Photo-detection element

Abstract

To provide a light detection element having excellent manufacturing quality to prevent an excessive dark current from occurring.SOLUTION: A light detection element includes a base plate 2, a correction layer 3 laminated on the base plate 2, a buffer layer 4 laminated on the correction layer 3, a composite layer 5 composed of a plurality of sublayers 51 and laminated on the buffer layer 4, a functional layer 6l laminated on the composite layer 5, and an absorption layer 7 laminated on the functional layer 6, is made of the same material as the base plate 2 in the case where a fourth support layer in the correction layer 3 is laminated such to make the fourth support layer adjacent to the base plate 2, and is made of the same material as the buffer layer 4 in the case of being laminated so as to be adjacent to the buffer layer 4, and the lattice constants of each sub layer 51 constituting the composite layer 5 are each larger than a first numerical value and smaller than a second numerical value when the lattice constant of the base plate 2 is regarded as a first numerical value and the lattice constant of the function layer 6 is regarded as a second numerical value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a semiconductor device, and more particularly to a photosensing element.

Background Art

[0002] FIG. 1 shows an example of a conventional photosensing element. The illustrated photosensing element 1 is formed by molecular beam epitaxial growth, and includes a substrate 11, a buffer layer 12 formed on the substrate 11, a quantum well layer 13 formed in the buffer layer 12 to block light and generate a signal, an absorption layer 14 formed in the quantum well layer 13 to absorb light, and a window layer 15 formed in the absorption layer 14 to limit the range in which light enters, in this order.

[0003] When this photosensing element 1 operates, light entering from the range restricted by the window layer 15 is absorbed by the absorption layer 14, and when a corresponding electrical signal is formed in the quantum well layer 13 by the energy of the light absorbed by the absorption layer 14, the function of detecting light can be exhibited by calculating the energy of the light based on this signal.

[0004] The buffer layer 12 formed between the substrate 11 and the quantum well layer 13 mainly uses a material similar to that of the substrate 11. Specifically, when an n+-doped gallium arsenide (GaAs) material is used as the substrate 11, if an N-type doped gallium arsenide (GaAs) material is used as the buffer layer 12, when the quantum well layer 13, which is significantly different in material from the substrate 11, is formed by epitaxial growth, the buffer layer 12 can exert a buffering effect between the substrate 11 and the quantum well layer 13.

[0005] However, if the difference in the lattice constants of the respective layers constituting such a photodetector element 1 is large, a situation may occur where the lattice constants cannot be matched even with the provision of the buffer layer 12, and internal stress will be continuously accumulated when the respective layers are stacked by epitaxial growth. If the accumulated internal stress is too high, large or small defects will occur in each layer, and when the photodetector element 1 having such defects operates, a dark current that affects the detection result (the electrical signal generated in the quantum well layer 13) will be generated. In some cases, it may become a defective product that exceeds the error standard of the detection function.

[0006] In addition, as basic knowledge regarding the configuration of conventional photodetector elements, for example, Patent Document 1 can also be referred to.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In view of the problems of the above prior art, an object of the present invention is to provide a photodetector element having excellent manufacturing quality and not generating excessive dark current.

Means for Solving the Problems

[0009] To achieve the above object, the present invention provides an optical detection element including a substrate, a correction layer laminated on the substrate, a buffer layer formed of a gallium arsenide (GaAs) material and laminated on the correction layer, a composite layer composed of a plurality of sublayers laminated on the buffer layer, a functional layer laminated on the composite layer, and an absorption layer laminated on the functional layer. The correction layer includes a first support layer, a second support layer, and a third support layer laminated in order from the substrate side to the buffer layer side, and a fourth support layer laminated between the substrate and the first support layer or between the buffer layer and the third support layer. The first support layer is made of an indium gallium phosphide (InGaP) material, the second support layer is made of an aluminum gallium arsenide (AlxGa1-xAs) material, the third support layer is made of an indium gallium arsenide (InGaAs) material, and the fourth support layer is made of gallium arsenide (GaAs). Further, when the lattice constant of the substrate is a first numerical value and the lattice constant of the functional layer is a second numerical value, the lattice constant of each of the sublayers constituting the composite layer is greater than the first numerical value and less than the second numerical value.

Advantages of the Invention

[0010] With the above configuration, in the present invention, since the correction layer is composed of the first to fourth support layers using materials having appropriate lattice constants respectively, an effective supporting effect can be exerted between the substrate and the buffer layer, and internal stress is less likely to accumulate between the substrate and the buffer layer during the epitaxial growth process, so that the effect of less occurrence of defects caused by internal stress can be obtained. Therefore, high production quality can be ensured, and the generation of dark current that affects the detection result during actual operation can also be suppressed, so that excellent detection performance can be exhibited.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

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Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0012] Hereinafter, each embodiment of the light detection element of the present invention will be described in detail with reference to the drawings.

[0013] First, FIG. 2 shows the configuration of the first embodiment of the light detection element of the present invention. As shown in the figure, this first embodiment includes a substrate 2 made of n+-type gallium arsenide (GaAs), a correction layer 3 laminated on the substrate 2, a buffer layer 4 made of N-type gallium arsenide (GaAs) and laminated on the correction layer 3, a composite layer 5 composed of a plurality of sublayers 51 laminated on the buffer layer 4, a functional layer 6 laminated on the composite layer 5, an absorption layer 7 laminated on the functional layer 6, at least one light entrance 80 is formed, and a window layer 8 laminated on the absorption layer 7 with indium gallium phosphide (InGaP) material.

[0014] FIG. 3 is an explanatory diagram showing the configuration of the correction layer 3 in this first embodiment. As shown in FIGS. 2 and 3, the correction layer 3 in this first embodiment includes a first support layer 31, a second support layer 32, and a third support layer 33 that are sequentially stacked from the substrate 2 side to the buffer layer 4 side, and a fourth support layer 30 that is stacked between the buffer layer 4 and the third support layer 33.

[0015] In the present invention, the first support layer 31 is made of indium gallium phosphide (InGaP) material, the second support layer 32 is made of aluminum gallium arsenide (AlxGa1-xAs) material 32, and the third support layer 33 is made of indium gallium arsenide (InGaAs) material.

[0016] Also, in this embodiment, the fourth support layer 30 is made of N-type gallium arsenide (GaAs), which is the same material as the buffer layer 4.

[0017] Therefore, in this embodiment, the correction layer 3 is composed of the first support layer 31 made of indium gallium phosphide (InGaP) material, the second support layer 32 made of aluminum gallium arsenide (AlxGa1-xAs) material 32, the third support layer 33 made of indium gallium arsenide (InGaAs) material, and the fourth support layer 30 made of N-type gallium arsenide (GaAs). Since these first support layer 31 to fourth support layer 30 have appropriate lattice constants, they can exert an effective supporting effect between the substrate 2 and the buffer layer 4, and internal stress is less likely to accumulate between the substrate 2 and the buffer layer 4 during the epitaxial growth process, so the effect that defects caused by internal stress are also less likely to occur can be obtained. Therefore, high production quality can be ensured, and the generation of dark current that affects the detection result can also be suppressed during actual operation, so excellent detection performance can also be exhibited.

[0018] Also, regarding the plurality of sub-layers 51 that make up the composite layer 5, in this embodiment, they are made using indium gallium arsenide (InGaAs) or indium gallium phosphide (InGaP). If the lattice constant of the substrate 2 is taken as the first numerical value and the lattice constant of the functional layer 6 is taken as the second numerical value, then by using the above materials, the lattice constant of each sub-layer 51 that makes up the composite layer 5 is larger than the first numerical value and smaller than the second numerical value. Furthermore, by configuring the plurality of sub-layers 51 that make up the composite layer 5 such that the lattice constant increases as approaching from the buffer layer 4 side to the functional layer 6 side, it is possible to suppress the accumulation of internal stress during epitaxial growth due to a configuration where the change in lattice constant between the buffer layer 4 and the functional layer 6 is too large, and further avoid the generation of defects caused by internal stress.

[0019] FIG. 4 is a graph showing the generation status of dark current of the first embodiment of the photodetector of the present invention and a comparative example. Referring also to FIGS. 2 and 3, in the measured results for two samples (Sample 1, Sample 2) created based on the first embodiment of the present invention and a sample of the comparative example created without the correction layer 3 of the present invention, the measured values of the dark current generated during operation of the samples (Sample 1, Sample 2) of this first embodiment are 6.3E-09 and 5.7E-09 respectively, while the measured value of the comparative example is 3.1E-08. Therefore, it can be seen that the dark current generated in the samples (Sample 1, Sample 2) of this first embodiment is suppressed. Thus, it is shown that this first embodiment can exhibit an effect that is superior to the comparative example in terms of the performance of suppressing the generation of dark current.

[0020] FIG. 5 is a graph showing the optical detection performance of the first embodiment of the optical detection element of the present invention and a comparative example. As shown in the figure, in the actual measurement results for two samples (Sample 1, Sample 2) created based on the first embodiment of the present invention and a sample of the comparative example created without the correction layer 3 of the present invention, the numerical value of the light reception sensitivity (responsivity, generated current / incident light intensity) for light with a wavelength of 1130 nm is 0.585 A / W for the two samples created based on the first embodiment of the present invention and 0.586 A / W for the sample of the comparative example. Therefore, it can be seen that both have equivalent performance.

[0021] Therefore, from the above actual measurement results, the sample of the first embodiment having the correction layer 3 of the present invention has equivalent performance compared to the sample of the comparative example without the correction layer 3, and the generation of dark current is suppressed. Therefore, it is possible to suppress the generation of defects during epitaxial growth and ensure high production quality. Also, since dark current that affects the detection result is less likely to occur during actual operation, it has been found that it can be expected to exhibit detection performance superior to the conventional one.

[0022] FIG. 6 shows the second embodiment of the optical detection element of the present invention. Referring to FIG. 2 in combination, the difference between this second embodiment and the first embodiment is that the fourth support layer 30 in the correction layer 3 is disposed between the first support layer 31 and the substrate 2, and is composed of N-type gallium arsenide (GaAs), a material corresponding to the substrate 2 made of n+-type gallium arsenide (GaAs). As shown in FIG. 7, when two samples (Sample 1, Sample 2) created as this second embodiment were operated, the dark currents measured during operation were 1.6E-08 and 8.6E-09 respectively, which are lower than the dark current measured from the comparative example shown in FIG. 4. Therefore, it can be seen that even with the configuration in which the fourth support layer 30 is disposed between the first support layer 31 and the substrate 2 in this second embodiment, results equivalent to those of the first embodiment can be obtained.

[0023] In summary, the photosensing element of the present invention has a correction layer 3 composed of the first to fourth support layers using materials having appropriate lattice constants respectively. Therefore, it can exert an effective supporting effect between the substrate 2 and the buffer layer 4, and it is difficult for internal stress to accumulate between the substrate 2 and the buffer layer 4 during the process of epitaxial growth, so that the effect of hardly generating defects caused by internal stress can be obtained. Therefore, high production quality can be ensured, and the generation of dark current that affects the detection result can also be suppressed during actual operation. Thus, excellent detection performance can be demonstrated, and the object of the present invention can be surely achieved.

[0024] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited thereto, and various modifications are possible without departing from the gist thereof.

Explanation of Reference Numerals

[0025] 2 Substrate 3 Correction layer 30 Fourth support layer 31 First support layer 32 Second support layer 33 Third support layer 4 Buffer layer 5 Composite layer 51 Sub-layer 6 Functional layer 7 Absorption layer 8 Window layer 80 Light entrance

Claims

1. A substrate, A correction layer laminated on the substrate, A buffer layer formed of a gallium arsenide (GaAs) material and laminated on the correction layer, A composite layer composed of a plurality of sublayers laminated on the buffer layer, A functional layer laminated on the composite layer, An absorption layer laminated on the functional layer, and a photodetector element comprising: The correction layer includes a first support layer, a second support layer, and a third support layer laminated in order from the substrate side to the buffer layer side, and a fourth support layer laminated between the substrate and the first support layer or between the buffer layer and the third support layer. The first support layer is made of an indium gallium phosphide (InGaP) material, the second support layer is made of an aluminum gallium arsenide (AlxGa1-xAs) material, the third support layer is made of an indium gallium arsenide (InGaAs) material, and the fourth support layer is made of gallium arsenide (GaAs). The constituent material of the substrate is n+-type gallium arsenide (GaAs), and the constituent material of the buffer layer is N-type gallium arsenide (GaAs). Furthermore, when the lattice constant of the substrate is a first numerical value and the lattice constant of the functional layer is a second numerical value, the lattice constant of each of the sublayers constituting the composite layer is greater than the first numerical value and less than the second numerical value. A photodetector element characterized by this.

2. The photodetector element according to claim 1, wherein the composite layer is made of an indium gallium arsenide (InGaAs) material.

3. The photodetector element according to claim 1, wherein the composite layer is made of an indium gallium phosphide (InGaP) material.

4. The photodetector element according to claim 2 or claim 3, wherein the lattice constant of each of the sublayers constituting the composite layer increases from the substrate side to the absorption layer side.

5. The photodetector element according to claim 1, further comprising a window layer laminated on the absorption layer and having at least one light entrance formed therein.

6. The photodetector element according to claim 5, wherein the window layer is made of an indium gallium phosphide (InGaP) material.

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