WO2023193257A1 - 发光芯片、发光芯片外延层及其生长方法 - Google Patents

发光芯片、发光芯片外延层及其生长方法 Download PDF

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WO2023193257A1
WO2023193257A1 PCT/CN2022/085910 CN2022085910W WO2023193257A1 WO 2023193257 A1 WO2023193257 A1 WO 2023193257A1 CN 2022085910 W CN2022085910 W CN 2022085910W WO 2023193257 A1 WO2023193257 A1 WO 2023193257A1
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layer
source
growth
period
cycle
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PCT/CN2022/085910
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English (en)
French (fr)
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黄兆斌
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重庆康佳光电技术研究院有限公司
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Priority to PCT/CN2022/085910 priority Critical patent/WO2023193257A1/zh
Publication of WO2023193257A1 publication Critical patent/WO2023193257A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure

Definitions

  • the present invention relates to LED (Light Emitting Diode (light-emitting diode) technical field, particularly relates to a light-emitting chip, a light-emitting chip epitaxial layer and a growth method thereof.
  • LED Light Emitting Diode
  • LEDs are widely used in display, lighting, disinfection and other fields because of their small size, light weight, low power consumption, high luminous efficiency, environmental friendliness, and continuously adjustable luminous wavelength.
  • GaN gallium nitride
  • AlGaN aluminum gallium nitride
  • UV LED chips are widely used in medical disinfection, water purification, etc.
  • the quality of LED chips currently depends largely on the crystal quality of the epitaxial layer, which is of poor quality.
  • the quality of the epitaxial layer is not high due to serious lattice mismatch between layers, which seriously affects the quality of LED chips. Therefore, how to improve the crystal quality of the epitaxial layer is an urgent problem that needs to be solved.
  • the purpose of this application is to provide a light-emitting chip, a light-emitting chip epitaxial layer and a growth method thereof, aiming to solve the problem of poor crystal quality of the epitaxial layer affecting the quality of the LED chip.
  • This application provides an epitaxial layer of a light-emitting chip, including:
  • the N-type current expansion layer and the P-type current expansion layer are located on opposite sides of the quantum well layer; at least one current expansion layer is grown by at least two The doping concentration of each current spreading sub-layer gradually decreases in the direction approaching the quantum well layer.
  • this application also provides a light-emitting chip, which includes:
  • the N electrode is electrically connected to the N-type current expansion layer
  • the P electrode is electrically connected to the P-type current expansion layer.
  • this application also provides a method for growing the epitaxial layer of a light-emitting chip, including growing a quantum well layer and a current expansion layer located on opposite sides of the quantum well layer; the current expansion layer consists of at least two current expansion layers stacked in sequence.
  • the expansion sub-layer consists of the growth current expansion layer including:
  • the basic source and doping source corresponding to the current expansion layer are introduced into the reaction chamber, and each current expansion sub-layer is grown layer by layer.
  • One current expansion sub-layer corresponds to one growth cycle, and in two adjacent growth cycles, it is closer to the quantum well.
  • the growth time of a layer has a smaller doping-to-basic ratio, which is the ratio between the input amount of the doping source and the input amount of the basic source.
  • the current spreading layer is composed of at least two current spreading sub-layers stacked sequentially along the growth direction, and in the direction close to the quantum well layer, each current spreading sub-layer in the current spreading layer
  • the doping concentration of the layer is gradually reduced, which ensures that the current extension layer contacts the low-doped quantum well layer with a low-doped current extension sub-layer, thereby preventing the doping concentration of the current extension layer from being much higher than that of the quantum well layer. impurity concentration, resulting in serious lattice mismatch problems between the current expansion layer and the quantum well layer.
  • the epitaxial layer of the light-emitting chip of the present application improves the efficiency of the light-emitting chip by reducing the lattice mismatch between the current expansion layer and the quantum well layer.
  • the current spreading layer is composed of at least two current spreading sub-layers stacked sequentially along the growth direction, and in the direction close to the quantum well layer, the current spreading sub-layer in the current spreading layer has The doping concentration is gradually reduced, which ensures that the current extension layer contacts the low-doped quantum well layer with a low-doped current extension sub-layer, thus preventing the doping concentration of the current extension layer from being much higher than the doping concentration of the quantum well layer. , resulting in a serious lattice mismatch problem between the current extension layer and the quantum well layer.
  • the epitaxial layer of the light-emitting chip improves the efficiency of the epitaxial layer of the light-emitting chip by reducing the lattice mismatch between the current extension layer and the quantum well layer.
  • the crystal quality of In the layer direction, the doping concentration of each current expansion sub-layer also gradually decreases, which can ensure the crystal quality of the current expansion layer itself, thereby further enhancing the quality of the light-emitting chip.
  • At least two sequentially stacked current expansion sub-layers are grown along the growth direction to form a current expansion layer.
  • One current expansion sub-layer grows for one growth cycle and is closer to the growth time of the quantum well layer.
  • the doping-to-basis ratio corresponding to the growth cycle is smaller, which means that the doping concentration of the current expansion layer closer to the quantum well layer is lower, which can ensure that the current expansion layer in the epitaxial layer of the light-emitting chip is low-doped.
  • the current extension sub-layer is in contact with the low-doped quantum well layer, thereby preventing the doping concentration of the current extension layer from being much higher than the doping concentration of the quantum well layer, resulting in severe lattice mismatch between the current extension layer and the quantum well layer.
  • this application improves the crystal quality of the epitaxial layer of the light-emitting chip by reducing the lattice mismatch between the current extension layer and the quantum well layer; moreover, because in the two adjacent current extension sub-layers in the current extension layer, the total The one closer to the quantum well layer has a lower doping concentration, so in the current expansion layer, in the direction closer to the quantum well layer, the doping concentration of each current expansion sub-layer also gradually decreases, which can ensure The crystal quality of the current expansion layer itself further enhances the quality of the epitaxial layer of the light-emitting chip and improves the quality of the light-emitting chip produced based on the epitaxial layer.
  • Figure 1 is a schematic structural diagram of the epitaxial layer of a light-emitting chip provided in an optional embodiment of the present application;
  • Figure 2 is a schematic structural diagram of a light-emitting chip provided in an optional embodiment of the present application.
  • Figure 3 is a schematic diagram of the access timing of each source in the reaction chamber when growing the current expansion layer provided in another optional embodiment of the present application;
  • Figure 4 is a schematic diagram of another access timing of each source in the reaction chamber when growing the current expansion layer provided in another optional embodiment of the present application;
  • Figure 5 is another schematic diagram of the access timing of each source in the reaction chamber when growing the current expansion layer provided in another optional embodiment of the present application;
  • Figure 6 is a schematic diagram of yet another access timing of each source in the reaction chamber when growing the current expansion layer provided in another optional embodiment of the present application;
  • Figure 7 is a schematic structural diagram of the epitaxial layer of a light-emitting chip provided in another optional embodiment of the present application.
  • Figure 8 is a schematic structural diagram of the N-type current expansion layer in Figure 7;
  • Figure 9 is a schematic structural diagram of the P-type current expansion layer in Figure 7.
  • Figure 10 is a schematic flow chart corresponding to a growth cycle provided in yet another optional embodiment of the present application.
  • Figure 11 is a schematic diagram of the access timing of each source in the reaction chamber when growing the N-type current expansion layer provided in yet another optional embodiment of the present invention.
  • FIG. 12 is a schematic diagram of the input timing of each source in the reaction chamber when growing an N-type current spreading layer in yet another optional embodiment of the present invention.
  • the atomic radius of the doping atoms is smaller than the atoms of the basic atoms in the current expansion layer.
  • the atomic radius of P-type doping atom Mg (magnesium) and N-type doping atom Si (silicon) are smaller than Ga (gallium) atom and Al (aluminum) atom , specifically, the radius of Mg atoms is 0.172 nm, the radius of Si atoms is 0.117 nm, and the radius of Ga atoms and Al atoms are 0.181 nm and 0.182 nm respectively.
  • This embodiment first provides an epitaxial layer of a light-emitting chip. Please refer to a schematic structural diagram of the epitaxial layer 10 of the light-emitting chip shown in Figure 1:
  • the epitaxial layer 10 of the light-emitting chip includes a quantum well layer 12 and two current expansion layers 11 respectively located on both sides of the quantum well layer 12.
  • One of the two current expansion layers is an N-type current expansion layer 11a and the other is a P-type current expansion layer.
  • Layer 11b One of the two current expansion layers is an N-type current expansion layer 11a and the other is a P-type current expansion layer.
  • the light-emitting chip epitaxial layer 10 may also include other layer structures, such as a stress control layer, an electron blocking layer, Buffer layer etc.
  • At least one of the two current spreading layers 11 is composed of at least two current spreading sub-layers 110 .
  • each current expansion sub-layer 110 is stacked sequentially along the growth direction of the light-emitting chip epitaxial layer 10.
  • the light-emitting chip epitaxial layer 10 is an N-type current expansion layer. Starting from one side of the layer 11a, it grows toward the P-type current spreading layer 11b. Therefore, the growth direction is from the N-type current spreading layer 11a to the P-type current spreading layer 11b. In Figure 1, the growth direction is from bottom to top.
  • the doping concentration of each current spreading sub-layer 110 in the current spreading layer 11 gradually decreases in the direction approaching the quantum well layer 12 .
  • the direction close to the quantum well layer 12 is the growth direction, that is, the bottom-up direction. Therefore, in the N-type current spreading layer 11a of FIG. 1 , the doping concentration of each current spreading sub-layer 110 gradually decreases from bottom to top.
  • the direction close to the quantum well layer 12 is the opposite direction to the growth direction, that is, the top-down direction. Therefore, in the P-type current spreading layer 11b in FIG. 1, each The doping concentration of the current spreading sublayer 110 gradually decreases from top to bottom.
  • the current spreading sub-layer 110 relatively close to the quantum well layer 12 has a lower doping concentration than the current spreading sub-layer 110 relatively far away from the quantum well layer 12, so , the current spreading layer 11 can contact the quantum well layer 12 with the current spreading sub-layer 110 having a lower doping concentration.
  • the quantum well layer 12 is unintentionally doped, so the doping concentration of the quantum well layer 12 is basically 0. This can reduce the lattice difference between the current expansion layer 11 and the quantum well layer 12 and reduce the size of the light-emitting chip.
  • the number of dislocations in the epitaxial layer 10 improves the quality of the epitaxial layer 10 of the light-emitting chip and enhances the quality of the light-emitting chip.
  • the thickness of each current expansion sub-layer 110 in the current expansion layer 11 also gradually decreases in the direction approaching the quantum well layer 12. Therefore, in the N-type current expansion layer 11a, The thickness of each current spreading sub-layer 110 gradually decreases from bottom to top, and in the P-type current spreading layer 11b, the thickness of each current spreading sub-layer 110 gradually decreases from top to bottom. It can be understood that in other examples of this embodiment, the thickness of each current spreading sub-layer 110 in the same current spreading layer 11 can also be uniform.
  • the thickness gradient of the current spreading sub-layer 110 exists in both current spreading layers 10 in the epitaxial layer 10 of the light-emitting chip shown in FIG. 1
  • the light-emitting chip Among the two current spreading layers 11 of the epitaxial layer 10 one may include a current spreading sub-layer with a gradient thickness, and the other may include a current spreading sub-layer with a consistent thickness.
  • the doping concentration gradient of the current spreading sub-layer 110 exists in both the N-type current spreading layer 11a and the P-type current spreading layer 11b.
  • one includes a current spreading sub-layer with gradient doping
  • the other includes a current spreading sub-layer with a constant doping concentration or irregular changes in doping concentration.
  • the current spreading layer 11 may include Al x Ga 1-x N, optionally, 0.4 ⁇ x ⁇ 1, for example, the value of 0.9 etc.
  • the AlGaN-based light-emitting chip epitaxial layer 10 can be made into an AlGaN-based ultraviolet light-emitting diode and applied to the field of disinfection.
  • the value of x may be 0.
  • the current spreading layer 11 includes GaN, and the GaN-based light-emitting chip epitaxial layer 10 can be used to produce blue-green LED chips, which are widely used in lighting. , display area.
  • the light-emitting chip 2 includes the light-emitting chip epitaxial layer 10, N electrode 20a and P electrode 20b, wherein the N electrode 20a is electrically connected to the N-type current spreading layer 11a in the epitaxial layer 10 of the light-emitting chip, and the P electrode 20b is electrically connected to the P-type current spreading layer 11b in the epitaxial layer 10 of the light-emitting chip.
  • the structure, light-emitting color, etc. of the light-emitting chip 2 are not specifically limited.
  • it can be a flip-chip structure, a formal structure, or a vertical structure; it can be an ultraviolet light-emitting chip, or it can be a blue light-emitting chip. chip, or it can also be a green light chip.
  • the doping concentration of each current extension sub-layer in the N-type current extension layer gradually decreases along the growth direction, while the doping concentration of each current extension sub-layer in the P-type current extension layer The concentration gradually increases along the growth direction, thereby reducing the lattice difference between the current expansion layer and the quantum well layer while ensuring high doping of the current expansion layer, improving the quality of the epitaxial layer of the light-emitting chip, and enhancing the strength of the light-emitting chip. the quality of.
  • This application provides a method for growing the epitaxial layer of a light-emitting chip:
  • growing the epitaxial layer of a light-emitting chip requires growing a quantum well layer and current spreading layers located on opposite sides of the quantum well layer.
  • the N-type current expansion layer may be grown first, then the quantum well layer may be grown on the N-type current expansion layer, and then the P-type current expansion layer may be grown on the quantum well layer.
  • the epitaxial layer of the light-emitting chip can be grown using MOCVD (Metal-organic Chemical Vapor Deposition (metal organic compound chemical vapor deposition) process or MOMBE (Metal Organic Molecular-Beam Epitaxy) process (also known as chemical beam epitaxy CEB), in some examples when growing the epitaxial layer of the light-emitting chip, the reaction chamber can be passed Input MO (high-purity metal organic compound) source for epitaxial growth. For example, when growing a current extension layer, a basic source and a doping source need to be introduced into the reaction chamber.
  • MOCVD Metal-organic Chemical Vapor Deposition (metal organic compound chemical vapor deposition) process
  • MOMBE Metal Organic Molecular-Beam Epitaxy
  • CEB chemical beam epitaxy
  • the basic source is used to form the basic crystal layer of the epitaxial layer of the light-emitting chip, while the doping source is used to dope the basic crystal layer. Miscellaneous, if the epitaxial layer of the light-emitting chip is based on AlGaN, the basic source is used to form AlGaN; if the epitaxial layer of the light-emitting chip is based on GaN, the basic source is used to form GaN.
  • the basic source usually includes a metal source and a nitrogen source.
  • the metal source needs to provide Al atoms and Ga atoms; if the epitaxial layer of the light-emitting chip is based on GaN, the metal source only needs to provide Ga atoms. If the epitaxial layer of the light-emitting chip is AlN-based, the metal source may only include an aluminum source that provides Al atoms. In some examples of this embodiment, the aluminum source may include, but is not limited to, TMAl (trimethylaluminum).
  • the gallium source includes, but is not limited to, at least one of TMGa (trimethylgallium) and TEGa (triethylgallium). For example, in some examples of this embodiment, TMGa or TEGa can be used as the gallium source, and in other examples of this embodiment, both TMGa and TEGa can be used as the gallium source.
  • a common nitrogen source may be NH 3 (ammonia), but those skilled in the art can understand that NH 3 is not the only nitrogen source.
  • the material of the doping source is related to the doping type of the current expansion layer: if it is an N-type current expansion layer, the doping source includes but is not limited to any one of silicon source, boron source and germanium source.
  • the doping source of the N-type current spreading layer is a silicon source, such as SiH 4 (monosilane) or Si 2 H 6 (disilane). In some examples of this embodiment, SiH 4 and Si 2 H 6 can also be used as silicon sources at the same time.
  • the doping source includes but is not limited to at least one of a magnesium source and a zinc source.
  • the doping source of the P-type current spreading layer is a magnesium source, such as Cp 2 Mg (magnesium cyclocene).
  • the current expansion layer includes at least two current expansion sub-layers stacked sequentially along the growth direction. Therefore, when growing the current expansion layer, it is necessary to grow each current expansion sub-layer layer by layer along the growth direction.
  • the growth time of the current spreading sublayer corresponds to one growth cycle.
  • the doping-basic ratio corresponding to each growth period gradually decreases as the growth time moves back, where the doping-basic ratio refers to the doping source pass Therefore, along the growth direction, the doping concentration in each current expansion sub-layer in the N-type current expansion layer gradually decreases. If the P-type current expansion layer is grown, as the growth time moves back, the doping-to-base ratio corresponding to each growth period gradually increases.
  • the current expansion sub-layers in the P-type current expansion layer The doping concentration gradually increases. In other words, in the direction approaching the quantum well layer, the doping concentration of each current extension sub-layer in the current extension layer (whether it is an N-type current extension layer or a P-type current extension layer) gradually decreases.
  • the one closer to the growth time of the quantum well layer has a smaller ratio of the doping source and the basic source introduced into the reaction chamber.
  • the same content of the basic source can be introduced into the reaction chamber during the two growth periods. In this case, it is achieved by controlling the input concentration c and/or the input flow rate f of the doping source during the two growth cycles.
  • the flow rate of the doping source in T1 is The inlet concentration c1 and the inlet flow rate f2 are respectively smaller than the inlet concentration c2 and the inlet flow rate f2 in T2.
  • the input concentration and input flow rate of the basic source in each growth cycle are the same.
  • the doping The input concentration c of the source in each growth cycle gradually decreases, and the input flow rate f also gradually decreases;
  • the input concentration c of the doping source in each growth cycle Gradually increasing, the incoming flow rate f also gradually increases, so that along the growth direction, the doping concentration corresponding to each current expansion sub-layer in the N-type current expansion layer gradually decreases, while each current in the P-type current expansion layer The effect of gradually increasing the doping concentration corresponding to the expansion sublayer.
  • the doping concentration of the quantum well layer in the epitaxial layer of the light-emitting chip is not high, when growing the N-type current expansion layer, the growth concentration of each current expansion sub-layer is gradually reduced. This can not only ensure that the N-type current expansion layer
  • the crystal quality itself can also reduce the lattice difference between the N-type current expansion layer and the quantum well layer, avoid large lattice mismatch between the N-type current expansion layer and the quantum well layer, reduce dislocations, and improve the epitaxy of light-emitting chips. The crystal quality of the layer.
  • gradually increasing the doping concentration of each current extension sub-layer in the P-type current extension layer is also to achieve high doping of the P-type current extension layer while reducing the lattice between the P-type current extension layer and the quantum well layer. Mismatch, enhancing the crystal quality of the epitaxial layer of the light-emitting chip.
  • the ratio of the doping source and the basic source introduced into the reaction chamber at any time during the same growth cycle is the same, and this doping method belongs to "uniform doping". In some examples, there are at least two moments in the same growth cycle where the ratio of the doping source and the basic source introduced into the reaction chamber is different. Compared with the uniform doping method, the latter doping method belongs to "non-uniform doping". ".
  • a growth cycle includes at least two cycle periods, and the cycle cycle includes at least a first period t1 and a second period t2 located after the first period t1.
  • a nitrogen source, a metal source, and a doping source can be introduced into the reaction chamber during the first period t1, where the metal source, the doping source In the first period t1, the input amounts are k1 and k2 respectively; in the second period t2, the nitrogen source, metal source, and doping source are introduced into the reaction chamber, and the metal source and doping source are supplied in the second period t2.
  • the input amounts are k3 and k4 respectively.
  • the metal source introduced into the reaction chamber in the first period t1 is more than the metal source introduced in the second period t2.
  • the input amount of the metal source is much more than the input amount of the metal source in the second period t2
  • the input amount of the doping source in the second period t2 is much more than the input amount of the doping source in the first period t1.
  • the values of k1, k2, k3 and k4 are not 0, where the rising edge means the starting point of a period, and the falling edge corresponds to the end point of the period.
  • the cycle period consists of the first period t1 and the second period t2, so the first The period t1 is immediately adjacent to the second period t2, and the end point of the first period t1 is also the starting point of the second period t2.
  • the nitrogen source is always open during the cycle.
  • the reaction chamber is under an ammonia atmosphere throughout the cycle.
  • At least one of k2 and k3 takes a value of 0.
  • a metal source and a metal source are introduced into the reaction chamber during the first period t1. Nitrogen source, but the doping source will not be introduced; and during the second period t2, the doping source and nitrogen source will be introduced into the reaction chamber, but the metal source will not be introduced. Therefore, in the scheme corresponding to Figure 4 , the values of k2 and k3 are both 0. In this scheme, the metal source and the doping source are introduced alternately. When the doping source is introduced, the metal source is not introduced at the same time. Therefore, when the doping source is first introduced, it can be formed in the base source.
  • a thin impurity film is formed on the surface of the basic crystal layer, and the impurity film is used to form a diffusion channel for lateral transfer of atoms, so that the basic source atoms have a greater diffusion length on the surface, which enhances the two-dimensional layered growth characteristics in the current expansion layer. Reduced lattice mismatch.
  • the enhancement of the two-dimensional layered growth characteristics means an acceleration of the lateral growth speed and an increase in the ratio of the lateral growth speed to the longitudinal growth speed, which can make the edge dislocation more easily slip along the slip surface, thereby causing Bending or even annihilation, thereby reducing edge dislocation density and improving crystal quality.
  • the alternating introduction of the basic source and the doping source ensures that the atoms of the doping source have enough time to adsorb on the surface of the grown basic crystal layer, diffuse into the basic crystal layer, and finally be evenly distributed in the basic crystal layer Within, it also increases the desorption probability of atoms, enhances the quality of the epitaxial layer of the light-emitting chip, and improves the quality of the light-emitting chip.
  • the duration of the first period t1 is longer than the duration of the second period t2.
  • the duration of the first period t1 can range from 0 to 30 seconds.
  • the duration of the first period t1 ranges from 1 to 28s, such as 25s, 20s, 18s or 15s, etc.
  • the duration of the second period t2 ranges from 0 to 20s, such as the duration of the second period t2 in some examples.
  • the value is 1 ⁇ 18s, for example, the second period t2 is 17s, 15s, 10s, 5s or 3s, etc.
  • the cycle period may also include a third period t3.
  • the third period t3 is located after the second period t2. During the third period t3, no one is allowed to enter the reaction chamber.
  • the metal source does not introduce the doping source into the reaction chamber, which can leave sufficient expansion time for the doping source atoms in the impurity film, thereby ensuring that the impurity film can evenly penetrate and disperse into the basic crystal layer in the form of atoms, achieving Doping of the base crystal layer.
  • the nitrogen source will continue to be introduced into the reaction chamber during the third period t3, but in other examples, the introduction of the nitrogen source into the reaction chamber will also be stopped during the third period t3. In the latter scheme, During a cycle, the nitrogen source is introduced into the reaction chamber in a pulse manner.
  • the cycle period in addition to the first period t1 and the second period t2, the cycle period also includes a fourth period t4 between the first period t1 and the second period t2. Please refer to FIG. 6 shown.
  • neither the metal source nor the doping source is introduced into the reaction chamber during the fourth period t4.
  • the fourth period t4 may allow the metal source and the doping source to be turned on at the same time.
  • the parameters of the cycle included in each growth cycle are the same.
  • the same parameters of the cycle mean that the total duration of the cycle is the same and the time period distribution within the cycle is also the same. If two cycles
  • the same period distribution means that the periods contained in the two cycles are the same, the order of periods in the cycle is the same, and the duration of each period is also the same.
  • the cycle period in the growth period T1 corresponding to a current extension sub-layer a of the current extension layer, the cycle period consists of a first period t1 and a second period t2, where the duration of the first period t1 is 18 s, and the duration of the second period t2 is 18 seconds.
  • the cycle period included in the growth period T2 corresponding to the other current extension sub-layer b in the current extension layer is also composed of a first period t1 with a duration of 18s and a second period t2 with a duration of 12s.
  • the cycle number r of the cycle included in one of the two adjacent growth cycles that is closer to the growth time of the quantum well layer smaller.
  • the growth period T1 corresponds to the current expansion sublayer a1 in the N-type current expansion layer
  • the growth period T2 corresponds to the current expansion sublayer a2 in the N-type current expansion layer
  • the current expansion sublayer a1 is larger than the current expansion sublayer a2 Closer to the quantum well layer, therefore, T1 corresponding to the current expansion sublayer a1 is closer to the growth time of the quantum well layer than T2 corresponding to the current expansion sublayer a2. Therefore, the number of cycles r1 contained in T1 is larger than that in T2 The number of cycles included in the cycle r2 is smaller.
  • the thickness of different current expansion sub-layers grown in a single cycle is not very different, but because the thickness of the growth cycle close to the growth time of the quantum well layer It contains fewer cycles, so the thickness of the current extension sub-layer close to the quantum well layer is thinner.
  • the current extension sub-layer a1 is thinner than the current extension sub-layer a2.
  • the parameters of the cycle included in different growth cycles are different.
  • the cycles R1 and R2 belong to the growth cycles T1 and T2 respectively, and the total duration of the two cycles R1 and R2 is different.
  • the distribution of periods within the cycle is the same.
  • the total duration of R2 is smaller than the total duration of R1.
  • the growth thickness of one cycle in T1 is greater than the growth thickness of one cycle in T2. Therefore, even if different growth cycles T1 and T2 contain the same cycle number r, the current expansion sublayer corresponding to T1 The thickness of is also greater than the thickness of the current expansion sublayer corresponding to T2.
  • the environmental parameters in the reaction chamber can be the same at different times when the current expansion layer is grown. This requires that the environmental parameters in the reaction chamber in different growth cycles are the same.
  • the environment in the reaction chamber in the same growth cycle and different cycle periods must be the same.
  • the parameters are the same, and the environmental parameters of the reaction chamber in different time periods within the same cycle are also the same.
  • Environmental parameters may include temperature and pressure, so in these examples the reaction chamber may always be maintained at the same temperature and pressure conditions when growing different current spreading sub-layers of a current spreading layer.
  • the pressure in the reaction chamber can be maintained between 50 and 250 Torr. In other examples, the pressure in the reaction chamber can be maintained between 200 and 250 Torr.
  • the pressure can be maintained between 140 and 155 Torr. In addition, the pressure can also be between 80 ⁇ 140Torr, or between 155 ⁇ 200Torr, which will not be enumerated here.
  • the temperature in the reaction chamber can be maintained between 850 and 1300°C. For example, in an example of this embodiment, the reaction temperature can be maintained at 900 ⁇ 1250°C.
  • the reaction temperature in the reaction chamber can be maintained between 750 and 1150°C. For example, in an example of this embodiment, the reaction temperature can be maintained at 800 ⁇ 1100°C.
  • the environmental parameters of the reaction chamber are different at at least two moments during the growth of the current expansion layer.
  • the environmental parameters of the reaction chamber in different growth cycles are not exactly the same.
  • the temperature or pressure may be different. , or both temperature and pressure are different. Therefore, in these examples, the environmental parameters in the reaction chamber can be controlled step by step in different growth cycles, so that different current spreading sub-layers grow in different environments. It can be understood that in some examples of this embodiment, there may also be situations where the environmental parameters of the reaction chamber corresponding to different cycles in the same growth cycle are different, or the environmental parameters of the reaction chamber corresponding to different periods in the same cycle are different. Condition.
  • This embodiment first provides a light-emitting chip epitaxial layer.
  • a light-emitting chip epitaxial layer 70 includes a substrate 71 and a stress control layer 72 from bottom to top. , N-type current spreading layer 73, preparation layer 74, quantum well layer 75, electron blocking layer 76, P-type current spreading layer 77, P-type ohmic contact layer 78.
  • the substrate 71 When growing the optical chip epitaxial layer 70, other layer structures are epitaxially grown layer by layer from the upper surface of the substrate 71 upward: the substrate 71 is placed in the reaction chamber, the substrate 71 is cleaned and preheated, and then grown on its surface.
  • the stress control layer 72 is formed, and each N-type current expansion sub-layer of the N-type current expansion layer 73 is grown layer by layer on the stress control layer 72 to form the N-type current expansion layer 73 .
  • a preparation layer 74 is grown on the N-type current spreading layer 73 , and a quantum well layer 75 is grown on the preparation layer 74 .
  • the electron blocking layer 76 can be grown on its upper surface, and then each P-type current expansion sub-layer is grown layer by layer on the electron blocking layer 76 to form the P-type current expansion layer 77, and then the P-type current expansion layer 77 is formed.
  • a P-type ohmic contact layer 78 is grown on the extension layer 77 .
  • the N-type current spreading layer 73 includes a first sub-layer 731, a second sub-layer 732... an i-th sub-layer 73i... an n-th sub-layer 73n from bottom to top.
  • the P-type current spreading layer 77 includes a first sub-layer 771, a second sub-layer 772...j-th sub-layer 77j...m-th sub-layer 77m in order from bottom to top.
  • the nitrogen source and the metal source are introduced into the reaction chamber without the doping source, so that the nitrogen source and the metal source can be used to form a basic crystal layer.
  • the light-emitting chip epitaxial layer 70 is an AlGaN-based epitaxial layer, so the basic crystal layer is the AlGaN crystal layer.
  • NH 3 is used as the nitrogen source.
  • the metal source includes a gallium source and an aluminum source.
  • TMAl is used as the aluminum source, and TMGa (trimethylgallium) and TEGa (triethylgallium) are used. At least one serves as a gallium source.
  • the input concentration and input flow rate of the basic source remain unchanged in each growth cycle, that is, in each growth cycle, the input concentration and input flow rate are the same. Introduce the nitrogen source, and when it is necessary to introduce the metal source into the reaction chamber, do it according to the same inlet concentration and inlet flow rate.
  • the nitrogen source and the doping source are introduced into the reaction chamber, and the metal source is stopped.
  • the doping source can be used to form a thin impurity film on the basic crystal layer, and the impurity film is
  • the doping atoms will diffuse horizontally and vertically in the subsequent time, and evenly penetrate into the basic crystal layer to achieve doping of the basic crystal layer.
  • the impurity film can serve as a diffusion channel for atoms, increase the expansion length of atoms, enhance the two-dimensional layered growth characteristics in the current expansion layer, and reduce the lattice mismatch.
  • the two-dimensional layered growth characteristics are obvious, which means that the ratio of the lateral growth rate and the longitudinal growth rate deserves to be improved.
  • This can make the edge dislocations in the epitaxial crystal more easily slip along the slip plane, causing bending or even annihilation, and then Reduce edge dislocation density and significantly improve crystal quality.
  • the metal source is not introduced at the same time when the doping source is introduced during the second period t2, this can give the doping atoms more time to diffuse, thereby increasing the desorption probability of the atoms and further improving the epitaxial layer 70 of the light-emitting chip. quality.
  • the doping source corresponding to the N-type current spreading layer 73 is a Si source
  • the doping source corresponding to the P-type current spreading layer 77 is an Mg source.
  • SiH 4 can be selected as the N-type doped Si source
  • Cp 2 Mg can be used as the P-type doped Mg source.
  • the doping concentration of each current extension sub-layer in a current extension layer changes gradually, for the N-type current extension layer 73, the doping concentration of each current extension sub-layer it contains along the growth direction The doping concentration gradually decreases.
  • the doping concentration of each current spreading sub-layer contained therein gradually increases along the growth direction.
  • the flow rate f of the doping source into the reaction chamber in different growth cycles is different from the concentration c: when growing the N-type current expansion layer, as the growth time goes by, In each growth cycle, the input concentration c of the doping source gradually decreases, and the input flow rate f also gradually decreases.
  • the input concentration c of the doping source in each growth cycle gradually increases, and the input flow rate f also gradually increases.
  • the input flow rate f of the doping source in each growth cycle can be kept unchanged, and its input concentration c can be gradually changed; in other examples, the doping source can be kept constant
  • the input concentration c of the source remains unchanged in each growth cycle, but its input flow rate f gradually changes.
  • the input concentration c and the input flow rate f of the doping source can even change in opposite trends, for example, the i-th N-type current expansion in the N-type current expansion layer grown in the i-th growth cycle When the sub-layer is formed, relative to the i-1th growth cycle, the incoming flow rate f of the doping source can be reduced and the incoming concentration c of the doping source can be increased.
  • the doping concentration of needs to be less than the doping concentration of the i-1th N-type current expansion sublayer, so the decrease in flow rate f of the doping source in the i-th growth cycle will be greater than that of the doping source in the i-th growth cycle.
  • the doping concentration is uniform everywhere in the same current spreading sub-layer. Therefore, in several cycles included in a growth cycle, the concentration c of the doping source introduced into the reaction chamber is consistent, and the flow rate is f is also consistent.
  • the cycle period consists of a first period t1, a second period t2, and a third period t3, and the above three periods are arranged in sequence.
  • the third period neither the metal source nor the doping source is introduced into the reaction chamber. This period is left for the dopant atoms in the impurity film to diffuse.
  • the duration of the first period t1 is longer than the duration of the second period t2.
  • the duration of the first period t1 can range from 0 to 30 seconds, while the duration of the second period t2 is The value range is between 0 ⁇ 20s.
  • t1 is 28s and t2 is 18s.
  • the duration of the third period t3 is also shorter than the duration of the first period t1; in some examples, the duration of the third period t3 is equal to the duration of the second period t2, and in some examples, the duration of the third period t3 is shorter than the duration of the first period t1.
  • the duration of the second period t2 can also be made longer than the second period t2, or even the third period t3 can be made longer than the second period t2.
  • the duration of a period t1. the longer the third period t3 is, the more time is available for the diffusion of doped atoms, but at the same time, the growth efficiency of the epitaxial layer 70 of the light-emitting chip is also lower. Therefore, in this embodiment, the length of the third period t3 is set. When doing so, it is necessary to comprehensively consider the growth efficiency of the epitaxial layer of the light-emitting chip and the crystal quality of the epitaxial layer of the light-emitting chip.
  • the cycle period in addition to the first period t1, the second period t2, and the third period t3, the cycle period also includes a fourth period t4.
  • the fourth period t4 is located between the first period t1 and the second period t3. Between t2, in the fourth period t4, the metal source and the doping source can be simultaneously connected. Since the input amount of the metal source in the first period t1 before the fourth period t4 is high, and the input amount of the metal source in the second period t2 after the fourth period t4 is 0, it is before the fourth period t4 In the first period t1 of , the input amount of the doping source is 0, and in the second period t2 after the fourth period t4, the input amount of the doping source is higher.
  • the fourth period t4 can As a transition period during which the input amount of the metal source and the input amount of the doping source gradually changes, during this period, the input flow rate and the input concentration of the metal source gradually decrease, while the input flow rate and input concentration of the doping source gradually increase. .
  • S1008 Determine whether the cumulative number of completed cycles in the current growth cycle reaches the preset number.
  • the "preset number" corresponding to a growth cycle is actually the number of cycles that need to be included in the growth cycle.
  • the size of the preset number is related to the thickness of the current expansion sublayer grown in the growth cycle.
  • the parameters of the cycles included in different growth cycles are the same. In other words, even if the two cycles belong to two growth cycles respectively, the total duration of the two cycles and the distribution of time periods within the cycles are the same. .
  • N-type current expansion layer As the growth time moves back, the number of cycles r included in each growth cycle gradually decreases; when growing a P-type current expansion layer, as the growth time moves back, each growth period The number r of cycles included in the cycle gradually increases.
  • the input flow rate of the doping source is f x6 and the input concentration is c x6
  • the cumulative number of completed cycles in the current growth cycle is 5, which is not less than 6. Therefore, it is necessary to continue to pass in doping according to the flow rate f x6 and the concentration c x6
  • the source undergoes a cycle of growth.
  • the first 1 to 4 cycles correspond to the formation process of the first sub-layer in the N-type current expansion layer 73
  • the 5th to 7th cycles correspond to the formation process of the first sub-layer in the N-type current expansion layer 73.
  • the first cycle period corresponds to the formation process of the second sub-layer in the N-type current expansion layer 73
  • the 8th to 9th cycle periods correspond to the formation process of the third sub-layer in the N-type current expansion layer 73... and so on.
  • the pulse heights corresponding to the doping source are consistent in the first 1 to 2 cycles
  • the pulse heights are consistent in the 3 to 5 cycles
  • the pulse heights are consistent in the 6 to 9 cycles.
  • the doping source input amounts corresponding to the first 1 to 2 cycles are consistent
  • the doping source input amounts corresponding to the 3 to 5 cycles are consistent
  • the doping source input amounts corresponding to the 6 to 9 cycles are consistent.
  • the input amounts are consistent. Therefore, the first 1 ⁇ 2 cycles correspond to the formation process of the first sub-layer in the P-type current expansion layer 77, and the 3 ⁇ 5 cycles correspond to the second sub-layer in the P-type current expansion layer 77.
  • the formation process, the 6th to 9th cycles correspond to the formation process of the third sub-layer in the P-type current expansion layer 77... and so on.
  • the temperature in the reaction chamber is between 880 and 1200°C.
  • the temperature in the reaction chamber is between 810 and 1000°C. between.
  • the pressure in the reaction chamber is between 55 and 240 Torr.
  • the temperature and pressure of the reaction chamber can also be regulated in stages according to the different growth cycles, or according to the different cycle periods in the growth cycle, or according to the different periods within the cycle cycle. .
  • the doping concentration of each current extension sub-layer in the current extension layer of the epitaxial layer of the light-emitting chip gradually decreases along the direction close to the quantum well layer, which can reduce the lattice gap between the current extension layer and the quantum well layer. Differences, reducing lattice mismatch and improving epitaxial crystal quality.
  • the doping source is turned on, the metal source is not turned on, and AlGaN stops growing.
  • the doping source can form a thin impurity film on AlGaN, which helps to form a diffusion channel for lateral transfer of atoms, making Ga or
  • the surface active cover of Al has a larger diffusion length on the surface, causing the lateral growth rate of the epitaxial crystal to be greater than the longitudinal growth rate.
  • the edge dislocations can more easily slide along the slip surface, causing bending or even annihilation, and then pass through Reducing edge dislocation density improves crystal quality.
  • a third period is also set, thereby reserving sufficient migration and diffusion time for the dopant atoms in the impurity film, and further Improved the quality of the epitaxial layer of the light-emitting chip.

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Abstract

本申请涉及一种发光芯片、发光芯片外延层及其生长方法，发光芯片外延层中，包括：量子阱层、N型电流扩展层与P型电流扩展层两个电流扩展层，N型电流扩展层与P型电流扩展层分别位于量子阱层相对的两侧；至少一个电流扩展层由至少两个沿着生长方向依次层叠的电流扩展子层构成，且各电流扩展子层的掺杂浓度在沿着靠近量子阱层的方向上逐渐减小。

Description

发光芯片、发光芯片外延层及其生长方法 技术领域
本发明涉及LED（Light Emitting Diode，发光二极管）技术领域，尤其涉及一种发光芯片、发光芯片外延层及其生长方法。
 背景技术
LED因为具有体积小、重量轻、功耗低、发光效率高、环境友好、发光波长连续可调等优点而广泛应用于显示、照明、消毒等领域，例如，GaN（氮化镓）基LED芯片在显示领域应用广泛，而AlGaN（铝镓氮）基紫外LED芯片则在医疗消毒、净水等方面有着普遍地应用。
不过目前LED芯片的品质很大程度上取决于外延层的晶体质量，质量较差，而外延层因为层与层之间晶格失配严重而质量不高，这严重影响了LED芯片的品质，因此，如何提升外延层的晶体质量是目前亟待解决的问题。
 技术问题
鉴于上述相关技术的不足，本申请的目的在于提供一种发光芯片、发光芯片外延层及其生长方法，旨在解决外延层晶体质量差，影响LED芯片品质的问题。
 技术解决方案
本申请提供一种发光芯片外延层，包括：
量子阱层；
N型电流扩展层与P型电流扩展层两个电流扩展层，N型电流扩展层与P型电流扩展层分别位于量子阱层相对的两侧； 至少一个电流扩展层由至少两个沿着生长方向依次层叠的电流扩展子层构成，且各电流扩展子层的掺杂浓度在沿着靠近量子阱层的方向上逐渐减小。
基于同样的发明构思，本申请还提供一种发光芯片，发光芯片包括：
N电极；
P电极；以及
上述发光芯片外延层；
其中，N电极与N型电流扩展层电连接，P电极与P型电流扩展层电连接。
基于同样的发明构思，本申请还提供一种发光芯片外延层的生长方法，包括生长量子阱层及位于量子阱层相对的两侧的电流扩展层；电流扩展层由依次层叠的至少两个电流扩展子层构成，生长电流扩展层包括：
向反应室内通入与电流扩展层对应的基础源与掺杂源，逐层生长各电流扩展子层，一个电流扩展子层对一个生长周期，且相邻两个生长周期中，更接近量子阱层的生长时间的一个的掺杂-基础比例更小，掺杂-基础比例为掺杂源的通入量与基础源的通入量间的比值。
 
 有益效果
上述发光芯片外延层中，因为电流扩展层中由至少两个沿着生长方向依次层叠的电流扩展子层构成，并且，在沿着靠近量子阱层的方向上，电流扩展层中各电流扩展子层的掺杂浓度逐渐降低，这样可以保证电流扩展层以低掺杂的电流扩展子层与低掺杂的量子阱层接触，从而避免电流扩展层的掺杂浓度远高于量子阱层的掺杂浓度，从而导致电流扩展层与量子阱层出现严重的晶格失配问题，本申请的发光芯片外延层通过减小电流扩展层与量子阱层之间的晶格失配，提升了发光芯片外延层的晶体质量；而且，因为电流扩展层内相邻两个电流扩展子层中，总是更靠近量子阱层的一个的掺杂浓度更低，所以在电流扩展层内，在沿着靠近量子阱层的方向上，各电流扩展子层的掺杂浓度也是逐渐降低的，这可以保证电流扩展层本身的晶体质量，进而进一步增强发光芯片外延层的品质，提升基于该外延层生产的发光芯片的质量。
上述发光芯片中，因为电流扩展层中由至少两个沿着生长方向依次层叠的电流扩展子层构成，并且，在沿着靠近量子阱层的方向上，电流扩展层中各电流扩展子层的掺杂浓度逐渐降低，这样可以保证电流扩展层以低掺杂的电流扩展子层与低掺杂的量子阱层接触，从而避免电流扩展层的掺杂浓度远高于量子阱层的掺杂浓度，从而导致电流扩展层与量子阱层出现严重的晶格失配问题，本申请中发光芯片外延层通过减小电流扩展层与量子阱层之间的晶格失配，提升了发光芯片外延层的晶体质量；而且，因为电流扩展层内相邻两个电流扩展子层中，总是更靠近量子阱层的一个的掺杂浓度更低，所以在电流扩展层内，在沿着靠近量子阱层的方向上，各电流扩展子层的掺杂浓度也是逐渐降低的，这可以保证电流扩展层本身的晶体质量，进而进一步增强发光芯片的品质。
上述发光芯片外延层的生长方法中，会沿生长方向生长至少两个依次层叠的电流扩展子层从而构成电流扩展层，一个电流扩展子层生长一个生长周期，并且更靠近量子阱层生长时间的生长周期所对应的掺杂-基础比例更小，这就意味着更靠近量子阱层的电流扩展层的掺杂浓度更低，这样可以保证发光芯片外延层中的电流扩展层以低掺杂的电流扩展子层与低掺杂的量子阱层接触，从而避免电流扩展层的掺杂浓度远高于量子阱层的掺杂浓度，从而导致电流扩展层与量子阱层出现严重的晶格失配问题，本申请通过减小电流扩展层与量子阱层之间的晶格失配，提升了发光芯片外延层的晶体质量；而且，因为电流扩展层内相邻两个电流扩展子层中，总是更靠近量子阱层的一个的掺杂浓度更低，所以在电流扩展层内，在沿着靠近量子阱层的方向上，各电流扩展子层的掺杂浓度也是逐渐降低的，这可以保证电流扩展层本身的晶体质量，进而进一步增强发光芯片外延层的品质，提升基于该外延层生产的发光芯片的质量。
 附图说明
图1为本申请一可选实施例中提供的发光芯片外延层的一种结构示意图；
图2为本申请一可选实施例中提供的发光芯片的一种结构示意图；
图3为本申请另一可选实施例中提供的生长电流扩展层时反应室中各源的一种通入时序示意图；
图4为本申请另一可选实施例中提供的生长电流扩展层时反应室中各源的另一种通入时序示意图；
图5为本申请另一可选实施例中提供的生长电流扩展层时反应室中各源的又一种通入时序示意图；
图6为本申请另一可选实施例中提供的生长电流扩展层时反应室中各源的再一种通入时序示意图；
图7为本申请另一可选实施例中提供的发光芯片外延层的一种结构示意图；
图8为图7中N型电流扩展层的一种结构示意图；
图9为图7中P型电流扩展层的一种结构示意图；
图10为本申请再一可选实施例中提供的一个生长周期对应的流程示意图；
图11为本发明又一可选实施例中提供的生长N型电流扩展层时反应室中各源的通入时序示意图；
图12为本发明又一可选实施例中提供的生长N型电流扩展层时反应室中各源的通入时序示意图。
附图标记说明：
10-发光芯片外延层；11-电流扩展层；11a-N型电流扩展层；11b-P型电流扩展层；12-量子阱层；110-电流扩展子层；2-发光芯片；20a-N电极；20b-P电极；70-发光芯片外延层；71-衬底；72-应力控制层；73-N型电流扩展层；731- N型电流扩展层的第1子层；732- N型电流扩展层的第2子层；73i- N型电流扩展层的第i子层；73n- N型电流扩展层的第n子层；74-准备层；75-量子阱层；76-电子阻挡层；77-P型电流扩展层；771- P型电流扩展层的第1子层；772- P型电流扩展层的第2子层；77j- P型电流扩展层的第j子层；77m- P型电流扩展层的第m子层；78-P型欧姆接触层。
 本发明的实施方式
为了便于理解本申请，下面将参照相关附图对本申请进行更全面的描述。附图中给出了本申请的较佳实施方式。但是，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施方式。相反地，提供这些实施方式的目的是使对本申请的公开内容理解的更加透彻全面。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施方式的目的，不是旨在于限制本申请。
在生长N型电流扩展层、P型电流扩展层时，需要掺入对应类型的杂质实现N型掺杂与P型掺杂，不过通常掺杂原子的原子半径小于电流扩展层中基础原子的原子半径，例如在GaN材质或AlGaN材质的电流扩展层中，P型掺杂原子Mg（镁）以及N型掺杂原子Si（硅）的原子半径均小于Ga（镓）原子与Al（铝）原子，具体地，Mg原子半径为0.172 nm，Si原子半径为0.117 nm，而Ga原子、Al原子半径分别为0.181 nm、0.182 nm，所以，当掺杂原子掺杂到电流扩展层中代替基础原子时，必然会改变电流扩展层的晶格常数，使得掺杂GaN（或掺杂AlGaN）与非掺杂掺杂GaN（或非掺杂AlGaN）因晶格失配而产生位错，进而导致发光芯片外延层的晶体质量变差。
基于此，本申请希望提供一种能够解决上述技术问题的方案，其详细内容将在后续实施例中得以阐述。
本申请一可选实施例：
本实施例首先提供一种发光芯片外延层，请参见图1示出的该发光芯片外延层10的一种结构示意图：
发光芯片外延层10包括量子阱层12以及分别位于量子阱层12两侧的两个电流扩展层11，这两个电流扩展层中一个为N型电流扩展层11a，另一个为P型电流扩展层11b。应当明白的是，在发光芯片外延层10中，除了N型电流扩展层11a、量子阱层12以及P型电流扩展层11b外，还可以包括其他层结构，例如应力控制层、电子阻挡层、缓冲层等。
在本实施例中，两个电流扩展层11中的至少一个由至少两个电流扩展子层110构成。在一个电流扩展层11中，各电流扩展子层110沿着发光芯片外延层10的生长方向依次层叠，例如，请继续参见图1，通常情况下，发光芯片外延层10是自N型电流扩展层11a一侧起，向着P型电流扩展层11b生长，所以，生长方向就是从N型电流扩展层11a指向P型电流扩展层11b，在图1中生长方向为自下而上。
本实施例中，在沿着靠近量子阱层12的方向上，电流扩展层11中各电流扩展子层110的掺杂浓度逐渐减小。毫无疑义的是，对于N型电流扩展层11a而言，沿着靠近量子阱层12的方向就是生长方向，即自下而上的方向，所以，在图1的N型电流扩展层11a中，各电流扩展子层110的掺杂浓度自下而上逐渐降低。对于P型电流扩展层11b而言，沿着靠近量子阱层12的方向是与生长方向相反的方向，即自上而下的方向，所以，在图1的P型电流扩展层11b中，各电流扩展子层110的掺杂浓度自上而下逐渐降低。不管在N型电流扩展层11a还是P型电流扩展层11b中，相对靠近量子阱层12的电流扩展子层110比相对远离量子阱层12的电流扩展子层110的掺杂浓度更低，所以，电流扩展层11得以以掺杂浓度较低的电流扩展子层110与量子阱层12接触。而通常情况下量子阱层12是非故意掺杂的，所以量子阱层12的掺杂浓度基本为0，这样可以降低电流扩展层11与量子阱层12之间的晶格差异，减小发光芯片外延层10中的位错数量，提升发光芯片外延层10的品质，增强发光芯片的质量。
在本实施例的一些示例中，在沿着靠近量子阱层12的方向上，电流扩展层11中各电流扩展子层110的厚度也逐渐减小，所以，在N型电流扩展层11a中，各电流扩展子层110的厚度自下而上逐渐减小，而在P型电流扩展层11b中，各电流扩展子层110的厚度自上而下逐渐减小。可以理解的是，在本实施例的其他一些示例中，同一电流扩展层11中各电流扩展子层110的厚度也可以均匀一致。
另外，需要说明的是，虽然图1示出的发光芯片外延层10中两个电流扩展层10中均存在电流扩展子层110的厚度渐变，但在本实施例的其他一些示例中，发光芯片外延层10的两个电流扩展层11中，可以其中一个包括厚度渐变的电流扩展子层，另一个包括厚度一致的电流扩展子层。类似地，在一些示例提供的发光芯片外延层10中，N型电流扩展层11a与P型电流扩展层11b中均存在电流扩展子层110掺杂浓度渐变情况，但还有另外一些示例中，发光芯片外延层10的两个电流扩展层11中，其中一个包括掺杂渐变的电流扩展子层，另一个包括掺杂浓度不变或者掺杂浓度无规律变化的电流扩展子层。
在本实施例的一些示例中，电流扩展层11中可以包括Al xGa 1-xN，可选地，0.4≤x＜1，例如，x的取值可以为0.46、0.49、0.51、0.75、0.9等。AlGaN基的发光芯片外延层10可以制成AlGaN基紫外发光二极管，应用到消毒领域。还有一些示例中，x的取值可以为0，在这种情况下，电流扩展层11包括GaN， GaN基的发光芯片外延层10可以制得蓝绿光LED芯片，从而被广泛应用于照明、显示领域。
本实施例还提供一种基于上述发光芯片外延层10制得的发光芯片，请参见图2所示，该发光芯片2中包括发光芯片外延层10以及N电极20a与P电极20b，其中N电极20a与发光芯片外延层10中的N型电流扩展层11a电连接，P电极20b与发光芯片外延层10中的P型电流扩展层11b电连接。
在本实施例中并不具体限定发光芯片2的结构、发光颜色等，例如其可以为倒装结构，也可以正装结构，或者还可以为垂直结构；其可以为紫外发光芯片，也可以为蓝光芯片，或者还可以为绿光芯片。
本实施例提供的发光芯片外延层与发光芯片，N型电流扩展层中各电流扩展子层的掺杂浓度沿着生长方向逐渐降低，而P型电流扩展层中各电流扩展子层的掺杂浓度沿着生长方向逐渐升高，从而在保证电流扩展层高掺杂的情况下降低了电流扩展层与量子阱层之间的晶格差异，提升了发光芯片外延层的品质，增强了发光芯片的质量。
 本申请另一可选实施例：
本申请提供一发光芯片外延层的生长方法：
可以理解的是，生长发光芯片外延层需要生长量子阱层以及位于量子阱层相对两侧的电流扩展层。可选地，可以先生长N型电流扩展层，然后在N型电流扩展层之上生长量子阱层，随后再在量子阱层之上生长P型电流扩展层。
在本实施例中，发光芯片外延层的生长可以采用MOCVD（Metal-organic Chemical Vapor Deposition，金属有机化合物化学气相沉淀）工艺或MOMBE（Metal Organic Molecular-Beam Epitaxy）工艺（亦称作化学束外延CEB），在一些示例中生长发光芯片外延层时，可以向反应室中通入MO（高纯金属有机化合物）源进行外延生长。例如在生长电流扩展层时，需要向反应室内通入基础源与掺杂源，其中，基础源用于形成发光芯片外延层的基础晶体层，而掺杂源则用于对基础晶体层进行掺杂，若发光芯片外延层为AlGaN基，则基础源用于形成AlGaN；发光芯片外延层为GaN基，则基础源用于形成GaN。基础源通常包括金属源与氮源，如果发光芯片外延层为AlGaN基，则金属源需要提供Al原子与Ga原子；如果发光芯片外延层为GaN基，则金属源只需要提供Ga原子。如果发光芯片外延层为AlN基，则金属源中可以仅包括提供Al原子的铝源。在本实施例的一些示例当中，铝源可以包括但不限于TMAl（三甲基铝）。镓源包括但不限于TMGa（三甲基镓）和TEGa（三乙基镓）中的至少一种。例如，在本实施例的一些示例中，可以采用TMGa或TEGa作为镓源，在本实施例的另外一些示例当中，可以同时采用TMGa和TEGa作为镓源。
常见的氮源可以为NH 3（氨气），不过本领域技术人员可以理解的是，NH 3并不是唯一的氮源。
掺杂源的材质与电流扩展层的掺杂类型有关：如果是N型电流扩展层，则其掺杂源包括但不限于硅源、硼源与锗源中的任意一种。通常情况下，N型电流扩展层的掺杂源为硅源，例如SiH 4（甲硅烷），或者Si 2H 6（乙硅烷）。在本实施例的一些示例中，也可以同时将SiH 4与Si 2H 6作为硅源。如果是P型电流扩展层，则掺杂源包括但不限于镁源、锌源中的至少一种。例如，在本实施例的一些示例当中，P型电流扩展层的掺杂源为镁源，例如Cp 2Mg（二茂镁）等。
在本实施例中，电流扩展层中包括至少两个沿着生长方向依次层叠的电流扩展子层，所以在生长电流扩展层时，需要沿着生长方向逐层生长各电流扩展子层，每一个电流扩展子层的生长时间对应一个生长周期。在本实施例中，如果生长的是N型电流扩展层，则随着生长时间的后移，各生长周期对应的掺杂-基础比例逐渐降低，其中掺杂-基础比例是指掺杂源通入量与基础源通入量的比例，因此沿着生长方向，N型电流扩展层中各电流扩展子层中的掺杂浓度逐渐降低。如果生长的P型电流扩展层，则随着生长时间的后移，各生长周期对应的掺杂-基础比例逐渐升高，因此沿着生长方向，P型电流扩展层中各电流扩展子层中的掺杂浓度逐渐升高。换言之，在沿着靠近量子阱层的方向上，电流扩展层（不管是N型电流扩展层还是P型电流扩展层）中各电流扩展子层的掺杂浓度逐渐降低，生长该电流扩展层时，相邻两个生长周期中，更靠近量子阱层生长时间的一个向反应室内通入的掺杂源与基础源的比例更小。
可以理解的是，为了保证一个生长周期T1的掺杂-基础比例比另一个生长周期T2的掺杂-基础比例更小，则可以在两个生长周期向反应室内通入相同含量的基础源的情况下，通过控制两个生长周期内掺杂源的通入浓度c和/或通入流量f实现。例如，在一些示例中，生长电流扩展层时，保证T1与T2内掺杂源的通入流量相等，同时控制T1内掺杂源的通入浓度c1小于T2对应的通入浓度c2，或者，保证T1与T2内掺杂源的通入浓度相等，同时控制T1内掺杂源的通入流量f1小于T2内对应的通入流量f2，还有一些示例中，掺杂源在T1内的通入浓度c1、通入流量f2分别小于T2内的通入浓度c2、通入流量f2。
在本实施例的一些示例中，生长电流扩展层时，基础源在各生长周期内的通入浓度与通入流量均相同，生长N型电流扩展层时，随着生长时间的推移，掺杂源在各生长周期内的通入浓度c逐渐降低，通入流量f也逐渐降低；生长P型电流扩展层时，随着生长时间的推移，掺杂源在各生长周期内的通入浓度c逐渐升高，通入流量f也逐渐升高，这样便可实现沿着生长方向，N型电流扩展层中各电流扩展子层对应的掺杂浓度逐渐降低，而P型电流扩展层中各电流扩展子层对应的掺杂浓度逐渐升高的效果。应当明白的是，由于发光芯片外延层中量子阱层的掺杂浓度并不高，所以生长N型电流扩展层时逐渐降低各电流扩展子层的生长浓度，这样不仅可以保证N型电流扩展层本身晶体质量，同时也可以减小N型电流扩展与量子阱层之间的晶格差异，避免N型电流扩展层与量子阱层出现大的晶格失配，减少位错，提升发光芯片外延层的晶体质量。同样地，逐步提高P型电流扩展层中各电流扩展子层的掺杂浓度也是为了在实现P型电流扩展层高掺杂的同时减小P型电流扩展层与量子阱层之间的晶格失配，增强发光芯片外延层的晶体质量。
在实施例的一些示例中，同一生长周期内任意时刻通入反应室中的掺杂源与基础源的比例都是相同的，这种掺杂方式属于“均匀掺杂”。还有一些示例中，同一生长周期中至少存在两个时刻向反应室内通入的掺杂源与基础源的比例不同，相较于均匀掺杂方式，后一掺杂方式属于“非均匀掺杂”。
在本实施例的一些示例中，一个生长周期中包括至少两个循环周期，循环周期内至少包括第一时段t1与位于第一时段t1之后的第二时段t2。在本实施例的一些示例中，在一个循环周期中进行电流扩展层生长时，可以在第一时段t1内向反应室内通入氮源、金属源、掺杂源，其中，金属源、掺杂源在第一时段t1内的通入量分别为k1、k2；在第二时段t2内向反应室内通入氮源、金属源、掺杂源，金属源、掺杂源在第二时段t2内的通入量分别为k3、k4。其中，k1＞k3，k2＜k4，所以，第一时段t1中向反应室中通入的金属源比第二时段t2中通入的金属源更多，在一些示例中，第一时段t1内金属源的通入量远多于第二时段t2内金属源的通入量，第二时段t2内掺杂源的通入量远多于第一时段t1内掺杂源的通入量量。例如，在一些示例中，请参见图3示出的一个生长周期的多个循环周期内反应室中各MO源的通入时序示意图，在图3中，k1、k2、k3以及k4的取值均不为0，其中上升沿意味着一个时段的起点，而下降沿则对应该时段的终点，从图3中可以看出，循环周期由第一时段t1与第二时段t2构成，故第一时段t1与第二时段t2紧邻，第一时段t1的终点同时也是第二时段t2的起点。同时，结合图3可以知在循环周期内，氮源是长通的，例如在一种示例当中，反应室在整个循环周期内均处于氨气气氛下。
在本实施例的另一些示例中，k2与k3中的至少一个取值为0，例如，请参见图4所示，在图4中，第一时段t1内会向反应室内通入金属源与氮源，但不会通入掺杂源；而在第二时段t2内，会向反应室内通入掺杂源与氮源，但不会通入金属源，故，在图4对应的方案中，k2与k3的取值均为0。在这种方案中，金属源与掺杂源是交替通入的，在通入掺杂源的时候并不会同时通入金属源，因此掺杂源刚通入时可以在基础源所形成的基础晶体层表面形成一层薄的杂质薄膜，利用该杂质薄膜形成原子横向转移的扩散通道，使基础源原子在表面具有更大的扩散长度，增强了电流扩展层中二维层状生长特征，降低了晶格失配度。进一步地，二维层状生长特征的增强意味着横向生长速度的加快、横向生长速度与纵向生长速度比值的增大，这样可以使得刃位错更容易地沿着滑移面滑移，从而发生弯曲甚至湮灭，进而降低刃位错密度，提升晶体质量。另一方面，基础源与掺杂源的交替通入保证了掺杂源的原子有足够的时间吸附在已生长的基础晶体层表面，并向基础晶体层内部扩散，最终均匀分布在基础晶体层内，因此也提高了原子的解吸附概率，增强了发光芯片外延层的品质，提升了发光芯片的质量。
在本实施例的一些示例当中，第一时段t1的时长大于第二时段t2的时长，例如，第一时段t1的时长取值可以介于0~30s之间，例如，还有一些示例中，第一时段t1的时长取值为1~28s，例如25s、20s、18s或15s等；第二时段t2的时长的取值范围为0~20s之间，例如部分示例中第二时段t2的时长的取值为1~18s，如第二时段t2为17s、15s、10s、5s或3s等。
在本实施例的一些示例中，循环周期中还可以包括第三时段t3，请参见图5，第三时段t3位于第二时段t2之后，在第三时段t3内，既不向反应室内通入金属源，又不会向反应室内通入掺杂源，这样可以给杂质薄膜中的掺杂源原子留下充裕的扩展时间，从而保证杂质薄膜以原子形式均匀渗透分散到基础晶体层中，实现对基础晶体层的掺杂。在本实施例的一些示例中，第三时段t3中会继续向反应室内通入氮源，但另外一些示例中，第三时段t3会将氮源的通入也停止，在后一方案中，一个循环周期内，氮源向反应室内的通入也是脉冲式进行的。
在本实施例的一些示例中，在循环周期内除了包括第一时段t1与第二时段t2以外，还包括介于第一时段t1与第二时段t2之间的第四时段t4，请参见图6所示。在一些示例中，第四时段t4内既不向反应室内通入金属源，又不向反应室内通入掺杂源。还有一些示例中，第四时段t4可以同时通入金属源与掺杂源。
在本实施例的一些示例中，各生长周期所包含的循环周期的参数相同，循环周期的参数相同意味着循环周期的总时长相同、循环周期内的时段分布也相同，而如果两个循环周期的时段分布相同则说明这两个循环周期内所包含的时段相同，时段在循环周期内的排序相同，以及各时段的时长占比也相同。例如，在电流扩展层的一个电流扩展子层a对应的生长周期T1中，循环周期由第一时段t1与第二时段t2构成，其中第一时段t1的时长为18s，第二时段t2的时长为12s；该电流扩展层中的另一个电流扩展子层b对应的生长周期T2所包含的循环周期也是由时长为18s的第一时段t1与时长为12s的第二时段t2构成。在本实施例的一些示例中，在属于不同生长周期的循环周期的参数相同的情况下，相邻两个生长周期中更接近量子阱层的生长时间的一个所包含的循环周期的周期数目r更小。例如，假定生长周期T1对应于N型电流扩展层中的电流扩展子层a1，生长周期T2对应于N型电流扩展层中的电流扩展子层a2，电流扩展子层a1比电流扩展子层a2更靠近量子阱层，所以，电流扩展子层a1对应的T1比电流扩展子层a2对应的T2更接近量子阱层的生长时间，故，T1中所包含的循环周期的周期数目r1比T2中所包含的循环周期的周期数目r2更小。可以理解的是，因为不同生长周期中所包含的循环周期的参数相同，所以不同电流扩展子层在单个循环周期内生长的厚度差异不大，但因为靠近量子阱层生长时间的生长周期中所含有的循环周期更少，故，靠近量子阱层的电流扩展子层的厚度更薄，在上述示例中，电流扩展子层a1比电流扩展子层a2更薄。
在本实施例的另一些示例中，不同生长周期所包含的循环周期的参数不同，例如，循环周期R1、R2分别属于生长周期T1、T2，R1与R2这两个循环周期的总时长不同，不过周期内的时段分布相同，具体的，R2的总时长小于R1的总时长。在这种情况下，T1内一个循环周期的生长厚度大于T2内一个循环周期的生长厚度，故，即便不同的生长周期T1、T2包含相同周期数目r的循环周期，T1对应的电流扩展子层的厚度也大于T2对应的电流扩展子层的厚度。
在本实施例的一些示例中，生长电流扩展层的不同时刻下，反应室内的环境参数可以相同，这要求不同生长周期中反应室内的环境参数相同，相同生长周期不同循环周期内反应室的环境参数相同，同一循环周期内不同时段内反应室环境参数也相同。环境参数可以包括温度与压力，所以，在这些示例中，生长一电流扩展层的不同电流扩展子层时，反应室可以始终维持在相同的温度与压力条件下。例如一些示例中，生长电流扩展层时，反应室内的压力可以维持在50~250Torr之间。另一些示例中，反应室内的压力可以维持在200~250Torr之间。还有一些示例当中，压力可以维持在140~155Torr之间。除此以外，压力也可以处于80~140Torr间，或者是处于155~200Torr间，这里不再枚举。生长N型电流扩展层时，可以将反应室中的温度保持在850~1300℃之间。例如，在本实施例的一种示例中，反应温度可以维持在900~1250°C。在生长P型电流扩展层时，可以将反应室中的反应温度保持在750~1150℃之间。例如，在本实施例的一种示例中，反应温度可以维持在800~1100°C。
还有一些示例中，生长电流扩展层期间至少两个时刻下反应室的环境参数不同，例如，一些示例中不同生长周期中反应室内的环境参数不完全相同，例如可以是温度不同，或压力不同，或者是温度与压力均不同。所以，在这些示例中，可以在不同的生长周期内对反应室内的环境参数进行阶段性地控制，使得不同电流扩展子层在不同环境下生长。可以理解的是，在本实施例的一些示例中，也可以存在同一生长周期中不同循环周期对应的反应室环境参数不同的情况，或者是同一循环周期内不同时段对应的反应室环境参数不同的情况。
 本申请又一可选实施例：
本实施例首先提供一种发光芯片外延层，请参见图7所示的发光芯片外延层70的一种结构示意图，该发光芯片外延层70中从下至上依次包括衬底71，应力控制层72，N型电流扩展层73，准备层74，量子阱层75，电子阻挡层76，P型电流扩展层77，P型欧姆接触层78。
在生长光芯片外延层70时，是从衬底71的上表面向上逐层外延生长其他各层结构：将衬底71至于反应室中，对衬底71进行清洁、预热后在其表面生长应力控制层72，并在应力控制层72上逐层生长N型电流扩展层73的各N型电流扩展子层，以形成N型电流扩展层73。随后再在N型电流扩展层73上生长准备层74，并在准备层74上生长量子阱层75。量子阱层75生长完成以后，可在其上表面生长电子阻挡层76，接着在电子阻挡层76上逐层生长各P型电流扩展子层以形成P型电流扩展层77，随后在P型电流扩展层77上生长P型欧姆接触层78。
请参见图8与图9，N型电流扩展层73中从下至上依次包括第1子层731、第2子层732…第i子层73i…第n子层73n。P型电流扩展层77中从下至上依次包括第1子层771、第2子层772…第j子层77j…第m子层77m。
下面对N型电流扩展层73、P型电流扩展层77的生长方式进行说明，请参见图10所示的一个生长周期对应的生长流程示意图，同时结合图11示出的生长N型电流扩展层时反应室中各源的通入时序示意图，以及图12中示出的生长P型电流扩展层时反应室中各源的通入时序示意图：
S1002：在循环周期的第一时段t1向反应室内通入氮源、金属源，关闭掺杂源。
在循环周期的第一时段t1内向反应室内通入氮源与金属源，不通入掺杂源，这样可以利用氮源与金属源形成一层基础晶体层。本实施例中，发光芯片外延层70为AlGaN基的外延层，所以，基础晶体层就是AlGaN晶体层。在生长发光芯片外延层70时，以NH 3作为氮源，金属源包括镓源与铝源，例如以TMAl作为铝源，以TMGa（三甲基镓）和TEGa（三乙基镓）中的至少一种作为镓源。
在一些示例中，生长电流扩展层时，基础源的通入浓度、通入流量在各生长周期中保持不变，也即每个生长周期中，都按照相同的通入浓度与通入流量通入氮源，并且在需要向反应室内通入金属源时，都按照相同的通入浓度与通入流量进行通入。
S1004：在循环周期的第二时段t2向反应室内通入氮源，并按照当前生长周期对应的通入浓度与通入流量通入掺杂源，关闭金属源。
在循环周期的第二时段t2内向反应室内通入氮源与掺杂源，停止通入金属源，这样可以利用掺杂源在基础晶体层上形成一层薄的杂质薄膜，并且该杂质薄膜中的掺杂原子将在随后的时间内进行横向与纵向的扩散，均匀地渗入到基础晶体层中，实现对基础晶体层的掺杂。应当理解的是，杂质薄膜可以作为原子的扩散通道，增加原子的扩展长度，增强电流扩展层中的二维层状生长特征，降低晶格失配度。同时，二维层状生长特征明显，意味着横向生长速度与纵向生长速度比值得提升，这样可以使得外延晶体中刃位错更容易地沿着滑移面滑移，从而发生弯曲甚至湮灭，进而降低刃位错密度，显著提升晶体质量。另外，因为在第二时段t2内通入掺杂源时不会同时通入金属源，这样可以给掺杂原子更多的时间扩散，从而提升原子的解吸附概率，进一步提升发光芯片外延层70的品质。
在本实施例中，N型电流扩展层73对应的掺杂源为Si源，而P型电流扩展层77对应的掺杂源为Mg源。可选地，可以选择以SiH 4作为N型掺杂的Si源，以Cp 2Mg作为P型掺杂的Mg源。在本实施例中，因为一个电流扩展层中各电流扩展子层的掺杂浓度是逐渐变化的，对于N型电流扩展层73而言，沿着生长方向其所包含的各电流扩展子层的掺杂浓度逐渐降低，对于P型电流扩展层77，沿着生长方向其所包含的各电流扩展子层的掺杂浓度逐渐升高。因为一个生长周期生长一个电流扩展子层，所以不同生长周期向反应室内通入掺杂源的通入流量f与通入浓度c不同：生长N型电流扩展层时，随着生长时间的推移，各生长周期内掺杂源的通入浓度c逐渐降低，通入流量f也逐渐降低。生长P型电流扩展层时，随着生长时间的推移，各生长周期内掺杂源的通入浓度c逐渐升高，通入流量f也逐渐升高。可以理解的是，在本实施例的其他一些示例中，可以保持掺杂源在各生长周期的通入流量f不变，而逐渐改变其通入浓度c；另一些示例中，可以保持掺杂源在各生长周期的通入浓度c不变，而逐渐改变其通入流量f。还有一些示例中，掺杂源的通入浓度c与通入流量f甚至可以进行相反趋势的变化，例如，第i个生长周期内生长N型电流扩展层中的第i个N型电流扩展子层时，相对于第i-1个生长周期，可以减小掺杂源的通入流量f，同时增大掺杂源的通入浓度c，不过因为第i个N型电流扩展子层最终的掺杂浓度需要小于第i-1个N型电流扩展子层的掺杂浓度，因此第i个生长周期掺杂源通入流量f的减小幅度会大于第i个生长周期掺杂源通入浓度c的增大幅度。
在本实施例中，同一电流扩展子层中各处的掺杂浓度均匀，因此一个生长周期包含的若干个循环周期中，向反应室内通入掺杂源的通入浓度c一致，通入流量f也一致。
S1006：在循环周期的第三时段t3内保持掺杂源与金属源关闭。
在本实施例中，循环周期由第一时段t1、第二时段t2以及第三时段t3构成，上述三个时段依次排列。在第三时段中，既不向反应室内通入金属源，又不通入掺杂源，该时段留给杂质薄膜中的掺杂原子进行扩散。
在本实施例的一些示例当中，第一时段t1的时长大于第二时段t2的时长，例如，第一时段t1的时长取值可以介于0~30s之间，而第二时段t2的时长的取值范围为0~20s之间。一种示例中，t1为28s，t2为18s。一些示例中第三时段t3的时长也小于第一时段t1的时长；部分示例中，第三时段t3的时长等于第二时段t2的时长，还有部分示例中，第三时段t3的时长小于第二时段t2的时长；当然，本领域技术人员可以理解的是，在部分示例中也可以让第三时段t3的时长大于第二时段t2的时长，甚至还可以让第三时段t3的时长大于第一时段t1的时长。理论上，第三时段t3的时长越大，则掺杂原子的扩散时间越充裕，但同时发光芯片外延层70的生长效率也更低，所以，本实施例中在设置第三时段t3的时长时，需要综合考虑发光芯片外延层的生长效率与发光芯片外延层的晶体质量。
在本实施例的一些示例中，循环周期中除了包括第一时段t1、第二时段t2以及第三时段t3以外，还包括第四时段t4，第四时段t4位于第一时段t1与第二时段t2之间，在第四时段t4中可以同时通入金属源与掺杂源。由于位于第四时段t4之前的第一时段t1中金属源的通入量较高，而位于第四时段t4之后的第二时段t2中金属源的通入量为0，位于第四时段t4之前的第一时段t1中掺杂源的通入量为0，而位于第四时段t4之后的第二时段t2中掺杂源的通入量较高，因此在部分示例中，第四时段t4可以作为金属源通入量与掺杂源通入量渐变的过渡期，在该时段内金属源的通入流量与通入浓度逐渐降低，而掺杂源的通入流量与通入浓度逐渐升高。
S1008：判断当前生长周期中已完成的循环周期的累计数目是否达到预设数目。
若判断结果为是，则执行S1010，结束该生长周期进入下一生长周期；否则继续执行S1002。
S1010：结束当前生长周期进入下一生长周期。
一个生长周期所对应的 “预设数目”实际上就是该生长周期中所需要包含的循环周期的周期数目，预设数目的大小与该生长周期所生长的电流扩展子层的厚度相关。在本实施例中，不同生长周期所包含的循环周期的参数相同，换言之，即便两个循环周期分别属于两个生长周期，但这两个循环周期的总时长以及周期内时段分布均是相同的。生长N型电流扩展层时，随着生长时间的后移，各生长周期所包含的循环周期的周期数目r逐渐减小；生长P型电流扩展层时，随着生长时间的后移，各生长周期所包含的循环周期的周期数目r逐渐增大。
在判断当前生长周期中已完成的循环周期的累计数目已经达到预设数目时，则说明当前生长周期对应的电流扩展子层已经生长完成，下面需要生长下一个电流扩展子层；否则，说明当前生长周期所对应的电流扩展子层尚未生长完成，因此需要继续按照前一循环周期对应的掺杂源的通入流量f与通入浓度c进行新的一个循环周期的生长。例如，假定在生长第i个电流扩展子层时，需要进行6个循环周期的生长，并且在这6个循环周期中掺杂源的通入流量为f x6，通入浓度为c x6，在最新一个循环周期的生长结束后，确定当前生长周期中已完成的循环周期的累计数目为5，尚未小于6，因此接下来需要继续按照通入流量f x6，通入浓度c x6通入掺杂源进行一个循环周期的生长。
可以理解的是，在图11与图12中，不仅示出了各时刻中各MO源的通入或关闭，也通过脉冲高度的变化体现了各MO源的通入量的变化，掺杂源量的通入量会直接影响电流扩展子层的掺杂浓度，所以从图11中可以看出，掺杂源在前1~4个循环周期中脉冲高度一致，第5~7个循环周期中脉冲高度一致，第8~9个循环周期中脉冲高度一致，这意味着前1~4个循环周期对应的掺杂源通入量一致，第5~7个循环周期对应的掺杂源通入量一致，第8~9个循环周期对应的掺杂源通入量一致，因此，前1~4个循环周期对应于N型电流扩展层73中第1子层的形成过程，第5-7个循环周期对应于N型电流扩展层73中第2子层的形成过程，第8~9个循环周期对应于N型电流扩展层73中第3子层的形成过程……依次类推。同样地，在图12中，前1~2个循环周期中掺杂源对应的脉冲高度一致，第3~5个循环周期中脉冲高度一致，第6~9个循环周期中脉冲高度一致，这意味着前1~2个循环周期对应的掺杂源通入量量一致，第3~5个循环周期对应的掺杂源通入量一致，第6~9个循环周期对应的掺杂源通入量一致，因此，前1~2个循环周期对应于P型电流扩展层77中第1子层的形成过程，第3~5个循环周期对应于P型电流扩展层77中第2子层的形成过程，第6~9个循环周期对应于P型电流扩展层77中第3子层的形成过程……依次类推。
在本实施例中，生长N型电流扩展层73时，反应室中的温度在880~1200°C之间，生长P型电流扩展层77时，反应室中的温度在810~1000°C之间。生长N型电流扩展层73与P型电流扩展层时，反应室内的压力在55~240Torr之间。不过本领域技术人员可以理解的是，这里只是阐述了N型电流扩展层73、P型电流扩展层77生长时的大致压力环境与温度环境，在实际生长一个电流扩展层的过程中，除了保证反应室的温度与压力在对应范围内以外，还可以根据生长周期的不同，或者根据生长周期中循环周期的不同，或者是根据循环周期内时段的不同来对反应室内压力与温度进行分段调控。
本实施例中，发光芯片外延层的电流扩展层中各电流扩展子层的掺杂浓度沿着靠近量子阱层的方向逐渐降低，这样可以减小电流扩展层与量子阱层之间的晶格差异，降低晶格失配，提升外延晶体质量。同时，因为掺杂源通入时，金属源未通入，AlGaN停止生长，掺杂源可以在AlGaN上形成一层薄的杂质薄膜，有助于原子横向转移的扩散通道的形成，使Ga或Al的表面活性盖面，从而在表面具有更大的扩散长度，使得外延晶体横向生长速度大于纵向生长速度，刃位错更容易地沿着滑移面滑移，从而发生弯曲甚至湮灭，进而通过降低刃位错密度提高了晶体质量。而且，因为在分别在第一时段、第二时段通入金属源、掺杂源之后，还设置了一个第三时段，从而为杂质薄膜中的掺杂原子预留了足够的迁移扩散时间，进一步提升了发光芯片外延层的质量。
应当理解的是，本申请的应用不限于上述的举例，对本领域普通技术人员来说，可以根据上述说明加以改进或变换，所有这些改进和变换都应属于本申请所附权利要求的保护范围。

Claims (14)

  1. 一种发光芯片外延层，包括：
    量子阱层；
    N型电流扩展层与P型电流扩展层两个电流扩展层，所述N型电流扩展层与所述P型电流扩展层分别位于所述量子阱层相对的两侧；至少一个所述电流扩展层由至少两个沿着生长方向依次层叠的电流扩展子层构成，且各所述电流扩展子层的掺杂浓度在沿着靠近所述量子阱层的方向上逐渐减小。
  2. 如权利要求1所述的发光芯片外延层，其中，至少一个所述电流扩展层中各所述电流扩展子层的厚度在沿着靠近所述量子阱层的方向上逐渐减小，或者至少一个所述电流扩展层中各所述电流扩展子层的厚度相等。
  3. 如权利要求1或2所述的发光芯片外延层，其中，所述电流扩展层中包括Al xGa 1-xN，0.4≤x＜1，或x=0。
  4. 一种发光芯片，所述发光芯片包括：
    N电极；
    P电极；以及
    如权利要求1至3任一项所述的发光芯片外延层；
    其中，所述N电极与所述N型电流扩展层电连接，所述P电极与所述P型电流扩展层电连接。
  5. 一种发光芯片外延层的生长方法，包括生长量子阱层及位于所述量子阱层相对的两侧的电流扩展层；所述电流扩展层由依次层叠的至少两个电流扩展子层构成，生长所述电流扩展层包括：
    向反应室内通入与所述电流扩展层对应的基础源与掺杂源，逐层生长各所述电流扩展子层，一个所述电流扩展子层对一个生长周期，且相邻两个所述生长周期中，更接近所述量子阱层的生长时间的一个的掺杂-基础比例更小，所述掺杂-基础比例为所述掺杂源的通入量与所述基础源的通入量间的比值。
  6. 如权利要求5所述的生长方法，其中，生长所述电流扩展层的各所述生长周期中所述反应室的环境参数不完全相同，所述环境参数包括温度与压力中的至少一种。
  7. 如权利要求5所述的生长方法，其中，一所述生长周期中所述掺杂源的通入浓度为c，通入流量为f，相邻两个所述生长周期中，更接近所述量子阱层的生长时间的一个对应的所述掺杂源的所述通入浓度c与所述通入f更低。
  8. 如权利要求5至7任一项所述的生长方法，其中，所述基础源包括氮源与金属源，所述金属源包括铝源与镓源中的至少一种。
  9. 如权利要求8所述的生长方法，其中，一个生长周期包括至少两个循环周期，生长所述电流扩展子层包括：
    在所述循环周期的第一时段内向所述反应室内通入所述氮源、所述金属源与所述掺杂源，且所述金属源、所述掺杂源在所述第一时段内的通入量分别为k1、k2；
    在所述循环周期的第二时段内向所述反应室内通入所述氮源、所述金属源与所述掺杂源，且所述金属源、所述掺杂源在所述第二时段内的通入量分别为k3、k4，k3小于k1，k4大于k2，且所述第二时段在所述第一时段之后。
  10. 如权利要求9所述的生长方法，其中，所述k2与k3均为0。
  11. 如权利要求9所述的生长方法，其中，所述循环周期中还包括位于所述第二时段之后的第三时段，所述金属源、所述掺杂源在所述第三时段内的通入量均为0。
  12. 如权利要求9所述的生长方法，其中，所述循环周期中还包括介于所述第一时段与所述第二时段中的第四时段，所述金属源、所述掺杂源在所述第四时段内的通入量均为0。
  13. 如权利要求9所述的生长方法，其中，属于不同生长周期的所述循环周期的总时长相同，且周期内时段分布相同；相邻两个所述生长周期中，更接近所述量子阱层的生长时间的一个所包含的所述循环周期的周期数目r更小。
  14. 如权利要求9所述的生长方法，其中，各所述生长周期中包含的所述循环周期的周期数目r相同，属于不同生长周期的所述循环周期的总时长不同，但周期内的时段分布相同；相邻两个所述生长周期中，更接近所述量子阱层的生长时间的一个所对应的所述循环周期的总时长更小。
PCT/CN2022/085910 2022-04-08 2022-04-08 发光芯片、发光芯片外延层及其生长方法 WO2023193257A1 (zh)

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