PN junction detector based on N-type germanium substrate and preparation method

Abstract

The invention discloses a PN junction detector based on an N-type germanium substrate and a preparation method, and relates to the technical field of microelectronics, and the PN junction detector comprises an N-type Ge substrate, a P-type Ge region formed in the substrate, a P + ohmic contact region located on the surface of the P-type Ge region, an N + ohmic contact region located on the bottom surface of the substrate, and corresponding metal electrodes. According to the detector, a longitudinal PN junction and a double heavily doped contact structure are adopted, near-infrared light is fully absorbed by using a body germanium substrate, and high responsivity is realized; and meanwhile, an electric field is built in the PN junction to effectively separate photon-generated carriers, so that the dark current is obviously reduced, and the detection sensitivity is improved. The preparation technology of the PN junction detector is compatible with the silicon-based CMOS technology, a complex epitaxial process is not needed, and the PN junction detector has the advantages of being low in cost and high in integration degree and is particularly suitable for near-infrared detection application in the fields of optical communication, sensing and imaging.

Description

Technical Field

[0001] This invention belongs to the field of microelectronics technology, specifically relating to a PN junction detector based on an N-type germanium substrate and its fabrication method. Background Technology

[0002] Near-infrared photodetectors play a crucial role in applications such as optical communication, sensing, and imaging. Currently, high-performance near-infrared detectors primarily utilize indium gallium arsenide (InGaAs) materials, exhibiting high responsivity and sensitivity in the 1550nm communication band. However, InGaAs detectors are costly to fabricate, requiring complex heteroepitaxial growth processes, and are difficult to integrate with mainstream silicon-based CMOS technology, limiting their application in large-scale, low-cost integrated systems. In recent years, colloidal quantum dot (e.g., PbS quantum dot) detectors have attracted attention due to their advantages such as solution-processability and lower cost. However, these devices still suffer from insufficient stability, low carrier mobility, and difficulties in integration with silicon processes, and their performance and reliability are still insufficient to meet commercialization requirements.

[0003] Germanium (Ge) is considered an ideal candidate material for achieving low-cost, high-performance on-chip optoelectronic integration due to its excellent light absorption characteristics in the near-infrared band (up to 1850 nm) and its fabrication process being highly compatible with silicon-based CMOS processes. However, traditional Ge-based photodetectors still face challenges in structural design. Taking metal-semiconductor-metal (MSM) structures as an example, these devices typically suffer from excessive dark current, leading to a decrease in overall device sensitivity.

[0004] To overcome this deficiency, existing technologies attempt to epitaxially grow Ge material on a lateral Si-based PIN structure, utilizing Si to suppress dark current while the Ge layer is responsible for infrared light detection. However, due to the thinness of the epitaxial Ge layer, its absorption capacity for near-infrared light is limited, resulting in a significant reduction in device responsivity. Existing Ge-based detectors struggle to balance dark current and responsivity, limiting their application in high-efficiency, high-sensitivity near-infrared detection systems. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a PN junction detector based on an N-type germanium substrate and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a PN junction detector based on an N-type germanium substrate, comprising: N-type Ge substrate; The P-type Ge region is located within the N-type Ge substrate and close to the top surface of the N-type Ge substrate, forming a PN junction with the N-type Ge substrate; The P+ ohmic contact region is located within the P-type Ge region and close to the top surface of the N-type Ge substrate; The N+ ohmic contact region is located on the bottom surface of the N-type Ge substrate; The first metal electrode is located on the P+ ohmic contact region and forms an ohmic contact with the P+ ohmic contact region; The second metal electrode is located on the N+ ohmic contact region and forms an ohmic contact with the N+ ohmic contact region.

[0006] In one embodiment of the present invention, the doping concentration of the P+ ohmic contact region is higher than the doping concentration of the P-type Ge region.

[0007] In one embodiment of the present invention, the doping concentration of the N+ ohmic contact region is higher than the doping concentration of the N-type Ge substrate.

[0008] In one embodiment of the present invention, the resistivity of the N-type Ge substrate does not exceed 10 Ω·cm.

[0009] In one embodiment of the present invention, the thickness of the N-type Ge substrate is 300-500 μm.

[0010] In one embodiment of the present invention, the doping concentration of the p-type Ge region is 1×10⁻⁶. 18 -1×10 19 cm -3 The ion implantation depth is 300-500 nm.

[0011] In one embodiment of the present invention, the doping concentration of the P+ ohmic contact region is 1×10⁻⁶. 19 -1×10 20 cm -3 The ion implantation depth is 100-200 nm.

[0012] In one embodiment of the present invention, the doping concentration of the N+ ohmic contact region is 1×10⁻⁶. 19 -1×10 20 cm -3 The ion implantation depth is 100-200 nm.

[0013] In one embodiment of the present invention, the materials of the first metal electrode and the second metal electrode are gold, silver or aluminum.

[0014] This invention provides a method for fabricating a PN junction detector based on an N-type germanium substrate, applicable to the PN junction detector based on an N-type germanium substrate described in any of the above embodiments. The fabrication method includes: Step 1: Select an N-type Ge substrate; Step 2: Perform ion implantation or diffusion process on the top surface of the N-type Ge substrate to form a P-type Ge region, wherein the P-type Ge region and the N-type Ge substrate form a PN junction; Step 3: Perform ion implantation or diffusion on the top surface of the P-type Ge region to form a P+ ohmic contact region; Step 4: Perform ion implantation or diffusion process on the bottom surface of the N-type Ge substrate to form an N+ ohmic contact region; Step 5: Electrode deposition is performed on the surfaces of the P+ ohmic contact region and the N+ ohmic contact region to form a first metal electrode and a second metal electrode.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The PN junction detector based on an N-type germanium substrate of this invention employs a vertical PN junction structure, fundamentally avoiding the excessive dark current defect caused by the low Schottky barrier in traditional germanium-based metal-semiconductor-metal structures. The depletion region formed by the PN junction under reverse bias effectively suppresses the thermal emission and generation-recombination processes of charge carriers, thereby significantly reducing dark current and improving the signal-to-noise ratio and sensitivity of the device, enabling it to detect weaker optical signals. Simultaneously, this structure directly uses a bulk N-type germanium substrate as the light absorption layer, with a thickness much greater than the penetration depth of near-infrared light in germanium, enabling sufficient absorption of incident photons and overcoming the problems of insufficient absorption and decreased responsivity caused by epitaxial thin germanium layers on silicon. Furthermore, photogenerated electrons, as majority carriers, drift rapidly in the high-mobility N-type substrate and are collected by the bottom electrode, contributing to improved overall device response speed and meeting the requirements of high-speed optical communication applications.

[0016] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a PN junction detector based on an N-type germanium substrate provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a method for fabricating a PN junction detector based on an N-type germanium substrate provided in an embodiment of the present invention.

[0018] Icons: 1-N-type Ge substrate; 2-P-type Ge region; 3-P+ ohmic contact region; 4-N+ ​​ohmic contact region; 5-First metal electrode; 6-Second metal electrode. Detailed Implementation

[0019] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for preparing a PN junction detector based on an N-type germanium substrate and its fabrication.

[0020] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0021] In a first aspect, embodiments of the present invention provide a PN junction detector based on an N-type germanium substrate, see [link to previous document]. Figure 1 , Figure 1 This is a schematic diagram of a PN junction detector based on an N-type germanium substrate provided in an embodiment of the present invention. Figure 1 As shown, the PN junction detector based on an N-type germanium substrate in this embodiment includes: an N-type Ge substrate 1, a P-type Ge region 2, a P+ ohmic contact region 3, an N+ ohmic contact region 4, a first metal electrode 5, and a second metal electrode 6. The P-type Ge region 2 is located within the N-type Ge substrate 1 and near its top surface, forming a PN junction with the N-type Ge substrate 1; the P+ ohmic contact region 3 is located within the P-type Ge region 2 and near its top surface; the N+ ohmic contact region 4 is located on the bottom surface of the N-type Ge substrate 1; the first metal electrode 5 is located on the P+ ohmic contact region 3, forming an ohmic contact with it; and the second metal electrode 6 is located on the N+ ohmic contact region 4, forming an ohmic contact with it.

[0022] In this embodiment, the doping concentration of the P+ ohmic contact region 3 is higher than that of the P-type Ge region 2. The doping concentration of the N+ ohmic contact region 4 is higher than that of the N-type Ge substrate 1.

[0023] In this embodiment, the N-type Ge substrate 1 serves as the mechanical support for the device and the collection and transport channel for photogenerated carriers (electrons). Optionally, the resistivity of the N-type Ge substrate 1 does not exceed 10 Ω·cm. The doping concentration and resistivity of the N-type Ge substrate 1 are negatively correlated; that is, the higher the doping concentration, the lower the resistivity. However, excessively high resistivity will increase the device's series resistance, affecting the response speed, while excessively low resistivity will increase the device's dark current due to the increased depletion region width, reducing sensitivity. To achieve a balance between low dark current and low series resistance, the N-type Ge substrate 1 can be selected with a medium or low doping concentration.

[0024] For example, the doping concentration of the N-type Ge substrate 1 can be 1 × 10⁻⁶. 15cm -3 -1×10 17 cm -3 This ensures that the device has a sufficiently wide light absorption depletion region and low dark current.

[0025] Optionally, the thickness of the N-type Ge substrate 1 is 300-500 μm. The thickness of 300-500 μm ensures that the substrate has good mechanical strength, can withstand subsequent processing, and provides sufficient light absorption path for near-infrared light, especially in the 1550 nm band, ensuring high quantum efficiency.

[0026] In this embodiment, the P-type Ge region 2 can be formed on the top surface region of the N-type Ge substrate 1 through ion implantation or diffusion processes. The P-type Ge region 2 and the N-type Ge substrate 1 together form a PN junction, which is the core region for the separation of photogenerated carriers.

[0027] Optionally, the doping concentration of the p-type Ge region 2 is 1×10⁻⁶. 18 -1×10 19 cm -3 For example, it could be 5×10 18 cm -3 This doping concentration ensures that the PN junction can form a sufficiently strong built-in electric field to efficiently separate photogenerated electron-hole pairs.

[0028] Optionally, the ion implantation depth of the P-type Ge region 2 is 300-500 nm to ensure that the P-region has sufficient thickness to form good contact with the metal electrode, and to allow its depletion region to extend sufficiently into the light absorption region of the N-type Ge substrate 1, thereby achieving efficient light absorption and carrier separation simultaneously.

[0029] In this embodiment, the P+ ohmic contact region 3 can be formed in the top surface region of the P-type Ge region 2 by ion implantation or diffusion process, and its doping concentration is significantly higher than that of the P-type Ge region 2.

[0030] Optionally, the doping concentration of the P+ ohmic contact region 3 is 1×10⁻⁶. 19 -1×10 20 cm -3 For example, it could be 5×10 19 cm -3 The ion implantation depth is 100-200 nm.

[0031] In this embodiment, by forming a P++ heavily doped P+ ohmic contact region 3, the Schottky barrier width of the metal-semiconductor contact can be significantly reduced. Charge carriers (holes) mainly tunnel through the extremely thin barrier, thereby forming an ideal low-resistance ohmic contact. This effectively reduces the series resistance and heat loss during device operation, improving the overall efficiency and lifespan of the detector.

[0032] In this embodiment, the N+ ohmic contact region can be formed on the entire bottom surface of the N-type Ge substrate 1 by ion implantation or diffusion processes, and its doping concentration is significantly higher than that of the N-type Ge substrate 1.

[0033] Optionally, the doping concentration of the N+ ohmic contact region 4 is 1×10⁻⁶. 19 -1×10 20 cm -3 For example, it could be 5×10 19 cm -3 The ion implantation depth is 100-200 nm.

[0034] Similar to P++ heavy doping, the N++ heavy doping N+ ohmic contact region 4 can form an excellent ohmic contact with the back electrode. This double-heavy-doped ohmic contact design is key to achieving both high performance and process simplicity. It avoids the use of complex alloying processes or special metal systems, and can be achieved simply through standard ion implantation and annealing, making it highly compatible with CMOS processes.

[0035] In this embodiment, the first metal electrode 5 and the second metal electrode 6 are formed on the P+ ohmic contact region 3 and the N+ ohmic contact region 4 by physical vapor deposition processes such as evaporation. The electrode materials can be gold (Au), silver (Ag), or aluminum (Al), etc.

[0036] Understandably, Al is an ideal electrode material for the P+ ohmic contact region 3 because aluminum is a P-type impurity, which can naturally form a good ohmic contact with the P+ ohmic contact region 3, and it is also inexpensive. For the N+ ohmic contact region 4, a composite structure can be used, in which nickel (Ni) is first deposited and then annealed to form nickel germanide (NiGe) as the contact layer, and then gold (Au) is deposited as the conductive and bonding layer.

[0037] For the PN junction detector based on an N-type germanium substrate in this embodiment of the invention, when near-infrared light (e.g., 1550 nm) is incident from the top of the device, passes through the P-type Ge region 2, and enters the depletion region and quasi-neutral region of the N-type Ge substrate 1, photons are absorbed and electron-hole pairs are generated. Under the influence of the built-in electric field of the PN junction, photogenerated electrons are swept toward the N-type Ge substrate 1 and are eventually collected by the second metal electrode 6 at the bottom; while photogenerated holes are swept toward the P-type Ge region 2 and are eventually collected by the first metal electrode 5 at the top, thereby forming a photocurrent signal in the external circuit. Since electrons have high mobility in the N-type Ge substrate 1, they can be quickly collected by the second metal electrode 6, which helps to improve the response speed of the device.

[0038] The PN junction detector based on an N-type germanium substrate of this invention employs a vertical PN junction structure, fundamentally avoiding the excessive dark current defect caused by the low Schottky barrier in traditional germanium-based metal-semiconductor-metal structures. The depletion region formed by the PN junction under reverse bias effectively suppresses the thermal emission and generation-recombination processes of charge carriers, thereby significantly reducing dark current and improving the signal-to-noise ratio and sensitivity of the device, enabling it to detect weaker optical signals. Simultaneously, this structure directly uses a bulk N-type germanium substrate as the light absorption layer, with a thickness much greater than the penetration depth of near-infrared light in germanium. This allows for sufficient absorption of incident photons, overcoming the problems of insufficient absorption and decreased responsivity caused by epitaxial thin germanium layers on silicon. This achieves high quantum efficiency and high responsivity in the 850-1850nm wavelength range, especially in the 1550nm communication window. Furthermore, photogenerated electrons, as majority carriers, drift rapidly in the high-mobility N-type substrate and are collected by the bottom electrode, contributing to improved overall device response speed and meeting the requirements of high-speed optical communication applications.

[0039] Furthermore, in terms of electrode contact design, by constructing heavily doped regions of P++ and N++ on the back side of the P-type Ge region and the N-type Ge substrate respectively, a low-resistance ohmic contact with the metal electrode is achieved by utilizing the tunneling effect induced by high-concentration doping. This design effectively reduces the device's series resistance and Joule heat loss during operation, not only improving the stability of electrical performance but also enhancing the device's reliability under long-term operating conditions. This invention, through a single homojunction and optimized doping distribution, successfully achieves both low dark current and high responsivity—performance indicators difficult to simultaneously realize in traditional germanium-based or silicon-based epitaxial detectors—providing a cost-effective solution for near-infrared light detection that is balanced in performance, simple in fabrication, and easy to integrate.

[0040] Secondly, embodiments of the present invention provide a method for fabricating a PN junction detector based on an N-type germanium substrate, applicable to the PN junction detector based on an N-type germanium substrate provided in the first aspect.

[0041] Please see Figure 2 , Figure 2 This is a schematic diagram of a method for fabricating a PN junction detector based on an N-type germanium substrate according to an embodiment of the present invention, as shown below. Figure 2 As shown, the fabrication method of the PN junction detector based on an N-type germanium substrate of the present invention includes the following steps: Step 1: Select an N-type Ge substrate.

[0042] Optionally, an N-type single-crystal germanium wafer with a resistivity not exceeding 10 Ω·cm and a thickness of 300-500 μm can be selected and subjected to standard cleaning.

[0043] Step 2: Perform ion implantation or diffusion on the top surface of the N-type Ge substrate to form a P-type Ge region. The P-type Ge region and the N-type Ge substrate form a PN junction.

[0044] Alternatively, p-type impurities such as boron (B) or indium (In) can be implanted onto the top surface of the N-type Ge substrate using an ion implanter. Subsequent thermal annealing processes activate the impurities and advance the junction depth, ultimately resulting in a doping concentration of approximately 5 × 10⁻⁶. 18 cm -3 A P-type Ge region with a depth of 300-500 nm.

[0045] Step 3: Perform ion implantation or diffusion on the top surface of the P-type Ge region to form a P+ ohmic contact region.

[0046] The doping concentration of the P+ ohmic contact region is higher than that of the P-type Ge region. Optionally, an implantation region can be defined on the surface of the P-type Ge region using a photoresist mask, followed by high-dose P-type impurity ion implantation. For example, boron (B) can be implanted to a depth of 100-200 nm with a concentration of 5 × 10⁻⁶ ions. 19 cm -3 The P+ ohmic contact region. Selective implantation here ensures that the ohmic contact region is precisely confined below the electrode, avoiding unnecessary device performance degradation.

[0047] Step 4: Perform ion implantation or diffusion on the bottom surface of the N-type Ge substrate to form an N+ ohmic contact region.

[0048] The doping concentration of the N+ ohmic contact region is higher than that of the N-type Ge substrate. Alternatively, the entire device can be flipped over, and a high dose of N-type impurity (such as phosphorus P or arsenic As) ions can be implanted onto the entire bottom surface of the N-type Ge substrate. The formation depth is 100-200 nm, and the concentration is 5 × 10⁻⁶. 19 cm -3 The N+ ohm contact area is formed. This step creates a global contact on the back of the device, which greatly reduces the contact resistance of the entire back electrode and facilitates uniform collection of photocurrent.

[0049] Step 5: Perform electrode evaporation on the surfaces of the P+ ohmic contact region and the N+ ohmic contact region to form the first metal electrode and the second metal electrode.

[0050] Optionally, a rapid thermal annealing (RTA) process can be performed first to activate all implanted impurities and repair lattice damage. Then, metal layers (such as Al or Ni / Au) are deposited on the top surface (covering the P+ ohmic contact region) and bottom surface of the device by electron beam evaporation or magnetron sputtering, respectively, and patterned by photolithography and etching processes to finally form the first metal electrode and the second metal electrode.

[0051] The method for fabricating a PN junction detector based on an N-type germanium substrate, as described in this invention, employs standard and mature silicon-based CMOS processes for ion implantation, annealing, thin film deposition, and patterning. This allows the detector structure proposed in this invention to be seamlessly integrated into existing semiconductor manufacturing platforms, laying a solid technological foundation for the low-cost, high-volume production of high-performance near-infrared photodetectors and solving the problems of high cost and incompatibility with CMOS in existing InGaAs detectors.

[0052] For details regarding the fabrication method of the PN junction detector based on an N-type germanium substrate and its corresponding beneficial effects, please refer to the relevant content on the PN junction detector based on an N-type germanium substrate provided in the first aspect; it will not be repeated here.

[0053] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes that element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0055] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A PN junction detector based on an N-type germanium substrate, characterized in that, include: N-type Ge substrate (1); The P-type Ge region (2) is located inside the N-type Ge substrate (1) and close to the top surface of the N-type Ge substrate, forming a PN junction with the N-type Ge substrate (1); The P+ ohmic contact region (3) is located within the P-type Ge region (2) and close to the top surface of the N-type Ge substrate (1); The N+ ohmic contact region (4) is located on the bottom surface of the N-type Ge substrate (1); The first metal electrode (5) is located on the P+ ohmic contact region (3) and forms an ohmic contact with the P+ ohmic contact region (3); The second metal electrode (6) is located on the N+ ohmic contact region (4) and forms an ohmic contact with the N+ ohmic contact region (4).

2. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The doping concentration of the P+ ohmic contact region (3) is higher than that of the P-type Ge region (2).

3. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The doping concentration of the N+ ohmic contact region (4) is higher than that of the N-type Ge substrate (1).

4. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The resistivity of the N-type Ge substrate (1) does not exceed 10 Ω·cm.

5. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The thickness of the N-type Ge substrate (1) is 300-500 μm.

6. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The doping concentration of the P-type Ge region (2) is 1×10⁻⁶. 18 -1×10 19 cm -3 The ion implantation depth is 300-500 nm.

7. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The doping concentration of the P+ ohmic contact region (3) is 1×10⁻⁶. 19 -1×10 20 cm -3 The ion implantation depth is 100-200 nm.

8. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The doping concentration of the N+ ohmic contact region (4) is 1×10⁻⁶. 19 -1×10 20 cm -3 The ion implantation depth is 100-200 nm.

9. The PN junction detector based on an N-type germanium substrate according to claim 1, characterized in that, The first metal electrode (5) and the second metal electrode (6) are made of gold, silver or aluminum.

10. A method for fabricating a PN junction detector based on an N-type germanium substrate, characterized in that, The method for fabricating the PN junction detector based on an N-type germanium substrate according to any one of claims 1-9 includes: Step 1: Select an N-type Ge substrate; Step 2: Perform ion implantation or diffusion process on the top surface of the N-type Ge substrate to form a P-type Ge region, wherein the P-type Ge region and the N-type Ge substrate form a PN junction; Step 3: Perform ion implantation or diffusion on the top surface of the P-type Ge region to form a P+ ohmic contact region; Step 4: Perform ion implantation or diffusion process on the bottom surface of the N-type Ge substrate to form an N+ ohmic contact region; Step 5: Electrode deposition is performed on the surfaces of the P+ ohmic contact region and the N+ ohmic contact region to form a first metal electrode and a second metal electrode.

Images