SEMICONDUCTOR MATERIAL PROVIDED WITH Ru CHALCOGENIDE THIN FILM AND METHOD OF PRODUCING SEMICONDUCTOR MATERIAL

Abstract

To provide a semiconductor material capable of exhibiting applicability with respect to a near infrared region and a shortwave infrared region.SOLUTION: There is provided a semiconductor material including a substrate and a semiconductor thin film formed on the substrate. The semiconductor thin film comprises an Ru chalcogenide that comprises Ru, and Se and S which each are a chalcogen element and that is shown in the following formula, and the film thickness of the semiconductor thin film is 10 nm or more and 100 nm or less. The semiconductor material may exhibit responsibility to light in a wavelength region of 900 nm or more and 2,500 nm or less. (In the formula, x and y represent a ratio of the number of Se atoms and a ratio of the number of S atoms to the number of Ru atoms, respectively, x and y are real numbers satisfying 0<x<2.0 and 0<y<1.9, respectively, and x and y satisfy 1.9<x+y<2.0.)SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a semiconductor material used for the light-receiving layer of an optical sensor, etc. In particular, the present invention relates to a semiconductor material in which a thin film of a transition metal chalcogenide made of Ru, Se, and S is formed as a semiconductor film on a substrate. [Background technology]

[0002] LiDAR (Light Detection and Ranging), an example of the application of remote sensing technology that uses light, is a system that detects the distance and angle to an object by irradiating the object with laser light and detecting the reflected light with a light-receiving element. LiDAR has the advantage of being able to detect the distance and angle to an object with high precision compared to detection systems using cameras or millimeter-wave radar. Until now, LiDAR has mainly been considered and used as a control system for automobiles, drones, ships, etc., but recently it has also been applied to facial recognition technology and augmented reality (AR) technology in smartphones and tablets.

[0003] The optical sensors used in LiDAR are capable of detecting light in a wide range of wavelengths, including ultraviolet, visible, and near-infrared regions, but what is currently particularly important is support for the near-infrared (NIR) and shortwave infrared (SWIR) regions. This is due to the recent development of autonomous driving technology. As the level of autonomous driving increases, it will be necessary to support levels 4 and 5, which do not assume a driver is driving the vehicle. In such cases, it is important for LiDAR to have response in wavelength regions that are less affected by sunlight and natural light.

[0004] Regarding the light receiving layer of optical sensors such as LiDAR, HgCdTe alloy (Hg 1-X CD X Te alloy: MCT alloy) and InGaAs alloy (In 1-X Ga XAs alloys) can be cited (for example, Patent Document 1 and Patent Document 2). These semiconductor alloys have responsiveness in the wavelength region of 1 μm to 30 μm by appropriately adjusting the composition (x).

[0005] However, HgCdTe alloys and InGaAs alloys pose problems in terms of manufacturing costs. In order to manufacture these semiconductor materials with the desired composition, it is necessary to use MBE (molecular beam epitaxy). MBE film formation requires an ultra-high vacuum atmosphere, and the film formation speed is slow, resulting in poor manufacturing efficiency. Furthermore, MBE is limited in the materials that can be used for substrates, and the substrate costs are high. These cost issues are a barrier to the widespread use of LiDAR.

[0006] Furthermore, HgCdTe alloys have a low N ratio at room temperature, raising concerns about noise generation and requiring the addition of a cooling mechanism. This hinders their application in automotive equipment, which must be operated at room temperature, and drones, which require miniaturization. Furthermore, InGaAs alloys also have problems with poor responsiveness at room temperature, as well as high operating voltages and structural instability.

[0007] Therefore, the application of transition metal chalcogenides has been proposed as a suitable semiconductor material for optical sensors such as LiDAR. Transition metal chalcogenides are compounds of transition metals from Group 3 to Group 11 elements and chalcogen elements (S (sulfur), Se (selenium), Te (tellurium), etc.) excluding O (oxygen). Transition metal chalcogenides are known to exhibit unique electrical and optical semiconductor properties based on the properties of the central metal.

[0008] Transition metal chalcogenide light-receiving layers have been reported to exhibit low noise at room temperature, solving the characteristic problems of HgCdTe alloys and other materials. Furthermore, transition metal chalcogenides can be manufactured using various thin-film deposition processes currently used industrially, and are particularly compatible with chemical vapor deposition (CVD) and atomic layer deposition (ALD). Chemical vapor deposition does not require the high vacuum required by MBE, and by setting appropriate reaction conditions, it also offers excellent control over the deposition rate. Furthermore, chemical vapor deposition offers a wide range of substrate materials, including glass substrates in addition to silicon. Given these advantages in cost and performance, transition metal chalcogenide semiconductor materials are considered to be cost-effective options for the light-receiving layer of optical sensors.

[0009] As an example of the application of transition metal chalcogenides to light-receiving layers, the applicant of the present application has proposed, for example, in Patent Document 3, a semiconductor film made of transition metal chalcogenides of the precious metals Pt (platinum) and Pd (palladium), and has disclosed a semiconductor material that has potential applicability to LiDAR. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Special Publication No. 6-9240 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-165359 [Patent Document 3] Special Publication No. 2018-525516 Summary of the Invention [Problem to be solved by the invention]

[0011] In the above-mentioned Patent Document 3, the response characteristics of Pt and Pd transition metal chalcogenide thin films to light with a wavelength of 940 nm have been confirmed, and therefore they are expected to be used as semiconductor materials compatible with the near-infrared region (NIR). However, their response in the short-wave infrared region (SWIR), which is a longer wavelength region, has not been confirmed. As mentioned above, in recent years, it has also been considered important for LiDAR and its light-receiving layer to exhibit effective photoresponse in the NIR.

[0012] The present invention has been made in light of the above-mentioned background and provides a semiconductor material useful as a light-receiving layer in optical sensors such as LiDAR, which employs a thin film made of a transition metal chalcogenide. In particular, the present invention clarifies a semiconductor material that can demonstrate sufficient applicability in the shortwave infrared region (SWIR) as well as the near-infrared region (NIR). A suitable method for manufacturing such a semiconductor material is also disclosed. In this invention, the near-infrared region (NIR) refers to a wavelength range of 700 nm or more and less than 1100 nm, and the shortwave infrared region (SWIR) refers to a wavelength range of 1100 nm or more and less than 3000 nm. [Means for solving the problem]

[0013] When investigating the photoresponsive properties of semiconductor thin films, it is necessary to optimize the band gap of the transition metal chalcogenide that constitutes them. The photon energy equation (E=hc / λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength) can be used to calculate the band gap required for the wavelength range in which photoresponsiveness is required. Based on this index, a semiconductor film with a band gap of approximately 1.77 eV or less is required to respond to the NIR region, and a band gap of approximately 0.41 eV to approximately 1.13 eV is required to respond to the SWIR region. Based on the above band gap index, the inventors conducted research to find a chalcogenide exhibiting a suitable band gap, and focused on chalcogenides of Ru (ruthenium), a transition metal and a noble metal.

[0014] However, even among ruthenium chalcogenides, there is no material that optimally matches the above-mentioned bandgap index. Although this will be described later, the inventors of the present invention have conducted preliminary studies on RuSe2, which is a ruthenium selenide, as a ruthenium chalcogenide. As a result, it has been found that RuSe2 has a particularly low bandgap among transition metal chalcogenides and can be expected to have a light responsiveness in the SWIR region, but it is difficult to cover the NIR region.

[0015] Therefore, as a result of further studies, the inventors of the present invention have found that by doping S into RuSe2, which has a low bandgap, and partially substituting it to form a ternary ruthenium chalcogenide, it is possible to exhibit responsiveness to both NIR and SWIR, and thus arrived at the present invention.

[0016] That is, the present invention relates to a semiconductor material including a substrate and a semiconductor thin film formed on the substrate. In the semiconductor thin film, the semiconductor thin film is composed of a ruthenium chalcogenide represented by the following formula composed of Ru, Se which is a chalcogen element, and S. The semiconductor material is characterized in that the film thickness of the semiconductor thin film is 10 nm or more and 100 nm or less.

[0017]

Chemical formula

[0018] Hereinafter, the details of the semiconductor material including the transition metal chalcogenide thin film according to the present invention will be described. As described above, the semiconductor material according to the present invention has a basic structure of a substrate and a semiconductor film on the substrate, and thus each of these structures will be described. In the present specification, the ruthenium transition metal chalcogenide (RuSe x S y ) applied in the present application may be referred to as "ruthenium chalcogenide".

[0019] (A) Structure of the semiconductor material according to the present invention (A-1) Base material The substrate is a member for supporting a thin film made of Ru chalcogenide. The substrate may be made of any material that can support a thin film made of a transition metal chalcogenide. Examples of the material include glass, quartz, silicon, ceramics, and metal. The shape and dimensions of the substrate are not particularly limited.

[0020] (A-2) Semiconductor film (Ru chalcogenide thin film) In the present invention, the transition metal chalcogenide thin film constituting the semiconductor film is a chalcogenide of Ru, Se, and S, and is RuSe x S y The reason for using Ru chalcogenides in this invention is that Ru and other noble metal chalcogenides have a lower band gap than other transition metal chalcogenides (such as MoS2). Furthermore, thin films of transition metal chalcogenides can be produced by chemical vapor deposition. In the Ru chemical vapor deposition method, a relatively large number of Ru complexes are known to be usable as raw materials (precursors) and are easily available, so Ru is considered to be advantageous in terms of production costs as well.

[0021] A specific embodiment of the semiconductor film of the present invention is a transition metal chalcogenide in which RuSe2, a Ru selenide, is doped with S and partially substituted. As mentioned above, RuSe2 has a low band gap, and while it can be expected to have responsiveness in the SWIR region, it has poor responsiveness in the NIR region. In the present invention, by doping RuSe2 with S, the band gap of the semiconductor film is adjusted, ensuring responsiveness in the wavelength range from the NIR region to the SWIR region. Specifically, it has responsiveness to light in the wavelength range of 900 nm to 2500 nm.

[0022] The composition of the Ru chalcogenide thin film varies depending on the values of x and y in the above formula. x is the ratio of the number of Se atoms when the number of Ru atoms is set to 1. y is the ratio of the number of S atoms when the number of Ru atoms is set to 1. x and y are real numbers such that 0 < x < 2.0 and 0 < y < 1.9. Also, for the sum of x and y, 1.9 < x + y < 2.0. And as the doping ratio of S increases, that is, as the value of y increases, the band gap of the semiconductor film shifts to the high-energy side.

[0023] In the semiconductor film according to the present invention, in order to improve the responsiveness of the semiconductor film in the NIR region and the SWIR region, the value of x is preferably 0.1 or more and 1.5 or less, and the value of y is preferably 0.6 or more and 1.5 or less. Further, it is more preferable that the value of x is 0.6 or more and 1.1 or less, and the value of y is 0.9 or more and 1.3 or less. In the present invention, the Ru chalcogenide thin film (RuSe x S y ) may be a stoichiometric composition based on the valences of the respective constituent elements, but it does not necessarily have to be in the stoichiometric composition.

[0024] Details will be described later, but the Ru chalcogenide thin film (RuSe x S y ) of the present invention is manufactured by heating a RuSe2 film formed by chemical vapor deposition while contacting it with an S-containing gas. The composition (x, y) of the Ru chalcogenide thin film can be controlled by adjusting the heating temperature. Also, for the analysis and identification of the composition (x, y) of the chalcogenide of Ru constituting the semiconductor film, various analysis methods can be applied. As the analysis methods, energy dispersive X-ray analysis (EDS, EDX), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), etc. can be applied.

[0025] And the semiconductor material according to the present invention is a Ru chalcogenide (RuSe x S y) thin film formed on a substrate. The thickness of this Ru chalcogenide thin film should be between 10 nm and 100 nm. Thin films less than 10 nm do not provide sufficient sensitivity when receiving NIR or SWIR light. On the other hand, thick films greater than 100 nm may result in reduced photoelectric conversion efficiency when electrodes are stacked on top and bottom of the substrate, as the electrons and holes generated by the received light are not efficiently separated and recombine. Furthermore, excessively thick semiconductor films can cause cracks within the layer, leading to disconnections. Furthermore, chemical vapor deposition, which aims for precise film formation, is not practical for forming films thicker than 100 nm.

[0026] The semiconductor material according to the present invention is a semiconductor material comprising the above-described substrate and a Ru chalcogenide thin film (RuSe x S y ) as essential components. The semiconductor material according to the present invention may also have other components. For example, it may have an electrode layer on the upper and / or lower surface of the semiconductor film, or an auxiliary layer. Furthermore, the semiconductor film, which is a Ru chalcogenide thin film, may be modified with the metal nanoparticles described in Patent Document 3. The metal nanoparticles have the effect of preferentially modifying defective portions on the semiconductor film surface and suppressing carrier traps caused by the defects. Therefore, modification with metal nanoparticles does not change the response wavelength of the semiconductor film, so the response in the NIR and SWIR regions is maintained.

[0027] (B) The method for producing a semiconductor material according to the present invention Next, a method for manufacturing a semiconductor material according to the present invention will be described. As described above, the Ru chalcogenide thin film, which is the semiconductor film according to the present invention, is composed of Ru and the chalcogen elements Se and S. This Ru chalcogenide thin film is formed by doping a thin film of Ru selenide with S (sulfur). That is, the method for manufacturing a semiconductor material according to the present invention is a method including a step of forming a thin film made of Ru selenide on a substrate (film formation step) and a step of doping the thin film with S (doping step). Each step of the method for manufacturing a semiconductor material according to the present invention will be described below.

[0028] The Ru chalcogenide thin film of the present invention is produced by doping S into a Ru selenide thin film, which is a ternary compound Ru chalcogenide thin film (RuSe x S y This is to efficiently form the film while taking into consideration the composition adjustment of the element. Se has a larger atomic radius than S and a weaker bond with Ru. Therefore, Ru sulfide (RuS) is doped with Se to form a Ru chalcogenide thin film (RuSe x S y Therefore, in the present invention, a Ru-selenium compound, which has a weaker bonding strength than Ru sulfide, is used as a precursor, and S, which has a stronger bonding strength with Ru than Se, is added to the precursor.

[0029] (B-1) Ru selenide film formation process Chemical vapor deposition methods such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) are used to form Ru selenide films on substrates. Chemical vapor deposition allows for the formation of Ru selenide films with a uniform composition, which in turn allows for the formation of uniform Ru chalcogenide thin films. Furthermore, chemical vapor deposition allows for the efficient formation of thin films with the required thickness.

[0030] In the basic process of chemical vapor deposition, a metal compound serving as a precursor for the thin film is vaporized, the resulting precursor gas is supplied to a substrate, and a reaction (decomposition reaction or synthesis reaction) occurs in the gas phase, depositing the target substance on the substrate to form a film. Chemical vapor deposition (CVD) is a process in which the reaction proceeds for a predetermined time to form a thin film of a desired thickness. Atomic layer deposition (ALD) is a process in which a cycle consists of supplying a precursor gas to the substrate surface to a thickness of one to several atomic layers and purging the excess precursor gas, and this cycle is repeated to form a thin film of a desired thickness. Chemical vapor deposition is highly efficient because it can form a film of the required thickness in one cycle, while atomic layer deposition allows film formation at the atomic layer level, enabling highly accurate film thickness control. In the present invention, both CVD and ALD processes can be used as chemical vapor deposition.

[0031] In the present invention, a Ru selenide film is formed by chemical vapor deposition. In the deposition of the selenide film, a Ru metal compound (Ru complex) is used as a precursor, and the precursor is vaporized to generate a Ru source gas. The precursor is then reacted with the substrate surface in an Se gas atmosphere, whereby Ru selenide is precipitated on the substrate surface.

[0032] Examples of Ru complex precursors include organoruthenium compounds such as dicarbonyl-bis(5-methyl-2,4-hexanedionato)ruthenium, hexacarbonyl[methyl-(1-methylpropyl)-butene-aminato]diruthenium, and dodecacarbonyltriruthenium (DCR). These organoruthenium compounds are heated to vaporize or sublimate them into source gases. The source gases are introduced onto the substrate in the reactor of a film formation device using an appropriate carrier gas such as Ar. The source gas supply rate is preferably 5 sccm to 100 sccm, more preferably 5 sccm to 50 sccm. An excessively high source gas supply rate excessively promotes the growth of the Ru-selenium compound.

[0033] To create a selenium atmosphere on the substrate surface, a selenium-containing gas is introduced onto the substrate surface. As a raw material for the selenium-containing gas, a selenium compound (e.g., HSe (hydrogen selenide)) or solid selenium (Se) may be used. Solid selenium sublimes when heated to form a selenium-containing gas. The form of the solid selenium is not limited, and powder, bulk, etc. may be used.

[0034] When a selenium-containing gas is generated from solid selenium and introduced into the substrate, the selenium-containing gas may be generated outside the reactor and supplied to the reactor. In addition, in the present invention, a two-zone heating reactor can be used as the reactor. A two-zone heating reactor is a reaction vessel having heating means at two locations: the substrate setting position and a predetermined position upstream of the substrate. Solid selenium is set upstream of the substrate in the reactor and heated and gasified separately from the substrate. At this time, the selenium-containing gas is transported to the substrate surface together with the Ru source gas introduced into the reactor. The heating temperature when converting solid selenium into a selenium-containing gas is preferably 200°C or higher and 240°C or lower.

[0035] The Ru source gas introduced onto the substrate surface in the selenium atmosphere as described above reacts to form a Ru selenide film. It is preferable to heat the substrate to promote the reaction. The reaction temperature for forming the Ru selenide film is preferably 250°C or higher and 350°C or lower. The film formation time is preferably 5 minutes or higher and 120 minutes or lower.

[0036] (B-2) S doping process By doping S into a Ru selenide film formed by chemical vapor deposition, the Ru chalcogenide thin film (RuSe x S y The doping of S is achieved by heating the Ru selenide film while contacting it with a sulfur-containing gas.

[0037] As the sulfur-containing gas for S doping, solid sulfur (S) can be used in addition to sulfur compounds (H2S (hydrogen sulfide)). When solid sulfur is used as the sulfur-containing gas, it is sublimated and gasified by heating at 120°C or higher. When supplying the sulfur-containing gas to the Ru selenide film for S doping, the supply rate is preferably 25 sccm to 100 sccm. However, as will be described later, the composition change (change in x) of the Ru chalcogenide thin film due to S doping tends to depend on the heating temperature, so the supply rate of the sulfur-containing gas is not particularly limited.

[0038] The heating temperature for doping S into the Ru selenide film is set to 300° C. or more and 600° C. or less. x S y The values ​​of x and y, which indicate the composition of RuS2, vary depending on the heating temperature in this process. If the heating temperature is less than 300°C, S doping does not progress easily, and the Ru selenide film remains in this state. As the heating temperature increases, the amount of S doped increases, and the value of x also increases. If the heating temperature exceeds 600°C, S becomes excessively doped, and the film becomes almost entirely a Ru sulfide film (RuS2). Preferably, the heating temperature is set to 400°C or higher and 550°C or lower, so that the values ​​of x and y can be kept within the above-mentioned preferred range. The heating time for S doping is preferably set to 0.5 hours or higher and 1 hour or lower.

[0039] By going through the above S doping process, a Ru chalcogenide thin film, which is the semiconductor film of the present invention, is formed. [Effects of the Invention]

[0040] As described above, the present invention is x S y The semiconductor material has a thin film of Ru chalcogenide represented by the following formula: The semiconductor film of the present invention is formed by doping a Ru selenide film with S, and the band gap changes depending on the doping amount (y) of S. This allows the semiconductor film to exhibit photoresponsiveness over a wide wavelength range from the near-infrared region (NIR) to the short-wave infrared region (SWIR). [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a diagram illustrating an outline of a CVD apparatus used in forming a Ru selenide film (RuSe2) in this embodiment. [Figure 2] 1A and 1B are diagrams showing the results of Raman analysis of a Ru selenide film (RuSe2) and a Ru chalcogenide thin film (RuSexSy) produced in this embodiment. [Figure 3]1A and 1B are diagrams showing the results of XRD analysis of a Ru selenide film (RuSe2) and a Ru chalcogenide thin film (RuSexSy) produced in this embodiment. [Figure 4a] EDS mapping of the Ru selenide film (RuSe2) produced in this embodiment. [Figure 4b] 1 shows EDS mapping of the Ru chalcogenide thin film (RuSexSy) produced in this embodiment. [Figure 5a] 1 is an XPS profile of a Ru selenide film (RuSe2) produced in this embodiment. [Figure 5b] 1 shows XPS profiles of the Ru chalcogenide thin film (RuSexSy: 300° C., 400° C., 500° C., 600° C.) produced in this embodiment. [Figure 6] 10A and 10B are diagrams showing the measurement results of the absorption spectra of a Ru selenide film (RuSe2) and a Ru chalcogenide thin film (RuSexSy) manufactured in this embodiment. [Figure 7] FIG. 10 is a graph showing the evaluation results of the SWIR light response of the Ru chalcogenide thin film (RuSexSy: 500° C.) manufactured in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0042] Hereinafter, an embodiment of the present invention will be described. In this embodiment, a Ru selenide film (RuSe) is formed on a substrate by a CVD method, and then a Ru chalcogenide thin film (RuSe) is formed by contacting and heating an S-containing gas. x S y ) to fabricate semiconductor materials. At this time, the heating temperature was changed to form Ru chalcogenide thin films with different x values. The composition (x) of each Ru chalcogenide thin film was confirmed, and their band gap values ​​were measured and their photoresponse was evaluated.

[0043] [Ru selenide film (RuSe2) deposition process] An SiO2 / Si substrate (dimensions: 20 mm x 20 mm x 1 mm, SiO2 film thickness: 300 nm) was prepared as the substrate, and a RuSe2 thin film was formed on this substrate by the CVD method (thermal CVD).

[0044] In this embodiment, a CVD apparatus equipped with a two-zone heating reactor was used. Figure 1 shows a schematic diagram of the reactor configuration. In the film formation process, the above-mentioned substrate was set in the reactor, and 5 g of selenium powder was placed upstream of the substrate. The temperatures of the substrate and selenium powder were independently controllable. Before film formation, the reactor was purged with argon gas (200 sccm).

[0045] As a precursor of Ru, dicarbonyl-bis(5-methyl-2,4-hexanedionato)ruthenium of the following formula was used, and this Ru complex was heated and vaporized, and introduced into the reactor together with a carrier gas.

[0046] [ka]

[0047] The selenium powder in the reactor was then heated and sublimated, decomposing the Ru complex introduced onto the substrate and causing the Ru and selenium to react, depositing RuSe2 and forming a thin film. The film formation conditions were as follows: The thickness of the RuSe2 thin film formed on the substrate in this film formation process was 15 nm. ·Raw material heating temperature: 100℃ Carrier gas: Argon / 10sccm Substrate temperature / Selenium powder heating temperature: 300℃ / 220℃ Deposition time: 10 minutes

[0048] [S doping process] The RuSe2 thin film formed above was doped with S to form a Ru chalcogenide thin film (RuSe x S y After the RuSe2 thin film was formed, the reactor was purged, and then H2S gas was introduced into the reactor and the substrate was heated. The reaction conditions for this S doping process were as follows: ·H2S flow rate: 50sccm ·Heating temperature: 300℃, 400℃, 500℃, 600℃ Cooking time: 60 minutes

[0049] [Ru chalcogenide thin film (RuSe x S y ) Various analyses] The RuSe2 thin film and the S-doped Ru chalcogenide thin film (RuSe) deposited at various temperatures were x S y ) were subjected to Raman spectroscopy and XRD analysis. Raman spectroscopy was performed using a Raman spectrometer (Horiba Ltd., LabRam ARAMIS) with a laser wavelength of 532 nm. XRD was performed using a high-resolution XRD device (Rigaku Corporation, SmartLab) in the 2θ range of 20° to 70°.

[0050] RuSe2 thin film and Ru chalcogenide thin film (RuSe x S y As a result of the analysis of the RuSe2 thin film, the Raman spectroscopic analysis results (Raman shift) are shown in Figure 2, and the XRD diffraction pattern is shown in Figure 3. Both analysis results show that the Raman shift peak and diffraction peak shift as the heating temperature during S doping increases. By heating at 300°C or higher, the RuSe2 thin film becomes a Ru chalcogenide thin film (RuSe x S y ) state. It is estimated that most of the film is converted to a RuS2 film by heating at 600°C. Although not shown, there was no change in the peak position for the RuSe2 thin film heated at 600°C without a sulfur atmosphere. This indicates that the heating in the S doping process itself does not affect the RuSe2 composition, and that the peak shift described above is due to a change in composition caused by S doping.

[0051] [Composition analysis of Ru chalcogenide thin films] Next, the RuSe2 thin film and the Ru chalcogenide thin film (RuSe x S yThe composition of the sample was analyzed by EDS and XPS. EDS was measured using a SEM (JSM-761FPlus manufactured by JEOL Ltd.) at a magnification of 50,000 times. XPS was analyzed using an XPS spectrometer (Thermo Scientific manufactured by Thermo Fisher Scientific K.K.).

[0052] As part of the composition analysis results, EDS mapping results (RuSe2 thin film and RuSe heated at 500°C) are shown in Figures 4a and 4b. x S y ) are shown in Fig. 5a and 5b. The results of XPS analysis (RuSe2 thin film and RuSe2 heated at 300°C, 400°C, 500°C, and 600°C) are shown in Fig. 5a and 5b. x S y ) are shown. The XPS results in Figures 5a and 5b show the measured spectrum and the results of waveform separation processing of the measured spectrum.

[0053] Based on the results of XPS analysis, the RuSe2 thin film before doping and the S-doped RuSe at 300°C to 600°C were x S y The values ​​of x and y, which indicate the composition of the thin film, were determined.

[0054] [Band gap measurement of Ru chalcogenide thin films] The RuSe2 thin film and Ru chalcogenide thin film (RuSe x S y The band gap was measured by measuring the absorption spectrum of each thin film. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (V-700 manufactured by JASCO Corporation) in the wavelength range of 400 nm to 1100 nm. The measurement results, which are the absorption spectrum curves (wavelength (eV) / transmittance ((ahv) 1 / 2 )) are shown in Figure 6. The rising part of the absorption edge in the absorption spectrum curve for each thin film was fitted with a straight line, and the intersection with the baseline was taken as the band gap. The band gap measurement results are shown in Table 1.

[0055] [Table 1]

[0056] From Table 1, it was confirmed that the value of the atomic ratio y, which indicates the doping ratio of S, increases with an increase in the heating temperature in the S doping process. It was also confirmed that the band gap of the thin film shifts to the higher energy side with an increase in the S atomic ratio yy.

[0057] [Evaluation of SWIR response of Ru chalcogenide thin films] The S-doped Ru chalcogenide thin film (RuSe x S y The response characteristics to 1550 nm SWIR were evaluated at (x = 0.76, y = 1.25). For the SWIR response evaluation, a measurement sample was prepared by patterning a Ti film (5 nm thick) and an Au film (40 nm thick) in a comb shape on the surface of the semiconductor film using thermal evaporation. A bias voltage of 0.5 V was applied using a multimeter connected to the electrode, and a 1550 nm laser light source (manufactured by AeroDIODE) was used to irradiate the semiconductor film with laser light for 40 seconds on and 40 seconds off on the substrate, and the photocurrent was measured.

[0058] The photocurrent measurement results for SWIR response are shown in Figure 7. From Figure 7, it can be seen that photocurrent was observed only when laser irradiation (1550 nm) was ON. It was confirmed that the semiconductor material of this embodiment, which uses a Ru chalcogenide thin film as the semiconductor film, can exhibit photoresponsiveness in the SWIR region. [Industrial Applicability]

[0059] As described above, the Ru chalcogenide thin film (RuSe x S y) as a semiconductor film has a band gap that corresponds to the doping amount (y) of S. As a result, the present invention exhibits photoresponsiveness over a wide wavelength range from the near-infrared region (NIR) to the shortwave infrared region (SWIR). The semiconductor material according to the present invention is useful as a constituent material for the light-receiving layer of various optical semiconductor devices, and is expected to contribute to improving the performance and miniaturization of such devices as the light-receiving element of optical sensors for LiDAR and image sensors.

Claims

1. A semiconductor material including a substrate and a semiconductor thin film formed on the substrate, The semiconductor thin film is made of Ru chalcogenide represented by the following formula, which is made of Ru and chalcogen elements Se and S: A semiconductor material characterized in that the semiconductor thin film has a thickness of 10 nm or more and 100 nm or less. 【Chemical 1】 (In the above formula, x and y are the ratios of the number of Se and S atoms to the number of Ru atoms, respectively, and are real numbers satisfying 0<x<2.0 and 0<y<1.9, and 1.9<x+y<2.0.)

2. 2. The semiconductor material according to claim 1, which is responsive to light in the wavelength range of 900 nm or more and 2500 nm or less.

3. 3. A method for producing a semiconductor material according to claim 1 or claim 2, comprising: a film-forming step of forming a thin film made of Ru selenide on a substrate by chemical vapor deposition; and a doping step of contacting the thin film with a sulfur-containing gas and heating the thin film to dope the thin film with S to form a Ru-chalcogenide thin film.

4. 4. The method for producing a semiconductor material according to claim 3, wherein the heating temperature in the doping step is 300° C. or higher and 600° C. or lower.

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