Strain collaborative regulation ge / ga in as epitaxial structure growth method
By introducing a self-assembled nanodot array and temperature gradient-controlled migration-enhanced epitaxy into the Ge/GaInAs heteroepitaxial structure, the lattice mismatch problem in Ge/GaInAs heteroepitaxial structure was solved, achieving efficient strain relaxation and defect trapping, and improving the carrier transport and photoelectric conversion performance of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHONGSHAN DEHUA CHIP TECH CO LTD
- Filing Date
- 2026-02-04
- Publication Date
- 2026-06-05
Smart Images
Figure CN122161197A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of optoelectronic device manufacturing, and in particular to a strain-coordinated method for growing Ge / GaInAs epitaxial structures. Background Technology
[0002] Epitaxial growth of high-quality III-V semiconductor materials on heterogeneous substrates is a core technological support for optoelectronic devices. III-V semiconductors, with their tunable band structure, high carrier mobility, and excellent photoelectric conversion efficiency, have application value in emerging fields. Heteroepitaxy, by combining III-V materials with low-cost, large-size substrates, overcomes the cost and size limitations of traditional homoepitaxy and achieves material functionality integration, making it an important direction for current semiconductor technology upgrades.
[0003] Among numerous heteroepitaxial systems, the combination of Ge substrate and GaInAs alloy is widely used in near-infrared optoelectronic devices and tandem solar cells due to the complementarity of their band structures. However, there is a significant lattice mismatch between Ge and GaInAs. This lattice mismatch introduces a large number of dislocation defects into the heterointerface and epitaxial layer. High dislocation density severely affects carrier transport efficiency, leading to nonradiative recombination enhancement, increased device leakage current, decreased photoelectric conversion efficiency, and reduced long-term stability. This has become the core bottleneck restricting the performance improvement of devices in this system.
[0004] Currently, lattice mismatch control technology for Ge / GaInAs heteroepitaxial growth still faces two major challenges, making it difficult to meet the fabrication requirements of high-performance devices:
[0005] I. Insufficient initial nucleation control and limited strain relaxation regulation capability.
[0006] The initial nucleation stage is crucial in determining the crystal quality, interface smoothness, and defect density of the epitaxial layer. To improve nucleation quality, migration-enhanced epitaxy (MEE) technology is widely used in the industry. However, even with this technology, the nucleation process of GaInAs on Ge substrates is still primarily two-dimensional planar nucleation. The arrangement of atoms on the substrate surface is strongly constrained by the substrate lattice orientation, making it impossible to precisely control the strain between the epitaxial layer and the substrate during the nucleation stage. As the epitaxial layer thickness increases, strain gradually accumulates and relaxes through dislocation slip and multiplication. The initial interface formed under the two-dimensional nucleation mode lacks sufficient strain buffer space, making the strain relaxation process difficult to control, ultimately leading to the retention and propagation of high dislocation defects.
[0007] Second, a single buffer layer solution has performance trade-offs and cannot meet multi-dimensional requirements.
[0008] Existing technologies generally use buffer layers to alleviate lattice mismatch and filter dislocation defects, but their core limitation is that using a single buffer layer system makes it difficult to simultaneously achieve synergistic optimization of the four key performance aspects: interface quality, strain relaxation, defect filtering, and carrier transport.
[0009] Traditional single buffer layer and nucleation regulation technologies, due to their inherent performance limitations, cannot simultaneously meet the above-mentioned multi-dimensional indicators. In particular, for the Ge / GaInAs structure, which serves as the bottom cell in perovskite / III-V tandem solar cells, this has become a key technical obstacle restricting the efficiency breakthrough and production of perovskite / III-V tandem solar cells. Summary of the Invention
[0010] The primary objective of this invention is to address the shortcomings of existing technologies by providing a strain-coordinated growth method for Ge / GaInAs epitaxial structures. This method enables efficient strain relaxation and defect trapping epitaxy in the early stages of nucleation. By combining defect engineering of self-assembled nanodots with atomically smooth growth of migration-enhanced epitaxy, the epitaxial initiation interface is reconstructed at the nanoscale.
[0011] The second objective of this invention is to provide a strain-coordinated controllable Ge / GaInAs epitaxial structure to address the shortcomings of the prior art.
[0012] The third objective of this invention is to provide a perovskite / III-V tandem solar cell to address the shortcomings of the prior art.
[0013] To achieve the aforementioned first objective, the technical solution provided by this invention is: a method for strain-coordinated regulation of the growth of Ge / GaInAs epitaxial structures, comprising the following steps:
[0014] S1. Grow a GaInP nucleation layer on a germanium substrate;
[0015] S2. Growing GaIn on GaInP nucleation layer 0.1 As matching buffer layer, bottom tunneling junction n-GaAs / p-AlGaAs and Al k Ga 1-x In x As lattice buffer layer; wherein, GaIn is grown in an intermittent epitaxial mode under a group V source atmosphere. 0.1 As a matching buffer layer and Al is grown using temperature gradient control and intermittent epitaxial mode. k Ga 1-x In x As a lattice buffer layer, the intermittent epitaxial mode is a process of cyclically performing growth from a group III source for t1 seconds to interrupting the group III source for t2 seconds, where t2 > t1;
[0016] S3, in Al k Ga 1-x In x A self-assembled Ga nanodot array is grown on an As lattice buffer layer; wherein, under a protective atmosphere, a Ga-covered germanium substrate is subjected to rapid thermal annealing to granulate the metallic Ga nanoparticles and combine them with Al. k Ga 1-x In x The surface of the As lattice buffer layer reacts to form a uniformly distributed self-assembled Ga nanodot array.
[0017] S4. Growth of Al on self-assembled Ga nanodot arrays k Ga 1-y In y As target matching buffer layer, Ga 1-y In y As target layer, AI 1-z In z P window layer and Ga 1-y In y As cap layer; where Al k Ga 1-y In y As a target-matching buffer layer as a coating layer for self-assembled Ga nanodot arrays and Ga 1-y In y As the template for the target layer.
[0018] Furthermore, step S2 includes:
[0019] Al was grown using temperature gradient control and intermittent epitaxial growth mode. k Ga 1-x In x During the process of creating the As lattice buffer layer, the In composition x and growth temperature T need to be changed continuously and synchronously, where:
[0020] The component x in In increases continuously from the initial value x1 to the target value x2, where 0 ≤ x1 < x2 ≤ 0.22;
[0021] The growth temperature T changes continuously from the initial temperature T1 to the final temperature T2, where 580°C ≤ T1 < T2 ≤ 660°C. A pre-defined functional relationship exists between the growth temperature T and the In composition x: T = f(x). This functional relationship is either linear or convex, meaning that the growth temperature T increases with increasing In composition, and the heating rate remains constant or gradually accelerates. The initial temperature T1 corresponds to the optimal growth temperature for low In composition materials, and the final temperature T2 corresponds to the optimal growth temperature for high In composition materials.
[0022] Furthermore, step S2 includes:
[0023] The range of t1 is 3-10 seconds, and the range of t2 is 15-40 seconds.
[0024] Furthermore, step S2 includes:
[0025] Al growth k Ga 1-x In x During the process of creating the As lattice buffer layer, the Al component k ranges from 0.2 to 0.6, and the In component x ranges from 0.01 to 0.22. k Ga 1-x In x The As lattice buffer layer consists of 5-10 layers, each with a thickness of 150-300 nm, a growth temperature of 600-640℃, and a growth rate of 0.5-1.5 nm / s.
[0026] Furthermore, step S3 includes:
[0027] The rapid thermal annealing process is performed at a temperature of 400-600℃ for 30-120 seconds.
[0028] Furthermore, step S3 includes:
[0029] The average diameter of the Ga nanodots formed in the self-assembled Ga nanodot array is 20-80 nm, and the density of the Ga nanodots is 10. 9 -10 11 cm -2 .
[0030] To achieve the second objective mentioned above, the technical solution provided by this invention is: a strain-coordinated Ge / GaInAs epitaxial structure, prepared according to the above-described growth method, comprising: a GaInP nucleation layer, a GaIn layer, and a GaIn substrate grown sequentially from bottom to top on a germanium substrate. 0.1 As matching buffer layer, bottom tunneling junction n-GaAs / p-AlGaAs, Al k Ga 1-x In x As lattice buffer layer, self-assembled Ga nanodot array, Al k Ga 1-y In y As target matching buffer layer, Ga 1-y In y As target layer, AI 1-z In z P window layer and Ga 1-y In y As cap layer.
[0031] Furthermore, the Al k Ga 1-x Inx The As lattice buffer layer includes:
[0032] The value of k for Al component ranges from 0.2 to 0.6, and the value of x for In component ranges from 0.01 to 0.22. k Ga 1-x In x The As lattice buffer layer consists of 5-10 layers, each with a thickness of 150-300 nm, a growth temperature of 600-640℃, and a growth rate of 0.5-1.5 nm / s.
[0033] Furthermore, the self-assembled Ga nanodot array includes:
[0034] The average diameter of Ga nanodots is 20-80 nm, and the density of Ga nanodots is 10. 9 -10 11 cm -2 .
[0035] To achieve the third objective mentioned above, the technical solution provided by the present invention is as follows: a perovskite / III-V tandem solar cell, including a bottom cell, wherein the bottom cell is a Ge / GaInAs double-junction solar cell prepared based on the strain-coordinated regulation of the Ge / GaInAs epitaxial structure mentioned above.
[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0037] 1. Temperature gradient control ensures the smoothness and controllability of the strain relaxation process; in Al k Ga 1-x In x In the initial stage of As lattice buffer layer growth, a relatively low starting temperature T1 is used to suppress three-dimensional island growth and promote two-dimensional layered growth, resulting in a smooth initial interface. As the In composition x and layer thickness increase, strain energy gradually accumulates. At this point, the growth temperature T is gradually increased to provide higher mobility and kinetic energy for atoms and dislocations, prompting the strain energy to be released through controlled, gentle dislocation slip and annihilation, rather than through violent dislocation bursts. A higher termination temperature T2 is used in the later stages of buffer layer growth, utilizing the efficient dislocation interactions and annihilation mechanisms at high temperatures to further filter and reduce penetrating dislocations. Combined with intermittent migration-enhanced epitaxy, this ensures an atomically smooth growth front and the lowest intrinsic point defects. The combination of these two methods achieves the highest defect filtering efficiency for this layer.
[0038] 2. In Al k Ga 1-x In xIntroducing a self-assembled Ga nanodot array on top of an As lattice buffer layer serves as a nanoscale interface for local strain relaxation and defect trapping, enabling further absorption of residual strain and termination of any dislocations that penetrate to it.
[0039] 3. The AlGaInAs target-matching buffer layer serves as both a coating layer for Ga nanodots and a Ga... 1-y In y As a template for the target layer, its Al composition is designed to form a blocking effect on charge carriers, thereby improving the quantum efficiency within the device.
[0040] This invention achieves three-dimensional, multi-scale suppression of dislocations and point defects by forming a triple system of "nucleation layer + lattice buffer layer + nanodot array". Attached Figure Description
[0041] Figure 1 This is a schematic diagram of the structure of Ge / GaInAs epitaxial structure for strain-coordinated regulation.
[0042] Figure 2 This is a magnified view of a portion of the structure of a self-assembled Ga nanodot array.
[0043] Figure 3 This is a schematic diagram of the apparent defects of a traditional single-buffered epitaxial structure.
[0044] Figure 4 A schematic diagram illustrating the apparent defects of Ge / GaInAs epitaxial structures under strain-coordinated regulation. Detailed Implementation
[0045] The present invention will be further described below with reference to specific embodiments.
[0046] Example 1
[0047] The strain-coordinated growth method for Ge / GaInAs epitaxial structures provided in this embodiment includes the following steps:
[0048] S1. Grow a GaInP nucleation layer on a germanium substrate;
[0049] S2. Growing GaIn on GaInP nucleation layer 0.1 As matching buffer layer, bottom tunneling junction n-GaAs / p-AlGaAs and Al k Ga 1-x In x As lattice buffer layer; wherein, GaIn is grown in an intermittent epitaxial mode under a group V source atmosphere. 0.1 As a matching buffer layer and Al is grown using temperature gradient control and intermittent epitaxial mode. k Ga 1-x Inx As a lattice buffer layer, the intermittent epitaxial mode is a process of cyclically performing growth from a group III source for t1 seconds to interrupting the group III source for t2 seconds, where t2 > t1, t1 ranges from 3 to 10 seconds, and t2 ranges from 15 to 40 seconds. k Ga 1-x In x In the As lattice buffer layer, the Al component k ranges from 0.2 to 0.6, and the In component x ranges from 0.01 to 0.22. k Ga 1-x In x The As lattice buffer layer consists of 5-10 layers, each with a thickness of 150-300 nm, a growth temperature of 600-640℃, and a growth rate of 0.5-1.5 nm / s.
[0050] Al was grown using temperature gradient control and intermittent epitaxial growth mode. k Ga 1-x In x During the process of creating the As lattice buffer layer, the In composition x and growth temperature T need to be changed continuously and synchronously, where:
[0051] The component x in In increases continuously from the initial value x1 to the target value x2, where 0 ≤ x1 < x2 ≤ 0.22.
[0052] The growth temperature T changes continuously from the initial temperature T1 to the final temperature T2, where 580°C ≤ T1 < T2 ≤ 660°C. A pre-defined functional relationship exists between the growth temperature T and the In composition x: T = f(x). This functional relationship is either linear or convex, meaning that the growth temperature T increases with increasing In composition, and the heating rate remains constant or gradually accelerates. The initial temperature T1 corresponds to the optimal growth temperature for low In composition materials, and the final temperature T2 corresponds to the optimal growth temperature for high In composition materials.
[0053] S3, in Al k Ga 1-x In x Self-assembled Ga nanodot arrays are grown on an As lattice buffer layer; wherein, under a protective atmosphere, a Ga-covered germanium substrate is subjected to rapid thermal annealing at a temperature of 400-600℃ for 30-120s to granulate the metallic Ga nanoparticles and combine them with Al. k Ga 1-x In x The surface of the As lattice buffer layer reacts to form a self-assembled Ga nanodot array with uniform size and distribution; wherein the average diameter of the Ga nanodots formed in the self-assembled Ga nanodot array is 20-80 nm, and the density of Ga nanodots is 10. 9 -1011 cm -2 .
[0054] S4. Growth of Al on self-assembled Ga nanodot arrays k Ga 1-y In y As target matching buffer layer, Ga 1-y In y As target layer, AI 1-z In z P window layer and Ga 1-y In y As cap layer; where Al k Ga 1-y In y As a target-matching buffer layer as a coating layer for self-assembled Ga nanodot arrays and Ga 1-y In y As the template for the target layer; Ga 1-y In y In the target layer (As), the value of y ranges from 0.08 to 0.18; Al 1-z In z In the P-window layer, the value of z ranges from 0.55 to 0.7.
[0055] Example 2
[0056] See Figure 1 As shown, this embodiment provides a strain-coordinated Ge / GaInAs epitaxial structure, prepared according to the growth method described in Example 1. The structure includes: a GaInP nucleation layer 2, a GaInP nucleation layer 3, and a GaIn4N ... 0.1 As matching buffer layer 3, bottom tunnel junction n-GaAs / p-AlGaAs 4, Al k Ga 1-x In x 5. As lattice buffer layer, 6. Self-assembled Ga nanodot array, Al k Ga 1-y In y As target matching buffer layer 7, Ga 1-y In y As target layer 8, Al 1-z In z P window layer 9 and Ga 1-y In y As cap layer 10.
[0057] Al k Ga 1-x In xThe As lattice buffer layer 5 includes: Al composition k ranging from 0.2 to 0.6, In composition x ranging from 0.01 to 0.22, and Al... k Ga 1-x In x The As lattice buffer layer 5 has 5-10 layers, each with a thickness of 150-300 nm, a growth temperature of 600-640℃, and a growth rate of 0.5-1.5 nm / s.
[0058] See Figure 2 The image shown is a partially magnified view of the structure of the self-assembled Ga nanodot array 6, where 'a' represents a surface defect. The average diameter of the Ga nanodots formed in the self-assembled Ga nanodot array is 20-80 nm, and the density of the Ga nanodots is 102. 9 -10 11 cm -2 .
[0059] Compare with Example 1
[0060] Unlike Example 2, this comparative example provides a conventional epitaxial structure, employing a conventional single buffer layer. A GaInP nucleation layer and a GaInAs buffer layer are grown on a Ge-based solar cell, followed by direct growth of a 2.5 μm thick linearly graded In layer. x Ga 1- x Al k As buffer layer, Ga 1-y In y As target layer, AI 1-z In z P window layer and Ga 1-y In y As cap layer.
[0061] See Figure 3 The diagram shown illustrates the apparent defects of this comparative example. Compared to Example 2, the dislocation density of Comparative Example 1, calculated through surface fitting, is ~2×10⁻⁶. 7 cm -2 The dislocation density in Example 2 is as low as ~1×10⁻⁶. 4 cm -2 This represents an improvement of nearly three orders of magnitude.
[0062] Meanwhile, two types of Ge / GaInAs double-junction solar cells were prepared according to Comparative Example 1 and Example 2, respectively, and JV tests were performed. The results are shown in Table 1 below:
[0063] project Jsc (mA / cm 2 )]]> Voc (mV) FF (%) Eff (%) Example 2 30.81 1128.25 79.8 20.50 Compare with Example 1 25.8 1090.21 73.3 15.24
[0064] Table 1. JV Test Data for Two Ge / GaInAs Dual-Junction Cells
[0065] JV test data shows that the battery FF of Example 1 is 73.3% and the Voc is 1090.21mV; while the battery FF of Example 1 is increased to 79.8% and the Voc is increased to 1128.25mV, showing a significant performance improvement.
[0066] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, any changes made in accordance with the shape and principle of the present invention should be covered within the protection scope of the present invention.
Claims
1. A method for strain-coordinated control of Ge / GaInAs epitaxial structure growth, characterized in that, Includes the following steps: S1. Grow a GaInP nucleation layer on a germanium substrate; S2. Growing GaIn on GaInP nucleation layer 0.1 As matching buffer layer, bottom tunneling junction n-GaAs / p-AlGaAs and Al k Ga 1-x In x As lattice buffer layer; wherein, GaIn is grown in an intermittent epitaxial mode under a group V source atmosphere. 0.1 As a matching buffer layer and Al is grown using temperature gradient control and intermittent epitaxial mode. k Ga 1-x In x As a lattice buffer layer, the intermittent epitaxial mode is a process of cyclically performing growth from a group III source for t1 seconds to interrupting the group III source for t2 seconds, where t2 > t1; S3, in Al k Ga 1-x In x A self-assembled Ga nanodot array is grown on an As lattice buffer layer; wherein, under a protective atmosphere, a Ga-covered germanium substrate is subjected to rapid thermal annealing to granulate the metallic Ga nanoparticles and combine them with Al. k Ga 1-x In x The surface of the As lattice buffer layer reacts to form a uniformly distributed self-assembled Ga nanodot array. S4. Growth of Al on self-assembled Ga nanodot arrays k Ga 1-y In y As target matching buffer layer, Ga 1-y In y As target layer, AI 1-z In z P window layer and Ga 1-y In y As cap layer; where Al k Ga 1-y In y As a target-matching buffer layer as a coating layer for self-assembled Ga nanodot arrays and Ga 1-y In y As the template for the target layer.
2. The method for strain-coordinated control of Ge / GaInAs epitaxial structure growth according to claim 1, characterized in that, Step S2 includes: Al was grown using temperature gradient control and intermittent epitaxial growth mode. k Ga 1-x In x During the process of creating the As lattice buffer layer, the In composition x and growth temperature T need to be changed continuously and synchronously, where: The component x in In increases continuously from the initial value x1 to the target value x2, where 0 ≤ x1 < x2 ≤ 0.22; The growth temperature T changes continuously from the initial temperature T1 to the final temperature T2, where 580°C ≤ T1 < T2 ≤ 660°C. A pre-defined functional relationship exists between the growth temperature T and the In composition x: T = f(x). This functional relationship is either linear or convex, meaning that the growth temperature T increases with increasing In composition, and the heating rate remains constant or gradually accelerates. The initial temperature T1 corresponds to the optimal growth temperature for low In composition materials, and the final temperature T2 corresponds to the optimal growth temperature for high In composition materials.
3. The method for strain-coordinated control of Ge / GaInAs epitaxial structure growth according to claim 1, characterized in that, Step S2 includes: The range of t1 is 3-10 seconds, and the range of t2 is 15-40 seconds.
4. The method for strain-coordinated control of Ge / GaInAs epitaxial structure growth according to claim 1, characterized in that, Step S2 includes: Al growth k Ga 1-x In x During the process of creating the As lattice buffer layer, the Al component k ranges from 0.2 to 0.6, and the In component x ranges from 0.01 to 0.
22. k Ga 1-x In x The As lattice buffer layer consists of 5-10 layers, each with a thickness of 150-300 nm, a growth temperature of 600-640℃, and a growth rate of 0.5-1.5 nm / s.
5. The method for strain-coordinated control of Ge / GaInAs epitaxial structure growth according to claim 1, characterized in that, Step S3 includes: The rapid thermal annealing process is performed at a temperature of 400-600℃ for 30-120 seconds.
6. The method for strain-coordinated control of Ge / GaInAs epitaxial structure growth according to claim 1, characterized in that, Step S3 includes: The average diameter of the Ga nanodots formed in the self-assembled Ga nanodot array is 20-80 nm, and the density of the Ga nanodots is 10. 9 -10 11 cm -2 .
7. A strain-coordinated Ge / GaInAs epitaxial structure, characterized in that, The structure is prepared by the growth method according to any one of claims 1-6, and comprises: a GaInP nucleation layer, a GaIn layer, and a GaIn substrate grown sequentially from bottom to top on a germanium substrate. 0.1 As matching buffer layer, bottom tunneling junction n-GaAs / p-AlGaAs, Al k Ga 1-x In x As lattice buffer layer, self-assembled Ga nanodot array, Al k Ga 1-y In y As target matching buffer layer, Ga 1-y In y As target layer, AI 1-z In z P window layer and Ga 1-y In y As cap layer.
8. The strain-coordinated Ge / GaInAs epitaxial structure according to claim 7, characterized in that, The Al k Ga 1-x In x The As lattice buffer layer includes: The value of k for Al component ranges from 0.2 to 0.6, and the value of x for In component ranges from 0.01 to 0.
22. k Ga 1-x In x The As lattice buffer layer consists of 5-10 layers, each with a thickness of 150-300 nm, a growth temperature of 600-640℃, and a growth rate of 0.5-1.5 nm / s.
9. The strain-coordinated Ge / GaInAs epitaxial structure according to claim 7, characterized in that, The self-assembled Ga nanodot array includes: The average diameter of Ga nanodots is 20-80 nm, and the density of Ga nanodots is 10. 9 -10 11 cm -2 .
10. A perovskite / III-V tandem solar cell, characterized in that, The invention includes a bottom cell, which is a Ge / GaInAs double-junction cell fabricated based on the strain-coordinated Ge / GaInAs epitaxial structure as described in any one of claims 7-9.