and a wing structure formed on top of the ridge structure, the wing structure having inclined sidewalls extending from its top centerline to both sides, the inclined sidewalls being semi-polar surfaces. The device layer, grown on the inclined sidewall of the wing-shaped structure, includes, from bottom to top, at least an electron-providing layer, an active region including at least one quantum well, and a hole-providing layer.

2. The semi-polar light-emitting device according to claim 1, characterized in that, It also includes a second substrate, on which the first substrate is grown.

3. The semi-polar light-emitting device according to claim 2, characterized in that, Also includes: A mask layer disposed on the second substrate, comprising at least two parallel strip masks, wherein a strip window exposing the second substrate is formed between the at least two strip masks; The ridge structure fills the strip window, and the wing structure is located on top of the ridge structure and extends to both sides to cover part of the mask layer.

4. The semi-polar light-emitting device according to claim 2, characterized in that, The material of the first substrate is GaN, AlN, InN, AlGaN, InGaN, or AlInGaN, and the material of the second substrate is GaN, sapphire, Si, SiC, GaAs, or InP.

5. The semi-polar light-emitting device according to claim 1, characterized in that, The first substrate is an N-type substrate, and the top of the semi-polar light-emitting device is exposed above the first substrate. The exposed area of ​​the first substrate is used to set the N-type electrode.

6. The semi-polar light-emitting device according to claim 5, wherein the hole-providing layer and the active region are physically isolated to define at least two independent light-emitting units, the at least two independent light-emitting units sharing the first substrate and the N-type electrode, the first substrate providing electrons for the at least two independent light-emitting units.

7. A method for fabricating a semi-polar light-emitting device, characterized in that, Includes the following steps: A mask layer is prepared on a second substrate, the mask layer comprising at least two parallel strip masks arranged at equal intervals, and a strip window is formed between adjacent strip masks to expose the substrate, the strip window exposing the second substrate below; In the substrate area exposed by the strip window, a first substrate is formed by longitudinal growth, and the first substrate is grown vertically upward until it fills the window and covers the sidewall of the strip mask, forming a ridge structure. After the first substrate extends beyond the strip window, the growth process parameters are changed so that the first substrate grows laterally from the top of the ridge structure to above the mask. The growth conditions are controlled so that the semi-polar surface is exposed and expanded as a stable growth surface, thereby forming a wing structure on the first substrate. The wing structure has inclined sidewalls extending from its top centerline to both sides, and the inclined sidewalls are semi-polar surfaces. A device layer comprising at least an electron-providing layer, an active region comprising at least one quantum well, and a hole-providing layer is epitaxially grown on the inclined sidewall of the wing-shaped structure.

8. The preparation method according to claim 7, characterized in that, The spacing between adjacent strip masks in the mask layer is configured to be 10-100 μm, and the width of the strip mask is configured to be 100-500 μm.

9. The preparation method according to claim 7, characterized in that, The first substrate is an N-type substrate, and the fabrication method further includes: longitudinally etching the light-emitting device to expose the first substrate, and fabricating an N-type electrode in the exposed area of ​​the first substrate.

10. The preparation method according to claim 9, characterized in that, Also includes: The light-emitting device is longitudinally etched to physically and electrically isolate the hole-providing layer and the active region, thereby defining at least two independent light-emitting units that share the first substrate and an N-type electrode. The first substrate provides electrons to the at least two independent light-emitting units.

11. The preparation method according to claim 10, characterized in that, Also includes: A P-type electrode is prepared on the surface of the hole-providing layer of the at least two independent light-emitting units.

12. The preparation method according to claim 7, characterized in that, The spacing between adjacent strip masks in the mask layer is greater than the width of the wing-shaped structure of the semi-polar surface nitride substrate.

13. The preparation method according to claim 7, characterized in that, The material of the first substrate is GaN, AlN, InN, AlGaN, InGaN, or AlInGaN, and the material of the second substrate is GaN, sapphire, Si, SiC, GaAs, or InP.

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