Semiconductor light receiving element

Abstract

To provide a semiconductor light receiving element capable of reducing an absolute value of distortion of a group III-V semiconductor layer in a light receiving layer.SOLUTION: An absorption layer provided between the 1III group-V semiconductor layer of the first conductivity type and the 2III group-V semiconductor layer of the second conductivity type in a first direction, the absorption layer including a plurality of unit structures stacked in the first direction, the 1III group-V semiconductor layer of the first conductivity type being provided between the 2III group-V semiconductor layer of the first conductivity type and the well group-V semiconductor layer of the second conductivity type in the first direction, each of the plurality of unit structures includes a first gallium indium arsenide layer, a second gallium indium arsenide layer, and a gallium arsenide antimonide layer, and a gallium composition of the first gallium indium arsenide layer is different from a gallium composition of the second gallium indium arsenide layer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor light receiving element. [Background technology]

[0002] Non-Patent Document 1 discloses a semiconductor photodetector having a light-receiving layer with a type II superlattice. The light-receiving layer includes a gallium arsenide (GaAs) layer, an indium arsenide (InAs) layer, and a gallium arsenide antimonide (GaAsSb) layer. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Takashi Kato, et al, "Optical properties of (GaAs / InAs)-GaAsySb1-y digital alloy superlattices in the short-wavelength infrared region calculated by an sp3d5s*tight-binding method" Applied Physics A, 129 (2023) 129:429 Summary of the Invention [Problem to be solved by the invention]

[0004] When the absorption layer is formed on an indium phosphide (InP) substrate, the strain in the GaAs layer is about +3.8% and the strain in the InAs layer is about -3.1%. The absolute values ​​of the strain in the GaAs layer and the InAs layer are relatively large, exceeding 3%.

[0005] The present disclosure provides a semiconductor light-receiving element capable of reducing the absolute value of strain in a III-V group semiconductor layer in a light-receiving layer. [Means for solving the problem]

[0006] A semiconductor light-receiving element according to one aspect of the present disclosure includes: a first III-V group semiconductor layer of a first conductivity type; a second III-V group semiconductor layer of a second conductivity type; and a light-receiving layer provided in a first direction between the first III-V group semiconductor layer and the second III-V group semiconductor layer, the light-receiving layer including a plurality of unit structures stacked in the first direction, each of the plurality of unit structures including a first gallium indium arsenide layer, a second gallium indium arsenide layer, and a gallium arsenide antimony layer, and the first gallium indium arsenide layer has a gallium composition different from the gallium composition of the second gallium indium arsenide layer. [Effects of the Invention]

[0007] According to the present disclosure, a semiconductor light-receiving element is provided that can reduce the absolute value of strain in the III-V group semiconductor layer in the light-receiving layer. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a semiconductor light-receiving element according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a light-receiving layer included in the semiconductor light-receiving element of FIG. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a unit structure included in the absorption layer of FIG. [Figure 4] FIG. 4 is a cross-sectional view schematically showing a unit structure according to another example. [Figure 5] FIG. 5 is a cross-sectional view schematically showing a unit structure according to another example. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a unit structure according to another example. [Figure 7] FIG. 7 is a cross-sectional view schematically showing a light receiving layer according to another example. [Figure 8] FIG. 8 is a graph showing an example of the range of composition v and composition w. [Figure 9] FIG. 9 is a graph showing an example of a quantum efficiency spectrum. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A semiconductor light-receiving element includes a first III-V semiconductor layer of a first conductivity type, a second III-V semiconductor layer of a second conductivity type, and a light-receiving layer provided in a first direction between the first III-V semiconductor layer and the second III-V semiconductor layer, the light-receiving layer including a plurality of unit structures stacked in the first direction, each of the plurality of unit structures including a first gallium indium arsenide layer, a second gallium indium arsenide layer, and a gallium arsenide antimony layer, and the gallium composition of the first gallium indium arsenide layer is different from the gallium composition of the second gallium indium arsenide layer.

[0011] According to the semiconductor light-receiving element, the absolute value of the strain in each of the first gallium indium arsenide layer and the second gallium indium arsenide layer can be reduced compared to the gallium arsenide layer and the indium arsenide layer.

[0012] (2) In the above (1), the absolute value of the strain in each of the first gallium indium arsenide layer and the second gallium indium arsenide layer may be 1 to 3%.

[0013] When the absolute value of the strain is 1% or more, the band gap wavelength of the absorption layer can be prevented from becoming too small.

[0014] (3) In the above (1) or (2), the gallium composition of the first gallium indium arsenide layer may be 0.02 to 0.32.

[0015] (4) In any one of the above (1) to (3), the gallium composition of the second gallium indium arsenide layer may be 0.61 to 0.89.

[0016] (5) In any one of (1) to (4) above, when the gallium composition of the first gallium indium arsenide layer is w and the gallium composition of the second gallium indium arsenide layer is v, w≧−2.14v+1.48 may be satisfied.

[0017] (6) In any one of (1) to (5) above, when the gallium composition of the first gallium indium arsenide layer is w and the gallium composition of the second gallium indium arsenide layer is v, w≦−0.72v+0.81 may be satisfied.

[0018] (7) In any one of the above (1) to (6), the ratio of the thickness of the first gallium indium arsenide layer to the thickness of the second gallium indium arsenide layer may be 0.5 to 1.5.

[0019] (8) In any one of (1) to (7) above, the semiconductor light receiving element may further include an indium phosphide substrate, and in the first direction, the first III-V semiconductor layer may be provided between the indium phosphide substrate and the light receiving layer.

[0020] [Details of the embodiments of the present disclosure] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0021] FIG. 1 is a cross-sectional view schematically illustrating a semiconductor light-receiving element according to one embodiment. The semiconductor light-receiving element 10 illustrated in FIG. 1 includes a first III-V semiconductor layer 12 of a first conductivity type, a second III-V semiconductor layer 14 of a second conductivity type, and a light-receiving layer 16. The first conductivity type is, for example, n-type. The second conductivity type is opposite to the first conductivity type. The second conductivity type is, for example, p-type. The light-receiving layer 16 is undoped. The semiconductor light-receiving element 10 is, for example, a photodiode. The light-receiving layer 16 is disposed between the first III-V semiconductor layer 12 and the second III-V semiconductor layer 14 in a first direction D1. The first direction D1 is the thickness direction of the light-receiving layer 16. The first direction D1 may be a direction from the first III-V semiconductor layer 12 toward the second III-V semiconductor layer 14. The first direction D1 may be a crystal growth direction. Alternatively, the first direction D1 may be a direction from the second III-V semiconductor layer 14 toward the first III-V semiconductor layer 12. The first direction D1 may be a direction opposite to the crystal growth direction.

[0022] The first III-V semiconductor layer 12 may be an indium phosphide (InP) layer. The dopant concentration in the first III-V semiconductor layer 12 is 1×10 23 From 1×10 24 m -3 The first III-V semiconductor layer 12 may have a thickness of 0.1 to 1 μm. Examples of n-type dopants include silicon (Si), tellurium (Te), and tin (Sn).

[0023] The second III-V semiconductor layer 14 may be an InP layer. The dopant concentration in the second III-V semiconductor layer 14 is 1×10 23 From 1×10 24 m -3 The second III-V semiconductor layer 14 may have a thickness of 0.1 to 1 μm. Examples of p-type dopants include zinc (Zn) and beryllium (Be).

[0024] The semiconductor light-receiving device 10 may further include a substrate 18. The substrate 18 may be a III-V semiconductor substrate such as an InP substrate. The substrate 18 may be a semi-insulating substrate. The first III-V semiconductor layer 12 may be provided between the substrate 18 and the light-receiving layer 16 in the first direction D1. The first III-V semiconductor layer 12 may be provided on a primary surface of the substrate 18. The primary surface of the substrate 18 may be a (100) plane. The primary surface of the substrate 18 may be perpendicular to the first direction D1.

[0025] The semiconductor light receiving element 10 may further include a first conductivity type III-V semiconductor layer 20. The III-V semiconductor layer 20 is provided between the first III-V semiconductor layer 12 and the substrate 18 in the first direction D1. The III-V semiconductor layer 20 may be a contact layer. The III-V semiconductor layer 20 may be an InP layer. An electrode 30 may be connected to the III-V semiconductor layer 20.

[0026] The semiconductor light receiving element 10 may further include a second conductivity type III-V group semiconductor layer 22. In the first direction D1, the second III-V group semiconductor layer 14 is provided between the III-V group semiconductor layer 22 and the light receiving layer 16. The III-V group semiconductor layer 22 may be a contact layer. The III-V group semiconductor layer 22 is Ga z In 1-z It may be an As layer (also called a GaInAs layer). z is the gallium (Ga) composition. z is greater than 0 and less than 1. An electrode 40 may be connected to the III-V semiconductor layer 22.

[0027] The semiconductor light receiving element 10 can detect incident light L. The incident light L may be visible light or infrared light having a wavelength of 0.4 to 3 μm. The incident light L may travel in a first direction D1. The incident light L may pass through the substrate 18 and enter the light receiving layer 16. The semiconductor light receiving element 10 may be used in a spectroscopy system, an imaging system, or an optical communication system of a gas analyzer.

[0028] 2 is a cross-sectional view schematically illustrating a light-receiving layer included in the semiconductor light-receiving element of FIG. 1. As illustrated in FIG. 2, the light-receiving layer 16 includes a plurality of unit structures U1 stacked in a first direction D1. Adjacent unit structures U1 may be in contact with each other. The number of unit structures U1 may be 100 to 500. The plurality of unit structures U1 form a superlattice.

[0029] 3 is a cross-sectional view schematically illustrating a unit structure included in the absorption layer of FIG. 2. As shown in FIG. 3, each unit structure U1 is made of gallium arsenide antimonide (GaAs y Sb 1-y ) layer L1 (hereinafter simply referred to as layer L1) and a first gallium indium arsenide (Ga w In 1-w As) layer L2 (hereinafter simply referred to as layer L2) and a second gallium indium arsenide (Ga v In 1-v The layer L1 includes an arsenic (As) layer L3 (hereinafter simply referred to as layer L3). y is the arsenic (As) composition. y is greater than 0 and less than 1. y may be 0.45 to 0.6. In this case, layer L1 can be lattice-matched to the InP layer. v and w are gallium (Ga) compositions. v and w are greater than 0 and less than 1. The gallium composition v of layer L3 is different from the gallium composition w of layer L2. The gallium composition v of layer L3 may be greater than the gallium composition w of layer L2. The gallium composition v of layer L3 may be greater than 0.47. The gallium composition v of layer L3 may be 0.61 to 0.89. The gallium composition w of layer L2 may be less than 0.47. The gallium composition w of layer L2 may be 0.02 to 0.32. The absolute value of the strain in each of layers L2 and L3 may be 1 to 3%.

[0030] The layers L1, L2, and L3 may be stacked in the first direction D1. The layers L1, L2, and L3 may be stacked in this order in the first direction D1. That is, the layer L2 may be disposed between the layer L1 and the layer L3 in the first direction D1. Each unit structure U1 may include multiple layers L2 and multiple layers L3. The multiple layers L2 and multiple layers L3 may be stacked on the layer L1 so that the layers L2 and L3 are alternately arranged. The layer L2 may contact the adjacent layer L3. The layer L1 may contact the adjacent layer L2. The layer L3 located at the end of one unit structure U1 in the first direction D1 may contact the layer L1 in the adjacent unit structure U1. The layer L1 may function as an electron barrier layer or a hole well layer. The layers L2 and L3 may function as electron well layers or hole barrier layers.

[0031] In each unit structure U1, the number of pairs including a single layer L2 and a single layer L3 is k. k may be 1 to 10. k may be 2 or greater. As shown in FIG. 3 , in each of the k pairs on the layer L1, the layer L2 and the layer L3 may be stacked in this order in the first direction D1.

[0032] Layers L2 and L3 may have thicknesses smaller than layer L1. The thickness of layer L2 may be the same as or different from the thickness of layer L3. The thickness of layer L1 may be 2.5 to 6.3 nm. The thickness of layer L2 may be 0.2 to 2.4 nm. The thickness of layer L3 may be 0.2 to 2.4 nm. The ratio of the thickness tw of layer L2 to the thickness tv of layer L3 may be 0.5 to 1.5. When one unit structure U1 includes multiple layers L3, the thickness tv of the multiple layers L3 is the total thickness of the multiple layers L3. When one unit structure U1 includes multiple layers L2, the thickness tw of the multiple layers L2 is the total thickness of the multiple layers L2. The thicknesses of the layers L2 within the unit structure U1 may be the same or different. The thicknesses of the layers L3 within the unit structure U1 may be the same or different.

[0033] FIG. 4 is a cross-sectional view schematically illustrating another example of a unit structure. The light-receiving layer 16 in FIG. 2 may include a unit structure U1a shown in FIG. 4 instead of the unit structure U1 in FIG. 3. The unit structure U1a is the same as the unit structure U1 except that the positions of the layers L2 and L3 are interchanged and a layer L3 is further included at the upper end in the first direction D1. In the unit structure U1a, the layers L1, L3, and L2 are stacked in this order in the first direction D1. That is, the layer L3 is provided between the layers L1 and L2 in the first direction D1.

[0034] FIG. 5 is a cross-sectional view schematically illustrating another example of a unit structure. The light-receiving layer 16 of FIG. 2 may include a unit structure U1b shown in FIG. 5 instead of the unit structure U1 of FIG. 3. The unit structure U1b is the same as the unit structure U1 except that the stacking order in the first direction D1 is reversed. In the unit structure U1b, the layer L3, the layer L2, and the layer L1 are stacked in this order in the first direction D1. That is, the layer L2 is provided between the layer L3 and the layer L1 in the first direction D1.

[0035] FIG. 6 is a cross-sectional view schematically illustrating another example of a unit structure. The light-receiving layer 16 of FIG. 2 may include a unit structure U1c shown in FIG. 6 instead of the unit structure U1 of FIG. 3. The unit structure U1c is the same as the unit structure U1b except that the positions of the layers L2 and L3 are interchanged and the unit structure U1c further includes a layer L3 at the lower end in the first direction D1. In the unit structure U1c, the layers L2, L3, and L1 are stacked in this order in the first direction D1. That is, the layer L3 is provided between the layers L2 and L1 in the first direction D1.

[0036] 7 is a cross-sectional view schematically illustrating another example of an absorption layer. The absorption layer 16a in FIG. 7 is the same as the absorption layer 16 in FIG. 2 except that it further includes a III-V group semiconductor layer L4. The III-V group semiconductor layer L4 is disposed between the unit structure U1 and the second III-V group semiconductor layer 14. The III-V group semiconductor layer L4 is GaAs y Sb 1-yWhen the absorption layer 16a of FIG. 7 includes a unit structure U1a instead of the unit structure U1, the III-V group semiconductor layer L4 may be GaAs y Sb 1-y 7 includes a unit structure U1b or U1c instead of the unit structure U1, the III-V group semiconductor layer L4 may be the same as the layer L1. v In 1-v It may be the same as the As layer L3.

[0037] FIG. 8 is a graph showing an example of the range of composition v and composition w. In FIG. 8, the line LN1 is represented by w = -2.14v + 1.48. The line LN2 is represented by w = -1.57v + 1.22. The line LN3 is represented by w = -1.08v + 0.98. The line LN4 is represented by w = -0.83v + 0.87. The line LN5 is represented by w = -0.72v + 0.81. The line LN1 shows the relationship between composition v and composition w when the ratio of the thickness tw of layer L2 to the thickness tv of layer L3 is 0.5. The line LN2 shows the relationship between composition v and composition w when the ratio of the thickness tw of layer L2 to the thickness tv of layer L3 is 0.7. The line LN3 shows the relationship between composition v and composition w when the ratio of the thickness tw of layer L2 to the thickness tv of layer L3 is 1. Line LN4 shows the relationship between composition v and composition w when the ratio of the thickness tw of layer L2 to the thickness tv of layer L3 is 1.3. Line LN5 shows the relationship between composition v and composition w when the ratio of the thickness tw of layer L2 to the thickness tv of layer L3 is 1.5.

[0038] 8, the gallium composition w of layer L2 may be 0.02 to 0.32. The gallium composition v of layer L3 may be 0.61 to 0.89. The following formulas (1) and (2) may also be satisfied: In each formula, w is the gallium composition of layer L2, and v is the gallium composition of layer L3. w≧-2.14v+1.48 … (1) w≦-0.72v+0.81 … (2)

[0039] In region A enclosed by the solid lines (six straight lines) in FIG. 8, when the ratio of the thickness tw of layer L2 to the thickness tv of layer L3 is 0.5 to 1.5, the absolute value of the strain in each of layers L2 and L3 can be 1 to 3%. For example, when the gallium composition w of layer L2 is 0.32 and the gallium composition v of layer L3 is 0.61, the absolute value of the strain in each of layers L2 and L3 is 1%. When the gallium composition w of layer L2 is 0.02 and the gallium composition v of layer L3 is 0.89, the absolute value of the strain in each of layers L2 and L3 is 3%. When the absolute value of the strain in each of layers L2 and L3 is 1% or more, the bandgap wavelength λg can be 2.3 μm or more. When the absolute value of the strain in each of layers L2 and L3 is 3% or less, the bandgap wavelength λg can be 2.5 μm or less.

[0040] In each unit structure U1, the average strain εSL of the layers L2 and L3 is calculated from the following formula (3). εSL=((as-av) / av×tv+(as-aw) / aw×tw) / (tv+tw) …(3)

[0041] In equation (3), as is the lattice constant of InP in a free state without strain. av is the lattice constant of Ga in a free state without strain. v In 1-v is the lattice constant of As. aw is the Ga w In 1-w is the lattice constant of As. tv is the Ga v In 1-v is the total thickness of the As layer L3. tw is the Ga w In 1-w This is the total thickness of the As layer L2.

[0042] Since the strain in the layer L2 is negative and the strain in the layer L3 is positive, the strains in the layer L2 and L3 cancel each other out, making it possible to make the average strain εSL approach 0. y Sb 1-yBy adjusting the arsenic composition y of the layer L1, the average strain εT2SL of each unit structure U1 can be set to 0. The average strain εT2SL is calculated by the following formula (4). εT2SL=((as-av) / av×tv+(as-aw) / aw×tw+(as-ay) / ay×ty) / (tv+tw+ty) …(4)

[0043] In equation (4), ay is GaAs in a free state without strain. y Sb 1-y ty is the lattice constant of GaAs in one unit structure U1. y Sb 1-y is the thickness of layer L1. The rest is the same as equation (3).

[0044] According to the semiconductor light receiving element 10, the absolute value of the strain in each of the layers L2 and L3 can be reduced. The absolute value of the strain in each of the layers L2 and L3 is, for example, 3% or less. As a result, the rate of occurrence of lattice defects due to strain can be reduced, and an increase in dark current in the semiconductor light receiving element 10 can be prevented.

[0045] Hereinafter, various experiments will be described that were conducted to evaluate the unit structure U1a of Fig. 4. The experiments described below do not limit the present disclosure.

[0046] (First experiment) In the unit structure U1a according to the first experiment, the absolute value of the strain in each of the layers L2 and L3 is 0%.

[0047] (Second experiment) In the unit structure U1a according to the second experiment, the absolute value of the strain in each of the layers L2 and L3 is 1%.

[0048] (Third experiment) In the unit structure U1a according to the third experiment, the absolute value of the strain in each of the layers L2 and L3 is 1.5%.

[0049] (Experiment 4) In the unit structure U1a according to the fourth experiment, the absolute value of the strain in each of the layers L2 and L3 is 2%.

[0050] (5th experiment) In the unit structure U1a according to the fifth experiment, the absolute value of the strain in each of the layers L2 and L3 is 2.5%.

[0051] (Experiment 6) In the unit structure U1a according to the sixth experiment, the absolute value of the strain in each of the layers L2 and L3 is 3%.

[0052] (Experiment 7) The unit structure according to the seventh experiment includes a GaAs layer and an InAs layer instead of the layer L2 and the layer L3 of the unit structure U1a.

[0053] (Quantum efficiency spectrum) The quantum efficiency spectra were calculated by simulation for the unit structures of Experiments 1 to 7. The temperature T was 250 K. The results are shown in Figure 9.

[0054] In FIG. 9, spectrum E1 shows the results of the first experiment. spectrum E2 shows the results of the second experiment. spectrum E3 shows the results of the third experiment. spectrum E4 shows the results of the fourth experiment. spectrum E5 shows the results of the fifth experiment. spectrum E6 shows the results of the sixth experiment. spectrum E7 shows the results of the seventh experiment. It can be seen that the absorption edge wavelength increases as the absolute value of the strain in layers L2 and L3 increases.

[0055] Although the preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments.

[0056] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0057] 10...Semiconductor light receiving element 12...First III-V semiconductor layer 14...Second III-V group semiconductor layer 16...Light-receiving layer 16a...Light-receiving layer 18... Circuit board 20...III-V group semiconductor layer 22...III-V semiconductor layer 30...electrode 40...Electrode A…Area D1…first direction E1...spectrum E2...spectrum E3...spectrum E4...Spectrum E5...Spectrum E6...Spectrum E7...Spectrum L…Incoming light L1...GaAs y Sb 1-y layer L2…Ga w In 1-w As layer L3…Ga v In 1-v As layer L4: III-V semiconductor layer LN1…straight line LN2: Straight line LN3…straight line LN4: Straight line LN5…straight line U1...Unit structure U1a...Unit structure U1b...Unit structure U1c...Unit structure

Claims

1. a first group III-V semiconductor layer of a first conductivity type; a second group III-V semiconductor layer of a second conductivity type; a light-receiving layer provided between the first group III-V semiconductor layer and the second group III-V semiconductor layer in a first direction; Equipped with the light receiving layer includes a plurality of unit structures stacked in the first direction, each of the plurality of unit structures includes a first gallium indium arsenide layer, a second gallium indium arsenide layer, and a gallium arsenide antimony layer; a gallium composition of the first gallium indium arsenide layer different from a gallium composition of the second gallium indium arsenide layer;

2. 2. The semiconductor light-receiving element according to claim 1, wherein the absolute value of the strain in each of said first gallium indium arsenide layer and said second gallium indium arsenide layer is 1 to 3%.

3. 3. The semiconductor light-receiving element according to claim 1, wherein the gallium composition of said first gallium indium arsenide layer is from 0.02 to 0.

32.

4. 3. The semiconductor light-receiving element according to claim 1, wherein the second gallium indium arsenide layer has a gallium composition of 0.61 to 0.

89.

5. 3. The semiconductor light-receiving element according to claim 1, wherein, when the gallium composition of said first gallium indium arsenide layer is w and the gallium composition of said second gallium indium arsenide layer is v, w≧−2.14v+1.48 is satisfied.

6. 3. The semiconductor light-receiving element according to claim 1, wherein, when the gallium composition of said first gallium indium arsenide layer is w and the gallium composition of said second gallium indium arsenide layer is v, w≦−0.72v+0.81 is satisfied.

7. 3. The semiconductor light-receiving element according to claim 1, wherein a ratio of the thickness of said first GaInAs layer to the thickness of said second GaInAs layer is 0.5 to 1.

5.

8. Further comprising an indium phosphide substrate, 3. The semiconductor light-receiving element according to claim 1, wherein the first III-V semiconductor layer is provided between the indium phosphide substrate and the light-receiving layer in the first direction.

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