KR101171250B1 - METHOD OF FORMING InGaN QUANTUM DOTS - Google Patents

Abstract

The present disclosure provides a method of forming an indium gallium nitride (InGaN) quantum dot, the method comprising: repeatedly alternately stacking a thin film dominated by InN and a thin film dominated by GaN; And forming an In _x Ga _1-x N (0 <x <1) quantum dot by heating and heating the alternatingly stacked InN-dominant thin film and GaN-dominant thin film. In _x Ga ₁ A structure of _-x N (0 <x <1) quantum dots forms an active layer, and InN is embedded in GaN in the active layer to form a method of forming indium gallium nitride quantum dots.

Quantum dots, active layer, nitride, indium, gallium, elevated temperature, heat treatment, blue, near infrared

Description

Method for forming indium gallium nitride quantum dots {METHOD OF FORMING InGaN QUANTUM DOTS}

The present disclosure relates to a method of forming indium gallium nitride quantum dots as a whole, and more particularly to a method of forming indium gallium nitride quantum dots having a wide range of adjustable indium composition.

Herein, the background art relating to the present disclosure is provided, and these are not necessarily meant to be known arts.

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

As the substrate 100, a GaN-based substrate is used as the homogeneous substrate, and a sapphire substrate, a SiC substrate, or a Si substrate is used as the heterogeneous substrate. Any substrate may be used as long as the group III nitride semiconductor layer can be grown. When a SiC substrate is used, the n-side electrode 800 may be formed on the SiC substrate side.

Group III nitride semiconductor layers grown on the substrate 100 are mainly grown by MOCVD (organic metal vapor growth method).

The buffer layer 200 is to overcome the difference in lattice constant and thermal expansion coefficient between the hetero substrate 100 and the group III nitride semiconductor, and preferably is not doped prior to growth of the n-type group III nitride semiconductor layer 300. The GaN layer is grown, which may be viewed as part of the buffer layer 200 or as part of the n-type group III nitride semiconductor layer 300.

In the n-type group III nitride semiconductor layer 300, at least a region (n-type contact layer) on which the n-side electrode 800 is formed is doped with impurities, and the n-type contact layer is preferably made of GaN, and mainly doped with Si. do.

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.

The p-type III-nitride semiconductor layer 500 is doped with an appropriate impurity such as Mg, and has an p-type conductivity through an activation process. U.S. Patent No. 5,247,533 describes a technique for activating a p-type III-nitride semiconductor layer by electron beam irradiation, and U.S. Patent No. 5,306,662 annealing the p-type Group III nitride semiconductor layer at a temperature of 400 DEG C or higher. A technique for activating is described, and US Patent Publication No. 2006/157714 discloses a p-type III-nitride semiconductor layer without an activation process by using ammonia and a hydrazine-based source material together as a nitrogen precursor for growing the p-type III-nitride semiconductor layer. Techniques for having this p-type conductivity have been described.

The p-side electrode 600 is provided to supply a good current to the entire p-type group III nitride semiconductor layer 500. US Patent No. 5,563,422 is formed over almost the entire surface of the p-type group III nitride semiconductor layer. A light-transmitting electrode made of Ni and Au in ohmic contact with the p-type III-nitride semiconductor layer 500 is described. US Pat. No. 6,515,306 discloses n on the p-type III-nitride semiconductor layer. A technique is described in which a type superlattice layer is formed and then a translucent electrode made of indium tin oxide (ITO) is formed thereon.

On the other hand, the p-side electrode 600 may be formed to have a thick thickness so as not to transmit light, that is, to reflect the light toward the substrate side, this technique is referred to as flip chip (flip chip) technology. U. S. Patent No. 6,194, 743 describes a technique relating to an electrode structure including an Ag layer having a thickness of 20 nm or more, a diffusion barrier layer covering the Ag layer, and a bonding layer made of Au and Al covering the diffusion barrier layer.

The p-side bonding pad 700 and the n-side electrode 800 are for supplying current and wire bonding to the outside, and US Patent No. 5,563,422 describes a technique in which the n-side electrode is composed of Ti and Al.

The passivation layer 900 is formed of a material such as silicon dioxide and may be omitted.

Meanwhile, the n-type III-nitride semiconductor layer 300 or the p-type III-nitride semiconductor layer 500 may be composed of a single layer or a plurality of layers, and recently, the substrate 100 may be formed by laser or wet etching. A technique for manufacturing a vertical light emitting device by separating from group III nitride semiconductor layers has been introduced.

FIG. 2 is a diagram illustrating an example of an InGaN quantum well layer described in US Pat. No. 5,959,307. The p-type group III nitride semiconductor layer 300 is grown after the Group III nitride semiconductor layer 300 and the InGaN quantum well layer 300 are grown. Prior to growing 500, the InGaN quantum well layer 400 is left for about 2 to 20 seconds, and has a thickness of 70 μs or less including the indium rich region 400a and the indium deficient region 400b in the transverse direction. Techniques for improving the efficiency of the light emitting device by forming the InGaN quantum well layer 400 is described, the average value of x in the In _x Ga _1-x N quantum well layer formed by this technique is only about 0.2.

3 is a view for explaining an example of a method of growing an InGaN quantum well layer described in US Patent Publication No. 2007/0075307, due to the large difference in lattice constant and thermal expansion coefficient between InN and another group III nitride semiconductor. Pointing out the difficulty of growing a high-quality InGaN quantum well layer having a high InN composition, supplying an In source and an N source, receiving Ga from a GaN layer located below, to form an In-rich InGaN layer (S1), By growing the cover layer (S3) through the growth stop state in which the supply of the In source is interrupted (S2), the region in which the amount of indium increases, the indium-rich region, and the amount of indium decreases in the stacking direction of the semiconductor layer. A technique for forming an In-rich In _x Ga _1-x N (x> 0.5) quantum well layer as a region is described.

In recent years, quantum dot (QD) structures have been attracting attention because they are three-dimensionally confined in charge, stable to heat, have little wavelength spread, and have high emission intensity. However, if the InGaN quantum dot is less In, the group III nitride semiconductor (Al _x Ga _y In _1-xy N (0≤x≤1,0≤y≤1,0≤x + y≤1)) is a lower layer of the quantum dot forming layer. It is difficult to form three-dimensional quantum dots due to the small difference between layers and lattice mismatches, and when the amount of In is too large, it is difficult to form quantum dots of uniform size, which results in a bad wavelength spread.

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, in a method of forming an indium gallium nitride (InGaN) quantum dot, a thin film in which InN is dominant and a thin film in which GaN is dominant are alternately repeatedly stacked. Doing; And forming an In _x Ga _1-x N (0 <x <1) quantum dot by heating and heating the alternatingly stacked InN-dominant thin film and GaN-dominant thin film. In _x Ga ₁ A method of forming an indium gallium nitride quantum dot characterized in that a structure of _-x N (0 <x <1) quantum dots forms an active layer and InN is embedded in GaN in the active layer. Preferably, the InN thin film and the GaN thin film can be used to form an InGaN quantum dot structure including more In, but the present disclosure excludes that some In is included in the InN thin film and some In is included in the GaN thin film. It is not.

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).

4 is a view showing an example of a method of forming InGaN quantum dots according to the present disclosure, the basic concept is a heat treatment process after the InN thin film (1) and GaN thin film (2) alternately grown while varying the thickness according to the wavelength By mixing them through, it is possible to consider various cases (when the amount of In and the amount of In) is large depending on the In composition, but the case where the amount of In is small is shown in FIG. The GaN buffer layer was grown to a thickness of 500 nm on a Si (111) substrate at a temperature of 750 ° C., and then the temperature was lowered to a thickness of 0.3 nm and 1.5 nm, respectively, at a temperature of 450 ° C. After repeated growth alternately shows the process of raising the temperature to 700 ℃. As the temperature increases, the layers 1 and 2 repeatedly grown form a uniform InGaN quantum dot as shown in FIG. 5 through the mixing process. FIG. 6 is a diagram illustrating a photoluminescence (PL) measurement result for a quantum dot structure formed according to the method shown in FIG. 4, and shows an InGaN quantum dot related signal in a 454 nm region.

7 and 8 illustrate another example of a method of forming InGaN quantum dots according to the present disclosure, and show an InGaN quantum dot growth method in which In is added in an amount of about 95% or more. In the method shown in FIG. 4, increasing the composition of In means increasing the thickness of the InN thin film 1 or decreasing the thickness of the GaN thin film 2. However, when the thickness of the InN thin film 1 is increased, the melting point of In is low and the agglomeration property is strong, so that uniformity and density may decrease. Therefore, the composition of In is preferably controlled by inserting a relatively thin GaN thin film 2 at a thickness of 1 to 2 monolayers (ML) as a blocking layer. As shown in FIG. 4, after the growth conditions are the same, the InN thin film 1 is grown to a ratio of 90% of the thickness of the GaN thin film 2, and after the heat treatment, the InN thin film 1 and the GaN thin film 2 are dissolved. As the phase change occurs due to the difference of points, In is combined by diffusion, and a uniform InN quantum dot 3 and GaN layer 4 are formed. Therefore, a GaN barrier is formed on the InN quantum dot 3, thereby exhibiting a quantum effect. In other words, as shown in FIG. 8, InN quantum dots 3 are embedded in the GaN layer 4.

FIG. 9 is an AFM image of a quantum dot structure formed according to the method shown in FIG. 7, and shows measurement results corresponding to In _0.95 Ga _0.05 N quantum dot structures, and it can be seen that the amount of In is uniformly distributed.

FIG. 10 is a view showing photoluminescence (PL) measurement results of a quantum dot structure formed according to the method shown in FIG. 7. The emission characteristics of the quantum dot structure thus formed are confirmed by low temperature PL measurement, and have a long wavelength of about 1450 nm. Observations were made at. Therefore, it can be seen that by utilizing the growth method according to the present disclosure, the disadvantages of In can be compensated for, and a uniform quantum dot structure can be grown even at a large In amount.

11 is a diagram illustrating an example of a group III semiconductor light emitting device manufactured according to the present disclosure, in which the group III nitride semiconductor light emitting device is a sapphire substrate 10, a buffer layer 20, and a buffer layer grown on the sapphire substrate 10. The n-type group III nitride semiconductor layer 30 grown on the 20 and the n-type group III nitride semiconductor layer 30 grown on the InGaN quantum dot active layer 40 and the p-type group III nitride semiconductor grown on the active layer 40 P-type electrode 60 formed on layer 50, p-type group III nitride semiconductor layer 50, p-side bonding pad 70 formed on p-side electrode 60, and p-type group III nitride semiconductor layer 50 and the active layer 40 include an n-side electrode 80 formed on the n-type group III nitride semiconductor layer 30 exposed by mesa etching. Here, although a single InGaN quantum dot structure is provided in the active layer 40, a multi-layered InGaN quantum dot structure may be provided.

Various embodiments of the present disclosure will be described below.

(1) A method of forming an indium gallium nitride quantum dot, wherein the value of x is determined by adjusting the thickness of the thin film where GaN is dominant.

(2) A method of forming an indium gallium nitride quantum dot, wherein the value of x is 0.5 or more. According to the method according to the present disclosure, an In-rich (0.5 ≦ x) InGaN quantum dot can be constructed.

(3) A method of forming indium gallium nitride quantum dots, wherein the structure of In _x Ga _1-x N (0 <x <1) quantum dots forms an active layer. Although the method according to the present disclosure is suitable for forming an active layer, and the quantum dot structure is mainly used for the active layer, the method according to the present disclosure is not limited to being applied to the formation of the active layer, and may be applied wherever such a structure is required.

(4) A method of forming an indium gallium nitride quantum dot, wherein the GaN-dominant thin film is controlled to a thickness of 2 monolayers or less. Through this method, it is possible to make a structure having a large amount of In composition, such as In _0.95 Ga _0.05 N quantum dot structure active layer.

According to the method of forming one indium gallium nitride quantum dot according to the present disclosure, it is possible to form an indium gallium nitride nitride quantum dot that can control the indium composition in a wide range.

In addition, according to the method of forming another indium gallium nitride quantum dot according to the present disclosure, it is possible to form a uniform and high density InGaN quantum dot structure regardless of the composition of indium.

In addition, according to the method of forming another indium gallium nitride quantum dot according to the present disclosure, it is possible to form an InGaN quantum dot structure capable of emitting light in the near infrared.

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 an InGaN quantum well layer described in US Patent No. 5,959,307,

3 is a view for explaining an example of a method for growing an InGaN quantum well layer described in US Patent Publication No. 2007/0075307;

4 is a diagram illustrating an example of a method of forming an InGaN quantum dot according to the present disclosure;

5 is an AFM photograph of a quantum dot structure formed according to the method shown in FIG. 4;

FIG. 6 is a diagram showing a photoluminescence (PL) measurement result of a quantum dot structure formed according to the method shown in FIG. 4, wherein the x-axis is wavelength (nm) and the y-axis is intensity.

7 and 8 illustrate another example of a method of forming an InGaN quantum dot according to the present disclosure;

9 is an AFM photograph of a quantum dot structure formed according to the method shown in FIG.

FIG. 10 is a view showing photoluminescence (PL) measurement results for a quantum dot structure formed according to the method shown in FIG. 7, where the x axis is energy (eV) and the y axis is intensity.

11 is a view showing an example of a group 3 semiconductor light emitting device manufactured according to the present disclosure.

Claims (10)

In the method of forming indium gallium nitride (InGaN) quantum dots, Alternately laminating an InN dominated thin film and a GaN dominated thin film; And, And thermally heating the alternatingly stacked InN dominated thin film and GaN dominated thin film to form In _x Ga _1-x N (0 <x <1) quantum dots; A method of forming In _x Ga _1-x N (0 <x <1) quantum dots to form an active layer, wherein InN is embedded in GaN in the active layer. The method according to claim 1, A method of forming indium gallium nitride quantum dots, wherein the value of x is determined by controlling the thickness of the thin film where GaN dominates. The method according to claim 1, A method of forming an indium gallium nitride quantum dot, characterized in that the value of x is 0.5 or more. The method according to claim 1, InN is the predominant thin film is InN, A method of forming indium gallium nitride quantum dots, characterized in that GaN is the predominant thin film. delete delete The method according to claim 1, A method of forming an indium gallium nitride quantum dot characterized in that the GaN-dominant thin film is controlled to a thickness of 2 monolayer or less. The method according to claim 2, A method of forming an indium gallium nitride quantum dot characterized in that the thickness ratio of the thin film dominated by InN and the thin film dominated by GaN is 9: 1. The method of claim 4, A method of forming indium gallium nitride quantum dots, wherein the structure of In _x Ga _1-x N (0 <x <1) quantum dots forms an active layer. In claim 9, A method of forming an indium gallium nitride quantum dot, characterized in that the active layer is provided with a structure consisting of a plurality of In _x Ga _1-x N (0 <x <1) quantum dots.

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