A high-density nanoscale dislocation schottky junction diode device and a preparation method thereof

Abstract

The application relates to the field of semiconductor devices, in particular to an alpha-Fe2O3 dislocation / Nb:SrTiO3 high-density nanoscale dislocation Schottky junction diode device and a preparation method thereof, which is suitable for the preparation of one-dimensional conductive Schottky junction devices with multiple sizes, high quality and high density. Nb-doped SrTiO3 (abbreviated as Nb:SrTiO3) is used as the N pole of the Schottky junction, and the penetrating dislocation in the alpha-Fe2O3 film is used as the M pole of the Schottky junction. The preparation method is that alpha-Fe2O3 films are grown on the Nb:SrTiO3 substrate through pulse laser deposition technology at high temperature, high-density penetrating dislocations are grown in the alpha-Fe2O3 film by regulating the interface mismatch, and thus the design of the alpha-Fe2O3 dislocation / Nb:SrTiO3 Schottky junction is realized. The application provides a new idea for the design mode of the Schottky junction diode, and lays a foundation for the development of the new high-density nanoscale dislocation Schottky junction diode device in the fields of photoelectricity, non-volatile storage and transistors.

Description

Technical fields:

[0001] This invention relates to the field of semiconductor devices, specifically to an α-Fe2O3 dislocation / Nb:SrTiO3 high-density nanoscale dislocation Schottky junction diode device and its fabrication method, which is suitable for the fabrication of multi-size, high-quality, and high-density one-dimensional conductive Schottky junction devices. Background technology:

[0002] Dislocations, as one of the common defect types in materials, often have different effects on different types of materials. For metallic structural materials, the interaction between dislocations and phenomena such as dislocation pinning can improve the strength of the material itself. However, for functional materials, especially high-precision semiconductor materials, defects and impurities can affect the normal use and service life of the material. Therefore, the production process of such materials has always been focused on avoiding the introduction of defects and impurities to meet the requirements of market applications. On the other hand, the atomic arrangement around dislocations differs from that of perfect crystals, and dislocations often possess different physical properties than perfect crystals. Therefore, by controlling the dislocation structure, the performance of functional materials can be designed and improved.

[0003] The principle of a Schottky junction is that when a metal (M) and an N-type or P-type semiconductor come into contact, the difference in their band structures creates a unidirectional conductivity, a property commonly used in semiconductor devices. Currently, advancements in diode semiconductor materials are nearing a bottleneck, and the development of alternative materials (e.g., gallium nitride, graphene) has become a research hotspot. Dislocations, as the unit cells of a Schottky junction, offer two major advantages: firstly, the core region of a dislocation is very small, which is crucial for device miniaturization; secondly, lattice mismatch is positively correlated with dislocation density, thus allowing for control of lattice mismatch by selecting the growth substrate, thereby enabling the creation of Schottky junctions with varying densities.

[0004] α-Fe₂O₃, as a type of iron oxide material, is inherently non-conductive. However, the non-stoichiometric ratio at dislocations alters the valence state of Fe atoms at the dislocations, thus producing conductivity similar to Fe₃O₄. Therefore, conductive α-Fe₂O₃ dislocations and an Nb:SrTiO₃ substrate constitute a Schottky junction diode device. This novel device exhibits excellent material property stability, unaffected by reductions in dimensionality and size. Furthermore, both materials are common, and the fabrication process is simple. Therefore, this dislocation Schottky junction not only enables the fabrication of high-density Schottky junction devices but also broadens the scope for future practical applications of dislocations. Summary of the Invention:

[0005] The purpose of this invention is to provide a high-density, chemically uniform, and physically stable α-Fe2O3 dislocation / Nb:SrTiO3 high-density nanoscale dislocation Schottky junction diode device and its fabrication method, which solves the current bottleneck of semiconductor materials and provides a new design concept for Schottky junctions, laying the foundation for the research of novel Schottky junctions and the exploration of their applications.

[0006] The technical solution of this invention is:

[0007] A high-density nanoscale dislocation Schottky junction diode device is disclosed. The diode device consists of an Nb-doped strontium titanate substrate (Nb:SrTiO3) and an α-Fe2O3 thin film deposited on it. Through dislocations are formed inside the α-Fe2O3 thin film. The Nb-doped strontium titanate substrate serves as the N-terminal of the Schottky junction, and the through dislocations in the α-Fe2O3 thin film serve as the M-terminal of the Schottky junction. The α-Fe2O3 thin film itself is an insulating single-crystal thin film, and the through dislocations in the α-Fe2O3 thin film have metallic conductivity. The through dislocations in the α-Fe2O3 thin film combine with the Nb-doped strontium titanate substrate to form a high-density distributed one-dimensional α-Fe2O3 dislocation / Nb:SrTiO3 Schottky junction diode device.

[0008] In the high-density nanoscale dislocation Schottky junction diode device, the dislocations in the α-Fe2O3 thin film are cylindrical with a diameter of 4 to 6 nanometers and a height consistent with the thickness of the α-Fe2O3 thin film.

[0009] The high-density nanoscale dislocation Schottky junction diode device has a fixed crystal orientation between the α-Fe2O3 thin film and the Nb:SrTiO3 substrate, and the crystal orientation relationship is: α-Fe2O3

[1010] / SrTiO3

[110] and α-Fe2O3

[0001] / SrTiO3

[111] .

[0010] The high-density nanoscale dislocation Schottky junction diode device has an Nb-doped strontium titanate substrate that is a perovskite structure material, and the lattice mismatch between the Nb-doped strontium titanate substrate and the α-Fe2O3 thin film is 5.7%.

[0011] The fabrication method of the high-density nanoscale dislocation Schottky junction diode device adopts... <111> An oriented Nb-doped strontium titanate ceramic material was used as the growth substrate to grow an α-Fe2O3 thin film by pulsed laser deposition. After annealing, the film was naturally cooled to obtain a single-crystal α-Fe2O3 thin film.

[0012] The fabrication method of the high-density nanoscale dislocation Schottky junction diode device, using pulsed laser deposition, has the following process parameters: laser energy of 30–400 mJ, frequency of 1 Hz–10 Hz, target material of α-Fe₂O₃, oxygen pressure of 1.0–5.0 Pascals, growth temperature of 600–800 °C, growth time of 1–40 minutes, and the thickness of the α-Fe₂O₃ film, which depends on the deposition time during growth, is 0.5 nm–1000 nm.

[0013] The fabrication method of the high-density nanoscale dislocation Schottky junction diode device includes the following annealing process parameters: the annealing atmosphere is oxygen, the oxygen pressure is 1.0 to 5.0 Pascals, the annealing temperature range is 600 to 800℃, the annealing time is 0.5 hours to 4 hours, and then the temperature is lowered to 200℃ and furnace cooled to room temperature.

[0014] The method for fabricating the high-density nanoscale dislocation Schottky junction diode device has a cooling rate of 2℃ / min to 20℃ / min.

[0015] The method for fabricating the high-density nanoscale dislocation Schottky junction diode device involves the generation of through-dislocations within the α-Fe2O3 thin film grown by pulsed laser deposition due to the lattice mismatch between the α-Fe2O3 thin film and the Nb-doped strontium titanate substrate.

[0016] The fabrication method of the high-density nanoscale dislocation Schottky junction diode device utilizes the lattice mismatch-induced through-dislocations, which exhibit metallic conductivity while the non-dislocation regions are non-conductive. The conductive α-Fe₂O₃ dislocations and the Nb-doped strontium titanate substrate then form a high-density one-dimensional Schottky junction. The Schottky junction density matches the density of the through-dislocations; that is, each through-dislocation forms a Schottky junction with the Nb-doped strontium titanate substrate, with a density ranging from (0.5 to 1.5) × 10⁻⁶. 10 pcs / cm 2 .

[0017] The design concept of this invention is:

[0018] This invention first deposits an α-Fe₂O₃ thin film on an Nb:SrTiO₃ substrate using pulsed laser deposition. The lattice mismatch between the film and the substrate leads to a large number of through-dislocations within the film. The non-stoichiometric ratio within a region of approximately 1 nanometer core diameter at these through-dislocations imparts conductivity, serving as the metal terminals of a Schottky junction. This conductivity combines with the N-type semiconductor Nb:SrTiO₃ substrate to form an α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky structure. This unique Schottky junction structure is formed based on interface dislocations; therefore, the α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky structure combines both small size and high density.

[0019] The advantages and beneficial effects of this invention are:

[0020] 1. This invention proposes a high-density nanoscale dislocation Schottky junction diode device, which has a high-quality α-Fe2O3 dislocation / Nb:SrTiO3 Schottky structure with simple fabrication process and stable physical properties. Its Schottky junction unit size is small and the density is high.

[0021] 2. The high-density nanoscale dislocation Schottky junction diode device obtained in this invention possesses excellent on / off ratio, high density, small size, and high chemical and thermal stability, representing a novel functional device using dislocations as Schottky junction units. These structural and functional characteristics open up new avenues for the research and application of this novel device in optoelectronic devices, non-volatile memory devices, transistors, and sensors.

[0022] 3. The growth method of the α-Fe2O3 dislocation / Nb:SrTiO3 Schottky structure device proposed in this invention is simple, with the characteristics of simple growth, easy control, and the ability to fabricate multiple sizes.

[0023] 4. Compared with other traditional Schottky junction devices, the α-Fe2O3 dislocation / Nb:SrTiO3 Schottky structure device obtained by the present invention has advantages in density and size because it uses dislocations as the unit of the device. For devices requiring the same number of structural units, the dislocation Schottky junction device occupies a smaller area. Attached image description:

[0024] Figure 1 This is a flowchart illustrating the fabrication of an α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky structure device using pulsed laser deposition. Figure a shows... <111> Figure b shows an Nb-doped strontium titanate single crystal substrate. Figure b shows the α-Fe2O3 dislocation / Nb:SrTiO3 Schottky junction formed after growth by pulsed laser deposition technology. Due to lattice mismatch, through-hole dislocations are formed inside the α-Fe2O3 film. Detailed implementation method:

[0025] In the specific implementation process, the fabrication method of the α-Fe2O3 dislocation / Nb:SrTiO3 high-density nanoscale dislocation Schottky junction diode device of the present invention adopts... <111> Using oriented perovskite ceramics as the growth substrate, α-Fe₂O₃ thin films are grown at 700℃ via pulsed laser deposition (PLD) to form α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky junctions. The specific steps are as follows:

[0026] (1) Preparation of α-Fe2O3 thin films: <111> An oriented Nb-doped strontium titanate perovskite material was used as the growth substrate (Nb:STO substrate), and an α-Fe2O3 thin film was grown on the substrate surface using a pulsed laser deposition method.

[0027] The growth substrate used was Nb-doped strontium titanate perovskite, with a lattice mismatch of 5.7% with α-Fe₂O₃, a purity of 99.99 wt%, an orientation of (111) ± 0.3°, and a polished surface with a surface roughness ≤ 0.5 nm. The pulsed laser deposition growth was performed using a COMPex-201 laser with a wavelength of 248 nm and a pulse width of 25 ns. The laser energy was 30–400 mJ, preferably 40 mJ–300 mJ; the frequency was 1 Hz–10 Hz, preferably 3 Hz–5 Hz. The growth target was α-Fe₂O₃ with a purity of 99.99 wt%; the oxygen pressure was 1.0–5.0 Pascals, preferably 1.0–3.0 Pascals. The growth temperature range is 600–800℃, with a preferred range of 650–750℃; the growth time is 1–40 minutes, with a preferred range of 5–30 minutes.

[0028] (2) The annealing atmosphere is oxygen, the oxygen pressure is 1.0 to 5.0 Pascals, preferably 1.0 to 3.0 Pascals, the annealing temperature range is 600 to 800℃, preferably 650 to 750℃, and the annealing time is 0.5 to 4 hours, preferably 0.5 to 3 hours; then the temperature is lowered to 200℃ at a rate of 2℃ / min to 20℃ / min, preferably 4℃ / min to 10℃ / min; then the furnace is cooled to room temperature.

[0029] The novel α-Fe2O3 dislocation / Nb:SrTiO3 Schottky junction obtained by the present invention has an α-Fe2O3 film with a thickness of 0.5nm to 1000nm (preferably 5nm to 100nm) and uniform composition. Through dislocations are generated in the film due to the mismatch between the film and the substrate.

[0030] The present invention will now be described in further detail with reference to embodiments and accompanying drawings.

[0031] Example 1

[0032] like Figure 1 As shown, the α-Fe2O3 dislocation / Nb:SrTiO3 high-density nanoscale dislocation Schottky junction diode device and its fabrication method are as follows:

[0033] First, this invention uses pulsed laser deposition and heat treatment to prepare α-Fe2O3 thin films, with a pulsed laser energy of 50 mJ and a pulse frequency of 5 Hz; the substrate is selected as follows. <111> Nb-doped strontium titanate (10 mm × 10 mm × 0.5 mm, purity 99.99 wt%, abbreviated as Nb:SrTiO3), Figure 1 STO (strontium titanate) was placed in the central region of the sample holder in the cavity, 8 cm away from the α-Fe₂O₃ target (25 mm in diameter, 6 mm in thickness, 99.99 wt% purity). The α-Fe₂O₃ film was grown at 700 °C under 1.0 Pa oxygen pressure for 30 minutes. After growth, it was annealed for 0.5 hours at the same temperature and oxygen pressure, cooled to 200 °C at a rate of 10 °C / min, and then furnace cooled to room temperature to obtain the α-Fe₂O₃ film. Transmission electron microscopy analysis of the film morphology and crystal orientation showed that the film was 50 nm thick, composed of a single α-Fe₂O₃ phase, and had good crystal quality. Due to interfacial mismatch, through-dislocations were generated inside the film. These through-dislocations were cylinders with a diameter of 5 nm and a height consistent with the film thickness. The density of through-dislocations was approximately 10-1. 10 pcs / cm 2 The Schottky junction density is consistent with the density of through dislocations, meaning that each through dislocation forms a Schottky junction with the Nb-doped strontium titanate substrate. Furthermore, the α-Fe2O3 film and the Nb:SrTiO3 substrate have a fixed crystal orientation, with the crystal orientation relationships being: α-Fe2O3[10 10] / SrTiO3

[110] and α-Fe2O3

[0001] / SrTiO3

[111] . These two orientation relationships correspond to two perpendicular directions, and their physical properties are stable and their composition is uniform.

[0034] The conductivity of this α-Fe₂O₃ / Nb:SrTiO₃ thin film system was then tested using a conductivity atomic force microscope (AFM). Conductivity testing was performed on a 2 μm × 2 μm area, revealing point-like conductive spots under positive voltage and virtually no conductivity under negative voltage. This confirmed the unidirectional conductivity of the α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky junction. Subsequent IV curve analysis of a single conductive spot also demonstrated the characteristic curve features of a Schottky junction, further confirming the formation of the α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky junction.

[0035] Example 2

[0036] like Figure 1As shown, the α-Fe2O3 dislocation / Nb:SrTiO3 high-density nanoscale dislocation Schottky junction diode device and its fabrication method are as follows:

[0037] First, this invention uses pulsed laser deposition and heat treatment to prepare α-Fe2O3 thin films, with a pulsed laser energy of 50 mJ and a pulse frequency of 5 Hz; the substrate is selected as follows. <111> Nb-doped strontium titanate (10 mm × 10 mm × 0.5 mm, 99.99 wt% purity) was placed in the central region of the cavity sample holder, 8 cm away from the α-Fe₂O₃ target (25 mm diameter, 6 mm thickness, 99.99 wt% purity). The α-Fe₂O₃ film was grown at 750 °C under 1.0 Pa oxygen pressure for 60 minutes. After growth, the film was annealed for 0.5 hours at the same temperature and oxygen pressure, cooled to 200 °C at a rate of 10 °C / min, and then furnace cooled to room temperature to obtain the α-Fe₂O₃ film. Transmission electron microscopy analysis of the film morphology and crystal orientation showed that the film was 100 nm thick, composed of a single α-Fe₂O₃ phase, and had good crystal quality. Due to interfacial mismatch, through-dislocations were generated within the film. These through-dislocations were cylinders with a diameter of 5 nm and a height consistent with the film thickness. The density of through-dislocations was approximately 10-1. 10 pcs / cm 2 The Schottky junction density is consistent with the density of through dislocations, meaning that each through dislocation forms a Schottky junction with the Nb-doped strontium titanate substrate. Furthermore, the α-Fe2O3 film and the Nb:SrTiO3 substrate have a fixed crystal orientation, with the crystal orientation relationships being: α-Fe2O3[10 10] / SrTiO3

[110] and α-Fe2O3

[0001] / SrTiO3

[111] . These two orientation relationships correspond to two perpendicular directions, and their physical properties are stable and their composition is uniform.

[0038] The conductivity of the α-Fe₂O₃ / Nb:SrTiO₃ thin film system was then tested using a conductivity atomic force microscope (AFM). Conductivity testing was performed over a 3 μm × 3 μm area, revealing point-like conductive spots under positive voltage and virtually no conductivity under negative voltage. This confirmed the unidirectional conductivity of the α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky junction. Subsequent IV curve analysis of a single conductive spot also demonstrated the characteristic curve features of a Schottky junction, further confirming the formation of the α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky junction.

[0039] The above results demonstrate that this invention achieves the fabrication of α-Fe₂O₃ dislocation / Nb:SrTiO₃ Schottky structure devices with tunable, stable properties, uniform crystal orientation, and excellent performance through pulsed laser deposition technology. Subsequent conductive atomic force microscopy also confirmed the unidirectional conductivity of the Schottky junction. This novel high-density Schottky junction device has a simple fabrication process, and the device thickness and Schottky junction density are easily controllable, thus laying the foundation for the research and application of this novel semiconductor device in optoelectronic devices, transistors, and sensor devices.

Claims

1. A method for fabricating a high-density nanoscale dislocation Schottky junction diode device, characterized in that, This diode device consists of an Nb-doped strontium titanate substrate (Nb:SrTiO3) and an α-Fe2O3 thin film deposited on it. Through dislocations are formed inside the α-Fe2O3 thin film. The Nb-doped strontium titanate substrate serves as the N-terminal of the Schottky junction, and the through dislocations in the α-Fe2O3 thin film serve as the M-terminal of the Schottky junction. The α-Fe2O3 thin film itself is an insulating single-crystal thin film, and the through dislocations in the α-Fe2O3 thin film have metallic conductivity. The through dislocations in the α-Fe2O3 thin film combine with the Nb-doped strontium titanate substrate to form a high-density distributed one-dimensional α-Fe2O3 dislocation / Nb:SrTiO3 Schottky junction diode device. The Nb-doped strontium titanate substrate is a perovskite structure material, and the lattice mismatch between the Nb-doped strontium titanate substrate and the α-Fe2O3 thin film is 5.7%. The fabrication method of the high-density nanoscale dislocation Schottky junction diode device adopts... <111> Using oriented Nb-doped strontium titanate ceramic material as the growth substrate, α-Fe2O3 thin films were grown by pulsed laser deposition, and after annealing and natural cooling, single-crystal α-Fe2O3 thin films were obtained. The process parameters of the pulsed laser deposition method are as follows: laser energy is 30-400 mJ, frequency is 1 Hz-10 Hz, the target material used for growth is α-Fe2O3 target, the oxygen pressure used for growth is 1.0-5.0 Pascal, the growth temperature range is 600-800℃, the growth time is 1-40 minutes, and the thickness of the α-Fe2O3 film depends on the deposition time during the growth process, with the thickness of the α-Fe2O3 film ranging from 0.5 nm to 1000 nm. The annealing process parameters are as follows: the annealing atmosphere is oxygen, the oxygen pressure is 1.0 to 5.0 Pascals, the annealing temperature range is 600 to 800℃, the annealing time is 0.5 hours to 4 hours, then the temperature is lowered to 200℃ and furnace cooled to room temperature; First, an α-Fe2O3 thin film was deposited on an Nb:SrTiO3 substrate using pulsed laser deposition. The lattice mismatch between the film and the substrate led to the generation of a large number of through dislocations in the film. The non-stoichiometry within a region with a core diameter of 1 nanometer at these through dislocations made the dislocations conductive. As the metal end of the Schottky junction, it was combined with the N-type semiconductor Nb:SrTiO3 substrate to form an α-Fe2O3 dislocation / Nb:SrTiO3 Schottky structure.

2. The method for fabricating a high-density nanoscale dislocation Schottky junction diode device according to claim 1, characterized in that, In α-Fe2O3 films, the penetrating dislocations are cylindrical structures with a diameter of 4–6 nanometers, and their height is consistent with the thickness of the α-Fe2O3 film.

3. The method of making a high-density nanoscale dislocation Schottky junction diode device according to claim 1, wherein The a-Fe2O3 thin film has a fixed crystal orientation with the Nb:SrTiO3 substrate, and the crystal orientation relationship is: and a-Fe2O3 [0001] / SrTiO3 [111].

4. The method of making a high-density nanoscale dislocation Schottky junction diode device according to claim 1, wherein, The cooling rate is 2℃ / minute to 20℃ / minute.

5. The method of making a high-density nanoscale dislocation Schottky junction diode device according to claim 1, wherein In the α-Fe2O3 thin film grown by pulsed laser deposition, through-hole dislocations are generated in the α-Fe2O3 thin film due to the lattice mismatch between the α-Fe2O3 thin film and the Nb-doped strontium titanate substrate.

6. The method of making a high-density nanoscale dislocation Schottky junction diode device according to claim 1, wherein The threading dislocations produced by the lattice mismatch exhibit metallic conductivity, while the dislocation-free regions are non-conductive. The conductive a-Fe2O3 dislocations and the Nb-doped strontium titanate substrate form a high density of one-dimensional distributed Schottky junctions. The density of the Schottky junctions is consistent with the density of the threading dislocations, i.e. each threading dislocation forms a Schottky junction with the Nb-doped strontium titanate substrate, with a density in the range of (0.5-1.5) x 10 10 / cm 2 .

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