TWI420696B - Light-emitting device and the manufacturing method thereof - Google Patents

Description

Light-emitting element and method of manufacturing same

The present invention relates to a light-emitting element, and more particularly to a light-emitting diode element having a multiple quantum well structure.

Light Emitting Diode (LED) has been widely used in automobiles, computers, communications, etc. due to its small size, long life, low driving voltage, low power consumption, fast response, and good shock resistance. In areas such as consumer electronics.

In general, the light-emitting diode has an active layer placed between two p-type & n-type cladding layers. When a driving current is applied to the electrodes above the two tie layers, the electrons and holes of the two tie layers are injected into the active layer, and combined in the active layer to emit light, the light is omnidirectional and will be in the light emitting diode element. Each surface is shot. Typically, the active layer can be a single quantum well structure layer (SQW) or a multiple quantum well structure layer (MQW). Compared with a single quantum well structure layer (SQW), multiple quantum well structure layers (MQW) have better photoelectric conversion efficiency, and even when the current is small, it can still be stacked through many barrier layers and well layers. A gap structure that converts current into light.

However, multiple quantum well structure layers are susceptible to carrier overflow and piezoelectric field effects, making it difficult for electrons and holes to be effectively confined to multiple quantum well structures for bonding, making it difficult to illuminate LEDs. Upgrade.

The present invention provides a light-emitting element comprising an n-type tie layer; a p-type tie layer; and an active layer between the n-type tie layer and the p-type tie layer. The active layer is formed by a plurality of energy barrier layers and a plurality of well layers alternately stacked to form a multiple quantum well structure.

The light-emitting element proposed by the invention comprises a multiple quantum well structure, and the p-type impurity is doped in the energy barrier layer to increase the number of holes, wherein the closer the doping concentration of the energy barrier layer to the n-type tie layer is, the closer to the p-type bondage The higher the doping concentration of the energy barrier layer of the layer is to form an energy barrier structure with a graded doping concentration.

The invention provides a multiple quantum well structure, wherein the p-type impurity doped in the energy barrier layer may be magnesium, and the doping concentration is 1×10 ¹⁶ to 5×10 ¹⁷ /cm ³ .

The present invention proposes a multiple quantum well structure in which the energy barrier layer is composed of gallium nitride (GaN) and the well layer is composed of indium gallium nitride (In _x Ga _1-x N, 0 < x < 1).

The present invention provides a multiple quantum well structure in which each of the energy barrier layers comprises at least one secondary energy barrier layer, and each of the energy barrier layers is composed of indium gallium nitride (InGaN), and the secondary energy barrier layer is made of gallium nitride (GaN). ) composed of. The p-type impurity is doped in the sub-barrier layer to increase the number of holes. The doped p-type impurity may be magnesium and has a doping concentration of 1×10 ¹⁶ to 5×10 ¹⁷ /cm ³ .

A first embodiment of the present invention is directed to a light-emitting element comprising an active layer. The active layer is formed by stacking a plurality of energy barrier layers and a plurality of well layers to form a multiple quantum well structure, wherein the energy barrier layer is doped with p-type impurities to increase the number of holes, and the closer to the n-type tie layer The lower the doping concentration of the barrier layer, the higher the doping concentration of the barrier layer closer to the p-type tie layer, to form an energy barrier structure with a graded doping concentration. In order to make the description of the embodiment more detailed and complete, the following description can be referred to in conjunction with the drawings of Fig. 1.

1 shows a first embodiment of an epitaxial structure of a light-emitting device according to the present invention. The epitaxial structure 1 includes a growth substrate 10, a buffer layer 20 formed on the growth substrate 10, and an n-type cladding layer. 30 is formed over the buffer layer 20, an active layer 40 is formed over the n-type tie layer 30, and a p-type tie layer 50 is formed over the active layer 40. The method of forming the epitaxial structure 1 includes providing a growth substrate 10; then, epitaxially growing a buffer layer 20 on the growth substrate 10 by metal-metal chemical vapor deposition (Metal-Organic Chemical Vapor Deposition) under the first growth condition. After the growth of the buffer layer 20 is completed, the n-type tie layer 30 is grown under the second growth condition. After the n-type tie layer 30 is completed, the active layer 40 is grown under the third growth condition, and the p-type tie layer 50 is grown under the fourth growth condition to form an epitaxial structure of the light-emitting element. Wherein, the lattice constant of the buffer layer 20 is between the n-type binding layer 30 and the growth substrate 10, which can improve the epitaxial quality and reduce the lattice defects. In the definition of the invention, the term "growth condition" is a group consisting of at least one process parameter set value selected from the group consisting of temperature, pressure and gas flow, and other process parameter settings. The active layer 40 grown under the third growth condition is formed by stacking a plurality of energy barrier layers 40A ₁ , 40A ₂ , , 40A _n (n>1) and a plurality of well layers 40B. Quantum well structure. In this embodiment, the energy barrier layers 40A ₁ , 40A ₂ , , 40A _{n are} composed of gallium nitride (GaN), and the well layer 40B is made of indium gallium nitride (In _x Ga _1-x N, 0<x <1) is composed. The energy barrier layer is doped with a p-type impurity such as magnesium (Mg) to increase the number of holes, and the closer to the n-type tie layer 30, the lower the doping concentration of the barrier layer, and the closer to the p-type tie layer 50. The doping concentration is higher to form an energy barrier layer structure having a graded doping concentration, and the doping concentration ranges from 1×10 ¹⁶ to 5×10 ¹⁷ /cm ³ . The multi-quantum well structure can achieve at least the following effects: 1. The higher the doping concentration of the barrier layer near the p-type tie layer, the more efficient the hole injection into the quantum well can be. 2. The lower the doping concentration of the barrier layer closer to the n-type tie layer, the more blocking effect on electrons, and the large amount of electrons overflowing to the p-side.

A second embodiment of the present invention is directed to a light-emitting element comprising an active layer. The active layer is formed by a plurality of energy barrier layers and a plurality of well layers alternately stacked to form a multiple quantum well structure, wherein each of the energy barrier layers comprises at least one secondary energy barrier layer to form a secondary energy barrier layer. Light-emitting element. In order to make the description of the embodiment more detailed and complete, the following description can be referred to in conjunction with the drawings of FIG. Fig. 2 is a view showing a second embodiment of the epitaxial structure of the light-emitting element according to the present invention. The epitaxial structure 2 is compared with the epitaxial structure 1, except that the structure of the active layer 40 is different, and the structure of the other layers is the same as the growth condition. The active layer 40 grown under the third growth condition is formed by stacking a plurality of energy barrier layers 40A and a plurality of well layers 40B to form a multiple quantum well structure, wherein each of the energy barrier layers 40A includes at least one Secondary barrier layer 40a. In this embodiment, the material forming the energy barrier layer 40A is indium gallium nitride (In GaN), the material forming the secondary energy barrier layer 40a is gallium nitride (GaN), and the material forming the well layer is indium gallium nitride ( In _x Ga _1-x N, 0 < x < 1). The design of such a multi-quantum well structure can reduce the energy band bending caused by the polarization charge between the energy barrier layer and the well layer, and can increase the bonding efficiency of the electron hole in the quantum well.

A third embodiment of the present invention relates to a light-emitting element comprising an active layer. The active layer is formed by a plurality of energy barrier layers and a plurality of well layers alternately stacked to form a multiple quantum well structure, wherein each of the energy barrier layers comprises at least one secondary energy barrier layer, and the secondary energy barrier layer is doped, for example. The p-type impurity of magnesium increases the number of holes to form a light-emitting element having a p-type impurity secondary barrier layer. In order to make the description of the embodiment more detailed and complete, the following description can be referred to in conjunction with the drawings of FIG. Fig. 3 shows a third embodiment of the epitaxial structure of the light-emitting element according to the present invention. The epitaxial structure 3 is compared with the epitaxial structure 2, except that the structure of the active layer 40 is different, and the growth of the other layers is the same as the growth condition. The active layer 40 grown under the third third growth condition is formed by staggering a plurality of barrier layers 40A and a plurality of well layers 40B to form a multiple quantum well structure, wherein each of the barrier layers 40A includes at least one Secondary barrier layers 40a ₁ , 40a ₂ , , 40a _n (n>1). In the present embodiment, the material forming the energy barrier layer 40A is indium gallium nitride (InGaN), and the material forming the secondary energy barrier layers 40a ₁ , 40a ₂ , and 40 a _n is gallium nitride (GaN), and is doped. For example, a p-type impurity of magnesium, wherein the doping concentration may be the same or the doping concentration of the secondary barrier layer is closer to the n-type binding layer 30, and the doping concentration of the secondary barrier layer closer to the p-type binding layer 50 is higher. To form a gradual doping concentration secondary energy barrier layer structure having a doping concentration ranging from 1×10 ¹⁶ to 5×10 ¹⁷ /cm ³ . The material forming the well layer is indium gallium nitride (In _x Ga _1-x N, 0 < x < 1). The design of such a multi-quantum well structure can reduce the energy band bending caused by the polarization charge between the energy barrier layer and the well layer, and can increase the bonding efficiency of the electron hole in the quantum well.

In the above embodiments, the buffer layer, the n-type tie layer, the p-type tie layer, and the material of the active layer comprise a group III-V compound, such as a material of a gallium nitride series or a gallium phosphide series. The growth substrate is, for example, a group comprising at least one material selected from the group consisting of sapphire, tantalum carbide, gallium nitride, and aluminum nitride. The buffer layer, the n-type tie layer, and the p-type tie layer may be a single layer or a multilayer structure, such as a superlattice structure. In addition, the luminescent epitaxial structure of the present invention is not limited to growing on the grown substrate in a grown manner, and other forms of formation, such as bonding directly by bonding or bonding to a thermally conductive or conductive substrate by a dielectric. It is within the scope of the invention.

Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the present invention, and it is intended to be able to make various changes without departing from the spirit and scope of the invention. And the scope of the present invention is defined by the scope of the appended claims.

1, 2, 3. . . Epitaxial structure

10. . . Growth substrate

20. . . The buffer layer

30. . . N-type binding layer

40. . . Active layer

40A. . . Energy barrier

40B. . . Well layer

40a. . . Secondary barrier

40a ₁ , 40a ₂ , , , 40a _n . . . Secondary barrier

50. . . P-type binding layer

The preferred embodiment of the present invention will be described in more detail in the description of the embodiments with the following figures:

1 is a schematic view showing an epitaxial structure 1 of Embodiment 1 of the present invention.

2 is a schematic view showing the epitaxial structure 2 of the second embodiment of the present invention.

Fig. 3 is a view showing the epitaxial structure 3 of the third embodiment of the present invention.

1. . . Epitaxial structure

10. . . Growth substrate

20. . . The buffer layer

30. . . N-type binding layer

40. . . Active layer

40A ₁ , 40A ₂ , , , 40A _n . . . Energy barrier

40B. . . Well layer

50. . . P-type binding layer

Claims (10)

A light-emitting element comprising: at least a semiconductor layer; and an active layer over the semiconductor layer and comprising a plurality of barrier layers stacked in a plurality of well layers with each other, wherein each of the plurality of barrier layers comprises At least one energy barrier. The light-emitting element according to claim 1, wherein the semiconductor layer is an n-type tie layer or a p-type tie layer. The light-emitting element of claim 1, wherein the sub-barrier layer is composed of gallium nitride (GaN). The light-emitting element of claim 1, wherein the barrier layer is composed of indium gallium nitride (InGaN). The light-emitting element according to claim 1, wherein the well layer is composed of indium gallium nitride (In _x Ga _1-x N, 0 < x < 1). The light-emitting element of claim 1, wherein the sub-barrier layer comprises p-type dopant impurities. The light-emitting element of claim 6, wherein the p-type dopant impurity comprises magnesium. The light-emitting element of claim 1, wherein the secondary barrier layer of each of the plurality of barrier layers comprises doping impurities of the same concentration. The light-emitting element of claim 1, wherein the lower the impurity concentration of the sub-barrier layer is, the lower the semiconductor layer is. A method of manufacturing a light-emitting device, the method comprising: growing a first electrical semiconductor layer; growing an active layer on the first electrical semiconductor layer; and growing a second electrical semiconductor layer on the active layer; The active layer includes a plurality of energy barrier layers stacked in a plurality of well layers with each other, and each of the plurality of energy barrier layers includes at least one secondary energy barrier layer.