Deep ultraviolet led device with wave vector regulation and method of manufacturing the same

Abstract

The application discloses a device structure for improving light-emitting efficiency of an AlGaN deep ultraviolet LED based on wave vector regulation and a preparation method thereof. The device comprises a light-transmitting substrate, a first semiconductor layer, a quantum well layer, a second semiconductor layer, an electrode contact layer, a reflection layer, and electrodes in contact with the first semiconductor layer and the second semiconductor layer respectively, and the second semiconductor layer and the electrode contact layer are etched with periodic or random distributed slot holes in which the reflection layer is embedded, the reflection metal embedded in the slot holes of the second semiconductor layer has plasmonic resonance characteristics in the deep ultraviolet light region, and the structure can realize regulation of high Al component AlGaN quantum well photon propagation modes, and based on wave vector regulation, the light-emitting efficiency of TM and TE mode radiation photons is significantly improved. The medium layer with a specific thickness and a low refractive index mainly plays a role of an optical cavity and assists in improving plasmonic resonance of the reflection metal and wave vector regulation ability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device fabrication technology, and in particular to a method for improving the light extraction efficiency of deep ultraviolet LEDs by modulating the wave vector of photons through plasmon microstructures, as well as a method for fabricating deep ultraviolet LED devices with this function. Background Technology

[0002] Currently, ultraviolet (UV) / deep ultraviolet (DUV) (200–340 nm) LED solid-state light sources, fabricated from third-generation wide-bandgap semiconductor materials gallium nitride (GaN), aluminum nitride (AlN), and their alloy aluminum gallium nitride (AlGaN), have broad application prospects in fields such as water and air purification, surface sterilization, ultraviolet lithography, non-line-of-sight communication, ultraviolet therapy, and ink curing due to their compact light source structure and environmentally friendly characteristics. However, unlike conventional blue-green light nitride LEDs which have achieved high external quantum efficiencies, the current photoelectric conversion efficiency of deep ultraviolet LEDs is generally below 10%, which greatly limits the application of deep ultraviolet solid-state light sources in the aforementioned fields.

[0003] For deep-ultraviolet (DLUV) LED quantum structures constructed from high-Al-content AlGaN materials, the increased Al content in the AlGaN quantum well semiconductor material exacerbates problems such as the increased difficulty of epitaxial growth of heterostructures and significant optical anisotropy. The polarization ratio changes of TE and TM photons generated by electron transitions from the conduction band bottom to the heavy / light hole valence band and crystal field splitting of the valence band intensify. The quantum well TM photon-dominated radiation mode severely limits the device's light extraction efficiency and output power. Furthermore, the commonly used P-type GaN ohmic contact layer in DUV LED devices, due to its small bandgap, severely absorbs the DUV light emitted from the AlGaN quantum well, preventing photons from escaping through the P-type electrode or after reflection by the reflecting electrode during device application. Therefore, designing novel micro / nano structures with photon transport manipulation capabilities and controlling photon transmission modes are crucial for improving the photon extraction efficiency of TE and TM modes in quantum structures and for fabricating high-efficiency DUV LED solid-state light source devices. Summary of the Invention

[0004] In view of the above problems, the present invention provides a deep ultraviolet LED device with a wave vector modulation structure and its fabrication method. By opening a hole in the second semiconductor layer and constructing a reflective metal microstructure with plasmonic resonance effect in the hole, the wave vector of the photons radiated by the quantum well is modulated by the plasmonic resonance and its associated dielectric cavity resonance, thereby improving the transmission form of the quantum well TM and TE mode photons and ultimately improving the light extraction efficiency of the quantum well radiated photons.

[0005] The technical solution of this invention is as follows:

[0006] A deep ultraviolet LED device with wave vector modulation has a device structure comprising, in sequence, a transparent substrate, a first semiconductor layer, a quantum well layer, a second semiconductor layer, an electrode contact layer, and a metal electrode. The metal electrode has a first electrode and a second electrode with opposite electrical polarities, which are respectively connected to the first semiconductor layer and the electrode contact layer. The electrode contact layer uniformly covers the surface of the second semiconductor layer. The second semiconductor layer and the electrode contact layer are etched with slots, and the slots are filled with a reflective layer. A dielectric layer is deposited between the reflective layer and the second semiconductor layer and the quantum well layer in the portion of the slot. A dielectric layer is provided to isolate the first electrode and the second electrode from the penetrating quantum well layer, the second semiconductor layer, and the electrode contact layer. A dielectric layer is provided between the first electrode and the second electrode and the electrode contact layer.

[0007] In some embodiments, the emission wavelength of the deep ultraviolet LED light-emitting device is no greater than 320nm.

[0008] In some embodiments, the second semiconductor layer is GaN, AlN, BN or an alloy thereof doped with Mg impurities.

[0009] In some embodiments, the diameter of the slot is 0.2 to 10.0 micrometers, and the diameter of the slot may be determined by a single parameter or a combination of multiple parameters.

[0010] In some embodiments, the cumulative area of ​​the slot in the opening region of the cross section perpendicular to the hole axial direction accounts for 1% to 90% of the area of ​​the second semiconductor layer.

[0011] In some embodiments, the etched slots of the second semiconductor layer and the transparent electrode contact layer are arranged in a periodic uniform array or at random locations.

[0012] In some embodiments, the sidewall of the slot makes an angle of 5 to 60 degrees with the normal to the surface of the second semiconductor layer, and the cross-section of the opening parallel to the hole axis has a trapezoidal structure.

[0013] In some embodiments, the reflective layer may extend between the electrode contact layer and the dielectric layer.

[0014] In some embodiments, the reflective layer is a reflective layer of one or more combinations of Al, Rh, Pt, or Ni.

[0015] In some embodiments, the reflective layer has a flat or uneven interface with the dielectric layer, and the height difference of the unevenness is no greater than 5 nm.

[0016] In some embodiments, the dielectric layer is one of SiO2, MgF2, Na3AlF6, and Al2O3.

[0017] In some embodiments, the thickness of the first dielectric layer is at least 5 nm and does not exceed the total thickness of the second semiconductor layer.

[0018] In some embodiments, the equivalent optical path length of the thickness of the first dielectric layer is an odd multiple of 1 / 4 wavelength.

[0019] This invention also provides a method for fabricating a deep ultraviolet LED device with wave vector modulation, which includes the following steps:

[0020] 1) Select a light-transmitting substrate, which includes a first surface side and a second surface side opposite to each other. A buffer layer, a first semiconductor layer, a quantum well layer, a second semiconductor layer, and a functional layer between each key layer are grown sequentially on the first surface side of the light-transmitting substrate to realize the deep ultraviolet emission function of the LED.

[0021] 2) Deposit an electrode contact layer on the surface of the second semiconductor layer;

[0022] 3) A mask is used to define the opening area on the surface of the transparent electrode, and the slot, the first dielectric layer and the reflective layer are sequentially etched to prepare the slot;

[0023] 4) Fabricate the first electrode, the second electrode, and other dielectric layers two and three that electrically isolate the electrodes from the surrounding semiconductor / conductor layers, and complete the semiconductor light-emitting sequence unitization to obtain a semiconductor light-emitting device.

[0024] In some embodiments, the above-described slot fabrication process includes, but is not limited to: depositing an electrode contact layer in a second semiconductor layer, etching a hole-like structure on its surface using semiconductor technology; then depositing a dielectric layer inside the hole; and finally depositing a reflective layer that is laid flat and embedded therein.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention utilizes a slot in the second semiconductor layer, within which a dielectric layer and a reflective metal are laid flat. The micron- or submicron-scale reflective metal structure within the slot, along with its associated dielectric layer, allows for the manipulation of the propagation wave vector of TM-mode photons radiated from the quantum well. By leveraging plasmon resonance and scattering effects to alter the original photon propagation mode, the emission efficiency of TM-mode radiated photons is improved. Furthermore, the relatively flat reflective film at the bottom of the slot can also reflect the TE mode, further enhancing the light extraction efficiency of the flip-chip device.

[0027] Compared to traditional reflective structures used in deep ultraviolet LEDs, this invention reduces the spatial distance between the reflective film and the quantum well radiating unit by creating an opening in the second semiconductor, thereby improving the efficiency of photon-induced plasmon resonance and reducing the absorption of quantum well radiated photons by the second layer. Furthermore, the micron- or submicron-scale non-planar reflective metal structure can utilize localized mode plasmon resonance to enhance the modulation of the TM mode and the excited propagation mode SPP, altering their photon transmission mode or propagation direction and promoting photon emission.

[0028] The present invention introduces a dielectric layer between the reflective layer and the second semiconductor layer or quantum well layer, which can suppress ohmic losses during plasmon resonance. Furthermore, the dielectric layer, composed of a low refractive index, forms a "sandwich" structure optical cavity in contact with the metal and nitride semiconductor, achieving improved optical reflection efficiency at a specific thickness. Here, the specific thickness refers to a preferred equivalent optical path length of the dielectric layer being an odd multiple of 1 / 4 wavelength.

[0029] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0030] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0031] Figure 1 This is a schematic diagram of the deep ultraviolet LED device structure with wave vector modulation provided in Example 1.

[0032] Figure 2 This is a partially enlarged schematic diagram of the device structure in Example 1, showing the openings in the second semiconductor layer and electrode contact layer, as well as the reflective electrode structure area.

[0033] Figure 3 A schematic diagram of a deep ultraviolet LED device using conventional reflective metal electrodes is provided for Comparative Example 1.

[0034] Figure 4 The diagram below is a schematic of a deep ultraviolet LED device with a flat embedded second semiconductor layer opening and a reflective metal filling structure, provided for Comparative Example 2.

[0035] Figure 5 This is a schematic diagram of the deep ultraviolet LED device structure with wave vector modulation provided in Example 2.

[0036] Figure 6 The local optical field distribution and light intensity distribution of the devices in Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0037] Figure 7 This is a comparison chart of the far-field angle resolved light intensity of devices in Example 1, Comparative Example 1, and Comparative Example 2.

[0038] The reference numerals in the detailed embodiments are as follows:

[0039] 100--Transparent substrate; 101--First semiconductor layer; 102--Quantum well layer; 103--Second semiconductor; 201--Electrode contact layer; 202--Dielectric layer three; 203--Metal electrode; 203-1--First electrode; 203-2--Second electrode; 301--Reflective layer; 302--Dielectric layer one; 401--Dielectric layer two. Detailed Implementation

[0040] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0042] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0043] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0044] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0045] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0046] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0047] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0048] Reference Figure 1 , 2As shown in Figure 5, a deep ultraviolet LED device with wave vector modulation has a device structure that sequentially includes a light-transmitting substrate 100, a first semiconductor layer 101, a quantum well layer 102, a second semiconductor layer 103, an electrode contact layer 201, and a metal electrode 203. The metal electrode 203 has a first electrode 203-1 and a second electrode 203-2 with opposite electrical polarities, and is respectively connected to the first semiconductor layer 101 and the electrode contact layer 201. The second semiconductor layer 103 and the electrode contact layer 201 are etched with slots, and the slots are filled with... A reflective layer 301 is provided, and a dielectric layer 302 is laid between the reflective layer 301 and the second semiconductor layer 103 and the quantum well layer 102. A dielectric layer 302 can also be provided between the region inside the slot and the electrode contact layer. A dielectric layer 401 is provided between the first electrode 203-1 and the second electrode 203-2 and the penetrating quantum well layer 102, the second semiconductor layer 103, and the electrode contact layer 201. A dielectric layer 202 is provided between the first electrode 203-1 and the second electrode 203-2 and the electrode contact layer 201.

[0049] The slot structure has a trapezoidal cross-section parallel to the hole axis. The embedded reflective layer 301 and dielectric layer 302 have the synergistic effect of plasmonic resonance and optical cavity resonance, which can realize the wave vector control function of photons emitted by the quantum well, thereby improving the light extraction efficiency of deep ultraviolet LED devices.

[0050] The first electrode 203-1 can be connected to or extend into the first semiconductor layer 101. This electrode contacts the N-type semiconductor and serves as the negative electrode of the diode. The second electrode 203-2 is connected through the electrode contact layer 201. Since the second semiconductor 103 typically has poor ohmic contact performance when in direct contact with a metal, a dedicated electrode contact layer 201 is needed as a transition. This electrode is the positive electrode. Both electrodes are located on one side of the device, facilitating the exit of photons emitted from the quantum well through the transparent substrate 100. When the first electrode 203-1 extends into the first semiconductor layer 101 for connection, a dielectric layer 401 is provided between the side of the first electrode 203-1 and the first semiconductor layer 101, so that the first electrode 203-1 only contacts the first semiconductor and needs to be insulated from other places through the 401 layer, which is an insulating dielectric layer; the second electrode 203-2 can extend into the electrode contact layer 201 for connection, and a dielectric layer 401 is provided between it and the reflective layer 301, so that the second electrode 203-2 deeply contacts 201, and the deep hole must also have 401 to avoid contact with the 301 reflective metal layer. The 301 metal is conductive, and contact in this place will cause the electrode to short-circuit with other places.

[0051] The function of dielectric layer 302 is, on the one hand, to serve as a surface passivation layer after the first semiconductor is etched, and on the other hand, to provide the effect of optical cavity resonance as a dielectric layer with a specific refractive index and a specific thickness; dielectric layer 401 is used to isolate the contact between the first electrode and the second electrode and the surrounding semiconductor layer, and serves as an electrical insulation barrier; dielectric layer 202 is used for electrical insulation barrier between the metal reflective layer and the first electrode and the second electrode.

[0052] In some embodiments, the emission wavelength of the deep ultraviolet LED light-emitting device is no greater than 320nm.

[0053] In some embodiments, the second semiconductor 103 layer is GaN, AlN, BN or an alloy thereof doped with Mg impurities.

[0054] In some embodiments, the diameter of the slot is 0.2 to 10.0 micrometers, and the diameter of the slot may be determined by a single parameter or a combination of multiple parameters.

[0055] In some embodiments, the cumulative area of ​​the cross-sectional opening region of the slot perpendicular to the hole axis accounts for 1% to 90% of the area in the two-dimensional plane of the second semiconductor 103 layer. If the proportion is too low, the desired effect of this application cannot be achieved; if it is too high, the second semiconductor 103 layer will have too few electrical contacts, resulting in uneven current spread and affecting the device performance.

[0056] In some embodiments, the etched slots of the second semiconductor 103 layer and the transparent electrode contact layer 201 are arranged in a periodic uniform array or at random locations.

[0057] In some embodiments, the trenches etched in the second semiconductor 103 layer and the electrode contact layer 201 are uniformly distributed on the side of the second semiconductor 103 layer.

[0058] In some embodiments, the sidewall of the slot is at an angle of 5 to 60 degrees to the surface normal of the second semiconductor 103 layer, and the cross-section of the opening parallel to the hole axis is trapezoidal; the overall shape is frustoconical.

[0059] The reflective layer 301 extends between the electrode contact layer 201 and the dielectric layer 401, which helps to improve the effective current injection and propagation at the contact between the second electrode 203-2 and the second semiconductor layer 103. This structure simplifies the device fabrication process (eliminating the need for additional etching of the metal outside the via), and the reflective metal is also conductive, which, when connected to the electrode contact layer 201, improves the current injection and propagation at the contact with the second semiconductor 103. No additional control is required in the fabrication process; only the following reflective metal characteristics are limited.

[0060] In some embodiments, the reflective layer is a reflective layer 301 consisting of one or more combinations of Al, Rh, Pt, or Ni.

[0061] In some embodiments, the reflective layer at its contact interface with the dielectric layer is either flat or uneven, with the height difference of the unevenness not exceeding 5 nm. The reflective layer can also be uneven in the electrode contact layer section. This refers to the bottom, sidewalls, or extended portions of the slot being macroscopically flat, but microscopically limited to being not too rough, i.e., the height of the unevenness not exceeding 5 nm. The diameter of the hole is on the order of several micrometers, and the deposited metal at the bottom, sidewalls, or extended portions of the hole is macroscopically flat, but microscopically the metal film has certain microscopic unevenness, which is limited to not exceeding 5 nm.

[0062] In some embodiments, a dielectric layer 302 is also laid between the reflective layer 301 and the electrode contact layer 201.

[0063] In some embodiments, the dielectric layer 302 is one of SiO2, MgF2, Na3AlF6, and Al2O3.

[0064] In some embodiments, the thickness of the dielectric layer 302 is at least 5 nm and does not exceed the total thickness of the second semiconductor layer 103.

[0065] In some embodiments, the equivalent optical path length of the dielectric layer 302 is an odd multiple of 1 / 4 wavelength. This dielectric layer serves to reduce losses during plasmon resonance on the reflective metal surface and acts as an optical resonant cavity to enhance the optical reflection effect of the reflective metal.

[0066] The reflective layer 301 and its contacting dielectric layer can generate plasmonic resonances at their interface under the excitation of quantum well TM mode radiated photons. These plasmonic resonance modes include typical propagating mode plasmons (SPPs) propagating along the surface of a flat metal thin film, and localized mode surface plasmons (LSPs) excited at uneven surfaces or structural edges. The excited localized mode surface plasmon (LSP) resonance can change the propagation direction of incident photons based on scattering effects; the propagating mode surface plasmons (SPPs) generated by the excitation of the reflective metal thin film can also cause changes in photon transmission mode and emission angle due to changes in the aperture structure boundary or the microscopic unevenness of its surface. Due to the plasmonic resonance of these two modes and their modulation of photon transmission, the TM mode photons radiated by the quantum well acquire a change in wave vector, making them easier to emit. The dielectric layer, due to its low refractive index and low absorption characteristics for deep ultraviolet photons, can utilize the optical field compression effect to reduce the ohmic loss during the aforementioned plasmonic resonances.

[0067] In addition, the FP optical cavity effect formed by the dielectric layer of a certain thickness can also improve the deep ultraviolet light reflection effect of the reflective layer 301. In particular, for TE mode photons radiated by quantum wells, optical reflection occurs when they irradiate the reflective metal laid flat in the opening, which is used to improve the light extraction efficiency of TE mode photons from the transparent substrate side.

[0068] This invention also provides a method for fabricating a deep ultraviolet LED device with wave vector modulation, which includes the following steps:

[0069] 1) Select a light-transmitting substrate 100, which includes a first surface side and a second surface side opposite to each other. A buffer layer, a first semiconductor layer 101, a quantum well layer 102, a second semiconductor layer 103, and a functional layer between each key layer are grown sequentially on the first surface side of the light-transmitting substrate 100 to realize the deep ultraviolet emission function of the LED.

[0070] 2) Deposit an electrode contact layer 201 on the surface of the second semiconductor 103 layer, preferably a transparent conductive electrode contact layer 201, but not limited to a transparent conductive electrode contact layer 201.

[0071] 3) A mask is used to define the opening area on the surface of the transparent electrode, and the slot, the deposited dielectric layer 302 and the reflective layer 301 are sequentially etched;

[0072] 4) Prepare the first electrode 203-1, the second electrode 203-2, and other dielectric layers 401 and 402 that electrically isolate the electrodes from the surrounding semiconductor / conductor layers, and complete the semiconductor light-emitting sequence unitization to obtain a semiconductor light-emitting device.

[0073] In some embodiments, the above-described via fabrication process includes, but is not limited to: depositing an electrode contact layer 201 on the second semiconductor 103 layer, etching a hole-like structure on its surface using semiconductor technology; then, depositing a dielectric layer within the hole to passivate the area where the second semiconductor 103 and the quantum well are in contact; and finally depositing a reflective layer 301, which is then embedded therein. The reflective metal may cover only the location of the hole or cover the entire surface of the electrode contact layer 201. If it only covers the location of the hole, the reflective metal only serves a primary reflective function. If it covers the entire surface of the electrode contact layer 201, the high conductivity of the reflective metal itself can be utilized to help improve the current spreading characteristics of the second electrode 203-2 when charge is injected.

[0074] Example 1:

[0075] This invention provides a deep ultraviolet LED device with wave vector modulation function and its fabrication method, belonging to the field of LED light emission technology. Figure 1As shown, the device structure, from top to bottom, includes: a transparent substrate 100, a first semiconductor layer 101, an AlGaN quantum well layer 102, a second semiconductor layer 103, an electrode contact layer 201, a reflective layer 301, and metal electrodes 203 with opposite electrical properties that are in contact with the first semiconductor layer 101 and the second semiconductor layer 103, respectively. The second semiconductor layer 103 has micrometer-scale slots, the reflective layer 301 extends to the bottom of the slots, and a dielectric layer 302 exists between the reflective layer 301, the second semiconductor layer 103, and the quantum well.

[0076] In this embodiment, the light-transmitting substrate 100 is a commonly used sapphire substrate. After epitaxially growing functional layers such as buffer layers on it, a relatively thick N-type AlGaN first semiconductor layer 101 doped with Si is sequentially epitaxially grown, followed by 10 cycles of Al... 0.4 Ga 0.6 N / A l 0.6 Ga 0.4 The N quantum well layer is 102 nm thick, and the Al layer is 30 nm thick. 0.75 Ga 0.15 The N-electron blocking layer and the second semiconductor layer 103. In this embodiment, the second semiconductor layer 103 is a P-type GaN layer doped with Mg impurities, with a thickness of 30 nm.

[0077] In the device fabrication process, firstly, MESA mesa is created on the epitaxial layer to define the first electrode 203-1 region and the second electrode 203-2 region. Then, an electrode contact layer 201 is deposited on the surface of the second semiconductor 103 layer. The transparent electrode contact layer 201 is made of transparent conductive ITO material. Next, a trench array is etched on the electrode contact layer 201 and the second semiconductor 103 layer using micro-nano fabrication techniques. The etching depth is close to the thickness of the second semiconductor 103 layer, and the diameter of the trench is 5 micrometers. By controlling the etching process, the sidewalls of the trenches have a certain tilt angle, approximately 30 degrees. The trenches are periodically arranged on the surfaces of the electrode contact layer 201 and the second semiconductor 103 layer, and the cumulative area of ​​the trenches accounts for 30% of the total area of ​​the second semiconductor 103 layer.

[0078] Subsequently, a medium layer of 302SiO2 with a thickness of 46 nm was deposited inside the pore.

[0079] Based on this, using a mask definition, the SiO2 layer covering the electrode contact layer 201 in areas other than the holes is removed. Then, using a mask definition, a reflective layer 301 Al thin film is deposited on the surface of the second semiconductor 103 layer, excluding the area of ​​the second electrode 203-2. The surface roughness of the Al thin film is approximately 3 nm. After metal deposition, the reflective metal fills the holes, and in its cross-section, the holes exhibit a trapezoidal structure, such as... Figure 2 As shown.

[0080] Finally, an electrode contact layer 201, consisting of a first electrode 203-1 and a second electrode 203-2, is deposited on the side of the second semiconductor layer near its outer surface. A PV protective layer isolates the metal electrode 203PAD region from the reflective metal. This process ultimately fabricates a typical flip-chip deep ultraviolet LED device.

[0081] Comparative Example 1:

[0082] This comparative example is a typical deep ultraviolet LED device using a conventional reflective metal electrode 203 and its fabrication method. For example... Figure 3 As shown, the device structure, from top to bottom, includes: a light-transmitting substrate 100, a first semiconductor layer 101, an AlGaN quantum well layer 102, a second semiconductor layer 103, an electrode contact layer 201, a reflective layer 301, and metal electrodes 203 with opposite electrical properties that are in contact with the first semiconductor layer 101 and the second semiconductor layer 103, respectively.

[0083] In this comparative example, the transparent substrate 100 is a commonly used sapphire substrate. After epitaxially growing a buffer layer and other functional layers on it, a relatively thick Si-doped N-type AlGaN first semiconductor layer 101 is sequentially epitaxially grown, followed by 10 cycles of Al... 0.4 Ga 0.6 N / A l 0.6 Ga 0.4 The N quantum well layer is 102 nm thick, and the Al layer is 30 nm thick. 0.75 Ga 0.15 The N-electron blocking layer and the second semiconductor layer 103. In this embodiment, the second semiconductor layer 103 is a P-type GaN layer doped with Mg impurities, with a thickness of 30 nm.

[0084] In the device fabrication process, firstly, MESA mesa is created on the epitaxial layer to define the first electrode 203-1 region and the second electrode 203-2 region. Then, an electrode contact layer 201 is deposited on the surface of the second semiconductor layer. The electrode contact layer 201 is made of a transparent and conductive ITO material. Subsequently, through mask definition, a reflective metal Al thin film is deposited on the surface of the electrode contact layer 201, except for the second electrode 203-2 region. The surface roughness of the Al thin film is approximately 3 nm.

[0085] Finally, an electrode contact layer 201, consisting of a first electrode 203-1 and a second electrode 203-2, is deposited on the side of the second semiconductor layer near its outer surface. A PV protective layer isolates the electrode PAD region from the reflective metal. This ultimately fabricates a typical flip-chip deep ultraviolet LED device.

[0086] Comparative Example 2:

[0087] This comparative example provides a deep ultraviolet LED device with a reflective metal surface and no dielectric layer, as well as its fabrication method. For example... Figure 4 As shown, the device structure, from top to bottom, includes: a transparent substrate 100, a first semiconductor layer 101, an AlGaN quantum well layer 102, a second semiconductor layer 103, an electrode contact layer 201, a reflective layer 301, and metal electrodes 203 with opposite electrical properties that are in contact with the first semiconductor layer 101 and the second semiconductor layer 103, respectively. The second semiconductor layer 103 has micrometer-scale openings, and the reflective layer 301 extends to the bottom of the openings. Compared to Example 1, this comparative example shows that the reflective structure formed by the openings has no dielectric layer between it and the second GaN and the quantum well, allowing for comparison of the modulation effect of the dielectric layer on the reflection effect.

[0088] In this comparative example, the light-transmitting substrate 100 is a commonly used sapphire substrate. After epitaxially growing functional layers such as buffer layers on it, a relatively thick N-type AlGaN first semiconductor layer 101 doped with Si is sequentially epitaxially grown, followed by 10 cycles of Al... 0.4 Ga 0.6 N / A l 0.6 Ga 0.4 The N quantum well layer is 102 nm thick, and the Al layer is 30 nm thick. 0.75 Ga 0.15 The N-electron blocking layer and the second semiconductor layer 103. In this embodiment, the second semiconductor layer 103 is a P-type GaN layer doped with Mg impurities, with a thickness of 30 nm.

[0089] In the device fabrication process, firstly, MESA mesa is formed on the epitaxial layer to define the first electrode 203-1 region and the second electrode 203-2 region. Then, an electrode contact layer 201 is deposited on the surface of the second GaN layer. The electrode contact layer 201 is made of a transparent and conductive ITO material. Subsequently, a micro-nano fabrication technique is used to etch a micro-hole array on the transparent electrode and the second GaN layer. The etching depth is close to the thickness of the second GaN layer, and the diameter of the micro-holes is 5 micrometers. By controlling the etching process, the sidewalls of the holes have a certain tilt angle, approximately 30 degrees. The micro-holes are periodically arranged on the surfaces of the transparent electrode layer and the second semiconductor 103, and the cumulative area of ​​the micro-holes accounts for 30% of the total area of ​​the second semiconductor 103 layer.

[0090] Based on this, a reflective metal Al thin film is deposited on the surface of the second semiconductor 103 layer, excluding the areas of the second and first electrodes 203-1, using a mask definition. The surface roughness of the Al thin film is approximately 3 nm. After metal deposition, the reflective metal fills the hole, and in its cross-section, the hole exhibits a trapezoidal structure.

[0091] Finally, a first electrode 203-1 and a second electrode 203-2 are deposited on the side of the second semiconductor layer near the outer surface, with a PV protective layer is used to isolate the electrode PAD region from the reflective metal. This ultimately fabricates a typical flip-chip deep ultraviolet LED device.

[0092] Example 1, Comparative Example 1, Comparative Example 2: Comparison of light extraction efficiency of three device structures:

[0093] Device Structure Example 1 Comparative Example 1 Comparative Example 2 Light output efficiency 11.3％ 6.6％ 4.8％

[0094] Figure 6 To calculate the local optical field distribution of the devices in Example 1, Comparative Example 1, and Comparative Example 2 under TM mode dipole excitation at a single wavelength of 275nm using finite element optical simulation, especially to show the light intensity distribution emitted to the transparent substrate 100 under the same dipole light source radiation for the three structures; it can be seen that, compared to the traditional flip-chip deep ultraviolet LED device structure with only metal reflective electrodes in Comparative Example 1, the light intensity emitted to the transparent substrate 100 is significantly increased after introducing an opening and embedding a reflective electrode in the second layer; when there is no dielectric layer to isolate the second layer opening and reflective metal in Comparative Example 2, the emitted light intensity is significantly reduced compared to the case with an isolation layer in Example 1.

[0095] Figure 7 To calculate the far-field angularly resolved light intensity of the devices in Example 1 and Comparative Example 2 under single TM mode dipole excitation at a wavelength of 275 nm using finite element optical simulation, the results show that, compared to the traditional flip-chip deep ultraviolet LED device structure in Comparative Example 1 with only a metal reflective electrode, the light intensity is significantly improved across almost all angle ranges after introducing an opening and embedding a reflective electrode in the second semiconductor layer. In Comparative Example 2, without a dielectric layer separating the opening in the second semiconductor layer from the reflective metal, the emitted light intensity is not as significantly higher than in Example 1 with an isolation layer. Based on the integral of the far-field emitted intensity, the light extraction efficiency of the three structures for TM mode radiated photons is listed in Table 1. It can be seen that Example 1 has the highest light extraction efficiency, followed by Comparative Example 2, and then Comparative Example 1.

[0096] Example 2:

[0097] As a variation of Example 1, the present invention also provides another deep ultraviolet LED device with wave vector modulation function and its fabrication method. Figure 5As shown, the device structure, from top to bottom, includes: a transparent substrate 100, a first semiconductor layer 101, an Al GaN quantum well layer 102, a second semiconductor layer 103, an electrode contact layer 201, a reflective layer 301, and metal electrodes 203 with opposite electrical properties that are in contact with the first semiconductor layer 101 and the second semiconductor layer 103, respectively. The second semiconductor layer 103 has micron-sized slots, the reflective layer 301 extends to the bottom of the slots, and a dielectric layer 302 exists between the reflective layer 301, the second semiconductor layer 103, and the quantum well.

[0098] Compared to Embodiment 1, in this embodiment, the reflective layer 301 exists only inside the slot and does not extend to the surface of the transparent conductive electrode film outside the slot.

[0099] In this embodiment, the light-transmitting substrate 100 is a commonly used sapphire substrate. After epitaxially growing functional layers such as buffer layers on it, a relatively thick N-type AlGaN first semiconductor layer 101 doped with Si is sequentially epitaxially grown, followed by 10 cycles of Al... 0.4 Ga 0.6 N / A l 0.6 Ga 0.4 The N quantum well layer is 102 nm thick, and the Al layer is 30 nm thick. 0.75 Ga 0.15 The N-electron blocking layer and the second semiconductor layer 103. In this embodiment, the second semiconductor layer 103 is a P-type GaN layer doped with Mg impurities, with a thickness of 30 nm.

[0100] In the device fabrication process, firstly, MESA mesa is created on the epitaxial layer to define the first electrode 203-1 region and the second electrode 203-2 region. Then, an electrode contact layer 201 is deposited on the surface of the second semiconductor 103 layer. The electrode contact layer 201 is made of a transparent and conductive ITO material. Subsequently, a trench array is etched on the transparent electrode and the second semiconductor 103 layer using micro-nano fabrication techniques. The etching depth is close to the thickness of the second semiconductor 103 layer, and the diameter of the trench is 5 micrometers. By controlling the etching process, the sidewalls of the trenches have a certain tilt angle, approximately 30 degrees. The trenches are periodically arranged on the surfaces of the electrode contact layer 201 and the second semiconductor 103 layer, and the cumulative area of ​​the trenches accounts for 30% of the total area of ​​the second semiconductor 103 layer.

[0101] Subsequently, a medium layer of 302SiO2 with a thickness of 46 nm was deposited inside the pore.

[0102] Based on this, the SiO2 layer covering the transparent electrode in areas other than the hole is removed by mask definition. Then, an Al thin film is deposited in the hole using mask definition, with a surface roughness of approximately 3 nm. After metal deposition, reflective metal fills the hole, resulting in a trapezoidal structure in its cross-section.

[0103] Finally, an electrode contact layer 201, consisting of a first electrode 203-1 and a second electrode 203-2, is deposited on the side of the second semiconductor near its outer surface. A PV protective layer isolates the electrode PAD region from the reflective metal. This ultimately fabricates a typical flip-chip deep ultraviolet LED device.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A deep ultraviolet LED device with wave vector modulation, characterized in that: The device structure sequentially includes a transparent substrate, a first semiconductor layer, a quantum well layer, a second semiconductor layer, an electrode contact layer, and a metal electrode. The metal electrode has a first electrode and a second electrode with opposite electrical polarities, which are respectively connected to the first semiconductor layer and the electrode contact layer. The second semiconductor layer and the electrode contact layer are etched with slots, and the slots are filled with a reflective layer. A dielectric layer is deposited between the reflective layer and the second semiconductor layer and the quantum well layer in the slot portion. A dielectric layer is provided to isolate the first electrode and the second electrode from the penetrating quantum well layer, the second semiconductor layer, and the electrode contact layer. A dielectric layer is provided between the first electrode and the second electrode and the electrode contact layer. The emission wavelength of the deep ultraviolet LED device is no greater than 320nm; The sidewall of the slot makes an angle of 5 to 60 degrees with the normal to the surface of the second semiconductor layer, and the cross-section of the opening structure parallel to the hole axis is trapezoidal. The equivalent optical path length of the thickness of the first dielectric layer is an odd multiple of 1 / 4 wavelength.

2. The deep ultraviolet LED device with wave vector modulation according to claim 1, characterized in that: The diameter of the slot is 0.2 to 10.0 micrometers, and the cumulative area of ​​the slot in the cross-sectional opening area perpendicular to the hole axis accounts for 1% to 90% of the area of ​​the second semiconductor layer. The slots are arranged in a periodic uniform array or randomly distributed.

3. The deep ultraviolet LED device with wave vector modulation according to claim 1, characterized in that: The reflective layer extends between the electrode contact layer and the dielectric layer.

4. A deep ultraviolet LED device with wave vector modulation according to claim 1, characterized in that: The reflective layer is composed of one or more of Al, Rh, Pt, or Ni.

5. A deep ultraviolet LED device with wave vector modulation according to claim 1, characterized in that: The reflective layer has a flat or uneven interface with the dielectric layer, and the height difference of the unevenness is no greater than 5 nm.

6. A deep ultraviolet LED device with wave vector modulation according to claim 1, characterized in that: The dielectric layer is one of SiO2, MgF2, Na3AlF6, and Al2O3.

7. A method for fabricating a deep ultraviolet LED device with wave vector modulation, characterized in that: Includes the following steps: 1) Select a light-transmitting substrate, which includes a first surface side and a second surface side opposite to each other. A buffer layer, a first semiconductor layer, a quantum well layer, a second semiconductor layer, and a functional layer between each key layer are grown sequentially on the first surface side of the light-transmitting substrate to realize the deep ultraviolet emission function of the LED. 2) Deposit an electrode contact layer on the surface of the second semiconductor layer; 3) Using a mask, an opening area is defined on the surface of the electrode contact layer, and the slot, the first deposited dielectric layer, and the reflective layer are sequentially etched and prepared; 4) Fabricate the first electrode, the second electrode, and other dielectric layers two and three that electrically isolate the electrodes from the surrounding semiconductor / conductor layers, and complete the semiconductor light-emitting sequence unitization to obtain a semiconductor light-emitting device; The emission wavelength of the deep ultraviolet LED device is no greater than 320nm; The sidewall of the slot makes an angle of 5 to 60 degrees with the normal to the surface of the second semiconductor layer, and the cross-section of the opening structure parallel to the hole axis is trapezoidal. The equivalent optical path length of the thickness of the first dielectric layer is an odd multiple of 1 / 4 wavelength.

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