KR20170094027A - Quantum well Photodetector having strain-compensated - Google Patents

Abstract

A photodetector according to the present invention is formed on a substrate and includes an InGaN/InAlN-stacked quantum well structure. The quantum well structure includes a stack structure of at least one well layer and at least one barrier layer which are alternatively stacked. In is added to the barrier layer and the well layer. When a stress epsilon xxx ranges from 0.3% to 0.8%, the thickness of the well layer has a range of 10 to 14 angstroms. Accordingly, the present invention can prevent a strain even if a lot of quantum well structures are stacked.

Description

[0001] The present invention relates to a strain compensated quantum well photodetector,

Field of the Invention [0002] The present invention relates to a photodetector, and more particularly, to a photodetector having a quantum well structure having a 1.55 mu m wavelength region band.

The intersubband (ISB) transition in the quantum well of an optical device has great potential in the optoelectronic region of the infrared region. ISB photodetectors have advantages over interband devices in speed and reproducibility. Of the materials used in ISB photodetectors, the III group nitride epitaxial junctions are interesting because they have very large band conduction offsets.

Room temperature ISB absorption in the 1.3 ㎛ - 1.55 ㎛ wavelength region has been reported for GaN / AlGaN and GaN / AIN quantum well structures. In particular, the AIN / GaN heterojunction structure is attractive due to the considerably large band offset of about 2 eV. However, for AIN / GaN heterojunction structures grown on GaN, a lattice mismatch of 2.5% is observed. This can lead to structural defects and cracks.

Therefore, there is a need to design GaN-based heterojunctions that can reduce lattice mismatch to minimize the formation of structural defects during epitaxial growth.

Recently, Akali et al. Have proposed an InGaN / InAlN quantum well structure instead of a GaN / AlN quantum well structure. In _y Al _1-y N is known to be lattice-matched to GaN at y = 0.185. In this report, it is known that x = 0.04 and y = 0.14 in the In _x Ga _1-x N / Al _1-y In _y N quantum well structures to obtain a 1.55 μm wavelength region. However, studies on strain compensated structures have not yet been made, and strain compensated quantum well structures are particularly useful when a large number of quantum wells are required.

Therefore, research on the quantum well structure of InGaN / AlInN is required.

Korean Patent Laid-Open Publication No. 2012-0024827

"Intersubband energies in Al1-yInyN / InxGa1-xN heterostructure with lattice constant close to aGaN", Akali et al., Superlattices and microstructures 52 (2012) 70-77,

As a technical means for solving the above-mentioned problems, it is an object of the present invention to provide a photodetector having a strain-compensated quantum well structure.

Another object of the present invention is to provide a photodetector having a structure in which a quantum well structure is stacked so as not to be strained as a whole.

As a technical means for solving the above-mentioned problems, one aspect of the present invention is a photodetector formed on a substrate and including an InGaN / InAlN stacked quantum well structure, wherein the quantum well structure includes at least one the it includes a stacked structure of an InGaN well layer and a barrier layer InAlN, but the respective in addition to the barrier layer and the well layer, the stress ε _xx The thickness of the barrier layer ranges from 10 A to 37 A when the thickness of the well layer is in the range of 10 A to 14 A in the range of 0.3 to 0.8%. When the stress ε _xx is determined, the amount of In injected into each of the InGaN well layer and the InAlN barrier layer is determined. Table 1 shows an example.

Preferably, the stress is ε _xx 0.4% to 0.6%, the thickness of the well layer is in the range of 10A to 14A, and the thickness of the barrier layer is in the range of 10A to 20A.

Preferably, when the stress epsilon _xx is in the range of 0.45% to 0.55%, the thickness of the well layer is in the range of 11 ANGSTROM to 13 ANGSTROM, and the thickness of the barrier layer is in the range of 14 ANGSTROM to 16 ANGSTROM. The photodetector is a photodetector that can be applied in the 1.55 [mu] m band.

According to the present invention, it is possible to provide a photodetector having a structure in which tensile strain is applied to a barrier layer in a well layer to prevent strain from being entirely generated even when a quantum well structure of many layers is stacked.

1 is a diagram illustrating an example of a photodetector according to an embodiment of the present invention.
FIGS. 2 to 5 are graphs of computer simulation results for manufacturing a photodetector according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

1 is a diagram illustrating an example of a photodetector according to an embodiment of the present invention.

The photodetector 100 may have a structure in which a substrate 110, a first doping layer 120, a quantum structure 130, and a second doping layer 140 are stacked. In some embodiments, a substrate 110, a first doping layer 120, a quantum structure 130, and a second doping layer 140 are sequentially deposited. The number of the stacked layers in which the barrier layer 130A and the well layer 130B are alternately stacked is not particularly limited and can be variously varied. According to the effect of the present invention, the strain according to the present invention can be reduced, so that the number of the barrier layer and the well layer stacked in the quantum well structure of the present invention can be more effective in a plurality of cases.

 The photodetector 100 may further include a first electrode 160 on the first doping layer 120 and a second electrode 170 on the second doping layer 140, A voltage may be applied to the photodetector 100.

The photodetector of the present invention can be applied to various detector structures such as a horizontal structure and a vertical structure which are not limited to a special structure, but only an example is presented in Fig.

According to the above-described photodetector structure of the present invention, In is added to the well layer 130B and the barrier layer 130A, respectively, so that the strain can be reduced to a desired wavelength (for example, a wavelength band of 1550 nm) Structure can be designed. As a result, we found that the strain is compensated for InGaN (-ε _xx ) / InAlN (+ ε _xx ) quantum well structures. According to this structure, a compressive strain is applied to the well layer 130B, and a tensile strain is applied to the barrier layer 130A, so that a structure can be realized in which a strain is not applied to the whole even if a quantum well structure having a plurality of layers is formed . It has been shown that a design can be made to have a wavelength of 1550 nm even with a small strain, for example, a strain of 0.5%, and presenting the conditions is one of the main points of the present invention.

FIGS. 2 to 5 are graphs of computer simulation results for manufacturing a photodetector according to an embodiment of the present invention.

FIG. 2 is a graph showing changes in ISB transition energy E ₂₁ and wavelengths? ₁₂ as a function of the width of a well layer for a GaN / Al _1-y In _y N (y = 0.185) quantum well structure lattice matched to GaN To FIG. This graph represents the result of computer simulation.

Referring to FIG. 2, E ₂₁ corresponds to the transition energy between two subbands in the conduction band, and the width L _b of the barrier layer is set to 20 Å. Here, 2.914 eV was used as a bowing parameter for the band gap energy of the three element compounds of Al _1-y In _y N. The interband transition energy increases with the width of the well layer and shows the maximum value near L _w = 12 Å. And when the width of the well layer is further increased, the decrease starts as the width of the well layer increases.

The maximum interband transition energy is about 0.618 eV, which corresponds to a 2 탆 transition wavelength. However, this wavelength is larger than 1.55 ㎛ useful for communication applications. Therefore, the interband transition energy was investigated as a function of the width of the barrier layer to determine whether the wavelength can be 1.55 μm in the QW structure lattice matched to GaN.

FIG. 3 is a graph showing changes in ISB transition energy E ₂₁ and wavelengths? ₁₂ as a function of the width of the barrier layer in GaN / Al _1-y In _y N (y = 0.185) quantum well structures lattice-matched to GaN to be. The width L _w of the well layer is set to 12 Å, which corresponds to the shortest wavelength in FIG.

However, even when L _b is 10 Å, the wavelength λ ₁₂ is larger than 1.55 μm. That is, the interband transition energy at L _b = 10 A is 0.78 eV, which corresponds to 1.6 μm.

FIG. 4 is a graph showing the relationship between the ISB transition energy E ₂₁ and the wavelength of the well layer as a function of the strain-compensated In _x Ga _{1 -x} N / Al _{1 -y} In _y N quantum well structure having several strain values. The change of? ₁₂ FIG. ε _xx is the strain tensor.

Here, the width Lb of the barrier layer is set to 20 angstroms as an example. When ε is 0.3, 0.5 and 0.8%, the well has compressive strain and the barrier has tensile strain. The dot line is a guideline for a wavelength of 1.55 μm. Regardless of the strain value, the maximum interband transition energies are observed at a well layer width of 12 ANGSTROM. However, the maximum interband transition energy increases sharply as the strain value increases. For example, for quantum wells with strain values of 0.3% and 0.8%, the maximum ISB transition energy values are 0.706 eV and 0.844 eV, respectively.

As a result, in the strain-compensated quantum well structure having a strain of 0.8%, the wavelength is short enough to 1.55 ㎛ in L _w = 14Å. However, it is desirable to have a quantum well with as small a lattice mismatch as possible, so the interband transition energy is investigated as a function of the barrier layer width.

FIG. 5 is a graph showing the relationship between the ISB transition energy E ₂₁ and the wavelengths λ ₁₂ (λ) of the strain compensated In _x Ga _{1 -x} N / Al _{1 -y} In _y N quantum well structure having several strain values as a function of the width of the barrier layer. As shown in FIG.

The well layer width L _w was set to 12Å as illustrated. When ε is 0.3%, 0.5% and 0.8%, the well layer has compressive strain and the barrier layer has tensile strain. The dot line is a guideline for a wavelength of 1.55 μm.

The interband transition energy increases as the width of the barrier layer decreases. The quantum well structure with a small strain shows a large increase rate of the transition energy as compared with the quantum well structure with a large strain. Therefore, even in the quantum well structure in which 0.3% L _b may be a wavelength of 1.55 ㎛ at 12Å the telecommunication application. It can therefore be expected that the strain compensated quantum well structure is suitable for telecommunication applications with a small strain of 0.3% to 0.5% and a wavelength of 1.55 μm.

Hereinafter, with reference to the experimental results of FIGS. 2 to 5, the present invention considers conditions for fabricating a strain-compensated photodetector at a wavelength of 1.55 μm band.

When ε _xx is determined, the amount of In injected into each of the well layer and the barrier layer can be accurately determined. Therefore, the conditions of ε _xx will be mainly discussed below. According to Table 1, for example, when? _Xx is 0.3%, 0.5%, and 0.8% The In and In quantities of each well layer are shown.

ε _xx In amount of well layer In amount of barrier layer Thickness of Well Barrier thickness 0.3 0.028 0.162 12 Å 12 Å 0.5 0.047 0.142 12 Å 15 Å 0.8 0.076 0.124 12 Å 34 Å

On the other hand, in Table 1, the well layer has a thickness of 12 angstroms. Referring to FIG. 4, a range of 10 angstroms to 14 angstroms may be a preferable condition. If the thickness of the well layer is smaller than 10 angstroms, there is a problem in the manufacturing process or the like. If it is larger than 14 angstroms, it may be difficult to manufacture the photodetector in the 1.55 占 퐉 range.

According to the above-mentioned Table 1 and Fig. 5, the stress? _Xx It was confirmed that a photodetector in the 1.55 탆 range could be fabricated in the range of 0.3% to 0.8%, with appropriate well layer thickness and barrier layer thickness. The stress ε _xx 0.3%, the photodetector in the 1.55 탆 range can be fabricated under the condition that the thickness of the well layer is in the range of 10 Å to 14 Å, and the thickness of the barrier layer is in the range of 10 Å to 12 Å. The thickness of the barrier layer was determined to be about 10 Å by the process margin. The stress ε _xx 0.5%, the photodetector in the 1.55 탆 range can be fabricated under the condition that the thickness of the well layer is in the range of 10 Å to 14 Å and the thickness of the barrier layer is in the range of 12 Å to 18 Å. The stress ε _xx 0.8%, the photodetector in the 1.55 탆 range can be fabricated under the condition that the thickness of the well layer is in the range of 10 Å to 14 Å and the thickness of the barrier layer is in the range of 27 Å to 41 Å. It goes without saying that the stress may have a larger value. Preferably, referring to FIG. 5, it can be seen that the thickness of the barrier layer for producing a photodetector having a 1.55 μm band in the range of 10 Å to 14 Å is present in the case of a stress of less than 2% have.

However, with respect to the preferred range, the stress? _Xx In the range of 0.3% to 0.8%, the photodetector in the 1.55 탆 range can be manufactured in the range of the thickness of the well layer ranging from 10 Å to 14 Å and the thickness of the barrier layer ranging from 10 Å to 37 Å.

With respect to the more preferable range, when the stress ε _xx is 0.4% to 0.6%, the thickness of the well layer is in the range of 10 Å to 14 Å, and the thickness of the barrier layer is in the range of 10 Å to 20 Å. .

According to a further preferable range, the case where the stress? _Xx is 0.5% is judged as the most stable stress condition in the process. When the stress? _Xx is 0.45% to 0.55%, the thickness of the well layer is 11? And the thickness of the barrier layer is in the range of 14 ANGSTROM to 16 ANGSTROM, it is possible to manufacture a photodetector in the 1.55 mu m band.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, but can be variously modified and embodied within the scope of the claims, the detailed description of the invention and the accompanying drawings This also belongs to the present invention.

Claims (4)

1. A photodetector formed on a substrate and comprising an InGaN / InAlN stacked quantum well structure,
Wherein the quantum well structure comprises a stacked structure of at least one alternately stacked well layer and a barrier layer,
In is added to the barrier layer and the well layer,
The stress ε _xx In the range of 0.3% to 0.8%, when the thickness of the well layer is in the range of 10 Å to 14 Å,
Wherein the thickness of the barrier layer ranges from 10 A to 37 A.
The method according to claim 1,
The stress is ε _xx Wherein the thickness of the well layer is in the range of 10 to 14 angstroms and the thickness of the barrier layer is in the range of 10 to 20 angstroms.
The method according to claim 1,
Wherein the thickness of the well layer is in the range of 11 to 13 Angstroms and the thickness of the barrier layer is in the range of 14 to 16 Angstroms when the stress? _Xx is 0.45% to 0.55%.
4. The method according to any one of claims 1 to 3,
Wherein the photodetector is a 1.55-μm band photodetector.

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