KR101784109B1 - Quantum well structure and blue light emitting diode including the same - Google Patents

Abstract

A barrier layer made of GaN, and a well layer formed on the GaN barrier layer and having the following Chemical Formula 1:
[Chemical Formula 1]
In _x B _y Ga _{1 -x- y} N
(Where 0.14? X? 0.2 and 0 < y? 0.02)

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantum well structure and a blue light emitting diode including the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a quantum well structure and a blue light emitting diode including the same, and more particularly, to a quantum well structure having a reduced internal electric field and improved light emitting efficiency in a blue spectral region and a blue light emitting diode .

Group III nitride semiconductors have been extensively studied because they can be applied to potential electronic and optoelectronic device applications such as light emitting diodes (LEDs) and laser diodes (LDs). In particular, ) To infrared (0.7 eV with respect to InN) is required in the field of optoelectronic devices.

However, the InGaN layer grown on the GaN substrate has a disadvantage of lattice mismatch with respect to the high In-content, resulting in a problem of increasing the misfit dislocation density.

Also, a large internal field induced by piezoelectric polarization and spontaneous polarization is present in the active region, thereby reducing the radiative recombination rate and causing significant electron leakage from the active region.

In order to solve this problem, various methods such as a non-square InGaN / GaN system have been proposed to reduce the internal field effect. For example, two-layer and three-layer staggered quantum well structures have been studied .

However, these structures are not effective in improving the light emission in the blue spectrum region, and therefore, the technical development is still required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a quantum well structure and a blue light emitting diode including the same that can reduce the internal electric field and improve the light emission efficiency of the blue spectral region.

Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

According to an embodiment of the present invention, there is provided a quantum well structure including a barrier layer made of GaN and a well layer stacked on the GaN barrier layer,

[Chemical Formula 1]

In _x B _y Ga _{1 -x- y} N

Here, 0.14? X? 0.2 and 0 < y?

In this case, 0.008? Y?

According to another embodiment of the present invention, there is provided a blue light emitting diode comprising a first doping layer, a second doping layer, and an active region interposed between the first doping layer and the second doping layer, The active region includes a barrier layer made of GaN and a well layer formed on the GaN barrier layer and having the following Chemical Formula 1:

[Chemical Formula 1]

In _x B _y Ga _{1 -x- y} N

(Where 0.14? X? 0.2 and 0 < y? 0.02)

In this case, 0.008? Y?

In addition, the active region may further include a GaN buffer layer.

The present invention has an advantage that boron (B, boron) is added to InGaN to reduce the internal electric field, optimize lattice parameters independently of each other, and provide a quantum well structure with reduced strain.

Further, by including the optimum boron content, there is an advantage that the maximum spontaneous emission peak can be exhibited in the blue spectrum.

)의 함수로서 도시하고, (b) 의사-페르미 준위 분리를 도시한 것이다. 1 is a cross-sectional view schematically showing a blue light emitting diode including a quantum well structure according to an embodiment of the present invention.
FIG. 2 is a _{graph showing the} relationship between the boron (B) composition of the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure with several indium (In) compositions, Lt; / RTI &gt;
FIG. 3 is a _{graph showing the} relationship between the boron (B) composition (a), the spontaneous emission spectrum and the internal electric field (b) for a quantum well structure of 440 nm, In _x B _y Ga _{1 -x- y} N / GaN having several indium Lt; / RTI &gt;
FIG. 4 is a _{graph showing the} relationship between x and y of the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure at a wavelength of 400 nm and (x, y) = (a) (0.192, 0) , 0.017), (c) (0.16, 0.014), and (d) (0.18, 0.008).
FIG. 5 shows the In _x B _y Ga _{1 -x- y} N / GaN quantum wells at (x, y) = (0.192,0), (0.14,0.017), (0.16,0.014) For the structure, (a) the optical matrix element is replaced with an infrain wave vector

) And (b) pseudo-Fermi level separation.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in this specification and claims should not be construed in a conventional or dictionary sense, and the inventor should properly define the concept of the term to best describe its invention The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, at the time of the present application, It should be understood that various equivalents and modifications are possible.

Hereinafter, the light emission characteristics of a quantum well structure will be described theoretically using multi-band effective-mass theory and non-Marcohoven model, and a free carrier motel by band gap re-standardization will be considered.

In addition, the solution of self-consistent (SC) is to solve the Schrodinger equation for electrons, to solve block-diagonalized 3 × 3 Hamiltonian for holes, to solve Poisson equation And the parameters for B _x In _y Ga _{1 -x- y} O are obtained from a linear combination between the parameters of BN, InN, GaN.

1 is a cross-sectional view schematically showing a blue light emitting diode including a quantum well structure according to an embodiment of the present invention.

Referring to FIG. 1, a blue light emitting diode 100 including a quantum well structure 130 according to an embodiment of the present invention includes a substrate 110, a first doping layer 120, an active region 140, 2 doping layer 130, and the active region may include a quantum well structure 141 and a buffer layer 142.

At this time, the substrate 110 is not limited to those used in the related art. For example, sapphire, spinel, silicon carbide substrate having a hexagonal system structure may be used.

The first doping layer 120 may be disposed on the substrate 110 and may be an n-type semiconductor layer or a p-type semiconductor layer. Preferably, the n-type semiconductor layer or the gallium nitride series A p-type semiconductor layer can be used. In addition, a buffer layer (not shown) may further be provided between the substrate 110 and the first doping layer 120 to improve the quality of the doping layer.

 An active region 140 including a quantum well structure 141 and a buffer layer 142 may be disposed on the first doping layer 120.

The quantum well structure 141 is formed by inserting a thin semiconductor layer having an energy bandgap smaller than the energy bandgap of the semiconductor layer between different semiconductor layers. The quantum well structure 141 is a structure in which electrons or holes are trapped in an energy barrier, .

The quantum well structure 141 according to an embodiment of the present invention may have a stacked structure of a well layer 141B and a barrier layer 141A. In this case, the well layer means a thin layer having a small energy band gap, and the barrier layer has a band gap larger than that of the well layer and surrounds the well layer, and serves to bind electrons and holes in the well layer into the well . When the quantum well structure has such a structure, electrons and holes in the active region recombine in the quantum well structure to emit light, so that the well layer determines the optical characteristics of the active region.

At this time, the barrier layer 141A of the quantum well structure 141 according to the preferred embodiment of the present invention may be formed to include GaN, and the well layer 141B may be formed to include the following Chemical Formula 1.

[Chemical Formula 1]

In _x B _y Ga _{1 -x- y} N

Herein, 0.14? X? 0.2 and 0 <y? 0.02, where x is a numerical value close to 440 nm in which the wavelength range is blue and the luminescence intensity of the indium (In) The range of y belonging to the increasing condition is 0 < y? 0.02.

The range of y may be 0.008? Y? 0.013, and as shown in Fig. 2 (a), the emission intensity can be optimum regardless of the indium component within this range.

Hereinafter, for convenience of description, a quantum well structure including a GaN barrier layer and a well layer according to an embodiment of the present invention will be abbreviated as In _x B _y Ga _{1 -x- y} N / GaN, Here, it is explained that 0.14? X? 0.2 and 0 <y? 0.02 are included.

FIG. 2 is a _{graph showing the} relationship between the boron (B) composition of the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure with several indium (In) compositions, Lt; / RTI &gt;

2 (a), in the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure in which the width is fixed to 2.5 nm, the transition wavelength (vertical axis) is changed according to the content of boron (B) . The transition wavelength changes abruptly with a longer wavelength, and the wavelength increases sharply due to the stark effect as B increases in the region where the B composition is larger than 0.07.

In particular, in order to provide a transition wavelength of 440 nm (blue wavelength), the In composition in the conventional InGaN / GaN quantum well structure was 0.192, but the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure (X, y) values are 0.14, 0.017, 0.16, 0.014, and 0.18, 0.008, respectively. As the value of B decreases, the value of indium in the well decreases and the strain value decreases. , Which shows the advantage of a quantum well structure with boron (B) added. If the strain is reduced, the crystal crack is reduced as much. For example, in the case of (x, y) = (0.18, 0.008), the strain was reduced from 2.01% to 1.72% as compared with the case of (x, y) = (0.192, 0.00).

FIG. 2 (b) is a graph showing the spontaneous emission peak of the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure fixed to a width of 2.5 nm. The spontaneous emission spectrum is N _2D = 10 × 10 ¹² cm &lt; ^{-2 &} gt ^{; at} the sheet carrier density.

Referring to FIG. 2 (b), the spontaneous emission peak rapidly increases as the composition of boron (B) increases, exhibits a maximum value in a predetermined critical boron (B) composition, and the critical boron (B) ), Regardless of the composition. In addition, the spontaneous emission peak began to decrease when the boron (B) composition exceeded the threshold value.

It was also observed that the light intensity of the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure in the critical boron (B) composition was increased to about twice that of the conventional InGaN / GaN quantum well structure light intensity.

Although not shown in the figure, the strain of the well for the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure is smaller than that of the conventional InGaN / GaN quantum well structure, and specifically, (x, y) = (0.192, 0.008), while the strain value for the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure is -1.72% ) For the InGaN / GaN quantum well structure was as high as -2.01%.

FIG. 3 is a _{graph showing the} relationship between the boron (B) composition (a), the spontaneous emission spectrum and the internal electric field (b) for a quantum well structure of 440 nm, In _x B _y Ga _{1 -x- y} N / GaN having several indium Lt; / RTI &gt;

The spontaneous emission spectrum of FIG. 3 was obtained at a sheet carrier density of N _2D = 10 × 10 ¹² cm ^-2 , and the results for a conventional InGaN / GaN quantum well structure with a transition wavelength of 440 nm for comparison are shown.

Referring to FIG. 3, it can be seen that the emission peak is improved when the spontaneous boron (B) composition is added as in the present invention. Specifically, the quantum well structure with x = 0.18 and y = 0.008 has a peak value twice as large as the peak value of the conventional InGaN / GaN quantum well structure. This is because the internal electric field (-0.40 MV / cm) of the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure becomes larger than the conventional InGaN / GaN quantum well structure internal electric field (-1.04 MV / cm). &Lt; / RTI &gt; Internal field reduction results from a rapid increase in spontaneous polarization in a well where the boron (B) composition increases. However, when the composition of boron (B) is further increased, the magnitude of the internal electric field increases rapidly as the boron (B) composition increases, and as a result, the spontaneous emission peak decreases as shown in Fig. 2 (b).

FIG. 4 is a _{graph showing the} relationship between x and y of the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure at a wavelength of 400 nm and (x, y) = (a) (0.192, 0) , 0.017), (c) (0.16, 0.014), and (d) (0.18, 0.008). At this time, a solution of self-consistent (SC) was obtained at a sheet carrier density of N _2D = 10 × 10 ¹² cm ^-2 .

Referring to FIG. 4, the potential profile of a conventional InGaN / GaN quantum well structure with (x, y) = (0.192, 0.0) is larger than the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure Lt; / RTI &gt; However, the internal electric field decreases as the boron (B) composition increases, and the potential profile exhibits a flat band shape in the critical boron composition, and this phenomenon occurs when (x, y) = (0.18, 0.008) In _x B _y Ga _{1 -x- y} N / GaN quantum well structures. Therefore, the spatial separation between electron and hole wave functions is greatly reduced due to the disappearance of the internal electric field. On the other hand, as shown in the In _x B _y Ga _1-xy N / GaN quantum well structure in which the internal electric field is (x, y) = (0.14, 0.017) and (0.16, 0.014) And when the boron content exceeds the critical boron composition, it begins to increase again.

)의 함수로서 도시하고, (b) 의사-페르미 준위 분리를 도시한 것이다. FIG. 5 shows the In _x B _y Ga _{1 -x- y} N / GaN quantum wells at (x, y) = (0.192,0), (0.14,0.017), (0.16,0.014) For the structure, (a) the optical matrix element is replaced with an infrain wave vector

) And (b) pseudo-Fermi level separation.

는, 의사-페르미 준위와 전도대의 접지 상태 에너지(가전자대) 간의 에너지 차로서 정의될 수 있다. 또한, 셀프 컨시스턴트 (self-consistent, SC)의 해(solution)는 N_2D = 10 × 10¹²cm^-2의 시트 캐리어 밀도에서 취득된 것이다. The pseudo-Fermi level separation is conveniently plotted as an x function, where pseudo-Fermi level separation

Can be defined as the energy difference between the pseudo-Fermi level and the ground state energy (valence band) of the conduction band. Also, a solution of self-consistent (SC) was obtained at a sheet carrier density of N _2D = 10 × 10 ¹² cm ^-2 .

와는 거의 독립적인 것으로 나타나 있다. 이는 붕소(B) 조성에 상관 없이

=0을 초과하는 높은 상태에서도 최상위 가전자 부대역의 HH 대역 특성이 변하지 않는 상태로 유지된다는 사실로 설명할 수 있다.The matrix element for the In _x B _y Ga _{1 -x- y} N / GaN quantum well structure according to an embodiment of the present invention is similar to the conventional InGaN / GaN quantum well structure,

Is almost independent from This means that regardless of the composition of boron (B)

Can be explained by the fact that the HH band characteristic of the highest valued electron subband remains unchanged even at a high state exceeding zero.

It has also been observed that the conventional InGaN / GaN quantum well structure at (x, y) = (0.192, 0) has maximum pseudo-Fermi level separation, The increase in the spontaneous emission peak observed in the case of (0.14, 0.017), (0.16, 0.014), (0.18, 0.008) is mainly due to the increase of the optical matrix element due to the decrease of the internal electric field.

Meanwhile, the second doping layer 130 may be disposed on the active region 140, and the second doping layer 120 may be either an n-type semiconductor layer or a p-type semiconductor layer, A gallium-based n-type semiconductor layer or a gallium nitride-based p-type semiconductor layer may be used, but it may be a semiconductor layer different from the first doping layer 120 applied together.

For example, the first doping layer 120 and the second doping layer 130 may be an n-type semiconductor layer-a p-type semiconductor layer or a p-type semiconductor layer-an n-type semiconductor layer, respectively.

In addition, a portion of the first doping layer 120 and the second doping layer 130 may be etched to remove the respective semiconductor layers, and the electrode pad 150 may be further formed on the exposed semiconductor layer can do.

In addition, according to another embodiment of the present invention, the active region 140 may further include a buffer layer 142, and the buffer layer 142 may include a GaN component.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be understood by 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.

100: blue light emitting diode
110: substrate
120: first doping layer
130: second doping layer
140: active area
141: Quantum well structure
141A: barrier layer
141B: well layer
142: buffer layer
150: Electrode pad

Claims (5)

A barrier layer made of GaN; And
A quantum well structure stacked on the GaN barrier layer and comprising a well layer having the following Formula 1:
[Chemical Formula 1]
In _x B _y Ga _{1 -x- y} N
(Where 0.14? X? 0.2 and 0 < y? 0.02) The method according to claim 1,
Wherein said quantum well structure is 0.008? Y? 0.013. A gallium nitride based n-type compound semiconductor layer;
A gallium nitride based p-type compound semiconductor layer; And
And an active region interposed between the n-type and p-type compound semiconductor layers, the blue light emitting diode comprising:
Wherein the active region comprises a barrier layer made of GaN and a well layer formed on the GaN barrier layer and having the following Chemical Formula 1. < EMI ID = 1.0 &gt;
[Chemical Formula 1]
In _x B _y Ga _{1 -x- y} N
(Where 0.14? X? 0.2 and 0 &lt; y? 0.02) The method of claim 3,
Wherein 0.008? Y? 0.013. The method of claim 3,
Wherein the active region further comprises a GaN buffer layer.

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