KR20120008809A - Compound semiconductor light emitting device - Google Patents

Abstract

PURPOSE: A compound semiconductor light emitting device is provided to improve the output of the compound semiconductor light emitting device by improving an injection effect of holes and a restriction effect of electrons. CONSTITUTION: An active layer generates light by recombining electrons and holes. A first compound semiconductor layer has a first conductivity and is located on one side of the active layer. Electrons are injected into the first compound semiconductor layer. A second compound semiconductor layer(50) has a second conductivity and is located on the other side of the active layer. Holes are injected into the second compound semiconductor layer. An electron blocking layer(42) is located between the active layer and the second compound semiconductor layer and has a type-II band alignment.

Description

 Compound Semiconductor Light Emitting Device {COMPOUND SEMICONDUCTOR LIGHT EMITTING DEVICE}

The present disclosure relates to a compound semiconductor light emitting device as a whole, and more particularly, to a compound semiconductor light emitting device having an improved output by improving the restraining effect of electrons and a hole injection effect.

The light emitting device includes a light emitting device including a compound semiconductor layer of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). It means a group III nitride light emitting device such as a diode, and does not exclude the inclusion of a material consisting of elements of other groups such as SiC, SiN, SiCN, CN or a semiconductor layer made of these materials.

This section provides background information related to the present disclosure which is not necessarily prior art.

In general, internal quantum efficiency (IQE) of semiconductor light emitting devices is degraded due to piezoelectric field and spontaneous polarization due to stress applied to the active layer, and these problems are group 3 constituting blue and green light emitting devices. More prominent in nitride semiconductors [Park et al., Appl. Phys. Lett. 75, 1354 (1999).

In order to minimize piezo electric field and spontaneous polarization in group III nitride semiconductor, the following method has been proposed.

1) Method to minimize spontaneous polarization and piezo effect using non-polar or semi-polar substrate [Park et al., Phys Rev B 59, 4725 (1999) and Waltereit et al., Nature 406, 865 (2000) ].

2) The cladding layer is a four-layered film, and the composition ratio of Al is increased to increase the binding effect of the transmitter to increase the luminous efficiency [Zhang et al., Appl. Phys. Lett. 77, 2668 (2000), Lai et al., IEEE Photonics Technol Lett. 13, 559 (2001).

However, in the case of 1), it is known that the device characteristics do not come out as theoretically expected due to the fact that there are many defects in the fabrication of the device due to the maturation of the growth technology for the dissimilar crystal growth direction, and the manufacturing process is very difficult [ K. Nishizuka et al., Appl. Phys. Lett. 87, 231901 (2005)].

In case of 2), it is not a fundamental solution because spontaneous polarization and piezo electric field cannot be eliminated fundamentally.

However, there is a theoretical study that the composition ratio of quaternary membranes in which the internal electric field due to piezoelectric and spontaneous polarization is extinguished can be found if the indium composition ratio in the quantum wells is determined in the InGaN / InGaAlN quantum well structure having the quaternary cladding layer. S. H Park, D. Ahn, J. W. Kim, Applied Physics Letters 92, 171115 (2008).

However, this method has the disadvantage that the growth conditions of the four-layer cladding layer are extremely difficult.

Meanwhile, in addition to the aforementioned method for improving the internal quantum efficiency, an electron blocking layer (EBL) for increasing the confinement effect of electrons in a light emitting device based on group II-VI or group III-V nitride-based quantum wells It is often adopted.

However, the electron barrier layer increases the restraining effect of electrons, and also acts as a potential barrier to holes and induces a downward band bending effect by an internal electric field. Therefore, the electron barrier layer has a problem of lowering the hole injection effect, making it difficult to improve the output [M. F. Schubert et al., Appl. Phys. Lett. 93, 041102 (2008).

This will be described later in the Specification for Implementation of the Invention.

SUMMARY OF THE INVENTION Herein, a general summary of the present disclosure is provided, which should not be construed as limiting the scope of the present disclosure. of its features).

According to one aspect of the present disclosure, an active layer that generates light by recombination of electrons and holes, and a first compound having a first conductivity and located on one side of the active layer and injecting electrons A second compound semiconductor layer having a second conductivity different from the first conductivity and positioned on the other side of the active layer and into which holes are injected, and between the active layer and the second compound semiconductor layer, and having a band of Type-II Provided is a compound semiconductor light-emitting device comprising an electron blocking layer having a band alignment.

This will be described later in the Specification for Implementation of the Invention.

1 is a view showing an example of a compound semiconductor light emitting device according to the present disclosure;
2 is a view showing an example of a quantum well structure of a compound semiconductor light emitting device according to the present disclosure;
3 is a view showing a state in which the quantum well structure shown in FIG. 2 is deformed by an internal electric field;
4 shows an example of a quantum well structure having a conventional electron barrier layer.

The present disclosure will now be described in detail with reference to the accompanying drawing (s).

The compound semiconductor light emitting device according to the present disclosure has the characteristics of improving the restraining effect of electrons and the hole injection effect to improve the output. To this end, an electron blocking layer (EBL) is interposed between the active layer and the second compound semiconductor layer. Since the electron barrier layer has a band alignment of Type-II, the electron barrier layer functions as an electron barrier layer and at the same time, lowers the potential barrier and the internal electric field effect on the holes, thereby improving the hole injection effect.

1 is a view showing an example of a compound semiconductor light emitting device according to the present disclosure.

Referring to FIG. 1, the compound semiconductor light emitting device may include a substrate 10, a buffer layer 20, a first compound semiconductor layer 30, an active layer 40, an electron barrier layer 42, and a second compound semiconductor layer 50. And a current spreading electrode 60, a first electrode 80, and a second electrode 70.

The buffer layer 20, the first compound semiconductor layer 30, the active layer 40, the electron barrier layer 42, and the second compound semiconductor layer 50 which serve as seeds of growth on the substrate 10 such as sapphire or SiC. This is formed in turn. If necessary, each layer may again include detailed layers. A first electrode 80 is formed on the etched first compound semiconductor layer 30, and a current spreading electrode 60 and a second electrode 70 are formed on the second compound semiconductor layer 50, and above them. A protective film (not shown) may be formed. When current is applied to the first electrode 80 and the second electrode 70, light is emitted from the active layer 40.

When an SiC substrate is used, the first electrode 80 may be formed under the substrate 10. The substrate 10 may be removed after growth of the first compound semiconductor layer 30, the active layer 40, and the second compound semiconductor layer 50 is completed. Growth of the first compound semiconductor layer 30, the active layer 40, the electron barrier layer 42, and the second compound semiconductor layer 50 is mainly performed by MOCVD (organic metal vapor growth method). The barrier layers 43 and 45 and the quantum well layer 41 are alternately formed on the first compound semiconductor layer 30 to form the active layer 40.

The first compound semiconductor layer 30, the quantum well layer 41, the barrier layers 43 and 45, and the second compound semiconductor layer 50 are formed of Al (p) Ga (q) In (1-pq) N (0). ≤ p ≤ 1, 0 ≤ q ≤ 1, 0 ≤ p + q ≤ 1).

The first compound semiconductor layer 30 and the second compound semiconductor layer 50 have different conductivity. For example, the first compound semiconductor layer 30 may be an n-type compound semiconductor layer 30, such as an n-type GaN layer, and the second compound semiconductor layer 50 may be a p-type compound semiconductor layer 50, such as a p-type GaN layer. Can be. Hereinafter, the first compound semiconductor layer 30 is used as the n-type compound semiconductor layer 30 and the second compound semiconductor layer 50 is used as the p-type compound semiconductor layer 50 and will be described with the same reference numerals.

The active layer 40 may be provided as a structure including one quantum well layer 41 (single quantum well structure) or a structure including a plurality of quantum well layers 41 (multi quantum well structure). For example, the quantum well layer 41 may be formed of InGaN, and the barrier layers 43 and 45 may be formed of at least one of GaN, InGaN, AlInGaN, and AlGaN.

2 is a diagram illustrating an example of a quantum well structure of the compound semiconductor light emitting device according to the present disclosure. 3 is a diagram illustrating a state in which the quantum well structure illustrated in FIG. 2 is deformed by an internal electric field.

2 and 3 illustrate an example of energy distribution of a conduction band (Ec) and a valence band (Ev) of the active layer 40, the electron barrier layer 42, and the second compound semiconductor layer 50. Shows. The electron barrier layer 42 is positioned between the active layer 40 and the p-type compound semiconductor layer 50. The electron barrier layer 42 may contact the barrier layer 43 of the active layer 40 or may contact the quantum well layer 41 of the active layer 40. 2 illustrates a quantum well structure in which the electron barrier layer 42 contacts the barrier layer 43 of the active layer 40.

The electron barrier layer 42 has a band alignment of Type-II. The term 'band-alignment of Type-II' refers to a band arrangement in which the energy of the conduction band Ev has a larger structure than the surroundings when the energy of the conduction band Ec is larger than the surroundings.

This is distinguished from 'band alignment of Type-I' which means that the energy of the valence band Ev is smaller than that of the surroundings when the energy of the conduction band Ec is larger than the surroundings. .

4 is a diagram illustrating an example of a quantum well structure having a conventional electron barrier layer. Unlike the quantum well structure according to the present disclosure, in the quantum well structure illustrated in FIG. 4, the electron barrier layer 142 has a band arrangement of Type-I.

2 and 3, the energy level of the conduction band Ec is higher than that of the conduction band Ec of the p-type compound semiconductor layer 50. The energy level is higher than the energy level of the valence band Ev of the p-type compound semiconductor layer 50. In addition, the energy level of the conduction band Ec of the electron barrier layer 42 is higher than the energy level of the conduction band Ec of the barrier layer 43 in contact with the electron barrier layer 42, and the energy level of the valence band Ev is higher. It is higher than the energy level of the valence band Ev of the barrier layer 43.

As such, the electron barrier layer 42 includes a special material to have a band arrangement of Type-II. The electron barrier layer 42 may be formed of a compound semiconductor containing antimony (Sb). For example, the electron barrier layer 42 is made of Al (x) Ga (y) In (1-xyz) NSb (z). (Where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 <z ≦ 1 0 <x + y + z ≦ 1).

When the composition ratio x of Al in the electron barrier layer 42 is increased, the effect of restraining electrons is increased, but the potential barrier to holes may be increased, and crystallinity may be lowered. If the composition ratio z of Sb is increased, the potential barrier for the hole is lowered, but the restraining effect of electrons may be lowered, and strain may be greatly increased. Therefore, by adjusting the ratio of the composition ratio x and z can be improved both the restraining effect of the electrons and the hole injection effect.

Electrons are injected into the n-type compound semiconductor layer 30 and diffused toward the p-type compound semiconductor layer 50. In order to increase the light emitted by the recombination of electrons and holes, the electrons must be confined to the quantum well layer 41 of the active layer 40, and the barrier layers 43 and 45 of the active layer 40 confine the electrons. The electron barrier layer 42 is interposed between the active layer 40 and the p-type compound semiconductor layer 50 to increase the electron confinement effect.

The electron barrier layer 42 according to the present disclosure described in FIGS. 2 and 3 and the conventional electron barrier layer 142 described in FIG. 4 have energy levels of the conduction band Ec as the barrier layer and the p-type compound semiconductor layer. Higher than 50 to increase the effect of restraining electrons.

The holes are injected into the p-type compound semiconductor layer 50 and diffused toward the n-type compound semiconductor layer 30. Since holes are significantly less mobile than electrons, improving the diffusion effect of holes is crucially important in improving the light generation efficiency by recombination of electrons and holes in the active layer 40.

In the conventional electron barrier layer 142 shown in FIG. 4, the energy level of the valence band Ev is lower than that of the barrier layer 143 and the p-type compound semiconductor layer 150, so that the potential barrier is used to diffuse holes into the active layer. It acts as a potential barrier. Therefore, the conventional electron barrier layer 142 improves the restraining effect of electrons but causes an obstacle in improving the hole injection effect.

On the other hand, in the electron barrier layer 42 according to the present disclosure described with reference to FIGS. 2 and 3, the energy level of the valence band (Ev) is higher than that of the barrier layer and the p-type compound semiconductor layer 50, so that holes are transferred to the active layer 40. In diffusion, the potential barrier is significantly lowered. Therefore, the hole injection efficiency is greatly improved, and the output of the compound semiconductor light emitting device is improved.

This output improvement effect was found to vary depending on the composition of the electronic barrier layer 42 as a result of repeated numerical analysis. In particular, the electron barrier layer 42 is made of Al (x) Ga (y) In (1-xyz) NSb (z). In the case of a compound semiconductor defined by 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 <z ≤ 1 0 <x + y + z ≤ 1, the effect of improving the output greatly depends on the content of Al and Sb. There was a difference.

According to the present disclosure, the composition ratio of Al in the electron barrier layer 42 having the band arrangement of Type-II is preferably 0 ≦ x ≦ 0.3. In order for the conduction band Ec to have sufficient energy to function as the electron barrier layer 42, Al is preferably contained in the electron barrier layer 42. When the content x of Al is greater than 0.3, band formation of Type-II is achieved. Is difficult and close to the conventional electronic barrier layer 142.

On the other hand, according to the present disclosure, it is preferable that the composition ratio of Sb in the electron barrier layer 42 having the band arrangement of Type-II is 0.005 ≦ z ≦ 0.1. The electron barrier layer 42 may have a band arrangement of Type-II by containing antimony (Sb). If the z content of antimony is z <0.005, the energy of the valence band (Ev) is not sufficiently high than that of the surroundings. The effect of lowering the potential barrier is weak. Therefore, in order to lower the potential barrier and improve the hole injection efficiency, it is preferable that it is 0.005 ≦ z. In addition, when 0.1 <z, since strain increases significantly, it is preferable that z <= 0.1.

Based on the numerical range for the composition ratio of Al and Sb for the electron barrier layer 42, the quantitative value of the band gap is referred to [S. Sakai et al., Jpn. J. Appl. Phys. 32, 4413 (1993).

Various embodiments of the present disclosure will be described below.

(1) The electron barrier layer is made of a compound semiconductor containing antimony (Sb), the energy level of the conduction band is higher than the energy level of the conduction band of the second compound semiconductor layer, and the valence band band) is higher than the energy level of the valence band of the second compound semiconductor layer.

(2) The electron barrier layer is made of Al (x) Ga (y) In (1-xyz) NSb (z) (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 <z ≦ 1 0 <x + y + A compound semiconductor light emitting device comprising: z≤1).

(3) A compound semiconductor light emitting device comprising 0.005 ≦ z ≦ 0.1.

(4) A compound semiconductor light emitting element, wherein 0 ≦ x ≦ 0.3.

(5) A compound semiconductor light emitting device, wherein the electron barrier layer is made of AlGaNSb.

(6) the active layer is a quantum well layer in which electrons and holes recombine; And

A compound semiconductor light-emitting device comprising a; barrier layers located on both sides of the quantum well layer.

 (7) The compound semiconductor light emitting device, wherein the electron barrier layer is located between the second compound semiconductor layer and the barrier layer, and is in contact with the second compound semiconductor layer and the barrier layer, respectively.

(8) The first compound semiconductor layer, the quantum well layer, the barrier layer, and the second compound semiconductor layer are made of Al (p) Ga (q) In (1-pq) N (0 ≦ p ≦ 1, 0 ≦ q ≦ 1, A compound semiconductor light emitting device comprising a compound semiconductor defined by 0 ≦ p + q ≦ 1).

(9) The electron barrier layer is made of Al (x) Ga (y) In (1-xyz) NSb (z) (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 <z ≦ 1 0 <x + y + A compound semiconductor light-emitting device, comprising z ≦ 1), wherein 0.005 ≦ z ≦ 0.1 and 0 ≦ x ≦ 0.3.

According to the compound semiconductor light emitting device according to the present disclosure, the electron blocking layer having the band arrangement of Type-II improves the restraining effect of electrons and the hole injection effect. Therefore, the output of the compound semiconductor light emitting device is improved.

30: n-type compound semiconductor layer 40: active layer
41: quantum well layer 43, 45: barrier layer
42: electron barrier layer 50: p-type compound semiconductor layer

Claims (10)

An active layer generating light by recombination of electrons and holes;
A first compound semiconductor layer having a first conductivity and positioned on one side of the active layer, into which electrons are injected;
A second compound semiconductor layer having a second conductivity different from the first conductivity and positioned on the other side of the active layer, wherein holes are injected; And
A compound semiconductor light emitting device, comprising: an electron blocking layer positioned between the active layer and the second compound semiconductor layer and having a band alignment of Type-II. The method according to claim 1,
The electron barrier layer is made of a compound semiconductor containing antimony (Sb), the energy level of the conduction band is higher than the energy level of the conduction band of the second compound semiconductor layer, and the value of the valence band A compound semiconductor light emitting element, wherein the energy level is higher than the energy level of the valence band of the second compound semiconductor layer. The method according to claim 2,
The electron barrier layer is made of Al (x) Ga (y) In (1-xyz) NSb (z) (Where 0≤x≤1, 0≤y≤1, and 0 <z≤1 0 <x + y + z≤1). The method according to claim 3,
Compound semiconductor light emitting device, characterized in that 0.005≤z≤0.1. The method according to claim 3,
A compound semiconductor light emitting device, characterized in that 0≤x≤0.3. The method according to claim 3,
Compound semiconductor light emitting device, characterized in that the electron barrier layer is made of AlGaNSb. The method according to claim 1,
Active layer
A quantum well layer in which electrons and holes recombine; And
A compound semiconductor light-emitting device comprising a; barrier layers located on both sides of the quantum well layer. The method according to claim 7,
The electron barrier layer is positioned between the second compound semiconductor layer and the barrier layer, the compound semiconductor light emitting device, characterized in that the contact with the second compound semiconductor layer and the barrier layer, respectively. The method according to claim 7,
The first compound semiconductor layer, the quantum well layer, the barrier layer, and the second compound semiconductor layer are Al (p) Ga (q) In (1-pq) N (0 ≦ p ≦ 1, 0 ≦ q ≦ 1, 0 ≦ p A compound semiconductor light emitting device comprising a compound semiconductor as defined by + q≤1). The method according to claim 9,
The electron barrier layer is made of Al (x) Ga (y) In (1-xyz) NSb (z) (Where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 <z ≦ 1 0 <x + y + z ≦ 1), and 0.005 ≦ z ≦ 0.1 and 0 ≦ x ≦ 0.3 Semiconductor light emitting device.

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