KR101051327B1 - Iii-nitride semiconductor light emitting device - Google Patents

Abstract

PURPOSE: A group III nitride semiconductor light-emitting diode is provided to reduce internal electric field due to a piezoelectric field and a spontaneous polarization by controlling a composition and a junction of a deep quantum well layer and a shallow quantum well layer. CONSTITUTION: A group III nitride semiconductor layer has first conductivity. A group III nitride semiconductor layer has second conductivity different from the first conductivity. A shallow quantum well layer is positioned among groups I and III nitride semiconductor layers and groups II and III nitride semiconductor layers and is formed with an In(x1)Al(y1)Ga(1-x1-y1)N (0<=x1<=1, 0<=y1<=1, 0<=x1+y1<=1). A second shallow quantum well layer is positioned among the groups I and III nitride semiconductor layers and the groups II and III nitride semiconductor layers and is formed with In(x2)Al(y2)Ga(1-x2-y2)N (0<=x2<=1, 0<=y2<=1, 0<=x2+y2<=1). A deep quantum well layer is formed with a compound semiconductor defined by In(x3)Al(y3)Ga(1-x3-y3)N (0<=x3<=1, 0<=y3<=1, 0<=x3+y3<=1).

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 in which light gain is improved by reducing the effects of piezoelectric fields and spontaneous polarization by suitably composition and thickness.

Here, the group III nitride semiconductor light emitting device means a semiconductor optical device that generates light through recombination of electrons and holes, and the group III nitride semiconductor is, for example, In (x) Al (y) Ga (1-xy). N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1).

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

In general, light emitting devices using III-V nitride semiconductors and II-VI compound semiconductors can be implemented in various fields such as flat panel displays and optical communications because they can be implemented in blue violet and blue green colors.

However, in the light emitting device using the III-V nitride semiconductor and the II-VI compound semiconductor, stress is applied to the active layer, thereby causing piezoelectric field and spontaneous polarizations to cause other III-V group semiconductors. Compared with the light emitting device using the semiconductor, the light gain is deteriorated.

Various studies have been conducted to minimize such piezoelectric fields and spontaneous polarization. Among them, methods for minimizing piezoelectric fields and spontaneous polarization using non-polar or semi-polar substrates [Park et al., Phys Rev B 59, 4725 (1999), Waltereit et al. , Nature 406, 865 (2000). However, this method has a problem in that defects occur frequently in the fabrication of devices due to inadequate growth technology for hetero-crystal growth, and thus, device characteristics are not superior to theoretical expectations [K. Nishizuka et al., Appl. Phys. Lett. 87, 231901 (2005).

Alternatively, the cladding layer is composed of a four-membered film and the composition ratio of aluminum (Al) is increased to increase the restraint effect of the carrier, thereby improving luminous efficiency. [Zhang et al., Appl. Phys. Lett. 77, 2668 (2000), Lai et al., IEEE Photonics Technol Lett. 13, 559 (2001). However, this method has a disadvantage in that the piezoelectric field and spontaneous polarization cannot be eliminated fundamentally. However, recent research results [Ahn et al., IEEEJ. Quantum Electron. 41, 1253 (2005), it is reported that the use of a four-barrier barrier has an effect of improving the light gain due to the transmitter restraining effect of the quantum wells.

Alternatively, based on the theory that the ratio of indium in the quantum well in the InGaN / InGaAlN quantum well having a four-layer barrier can be found, the composition ratio of the quaternary membrane in which the internal electric field due to the piezoelectric field and the spontaneous polarization disappears can be found. Method for remarkably improving the light emitting characteristics of optical devices such as well light emitting diode (LED) and laser diode (LD) [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-film barrier are extremely difficult.

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).

To this end, the present disclosure provides a first group III nitride semiconductor layer having a first conductivity, a second group III nitride semiconductor layer having a second conductivity different from the first conductivity, a first group III nitride semiconductor layer, and a second Located between group III nitride semiconductor layers and defined as In (x1) Al (y1) Ga (1-x1-y1) N (0≤x1≤1, 0≤y1≤1, 0≤x1 + y1≤1) The first shallow quantum well layer (shallow-well) consisting of a compound semiconductor, and between the first group III nitride semiconductor layer and the second group III nitride semiconductor layer, and In (x2) Al (y2) Ga (1- a second shallow quantum well layer made of a compound semiconductor defined by x 2 -y 2) N (0 ≦ x2 ≦ 1, 0 ≦ y2 ≦ 1, 0 ≦ x2 + y2 ≦ 1), and In (x3) Al (y3) Ga A first shallow quantum well layer and a second shallow quantum well layer, consisting of a compound semiconductor defined as (1-x3-y3) N (0≤x3≤1, 0≤y3≤1, 0≤x3 + y3≤1) A deep quantum well positioned between and in contact with the first shallow quantum well layer and the second shallow quantum well layer, respectively As a dip-well, a deep quantum well layer satisfying 0.1 ≦ x3 ≦ 0.3 and x1 <x3, x2 <x3 has an energy band gap smaller than that of the first shallow quantum well layer and the second shallow quantum well layer. Provided is a Group III nitride semiconductor light emitting device comprising a dip-well.

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

1 is a model for obtaining stress and strain applied to a plurality of thin film layers,
2 is a view showing an example of a group III nitride semiconductor light emitting device according to the present disclosure;
3 is a graph showing calculation results of an energy band gap and a wave function of an example of a group III nitride semiconductor light emitting device having no deep quantum well layer and a group III nitride semiconductor light emitting device having a deep quantum well layer according to the present disclosure;
FIG. 4 shows wavefunction distributions for the ground state of electrons (blue) and holes (red) when the thickness L _w of the quantum wells is 3 nm and 5 nm, respectively. graph shown in dip-shaped quantum well (indicated by a solid line),
5 shows theoretically calculated dipole matrix values of conventional quantum wells (indicated by dotted lines) and dip-shaped quantum wells in accordance with the present disclosure (indicated by solid lines) according to different wavelengths and thicknesses of quantum wells. Graph showing
6 is a graph showing spontaneous luminous efficiency for a typical quantum well (indicated by dotted lines) and an example of dip-shaped quantum wells (indicated by solid lines) according to different wavelengths and thicknesses of quantum wells;
7 is a graph showing an energy band gap of an example of a group III nitride semiconductor light emitting device having a deep quantum well layer having a deep quantum well layer according to the present disclosure;
FIG. 8 is a graph illustrating variation of an oscillation wavelength according to changes of a deep quantum well layer and a shallow quantum well layer in the group III nitride semiconductor light emitting device of FIG. 7;
FIG. 9 is a graph illustrating a change in the size of the dipole matrix according to the change of the deep quantum well layer and the shallow quantum well layer in the dip-shaped quantum well shown in FIG.
FIG. 10 is a graph illustrating a change in magnitude of light gain according to changes of a deep quantum well layer and a shallow quantum well layer in the dip-shaped quantum well shown in FIG. 7.

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

The group III nitride semiconductor light emitting device according to the present disclosure has a dip-shaped quantum well, and has a feature of improving the light gain by appropriately adjusting the composition and thickness of the dip-shaped quantum well. The dip-shaped quantum well layer comprises a first shallow quantum well layer, a second shallow quantum well layer, and a deep quantum well layer formed between the first shallow quantum well layer and the second shallow quantum well layer. The deep quantum well layer has an energy band gap smaller than the energy band gap of the first shallow quantum well layer and the second shallow quantum well layer, and the composition of the deep quantum well layer, the first shallow quantum well layer and the second shallow quantum well layer. And thickness are appropriately selected to reduce the spatial separation of the wave functions of electrons and holes. As a result, the influence of the piezoelectric field and the spontaneous polarization is greatly reduced, and the optical gain is improved.

The energy band gap of the deep quantum well layer, the first shallow quantum well layer and the second shallow quantum well layer may be adjusted by changing the indium content of the deep quantum well layer, the first shallow quantum well layer and the second shallow quantum well layer. . When the indium content of the deep quantum well layer is higher than the indium content of the first shallow quantum well layer and the second shallow quantum well layer, the energy band gap of the deep quantum well layer is the first shallow quantum well layer and the second shallow quantum well layer. It can be smaller than the energy band gap of. In particular, the present disclosure provides the indium content and thickness of the deep quantum well layer, and the first shallow quantum well layer and the second shallow quantum well layer disposed above and below the deep quantum well layer to improve light gain of the group III nitride semiconductor light emitting device. An effective range of indium content and thickness is disclosed.

Prior to describing an example of the Group III nitride semiconductor light emitting device according to the present disclosure, in a structure in which a plurality of thin film layers are stacked, a strain applied to each thin film layer, a piezoelectric field and spontaneous generation generated in the thin film layer by the strain. The polarization, the piezoelectric field, the internal electric field applied to each thin film layer by spontaneous polarization, and the light gain will be analyzed through a mathematical method.

bracket In a thin film layer  Applied strain and the resulting Piezoelectric , Spontaneous polarization  And Internal electric field

The internal electric field applied to the quantum well and the barrier by the piezoelectric field PZ and the spontaneous polarization SP is given by Equation 1 as follows. Bykhovski, A. D., Gelmont, B. L. & Shur, M. S. Elastic strain relaxation and piezoeffect in GaN-AlN, GaN-AlGaN and GaN-InGaN superlattices. J. Appl. Phys. 81, 6332-6338 (1997).]

[Equation 1]

Where P is the polarization, subscripts w and b, quantum wells and barriers, L is thickness, and ε is the static dielectric constant.

1 is a model for obtaining stresses and strains applied to a plurality of thin film layers. Hereinafter, a method of mathematically obtaining strain and stress applied to each layer in a structure composed of a plurality of thin film layers as shown in FIG. 1 will be described. For reference, the mathematical interpretation of strain and stress applied to each layer follows the method suggested by Nakajima (Nakajima, J. Appl. Phys. 72, 5213 (1992)).

In FIG. 1, the stress applied to the i th layer is F _i , the moment of the i layer is M _i , the thickness of the _i layer is d _i , the lattice constant of the i layer is a _i , and the Young's modulus of the i layer. ) Is defined as the curvature of the structure consisting of E _i , i thin film layer as R, the stress applied to the i th layer follows the equation (2) below.

[Equation 2]

On the other hand, the condition for maintaining the i-th layer and the (i + 1) -th layer in an equilibrium state is shown in Equation 3 below.

&Quot; (3) &quot;

Where l _i is the effective lattice constant of the i-th layer taking into account thermal expansion, T is the temperature of the lattice, and e _i is the strain applied to the i-th layer.

When the stress applied to the i th layer is obtained by combining Equation 2 and Equation 3, Equation 4 below.

&Quot; (4) &quot;

On the other hand, the curvature R of the structure consisting of i thin film layers is given by the following equation (5).

[Equation 5]

Therefore, the strain applied to the i-th layer from the equations (4) and (5) is obtained by the following equation (6).

&Quot; (6) &quot;

Where ε _xxi is the effective strain applied to the ith layer

In the above equation, as shown in Equation 2, the sum of stress acting on the structure composed of the plurality of thin film layers is 0, and when the equations 3 to 6 are interpreted, the strain is properly distributed to each thin film layer. Can be.

The group III nitride semiconductor light emitting device according to the present disclosure uses the principle of distributing strain, and when the compressive strain is induced to act on a specific thin film layer (deep quantum well layer), the other thin film layer (the first shallow quantum well layer and the second layer) The compressive strain acting on the shallow quantum well layer is reduced compared to the case without the deep quantum well layer.

On the other hand, the piezoelectric field and spontaneous polarization applied to each layer may be calculated using the strains calculated through Equations 2 to 6 above. Piezoelectric and spontaneous polarization analysis using strain follows the method proposed by Bernardini (Phys. Stat. Sol. (B) 216,392 (1999)), and is calculated as in Equation 7 below.

[Equation 7]

(E _i is the piezoelectric field applied to the i-th layer and the effective field by spontaneous polarization)

Light gain

Next, we will look at the mathematical interpretation of light gain.

The optical gain spectrum is calculated using a non-Markovian gain model with multibody effects (SH Park, SL Chung and D Ahn, "Interband relaxation time effects on non-Markovian gain with many-body effects and comparison with experiment", Semicond. Sci. Technol., Vol. 15 pp. 2003-2008). Specifically, the light gain having the multi-body effect including the anisotropy of the valence band dispersion is expressed by Equation 8 below.

[Equation 8]

Where ω is the angular velocity, μ ₀ is the permeability in vacuum, ε is the dielectric constant, σ = U (or L) is the upper (or lower) block of the effective mass Hamiltonian, and e is the electron's The amount of charge, m ₀ is the mass of free electrons, k _∥ is the size of the surface wave vector in the quantum well plane, L _w is the thickness of the quantum well, ｜ M _nm ｜ ² is the matrix component of the strained quantum well . In addition, f _n ^c and f _m ^v are Fermi functions for the probability of electron occupancy in the conduction band and valence band, respectively, and the subscripts n and m are the electronic and hole states in the conduction band, respectively. Indicates.

In addition, the re-standardized transition energy between the electron and the hole is represented by Equation 9 below.

[Equation 9]

Where E _g is the energy band gap, and ΔE _SX and ΔE _CH are the screened exchange and coulomb hole contributions for energy band gap renormalization, respectively (WW Chow, M. Hagerott, A). Bimdt and SW Koch, "Threshold conditions for ultraviolet wavelength GaN quantum-well laser", IEEE J. Select. Topics Quantum Electron., Vol. 4, pp. 514-519, 1998).

A Gaussian line shape function L (ω, k _∥ , φ) is expressed by Equation 10 below.

[Equation 10]

In the above equation, Q (k _∥ , h _w , φ ₀ ) causes the coulomb rise of the excitonic or energy band transition. The above-described line shape function is the simplest Gaussian of Non-Markobian quantum kinetics, and is described by Equations 11 and 12 below.

[Equation 11]

[Equation 12]

The interband relaxation time τ _in and the co-relation time τ _c between the energy bands are regarded as constants and calculated as 25 fs and 10 fs, respectively.

Hereinafter, an example of a group III nitride semiconductor light emitting device according to the present disclosure will be described with reference to the drawings.

2 is a diagram illustrating an example of a group III nitride semiconductor light emitting device according to the present disclosure.

2, an example of a group III nitride semiconductor light emitting device according to the present disclosure may include an n-type semiconductor layer (first nitride semiconductor layer) 10, a p-type semiconductor layer (second nitride semiconductor layer) 30, A first shallow quantum well layer 51, a second shallow quantum well layer 53, and a deep quantum well layer 70, the n-type semiconductor layer 10, The first shallow quantum well layer 51 and the second shallow quantum well layer 53 and the p-type semiconductor layer 30 are sequentially stacked, and the deep quantum well layer 70 is formed of the first shallow quantum well layer 51 and Located between the second shallow quantum well layer 53, the first shallow quantum well layer 51 and the second shallow quantum well layer 53, respectively.

The n-type semiconductor layer 10 and the p-type semiconductor layer 30 may be made of GaN. The first shallow quantum well layer 51 is defined as In (x1) Al (y1) Ga (1-x1-y1) N (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1, 0 ≦ x1 + y1 ≦ 1). It may be made of a semiconductor compound. The second shallow quantum well layer 53 is defined as In (x2) Al (y2) Ga (1-x2-y2) N (0≤x2≤1, 0≤y2≤1, 0≤x2 + y2≤1). It may be made of a semiconductor compound. The deep quantum well layer 70 is a semiconductor defined as In (x3) Al (y3) Ga (1-x3-y3) N (0≤x3≤1, 0≤y3≤1, 0≤x3 + y3≤1). It may consist of a compound.

The deep quantum well layer 70 suppresses or reduces spatial separation of the wave function of the electron and the wave function of the hole by piezoelectric field and spontaneous polarization in the quantum well. In other words, it induces a wave function localization. The wave function means a function representing the energy band change of the quantum well with respect to the thickness of the quantum well. In the quantum well, the wave function of the electron and the wave function of the hole exist, respectively, and the wave function localization means that the wave function of the electron and the wave function of the hole are not deflected in opposite directions.

In order to induce the wave function localization, the deep quantum well layer 70 should have a smaller energy band gap than the first shallow quantum well layer 51 and the second shallow quantum well layer 53, Adjustment is possible by controlling the indium content of the first shallow quantum well layer 51, the second shallow quantum well layer 53, and the deep quantum well layer 70. Specifically, the indium content of the deep quantum well layer 70 is preferably controlled to be greater than the indium content of the first shallow quantum well layer 51 and the second shallow quantum well layer 53.

In one example of the group III nitride semiconductor light emitting device according to the present disclosure, the wave function in the quantum well is as follows.

3 is a graph showing calculation results of energy band gaps and wave functions of an example of a group III nitride semiconductor light emitting device having no deep quantum well layer and a group III nitride semiconductor light emitting device having a deep quantum well layer according to the present disclosure. .

The energy band gap and wave function of the group III nitride semiconductor light emitting device (hereinafter, referred to as a conventional group III nitride semiconductor light emitting device) having no deep quantum well layer are shown in FIG. 3 (a), and the deep quantum well layer according to the present disclosure. The energy band gap and the wave function of the group III nitride semiconductor light emitting device having the same are shown in FIG. 3 (a) and 3 (b), thickness and indium composition ratios of the conventional group III nitride semiconductor light emitting device and the light emitting device according to the present disclosure are determined such that the oscillation wavelength is 530 nm.

Referring to FIG. 3 (a), in the conventional nitride-based bladder device, an n-type semiconductor layer / quantum well layer / p-type semiconductor layer has a structure of GaN / In (x) Ga (1-x) N / GaN. The indium content (x) of the quantum well layer (In (x) Ga (1-x) N) is 14.6% and the thickness L _w is 5 nm. The wave function of the electron is shown by the dotted line graph at the top in Figure 3 (a), the wave function of the hole is shown by the dotted line graph at the bottom. From the graphs, it can be seen that in the conventional group III nitride semiconductor light emitting device, the wave function of electrons and the hole function of holes are largely deflected in opposite directions by the piezoelectric field and the internal electric field induced by spontaneous polarization.

Meanwhile, in an example of the group III nitride semiconductor light emitting device according to the present disclosure shown in FIG. 3B, a dip-shapped quantum well layer, that is, a first shallow quantum well layer / deep quantum well layer / second shallow quantum well layer structure In (x1) Ga (1-x1) N / In (x3) Ga (1-x3) N / In (x2) Ga (1-x2) N structure, a dip-shaped quantum well is a deep quantum well It means a quantum well as shown in Figure 3 (b) including a layer.

The indium content of the first shallow quantum well layer and the second shallow quantum well layer is 5%, and the indium content of the deep quantum well layer is 11.8%. Further, the thickness L _w2 of the deep quantum well layer is 2 nm, and the thicknesses L _w1 and L _{w3 of} the first shallow quantum well layer and the second shallow quantum well layer above and below the deep quantum well layer are 1.5 nm, respectively. Looking at the wave function in the group III nitride semiconductor light emitting device having such a structure, the degree of deflection between the wave function of the electron represented by the dotted line graph at the top and the hole wave function represented by the dotted line graph at the bottom of FIG. It can be seen that it is localized to the middle part of the quantum well.

On the other hand, the localization of the electron wave function and the hole wave function is related to the thickness of the quantum well.

FIG. 4 shows wavefunction distributions for the ground state of electrons (blue) and holes (red) when the thickness L _w of the quantum wells is 3 nm and 5 nm, respectively. This is a graph of a dip-shaped quantum well (indicated by a solid line). As shown in FIGS. 4A and 4B, when the thickness Lw of the quantum well is 3 nm, the wave function (blue) and the hole of the electron are prepared in the case where the thickness Lw of the quantum well is 5 nm. It can be seen that the localization of the wave function (red) is achieved well. Therefore, the thinner the thickness of the quantum well, the greater the effect of the wave function localization induction.

5 shows theoretically calculated dipole matrix values of conventional quantum wells (indicated by dotted lines) and dip-shaped quantum wells in accordance with the present disclosure (indicated by solid lines) according to different wavelengths and thicknesses of quantum wells. Is a graph.

Referring to FIG. 5, it can be seen that one example of the group III nitride semiconductor light emitting device according to the present disclosure has a relatively constant dipole moment value than that of a conventional group III nitride semiconductor light emitting device even when various wavelengths are applied. have. This improvement is considered to be because an example of the group III nitride semiconductor light emitting device according to the present disclosure has a deep quantum well layer.

6 is a graph showing spontaneous light emission efficiency for a typical quantum well (indicated by dotted lines) and an example of dip-shaped quantum wells (indicated by solid lines) according to different wavelengths and thicknesses of quantum wells.

6 shows an example of a group III nitride semiconductor light emitting device (represented by a dotted line) and a group III nitride semiconductor light emitting device according to the present disclosure when the thickness Lw of the quantum well is 3 nm and 5 nm, respectively (solid line Shows the result of theoretically calculating the spontaneous emission rate of the (s). In FIG. 6, the blue graph shows the case where the oscillation wavelength is 440 nm and the red graph shows the case where the oscillation wavelength is 530 nm.

As shown in FIG. 6, a group III nitride semiconductor light emitting device according to the present disclosure is provided because a deep quantum well layer is interposed between the first shallow quantum well layer and the second shallow quantum well layer regardless of the thickness and oscillation wavelength of the quantum well. It can be seen that one example of the device is superior because the spontaneous light emission efficiency is much higher than the conventional group III nitride semiconductor light emitting device. For reference, the spontaneous emission characteristic analysis of FIG. 6 is based on the model presented by Ahn (Ahn, IEEE J. Quantum Electron. 34, 344 (1998) & Ahn et al., IEEE J. Quantum Electron. 41, 1253 ( 2005).

7 is a graph showing an energy band gap of an example of a group III nitride semiconductor light emitting device having a deep quantum well layer and having a dip-shaped quantum well according to the present disclosure. 7 shows potential profiles of the conduction and valence bands for the deep quantum well layer L _w2 , the first shallow quantum well layer L _w1 , and the second shallow quantum well layer L _w3 , and the electrons in the ground state. And the wave function (dotted line) of the hole. The thickness and the indium composition ratio of the first shallow quantum well layer L _w1 and the second shallow quantum well layer L _w3 were selected to be the same. The barrier layer outside the first shallow quantum well layer L _w1 and the second shallow quantum well layer L _w3 may be made of GaN.

The internal electric field in the thin film layer is determined using a periodic boundary condition represented by the following equation (13).

[Equation 13]

은 박막층의 두께를 나타내고, F는 박막층에서 내부전계를 나타낸다. Using Equation 13, the sum is calculated for all thin film layers, including the barrier layer,

Represents the thickness of the thin film layer, and F represents the internal electric field in the thin film layer.

The internal electric field of the nth thin film layer is represented by the following equation (14).

[Equation 14]

Where ε is the dielectric constant.

Unlike the dip-shaped quantum well, if the indium composition ratio of the first shallow quantum well layer and the second shallow quantum well layer is the same as the deep quantum well layer, a single quantum well is formed. In general, because of the difference in piezoelectric and spontaneous polarization between the barrier layer and the quantum well layer, a large internal electric field is formed. do.

On the other hand, in the dip-shaped quantum well according to the present disclosure, the spatial separation between the wave function of the electron and the wave function of the hole is greatly reduced by interposing a deep quantum well layer as described above. The optical gain is improved by greatly reducing the effects of spontaneous polarization.

The present disclosure further improves the light emission gain, wherein the indium composition ratio and thickness of the first shallow quantum well layer and the second shallow quantum well layer in the dip-shaped quantum well are constant, and the deep quantum well layer ( The effects of the dip-well thickness and the indium composition ratio on the light gain were examined. As a result, the indium composition ratio and thickness of the deep quantum well layer, the indium composition ratio of the first shallow quantum well layer and the second shallow quantum well layer on both sides of the deep quantum well layer, A suitable range of thickness is disclosed.

FIG. 8 is a graph illustrating a change in oscillation wavelength according to changes of a deep quantum well layer and a shallow quantum well layer in the group III nitride semiconductor light emitting device of FIG. 7.

FIG. 8 (a) shows that the first shallow quantum well layer on both sides of the deep quantum well layer and the second shallow quantum well layer each have an indium composition ratio of 0.05 and a thickness of 10 ms. In the case where the indium composition ratio of each of the second shallow quantum well layers is 0.1 μs, the oscillation wavelength (vertical axis) is changed according to the thickness (10 μs, 20 μs, 30 μs) of the deep quantum well layer and the change of the indium composition ratio (horizontal axis). Ellipses marked on the vertical axis represent single quantum wells different from the present disclosure.

In both cases of FIGS. 8 (a) and 8 (b), as the composition ratio of indium of the deep quantum well layer increases, the long wavelength of the oscillation wavelength is rapidly increased. In addition, it can be seen that the longer the wavelength, the greater the thickness of the deep quantum well layer. These results indicate that the potential energy induced by the internal electric field of a quantum well is given by the product of the internal electric field and the thickness of the quantum well. As the thickness of the deep quantum well layer increases, the potential energy induced by the internal electric field of the deep quantum well layer increases. This is because it increases. In the case of 8 (a) having a smaller indium composition ratio of the shallow quantum well layer, the oscillation wavelength has a longer wavelength than 8 (b). It is big.

The internal electric field is determined by the difference in the sum of the piezoelectric field and the spontaneous polarization between the quantum well layer and the barrier layer. For example, when the thickness L _w = 30 kPa of the deep quantum well layer, the indium composition ratio is 0.2, and the indium composition ratio of the shallow quantum well layer is 0.1 and 0.05, respectively, the internal electric fields are 2.17 and 2.28 MV / cm.

FIG. 9 is a graph illustrating a change in the size of the dipole matrix according to the change of the deep quantum well layer and the shallow quantum well layer in the group III nitride semiconductor light emitting device of FIG. 7.

FIG. 9 (a) shows the case where the indium composition ratio of the first shallow quantum well layer and the second shallow quantum well layer is 0.05 mm in thickness, and FIG. 9 (b) The indium of the first shallow quantum well layer and the second shallow quantum well layer. When the composition ratio is 0.1 μs, the thickness of the deep quantum well layer (10 μs, 20 μs, 30 μs) and the dipole matrix according to the change of the indium composition ratio (horizontal axis) are shown. Ellipses marked on the vertical axis represent single quantum wells different from the present disclosure.

9 (a) and 9 (b), the indium composition ratio of the deep quantum well layer and the indium composition ratio are 0.1 compared to the case where the indium composition ratio of the first shallow quantum well layer and the second shallow quantum well layer is 0.05. It can be seen that the size of the dipole matrix is large regardless of. This is because the former has a smaller internal electric field due to the piezoelectric field and the spontaneous polarization than the latter. For example, when the indium composition ratio of the deep quantum well layer is 0.15 and the thickness is 10Å, the theoretical calculated electric fields at the indium composition ratio of 0.05 and 0.1 in the shallow quantum well layer are 0.59 MV / cm and 1.11 MV / cm, respectively. do.

On the other hand, it can be seen that the indium composition ratio of the shallow quantum well layer is more affected by the indium composition ratio of the deep quantum well layer than the case where the indium composition ratio is 0.05. That is, as the thickness of the deep quantum well layer is larger in the case of FIG. 9 (a) than in the case of FIG. 9 (b), the size of the dipole matrix decreases rapidly as the indium composition ratio of the deep quantum well layer increases. Can be. This is mainly because the effect of the internal electric field increases as the thickness of the deep quantum well layer increases. However, in FIG. 9 (b) where the indium composition ratio of the shallow quantum well layer is relatively large as 0.1, the size reduction effect of the dipole matrix due to the increase in the thickness of the deep quantum well layer and the indium composition ratio is significantly weakened. Able to know.

FIG. 10 is a graph illustrating a change in magnitude of light gain according to changes of a deep quantum well layer and a shallow quantum well layer in the group III nitride semiconductor light emitting device of FIG. 7.

FIG. 10 (a) shows the case where the indium composition ratios of the first shallow quantum well layer and the second shallow quantum well layer are 0.05 mm each, and FIG. 10 (b) shows the first shallow quantum well layer and the second shallow quantum well layer. In the case where the indium composition ratio of is 0.1Å, the thickness of the deep quantum well layer (10Å, 20Å, 30Å) and the magnitude (vertical axis) of light gain according to the change of the indium composition ratio (horizontal axis) are shown. The graph of Figure 10 is the carrier (carrier) density of 10 × 10 ¹² cm ^- the results of a home ² and calculate.

10 (a) and 10 (b), it can be seen that the light gain is greater than that of the case where the indium composition ratio of the shallow quantum well layer is 0.05. This result may be because the internal electric field is smaller in the case where the indium composition ratio of the shallow quantum well layer is 0.05 than in the case of 0.1. In addition, it can be seen that the light gain increases more rapidly as the indium composition ratio of the deep quantum well layer is larger than the case where the thickness of the deep quantum well layer is larger than 10 μs. This is because as the indium composition ratio increases, the depth of the deep quantum well layer becomes deeper, thereby increasing the separation of quasi-Fermi level. For example, when the indium composition ratio of the deep quantum well layer is 0.05 and 0.2, the separation of quasi-Fermi level is calculated as 0.013 eV and 0.12 eV, respectively. However, it can be seen that as the thickness of the deep quantum well layer increases, the increase rate of light gain decreases rapidly. In FIG. 10 (b), where the indium composition ratio of the shallow quantum well layer is relatively large as 0.1, it can be seen that the light gain gradually increases as the indium composition ratio of the deep quantum well layer increases.

Summarizing the analysis results of the graphs illustrated in FIGS. 7 to 10, parameters for improving light gain in a dip-shaped quantum well made of InGaN / GaN may be determined as follows. First, when the indium composition ratio of the shallow quantum well layer is 0.05, which is relatively small, the internal field influence is smaller than that of 0.1, and thus the light gain is greater. In addition, when the thickness of the deep quantum well layer is relatively small and the indium composition ratio of the shallow quantum well layer is relatively small (0.05), the internal electric field effect can be almost ignored, and the separation of the quasi-Fermi level is increased, thereby increasing the indium composition ratio of the deep quantum well layer. As increases, the optical gain increases rapidly.

On the other hand, as the thickness of the well increases, the increase rate of light gain significantly decreases due to the influence of the internal electric field. When the indium composition ratio of the shallow quantum well layer is relatively large 0.1, the light gain gradually increases as the indium composition ratio of the deep quantum well layer increases. Based on the analysis results of the graphs described with reference to FIG. 10 in FIG. 7, suitable conditions of the deep quantum well layer and the shallow quantum well layer for further improving the light gain can be found.

Referring to the graph analysis illustrated in FIGS. 7 to 10, it is preferable that the indium composition ratio of the shallow quantum well layer is 0.05 or more and 0.1 or less to effectively reduce the piezoelectric field and the internal electric field caused by spontaneous polarization. If the indium composition ratio of the shallow quantum well layer is less than 0.05, it is disadvantageous because the lattice difference between the deep quantum well layer is large and the stress is large.

The thickness of the shallow quantum well layer is preferably 5 kPa or more and 20 kPa or less. If the thickness of the shallow quantum well layer is less than 5 μs, the wave function is not well constrained, and if it is larger than 20 μs, the two-dimensional density of state of the active layer is disadvantageous.

It is preferable that the thickness of a deep quantum well layer is 5 kPa or more and 20 kPa or less. If the thickness of the deep quantum well layer is less than 5 μs, the wave function is not well constrained, and if it is larger than 20 μs, the two-dimensional density of state of the active layer is disadvantageous.

It is preferable that the indium composition ratio of the deep quantum well layer is 0.1 or more and 0.3 or less. If the indium composition ratio of the deep quantum well layer is less than 0.1, the quasi-Fermi level separation is disadvantageous, and if the indium composition ratio is greater than 0.3, the piezoelectric field and spontaneous polarization are increased.

Hereinafter, various embodiments of the present disclosure will be described.

(1) x1, x2 and x3 and the thickness of the deep quantum well layer, the thickness of the first shallow quantum well layer and the thickness of the second shallow quantum well layer are the spatial separation between the wave function of the electron and the wave function of the hole. Group III nitride semiconductor light-emitting device is selected to reduce, 0.05≤x1≤0.1, 0.05≤x2≤0.1.

(2) A group III nitride semiconductor light emitting device characterized in that the thickness of the deep quantum well layer is larger than the thickness of the first thin quantum well layer and larger than the thickness of the second thin quantum well layer.

(3) A group III nitride semiconductor light emitting element, wherein the deep quantum well layer has a thickness of 5 kPa or more and 20 kPa or less.

(4) A group III nitride semiconductor light emitting element, wherein the thickness of the first shallow quantum well layer and the second shallow quantum well layer is 5 kPa or more and 20 kPa or less, respectively.

(5) A group III nitride semiconductor light emitting element, wherein x1 = x2 and y1 = y2.

(6) A group III nitride semiconductor light emitting element, wherein x1 = x2 = 0.05.

(7) A group III nitride semiconductor light emitting element, wherein the deep quantum well layer has a thickness of 5 kPa or more and 20 kPa or less, and the thickness of the first shallow quantum well layer and the second shallow quantum well layer is 5 kPa or more and 20 kPa or less, respectively.

(8) a first barrier layer located between the first group III nitride semiconductor layer and the first shallow quantum well layer; And a second barrier layer positioned between the second Group III nitride semiconductor layer and the second shallow quantum well layer.

(8) the deep quantum well layer, the first shallow quantum well layer and the second shallow quantum well layer are made of InGaN, and the first barrier layer and the second barrier layer are at least selected from the group consisting of GaN, InGaN, AlInGaN and AlGaN. Group III nitride semiconductor light emitting device, characterized in that consisting of one.

According to the group III nitride semiconductor light emitting device according to the present disclosure, the separation of the wave function of the electron and the wave function of the hole in the quantum well due to the dip-shaped quantum well is greatly reduced, deep quantum well layer and shallow quantum By controlling the composition and thickness of the well layer to be bonded, the formation of the internal electric field by piezoelectric field and spontaneous polarization is reduced. Therefore, the light gain of the group III nitride semiconductor light emitting device is improved.

Claims (10)

A first group III nitride semiconductor layer having a first conductivity;
A second group III nitride semiconductor layer having a second conductivity different from the first conductivity;
Located between the first group III nitride semiconductor layer and the second group III nitride semiconductor layer, In (x1) Al (y1) Ga (1-x1-y1) N (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1 A first shallow quantum well layer made of a compound semiconductor defined by 0 ≦ x1 + y1 ≦ 1);
In (x2) Al (y2) Ga (1-x2-y2) N (0≤x2≤1, 0≤y2≤1), located between the first group III nitride semiconductor layer and the second group III nitride semiconductor layer A second shallow quantum well layer made of a compound semiconductor defined by 0 ≦ x2 + y2 ≦ 1); And
First compound consisting of a compound semiconductor defined as In (x3) Al (y3) Ga (1-x3-y3) N (0≤x3≤1, 0≤y3≤1, 0≤x3 + y3≤1) A deep quantum well layer positioned between the quantum well layer and the second shallow quantum well layer and in contact with the first shallow quantum well layer and the second shallow quantum well layer, respectively; 0.1 ≦ x3 ≦ 0.3 and x1 Group III nitride semiconductor light emitting device comprising: a deep quantum well layer having an energy band gap smaller than the energy band gap of the first shallow quantum well layer and the second shallow quantum well layer satisfying <x3, x2 <x3 . The method according to claim 1,
x1, x2, and x3 and the thickness of the deep quantum well layer, the thickness of the first shallow quantum well layer and the thickness of the second shallow quantum well layer are to reduce the spatial separation between the wave function of the electron and the wave function of the hole. Group III nitride semiconductor light emitting device, characterized in that selected from 0.05≤x1≤0.1, 0.05≤x2≤0.1. The method according to claim 2,
A group III nitride semiconductor light emitting device, characterized in that the thickness of the deep quantum well layer is larger than the thickness of the first thin quantum well layer and larger than the thickness of the second thin quantum well layer. The method according to claim 3,
A group III nitride semiconductor light emitting device, characterized in that the thickness of the deep quantum well layer is 5 kW or more and 20 kW or less. The method according to claim 3,
The group III nitride semiconductor light emitting device of claim 1, wherein the first shallow quantum well layer and the second shallow quantum well layer have a thickness of 5 mW or more and 20 mW or less, respectively. The method according to claim 2,
A group III nitride semiconductor light emitting device, wherein x1 = x2 and y1 = y2. The method of claim 6,
A group III nitride semiconductor light emitting device, wherein x1 = x2 = 0.05. The method according to claim 7
A group III nitride semiconductor light-emitting device, wherein the deep quantum well layer has a thickness of 5 mW or more and 20 mW or less, and the thickness of the first shallow quantum well layer and the second shallow quantum well layer is 5 mW or more and 20 mW or less, respectively. The method according to claim 1,
A first barrier layer located between the first group III nitride semiconductor layer and the first shallow quantum well layer; And
And a second barrier layer disposed between the second Group III nitride semiconductor layer and the second shallow quantum well layer. The method according to claim 9,
The deep quantum well layer, the first shallow quantum well layer and the second shallow quantum well layer are made of InGaN, and the first barrier layer and the second barrier layer are made of at least one selected from the group consisting of GaN, InGaN, AlInGan, and AlGaN. Group III nitride semiconductor light emitting device.

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