Photoelectric detector and preparation method thereof

Abstract

The invention provides a photoelectric detector and a preparation method thereof, which are applied to the technical field of semiconductors, and the photoelectric detector comprises a gallium oxide light absorption layer; the two-dimensional Van der Waals material layer is arranged on the gallium oxide light absorption layer and is combined with the gallium oxide light absorption layer through Van der Waals force to form a vertical heterojunction; the metal electrode is formed on the surfaces of the gallium oxide light absorption layer and the two-dimensional Van der Waals material layer; wherein the work function of the two-dimensional Van der Waals material layer is matched with the work function of the gallium oxide light absorption layer, so that staggered energy band arrangement is formed at the interface of the vertical heterojunction. According to the invention, interface defects caused by lattice mismatch can be avoided, and non-radiative recombination of photon-generated carriers can be reduced, so that the response speed and photoelectric conversion efficiency of the photoelectric detector can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of semiconductor technology, and in particular, to a photodetector and a preparation method thereof. BACKGROUND

[0002] A photodetector is a kind of semiconductor device capable of converting incident light signals into electrical signals, and has a wide range of applications in the fields of optical communication, imaging, sensing and spectral analysis. Among them, the photodetector based on wide bandgap semiconductor material (such as gallium oxide) has attracted extensive attention of researchers due to its excellent thermal stability and chemical stability, as well as its unique application potential in the solar blind ultraviolet band.

[0003] Gallium oxide, especially its β-phase single crystal, as a kind of ultra-wide bandgap semiconductor material, has a bandgap width of about 4.9 eV, which is an ideal material for realizing high-performance solar blind ultraviolet detection. Traditional gallium oxide-based photodetectors usually adopt a metal-semiconductor-metal (MSM) structure or a Schottky junction structure. However, the photoelectric response of such devices mainly depends on the intrinsic absorption of the gallium oxide material itself, and the response spectral range is usually limited to the ultraviolet band, which is difficult to effectively expand to the visible light band or even the near-infrared band, which greatly limits its application in wide-spectrum detection scenarios.

[0004] In order to broaden the spectral response range, the prior art attempts to construct a heterojunction between gallium oxide and other semiconductor materials. A common idea is to integrate materials such as indium tin oxide (ITO), silicon (Si) or other III-V compound semiconductors with gallium oxide. However, there is a significant lattice mismatch and difference in thermal expansion coefficient between such material systems and gallium oxide. During the epitaxial growth of the heterojunction, a high density of lattice defects and dangling bonds will inevitably be generated at the interface. These defects will become recombination centers for carriers, seriously trapping photo-generated carriers, resulting in an increase in carrier recombination probability and a decrease in effective separation efficiency, thereby degrading key performance indicators such as responsivity and response speed of the device.

[0005] Therefore, for gallium oxide-based photodetectors, how to effectively broaden the spectral response range without introducing additional interface defects, and at the same time ensure the efficient separation and rapid transport of photo-generated carriers, has become a technical problem to be solved by those skilled in the art. SUMMARY

[0006] In view of the above problems, the present disclosure provides a photodetector and a preparation method thereof, which at least solve one of the above problems.

[0007] According to a first aspect of this disclosure, a photodetector is provided, the photodetector comprising: a gallium oxide light-absorbing layer 14; a two-dimensional van der Waals material layer 13 disposed on the gallium oxide light-absorbing layer 14 and bonded to the gallium oxide light-absorbing layer 14 by van der Waals forces to form a vertical heterojunction; and a metal electrode formed on the surfaces of the gallium oxide light-absorbing layer 14 and the two-dimensional van der Waals material layer 13; wherein the work function of the two-dimensional van der Waals material layer 13 matches the work function of the gallium oxide light-absorbing layer 14, such that an interleaved band arrangement is formed at the interface of the vertical heterojunction.

[0008] According to an embodiment of this application, the metal electrode includes: a source electrode 11 disposed above the two-dimensional van der Waals material layer 13; and a drain electrode 15 disposed above the gallium oxide light absorption layer 14 region not covered by the two-dimensional van der Waals material 13.

[0009] According to an embodiment of this application, it further includes: an encapsulation layer 12 covering the two-dimensional van der Waals material layer 13, the gallium oxide light absorption layer 14, and the metal electrode.

[0010] According to an embodiment of this application, the electrode materials of the source 11 and drain 15 are selected based on the work function of the two-dimensional van der Waals material layer 13 and the gallium oxide light absorption layer 14 to form an ohmic contact or a Schottky contact.

[0011] According to an embodiment of this application, the two-dimensional van der Waals material layer 13 includes at least one of molybdenum disulfide, tungsten diselenide, tungsten disulfide, molybdenum diselenide, and black phosphorus.

[0012] According to an embodiment of this application, the interface of the vertical heterojunction is a staggered type II band structure.

[0013] According to a second aspect of this disclosure, a method for fabricating a photodetector is provided, the method comprising: providing a gallium oxide light-absorbing layer 14; transferring a two-dimensional van der Waals material onto the gallium oxide light-absorbing layer 14 to form a two-dimensional van der Waals material layer 13 and a vertical heterojunction; and fabricating metal electrodes on the surfaces of the gallium oxide light-absorbing layer 14 and the two-dimensional van der Waals material layer 13; wherein the work function of the two-dimensional van der Waals material layer 13 matches the work function of the gallium oxide light-absorbing layer 14, thereby forming an interleaved band arrangement at the interface of the vertical heterojunction.

[0014] According to an embodiment of this application, providing the gallium oxide light absorption layer 14 includes: providing a gallium oxide single wafer; and performing mesa etching on the gallium oxide single wafer to form the gallium oxide light absorption layer 14.

[0015] According to an embodiment of this application, the fabrication of metal electrodes on the surfaces of the gallium oxide light-absorbing layer 14 and the two-dimensional van der Waals material layer 13 includes: fabricating a source electrode 11 on the two-dimensional van der Waals material layer 13; and fabricating a drain electrode 15 on the gallium oxide light-absorbing layer 14.

[0016] According to an embodiment of this application, the method further includes: depositing an encapsulation layer 12, the encapsulation layer 12 covering the two-dimensional van der Waals material layer 13, the gallium oxide light absorption layer 14, and the metal electrode.

[0017] According to the photodetector and its fabrication method provided in this disclosure, a van der Waals heterojunction is formed by a two-dimensional van der Waals material layer and a gallium oxide light-absorbing layer. This avoids interface defects caused by lattice mismatch and significantly reduces nonradiative recombination of photogenerated carriers, thereby greatly improving the device's response speed and photoelectric conversion efficiency. By forming a staggered type-II band arrangement with a built-in electric field at the heterojunction interface through band engineering, efficient spatial separation of photogenerated electron-hole pairs is achieved, effectively enhancing the detector's photoresponse performance and detection sensitivity over a wide spectral range from ultraviolet to infrared. Attached Figure Description

[0018] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0019] Figure 1A A schematic diagram of a photodetector according to an embodiment of the present disclosure is shown.

[0020] Figure 1B This illustration schematically depicts an embodiment according to the present disclosure. Figure 1A A side view of the photodetector in the image;

[0021] Figure 2 A flowchart illustrating a method for fabricating a photodetector according to an embodiment of the present disclosure is shown schematically.

[0022] Figure 3A This diagram schematically illustrates an application of a photodetector according to an embodiment of the present disclosure;

[0023] Figure 3B This illustration schematically shows the use of a convolutional neural network according to embodiments of the present disclosure. Figure 3A A schematic diagram illustrating the training of the two datasets. Detailed Implementation

[0024] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0026] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0027] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0028] Two-dimensional van der Waals materials, as photodetector materials, possess high light absorption, low noise, and fast photoresponse rates. Furthermore, they generally exhibit broad spectral response characteristics, making them suitable for photodetection from the ultraviolet to the infrared. However, for solar-blind ultraviolet light (200nm-280nm), most two-dimensional van der Waals materials suffer from low light absorption efficiency and carrier recombination. Therefore, structural design can significantly improve their response performance. Gallium oxide (GaO) is a wide-bandgap semiconductor material with a bandgap of approximately 4.8-5.3 eV, capable of detecting solar-blind ultraviolet light. β-type GaO, in particular, exhibits high thermal and chemical stability, and GaO-based photodetectors are widely used in flame detection, ultraviolet index monitoring, and biomedical imaging.

[0029] By constructing a two-dimensional van der Waals material / gallium oxide heterojunction, the resulting interface effect and staggered type II band structure effectively enhance the material's light absorption and improve carrier separation efficiency. A broadband photodetector fabricated based on this heterojunction can detect multiple wavelengths of light. Using a convolutional neural network, multispectral image classification can be achieved. By processing image data from multiple wavelengths captured by the broadband photodetector, the image classification accuracy can be improved.

[0030] Figure 1A A schematic diagram of a photodetector according to an embodiment of the present disclosure is shown.

[0031] like Figure 1A As shown, the photodetector includes a gallium oxide light-absorbing layer 14, a two-dimensional van der Waals material layer 13 thereon, and a metal electrode. The metal electrode may include a source electrode 11 disposed above the two-dimensional van der Waals material layer 13 and a drain electrode 15 disposed above the gallium oxide light-absorbing layer 14. The two-dimensional van der Waals material layer 13 is disposed above the gallium oxide light-absorbing layer 14, and the two are bonded together by van der Waals forces to form a vertical heterojunction.

[0032] The photodetector may also include an encapsulation layer 12 covering all the above structures. The encapsulation layer 12 covers a two-dimensional van der Waals material layer 13, a gallium oxide light-absorbing layer 14, and a metal electrode.

[0033] In some embodiments, the electrode materials of the source 11 and drain 15 are selected based on the work function of the two-dimensional van der Waals material layer 13 and the gallium oxide light-absorbing layer 14 to form an ohmic contact or a Schottky contact.

[0034] In some embodiments, the two-dimensional van der Waals material layer 13 includes at least one of molybdenum disulfide, tungsten diselenide, tungsten disulfide, molybdenum diselenide, and black phosphorus.

[0035] In some embodiments, the interface of the vertical heterojunction is a staggered type II band structure.

[0036] Figure 1B This illustration schematically depicts an embodiment according to the present disclosure. Figure 1A A side view of the photodetector in the image.

[0037] like Figure 1BAs shown, a two-dimensional van der Waals material layer 13 and a gallium oxide light-absorbing layer 14 form a vertical heterojunction through van der Waals forces. Since van der Waals interactions do not require chemical bonding, the problem of interface defects introduced by lattice mismatch is fundamentally avoided. The low-defect interface significantly reduces the recombination efficiency of photogenerated carriers, thereby contributing to improved device response speed. By selecting two-dimensional van der Waals material layer 13 and gallium oxide light-absorbing layer 14 with matched work functions, a staggered (type-II) band arrangement (i.e., "type II band structure") can be formed at the heterojunction interface. This band structure can drive the effective spatial separation of photogenerated electrons and holes, thereby further improving the photoresponse performance of the photodetector.

[0038] Figure 2 A flowchart illustrating a method for fabricating a photodetector according to an embodiment of the present disclosure is shown schematically.

[0039] like Figure 2 As shown, the fabrication method of this photodetector includes operation S210-operation S230.

[0040] In operation S210, a gallium oxide light-absorbing layer 14 is provided.

[0041] In some embodiments, a gallium oxide single-chip wafer may be provided, and mesa etching may be performed on the gallium oxide single-chip wafer to form a gallium oxide light-absorbing layer 14.

[0042] Specifically, ultraviolet lithography and inductively coupled plasma (ICP) etching processes can be combined to etch device mesas. The size of the mesas is determined based on the dimensions of the two-dimensional van der Waals material and the dimensions of the metal electrodes. Subsequently, electrical isolation treatment needs to be performed between the mesas to prevent device crosstalk.

[0043] In some embodiments, the isolation material may be selected from silicon oxide, aluminum oxide, etc., and deposited by plasma-enhanced chemical vapor deposition (PECVD) or atomic layer deposition (ALD). After depositing the isolation layer, ultraviolet lithography and ICP etching are used to create windows to expose the gallium oxide mesa. To eliminate surface damage that may be caused by dry etching, the surface can be treated with a mixture of concentrated sulfuric acid and hydrogen peroxide to reduce surface defects.

[0044] In operation S220, a two-dimensional van der Waals material is transferred onto the gallium oxide light-absorbing layer 14 to form a two-dimensional van der Waals material layer 13 and a vertical heterojunction.

[0045] In some embodiments, the transfer operation can be performed via dry transfer. Two-dimensional van der Waals materials can be obtained, depending on their type, by mechanically exfoliating single-crystal materials combined with dry transfer, or by transfer after chemical vapor deposition growth.

[0046] In operation S230, metal electrodes are fabricated on the surfaces of gallium oxide light-absorbing layer 14 and two-dimensional van der Waals material layer 13.

[0047] In some embodiments, electrode materials whose work function matches that of the two-dimensional van der Waals material layer 13 and the gallium oxide light-absorbing layer 14 can be selected to form ohmic contacts or Schottky contacts. Depending on the selected electrode material, processes such as transfer electrode method or thermal evaporation method can be used for fabrication.

[0048] In some embodiments, a source electrode 11 can be fabricated on a two-dimensional van der Waals material layer 13; and a drain electrode 15 can be fabricated on a gallium oxide light-absorbing layer 14.

[0049] In some embodiments, an encapsulation layer 12 may be deposited, which covers a two-dimensional van der Waals material layer 13, a gallium oxide light-absorbing layer 14, and a metal electrode.

[0050] In some embodiments, the encapsulation layer can be made of transparent materials such as silicon oxide or aluminum oxide. The device structure can be optically simulated using the finite-difference time-domain (FDTD) method. Encapsulation layers of different thicknesses have different anti-reflection effects on incident light. Therefore, selecting and fabricating an encapsulation layer with an appropriate thickness can simultaneously protect the device and improve its optical performance.

[0051] Figure 3A The diagram schematically illustrates an application of a photodetector according to an embodiment of the present disclosure.

[0052] like Figure 3A As shown, this photodetector can be integrated into the imaging system as a photosensitive unit. Under the illumination of a composite light source, the reflected light from the object's surface is received by the photodetector via a 4f imaging system. Thanks to its wide-spectrum response characteristics, the photodetector can detect light signals from the ultraviolet to the infrared bands and convert them into electrical signals, ultimately generating a high-resolution wide-spectrum image. If replaced with a traditional photodetector sensitive only to a single band, only images of that band can be acquired, greatly limiting the richness of the information obtained. To compare and verify the advantages of the wide-spectrum detector, this application embodiment uses different objects to construct two types of datasets: one is a multispectral image dataset generated by the photodetector provided in this application embodiment, and the other is a single-band image dataset based on a single-band detector.

[0053] Figure 3B This illustration schematically shows the use of a convolutional neural network according to embodiments of the present disclosure. Figure 3A A schematic diagram illustrating the training of the two datasets.

[0054] like Figure 3BAs shown, this embodiment of the application uses a convolutional neural network (CNN) to train and evaluate the performance of the two datasets mentioned above. Specifically, the CNN utilizes convolutional layers to automatically extract spatial features of the images, pooling layers to reduce the dimensionality of the feature maps, and finally, fully connected layers to integrate the information and output the classification results. During training, the backpropagation algorithm is used to optimize the network parameters to minimize the cross-entropy loss function, thereby improving the model's accuracy and generalization ability. After training, the recognition accuracy of the model on the two test sets is calculated and compared. Experimental results show that the model trained based on the photodetector dataset provided in this embodiment of the application achieves higher recognition accuracy. This verifies the significant advantages of the data provided by the photodetector in terms of information richness and feature representation ability.

[0055] The photodetector fabrication method provided in this disclosure eliminates the need for complex lattice matching or high-temperature epitaxial growth. It enables the construction of heterojunctions through methods such as mechanical exfoliation, transfer stacking, or chemical vapor deposition (CVD), significantly reducing fabrication difficulty and cost. Furthermore, due to the atomic-level thickness of the low-dimensional material, the device size can be drastically reduced, making it suitable for high-density integration and miniaturized applications. After packaging, the device exhibits excellent environmental stability and long-term operational reliability, enabling it to adapt to complex operating environments and ensuring large-scale mass production.

[0056] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0057] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A photodetector, characterized in that, The photodetector includes: Gallium oxide light-absorbing layer (14); A two-dimensional van der Waals material layer (13) is disposed on the gallium oxide light absorption layer (14) and is bonded to the gallium oxide light absorption layer (14) by van der Waals forces to form a vertical heterojunction; Metal electrodes are formed on the surfaces of the gallium oxide light-absorbing layer (14) and the two-dimensional van der Waals material layer (13); The work function of the two-dimensional van der Waals material layer (13) matches the work function of the gallium oxide light absorption layer (14), resulting in an interleaved band arrangement at the interface of the vertical heterojunction.

2. The photodetector according to claim 1, characterized in that, The metal electrode includes: The source electrode (11) is disposed above the two-dimensional van der Waals material layer (13); The drain (15) is disposed above the region of the gallium oxide light-absorbing layer (14) that is not covered by the two-dimensional van der Waals material (13).

3. The photodetector according to claim 1, characterized in that, Also includes: The encapsulation layer (12) covers the two-dimensional van der Waals material layer (13), the gallium oxide light absorption layer (14), and the metal electrode.

4. The photodetector according to claim 2, characterized in that, The electrode materials of the source (11) and drain (15) are selected according to the work function of the two-dimensional van der Waals material layer (13) and the gallium oxide light absorption layer (14) to form an ohmic contact or a Schottky contact.

5. The photodetector according to claim 1, characterized in that, The two-dimensional van der Waals material layer (13) includes at least one of molybdenum disulfide, tungsten diselenide, tungsten disulfide, molybdenum diselenide, and black phosphorus.

6. The photodetector according to claim 1, characterized in that, The interface of the vertical heterojunction is a staggered type II band structure.

7. A method for fabricating a photodetector, characterized in that, The method includes: A gallium oxide light-absorbing layer is provided (14); Two-dimensional van der Waals material is transferred onto the gallium oxide light-absorbing layer (14) to form a two-dimensional van der Waals material layer (13) and a vertical heterojunction; Metal electrodes are fabricated on the surfaces of the gallium oxide light-absorbing layer (14) and the two-dimensional van der Waals material layer (13); The work function of the two-dimensional van der Waals material layer (13) matches the work function of the gallium oxide light absorption layer (14), resulting in an interleaved band arrangement at the interface of the vertical heterojunction.

8. The method according to claim 7, characterized in that, The gallium oxide light-absorbing layer (14) includes: Provide gallium oxide single-chip solutions; Mesa etching is performed on the gallium oxide single wafer to form a gallium oxide light absorption layer (14).

9. The method according to claim 7, characterized in that, The fabrication of metal electrodes on the surfaces of the gallium oxide light-absorbing layer (14) and the two-dimensional van der Waals material layer (13) includes: A source electrode (11) is fabricated on the two-dimensional van der Waals material layer (13); A drain electrode (15) is fabricated on the gallium oxide light-absorbing layer (14).

10. The method according to claim 7, characterized in that, The method further includes: A deposition encapsulation layer (12) is formed, which covers the two-dimensional van der Waals material layer (13), the gallium oxide light absorption layer (14), and the metal electrode.

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