TWM617989U - Light-emitting device - Google Patents

Abstract

The present model provides a light-emitting element whose structure is sequentially formed from bottom to top: a substrate, a lower cladding layer, a lower confinement layer, an active layer, an upper confinement layer, an upper cladding layer, a window layer and A tunnel junction surface layer. The tunnel junction layer includes a heavily doped p-type layer and a heavily doped n-type layer. The heavily doped n-type layer is adjacently disposed above the heavily doped p-type layer, and the heavily doped p-type layer is disposed on Above the window layer, the heavily doped n-type layer is used as an ohmic contact layer to contact an external power source to facilitate ohmic contact. The doping concentration of the ohmic contact layer of the new type is greater than that of the traditional LED, so it has lower resistance than the ohmic contact layer of the traditional LED, which is conducive to the lateral diffusion of current, and the total luminous energy is also greater than that of the traditional LED. At the same time, the temperature of the active layer is It is also lower than traditional LEDs.

Description

Light-emitting element

The present invention relates to a light-emitting element with a better current distribution effect in the window layer.

Optical semiconductor devices such as light-emitting devices, which include light-emitting diodes (Light-Emitting Diode, LED) and laser diodes (Laser Diode, LD), light-emitting devices are formed by epitaxial technology on the semiconductor substrate pn Surface or pin connection to achieve the purpose of luminescence. Please refer to Figure 1. The light-emitting element (such as LED) in the conventional conventional technology is formed by epitaxial, and its structure from bottom to top includes: a substrate (substate) 1, a distributed Bragg reflector (Distributed Braggre) Flector, DBR layer 2, lower cladding layer 3, lower confinement layer 4, active layer 5, upper confinement layer 6, and upper cladding layer layer) 7 and a window layer (window layer) 8. There are also two contact layers (Contact), for example, a bottom electrode (electrode) C1 and a top electrode C2, below the substrate 1 is the bottom electrode C1, and above the window layer 8 is formed the top electrode C2, the bottom electrode C1 and the top electrode C2 respectively form an ohmic contact with the substrate 1 and the window layer 8 to provide electrical energy to the active layer 5 and inject carriers. The lower electrode C1, the substrate 1, the DBR layer 2 and the lower cladding layer 3 are of the first conductivity type, such as n-type, and the upper electrode C2, the window layer 8 and the upper cladding layer 7 are of the second conductivity type For example, for the p-type, the lower confinement layer 6, the active layer 5, and the upper confinement layer 4 are undoped. For example, the epitaxial chip structure of aluminum gallium indium phosphide (AlGaInP) LED is to sequentially grow the n-type DBR layer 2 and the n-type lower cladding layer on an n-type substrate 1 made of gallium arsenide (GaAs). 3, and the lower confinement layer 4, the active layer 5, and the upper confinement layer 6 composed of undoped AlGaInP, then the p-type upper cladding layer 7, and gallium phosphide (GaP) form the p-type window layer 8, and then GaP forms the p-type upper electrode C2.

Generally speaking, the window layer 8 is used as a current spreading layer, which utilizes the high conductivity (low resistance) of the window layer 8 to spread the current laterally to improve the luminous efficiency of the LED. The upper electrode C2 above the window layer 8 is generally circular for wiring, which is etched to make the area smaller than the window layer 8, so most of the current will be limited to the circular shape of the upper electrode C2. Below the area, and then through the window layer 8 to spread the current laterally. However, such a structural design is only suitable for low current (for example, less than 8 mA (milliampere)) operating conditions, because the lower current allows sufficient time for carriers to diffuse laterally in the window layer 8.

When in order to increase the total power of the LED light, it is usually input from the upper electrode C2 by increasing the current (for example, greater than or equal to 8mA). The high current cannot be as low as the low current in the window layer 8 Time lateral diffusion, in other words, compared to low current, under high current operating conditions, carriers are more confined under the circular area, so the carrier density under the circular area is greater, even if the window layer 8 No matter how thick the thickness is, it will not be able to spread the high current laterally in time. The inability of the aforementioned high current to diffuse laterally in time causes only a part of the quantum well structure of the active layer 5 to be used. In addition, the higher carrier density under the aforementioned circular area also causes the temperature of the active layer 5 to be higher when the LED is operating. For example, it is as high as 485°C (10mA at high current), but the higher temperature of the active layer will make the total luminous energy of the LED unable to increase effectively with the increase of the current.

Furthermore, as mentioned above, the upper electrode C2 must be manufactured in an etching manner, which makes it necessary to undergo an epitaxial and etching process when manufacturing the LED. Therefore, the manufacturing process is cumbersome, the risk is increased, and the yield is challenged.

In view of the above-mentioned problems, the object of the present invention is to provide a light-emitting device whose active layer temperature is lower during high current operation and the total light-emitting energy can be increased, and no etching process is required.

In order to achieve the above objective, the present invention discloses a light-emitting element, which at least includes: a substrate; a lower cladding layer, the lower cladding layer is disposed above the substrate; a lower confined layer, the lower confined layer is disposed on the lower cladding Above the layer; an active layer, the active layer is disposed above the lower confinement layer; an upper confinement layer, the upper confinement layer is disposed above the active layer; an upper cladding layer, the upper cladding layer is disposed on Above the upper confinement layer; a window layer, the window layer is arranged above the upper cladding layer; a tunnel interface layer, the tunnel interface layer is arranged above the window layer.

In another embodiment, the tunnel junction layer includes a heavily doped p-type layer and a heavily doped n-type layer, and the heavily doped n-type layer is adjacently disposed above the heavily doped p-type layer.

In another embodiment, the heavily doped p-type layer is disposed above the window layer.

In another embodiment, the area of an upper surface and the area of the lower surface of the tunnel junction layer are respectively equal to the area of an upper surface of a window layer of the window layer.

In another embodiment, a contact supplementary layer is provided above the tunnel junction layer.

In order to enable those with ordinary knowledge in the field to clearly understand the content of this new model, please refer to the following descriptions and diagrams.

First of all, please refer to Figure 2. The light-emitting element (Light-Emitting Diode) 100 of the present invention can be a light-emitting diode (Light-Emitting Diode, LED) and a laser diode (Laser Diode, LD). In order to facilitate the understanding of the spirit of the present invention, the following embodiments take the structure of the LED as an example. However, those skilled in the art should understand that the spirit and structure of the present invention are also applicable to LD. In the first embodiment, the light-emitting element 100 includes at least: a bottom electrode 10; a substrate 11, the substrate 11 is in contact with the bottom electrode 10, and the substrate 11 can be disposed above or below the bottom electrode 10; A distributed Bragg reflector (DBR) layer 12, the DBR layer 12 is disposed above the substrate 11, the DBR layer 12 can be in contact with the upper surface of the substrate 11; the lower cladding layer 13, the lower cladding layer 13 Is disposed above the DBR layer 12, the lower cladding layer 13 can be in contact with the upper surface of the DBR layer 12; the lower confinement layer 14, the lower confinement layer 14 is disposed above the lower cladding layer 13, The layer 14 can be in contact with the upper surface of the lower cladding layer 13; an active layer 15, the active layer 15 is disposed above the lower confinement layer 14, and the active layer 15 can be in contact with the upper surface of the lower confinement layer 14; An upper confinement layer 16, the upper confinement layer 16 is disposed above the active layer 15, the upper confinement layer 16 can be in contact with the upper surface of the active layer 15; an upper cladding layer 17, the upper cladding layer 17 is disposed Above the upper confinement layer 16, the upper cladding layer 17 can be in contact with the upper surface of the upper confinement layer 16; a window layer 18, the window layer 18 is disposed above the upper cladding layer 17, the window layer 18 can be in contact with the upper surface of the upper cladding layer 17; a tunnel junction layer TJ, the tunnel junction layer TJ is disposed above the window layer 18, the tunnel junction layer TJ can It is in contact with the upper surface of the window layer 18. The bottom electrode 10 and the tunnel junction layer TJ are respectively an ohmic contact layer to provide electrical energy to the active layer 15 and inject carriers. In other words, the structure of the light-emitting device 100 is sequentially formed by epitaxial technology from bottom to top: the substrate 11, the DBR layer 12, the lower cladding layer 13, the lower confinement layer 14, the active layer 15, The upper confinement layer 16, the upper cladding layer 17, the window layer 18, and the tunnel junction layer TJ, such as molecular beam epitaxy (MBE), metal organic vapor phase epitaxy (metal Organic vapor phase epitaxy (MOPVE), low pressure vapor phase epitaxial method (LPMOVPE) or metal organic chemical vapor deposition (MOCVD) and other related technologies are used in the reaction chamber. In-suit formation. Of course, the DBR layer 12 may not be provided. In this case, the lower cladding layer 13 is provided above the substrate 11, and the lower cladding layer 13 may be in contact with the upper surface of the substrate 11.

The bottom electrode 10 is a first conductivity type electrode, such as an n-type electrode, such as n-type gallium arsenide (GaAs). The substrate 11 is a first conductivity type substrate, for example, n-type GaAs. The DBR layer 12 is a first conductivity type DBR layer, such as an n-type DBR layer, and the DBR layer 12 may be aluminum gallium arsenide (AlGaAs). The lower cladding layer 13 is a first conductivity type cladding layer, for example, an n-type cladding layer, and the lower cladding layer 13 may be aluminum indium phosphide (AlInP). The material of the lower confinement layer 14 may be (Al _x Ga _1-x ) _0.5 In _0.5 P, where 0<x<1, for example, 0.65. The active layer 15 may be a light-emitting layer having a multiple quantum well structure. The multiple quantum well structure is composed of multiple stacked pairs (not shown in the figure) repeatedly stacked, and each stacked pair includes a well layer and a well layer. Barrier layer. The material of the active layer 15 may be (Al _y Ga _1-y ) _0.5 In _0.5 P, where 0<y<1, for example, 0.65. The material of the upper confinement layer 16 may be (Al _z Ga _1-z ) _0.5 In _0.5 P, where 0<z<1, for example, 0.65. The lower confinement layer 14, the active layer 15, and the upper confinement layer 16 are undoped. The upper cladding layer 17 is a second conductivity type cladding layer, for example, a p-type cladding layer, and the upper cladding layer 17 may be aluminum indium phosphide (AlInP).

The window layer 18 is a second conductivity type window layer, for example, a p-type window layer. The window layer 18 has a wider or indirect energy gap and higher conductivity. The window layer 18 can be GaP, GaAsP (gallium arsenide phosphorous) or AlGaAs. The window layer 18 may be GaP doped with magnesium (Mg).

The tunnel junction layer TJ may be a multilayer structure including a heavily doped second-type layer and a heavily doped first-type layer, such as a heavily doped p-type layer TJ1 and a heavily doped n-type layer TJ2, respectively. The hetero n-type layer TJ2 is adjacently arranged above the heavily doped p-type layer TJ1, in other words, the heavily doped first type layer is adjacently arranged above the heavily doped second type layer. The heavily doped p-type layer TJ1 of the tunnel junction layer TJ is disposed above the window layer 18, for example, the heavily doped p-type layer TJ1 of the tunnel junction layer TJ is adjacent to the window layer 18. The material of the tunnel junction layer TJ can be a material that matches with the substrate 11. For example, if the substrate 11 uses GaAs, the tunnel junction layer TJ can use GaAs, AlGaAs, InGaP (indium gallium phosphide). , AlInP (aluminum indium phosphide), AlGaInP or GaP.

Specifically, in the foregoing statement that the tunnel junction layer TJ is the ohmic contact layer, the heavily doped n-type layer TJ2 of the tunnel junction layer TJ is the ohmic contact layer, and is shown in FIG. 2 In this case, the area of the upper surface TJA and the area of the lower surface TJB of the tunnel junction layer TJ are respectively equal to the area of the upper surface 18A of the window layer of the window layer 18. Please compare the second figure representing Example 1 with the first figure representing Comparative Example 1. As mentioned above, since the heavily doped n-type layer TJ2 is the ohmic contact layer, the light-emitting element 100 in the embodiment of the present invention The heavily doped n-type layer TJ2 of 1 corresponds to the upper electrode (ohmic contact layer) in Comparative Example 1 of the traditional LED. electrode. Since the area of the upper surface TJA and the area of the lower surface TJB of the tunnel junction layer TJ are respectively equal to the area of the upper surface 18A of the window layer of the window layer 18, the heavily doped n-type layer TJ2 does not need to be as In Comparative Example 1 (Figure 1), the area of the upper electrode is reduced by etching to be smaller than the window layer. Therefore, compared with the conventional LED, the light-emitting element 100 of the present invention has the advantages of simple manufacturing process, reduced risk and improved yield.

The following table 1 lists the structure comparison table of the traditional LED comparative example 1.

Table 1 (Comparative Example 1) Floor Annotation Material Dopant Dopant content (atoms/cm ³ ) type 1 Lower electrode GaAs Si Greater than 1.0x10 ¹⁸ n 2 Base GaAs Si Greater than 1.0x10 ¹⁸ n 3 DBR layer AlGaAs Si 6.0x10 ¹⁷ n 4 Lower cladding layer AlInP Si 6.0x10 ¹⁷ n 5 Lower confinement layer (Al _0.65 Ga _0.35 ) _0.5 In _0.5 P - - - 6 Active layer (Al _0.65 Ga _0.35 ) _0.5 In _0.5 P - - - 7 Upper limit layer (Al _0.65 Ga _0.35 ) _0.5 In0.5P - - - 8 Overlay Al _0.5 In _0.5 P Mg 9.0x10 ¹⁷ p 9 Window layer GaP Mg 9.0x10 ¹⁷ p 10 Upper electrode* GaP C 1.0x10 ¹⁹ p *: The area of the upper electrode is smaller than the area of the window layer.

Table 2 below lists the structure comparison table of Embodiment 1 of the new light-emitting element 100.

Table 2 (Example 1) Floor Annotation Material Dopant Dopant content (atoms/cm ³ ) type 1 Lower electrode 10 GaAs Si Greater than 1.0x10 ¹⁸ n 2 Base 11 GaAs Si Greater than 1.0x10 ¹⁸ n 3 DBR layer 12 AlGaAs Si 6.0x10 ¹⁷ n 4 Lower cladding layer 13 AlInP Si 6.0x10 ¹⁷ n 5 Lower limit layer 14 (Al _0.65 Ga _0.35 ) _0.5 In _0.5 P - - - 6 Active layer 15 (Al _0.65 Ga _0.35 ) _0.5 In _0.5 P - - - 7 Upper limit layer 16 (Al _0.65 Ga _0.35 ) _0.5 In _0.5 P - - - 8 Upper cladding layer 17 Al _0.5 In _0.5 P Mg 9.0x10 ¹⁷ p 9 Window layer 18 GaP Mg 9.0x10 ¹⁷ p Tunnel junction surface layer TJ * Heavy doped p-type layer TJ1 GaP C Greater than 5.0x10 ¹⁹ p Heavily doped n-type layer TJ1 GaP Te Greater than 5.0x10 ¹⁹ n *: The area of the upper surface TJA and the area of the lower surface TJB of the tunnel junction layer TJ are respectively equal to the area of the upper surface 18A of the window layer of the window layer 18.

Table 3 below lists the total luminous energy of Example 1 and Comparative Example 1 of the new light-emitting element 100 under high current (greater than or equal to 8 mA) operating conditions. Please also refer to Figure 3.

Table Three The total luminous energy mW (milliwatts) under the operating current of 8mA (C) Operating current 10mA total luminous energy mW (D) (C)/(D) Comparative example 1 (A) 5.282 5.517 1.04 Example 1 (B) 5.484 5.941 1.08 (B)/(A) 1.0382 1.0769 -

Table 4 below lists the temperature of the active layer 15 of Example 1 of the new light-emitting element 100 and the active layer of Comparative Example 1 under the operating current of 10 mA.

Table Four Operating current 10mA Active layer of Comparative Example 1 (E) 485°C The active layer 15 of Example 1 (F) 390°C (F)-(E) -95℃

From Table 1 to Table 4 above, it can be seen that, compared with the conventional LED comparative example 1, the embodiment 1 of the new light-emitting element 100 of the present invention has the following advantages: (1) the ohmic contact layer of the embodiment 1 is n-type ( The heavily doped n-type layer TJ2), and the ohmic contact layer (upper electrode) of Comparative Example 1 is p-type. Since the resistance of the n-type is much lower than that of the p-type, the ohmic contact layer ( Compared with the ohmic contact layer (p-type upper electrode) of Comparative Example 1, the heavily doped n-type layer (TJ2) is more conducive to ohmic contact. (2) From Table 3, in terms of the total luminous energy at an operating current of 8 mA, Example 1 is 1.0382 times that of Comparative Example 1, and in terms of the total luminous energy at an operating current of 10 mA, Example 1 is Comparative Example 1. This is because the ohmic contact layer (the heavily doped n-type layer TJ2) of Example 1 is heavily doped (the doping concentration is higher than 5.0x10 ¹⁹ atoms/cm ³ ) and the ohmic contact layer of Comparative Example 1 The doping concentration of the (p-type upper electrode) is only 1.0x10 ¹⁹ atoms/cm ³ , so the ohmic contact layer of Example 1 has lower resistance than that of Comparative Example 1, so the ohmic contact layer of Example 1 is beneficial to current Lateral diffusion, when a high current is introduced, the current will first rapidly diffuse laterally; and the heavily doped n-type layer TJ2 of Example 1 has the same area as the window layer 18, so it has been diffused laterally in the ohmic contact layer. For current, the current lateral coverage area must be larger than the restricted circular area of Comparative Example 1. Therefore, the quantum well structure of the active layer 15 of Example 1 can be used in more parts, and the carrier recombination area is also relatively large. Therefore, the total luminous energy of Example 1 is greater than the total luminous energy of Comparative Example 1. For example, the total luminous energy of Example 1 is 5.484 mW at an operating current of 8 mA, which is greater than the total luminous energy of Comparative Example 1, which is 5.282 mW. (3) When a high current is introduced, the current lateral coverage area of the aforementioned example 1 must be greater than the restricted circular area of the comparative example 1, so the ohmic contact layer (the heavily doped n-type layer TJ2 ) The carrier density below must be lower than the carrier density below the ohmic contact layer (p-type upper electrode) of Comparative Example 1, so the temperature of the active layer 15 of Example 1 is only 390°C, which is much lower than that of Comparative Example 1. The temperature of the active layer is 485°C up to 95°C (Table 4), and the lower temperature of the active layer 15 enables the total luminescence energy of Example 1 to be effectively increased with the increase of current; for example, in Table 3, when When the operating current is increased from 8 mA to 10 mA, the total luminous energy of Comparative Example 1 is only increased to 1.04 times, but Example 1 can be increased to 1.08 times. (3) The unexpected finding is that based on the fact that the movement rate of carriers in the n-type semiconductor is greater than the movement rate of the carriers in the p-type semiconductor, in Comparative Example 1, electrons/holes are coupled in the upper half of the active layer to emit light. Most of the light field is in the upper half of the active layer, and the lower half of the active layer cannot be effectively used; however, embodiment 1 uses the tunnel junction layer TJ doped with species, so it is compared with the comparative example. 1. In terms of 1, the carrier moving from top to bottom in the tunnel junction layer TJ, the window layer 18, and the upper cladding layer 17 in Example 1 is greater than that in Comparative Example 1 from top to bottom. The moving speed of the electrode and the window layer makes the coupling of the light field L and the quantum well of the active layer 15 in the first embodiment more likely to be in the middle of the active layer 15 so that the upper and lower half of the active layer 15 All parts can be effectively used and compensate the light field deviation in the vertical direction, thereby increasing the modal gain and lowering the critical current value, and enabling the light-emitting element 100 to operate under high temperature conditions and have a high operating speed.

In addition, of course, a contact supplementary layer 19 can also be provided above the tunnel junction layer TJ, please refer to FIG. 4 together. The contact supplement layer 19 is made of n-type GaP doped with Si/Te, and its doping concentration is 5.0×10 ¹⁸ atoms/cm ³ .

The new type of light-emitting element is provided with a tunnel interface layer above the window layer. The heavily doped n-type layer (ohmic contact layer) of the tunnel interface layer corresponds to the p-type upper electrode (ohmic contact layer) in the traditional LED In contact with an external power source, the area of the upper surface and the area of the lower surface of the tunnel interface layer are respectively equal to the area of the upper surface of the window layer. Since the resistance of the n-type is much smaller than that of the p-type, the ohmic contact layer of the new light-emitting element is more conducive to ohmic contact. The doping concentration of the ohmic contact layer of the new type of light-emitting element is greater than that of the traditional LED, so the resistance of the ohmic contact layer of the new type is lower than that of the traditional LED, so the ohmic contact layer of the new type is beneficial to current With lateral diffusion, the total luminous energy is also greater than that of traditional LEDs, and the temperature of the active layer of the present invention is also lower than that of traditional LEDs.

However, the above are only the preferred embodiments of the present model, and should not be used to limit the scope of implementation of the present model, that is, simple equivalent changes and modifications made in accordance with the scope of the patent application for the present model and the description of the model, All are still within the scope of this new patent. In addition, any embodiment of the present invention or the scope of the patent application does not have to achieve all the objectives or advantages or features disclosed in the present invention. In addition, the abstract part and title are only used to assist the search of patent documents, not to limit the scope of the rights of this model.

[Prior Art] 1: base 2: DBR layer 3: Lower cladding layer 4: Lower limit layer 5: Active layer 6: Upper limit layer 7: Upper cladding layer 8: Window layer C1: Lower electrode C2: Upper electrode [This new model] 100: light-emitting element 10: Lower electrode 11: Base 12: DBR layer 13: Lower cladding layer 14: Lower limit layer 15: active layer 16: upper limit layer 17: Upper cladding layer 18: Window layer 18A: Upper surface of window layer 19: Contact supplementary layer L: light field TJ: Tunnel junction surface layer TJ1: heavily doped p-type layer TJ2: heavily doped n-type layer TJA: upper surface TJB: bottom surface

Figure 1 shows the structure of a traditional LED. Figure 2 is a structural diagram of the new type of light-emitting element. Figure 3 is a graph showing the relationship between the total luminous energy and the operating current of Example 1 and Comparative Example 1 of the new model. Figure 4 is a structural diagram of the new type of light-emitting element provided with a contact supplementary layer.

100: light-emitting element

10: Lower electrode

11: Base

12: DBR layer

13: Lower cladding layer

14: Lower limit layer

15: active layer

16: upper limit layer

17: Upper cladding layer

18: Window layer

18A: Upper surface of window layer

L: light field

TJ: Tunnel junction surface layer

TJ1: heavily doped p-type layer

TJ2: heavily doped n-type layer

TJA: upper surface

TJB: bottom surface

Claims (5)

A light-emitting element, which contains at least: A base A lower cladding layer, the lower cladding layer is disposed above the substrate; The lower confinement layer, the lower confinement layer is arranged above the lower cladding layer; An active layer, the active layer is disposed above the lower limited layer; An upper confined layer, the upper confined layer is arranged above the active layer; An upper cladding layer, the upper cladding layer is disposed above the upper confined layer; A window layer, the window layer being arranged above the upper cladding layer; and A tunneling surface layer, the tunneling surface layer is arranged above the window layer. The light-emitting device according to claim 1, wherein the tunnel junction layer includes a heavily doped p-type layer and a heavily doped n-type layer, wherein the heavily doped n-type layer is disposed adjacent to the heavily doped p-type layer Above the layer. The light-emitting device according to claim 2, wherein the heavily doped p-type layer is disposed above the window layer. The light emitting device according to claim 3, wherein the area of an upper surface and the area of the lower surface of the tunnel junction layer are respectively equal to the area of an upper surface of a window layer of the window layer. The light-emitting device according to claim 4, wherein a contact supplementary layer is provided above the tunnel junction layer.

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