KR101874873B1 - Light-emitting device - Google Patents

Abstract

The light emitting element includes a first conductivity type semiconductor layer; An active layer including a plurality of barrier layers and a plurality of well layers alternately formed on the first conductivity type semiconductor layer; And a second conductive semiconductor layer formed on the active layer, wherein at least one of the barrier layers includes a dopant.

Description

Light-emitting device

An embodiment relates to a light emitting element.

Light emitting diodes (LEDs) are semiconductor light emitting devices that convert current into light. The light emitting diode is widely used as a light source for a display, a light source for an automobile, and a light source for an illumination, and a light emitting diode Diodes can also be implemented.

A method of improving the structure of the active layer, a method of improving the current spreading, a method of improving the structure of the electrode, a method of improving the structure of the light emitting diode package Methods have been tried.

The embodiment provides a light emitting device having a novel structure.

The embodiment provides a light emitting device with improved quality and reliability.

The embodiment provides a light emitting device with improved light efficiency.

According to an embodiment, the light emitting element includes a first conductivity type semiconductor layer; An active layer including a plurality of barrier layers and a plurality of well layers alternately formed on the first conductivity type semiconductor layer; And a second conductive semiconductor layer formed on the active layer, wherein at least one of the barrier layers includes a dopant.

According to an embodiment, the light emitting element includes a first conductivity type semiconductor layer; A second conductivity type semiconductor layer; And an active layer including a plurality of barrier layers and a plurality of well layers alternately formed between the first and second conductivity type semiconductor layers, wherein a first barrier layer is formed in contact with the second conductivity type semiconductor layer A second barrier layer is formed spaced apart from the first barrier layer, a first well layer is formed between the first and second barrier layers, and the second barrier layer has a tunnel region for passing carriers therethrough Lt; RTI ID = 0.0 > dopant. ≪ / RTI >

The embodiment can improve the internal quantum efficiency by doping the barrier layer adjacent to the well layer of the active layer with a high concentration of dopant.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment.
2 is an enlarged cross-sectional view of an active layer of the light emitting device of FIG.
3 is a diagram showing an energy band diagram of the light emitting device according to the first embodiment.
FIG. 4 is a view showing a tunnel path formed in the energy band diagram of FIG. 3. FIG.
5 is a graph showing the internal quantum efficiency of the comparative example and the embodiment.
6 is a diagram showing an energy band diagram of a light emitting device according to the second embodiment.
7 is a diagram showing an energy band diagram of the light emitting device according to the third embodiment.

In describing an embodiment according to the invention, in the case of being described as being formed "above" or "below" each element, the upper (upper) or lower (lower) Directly contacted or formed such that one or more other components are disposed between the two components. Also, in the case of "upper (upper) or lower (lower)", it may include not only an upward direction but also a downward direction based on one component.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment.

Referring to FIG. 1, a light emitting device 10 according to an embodiment includes a substrate 12 and a light emitting structure 15 formed on the substrate 12.

The light emitting structure 15 may include a plurality of compound semiconductor layers formed of a compound semiconductor material of a group III-V element. The light emitting structure 15 may be formed by a metal organic chemical vapor deposition (MOCVD) method, a chemical vapor deposition (CVD) method, a plasma enhanced chemical vapor deposition (PECVD) method, a molecular beam epitaxy (Molecular Beam Epitaxy) and HVPE (Hydride Vapor Phase Epitaxy).

For example, the light emitting structure 15 may include a first conductive semiconductor layer 16, an active layer 20, and a second conductive semiconductor layer 18.

The first conductive semiconductor layer 16 is formed on the substrate 12, the active layer 20 is formed on the first conductive semiconductor layer 16, and the second conductive semiconductor layer 16 18 may be formed on the active layer 20.

The substrate 12 may be formed of at least one selected from the group consisting of sapphire (Al ₂ O ₃ ), SiC, Si, GaAs, GaN, ZnO, Si, GaP, InP and Ge.

A buffer layer 14 may be formed between the substrate 12 and the light emitting structure 15, specifically, the first conductivity type semiconductor layer 16.

The buffer layer 14 may also be formed of a compound semiconductor material of Group III-V elements described above.

The buffer layer 14 may be formed to reduce a lattice constant difference between the first conductive semiconductor layer 16 and the substrate 12.

The buffer layer 14 may more reliably alleviate the lattice difference between the first conductivity type semiconductor layer 16 and the substrate 12 and may further reduce the difference between the first conductivity type semiconductor layer 16, A plurality of layers may be formed in order to prevent cracks such as cracks from being generated in the active layer 20 and the second conductivity type semiconductor layer 18.

For example, the buffer layer 14 including a plurality of layers having Al _1-x In _x N containing different mol% of In may be formed, but the present invention is not limited thereto.

For example, the buffer layer 14 may contain no dopant or may include an n-type dopant, but the present invention is not limited thereto. The n-type dopant may include, for example, Si, Ge, Sn and the like.

The first conductive semiconductor layer 16 formed later due to the buffer layer 14 relieves the difference in lattice constant between the first conductive semiconductor layer 16 and the substrate 12 and is therefore stable without any defects such as cracks or voids. As shown in FIG.

The first conductive semiconductor layer 16 may be, for example, an n-type semiconductor layer including an n-type dopant. Wherein the n-type semiconductor layer is made of a compound semiconductor material of a group III-V element and has a composition formula of In _x Al _y Ga _1-xy N (0? X? 1, 0? _Y? 1, 0? _X + Lt; / RTI > At least one selected from the group consisting of InAlGaN, GaN, AlGaN, InGaN, AlN, InN and AlInN may be formed as the first conductivity type semiconductor layer 16 by this composition formula. The n-type dopant may include n-type dopants such as Si, Ge, and Sn.

The active layer 20 may be formed on the first conductive semiconductor layer 16.

The active layer 20 may include a first carrier injected through the first conductive semiconductor layer 16, for example, an electron or a hole, a second carrier injected through the second conductive semiconductor layer 18, For example, holes or electrons are combined with each other to emit light having a wavelength corresponding to a band gap difference of an energy band according to a material of the active layer 20. [

The active layer 20 of the embodiment may include any one of a single quantum well structure, a multiple quantum well structure (MQW), a quantum dot structure, and a quantum wire structure. The active layer 20 may have a multi-quantum structure in which compound semiconductors of group III-V elements are repeatedly formed in the period of the well layer and the barrier layer.

For example, the period of the InGaN well layer / GaN barrier layer, the period of the InGaN well layer / AlGaN barrier layer, the period of the InGaN well layer / the InGaN barrier layer, and the like. The band gap of the barrier layer may be formed to be larger than the band gap of the well layer.

The active layer 20 of the embodiment will be described later in more detail.

The second conductivity type semiconductor layer 18 may be formed on the active layer 20. The second conductivity type semiconductor layer 18 may be, for example, a p-type semiconductor layer including a p-type dopant. Wherein the p-type semiconductor layer is made of a compound semiconductor material of a group III-V element and has a composition formula of In _x Al _y Ga _1-xy N (0? X? 1, 0? _Y? 1, 0? _X + Lt; / RTI > At least one selected from the group consisting of InAlGaN, GaN, AlGaN, InGaN, AlN, InN and AlInN may be formed as the second conductivity type semiconductor layer 18 by this composition formula. The p-type dopant may include Mg, Zn, Ca, Sr, Ba, and the like.

Typically, the mobility of electrons is much higher than the mobility of holes. When the first conductivity type semiconductor layer 16 includes an n-type dopant and the second conductivity type semiconductor layer 18 includes a p-type dopant, electrons of the first conductivity type semiconductor layer 16 are rapidly The holes of the second conductivity type semiconductor layer 18 are supplied to the active layer 20 relatively slowly while being supplied to the active layer 20. Accordingly, electrons in the active layer 20 are relatively more electrons than electrons in the active layer 20, and electrons in some of the electrons that can not recombine with holes can not remain in the active layer 20, . Leakage current is generated by the electrons transferred to the second conductivity type semiconductor layer 18 without being involved in recombination with the holes in the active layer 20.

A blocking layer 17 may be formed between the active layer 20 and the second conductive semiconductor layer 18 to prevent a leakage current caused by the electrons.

The barrier layer 17 may be formed of a compound semiconductor material of a group III-V element.

The barrier layer 17 may be formed of a semiconductor material at least larger than the energy band gap of the active layer 20 in order to prevent electrons of the active layer 20 from moving to the second conductivity type semiconductor layer 18. [ have. For example, the barrier layer 17 may be formed of at least one selected from the group consisting of AlN, AlGaN, and AlGaInN.

The blocking layer 17 may include no or no p-type dopant, but is not limited thereto. The p-type dopant may include, for example, Mg, Zn, Ca, Sr, Ba, and the like.

The electrons of the active layer 20 stay in the active layer 20 without being moved to the second conductivity type semiconductor layer 18 by the blocking layer 17 larger than the energy band gap of the active layer 20.

Although not shown, a transparent conductive layer may be formed on the second conductive semiconductor layer 18. The transparent electrode layer may be formed of ITO, IZO (In-ZnO), GZO (Ga-ZnO), AZO (Al- ZnO) , Ni / IrOx / Au, and Ni / IrOx / Au / ITO.

A reflective conductive layer (not shown) may be formed instead of the transparent conductive layer. The reflective conductive layer may include at least one selected from the group consisting of silver (Ag), aluminum (Al), platinum (Pt), and palladium (Pd) having high reflection efficiency.

Although not shown, a first electrode (not shown) may be formed on the second conductive semiconductor layer 18. In addition, a second electrode (not shown) may be formed in a region where a part of the first conductivity type semiconductor layer 16 is exposed. The first and second electrodes provide power to the light emitting device 10. This structure can be termed a lateral structure. The embodiments can be applied to a vertical structure or a flip-chip structure in addition to the horizontal structure.

Mesa etching may be performed to expose the first conductivity type semiconductor layer 16 before forming the second electrode.

2 is an enlarged cross-sectional view of an active layer of the light emitting device of FIG.

Referring to FIG. 2, the active layer 20 according to the embodiment may be formed of a multiple quantum well structure (MQW).

The active layer 20 includes a plurality of well layers 24_1, 24_2, ..., 24_ (n-2), 24_n and a plurality of barrier layers 22_1, 22_2, ..., 22_ May be alternately laminated on the first conductivity type semiconductor layer 16.

For example, when the first conductivity type semiconductor layer 16 includes an n-type dopant, the well layer 24_n may be formed in contact with the first conductivity type semiconductor layer 16.

For example, when the second conductivity type semiconductor layer 18 includes a p-type dopant, the barrier layer 22_1 may be formed in contact with the second conductivity type semiconductor layer 18.

A barrier layer 17 is formed between the active layer 20 and the second conductivity type semiconductor layer 18 so that the barrier layer 22_1 may be formed in contact with the barrier layer 17.

For example, the first barrier layer 22_1, the first well layer 24_1, the second barrier layer 22_2, the second well layer 24_2, the third barrier layer 22_3, (N-2) -th well layer 24_3, the fourth barrier layer 22_4, ..., the (n-2) -th barrier layer 22_ (N-1) th barrier layer 22_ (n-1), the (n-1) th well layer 24_ ) May alternately or alternately be disposed.

The n-type well layer 24_n may be in contact with the first conductivity type semiconductor layer 16.

An n-type well layer 24_n may be formed in contact with the first conductivity type semiconductor layer 16 so that electrons of the first conductivity type semiconductor layer 16 may be easily supplied to the active layer 20. [

The first barrier layer 22_1 serves as a barrier to prevent electrons in the first well layer 24_1 contacting the first barrier layer 22_1 from moving to the second conductivity type semiconductor layer 18 .

The thicknesses of the plurality of barrier layers 22_1, 22_2, ..., 22_ (n-1), and 22_n may be the same or different from each other. The thicknesses of the plurality of well layers 24_1, 24_2, ..., 24_ (n-2), 24_n may be the same or different from each other.

The thicknesses of the barrier layers 22_1, 22_2, ..., 22_ (n-1), and 22_n and the thicknesses of the well layers 24_1, 24_2, ..., 24_ Or different from each other.

As shown in FIG. 3, a plurality of barrier layers 22_1, 22_2, ..., 22_ (n-1), 22_n are formed in a plurality of well layers 24_1, 24_2, ..., 24_ , 24_n).

Although only the conduction band energy diagram is shown in FIG. 3, there is also a valance band energy diagram that is symmetric with the conduction band based on the energy level.

Since the balance band energy diagram and the conduction band energy diagram have the same shape, the conduction band energy diagram is shown for convenience of explanation.

The electrons of the first conductivity type semiconductor layer 16 may be filled from the n-type well layer 24_n of the active layer 20 adjacent to the first conductivity type semiconductor layer 16. For example, when electrons are filled in the n-th well layer 24_n of the active layer 20 and the n-th well layer 24_n is filled, (n-1)). In this way, electrons are filled in the respective well layers 24_1, 24_2, ..., 24_ (n-2), 24_n of the active layer 20, and these electrons recombine with the holes existing in the balance band Light can be generated.

The portion where the light amount is most generated may be the first well layer 24_1 adjacent to the second conductivity type semiconductor layer 18 or the barrier layer 17.

However, it is not easy for electrons to move to the first well layer 24_1 by the second barrier layer 22_2 adjacent to the first well layer 24_1.

In order to solve this problem, the second barrier layer 22_2 may include a dopant doped with a high concentration.

The dopant may include an n-type dopant or a p-type dopant. The n-type dopant may include n-type dopants such as Si, Ge, and Sn. The p-type dopant may include Mg, Zn, Ca, Sr, Ba, and the like.

In other words, the first barrier layer 22_1 and the third barrier layer 22_3 to 22_n do not include any dopant, and only the second barrier layer 22_n is doped with a high concentration . ≪ / RTI >

By this dopant doped to the high concentration, the energy band of the second barrier layer 22_2 can be bent as shown in FIG. That is, the energy band of the second barrier layer 22_2 has a peak point adjacent to the first well layer 24_1, and is bent into a concave curve from the peak point. Accordingly, a tunnel region (A) through which the electrons can pass by the tunneling effect can be formed around the peak point.

The width w of the tunnel region A becomes narrow as the energy band of the second barrier layer 22_2 is warped into a concave curve so that electrons can pass through the tunnel region A. [

Normally, electrons must pass over the energy band of the barrier layer to the next well layer. Since the energy band of the barrier layer is higher toward the well layer, it is not easy for the electrons to pass the energy band of the barrier layer.

On the other hand, in the embodiment, instead of passing the energy band of the second barrier 22_n, the electrons pass through the tunnel region A formed in the second barrier layer 22_2 and pass through the next well layer such as the first well layer 24_1 ), Electrons can be more easily moved to the first well layer 24_1. As described above, since the electrons are more easily provided to the first well layer 24_1, the probability of recombination with the holes increases, and the internal quantum efficiency can ultimately be improved.

As shown in Fig. 5, the comparative example is a case in which no dopant is included in the second barrier layer 22_2, and the embodiment shows a case where a high concentration dopant is contained in the second barrier layer 22_2.

In both the comparative example and the example, the internal quantum efficiency increases as the current density increases, and the internal quantum efficiency saturates from a certain point of time.

However, it can be seen that the internal quantum efficiency for all current densities is higher in the embodiment than in the comparative example.

Therefore, in the embodiment, the internal quantum efficiency can be improved by doping the second barrier layer 22_2 adjacent to the first well layer 24_1 of the active layer 20 with a high concentration dopant.

For example, the dose amount of the dopant included in the second barrier layer 22_2 may have a range from 9E17 to 3E18 to form the tunnel region A having the width w through which electrons can pass.

When the dose amount of the dopant of the second barrier layer 22_2 is 9E17 or less, the width w of the electrons can be larger than the width w, and electrons can not pass through.

When the dose amount of the dopant of the second barrier layer 22_2 is 3E18 or more, the crystallinity of the film quality of the second barrier layer 22_2 itself may be broken.

In the light emitting device according to the second and third embodiments, the remaining barrier layers except for the first barrier layer 22_1 of the active layer 20, that is, the second barrier layer to the nth barrier layer 22_2 to 22_n, All may include a dopant.

The second and third embodiments are almost similar to those of the first embodiment except for the division according to the barrier layer including the dopant.

Therefore, in the description of the second and second embodiments, the light emitting element 10 of Fig. 1 can be applied as it is.

6 is a diagram showing an energy band diagram of a light emitting device according to the second embodiment.

Referring to FIG. 6, all the second to n-th barrier layers 22_2 to 22_n in the light emitting device according to the second embodiment include high-concentration dopants. However, the first barrier layer 22_1 in contact with the second conductivity type semiconductor layer 18 or the barrier layer 17 does not include any dopant. This is because when the first barrier layer 22_1 contains a high concentration dopant, the tunnel region A is formed in the first barrier so that electrons in the first well layer 24_1 pass through the first barrier layer 22_1 Layer 17 or the second conductivity type semiconductor layer 18, the first barrier layer 22_1 can not perform its function.

The dopant may include an n-type dopant or a p-type dopant. The n-type dopant may include n-type dopants such as Si, Ge, and Sn. The p-type dopant may include Mg, Zn, Ca, Sr, Ba, and the like.

Each of the second barrier layer to the n-th barrier layer 22_2 to 22_n may include dopants of the same kind or may include dopants of different kinds.

For example, both the second barrier layer to the n-th barrier layer 22_2 to 22_n may include Si of the same kind, but the present invention is not limited thereto.

For example, the second barrier layer 22_2, the fourth barrier layer 22_4, ..., the (n-2) th barrier layer 22_ (n-2) and the nth barrier layer 22_n include Si And the third barrier layer 22_3, ..., (n-1) barrier layer 22_ (n-1) may include Ge, but the present invention is not limited thereto.

Each of the second to n-th barrier layers 22_2 to 22_n may include the same conductive dopant, or may include different kinds of dopants.

 For example, both of the second to n-th barrier layers 22_2 to 22_n may include Si having the same conductivity type, but the present invention is not limited thereto.

For example, the second barrier layer 22_2, the fourth barrier layer 22_4, ..., the (n-2) th barrier layer 22_ (n-2) , And the (n-1) th barrier layer 22_ (n-1) may include p-type Mg, but the present invention is not limited thereto.

The doses of the dopants of the second to n-th barrier layers 22_2 to 22_n are different from each other.

The dose amount of the dopant in the second barrier layer to the n-th barrier layer 22_2 to 22_n along the direction of the first conductivity type semiconductor layer 16 from the second conductivity type semiconductor layer 18 may be reduced have.

The third barrier layer 22_3 comprises a lesser dose amount of the dopant than the second barrier layer 22_2 and the fourth barrier layer 22_4 comprises less dopant than the third barrier layer 22_3 Dopants. Accordingly, the n-th barrier layer 22_n, which is the last barrier layer and is adjacent to the first conductivity type semiconductor layer 16, contains the least amount of dopant, whereas the second barrier layer 22_2 has the largest dose Amount of dopant.

The second barrier layer 22_2 including the dopant with the greatest dose amount is formed in a very narrow tunnel region A so that electrons can pass through the tunnel region A very easily.

On the other hand, the n-th barrier layer 22_n including the dopant of the smallest dose has a relatively wide tunnel region A, and the dose of electrons passing through the tunnel region A is relatively small.

Therefore, the amount of passage of the electrons of the respective barrier layers 22_2 to 22_n in the tunnel region A along the direction of the second conductivity type semiconductor layer 18 from the first conductivity type semiconductor layer 16 can be increased have. This means that electrons can more easily pass through the respective barrier layers 22_2 to 22_n along the direction of the second conductivity type semiconductor layer 18 from the first conductivity type semiconductor layer 16.

As described above, since the first well layer 24_1 adjacent to the second conductivity type semiconductor layer 18 has the highest internal light emitting efficiency, electrons of the active layer 20 are injected into the first conductivity type semiconductor layer 16, The second conductivity type semiconductor layer 18 is formed in the first conductivity type semiconductor layer 16 in the direction of the first conductivity type semiconductor layer 16 so that the first conductivity type semiconductor layer 16 is moved to the first well layer 24_1 rather than the n- And the dose amount of the dopant in the second to n-th barrier layers 22_2 to 22_n is reduced.

7 is a diagram showing an energy diagram of the light emitting device according to the third embodiment.

The third embodiment is substantially similar to the second embodiment except that the same dose amount of dopant is included in each of the remaining barrier layers 22_2 to 22_n except for the first barrier layer 22_1 which does not include any dopant .

Therefore, the description of the same components as those of the second embodiment in the third embodiment is omitted, and the explanation omitted in the third embodiment can be easily understood from the description of the second embodiment.

As shown in Fig. 7, the first barrier layer 22_1 does not include any dopant.

The second to n-th barrier layers 22_2 to 22_n may all contain dopants of the same dose amount.

As another example, the second barrier layer 22_2 may include a high concentration dopant, and the third through n-th barrier layers 22_3 through 22_n may have a dose amount less than the dopant included in the second barrier layer 22_2 Dopants may be equally included.

(N-2) barrier layer 22_ (n-2) and the second barrier layer 22_2, the fourth barrier layer 22_4, ..., and The n-th barrier layer 22_n and the odd-numbered barrier layers such as the third barrier layer 22_3, ..., the (n-1) -th barrier layer 22_ Of a dopant. In other words, the second barrier layer 22_2, the fourth barrier layer 22_4, ..., the (n-2) th barrier layer 22_ (n-2) and the nth barrier layer 22_n are the same (N-1) -th barrier layer 22_ (n-1) includes a dopant of the same dose amount, and the second barrier layer 22_ Each of the second barrier layer 22_2, the fourth barrier layer 22_4, ..., the (n-2) -th barrier layer 22_4 and the n-th barrier layer 22_n includes the third barrier layer 22_3, (N-1) barrier layer 22_ (n-1), respectively.

10: Light emitting element
12: substrate
14: buffer layer
15: Light emitting structure
16: First conductive type semiconductor layer
17:
18: second conductive type semiconductor layer
20:
22_1, 22_2, ..., 22_ (n-1), 22_n: barrier layer
24_1, 24_2, ..., 24_ (n-2), 24_n:

Claims (17)

A first conductive semiconductor layer;
An active layer including a plurality of barrier layers and a plurality of well layers alternately formed on the first conductivity type semiconductor layer; And
And a second conductivity type semiconductor layer formed on the active layer,
Wherein,
A first barrier layer disposed in contact with the second conductive semiconductor layer;
A second barrier layer disposed below the first barrier layer and closest to the first barrier layer;
And a first well layer disposed between the first barrier layer and the second barrier layer,
And the second barrier layer is doped only among the plurality of barrier layers formed in the active layer. The method according to claim 1,
The first well layer and the second barrier layer are in contact with each other,
Wherein the second barrier layer comprises a tunnel region for passing carriers therethrough. 3. The method of claim 2,
Wherein the energy band of the second barrier layer has a peak point adjacent to the first well layer,
Wherein the tunnel region is bent into a concave curve from a peak point adjacent to the first well layer. The method of claim 3,
Wherein the dopant doped in the second barrier layer is one of a p-type dopant and an n-type dopant. 5. The method of claim 4,
And the dose amount of the dopant doped in the second barrier layer is in the range of 9E17 to 3E18. delete delete delete delete delete delete delete delete delete delete delete delete

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