KR101056754B1 - Group III nitride semiconductor light emitting device - Google Patents

Abstract

The present disclosure is a substrate; An active layer formed on the substrate and generating light by recombination of electrons and holes; And first and second conductivity type semiconductor layers positioned on both sides of the active layer in the transverse direction and supplying electrons and holes to the side surfaces of the active layer.

Semiconductor, Light Emitting Device, Transverse Junction, Gate Electrode, Metal Layer

Description

Group III nitride semiconductor light emitting device {III NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE}

The present disclosure relates to a group III nitride semiconductor light emitting device as a whole, and more particularly, to a group III nitride semiconductor light emitting device capable of reducing attenuation of quantum efficiency by non-radiative recombination and an internal electric field. will be.

Here, the group III nitride semiconductor light emitting device has a compound semiconductor layer of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). Means a light emitting device, such as a light emitting diode comprising a, 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 of these materials.

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

1 is a view illustrating an example of a conventional Group III nitride semiconductor light emitting device, wherein the Group III nitride semiconductor light emitting device is grown on the substrate 100, the buffer layer 200 grown on the substrate 100, and the buffer layer 200. n-type group III nitride semiconductor layer 300, an active layer 400 grown on the n-type group III nitride semiconductor layer 300, p-type group III nitride semiconductor layer 500, p-type 3 grown on the active layer 400 The p-side electrode 600 formed on the group nitride semiconductor layer 500, the p-side bonding pad 700 formed on the p-side electrode 600, the p-type group III nitride semiconductor layer 500 and the active layer 400 are formed. The n-side electrode 800 and the passivation layer 900 are formed on the n-type group III nitride semiconductor layer 300 exposed by mesa etching.

As the substrate 100, a GaN-based substrate is used as a homogeneous substrate, and a sapphire substrate, a SiC substrate, or a Si substrate is used as a heterogeneous substrate, but in general, a sapphire substrate which is stable at high temperature and easily grows a relatively thin group III nitride thin film is used. It is used.

The active layer 400 is a layer that generates photons (light) through recombination of electrons and holes, and is mainly composed of In (x) Ga (1-x) N (0 <x≤1), and one quantum well layer (single quantum wells) or multiple quantum wells.

In the conventional Group III nitride semiconductor light emitting device, when electrons and holes move in the thickness direction of the active layer 400 formed of a plurality of material layers, non-radiative recombination that generates heat instead of light by recombination of electrons and holes ( As the frequency of non-radiative recombination increases, the quantum efficiency is deteriorated.

In addition, the conventional group III nitride semiconductor light emitting device has a problem in that the movement of electrons and holes is restricted by the internal electric field formed by piezoelectric phenomenon and spotaneous polarization, thereby deteriorating quantum efficiency.

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, a substrate; An active layer formed on the substrate and generating light by recombination of electrons and holes; And first and second conductivity type semiconductor layers positioned on both sides of the active layer in the transverse direction and supplying electrons and holes to the side surfaces of the active layer.

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

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

2 illustrates an example of a group III nitride semiconductor light emitting device according to the present disclosure, and includes a substrate 11, an active layer 12, and first and second conductive semiconductor layers 14 and 16.

As the substrate 11, a GaN-based substrate may be used as a homogeneous substrate, and a sapphire substrate, a SiC substrate, or a Si substrate may be used as a heterogeneous substrate. Sapphire substrates are preferred.

The active layer 12 is stacked on the substrate 11 in the vertical direction, and barrier layers 12a and 12c are disposed on upper and lower surfaces of the quantum well layer 12b and the quantum well layer 12b, respectively, in which electrons and holes are recombined. It can be formed as.

Here, when the substrate 11 is formed of a sapphire substrate, crystal defects may occur in the active layer 12 due to a lattice constant mismatch between the substrate 11 and the active layer 12, and in order to reduce this, the substrate 11 may be reduced. ) And the undoped GaN layer 13 may be formed between the active layer 12 and the active layer 12. In addition, a buffer layer may be further formed between the undoped GaN layer 13 and the substrate 11.

The quantum well layer 12b may be formed of In (x) Ga (1-x) N (0 <x ≦ 1), and the active layer 12 may have a plurality of quantum well layers as well as a single quantum well layer. It may be composed of four quantum wells. In the latter case, barrier layers 12a and 12c may be located between the respective quantum well layers, respectively.

The first conductive semiconductor layer 14 and the second conductive semiconductor layer 16 are located on both sides of the active layer 12 in the transverse direction. In particular, it is preferable that both lateral sides of the quantum well layer 12b are formed to contact the first and second conductivity-type semiconductor layers 14 and 16, respectively.

As a result, electrons and holes are injected through the side surfaces of the active layer 12. That is, electrons and holes may be directly injected into the quantum well layer 12b.

Accordingly, the frequency of occurrence of non-radiative recombination, which may occur when electrons and holes are injected in the thickness direction of the active layer 12, may be reduced, thereby improving quantum efficiency.

Each of the first conductive semiconductor layer 14 and the second conductive semiconductor layer 16 is formed of a semiconductor doped with n-type impurities and p-type impurities in a group III nitride semiconductor.

Specifically, the group III nitride semiconductor may be formed of Al (x) In (y) Ga (1-xy) N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1), and n Si, Ge, Se, C, etc. may be used as the type impurity, and Mg, Zn, Be, etc. may be used as the p-type impurities.

In addition, upper surfaces of the first conductive semiconductor layer 14 and the second conductive semiconductor layer 16 are provided with a first electrode 14a and a second electrode 16a respectively connected to an external power source.

The group III nitride semiconductor light emitting device 10 according to the present disclosure may be formed by the following process.

That is, after the active layer 12 is stacked on the substrate 11, the n-type impurity is doped in a state in which the remaining regions other than the active layer region at the position where the first conductivity-type semiconductor layer 14 is formed are doped and the first conductive layer is doped. The semiconductor layer 14 may be formed, and the second conductivity-type semiconductor layer 16 may be formed on the same principle.

Alternatively, after the active layer 12 is laminated on the substrate 11, the active layer region at the position where the first conductive semiconductor layer 14 is formed is removed by an etching process, and the first conductive doped with n-type impurities. The semiconductor layer 14 may be formed, and the second conductive semiconductor layer 16 may be formed on the same principle.

3 is a view illustrating another example of the group III nitride semiconductor light emitting device according to the present disclosure. The group III nitride semiconductor light emitting device 20 according to the present example may include the substrate 11, the active layer 12, the first, In addition to the two conductive semiconductor layers 14 and 16, the gate electrode 23 and the insulating layer 25 are further included.

The gate electrode 23 is formed above the group III nitride semiconductor light emitting device 10, that is, on the active layer 12, and the insulating layer 25 is formed between the gate electrode 23 and the active layer 12.

Here, the gate electrode 23 and the insulating layer 25 is preferably formed of a light-transmissive metal material so that the light generated in the active layer 12 can be easily emitted.

As a result, an electric potential in the vertical direction can be formed in the active layer 12, and the internal electric field formed by the piezolectic phenomenon and the spontaneous polarization can be reduced by the formed electric potential.

4 is a diagram illustrating a change in an internal electric field by the gate electrode of FIG. 3, before (a) and after (b) the first conductive semiconductor layer 14 and the active layer are applied with power to the gate electrode 23. (12), the conduction band energy of the second conductivity-type semiconductor layer 16 is shown.

In (a), it can be seen that an internal electric field is formed in the region A of the active layer 12 by piezolectic phenomenon and spotaneous polarization, but in case of (b), in the region A of the active layer 12 It can be seen that the internal field formed is significantly reduced.

FIG. 5 is a view showing another example of the group III nitride semiconductor light emitting device according to the present disclosure. The group III nitride semiconductor light emitting device 30 according to the present example may include the substrate 11 and the active layer described with reference to FIG. 2. In addition to (12) and the first and second conductivity-type semiconductor layers 14 and 16, a metal layer 34 is further included.

The metal layer 34 is formed in at least two grooves 32g formed on the top surface of the active layer 12 so as to be spaced apart from each other.

Here, the groove 32g may be formed in a lattice shape, a stripe shape, or the like when looking at the top surface of the active layer 12.

In addition, the distance ratio between the thickness of the groove 32g and the groove 32g adjacent to each other is preferably 1: 1 to 10, and the thickness of the groove 32g is preferably 1nm to 10nm.

In addition, the groove 32g is preferably formed to a depth adjacent to the quantum well layer 12b. This is because when the groove 32g is formed in the quantum well layer 12b, a problem may be prevented that the electrons and holes move.

As a result, Surface Plasmon Resonance (SPR) is generated in each of the metal layers 34 by the light generated from the active layer 12, and the two adjacent Plasmon Resonances (SPR) are adjacent to each other. An optical electric field is strongly formed in the active layer 12 located between the metal layers 34. As a result, the optical confinement factor is improved and the quantum efficiency can be improved.

Specifically, the quantum efficiency is proportional to the light amplification factor A, and the light amplification factor A of the group III nitride semiconductor light emitting device 10 having the length of the active layer 12 is A. ) Is defined as

Where Γ is the optical confinement factor and g is the optical gain.

On the other hand, the optical confinement factor (Γ) is defined as follows.

Where E is an optical electric field.

Looking at the two equations, as the optical electric field of the active layer 12 becomes larger than the surroundings, the optical confinement factor (Γ) increases, and the light amplification factor (A) is increased. Will become large.

The optical electric field of the active layer 12 is subjected to Surface Plasmon Resonance (SPR) where surface plasmon generated in the metal layer 34 is lifted by the light generated in the active layer 12. It can be formed strongly by.

That is, due to surface plasmon resonance (SPR), the metal layer 34 has a negative effective dielectric constant having a large absolute value, whereby the active layer 12 positioned between the two metal layers 34. ) A strong photoelectric field is formed.

Meanwhile, the metal layer 34 is formed of a metal capable of generating surface plasmon resonance. Specifically, metals having easy dielectric emission and negative dielectric constant such as Ag, Al, Au, etc. may be mainly used. . In addition, an alloy of Ag, Al, Au may also be used as the metal layer 34.

The metal layer 34 may be formed by a patterning process, an etching process, and a deposition process.

The patterning process may be electron beam patterning useful for nanopatterning, the etching process may be wet etching or electron beam lithography, and the deposition process may be performed by electron beam evaporation.

Various embodiments of the present disclosure will be described below.

(One). The active layer is a group III nitride semiconductor light-emitting device comprising a quantum well layer, the electrons and holes are recombined, and a barrier layer located on the upper and lower surfaces of the quantum well layer, respectively.

Thereby, the problem of leakage of electrons and holes from the quantum well layer can be prevented by the barrier layer, so that the problem of quantum efficiency deteriorating can be eliminated.

(2). A group III nitride semiconductor light emitting device in which lateral wells of the quantum well layer are in contact with the first and second conductivity type semiconductor layers, respectively.

As a result, electrons and holes can be easily introduced into the quantum well layer from the first and second conductivity-type semiconductor layers.

(3). A group III nitride semiconductor light-emitting device further comprising a gate electrode formed on the active layer to form a potential in the vertical direction, and an insulating layer positioned between the gate electrode and the active layer.

Thereby, the internal electric field in the active layer which adversely affects the quantum efficiency by the potential formed by the gate electrode can be reduced.

(4). The gate electrode is a group III nitride semiconductor light emitting device formed of a light-transmissive metal material.

As a result, since light generated in the active layer can be emitted through the gate electrode, a decrease in quantum efficiency due to the gate electrode can be prevented.

(5). At least two grooves formed spaced apart from each other on an upper surface of the active layer; And a metal layer formed in the groove.

Thereby, the light confinement factor of the active layer located between two adjacent metal layers can be improved, and quantum efficiency can be improved.

(6). A group III nitride semiconductor light emitting device, wherein the metal layer is formed of at least one material selected from Ag, Al, Au, and alloys thereof.

Thereby, the surface plasmon can be excited more easily in the metal layer.

According to one group III nitride semiconductor light emitting device according to the present disclosure, since electrons and holes are injected in a direction parallel to the active layer, the frequency of occurrence of non-radiative recombination may be reduced, thereby improving quantum efficiency. .

In addition, according to another group III nitride semiconductor light emitting device according to the present disclosure, the quantum efficiency can be improved because the internal electric field due to the piezoelectric phenomenon and the spontaneous polarization can be controlled by the gate electrode.

In addition, according to another group III nitride semiconductor light emitting device according to the present disclosure, quantum efficiency may be improved by surface plasmon resonance formed in the metal layer.

1 is a view showing an example of a conventional group III nitride semiconductor light emitting device,

2 is a view showing an example of a group III nitride semiconductor light emitting device according to the present disclosure;

3 is a view showing another example of the group III nitride semiconductor light emitting device according to the present disclosure;

4 is a view showing a change in an internal electric field by the gate electrode of FIG.

5 is a view showing another example of a group III nitride semiconductor light emitting device according to the present disclosure.

Claims (8)

Board; An active layer formed on the substrate and generating light by recombination of electrons and holes; And First and second conductivity type semiconductor layers positioned on both sides of the active layer and supplying electrons and holes to the side surfaces of the active layer; A gate electrode formed on the active layer to form a potential in the vertical direction; And A group III nitride semiconductor light emitting device comprising: an insulating layer positioned between the gate electrode and the active layer. The method according to claim 1, wherein the active layer, A quantum well layer in which electrons and holes are recombined; And A group III nitride semiconductor light emitting device comprising a; barrier layers positioned on the upper and lower surfaces of the quantum well layer, respectively. The group III nitride semiconductor light emitting device according to claim 2, wherein both sides of the quantum well layer are in contact with the first and second conductivity type semiconductor layers, respectively. The method according to claim 1, At least two grooves formed spaced apart from each other on an upper surface of the active layer; And It further comprises a metal layer formed in the groove, The group III nitride semiconductor light emitting device according to claim 1, wherein the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer are sequentially disposed in the transverse direction on the sapphire substrate. The method according to claim 1, A group III nitride semiconductor light emitting device, characterized in that the gate electrode is formed of a translucent metal material. Board; An active layer formed on the substrate and generating light by recombination of electrons and holes; And First and second conductivity type semiconductor layers positioned on both sides of the active layer and supplying electrons and holes to the side surfaces of the active layer; At least two grooves formed spaced apart from each other on an upper surface of the active layer; And A group III nitride semiconductor light emitting device further comprising a metal layer formed in the groove. The method according to claim 6, Group 3 nitride semiconductor light emitting device, characterized in that the metal layer is formed of at least one material selected from Ag, Al, Au and alloys thereof. The method according to claim 6, A gate electrode formed of a light-transmissive metal material on the active layer to form a potential in the vertical direction; And And an insulating layer disposed between the gate electrode and the active layer. The first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer are sequentially positioned laterally on the sapphire substrate. A group III nitride semiconductor light emitting device, characterized in that the metal layer is formed of at least one material selected from Al, Au, Ag, and alloys thereof.

Images