Light-emitting diode

Abstract

A light-emitting diode, relating to the technical field of semiconductors. The light-emitting diode comprises: a first light-emitting unit, a first buffer layer, a first tunneling junction, a second buffer layer, and a second light-emitting unit which are sequentially stacked. The first light-emitting unit comprises a first semiconductor layer having a first conductivity type, the second light-emitting unit comprises a second semiconductor layer having a second conductivity type, and the first tunneling junction comprises a third semiconductor layer having the first conductivity type and a fourth semiconductor layer having the second conductivity type, wherein the first conductivity type is different from the second conductivity type. The bandgap width of the first buffer layer is between the bandgap width of the first semiconductor layer and the bandgap width of the third semiconductor layer. The bandgap width of the second buffer layer is between the bandgap width of the fourth semiconductor layer and the bandgap width of the second semiconductor layer.

Description

light-emitting diodes

[0001] This application claims priority to Chinese patent application No. 202311146567.5, filed on September 6, 2023, with the invention name “Light Emitting Diode”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure relates to the field of semiconductor technology, and in particular to a light emitting diode. Background Art

[0003] The luminous efficiency of red micro light emitting diodes (LEDs) is very low at low currents. By connecting PN junctions through epitaxial tunneling junctions, multiple PN junctions are connected in series to improve the luminous efficiency problem at low currents.

[0004] However, connecting multiple PN junctions through a tunnel junction will cause the LED voltage to increase significantly, resulting in no obvious improvement in lighting efficiency.

[0005] Summary of the Invention

[0006] The present disclosure provides a light emitting diode. The technical solution is as follows:

[0007] In a first aspect, an embodiment of the present disclosure provides a light emitting diode, comprising:

[0008] A first light-emitting unit, a first buffer layer, a first tunnel junction, a second buffer layer, and a second light-emitting unit stacked in sequence;

[0009] The first light emitting unit includes a first semiconductor layer having a first conductivity type, the second light emitting unit includes a second semiconductor layer having a second conductivity type, the first tunnel junction includes a third semiconductor layer having the first conductivity type and a fourth semiconductor layer having the second conductivity type, wherein the first conductivity type is different from the second conductivity type;

[0010] The band gap of the first buffer layer is between the band gaps of the first semiconductor layer and the third semiconductor layer, and the band gap of the second buffer layer is between the band gaps of the fourth semiconductor layer and the second semiconductor layer.

[0011] Optionally, the first semiconductor layer is a first P-type AlInP confinement layer, the first buffer layer is a first hole buffer layer, the second buffer layer is a first electron buffer layer, the second semiconductor layer is a second N-type AlInP confinement layer, the third semiconductor layer is a first P-type AlGaAs layer, and the fourth semiconductor layer is a first N-type GaAs layer.

[0012] Optionally, the first buffer layer is a P-type doped (AlyGa1-y)0.5In0.5P layer, and the value of y ranges from 0.3 to 1.

[0013] Optionally, the value of y gradually decreases along the direction from the first semiconductor layer to the first tunnel junction, the maximum value of y is 1, and the minimum value of y is 0.15-0.3.

[0014] Optionally, the doping concentration of the first buffer layer is 1.5E18 to 2.5E18 cm-3.

[0015] Optionally, the thickness of the first buffer layer is 20-100 nm.

[0016] Optionally, the second buffer layer is an N-type doped (AlzGa1-z)0.5In0.5P layer, and the value of z ranges from 0.3 to 1.

[0017] Optionally, the value of z gradually increases along the direction from the first tunnel junction to the second semiconductor layer, the maximum value of z is 1, and the minimum value of z is 0.15-0.3.

[0018] Optionally, the doping concentration of the second buffer layer is 2E18 to 3E18 cm-3.

[0019] Optionally, the second buffer layer has a thickness of 20-100 nm.

[0020] Optionally, the light emitting diode further comprises:

[0021] A third buffer layer, a second tunnel junction, a fourth buffer layer and a third light-emitting unit sequentially stacked on the second light-emitting unit;

[0022] The second light emitting unit further includes a fifth semiconductor layer having the first conductivity type, the third light emitting unit includes a sixth semiconductor layer having the second conductivity type, and the second tunnel junction includes a seventh semiconductor layer having the first conductivity type and an eighth semiconductor layer having the second conductivity type;

[0023] The band gap of the third buffer layer is between the band gaps of the fifth semiconductor layer and the seventh semiconductor layer, and the band gap of the fourth buffer layer is between the band gaps of the eighth semiconductor layer and the sixth semiconductor layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic structural diagram of a light emitting diode provided by an embodiment of the present disclosure;

[0025] FIG2 is a schematic structural diagram of a light emitting diode provided by an embodiment of the present disclosure;

[0026] FIG3 is a schematic structural diagram of another light emitting diode provided by an embodiment of the present disclosure;

[0027] FIG4 is a schematic structural diagram of another light emitting diode provided by an embodiment of the present disclosure;

[0028] FIG5 is a flow chart of a method for preparing a light emitting diode provided in an embodiment of the present disclosure.

[0029] Reference numerals: 10 - first light emitting unit; 20 - first buffer layer; 30 - first tunnel junction; 40 - second buffer layer; 50 - Second light-emitting unit; 60-third buffer layer; 70-second tunnel junction; 80-fourth buffer layer; 90-third light-emitting unit; 101-GaAs substrate; 102-N-type GaAs buffer layer; 103-N-type GaInP etching stop layer; 104-N-type GaAs ohmic contact layer; 105-N-type current spreading layer; 106-first N-type AlInP confinement layer; 107-first active layer; 108-first P-type AlInP confinement layer; 109-first hole buffer layer; 111-first electron buffer layer; 112-second N-type AlInP confinement layer; 113-second active layer; 114-second P-type AlInP confinement layer; 115-P-type current spreading layer; 116-second hole buffer layer; 118-second electron buffer layer; 119-third N-type AlInP confinement layer; 120-third active layer; 121-third P-type AlInP confinement layer. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0031] In related technologies, multiple PN junctions are connected via a tunnel junction consisting of a P-type AlGaAs layer and an N-type GaAs layer. Electrons can easily transition within the tunnel junction. On either side of the tunnel junction are a P-type AlInP confinement layer and an N-type AlInP confinement layer, respectively. The P-type AlInP confinement layer is adjacent to the P-type AlGaAs layer, while the N-type AlInP confinement layer is adjacent to the N-type GaAs layer.

[0032] There is a large energy band difference between the P-type AlInP confinement layer (bandgap width 2.45eV) and the P-type AlGaAs layer (bandgap width 1.4~1.9eV), and there is a large energy band difference between the N-type GaAs layer (bandgap width 1.4eV) and the N-type AlInP confinement layer (bandgap width 2.45eV). Electrons cannot jump well at the two interfaces, resulting in high voltage and low light efficiency, and cannot achieve the expected effect.

[0033] FIG1 is a schematic diagram of the structure of a light emitting diode provided by an embodiment of the present disclosure. Referring to FIG1 , the light emitting diode includes: a first light emitting unit 10, a first buffer layer 20, a first tunneling junction 30, a second buffer layer 40, and a second light emitting unit 50 stacked in sequence.

[0034] In which, the first light-emitting unit 10 includes a first semiconductor layer having a first conductivity type, the second light-emitting unit 50 includes a second semiconductor layer having a second conductivity type, and the first tunnel junction 30 includes a third semiconductor layer having the first conductivity type and a fourth semiconductor layer having the second conductivity type, wherein the first conductivity type is different from the second conductivity type.

[0035] The band gap of the first buffer layer 20 is between the band gaps of the first semiconductor layer and the third semiconductor layer. The band gap of the second buffer layer 40 is between the band gaps of the fourth semiconductor layer and the second semiconductor layer.

[0036] In the embodiment of the present disclosure, a first buffer layer with a moderate bandgap width is inserted between the first semiconductor layer and the third semiconductor layer, which reduces the energy band difference at the interface between the layers, allowing electrons to jump well between the interfaces; similarly, a first buffer layer with a moderate bandgap width is inserted between the second semiconductor layer and the fourth semiconductor layer, which reduces the energy band difference at the interface between the layers, allowing electrons to jump well between the interfaces; in summary, the addition of the first buffer layer and the second buffer layer is beneficial to electron jump, thereby achieving the purpose of reducing voltage and improving the light efficiency of the light-emitting diode.

[0037] In one example of the embodiment of the present disclosure, the first conductivity type refers to a P-type semiconductor type, and the second conductivity type refers to an N-type semiconductor type. The embodiment of the present disclosure uses this classification as an example to introduce the structure of the light-emitting diode.

[0038] Exemplarily, the first semiconductor layer is a first P-type AlInP confinement layer.

[0039] Optionally, the first light emitting unit 10 further includes a first N-type AlInP confinement layer and a first active layer.

[0040] Illustratively, the first buffer layer 20 is a first hole buffer layer.

[0041] Exemplarily, the second buffer layer 40 is a first electron buffer layer.

[0042] Exemplarily, the second semiconductor layer is a second N-type AlInP confinement layer.

[0043] Optionally, the second light emitting unit 50 further includes a second active layer and a second P-type AlInP confinement layer.

[0044] Exemplarily, the third semiconductor layer is a first P-type AlGaAs layer; and the fourth semiconductor layer is a first N-type GaAs layer.

[0045] In other examples of the embodiments of the present disclosure, the first conductivity type refers to an N-type semiconductor type, and the second conductivity type refers to a P-type semiconductor type.

[0046] Optionally, the light emitting diode further includes a buffer layer, an etching stop layer, an ohmic contact layer, an N-type current spreading layer, etc. located on the substrate and between the substrate and the first light emitting unit 10 .

[0047] Optionally, the light emitting diode further includes a P-type current spreading layer located on the second light emitting unit 50 .

[0048] Illustratively, the light emitting diode provided in the embodiment of the present disclosure may be a red light emitting diode.

[0049] FIG2 is a schematic diagram of the structure of a light-emitting diode provided by an embodiment of the present disclosure. Compared to FIG1 , the detailed structure of each film layer is further refined. Referring to FIG2 , the light-emitting diode includes: a GaAs substrate 101, an N-type GaAs buffer layer 102, an N-type GaInP etch-stop layer 103, an N-type GaAs ohmic contact layer 104, an N-type current spreading layer 105, a first N-type AlInP confinement layer 106, a first active layer 107, a first P-type AlInP confinement layer 108, a first hole buffer layer 109, a first tunneling junction 30, a first electron buffer layer 111, a second N-type AlInP confinement layer 112, a second active layer 113, a second P-type AlInP confinement layer 114, and a P-type current spreading layer 115.

[0050] Among them, the first N-type AlInP confinement layer 106, the first active layer 107 and the first P-type AlInP confinement layer 108 constitute the first light-emitting unit 10, the first hole buffer layer 109 is the first buffer layer 20, the first electron buffer layer 111 is the second buffer layer 40, and the second N-type AlInP confinement layer 112, the second active layer 113, and the second P-type AlInP confinement layer 114 constitute the second light-emitting unit 50.

[0051] Among them, the N-type GaAs buffer layer 102, the N-type GaInP etching stop layer 103, the N-type GaAs ohmic contact layer 104, the N-type current spreading layer 105, the first N-type AlInP confinement layer 106, the first active layer 107, the first P-type AlInP confinement layer 108, the first hole buffer layer 109, the first tunnel junction 30, the first electron buffer layer 111, the second N-type AlInP confinement layer 112, the second active layer 113, the second P-type AlInP confinement layer 114 and the P-type current spreading layer 115 are stacked in sequence on the GaAs substrate 101.

[0052] The first tunnel junction 30 includes a first P-type AlGaAs layer and a first N-type GaAs layer stacked in sequence; the bandgap width of the first hole buffer layer 109 is between the bandgap width of the first P-type AlInP confinement layer 108 and the bandgap width of the first P-type AlGaAs layer, and the bandgap width of the first electron buffer layer 111 is between the bandgap width of the second N-type AlInP confinement layer 112 and the bandgap width of the first N-type GaAs layer.

[0053] In the embodiment of the present disclosure, a first hole buffer layer with a moderate bandgap width is inserted between the first P-type AlGaAs layer and the first P-type AlGaAs layer, thereby reducing the energy band difference at the interface between the layers, so that electrons can well transition between the interfaces; similarly, a first electron buffer layer with a moderate bandgap width is inserted between the second N-type AlInP confinement layer and the first N-type GaAs layer, thereby reducing the energy band difference at the interface between the layers, so that electrons can well transition between the interfaces; in summary, the addition of hole and electron buffer layers is beneficial to electron transition, thereby achieving the purpose of reducing voltage and improving the light efficiency of the light-emitting diode.

[0054] For example, the thickness of the N-type GaAs buffer layer 102 is 150-300 nm, for example, 200 nm. The dopant of the N-type GaAs buffer layer 102 is Si2H6. The doping concentration of the N-type GaAs buffer layer 102 is 1E18-2E18 cm -3 , for example 1.5E18cm -3 .

[0055] For example, the thickness of the N-type GaInP etching stop layer 103 is 200-300 nm, for example, 250 nm. The dopant of the N-type GaInP etching stop layer 103 is Si2H6. The doping concentration of the N-type GaInP etching stop layer 103 is 2E18-6E18 cm -3 , for example 4E18cm -3 .

[0056] For example, the thickness of the N-type GaAs ohmic contact layer 104 is 30-60 nm, for example, 45 nm. The dopant of the N-type GaAs ohmic contact layer 104 is Si2H6. The doping concentration of the N-type GaAs ohmic contact layer 104 is 4E18-6E18 cm -3 , for example 5E18cm -3 .

[0057] For example, the N-type current spreading layer 105 is N-type (Al x Ga 1-x ) 0.5 In 0.5P layer, where 0.3 ≤ x ≤ 1. The thickness of the N-type current spreading layer 105 is 0.8 to 1.2 μm, for example, 1 μm. The dopant of the N-type current spreading layer 105 is Si2H6. The doping concentration of the N-type current spreading layer 105 is 1E18 to 4E18 cm -3 , for example 2.5E18cm -3 .

[0058] For example, the thickness of the first N-type AlInP confinement layer 106 is 200-300 nm, for example, 250 nm. The dopant of the first N-type AlInP confinement layer 106 is Si2H6. The doping concentration of the first N-type AlInP confinement layer 106 is 1E18-2E18 cm -3 , for example 1.5E18cm -3 .

[0059] Exemplarily, the first active layer 107 is a multi-quantum well layer. The thickness of the quantum wells in the multi-quantum well layer is 3 to 5 nm, for example, 4 nm; the thickness of the quantum barriers in the multi-quantum well layer is 5 to 10 nm, for example, 8 nm; and the number of periods in the multi-quantum well layer is 2 to 7, for example, 5.

[0060] For example, the thickness of the first P-type AlInP confinement layer 108 is 200-300 nm, for example, 250 nm. The dopant of the first P-type AlInP confinement layer 108 is Cp2Mg. The doping concentration of the first P-type AlInP confinement layer 108 is 1E18-1.5E18 cm -3 , for example 1.25E18cm -3 .

[0061] In the embodiment of the present disclosure, the first hole buffer layer 109 is a P-type doped (Al y Ga 1-y ) 0.5 In 0.5 P layer, the value of y ranges from 0.3 to 1, for example, 0.5. y Ga 1-y ) 0.5 In 0.5 The dopant of the P layer is Cp2Mg.

[0062] Among them, the value of y represents the value of Al in the whole (Al y Ga 1-y ) 0.5 In 0.5 The average content in the P layer.

[0063] Among them, P-type doped (Al y Ga 1-y ) 0.5 In 0.5The bandgap of P is 2.0 to 2.1 eV, the bandgap of the first P-type AlInP confinement layer is 2.45 eV, and the bandgap of the first P-type AlGaAs layer is 1.4 to 1.9 eV. Therefore, using the above materials as the first hole buffer layer can ensure that the bandgap of the first hole buffer layer is between the first P-type AlInP confinement layer and the first P-type AlGaAs layer.

[0064] In one example, the value of y gradually decreases along the direction from the first P-type AlInP confinement layer to the first tunnel junction, the maximum value of y is 1, and the minimum value of y is 0.15 to 0.3, for example, 0.2.

[0065] In this implementation, the value of y gradually decreases along the direction from the first P-type AlInP confinement layer to the first tunnel junction, so that the band gap width of the first hole buffer layer gradually decreases along the direction from the first P-type AlInP confinement layer to the first tunnel junction, so that the energy band differences at the interlayer interfaces between the first hole buffer layer and the first P-type AlInP confinement layer and between the first hole buffer layer and the first P-type AlGaAs layer are relatively small.

[0066] In other examples, the value of y may remain unchanged or may vary in other ways.

[0067] For example, the doping concentration of the first hole buffer layer is 1.5E18-2.5E18cm -3 , for example 2E18cm -3 .

[0068] In this implementation, if the doping concentration of the first hole buffer layer is too low, the voltage will be relatively high; if the doping concentration is too high, it means there are many impurities, which will absorb photons and cause a decrease in light efficiency; therefore, a suitable doping concentration is selected to ensure voltage and light efficiency.

[0069] Illustratively, the thickness of the first hole buffer layer is 20-100 nm, for example, 60 nm.

[0070] In this implementation, since the hole buffer layer uses AlGaInP with a low bandgap width, if the thickness is too thick, it will absorb more photons and cause a decrease in light efficiency; if the thickness is too thin, it will not play a hole buffering role, resulting in high voltage.

[0071] For example, the first P-type AlGaAs layer in the first tunnel junction 30 is a P-type AlGaAs layer. 1-a As layer, 0≤a≤0.3. The thickness of the first P-type AlGaAs layer is 10-40 nm, for example, 25 nm. The dopant of the first P-type AlGaAs layer is CBr4 or CCl4. The doping concentration of the first P-type AlGaAs layer is 0.5E20-2E20 cm -3 , for example 1E18cm-3 .

[0072] The thickness of the first N-type GaAs layer in the first tunnel junction 30 is 10-40 nm, for example, 25 nm. The dopant of the first N-type GaAs layer is Si2H6 or diethyltellurium. The doping concentration of the first N-type GaAs layer is 0.8E19-3E19 cm -3 , for example 2E18cm -3 .

[0073] In the embodiment of the present disclosure, the first electron buffer layer 111 is N-type doped (Al z Ga 1-z ) 0.5 In 0.5 The value of z in the P layer ranges from 0.3 to 1, for example, 0.5. The dopant of the first electron buffer layer is Si2H6.

[0074] Among them, the value of z represents the value of Al in the whole (Al z Ga 1-z ) 0.5 In 0.5 The average content in the P layer.

[0075] The bandgap of the first N-type GaAs layer is 1.4 eV, and the bandgap of the second N-type AlInP confinement layer is 2.45 eV. Using the above materials as the first electron buffer layer ensures that the bandgap of the first electron buffer layer is between the second N-type AlInP confinement layer and the first N-type GaAs layer.

[0076] In one example, the value of z gradually increases along the direction from the first tunnel junction to the second N-type AlInP confinement layer, the maximum value of z is 1, and the minimum value of z is 0.15 to 0.3, for example, 0.2.

[0077] In this implementation, the value of z gradually increases along the direction from the first tunnel junction to the second N-type AlInP confinement layer, so that the band gap width of the first electron buffer layer gradually increases along the direction from the first tunnel junction to the second N-type AlInP confinement layer, so that the energy band differences at the interlayer interfaces between the first electron buffer layer and the first N-type GaAs layer and between the first electron buffer layer and the second N-type AlInP confinement layer are relatively small.

[0078] In other examples, the value of z may remain unchanged or vary in other ways.

[0079] For example, the doping concentration of the first electron buffer layer is 2E18-3E18 cm -3 , for example 2.5E18cm -3 .

[0080] Exemplarily, the thickness of the first electron buffer layer is 20-100 nm, for example, 60 nm.

[0081] For example, the thickness of the second N-type AlInP confinement layer 112 is 200-300 nm, for example, 250 nm. The dopant of the second N-type AlInP confinement layer 112 is Si2H6. The doping concentration of the second N-type AlInP confinement layer 112 is 1E18-2E18 cm -3 , for example 1.5E18cm -3 .

[0082] Exemplarily, the second active layer 113 is a multi-quantum well layer. The thickness of the quantum wells in the multi-quantum well layer is 3 to 5 nm, for example, 4 nm; the thickness of the quantum barriers in the multi-quantum well layer is 5 to 10 nm, for example, 8 nm. The number of periods in the multi-quantum well layer is 2 to 7, for example, 5.

[0083] For example, the thickness of the second P-type AlInP confinement layer 114 is 200-300 nm, for example, 250 nm. The dopant of the second P-type AlInP confinement layer 114 is Cp2Mg. The doping concentration of the second P-type AlInP confinement layer 114 is 1E18-1.5E18 cm -3 , for example 1.25E18cm -3 .

[0084] Exemplarily, the P-type current spreading layer 115 is a P-type GaP layer. The thickness of the P-type current spreading layer 115 is 4 to 8 μm, for example, 6 μm. The dopant of the P-type current spreading layer 115 is Cp2Mg. The doping concentration of the P-type current spreading layer 115 is 1E18 to 8E18 cm -3 , for example 5E18cm -3 .

[0085] The embodiment of the present disclosure further provides another light-emitting diode, which may further include more tunneling junctions and PN junctions.

[0086] For example, a light-emitting diode includes three or more PN junctions, with a hole buffer layer, a tunneling junction, and an electron buffer layer between adjacent PN junctions. The PN junction includes an N-type confinement layer, an active layer, and a P-type confinement layer.

[0087] Figure 3 is a schematic diagram of the structure of a light-emitting diode provided by an embodiment of the present disclosure. Compared to Figure 1, this light-emitting diode includes more PN junctions. Referring to Figure 3 , this light-emitting diode also includes: a third buffer layer 60, a second tunneling junction 70, a fourth buffer layer 80, and a third light-emitting unit 90, which are sequentially stacked on the second light-emitting unit 50.

[0088] The second light-emitting unit 50 further includes a fifth semiconductor layer having the first conductivity type, the third light-emitting unit 90 includes a sixth semiconductor layer having the second conductivity type, and the second tunnel junction 70 includes a seventh semiconductor layer having the first conductivity type and an eighth semiconductor layer having the second conductivity type.

[0089] The bandgap of the third buffer layer 60 is between the bandgap of the fifth semiconductor layer and the bandgap of the seventh semiconductor layer. The bandgap of the fourth buffer layer 80 is between the bandgap of the eighth semiconductor layer and the bandgap of the sixth semiconductor layer.

[0090] Exemplarily, the fifth semiconductor layer is a second P-type AlInP confinement layer.

[0091] Exemplarily, the sixth semiconductor layer is a third N-type AlInP confinement layer; optionally, the third light-emitting unit 90 further includes a third active layer and a third P-type AlInP confinement layer.

[0092] Illustratively, the third buffer layer 60 is a second hole buffer layer.

[0093] Exemplarily, the fourth buffer layer 80 is a second electron buffer layer.

[0094] Exemplarily, the seventh semiconductor layer is a second P-type AlGaAs layer; and the eighth semiconductor layer is a second N-type GaAs layer.

[0095] Figure 4 is a schematic diagram of the structure of another light-emitting diode provided by an embodiment of the present disclosure. Compared to Figure 3 , the detailed structure of each film layer is further refined. Referring to Figure 4 , compared to Figure 2 , this light-emitting diode further includes: a second hole buffer layer 116 , a second tunneling junction 70 , a second electron buffer layer 118 , a third N-type AlInP confinement layer 119 , a third active layer 120 , and a third P-type AlInP confinement layer 121 .

[0096] The second hole buffer layer 116 is the third buffer layer 60 , the second electron buffer layer 118 is the fourth buffer layer 80 , and the third N-type AlInP confinement layer 119 , the third active layer 120 and the third P-type AlInP confinement layer 121 constitute the third light emitting unit 90 .

[0097] The second hole buffer layer 116 , the second tunnel junction 70 , the second electron buffer layer 118 , the third N-type AlInP confinement layer 119 , the third active layer 120 and the third P-type AlInP confinement layer 121 are located between the second P-type AlInP confinement layer 114 and the P-type current spreading layer 115 .

[0098] The second hole buffer layer 116 , the second tunnel junction 70 , the second electron buffer layer 118 , the third N-type AlInP confinement layer 119 , the third active layer 120 and the third P-type AlInP confinement layer 121 are sequentially stacked on the second P-type AlInP confinement layer 114 .

[0099] The second tunnel junction 70 includes a second P-type AlGaAs layer and a second N-type GaAs layer stacked in sequence; the bandgap width of the second hole buffer layer 116 is between the bandgap width of the second P-type AlInP confinement layer 114 and the bandgap width of the second P-type AlGaAs layer, and the bandgap width of the second electron buffer layer 118 is between the bandgap width of the third N-type AlInP confinement layer 119 and the bandgap width of the second N-type GaAs layer.

[0100] In the embodiment of the present disclosure, the second hole buffer layer 116 is a P-type doped (Al y Ga 1-y ) 0.5 In 0.5 P layer, the value of y ranges from 0.3 to 1, for example, 0.5. y Ga 1-y ) 0.5 In 0.5 The dopant of the P layer is Cp2Mg.

[0101] Among them, P-type doped (Al y Ga 1-y ) 0.5 In 0.5 The bandgap of P is 2.0 to 2.1 eV, the bandgap of the second P-type AlInP confinement layer is 2.45 eV, and the bandgap of the second P-type AlGaAs layer is 1.4 to 1.9 eV. Therefore, using the above materials as the second hole buffer layer can ensure that the bandgap of the second hole buffer layer is between the second P-type AlGaAs layer and the second P-type AlGaAs layer.

[0102] In one example, the value of y gradually decreases along the direction from the second P-type AlInP confinement layer to the second tunnel junction, the maximum value of y is 1, and the minimum value of y is 0.15 to 0.3, for example, 0.2.

[0103] In this implementation, the value of y gradually decreases along the direction from the second P-type AlInP confinement layer to the second tunnel junction, so that the band gap width of the second hole buffer layer gradually decreases along the direction from the second P-type AlInP confinement layer to the second tunnel junction, so that the energy band differences at the interlayer interfaces between the second hole buffer layer and the second P-type AlInP confinement layer and the second hole buffer layer and the second P-type AlGaAs layer are relatively small.

[0104] In other examples, the value of y may remain unchanged or may vary in other ways.

[0105] For example, the doping concentration of the second hole buffer layer is 1.5E18 to 2.5E18 cm -3 , for example 2E18cm -3 .

[0106] Illustratively, the thickness of the second hole buffer layer is 20-100 nm, for example, 60 nm.

[0107] For example, the second P-type AlGaAs layer in the second tunnel junction 70 is a P-type AlGaAs layer. 1-a As layer, 0≤a≤0.3. The thickness of the second P-type AlGaAs layer is 10-40 nm, for example, 25 nm. The dopant of the second P-type AlGaAs layer is CBr4 or CCl4. The doping concentration of the second P-type AlGaAs layer is 0.5E20-2E20 cm -3 , for example 1.5E18cm -3 .

[0108] The thickness of the second N-type GaAs layer in the second tunnel junction 70 is 10-40 nm, for example, 25 nm. The dopant of the second N-type GaAs layer is Si2H6 or diethyltellurium. The doping concentration of the second N-type GaAs layer is 0.8E19-3E19 cm -3 , for example 2E18cm -3 .

[0109] In the embodiment of the present disclosure, the second electron buffer layer 118 is N-type doped (Al z Ga 1-z ) 0.5 In 0.5 The value of z in the P layer ranges from 0.3 to 1, for example, 0.5. The dopant of the second electron buffer layer is Si2H6.

[0110] The second N-type GaAs layer has a bandgap of 1.4 eV, and the third N-type AlInP confinement layer has a bandgap of 2.45 eV. Using these materials as the second electron buffer layer ensures that the bandgap of the second electron buffer layer is between the third N-type AlInP confinement layer and the second N-type GaAs layer.

[0111] In one example, the value of z gradually increases along the direction from the second tunnel junction to the third N-type AlInP confinement layer, the maximum value of z is 1, and the minimum value of z is 0.15 to 0.3, for example, 0.2.

[0112] In this implementation, the value of z gradually increases along the direction from the second tunnel junction to the third N-type AlInP confinement layer, so that the band gap width of the second electron buffer layer gradually increases along the direction from the second tunnel junction to the third N-type AlInP confinement layer, so that the energy band differences at the interlayer interfaces between the second electron buffer layer and the second N-type GaAs layer and between the second electron buffer layer and the third N-type AlInP confinement layer are relatively small.

[0113] In other examples, the value of z may remain unchanged or vary in other ways.

[0114] For example, the doping concentration of the second electron buffer layer is 2E18-3E18 cm -3 , for example 2.5E18cm -3 .

[0115] Exemplarily, the thickness of the second electron buffer layer is 20-100 nm, for example, 60 nm.

[0116] For example, the thickness of the third N-type AlInP confinement layer 119 is 200-300 nm, for example, 250 nm. The dopant of the third N-type AlInP confinement layer 119 is Si2H6. The doping concentration of the third N-type AlInP confinement layer 119 is 1E18-2E18 cm -3 , for example 1.5E18cm -3 .

[0117] Exemplarily, the third active layer 120 is a multi-quantum well layer. The thickness of the quantum wells in the multi-quantum well layer is 3 to 5 nm, for example, 4 nm; the thickness of the quantum barriers in the multi-quantum well layer is 5 to 10 nm, for example, 8 nm; and the number of periods in the multi-quantum well layer is 2 to 7, for example, 5.

[0118] For example, the thickness of the third P-type AlInP confinement layer 121 is 200-300 nm, for example, 250 nm. The dopant of the third P-type AlInP confinement layer 121 is Cp2Mg. The doping concentration of the third P-type AlInP confinement layer 121 is 0.3E18-1E18 cm -3 , for example 0.5E18cm -3 .

[0119] The light-emitting diode can also have more PN junctions and tunnel junctions connecting the PN junctions. The structure can be designed with reference to the second hole buffer layer 116, the second tunnel junction 70, the second electron buffer layer 118, the third N-type AlInP confinement layer 119, the third active layer 120 and the third P-type AlInP confinement layer 121, that is, a structure including multiple periods based on Figure 2, each period including the second hole buffer layer 116, the second tunnel junction 70, the second electron buffer layer 118, the third N-type AlInP confinement layer 119, the third active layer 120 and the third P-type AlInP confinement layer 121.

[0120] It is worth noting that the embodiment of the present disclosure mainly provides an epitaxial structure in a light-emitting diode. In addition, the light-emitting diode may also include an electrode structure, which is connected to the epitaxial structure. For example, in the example of Figure 2, the two electrodes of the electrode structure are respectively connected to the N-type GaAs ohmic contact layer 104 and the P-type current spreading layer 115, thereby providing an electrical signal to the epitaxial structure to drive each light-emitting unit in the epitaxial structure to emit light. This embodiment of the present disclosure will not be elaborated on.

[0121] FIG5 is a flow chart of a method for preparing a light-emitting diode according to an embodiment of the present disclosure. Referring to FIG5 , the method includes:

[0122] 301. Provide a GaAs substrate.

[0123] 302. An N-type GaAs buffer layer, an N-type GaInP etching stop layer, an N-type GaAs ohmic contact layer, an N-type current spreading layer, a first N-type AlInP confinement layer, a first active layer, a first P-type AlInP confinement layer, a first hole buffer layer, a first tunnel junction, a first electron buffer layer, a second N-type AlInP confinement layer, a second active layer, a second P-type AlInP confinement layer and a P-type current spreading layer are sequentially formed on a GaAs substrate.

[0124] The first tunnel junction includes a first P-type AlGaAs layer and a first N-type GaAs layer stacked in sequence; the bandgap width of the first hole buffer layer is between the bandgap width of the first P-type AlInP confinement layer and the bandgap width of the first P-type AlGaAs layer, and the bandgap width of the first electron buffer layer is between the bandgap width of the second N-type AlInP confinement layer and the bandgap width of the first N-type GaAs layer.

[0125] In the embodiment of the present disclosure, a first hole buffer layer with a moderate bandgap width is inserted between the first P-type AlGaAs layer and the first P-type AlGaAs layer, thereby reducing the energy band difference at the interface between the layers, so that electrons can well transition between the interfaces; similarly, a first electron buffer layer with a moderate bandgap width is inserted between the second N-type AlInP confinement layer and the first N-type GaAs layer, thereby reducing the energy band difference at the interface between the layers, so that electrons can well transition between the interfaces; in summary, the addition of hole and electron buffer layers is beneficial to electron transition, thereby achieving the purpose of reducing voltage and improving the light efficiency of the light-emitting diode.

[0126] In the embodiment of the present disclosure, the first hole buffer layer is P-type doped (Al y Ga 1-y ) 0.5 In 0.5 P layer, the value of y ranges from 0.3 to 1. y Ga 1-y ) 0.5 In 0.5 The dopant of the P layer is Cp2Mg.

[0127] Among them, P-type doped (Al y Ga 1-y ) 0.5 In 0.5 The bandgap of P is 2.0 to 2.1 eV, the bandgap of the first P-type AlInP confinement layer is 2.45 eV, and the bandgap of the first P-type AlGaAs layer is 1.4 to 1.9 eV. Therefore, using the above materials as the first hole buffer layer can ensure that the bandgap of the first hole buffer layer is between the first P-type AlInP confinement layer and the first P-type AlGaAs layer.

[0128] In one example, the value of y gradually decreases along the direction from the first P-type AlInP confinement layer to the first tunnel junction, the maximum value of y is 1, and the minimum value of y is 0.15-0.3.

[0129] In this implementation, the value of y gradually decreases along the direction from the first P-type AlInP confinement layer to the first tunnel junction, so that the band gap width of the first hole buffer layer gradually decreases along the direction from the first P-type AlInP confinement layer to the first tunnel junction, so that the energy band differences at the interlayer interfaces between the first hole buffer layer and the first P-type AlInP confinement layer and between the first hole buffer layer and the first P-type AlGaAs layer are relatively small.

[0130] In other examples, the value of y may remain unchanged or may vary in other ways.

[0131] For example, the doping concentration of the first hole buffer layer is 1.5E18-2.5E18cm-3 .

[0132] Illustratively, the thickness of the first hole buffer layer is 20-100 nm.

[0133] In the embodiment of the present disclosure, the first electron buffer layer is N-type doped (Al z Ga 1-z ) 0.5 In 0.5 The value of z in the P layer ranges from 0.3 to 1. The dopant of the first electron buffer layer is Si2H6.

[0134] The bandgap of the first N-type GaAs layer is 1.4 eV, and the bandgap of the second N-type AlInP confinement layer is 2.45 eV. Using the above materials as the first electron buffer layer ensures that the bandgap of the first electron buffer layer is between the second N-type AlInP confinement layer and the first N-type GaAs layer.

[0135] In one example, the value of z gradually increases along the direction from the first tunnel junction to the second N-type AlInP confinement layer, the maximum value of z is 1, and the minimum value of z is 0.15-0.3.

[0136] In this implementation, the value of z gradually increases along the direction from the first tunnel junction to the second N-type AlInP confinement layer, so that the band gap width of the first electron buffer layer gradually increases along the direction from the first tunnel junction to the second N-type AlInP confinement layer, so that the energy band differences at the interlayer interfaces between the first electron buffer layer and the first N-type GaAs layer and between the first electron buffer layer and the second N-type AlInP confinement layer are relatively small.

[0137] In other examples, the value of z may remain unchanged or vary in other ways.

[0138] For example, the doping concentration of the first electron buffer layer is 2E18-3E18 cm -3 .

[0139] Exemplarily, the thickness of the first electron buffer layer is 20-100 nm.

[0140] In the embodiment of the present disclosure, when the hole buffer layer is grown, the molar flow ratio of phosphine (PH3) and the metal organic source (V / III ratio) is controlled to be 20-30, the growth rate can be controlled to be 0.45-0.55 nm / s, and the growth temperature can be 650-670°C. y Ga 1-y ) 0.5 In 0.5Under the P matching condition, the flow rate of TMAl gradually decreases and the flow rate of TMGa gradually increases to meet the requirement of gradually decreasing energy band, wherein phosphine can be an electronic special gas with a purity of more than 99.9999%.

[0141] During the growth of the hole buffer layer, the doping source Cp2Mg and the appropriate flow rate are introduced to make the carrier concentration of the hole buffer layer reach 1.5E18cm -3 ~2.5E18cm -3 .

[0142] In the embodiment of the present disclosure, when growing the electronic buffer layer, the molar flow ratio of phosphine (PH3) and the metal organic source (V / III ratio) is controlled to be 20-30, the growth rate can be controlled to be 0.45-0.55 nm / s, and the growth temperature can be 650-670°C. z Ga 1-z ) 0.5 In 0.5 Under the P matching condition, the flow rate of TMAl gradually increases and the flow rate of TMGa gradually decreases to meet the requirement of gradually rising energy bands, wherein phosphine can be an electronic special gas with a purity of more than 99.9999%.

[0143] During the growth of the electronic buffer layer, the doping source Si2H6 and the appropriate flow rate are introduced to make the carrier concentration of the electron buffer layer 2E18~3E18cm -3 .

[0144] Optionally, the light emitting diode manufacturing method further includes:

[0145] Before forming the P-type current spreading layer, a second hole buffer layer, a second tunnel junction, a second electron buffer layer, a third N-type AlInP confinement layer, a third active layer and a third P-type AlInP confinement layer are sequentially formed on the second P-type AlInP confinement layer;

[0146] The second tunnel junction includes a second P-type AlGaAs layer and a second N-type GaAs layer stacked in sequence; the bandgap width of the second hole buffer layer is between the bandgap widths of the second P-type AlInP confinement layer and the second P-type AlGaAs layer, and the bandgap width of the second electron buffer layer is between the bandgap widths of the third N-type AlInP confinement layer and the second N-type GaAs layer.

[0147] The above descriptions are merely embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A light emitting diode, comprising: A first light-emitting unit (10), a first buffer layer (20), a first tunnel junction (30), a second buffer layer (40), and a second light-emitting unit (50) stacked in sequence; The first light emitting unit (10) comprises a first semiconductor layer having a first conductivity type, the second light emitting unit (50) comprises a second semiconductor layer having a second conductivity type, the first tunnel junction (30) comprises a third semiconductor layer having the first conductivity type and a fourth semiconductor layer having the second conductivity type, wherein the first conductivity type is different from the second conductivity type; The bandgap width of the first buffer layer (20) is between the bandgap width of the first semiconductor layer and the bandgap width of the third semiconductor layer, and the bandgap width of the second buffer layer (40) is between the bandgap width of the fourth semiconductor layer and the bandgap width of the second semiconductor layer.

2. The light emitting diode according to claim 1, wherein: The first semiconductor layer is a first P-type AlInP limiting layer, the first buffer layer (20) is a first hole buffer layer, the second buffer layer (40) is a first electron buffer layer, the second semiconductor layer is a second N-type AlInP limiting layer, the third semiconductor layer is a first P-type AlGaAs layer, and the fourth semiconductor layer is a first N-type GaAs layer.

3. The light emitting diode according to claim 1 or 2, wherein: The first buffer layer (20) is a P-type doped (Al y Ga 1-y ) 0.5 In 0.5 P layer, the value range of y is 0.3-1.

4. The light emitting diode according to claim 3, wherein: The value of y gradually decreases along the direction from the first semiconductor layer to the first tunnel junction (30), the maximum value of y is 1, and the minimum value of y is 0.15-0.

3.

5. The light emitting diode according to claim 3, wherein: The doping concentration of the first buffer layer (20) is 1.5E18-2.5E18cm -3 .

6. The light emitting diode according to any one of claims 1 to 5, wherein: The second buffer layer (40) is N-type doped (Al z Ga 1-z ) 0.5 In 0.5 P layer, the value range of z is 0.3~1.

7. The light emitting diode according to claim 6, wherein: The value of z gradually increases along the direction from the first tunnel junction (30) to the second semiconductor layer, the maximum value of z is 1, and the minimum value of z is 0.15-0.

3.

8. The light emitting diode according to claim 6, wherein: The doping concentration of the second buffer layer (40) is 2E18-3E18cm -3 .

9. The light emitting diode according to any one of claims 1 to 8, wherein: The thickness of the first buffer layer (20) is 20-100 nm, and the thickness of the second buffer layer (40) is 20-100 nm.

10. The light emitting diode according to any one of claims 1 to 9, wherein: The light emitting diode further comprises: A third buffer layer (60), a second tunnel junction (70), a fourth buffer layer (80) and a third light-emitting unit (90) sequentially stacked on the second light-emitting unit (50); The second light emitting unit (50) further comprises a fifth semiconductor layer having the first conductivity type, the third light emitting unit (90) comprises a sixth semiconductor layer having the second conductivity type, and the second tunnel junction (70) comprises a seventh semiconductor layer having the first conductivity type and an eighth semiconductor layer having the second conductivity type; The bandgap width of the third buffer layer (60) is between the bandgap width of the fifth semiconductor layer and the bandgap width of the seventh semiconductor layer, and the bandgap width of the fourth buffer layer (80) is between the bandgap width of the eighth semiconductor layer and the bandgap width of the sixth semiconductor layer.

Images