KR101903360B1 - Light Emitting Device - Google Patents

Abstract

According to an aspect of the present invention, there is provided a semiconductor light emitting device including: a first conductivity type semiconductor layer; a second conductivity type semiconductor layer disposed on the first conductivity type semiconductor layer; and a second conductivity type semiconductor layer disposed between the first and second conductivity type semiconductor layers, A diffusion barrier layer disposed between the second conductivity type semiconductor layer and the active layer and having a bandgap energy greater than that of the quantum well layer but smaller than that of the quantum well layer, the active layer including a quantum well layer and a quantum barrier layer, Emitting layer.

Description

Semiconductor light emitting device (Light Emitting Device)

The present invention relates to a semiconductor light emitting device.

2. Description of the Related Art A light emitting diode (LED), which is a kind of semiconductor light emitting device, is a semiconductor device capable of generating light of various colors due to recombination of electrons and holes at a junction portion of p and n type semiconductors when an electric current is applied. Such a semiconductor light emitting device has many advantages such as a long lifetime, a low power supply, and an excellent initial driving characteristic as compared with a light emitting device based on a filament, and the demand thereof is continuously increasing. Particularly, in recent years, a group III nitride semiconductor capable of emitting light in a short wavelength range of a blue series has been spotlighted.

In the case of such a light emitting diode, a structure in which an active layer is disposed between n-type and p-type semiconductor layers is generally used, and silicon (Si) as a Group 4 element is used to form the n-type semiconductor layer of the III- And a magnesium (Mg) atom which is a Group 2 element is used as a main dopant to form a p-type semiconductor layer. However, when magnesium is used as the dopant, due to the Mg-H complex formed by reacting with the hydrogen (H) atoms left after the reaction of ammonia (NH ₃ ) used as the source gas of the Group V element, There may be a problem in formation.

In order to solve such problems, various methods have been applied. Among them, a method of increasing the doping amount of magnesium to form the p-type semiconductor layer is typical. However, an increase in the amount of magnesium doping has a problem that magnesium in the process diffuses into the active layer and adversely affects the light emission in the active layer.

One of the objects of the present invention is to provide a semiconductor light emitting device having improved crystal quality.

Another object of the present invention is to provide a semiconductor light emitting device having improved light output.

According to an aspect of the present invention,

A second conductivity type semiconductor layer disposed on the first conductivity type semiconductor layer, at least a pair of quantum well layers and a quantum well layer disposed between the first and second conductivity type semiconductor layers, And a diffusion barrier layer disposed between the second conductive semiconductor layer and the active layer and having a bandgap energy greater than that of the quantum well layer but smaller than that of the quantum well layer, have.

In one embodiment of the present invention, the diffusion preventing layer may include In _x Ga _y N (0 <x? 1, 0? _Y <1, 0 <x + y?

In one embodiment of the present invention, the quantum well layer may have a composition formula of In _z Ga _w N (x <z? 1, 0? W <1, 0 <z + _w ?

In one embodiment of the present invention, the diffusion barrier layer may comprise an In _x Ga _y N (0.5 z & lt _{; x} &lt; z) layer.

In one embodiment of the present invention, the diffusion preventing layer may have a thickness of 1 nm to 5 nm.

In one embodiment of the present invention, the diffusion preventing layer has a structure in which a first layer having a larger band gap energy than the quantum well layer and a second layer having a band gap energy larger than that of the first layer are sequentially stacked .

In one embodiment of the present invention, the first layer may be InGaN and the second layer may be GaN.

In one embodiment of the present invention, the InGaN and GaN may be alternately repeatedly laminated two or more times.

In one embodiment of the present invention, the quantum well layer comprises InGaN, and the quantum barrier layer may comprise GaN.

In one embodiment of the present invention, the active layer is a multiple quantum well structure in which the quantum well layer and the quantum barrier layer are alternately repeatedly laminated two or more times, and the diffusion preventing layer is larger than the average band gap energy of the quantum well layer Band gap energy, but may have a thickness less than the average thickness of the quantum well layer.

In one embodiment of the present invention, the band gap energy may be increased as the diffusion preventing layer is closer to the second conductivity type semiconductor layer.

In one embodiment of the present invention, the diffusion barrier layer may include an InGaN layer having a smaller In composition ratio as the second conductivity type semiconductor layer is closer to the second conductivity type semiconductor layer.

In one embodiment of the present invention, the diffusion barrier layer may include a semiconductor layer having a band gap energy larger than the quantum well layer and smaller than the quantum well layer.

In addition, the solution of the above-mentioned problems does not list all the features of the present invention. The various features of the present invention and the advantages and effects thereof will be more fully understood by reference to the following specific embodiments.

According to an aspect of the present invention, it is possible to provide a semiconductor light emitting device having improved crystal quality.

According to another aspect of the present invention, a semiconductor light emitting device having improved light output can be provided.

The effects of the present invention are not limited to the effects described above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a schematic cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a part (A) of the active layer and the diffusion preventing layer of the semiconductor light emitting device shown in FIG.
FIG. 3 schematically shows conduction band energy levels in the vicinity of the active layer and the diffusion preventing layer of the semiconductor light emitting device shown in FIG.
4 is a schematic cross-sectional view of a semiconductor light emitting device according to another embodiment of the present invention.
FIG. 5 schematically shows conduction band energy levels in the vicinity of the active layer and the diffusion preventing layer of the semiconductor light emitting device shown in FIG.
6 is a graph showing SIMS measurement results of a semiconductor light emitting device according to an embodiment of the present invention and a semiconductor light emitting device according to a comparative example.
FIG. 7 is a graph showing light output measured by varying the magnesium doping concentration for the diffusion preventing layer having the same thickness.
FIG. 8 is a graph showing light output according to thickness when two layers are applied as a diffusion preventing layer.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. Therefore, the shapes and sizes of the elements in the drawings and the like can be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

FIG. 1 is a schematic cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a part (A) of an active layer and a diffusion preventing layer of the semiconductor light emitting device shown in FIG. FIG. 3 schematically shows conduction band energy levels in the vicinity of the active layer and the diffusion preventing layer of the semiconductor light emitting device shown in FIG.

1 to 3, a semiconductor light emitting device 100 according to the present embodiment includes a first conductivity type semiconductor layer 20, a second conductivity type semiconductor layer 20 disposed on the first conductivity type semiconductor layer 20, A semiconductor layer 30, an active layer 40 disposed between the first and second conductivity type semiconductor layers 20 and 30, a diffusion disposed between the active layer 40 and the second conductivity type semiconductor layer 30, Blocking layer 50 as shown in FIG.

The active layer 40 may include at least a pair of quantum well layers 41 and a quantum barrier layer 42 and the diffusion barrier layer 50 may have a band gap energy greater than that of the quantum well layer 41 And may have a thickness smaller than that of the quantum well layer (41).

The light emitting structure including the first conductivity type semiconductor layer 20, the active layer 40, the diffusion preventing layer 50 and the second conductivity type semiconductor layer 30 is formed on the substrate 10 sequentially And first and second electrodes 20a and 20b electrically connected to the first and second conductivity type semiconductor layers 20 and 30 are formed on the first and second conductivity type semiconductor layers 20 and 30, , 30a may be formed.

1, the first electrode 20a is formed by exposing a portion of the second conductive semiconductor layer 30, the active layer 40, and the first conductive semiconductor layer 20 to a first conductive type The second electrode 30a may be formed on the semiconductor layer 20 and the second electrode 30a may be formed on the second conductivity type semiconductor layer 30. [ In this case, a transparent electrode such as ITO, ZnO, or the like may be further provided to improve the ohmic contact function between the second conductivity type semiconductor layer 30 and the second electrode 30a.

The substrate 10 is provided as a substrate for semiconductor growth and may be made of an insulating, conductive, or semiconducting material such as sapphire, Si, SiC, MgAl ₂ O ₄ , MgO, LiAlO ₂ , LiGaO ₂ or GaN. In this case, it is most preferable to use sapphire having electrical insulation, sapphire having hexagonal-rhombo-symmetry (Hexa-Rhombo R3c) symmetry and having lattice constants of 13.001 Å and 4.758 Å in the c- And has a C (0001) plane, an A (1120) plane, an R (1102) plane, and the like. In this case, the C-plane is relatively easy to grow the nitride film, and is stable at high temperature, and thus is mainly used as a substrate for nitride growth.

On the other hand, as a material suitable for use as the substrate 10, an Si substrate can be exemplified, and the mass productivity can be improved by using a Si substrate which is more suitable for large diameter hardening and relatively low price. When a Si substrate is used, a nucleation layer made of a material such as Al _x Ga _{1 - x} N (0? X? 1) may be formed on the substrate 10, and then a nitride semiconductor having a desired structure may be grown thereon .

First and second conductive semiconductor layers 20, 30 is, for example, each of n-type and p-type semiconductor, and may be a layer, a nitride semiconductor, for example, Al _x In _y Ga _{1 -x- y} N (0≤x≤ 1, 0? Y? 1, 0? X + y? 1). Each layer may be composed of a single layer, but it may have a plurality of layers having different characteristics such as a doping concentration, a composition and the like. However, in addition to the nitride semiconductor, the first and second conductivity type semiconductor layers 20 and 30 may be made of AlInGaP or AlInGaAs semiconductor.

The active layer 40 disposed between the first and second conductivity type semiconductor layers 20 and 30 emits light having a predetermined energy by recombination of electrons and holes, and as shown in FIG. 3, Layer 41 and the quantum barrier layer 42 may be a single quantum well (SQW) or a multiple quantum well (MQW) structure alternately stacked. For example, in the case of a nitride semiconductor, the quantum well layer 41 may be made of InGaN (In, Ga content may be changed) and the quantum barrier layer 42 may be made of GaN, InGaN (In, Ga, The In content may be lower than the quantum well layer), AlInGaN (Al, In, Ga content may vary), and the like. The quantum barrier layer 42 may be thicker than the quantum well layer 41 although it may vary depending on the embodiment.

The first and second conductive semiconductor layers 20 and 30 and the active layer 40 and the diffusion preventing layer 50 and the like which will be described later are formed by metal organic chemical vapor deposition (MOCVD) , Hydride vapor phase epitaxy (&quot; HVPE &quot;), molecular beam epitaxy (MBE), and the like.

Although not shown in detail, a buffer layer is interposed between the first conductivity type semiconductor layer 20 and the substrate 10 to relax the stress acting on the first conductivity type semiconductor layer 20, thereby improving the crystallinity. An electron blocking layer (not shown) having a relatively high band gap energy is interposed between the diffusion preventing layer 50 and the second conductivity type semiconductor layer 30 so that electrons flow over the active layer 40, Can be prevented. The electron blocking layer may be made of AlGaN or the like, but is not limited thereto.

The diffusion preventing layer 50 is disposed between the active layer 40 and the second conductivity type semiconductor layer 30 and has a band gap energy larger than that of the quantum well layer 41 but smaller than the quantum well layer 41 It is possible to prevent diffusion and inflow of the impurity into the active layer 40 without distortion or deformation of the emission wavelength caused by the diffusion preventing layer 50. [

Specifically, the diffusion barrier layer 50 may include a dopant (for example, Mg) doped for doping the second conductivity type semiconductor layer 30 when the second conductivity type semiconductor layer 30 is grown on the active layer 40, , Zn, etc.) can be prevented from diffusing into the active layer 40. At this time, the diffusion preventing layer 50 is formed to have a smaller thickness than the quantum well layer 41, so that the diffusion preventing layer 50 hardly affects the emission wavelength determined by the band gap energy and the thickness of the quantum well layer 41 and the quantum barrier layer 42 And the polarization phenomenon due to the band gap difference between the quantum well layer 41 and the second conductivity type semiconductor layer 30 can be alleviated.

In one embodiment of the present invention, the diffusion barrier layer 50 may include In _x Ga _y N (0 <x? 1, 0? _Y <1, 0 <x + y? Since the indium (In) atom has a relatively large size as compared with gallium (Ga), it can effectively block the incorporation of the second conductivity type dopant, for example, magnesium (Mg) acting as an impurity in the active layer 40 .

When the quantum well layer 41 and the quantum barrier layer 42 are made of InGaN / GaN, the diffusion barrier layer 50 is lattice-matched to the InGaN quantum well layer 41, The defects can be minimized. Specifically, the quantum well layer 41 may have a composition formula of In _z Ga _w N (x <z? 1, 0? W <1, 0 <z + _w ? That is, the quantum well layer 41 may have an indium (In) composition ratio larger than that of the diffusion barrier layer 50, so that it is larger than the quantum well layer 41 and smaller than the quantum barrier layer 42 It is possible to provide a semiconductor light emitting device in which the emission quality is improved by having band gap energy.

In the present embodiment, when the active layer 40 has a multiple quantum well structure in which the quantum well layer 41 and the quantum barrier layer 42 are alternately repeatedly laminated two or more times, May have a bandgap energy that is larger than the average band gap energy of the well layer (41), but may have a thickness smaller than the average thickness of the quantum well layer (41).

In one embodiment, the diffusion barrier layer 50 may comprise a layer of In _x Ga _y N (0.5 z & lt _{; x} &lt; z). That is, the diffusion preventing layer 50 is formed to be larger than the indium (In) composition ratio z of the quantum well layer 41 but larger than 0.5 times (0.5 z) of the indium (In) composition ratio of the quantum well layer 41 Indium composition ratio. Diffusion preventing layer 50 acts as a quantum well layer 41 of the active layer 40 and participates in light emission when the indium composition ratio x of the diffusion preventing layer 50 is 0.5 times or more than that of the quantum well layer 41, The diffusion preventing layer 50 is formed to have a thickness smaller than that of the quantum well layer 41, so that the diffusion preventing layer 50 can be prevented from participating in the light emission. Specifically, the diffusion barrier layer 50 may have a thickness of about 1 nm to 5 nm.

4 schematically shows a cross section of a semiconductor light emitting device according to another embodiment of the present invention, and FIG. 5 schematically shows a conduction band energy level around the active layer and the diffusion preventing layer of the semiconductor light emitting device shown in FIG. 4 .

4 and 5, the semiconductor light emitting device 101 according to the present embodiment includes a first conductivity type semiconductor layer 20, a second conductivity type semiconductor layer 20 disposed on the first conductivity type semiconductor layer 20, A semiconductor layer 30, an active layer 40 disposed between the first and second conductivity type semiconductor layers 20 and 30, a diffusion disposed between the active layer 40 and the second conductivity type semiconductor layer 30, Blocking layer 150 as shown in FIG.

In the case of this embodiment, only the configuration of the diffusion preventing layer 150 is different from the embodiment shown in FIG. 1 to FIG. 3, and therefore, only the changed configuration will be described below.

The active layer 40 may include at least one pair of quantum well layers 41 and a quantum barrier layer 42 and the diffusion barrier layer 150 may have a band gap energy greater than that of the quantum well layer 41 And may have a thickness smaller than that of the quantum well layer (41).

In addition, in the case of this embodiment, the diffusion preventing layer 150 has a first layer 151 having a larger band gap energy than the quantum well layer 41 and a second layer 151 having a band gap energy larger than that of the first layer 151 And the second layer 152 may be sequentially stacked. Specifically, the first layer 151 may be made of InGaN, the second layer 152 may be made of GaN, and the first and second layers 151 and 152 may be alternately stacked two or more times .

In the present embodiment, since the diffusion barrier layer 150 is composed of two layers having different band gap energies, the stress due to the difference in lattice constant between the active layer 40 and the second conductivity type semiconductor layer 30 is alleviated Accordingly, it is possible to provide a semiconductor light emitting device having improved crystal quality and improved light emitting efficiency.

Although not shown in detail, the diffusion barrier layer 150 is made of InGaN, and a structure in which the composition ratio of indium (In) is gradually decreased in a layer closer to the second conductivity type semiconductor layer 30 Lt; / RTI &gt; Accordingly, the diffusion barrier layer 150 may have a tilted structure in which the bandgap energy increases as the second conductivity type semiconductor layer 30 becomes closer to the second conductivity type semiconductor layer 30. In this case, An effect similar to that of the embodiment shown in Fig. 5 can be obtained.

6 is a graph showing SIMS measurement results of a semiconductor light emitting device according to an embodiment of the present invention and a semiconductor light emitting device according to a comparative example.

Specifically, Mg (Mg) penetration profile into the active layer is shown when InGaN is applied between the active layer and the p-type GaN layer (Example) and when GaN is applied (Comparative Example).

Referring to FIG. 6, the distribution of indium ((1) In) in the active layer is similar to that of InGaN ((2) In) when GaN is used as the diffusion preventing layer. On the other hand, when GaN is applied as the diffusion preventing layer ((1) Mg), magnesium (Mg) applied as a dopant of p-type GaN exhibits a concentration of about 3 × 10 ¹⁸ / cm 3 at a depth of about 0.15 μm (Mg) concentration in the active layer, and a concentration of about 1.8 × 10 ¹⁷ / cm 3 at the same depth when InGaN is applied to the diffusion barrier layer (Mg). That is, when InGaN having a bandgap energy larger than the quantum well layer and smaller than the quantum well layer is used as the diffusion preventing layer, it can effectively prevent the influx and diffusion of the p-type impurity which functions as an impurity in the active layer, have.

FIG. 7 is a graph of light output measured by varying the doping concentration of magnesium (Mg) for the diffusion preventing layer having the same thickness.

Referring to FIG. 7, when the GaN is applied as the diffusion preventing layer and magnesium (Mg) is flowed as a dopant in the growth of the p-type semiconductor layer, the light output is about 144 mW. However, the InGaN is applied as the diffusion preventing layer It can be seen that when the same amount of magnesium (Mg) is flowed, the light output remarkably increases to about 148 mW. In addition, in order to confirm the change of the light output according to the amount of magnesium (Mg) injection, the amount of magnesium injected was increased to 700 cc and 900 cc, and it was confirmed that the light output decreased with an increase in the magnesium injection amount. In other words, according to FIG. 7, magnesium has an effect of lowering the light output of the light emitting device, and the InGaN diffusion preventing layer has an effect of preventing diffusion of magnesium and improving light output.

FIG. 8 is a graph showing light output according to thickness when two layers (InGaN / GaN) are applied as a diffusion preventing layer as in the embodiment shown in FIG.

Referring to FIG. 8, when the diffusion preventing layer is applied to a thickness of 16 nm, the light output is about 136 mW. After measuring the light output after reducing the thickness by 20% and 40%, the light output is about 138 mW, MW. &Lt; / RTI &gt; That is, the distance between the active layer and the p-type semiconductor layer is minimized by reducing the thickness of the diffusion prevention layer to a thickness of the quantum well layer or less, thereby increasing the electron-hole coupling efficiency and improving the light output.

The present invention is not limited to the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

100, 101: Semiconductor light emitting device 10: Substrate
20: first conductivity type semiconductor layer 30: second conductivity type semiconductor layer
40: active layer 41: quantum well layer
42: quantum barrier layer 50, 150: diffusion barrier layer
151: first layer 152: second layer
20a: first electrode 30a: second electrode

Claims (13)

A first conductive semiconductor layer;
A second conductive semiconductor layer disposed on the first conductive semiconductor layer;
An active layer disposed between the first and second conductive type semiconductor layers and including at least a pair of quantum well layers and a quantum barrier layer; And
A diffusion barrier layer disposed between the second conductivity type semiconductor layer and the active layer and having a band gap energy greater than that of the quantum well layer but smaller than the quantum well layer;
/ RTI &gt;
Wherein the diffusion barrier layer includes a semiconductor layer having a band gap energy larger than that of the quantum well layer and smaller than that of the quantum well layer.
The method according to claim 1,
Wherein the diffusion preventing layer comprises In _x Ga _y N (0 <x? 1, 0? _Y <1, 0 <x + y? 1) layer.
3. The method of claim 2,
Wherein the quantum well layer has a composition formula of In _z Ga _w N (x <z? 1, 0? W <1, 0 <z + _w ? 1).
The method of claim 3,
Wherein the diffusion preventing layer comprises In _x Ga _y N (0.5z _x &lt; z) layer.
The method according to claim 1,
Wherein the diffusion preventing layer has a structure in which a first layer having a larger band gap energy than the quantum well layer and a second layer having a band gap energy larger than that of the first layer are sequentially stacked.
6. The method of claim 5,
Wherein the first layer is InGaN and the second layer is GaN.
The method according to claim 6,
Wherein the InGaN and GaN are repeatedly laminated two or more times alternately.
The method according to claim 1,
Wherein the active layer is a multiple quantum well structure in which the quantum well layer and the quantum barrier layer are alternately repeatedly laminated two or more times,
Wherein the diffusion barrier layer has a band gap energy greater than an average band gap energy of the quantum well layer and a thickness smaller than an average thickness of the quantum well layer.
The method according to claim 1,
And the band gap energy increases as the diffusion preventing layer is closer to the second conductivity type semiconductor layer.
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