KR101922934B1 - Nitride semiconductor light emitting device - Google Patents

Abstract

The present invention discloses a nitride semiconductor light emitting device. An N-type semiconductor layer and a P-type semiconductor layer of the disclosed invention; And an active layer of a multiple quantum well structure interposed between the N-type semiconductor layer and the P-type semiconductor layer, wherein a plurality of quantum well layers and a plurality of quantum barrier layers are alternately arranged, wherein the quantum barrier layer and the P- The first and second hole inducing layers including a semiconductor material used for the quantum barrier layer are laminated between the first and second hole inducing layers so that the energy levels of the P-type semiconductor layer, the second hole inducing layer, and the first hole inducing layer are sequentially lowered .
The nitride semiconductor light emitting device of the present invention has an effect of smoothly injecting holes into the active layer by inserting a semiconductor layer or a semiconductor layer doped with Mg between the active layer and the P-type semiconductor layer for use in the quantum well layer of the active layer.

Description

[0001] NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE [0002]

The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device in which hole injection is smoothly performed in an active layer to improve light emitting efficiency.

In general, nitrides of a Group III element such as gallium nitride (GaN) and aluminum nitride (AlN) used in a nitride semiconductor light emitting device have excellent thermal stability and have a direct transition type energy band structure. Recently, And are attracting much attention as materials for photoelectric elements in the ultraviolet region. In particular, blue and green light emitting devices using gallium nitride (GaN) have been used in various applications such as large-scale color flat panel displays, traffic lights, indoor lighting, high-density light sources, high resolution output systems and optical communication.

FIG. 1 illustrates a structure of a conventional nitride semiconductor light emitting device, and FIG. 2 illustrates an active layer region of the multiple quantum well structure of FIG. 1. Referring to FIG.

1 and 2, a conventional nitride semiconductor light emitting device includes a buffer layer 12 formed on an insulating substrate 10, an undoped layer 13 formed on the buffer layer 12, A layer 15, an active layer 30, a P-type semiconductor layer 40, and a transparent metal layer 45 are stacked. An N-type electrode 20 and a P-type electrode 50 are formed on the N-type semiconductor layer 15 and the P-type semiconductor layer 40 exposed to the outside.

The insulating substrate 10 may be made of a material suitable for growing a nitride semiconductor single crystal. For example, the insulating substrate 10 may be formed using a material such as sapphire. In addition to sapphire, zinc oxide (ZnO), gallium nitride (GaN), silicon carbide, SiC), aluminum nitride (AlN), or the like.

The active layer 30 is a region in which electrons and holes are recombined and has a multi-quantum well layer 31 and a quantum barrier layer 33, which are expressed by a general formula of InxGa1-xN (0? X? And has a quantum well structure. The emission wavelength emitted from the nitride semiconductor light emitting device is determined according to the kind of the material forming the active layer 30. [

The active layer 30 has a single quantum well (SQW) structure having one quantum well layer and a multi quantum well (MQW) structure having a plurality of quantum well layers less than about 100 angstroms. 2, the active layer 30 of the multiple quantum well structure has a higher luminous efficiency compared to a single quantum well structure, and has a high luminous output.

The light efficiency of such a nitride semiconductor light emitting device is originally determined by the probability of recombination of electrons and holes in the active layer, that is, the internal quantum efficiency. The improvement of the internal quantum efficiency is mainly studied in order to improve the structure of the active layer itself or increase the effective mass of the carrier.

However, since the mobility of holes is generally lower than the mobility of electrons, there arises a problem that the P-type semiconductor layer 40 can not be sufficiently supplied to the active layer 30.

If holes are not sufficiently supplied to the active layer 30 as described above, electrons that are not coupled out of the electrons supplied from the N-type semiconductor layer 15 are generated and the luminous efficiency is lowered.

Recently, a method of forming a nano-layered structure to improve the hole injection property in the active layer has been proposed, but the growth time for forming the nano-laminated structure is long and the overall productivity is lowered.

AlGaN-based electron barrier layer formation methods have been proposed for electron overflow phenomenon and smooth injection of holes. However, aluminum (Al) acts as a contaminant source during growth of a semiconductor layer, thereby deteriorating device characteristics. In addition, an additional process is required to maintain the reactor in a high temperature state for a long time in order to form an electron barrier layer.

The present invention relates to a nitride semiconductor light emitting device in which a semiconductor layer used for a quantum well layer of an active layer or a semiconductor layer doped with Mg is inserted between an active layer and a P-type semiconductor layer to allow holes to be injected smoothly into the active layer, The present invention has been made to provide a device.

It is another object of the present invention to provide a nitride semiconductor light emitting device in which a plurality of hole induction layers are formed between an active layer and a P-type semiconductor layer to improve luminous efficiency and production yield.

According to an aspect of the present invention, there is provided a nitride semiconductor light emitting device including: an N-type semiconductor layer and a P-type semiconductor layer; And an active layer of a multiple quantum well structure interposed between the N-type semiconductor layer and the P-type semiconductor layer, wherein a plurality of quantum well layers and a plurality of quantum barrier layers are alternately arranged, wherein the quantum barrier layer and the P- The first and second hole inducing layers including the semiconductor material used for the quantum well layer are laminated between the layers so that the energy levels of the P-type semiconductor layer, the second hole inducing layer, and the first hole inducing layer are sequentially lowered .

The nitride semiconductor light emitting device of the present invention is characterized in that a semiconductor layer used for a quantum well layer or a semiconductor layer doped with Mg is inserted between an active layer and a P-type semiconductor layer so that holes can be injected smoothly into the active layer, There is an improvement effect.

Further, the nitride semiconductor light emitting device of the present invention has the effect of improving the luminous efficiency and the production yield by forming a plurality of hole induction layers between the active layer and the P-type semiconductor layer.

FIG. 1 shows a structure of a conventional nitride semiconductor light emitting device.
2 is a view showing an active layer region of the multiple quantum well structure of FIG.
3 is a view illustrating an active layer structure of a multiple quantum well structure according to a first embodiment of the present invention.
4 is a view showing an active layer structure of a multiple quantum well structure according to a second embodiment of the present invention.
5 is a view showing an active layer structure of a multiple quantum well structure according to a third embodiment of the present invention.
6A and 6B are diagrams comparing defects generated in the nitride semiconductor light emitting device of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the size and thickness of the device may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

The embodiments of the present invention are modifications of the structure of the active layer region centering on the conventional nitride semiconductor light emitting device of FIG. Therefore, except for the structure of the active layer described below, the constituent parts such as the N-type electrode and the P-type electrode of the nitride semiconductor light emitting device described above can be directly applied to the embodiments of the present invention.

3 is a view illustrating an active layer structure of a multiple quantum well structure according to a first embodiment of the present invention.

Referring to FIG. 3, the active layer 230 of the nitride semiconductor light emitting device according to the first embodiment of the present invention has a multi quantum well (MQW) structure as follows. A first quantum barrier layer 231a, a second quantum barrier layer 231b, a third quantum barrier layer 231c and a fourth quantum barrier layer 231b are formed between the N-type semiconductor layer 115 and the P- A first quantum well layer 232a, a second quantum well layer 232b, and a second quantum well layer 232b are formed between the quantum barrier layers 231d, 231d, the fifth quantum barrier layer 231e, and the sixth quantum barrier layer 231f, 3 quantum well layer 232c, a fourth quantum well layer 232d and a fifth quantum well layer 232e.

The first and second hole inducing layers 240 and 250 are formed between the sixth quantum barrier layer 231f and the P-type semiconductor layer 140 of the active layer 230.

The N-type semiconductor layer 115 and the P-type semiconductor layer 140 may be formed of a compound III-nitride semiconductor layer such as (Al, In, Ga) N. For example, the N-type semiconductor layer 115 and the P-type semiconductor layer 140 may be N-type and P-type GaN, respectively, or N-type and P-type AlGaN.

The fourth quantum barrier layer 231d, the fifth quantum barrier layer 231e, the sixth quantum barrier layer 231b, the third quantum barrier layer 231c, the fourth quantum barrier layer 231d, the fifth quantum barrier layer 231e, The quantum barrier layer 231f may be formed by doping a GaN-based semiconductor material with a p-type (p +) impurity or an n-type (n +) impurity.

The first quantum well layer 232a, the second quantum well layer 232b, the third quantum well layer 232c, the fourth quantum well layer 232d and the fifth quantum well layer 232e are formed of InxGal- xN (0 < x < 1), and silicon may be doped to lower the driving voltage.

In addition, the first hole induction layer 240 is formed of an InGaN-based semiconductor layer, which is the quantum well layers, and the second hole inducing layer 250 is formed by implanting a Mg-based metal dopant into the InGaN-based semiconductor layer . When the Mg-based metallic dopant is implanted, the InGaN-based semiconductor layer is diffused and the operating voltage level is higher than that of the InGaN-based semiconductor layer.

As shown in the figure, the P-type semiconductor layer 140, the second hole inducing layer 250, and the first hole inducing layer 240 are sequentially lowered in operating voltage level. Therefore, the holes injected into the P-type semiconductor layer 140 can easily pass through the barrier layers of the second hole inducing layer 250 and the first hole inducing layer 240 and reach the sixth quantum barrier layer 231f of the active layer 230 Can be supplied. Further, the holes of the P-type semiconductor layer 140 can easily reach the active layer 230, so that the operating voltage of the nitride semiconductor light emitting device is lowered.

The nitride semiconductor light emitting device of the present invention has an effect of smoothly injecting holes into the active layer by inserting a semiconductor layer or a semiconductor layer doped with Mg between the active layer and the P-type semiconductor layer for use in the quantum well layer of the active layer.

Further, the nitride semiconductor light emitting device of the present invention has the effect of improving the luminous efficiency and the production yield by forming a plurality of hole induction layers between the active layer and the P-type semiconductor layer.

4 is a view showing an active layer structure of a multiple quantum well structure according to a second embodiment of the present invention.

Referring to FIG. 4, the active layer 230 of the nitride semiconductor light emitting device according to the second embodiment of the present invention includes an N-type semiconductor layer 115, an active layer 230, a third hole inducing layer 350, A hole-guiding layer 350 and a P-type semiconductor layer 140.

The active layer 230 includes a first quantum barrier layer 231a, a second quantum barrier layer 231b, a third quantum barrier layer 231c, a fourth quantum barrier layer 231d, a fifth quantum barrier layer 231e, And the sixth quantum barrier layer 231f and a quantum well layer 232a, a second quantum well layer 232b, a third quantum well layer 232c, and a fourth quantum well layer 232b, A well layer 232d and a fifth quantum well layer 232e.

The third hole inducing layer 350 is formed between the active layer 230 and the P-type semiconductor layer 140, and a quantum well layer is formed by diffusing an Mg-based metallic dopant in the InGaN-based semiconductor layer for forming quantum well layers. A fourth hole inducing layer 340 formed of an InGaN-based semiconductor layer is formed.

In the third hole inducing layer 350, an energy level rises at the boundary between the sixth quantum barrier layer 231f and the third hole inducing layer 350 due to diffusion of Mg, and the P-type semiconductor layer 140 The hole injected from the second hole transporting layer 350 can easily move to the third hole inducing layer 350 and the sixth quantum barrier layer 231f via the fourth hole inducing layer 340. [

Accordingly, the coupling ratio of holes and electrons of the active layer 230 is increased and the driving voltage of the light emitting device is lowered.

Therefore, the nitride semiconductor light emitting device of the present invention has an effect of smoothly injecting holes into the active layer by inserting a semiconductor layer or Mg-doped semiconductor layer used for the quantum well layer of the active layer between the active layer and the P-type semiconductor layer .

Further, the nitride semiconductor light emitting device of the present invention has the effect of improving the luminous efficiency and the production yield by forming a plurality of hole induction layers between the active layer and the P-type semiconductor layer.

5 is a view showing an active layer structure of a multiple quantum well structure according to a third embodiment of the present invention.

Referring to FIG. 5, the active layer 230 of the nitride semiconductor light emitting device according to the third embodiment of the present invention includes an N-type semiconductor layer 115, an active layer 230, a fifth hole inducing layer 440a, A hole-guiding layer 440b, and a P-type semiconductor layer 140.

The active layer 230 includes a first quantum barrier layer 231a, a second quantum barrier layer 231b, a third quantum barrier layer 231c, a fourth quantum barrier layer 231d, a fifth quantum barrier layer 231e, And the sixth quantum barrier layer 231f and a quantum well layer 232a, a second quantum well layer 232b, a third quantum well layer 232c, and a fourth quantum well layer 232b, A well layer 232d and a fifth quantum well layer 232e.

A fifth hole inducing layer 440a and a sixth hole inducing layer 440b formed of an InGaN-based semiconductor layer for forming quantum well layers are formed between the active layer 230 and the P-type semiconductor layer 140.

The energy level (energy barrier) is sequentially lowered from the P-type semiconductor layer 140 because the In injection amount of the fifth hole induction layer 440a is relatively larger than that of the sixth hole induction layer 440b Different). The holes injected from the P-type semiconductor layer 140 can be easily transferred to the sixth hole inducing layer 440b and the sixth quantum barrier layer 231f through the fifth hole inducing layer 440a.

Accordingly, the coupling ratio of holes and electrons of the active layer 230 is increased and the driving voltage of the light emitting device is lowered.

Therefore, the nitride semiconductor light emitting device of the present invention has an effect of smoothly injecting holes into the active layer by inserting a semiconductor layer or Mg-doped semiconductor layer used for the quantum well layer of the active layer between the active layer and the P-type semiconductor layer .

Further, the nitride semiconductor light emitting device of the present invention has the effect of improving the luminous efficiency and the production yield by forming a plurality of hole induction layers between the active layer and the P-type semiconductor layer.

6A and 6B are diagrams comparing defects generated in the conventional and the nitride semiconductor light emitting device of the present invention.

Referring to FIGS. 6A and 6B, after generating the same driving voltage and output in the conventional nitride semiconductor light emitting device and the nitride semiconductor light emitting device of the present invention, the occurrence of defects is compared.

The conventional nitride semiconductor light emitting device has a buffer layer 12, an undoped layer 13, an N-type semiconductor layer 15, an active layer 30 and a P-type semiconductor layer 40 sequentially formed on a sapphire insulating substrate 10 However, since the P-type semiconductor layer 40 is formed directly on the active layer 30, the incidence of defects is high when the semiconductor layer is grown due to uneven lattice constants.

Although the nitride semiconductor light emitting device of the second embodiment of the present invention is described below, the same applies to the first and third embodiments of the present invention.

However, the nitride semiconductor light emitting device according to the second embodiment of the present invention includes a buffer layer 112, an undoped layer 113, an N-type semiconductor layer 115, an active layer 130, 3 hole-guiding layer 350, a fourth hole-guiding layer 340, and a P-type semiconductor layer 140 are sequentially formed.

That is, since the P-type semiconductor layer 140 is formed after the hole induction layers serving as a buffer are stacked on the active layer 130, the occurrence of defects due to non-uniformity of the lattice constant during the growth of the semiconductor layer is remarkably reduced.

Therefore, even when the nitride semiconductor light emitting device is operated, the occurrence rate of defects of the conventional nitride semiconductor light emitting device is lowered, which is advantageous for device stability.

110: insulating substrate 112: buffer layer
113: Undoped layer 115: N-type semiconductor layer
130: active layer 240: first hole inducing layer
250: second hole guiding layer 140: P-type semiconductor layer

Claims (2)

An N-type semiconductor layer and a P-type semiconductor layer;
An active layer of a multiple quantum well structure interposed between the N-type semiconductor layer and the P-type semiconductor layer and having a plurality of quantum well layers and a plurality of quantum barrier layers alternately arranged; And
And a first and a second hole inducing layer interposed between the quantum barrier layer and the P-type semiconductor layer and including a semiconductor material used for the quantum well layer,
The energy level of the first and second hole inducing layers is lower than the energy level of the quantum barrier layer, the energy level of the second hole inducing layer is lower than the energy level of the P-type semiconductor layer, The energy level of the first hole-guiding layer is lower than the energy level of the inductive layer,
Wherein the first hole inducing layer adjacent to the quantum barrier layer is formed of an InGaN-based semiconductor layer, or the InGaN-based semiconductor layer is doped with Mg. An N-type semiconductor layer and a P-type semiconductor layer;
An active layer of a multiple quantum well structure interposed between the N-type semiconductor layer and the P-type semiconductor layer and having a plurality of quantum well layers and a plurality of quantum barrier layers alternately arranged; And
And a first and a second hole inducing layer interposed between the quantum barrier layer and the P-type semiconductor layer and including a semiconductor material used for the quantum well layer,
The energy level of the first and second hole inducing layers is lower than the energy level of the quantum barrier layer, the energy level of the second hole inducing layer is lower than the energy level of the P-type semiconductor layer, The energy level of the first hole-guiding layer is lower than the energy level of the inductive layer,
Wherein the second hole inducing layer adjacent to the P-type semiconductor layer is formed of an InGaN-based semiconductor layer, or the InGaN-based semiconductor layer is doped with Mg.

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