Semiconductor device
By introducing multiple alternating undoped diffusion prevention layers into a semiconductor laser, the problem of laser and electrical property degradation caused by dopant diffusion is solved, and better laser and electrical property stability is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- MITSUBISHI ELECTRIC CORP
- Filing Date
- 2023-12-26
- Publication Date
- 2026-07-24
AI Technical Summary
In the prior art, the diffusion of dopants from the p-type coating layer to the active layer leads to the degradation of laser and electrical properties, and existing prevention measures are not effective enough.
Multiple alternating undoped diffusion prevention layers are introduced between the p-type coating layer and the active layer to form multiple heterogeneous interfaces to prevent dopant diffusion. The specific structure includes at least two undoped layers with different compositions, preferably using materials such as InP and AlInAs.
It effectively suppresses the diffusion of dopants into the active layer, improves the stability of laser and electrical properties, and reduces the risk of laser property degradation.
Smart Images
Figure CN122459980A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to semiconductor devices. Background Technology
[0002] In semiconductor lasers, light amplification occurs within the active layer. The active layer is typically composed of undoped compound semiconductors such as InGaAsP. Light is generated by injecting electrons and holes into the active layer and amplified to be emitted as a laser beam. P-type and n-type cladding layers are formed above and below the active layer. These cladding layers sandwich the active layer from above and below, forming a laser diode that confines the light within the active layer.
[0003] In such semiconductor lasers, dopants injected into the p-type cladding layer can sometimes diffuse into the active layer. If dopants diffuse into the active layer, it will lead to a deterioration in both the laser's characteristics and its electrical properties.
[0004] In the semiconductor laser element described in Patent Document 1, an undoped semiconductor layer is formed between the p-type cladding layer and the active layer to prevent the diffusion of Zn, a dopant used as a p-type cladding layer, into the active layer. This undoped semiconductor layer prevents the diffusion of dopant into the active layer, thus suppressing the degradation of laser characteristics and electrical properties.
[0005] Patent Document 1: Japanese Patent Application Publication No. 4-320027
[0006] However, the semiconductor laser element described in Patent Document 1 has the problem that it is not effective enough in preventing the diffusion of dopants from the p-type cladding layer into the active layer. Generally, dopants tend to exist locally near heterojunctions. In the semiconductor laser element described in Patent Document 1, since the number of interfaces increased by inserting an undoped semiconductor layer is only one, the effect of preventing dopant diffusion is limited. Summary of the Invention
[0007] This disclosure was made to solve the above-mentioned problems, and its purpose is to obtain a semiconductor device that effectively prevents the diffusion of dopants from the p-type coating layer into the active layer.
[0008] The semiconductor device disclosed herein includes: an n-type cladding layer, an active layer formed on the n-type cladding layer, a diffusion prevention layer formed on the active layer and consisting of two or more undoped layers that are different from the adjacent layers above and below, stacked in the vertical direction, and a p-type cladding layer formed on the diffusion prevention layer.
[0009] According to this disclosure, a semiconductor device with good effect in preventing the diffusion of dopants from the p-type cladding layer into the active layer can be obtained. Attached Figure Description
[0010] Figure 1 This is a cross-sectional view of the semiconductor device according to Embodiment 1.
[0011] Figure 2 This is a diagram showing the layer structure of the diffusion-prevention layer.
[0012] Figure 3 This is a diagram illustrating a method for manufacturing a semiconductor device according to Embodiment 1.
[0013] Figure 4 This is a diagram illustrating a method for manufacturing a semiconductor device according to Embodiment 1.
[0014] Figure 5 This is a diagram illustrating a method for manufacturing a semiconductor device according to Embodiment 1.
[0015] Figure 6 This is a diagram illustrating a method for manufacturing a semiconductor device according to Embodiment 1.
[0016] Figure 7 This is a diagram illustrating a method for manufacturing a semiconductor device according to Embodiment 1.
[0017] Figure 8 This is a cross-sectional view of the semiconductor device in the modified example.
[0018] Figure 9 This is a diagram showing the layer structure of the diffusion prevention layer in the modified example. Detailed Implementation
[0019] Implementation method 1.
[0020] exist Figure 1 The image shows the semiconductor device 10 according to Embodiment 1. The semiconductor device 10 is a semiconductor laser. Figure 1 A cross-section perpendicular to the direction of laser resonance is shown. This includes... Figure 1 The accompanying drawings are for illustrating the implementation methods, etc., and the dimensions and proportions of the components may sometimes differ from the actual figures.
[0021] The semiconductor device 10 includes a semiconductor substrate 12. The semiconductor substrate 12 is made of an n-type semiconductor, such as an n-type InP. A first electrode 14 is formed beneath the semiconductor substrate 12.
[0022] An n-type cladding layer 16 is formed on the semiconductor substrate 12. The n-type cladding layer 16 is made of an n-type semiconductor, such as n-type InP. The n-type cladding layer 16 may also be integral with the semiconductor substrate 12.
[0023] An active layer 18 is formed on the n-type cladding layer 16. The active layer 18 is made of an undoped semiconductor, such as InGaAsP.
[0024] A diffusion prevention layer 22 with a layered structure is formed on the active layer 18. Figure 2 This indicates the layer structure of diffusion prevention layer 22.
[0025] For diffusion prevention layer 22, a first diffusion prevention layer 26 and a second diffusion prevention layer 28 are alternately stacked from bottom to top. Figure 2 In this embodiment, the first diffusion prevention layer 26 and the second diffusion prevention layer 28 are each stacked in three layers, but it is sufficient that at least one layer of each is stacked. Furthermore, the topmost layer can be either the first diffusion prevention layer 26 or the second diffusion prevention layer 28. The first diffusion prevention layer 26 is made of an undoped semiconductor, such as InP. The second diffusion prevention layer 28 is made of an undoped semiconductor that matches the crystal lattice of the first diffusion prevention layer 26. In Embodiment 1, since the dopant of the p-type coating layer 20 is Zn, the second diffusion prevention layer 28 is formed of AlInAs satisfying the above conditions. Furthermore, the material of the second diffusion prevention layer 28 is not limited to AlInAs, but can also be InGaAsP, InGaAs, AlGaInAs, InGaAsP, InGaAs, etc., which match the crystal lattice of InP. Additionally, since the resistance of the first diffusion prevention layer 26 and the second diffusion prevention layer 28 increases with increasing film thickness, it is preferable that the film thickness of each layer is 10 nm or less. Furthermore, from the viewpoint of preventing the diffusion of dopants in the p-type coating layer 20, it is preferable that the first diffusion prevention layer 26 and the second diffusion prevention layer 28 are grouped into three or more groups.
[0026] A p-type cladding layer 20 is formed on the diffusion prevention layer 22. The p-type cladding layer 20 is, for example, made of a Zn-doped p-type semiconductor or p-type InP.
[0027] A contact layer 30 is formed on the p-type cladding layer 20. The contact layer 30 is made of a p-type semiconductor, such as p-type InGaAs.
[0028] A second electrode 32 is formed on the contact layer 30.
[0029] Here, the manufacturing method of the semiconductor device 10 according to Embodiment 1 will be described. First, as Figure 3As shown, an n-type cladding layer 16 is formed on the semiconductor substrate 12. The n-type cladding layer 16 is formed using MOCVD (Metal Organic Chemical Vapor Deposition). Subsequently, the semiconductor layers are stacked using MOCVD. However, the stacking method is not limited to MOCVD.
[0030] Next, as Figure 4 As shown, an active layer 18 is formed on the n-type coating layer 16.
[0031] Next, a diffusion prevention layer 22 is formed on the active layer 18. To form the diffusion prevention layer 22, a first diffusion prevention layer 26 is first formed on the active layer 18. Then, a second diffusion prevention layer 28 is formed on the first diffusion prevention layer 26. If necessary, the first diffusion prevention layer 26 is formed on the second diffusion prevention layer 28. These steps are repeated to achieve the required number of diffusion prevention layers 22, such as... Figure 5 As shown, a diffusion prevention layer 22 is formed.
[0032] Next, as Figure 6 As shown, a p-type coating layer 20 is formed on the diffusion prevention layer 22.
[0033] Next, as Figure 7 As shown, a contact layer 30 is formed on the p-type overlay layer 20.
[0034] Next, a first electrode 14 and a second electrode 32 are formed below the semiconductor substrate 12 and above the contact layer 30, respectively. This manufactures a... Figure 1 The semiconductor device 10 shown.
[0035] Here, the effect of the diffusion prevention layer 22 will be explained. Without the diffusion prevention layer 22, the dopant in the p-type cladding layer 20 may sometimes diffuse to the active layer 18. If the dopant reaches the active layer 18, the characteristics of the laser and its electrical properties will deteriorate. However, in the semiconductor device 10 according to Embodiment 1, since the diffusion prevention layer 22 is inserted between the p-type cladding layer 20 and the active layer 18, the dopant diffused from the p-type cladding layer 20 remains in the diffusion prevention layer 22, and diffusion to the active layer 18 is suppressed.
[0036] Furthermore, since the diffusion prevention layer 22 has a layered structure with alternating layers of the first diffusion prevention layer 26 and the second diffusion prevention layer 28, it effectively prevents dopant from diffusing into the active layer 18. Generally, dopant tends to be locally present near heterojunctions. In the semiconductor device 10 according to Embodiment 1, because the diffusion prevention layer 22 has a layered structure, multiple heterojunctions exist. For example, such as... Figure 2As shown, when the first diffusion prevention layer 26 and the second diffusion prevention layer 28 are each stacked in three layers, the number of interfaces increases by six compared to the case where the diffusion prevention layer 22 is not present. Because the number of interfaces increases due to the presence of the diffusion prevention layer 22, the effect of preventing the diffusion of dopants from the p-type coating layer 20 to the active layer 18 is improved in the semiconductor device 10 according to Embodiment 1.
[0037] The diffusion prevention layer 22 is not limited to a structure of alternating layers; it can be formed by stacking two or more undoped layers in the vertical direction. Each undoped layer simply needs to be different from its adjacent layers. Thus, since the number of interfaces increased by the insertion of the diffusion prevention layer 22 is more than two due to the stacking of two or more undoped layers in the vertical direction, the effect of preventing the dopant in the p-type coating layer 20 from diffusing into the active layer 18 is improved.
[0038] Furthermore, for the undoped layer of the diffusion prevention layer 22, it is preferable to use at least one semiconductor layer with a higher solid solubility for the dopant of the p-type coating layer 20 than that of the active layer 18. If such a semiconductor layer is used, the dopant of the p-type coating layer 20 will remain in the undoped layer and suppress diffusion to the active layer 18.
[0039] Implementation method 2.
[0040] The semiconductor device according to Embodiment 2 is the same as the semiconductor device 10 according to Embodiment 1, but differs from Embodiment 1 in that strain is applied to the second diffusion-preventing layer to reduce the bandgap difference with the first diffusion-preventing layer. The cross-section of the semiconductor device according to Embodiment 2 is... Figure 1 The diffusion prevention layer has the same layer structure as... Figure 2 same.
[0041] If the bandgap difference between the first and second diffusion-prevention layers is large, the resistance increases, potentially leading to a decrease in laser luminescence efficiency. On the other hand, as in the semiconductor device according to Embodiment 2, when strain is applied to the second diffusion-prevention layer to reduce the bandgap difference with the first diffusion-prevention layer, the resistance of the diffusion-prevention layer decreases. For example, when the second diffusion-prevention layer is composed of AlInAs, by adjusting the composition ratio of Al to In and applying strain, the bandgap difference with InP can be reduced, thus preventing a decrease in luminescence efficiency.
[0042] Implementation method 3.
[0043] The semiconductor device according to Embodiment 3 is a semiconductor device in which a diffusion prevention layer is formed in the laser modulation section of an EA (Electro Absorption) modulator or an MZ (Mach-Zehnder) modulator. The structure of the semiconductor device according to Embodiment 3 is the same as that of Embodiment 1, but the cross-section and the layer structure of the diffusion prevention layer are the same as those of Embodiment 1. Figure 1 , Figure 2 The same applies. If it is the laser modulation section of the modulator, since only a voltage needs to be applied between the first electrode and the second electrode, it is not necessary to consider the film thickness and band gap difference of the layer constituting the diffusion prevention layer.
[0044] The embodiments have been described above, but the semiconductor device in each embodiment may also be a mesa structure in which the region containing the active layer is formed as a stripe extending along the resonant direction of the laser.
[0045] Alternatively, the semiconductor substrate can also be p-type. Figure 8 The image shows a cross-section of the semiconductor device 40 in this case. Figure 8 In, with Figure 1 Unlike other semiconductor substrates, this one is shown with the semiconductor substrate on top for convenience. When the semiconductor substrate is p-type, a Zn-doped p-type cladding layer 50 is formed below the semiconductor substrate 42, and a diffusion prevention layer 52 is formed below the p-type cladding layer 50. Figure 9 The layer structure of the diffusion prevention layer 52 is shown. The bottom layer of the diffusion prevention layer 52 is a first diffusion prevention layer 56, and a second diffusion prevention layer 58 is formed above the first diffusion prevention layer 56. The first diffusion prevention layer 56 and the second diffusion prevention layer 58 are repeated on the second diffusion prevention layer 58 as needed. An active layer 48, an n-type cladding layer 46, and a contact layer 60 are formed below the diffusion prevention layer 52, and a first electrode 44 and a second electrode 62 are formed vertically. Thus, even when the semiconductor substrate is p-type, the insertion of the diffusion prevention layer enables a semiconductor device that effectively prevents the diffusion of dopants from the p-type cladding layer 50 into the active layer 48.
[0046] Explanation of reference numerals in the attached figures
[0047] 10, 40… Semiconductor device; 16, 46… n-type cladding layer; 18, 48… Active layer; 20, 50… p-type cladding layer; 22, 52… Diffusion prevention layer; 26, 56… First diffusion prevention layer; 28, 58… Second diffusion prevention layer.
Claims
1. A semiconductor device, characterized in that, have: n-type coating layer; An active layer is formed on the aforementioned n-type coating layer; A diffusion prevention layer is formed on the active layer and is constructed by stacking two or more undoped layers with compositions different from those of the adjacent layers in the vertical direction; and A p-type coating layer is formed on top of the aforementioned diffusion prevention layer.
2. The semiconductor device according to claim 1, characterized in that, At least one of the undoped layers of the diffusion prevention layer has a higher solid solubility for the dopant in the p-type coating layer than the active layer.
3. The semiconductor device according to claim 1 or 2, characterized in that, The thickness of the undoped layer is less than 10 nm.
4. The semiconductor device according to any one of claims 1 to 3, characterized in that, The aforementioned p-type coating layer is doped with Zn.
5. The semiconductor device according to claim 4, characterized in that, The aforementioned n-type coating layer is composed of InP. The above active layer is composed of InGaAsP. The aforementioned diffusion prevention layers alternately stack a first diffusion prevention layer composed of InP and a second diffusion prevention layer that matches the InP lattice, starting from the side closest to the active layer. The aforementioned p-type coating layer is composed of InP.
6. The semiconductor device according to claim 5, characterized in that, The aforementioned second diffusion prevention layer is composed of any one of AlInAs, InGaAsP, InGaAs, AlGaInAs, InGaAsP, and InGaAs.
7. The semiconductor device according to claim 5 or 6, characterized in that, In the above-mentioned diffusion prevention layer, there are three or more groups of the first diffusion prevention layer and the second diffusion prevention layer stacked together.
8. The semiconductor device according to any one of claims 5 to 7, characterized in that, The aforementioned second diffusion prevention layer was subjected to strain.
9. The semiconductor device according to any one of claims 1 to 8, characterized in that, The aforementioned semiconductor device is the laser modulation section of an EA modulator or an MZ modulator.