KR20190085682A - Photodetector and manufacturing method thereof - Google Patents

Abstract

Provided are a photodetector with improved performance and manufacturing method thereof. The photodetector comprises: a substrate; a molybdenum sulfide film formed on the substrate and growth in a vertical direction; an upper contact formed on the molybdenum sulfide film; and a lower contact formed below the substrate.

Description

Photodetector and manufacturing method < RTI ID = 0.0 >

The present invention relates to a photodetector and a method of manufacturing the same.

Graphene lacks some important features as a much discussed research in the modern era. One of them is that there is no bandgap, and because of this drawback, graphene is difficult to become a potential material for optoelectronic devices. However, research has continued to find semiconducting materials such as graphene because of its outstanding properties such as transparency of 97%, ultra thin film (1 atom thickness), high conductivity and Young's modulus of 1.1 TPa.

As a result, molybdenum disulfide (MoS ₂ ), an excellent member of the transition metal dichalcogenides (TMDs) family, is a natural candidate and a suitable candidate to replace graphene in all aspects, including structure . The bulk MoS ₂ material can be sliced into an equally thin 2D layer. Each of these 2D layers consists of a single sheet of molybdenum sandwiched between thin films of chalcogen.

Patent Registration No. 10-1241467

A problem to be solved by the present invention is to provide a photodetector with improved operation performance.

A further object of the present invention is to provide a method of manufacturing a photodetector with improved operational performance.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a photodetector comprising a substrate, a molybdenum sulfide film formed on the substrate and grown in a vertical direction, an upper contact formed on the molybdenum sulfide film, The lower contact being formed.

According to another aspect of the present invention, there is provided a method of manufacturing a photodetector, including: providing a substrate including first and second surfaces opposite to each other; forming a lower contact on the second surface; Depositing a molybdenum sulfide film at a first temperature on the first side, and forming an upper contact on the molybdenum sulfide film.

The details of other embodiments are included in the detailed description and drawings.

According to one embodiment of the present invention, at least the following effects are obtained.

That is, the photodetector according to some embodiments of the present invention may have a high response characteristic for a wide band of light.

The method of manufacturing the photodetector according to some embodiments of the present invention can adjust the degree of absorption according to the temperature variation.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the specification.

1 is a perspective view illustrating a photodetector according to some embodiments of the present invention.
Figure 2 is an image of a photodetector manufactured in accordance with some embodiments of the present invention.
3 is a FESEM (Field Emission Scanning Electron Microscope) image showing a cross section of the photodetector of FIG.
FIGS. 4 to 8 are intermediate-level diagrams illustrating a method of manufacturing a photodetector according to some embodiments of the present invention.
9 is an image showing an actually produced image of Embodiments 1 to 3 of the present invention.
10 is an image showing a MoS ₂ film formed on a 3 inch silicon wafer of some embodiments of the present invention.
11 is an X-ray diffraction (XRD) profile of the MoS ₂ films of Examples 1 to 3 of the present invention.
12 is an FESEM image showing the surface morphology of the MoS ₂ film of Example 1 of the present invention.
13 is an FESEM image showing the surface morphology of the MoS ₂ film of Example 2 of the present invention.
14 is an FESEM image showing the surface morphology of the MoS ₂ film of Example 3 of the present invention.
FIG. 15 is a graph showing the absorption of MoS ₂ films according to Examples 1 to 3 according to wavelengths of the present invention. FIG.
16 is a diagram showing the photoreaction at a wavelength of 455 nm of the photodetector of Example 3 of the present invention.
17 is a diagram showing the photoreaction at a wavelength of 515 nm of the photodetector of Example 3 of the present invention.
18 is a diagram showing the photoreaction at a wavelength of 620 nm of the photodetector of Example 3 of the present invention.
19 is a table summarizing a rise time and a fall time with respect to a wavelength of a photodetector according to the third embodiment of the present invention.
20 is a table comparing the characteristics of the photodetector of the third embodiment of the present invention with the conventional photodetector.
FIG. 21 is a graph showing the photocurrent according to the intensity of light with respect to incident light of blue color of the photodetector according to the third embodiment of the present invention. FIG.
FIG. 22 is a graph showing photocurrent according to the intensity of light with respect to incident light of green color of the photodetector of Example 3 of the present invention. FIG.
23 is a graph showing photocurrent according to intensity of light with respect to incident light of red color of the photodetector of Example 3 of the present invention.
FIG. 24 is a diagram showing the response and detectability at a wavelength of 455 nm of the photodetector of Example 3 of the present invention. FIG.
Fig. 25 is a chart showing the response and detectability of the photodetector according to the third embodiment of the present invention at a wavelength of 515 nm. Fig.
26 is a chart showing the response and detection ability of the photodetector according to the third embodiment of the present invention at a wavelength of 620 nm.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Although the first, second, etc. are used to describe various elements, components and / or sections, it is needless to say that these elements, components and / or sections are not limited by these terms. These terms are only used to distinguish one element, element or section from another element, element or section. Therefore, it goes without saying that the first element, the first element or the first section mentioned below may be the second element, the second element or the second section within the technical spirit of the present invention.

It is to be understood that when an element or layer is referred to as being "on" or " on "of another element or layer, All included. On the other hand, a device being referred to as "directly on" or "directly above " indicates that no other device or layer is interposed in between.

The terms spatially relative, "below", "beneath", "lower", "above", "upper" May be used to readily describe a device or a relationship of components to other devices or components. Spatially relative terms should be understood to include, in addition to the orientation shown in the drawings, terms that include different orientations of the device during use or operation. For example, when inverting an element shown in the figure, an element described as " below or beneath "of another element may be placed" above "another element. Thus, the exemplary term "below" can include both downward and upward directions. The elements can also be oriented in different directions, in which case spatially relative terms can be interpreted according to orientation.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that the terms "comprises" and / or "comprising" used in the specification are intended to be inclusive in a manner similar to the components, steps, operations, and / Or additions.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

Hereinafter, a photodetector according to some embodiments of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view illustrating a photodetector according to some embodiments of the present invention, and FIG. 2 is an image of a photodetector actually manufactured according to some embodiments of the present invention. 3 is a FESEM (Field Emission Scanning Electron Microscope) image showing a cross section of the photodetector of FIG.

1 to 3, a photodetector according to some embodiments of the present invention includes a substrate 100, a bottom contact 200, a top contact 400, and a molybdenum sulfide film 300.

The substrate 100 may be a silicon substrate. The substrate 100 may be a p-type silicon substrate. The substrate 100 may include a top surface and a bottom surface in a first direction X and a side surface in the second direction Y and in a third direction Z. [ In this case, the first direction (X), the second direction (Y), and the third direction (Z) intersect with each other and may be perpendicular to each other. Accordingly, the first direction X, the second direction Y, and the third direction Z may be directions orthogonal to each other.

The substrate 100 may include a first side and a second side opposite to each other. The first surface and the second surface may be opposite to each other in the third direction (Z). Thus, in Figure 1, the first side of the substrate 100 is the upper surface, and the second side of the substrate 100 is the lower surface.

The upper surface of the substrate 100 may be a (100) plane of silicon. As the upper surface of the substrate 100 is the (100) plane of silicon, the molybdenum sulfide film 300 can grow laterally in the vertical direction.

The thickness of the substrate 100 may be sufficiently thick to support the top and bottom structures. For example, the thickness of the substrate 100 may be 100 to 1000 占 퐉. However, the present embodiment is not limited thereto.

The lower contact 200 may be formed on the second surface, that is, the lower surface of the substrate 100. The lower contact 200 may be a metal contact. The lower contact 200 may comprise, for example, Al. However, the present embodiment is not limited thereto. The lower contact 200 may cover the lower surface of the substrate 100. Specifically, the lower surface of the substrate 100 may be covered by the lower contact 200 since the lower surface of the substrate 100 is not in the direction of receiving the incident light.

The lower contact 200 may be formed to a thickness of, for example, 50 to 500 nm. However, the present embodiment is not limited thereto. The lower contact 200 may be formed to a thickness sufficient to transfer the current generated by the substrate 100 and the molybdenum sulfide film 300 to the outside. If the lower contact 200 is too thick, the resistance can be increased.

The molybdenum sulfide film 300 may be formed on the first surface, that is, the upper surface of the substrate 100. The molybdenum sulfide film 300 may include MoS ₂ . The molybdenum sulfide film 300 may be a MoS ₂ film grown in the vertical direction. Specifically, MoS ₂ is a two-dimensional (2D) material, and a two-dimensional material has a property of preferentially growing only in a plane direction. That is, since the growth direction is a two-dimensional plane, growth does not occur in the direction perpendicular to the growth direction.

The molybdenum sulfide film 300 may be a vertically grown film that grows in the third direction Z. [ The molybdenum sulfide film 300 grows first in the third direction Z and grows slowly or slowly in the first direction X and the second direction Y, i.e., in the horizontal direction. That is, the growth rate of the molybdenum sulfide film 300 in the horizontal direction may be smaller than the growth rate in the vertical direction.

The molybdenum sulfide film 300 may have characteristics more suitable for a photodetector by being grown vertically. The molybdenum sulfide film 300 may have a leaf or leaves shape in the plane of the first direction X or the side of the second direction Y. [

The molybdenum sulfide film 300 may be formed to cover the upper surface of the substrate 100 on the substrate 100. The molybdenum sulfide film 300 may be formed to a thickness of 10 to 200 nm, for example. However, the present embodiment is not limited thereto.

The molybdenum sulfide film 300 may form a rectifying junction with the substrate 100.

The upper contact 400 may be formed to cover the upper surface of the molybdenum sulfide film 300. However, since the upper surface of the molybdenum sulfide film 300 is located in a direction in which incident light is incident, the upper surface of the molybdenum sulfide film 300 may have a grid shape so as not to cover the upper surface of the molybdenum sulfide film 300. That is, a part of the upper surface of the molybdenum sulfide film 300 may be exposed to the outside by the upper contact 400.

The upper contact 400 can maximize the area where the incident light on the upper surface of the molybdenum sulfide film 300 enters. The upper contact 400 may include a body 410 and a branch 420.

The body 410 may extend in the second direction Y and may be located in the center of the upper contact 400 in the first direction X. [ The body 410 may have a first thickness. For example, the first thickness may be 50 to 500 nm. However, the present embodiment is not limited thereto.

The body 410 may be a portion connected to the outside. Therefore, it is formed thicker than the branch 420 to be described later, so that connection with the outside can be facilitated.

The branch 420 may extend in the first direction X at the body 410. The branch 420 may extend to both sides in the first direction X about the body 410. The branches 420 extending to both sides may extend the same length from the body 410. Accordingly, the shape of the upper contact 400 may be symmetrical in the first direction X with respect to the body 410. This is to ensure that the current of the photodetector according to some embodiments of the present invention is transmitted uniformly.

The branch 420 may have a second thickness that is less than the first thickness of the body 410. The branch 420 may contact the body 410 and the molybdenum sulfide film 300 and may not be directly connected to the outside.

The top contact 400 of the photodetector according to some embodiments of the present invention may include a metal such as Al. In addition, the upper contact 400 of the photodetector according to some embodiments of the present invention may include at least one of a metal such as Al, a transparent conductive layer, and a metal nanowire. At this time, the transparent conductive layer may include a transparent conductor such as ITO or FTO.

FIG. 2 is an image of a photodetector actually manufactured, and FIG. 3 is an FESEM image showing a cross section of the photodetector of FIG.

Hereinafter, a method of manufacturing a photodetector according to some embodiments of the present invention will be described with reference to FIGS. 1 and 4 to 8. FIG. The description overlapping with the above embodiment is simplified or omitted.

FIGS. 4 to 8 are intermediate-level diagrams illustrating a method of manufacturing a photodetector according to some embodiments of the present invention.

First, referring to FIG. 4, a substrate 100 is provided.

The substrate 100 may include a first side 101 and a second side 102 that are opposite to each other in a third direction Z. [ In Figure 4, the first side 101 is shown as the top side and the second side 102 is shown as the bottom. In the photodetector according to some embodiments of the present invention, the first side 101 and the second side 102 may be the lower surface and the upper surface, respectively. For convenience, the first surface 101 and the second surface 102 are referred to as upper and lower surfaces, respectively.

The substrate 100 may be a p-type silicon substrate. The upper surface of the substrate 100 may be a (100) plane of silicon. The substrate 100 can be cleaned by ultrasonic treatment using acetone and distilled water.

Referring now to FIG. 5, a bottom contact 200 is formed on a second side 102 of the substrate 100.

The lower contact 200 may include Al. The lower contact 200 may be deposited by DC sputtering. The lower contact can completely cover the lower surface of the substrate 100. [

Next, referring to FIG. 6, a molybdenum sulfide film 300 is formed on the first surface 101 of the substrate 100.

The molybdenum sulfide film 300 may include MoS ₂ . The molybdenum sulfide film 300 may be a MoS ₂ film grown in the vertical direction. The molybdenum sulfide film 300 may be deposited using RF sputtering. As the molybdenum sulfide film 300 is formed, the substrate 100 and the molybdenum sulfide film 300 can form a rectification junction.

The molybdenum sulfide film 300 is first grown in the third direction Z and the molybdenum sulfide film 300 is not grown or grown slowly in the first direction X and the second direction Y . That is, the growth rate of the molybdenum sulfide film 300 in the third direction Z may be greater than the growth rate in the first direction X and the second direction Y.

The molybdenum sulfide film 300 may be deposited at a first temperature. At this time, the first temperature may be from room temperature to 600 ° C. As the first temperature is changed, the structure and surface state of the molybdenum sulfide film 300 may be changed. Accordingly, various characteristics of the molybdenum sulfide film 300 can be changed. The substrate 100 may be rotated at a constant speed while the molybdenum sulfide film 300 is being deposited. This can make the deposition of the molybdenum sulfide film 300 uniform.

Next, referring to FIG. 7, an upper contact 400 is formed on the molybdenum sulfide film 300. Top contact 400 may have a grid shape. That is, a portion of the molybdenum sulfide film 300 may be exposed to the outside by the upper contact 400. The upper contact 400 may be deposited by DC sputtering.

Referring now to FIG. 8, a phototetector according to some embodiments of the present invention may be subjected to a rapid thermal process (RTP) 50.

The rapid thermal annealing 50 can further strengthen the adhesion between the upper contact 400 and the molybdenum sulfide film 300. Similarly, the rapid thermal annealing process 50 can further strengthen the adhesion between the lower contact 200 and the substrate 100.

The rapid thermal processing (50) may be performed at a second temperature. The second temperature may be 100-1000 < 0 > C. The rapid thermal annealing (50) may be performed for 5 to 60 minutes.

Next, referring to FIG. 1, a photodetector can be completed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of manufacturing a photodetector and a photodetector according to some embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1-RT

The p-type silicon substrate was cleaned, and an Al lower contact was formed on the lower surface. A 4-inch Al target was DC sputtered for 10 minutes at 300 W DC power to form an Al bottom contact. Subsequently, a 4-inch MoS ₂ target was deposited on the upper surface of the substrate for 30 minutes using RF sputtering of 25 W to form a vertical MoS ₂ film, that is, a molybdenum sulfide film. At this time, the MoS ₂ film was deposited at room temperature (RT). During the deposition of the MoS ₂ film, the substrate rotated at a constant rate of 5 rpm. Then, a grid-shaped upper Al contact was formed on the MoS ₂ film by DC sputtering, and rapid thermal annealing was performed at 500 캜 for 10 minutes.

Example 2 200 占 폚

Except that the deposition temperature of the MoS ₂ film was changed to 200 캜.

Example 3-400 [

Except that the deposition temperature of the MoS ₂ film was changed to 200 캜.

9 is an image showing an actually produced image of Embodiments 1 to 3 of the present invention. Fig. 9 shows Examples 1 to 3 (left side) formed on a silicon substrate and an example (right side) in which a MoS ₂ film was formed at room temperature, 200 캜 and 400 캜, respectively, on a glass substrate.

10 is an image showing a MoS ₂ film formed on a 3 inch silicon wafer of some embodiments of the present invention. Sputtering of the MoS ₂ film can be successfully performed with a large area technique on 3 inch wafers.

Experimental Example 1

In order to examine the structural characteristics of the MoS2 film, X-ray diffraction (XRD) of Examples 1 to 3 was carried out and the surface morphology was photographed by FESEM.

11 is an X-ray diffraction (XRD) profile of the MoS ₂ films of Examples 1 to 3 of the present invention.

Referring to FIG. 11, the MoS ₂ films of Examples 1 and ₂ show a similar pattern. However, Example 3 shows a completely different pattern. Example 3 shows two major differences in the XRD patterns with Examples 1 and 2. The first is the width of the peak, and the second is the shift of the peak.

The size of the crystallites is an important factor that brings about the above two differences. In the MoS ₂ films of Examples 1 and ₂ , the crystallite size was in the range of a few nanometers, which broadened the peak of Fig. 11 and caused the out-of-plane of the (004) direction at 2? = 24 占-plane. < / RTI >

As the deposition temperature increases, the nanocrystallites agglomerate into larger grains and grow further in the form of a vertical film of MoS ₂ . Therefore, the highest peak of Example 3 is shifted to 2? = 13.5 ° corresponding to the (002) plane.

A low full width at half maximum (FWHM) of 1.3 ° demonstrates the high degree of crystallinity of Example 3. In addition, (00 l) the presence of a non-planar plane of good quality in the transition metal chalcogenide (TMD) refers to a texture.

FIG. 12 is an FESEM image showing the surface morphology of the MoS ₂ film of Example 1 of the present invention, and FIG. 13 is an FESEM image showing the morphology of the MoS ₂ film of Example 2 of the present invention. 14 is an FESEM image showing the surface morphology of the MoS ₂ film of Example 3 of the present invention.

Referring to Figures 12-14, the MoS ₂ film at each temperature level shows a unique, distinct surface morphology. In Example 1, the grain size is small and a horizontal film is formed (FIG. 12).

The temperature in Example 2 raised to 200 ℃, horizontal film of MoS ₂ is converted into a closely filled filled vertical structure of MoS ₂ with each other (Fig. 13). In Example 3, in which the temperature further increased to 400 캜, the MoS ₂ film in which the interlayer distance was increased and the density of the vertical structure was reduced can be confirmed (Fig. 14).

It can be seen that Example 2 and Example 3 at a high temperature grow uniformly with the edge face of the vertically grown MoS ₂ film facing upward. This may be an active surface for improving field emission characteristics. The structural form of this MoS ₂ film is in good agreement with the above XRD profile. Thus, it can be seen that the method introduced in this invention is a straightforward and simple method of depositing a vertical MoS ₂ film.

Experimental Example 2

Structural changes with temperature can have a significant effect on optical properties. In order to examine the optical properties of Examples 1 to 3, the degree of absorption was measured. FIG. 15 is a graph showing the absorption of MoS ₂ films according to Examples 1 to 3 according to wavelengths of the present invention. FIG.

Referring to FIG. 15, the absorbances of Examples 1 to 3 increase as the deposition temperature of the MoS ₂ film increases. The density of the vertically aligned MoS ₂ film of Example 2 is greater than the density of the vertically aligned MoS ₂ film of Example 3. Nevertheless, the average absorbance of Example 2 is only 28.47% compared to 53.68% of Example 3 for incident light in the range of 380-600nm. Thus, the enhancement of the absorption is not only determined by the density of the MoS ₂ film, but also by the length of vertically aligned films. The transfer to the junction through the long vertical film of the charge carriers or photons is very fast.

Experimental Example 3

In order to investigate the photoreaction of Example 3, photocurrent generation, response time, and detectability were examined. The photoreaction with time was measured after exposing light of different wavelengths to the photodetector of Example 3 of the present invention. The lights of different wavelengths may be 455 nm, 515 nm and 620 nm LED light corresponding to blue, green and red colors, respectively. At the zero bias voltage, the photoreaction was measured under the LED conditions, which are turned on and off in real time.

FIG. 16 is a diagram showing a photoreaction at a wavelength of 455 nm of a photodetector according to Embodiment 3 of the present invention, and FIG. 17 is a diagram showing a photoreaction at a wavelength of 515 nm of a photodetector according to Embodiment 3 of the present invention. 18 is a diagram showing the photoreaction at a wavelength of 620 nm of the photodetector of Example 3 of the present invention.

16 to 18, when the wavelength is 620 nm, the photocurrent of 130 μA is generated in the third embodiment. This is a very high value at zero bias. This is due to the rapid transfer of the charge carriers by the large volume of the edge face of the vertically aligned MoS ₂ film.

Speed and durability are important factors that determine the overall performance of the photodetector. As a result, the rise and fall times of the photocurrent signal were measured.

19 is a table summarizing a rise time and a fall time with respect to a wavelength of a photodetector according to the third embodiment of the present invention.

The rise time was measured as the time taken for the photocurrent value of the photodetector to increase from 10% to 90% of the peak value. The decay time or fall time was measured to the contrary (ie, the time it takes to decrease from 90% to 10%).

Referring to FIG. 19, the photodetector of Embodiment 3 is shown to provide a steady and quick response to incoming photons. The photodetector of Example 3 produces a photocurrent of 63 μA within a short time of 38.78 μs in the 455 nm wavelength region and reduces it within 43.07 μs. This is because the conventional MoS ₂ It is characterized by a very high reaction rate as compared with the techniques using a film, and also has a feature of operating without the help of an external bias (or bias).

20 is a table comparing the characteristics of the photodetector of the third embodiment of the present invention with the conventional photodetector. This difference is clearly shown in Fig.

FIG. 21 is a graph showing the photocurrent according to the intensity of light with respect to incident light of blue color of the photodetector according to the third embodiment of the present invention, FIG. 22 is a graph showing the photocurrent according to the green color of the photodetector according to the third embodiment of the present invention FIG. 3 is a graph showing photocurrent according to intensity of light. FIG. 23 is a graph showing photocurrent according to intensity of light with respect to incident light of red color of the photodetector of Example 3 of the present invention.

Referring to FIGS. 21 to 23, photocurrent increases linearly as the intensity of light increases. The graphs of Figures 21 to 23 are in good agreement with the power law of I _p aP ^[theta ]. Where Ip is photocurrent, P is intensity of light, and [theta] is a proportional constant. The linearity of the photocurrent according to the intensity of incident light means that the upper surface of the MoS ₂ film of the photodetector of Example 3 has a low defect.

FIG. 24 is a diagram showing the response and detection performance of the photodetector according to the third embodiment of the present invention at a wavelength of 455 nm, FIG. 25 is a graph showing the response of the photodetector according to the third embodiment of the present invention at a wavelength of 515 nm, Fig. 26 is a chart showing the response and detection ability of the photodetector according to the third embodiment of the present invention at a wavelength of 620 nm.

The responsivity (R) and detectability (D ^* ) of the photodetector of Example 3 are calculated as a function of light intensity with respect to the three target wavelengths shown in FIGS.

Referring to FIGS. 24 to 26, the response chart shows photocurrent generated by the photodetector per unit power of light intensity in a specific wavelength region. This is measured by the relationship of R = I _p / P _in . Where I _p and P _in are the photocurrent and the intensity of the incident light, respectively. The photodetector of Example 3 produces a steady photocurrent under the conditions of changing incident light. As the intensity of light increases at 455 nm, the response initially increases and then maintains a constant photocurrent. Stable photocurrent in the range of the power of the incident light of green color is important in the X-ray analyzer. When the wavelength is 620 nm, the response increases as the intensity of light decreases. When the wavelength increases from blue color to red color, the response of the photodetector of Example 3 decreases from 30 mA / W to 10 mA / W.

A similar phenomenon is also found in the detectability of the photodetector of Example 3. Detection performance is an important factor in determining its ability to detect weak light signal under a noisy condition of the photodetector, the MoS ₂ in the device _{^{D * = R / (2qJ d}} ) excellent detection performance through the relational expression of ^1/2 Respectively. This is because the quality of the MoS2 film is excellent, and has a low J _d (dark current density) value and a high response. This is calculated by the relationship of D ^* = R / (2qJ _d ) ^1/2 . Where J _d is the dark current density. In the above relationship, a high response degree and a low dark current density result in a high detection capability.

As described above, the degree of response varies from 10 to 30 mA / W at the zero bias voltage. Furthermore, the noise level typically measured at the reverse saturation current is measured at a very low 3μA. Therefore, in the absence of bias, the detection capability is measured at 10 ⁹ to 10 ¹⁰ Jones, which means that the MoS ₂ photodetector is sensitive to very weak incident signals as in Example 3.

In previously reported results, photodetectors based on MoS ₂ require most or often external bias for operation.

On the other hand, the present invention shows rapid reaction and high stability as shown in some embodiments because 1) the uniform vertical growth of MoS2 leaves absorbs more photons and 2) the vertical structure of MoS2 Speed path is provided.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It can be understood that It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: substrate 200: lower contact
300: molybdenum sulfide film 400: upper contact

Claims (19)

Board;
A molybdenum sulfide film formed on the substrate and grown in a vertical direction;
An upper contact formed on the molybdenum sulfide film; And
And a lower contact formed under the substrate. The method according to claim 1,
Wherein the molybdenum sulfide film comprises MoS ₂ . The method according to claim 1,
Wherein the substrate comprises Si. The method according to claim 1,
Wherein the lower contact includes a metal such as Al. The method according to claim 1,
Wherein the upper contact includes at least one of a metal such as Al, a transparent conductive layer, and a metal nanowire. The method according to claim 1,
The molybdenum sulfide film includes an upper surface and a side surface,
Wherein the molybdenum sulfide film grows on the top surface but does not grow on the side surface. The method according to claim 1,
Wherein the upper contact is formed in a grid shape. Providing a substrate comprising opposing first and second surfaces,
Forming a lower contact on the second surface,
Depositing a molybdenum sulfide film on the first surface at a first temperature,
And forming an upper contact on the molybdenum sulfide film. 9. The method of claim 8,
Wherein the substrate comprises Si. 10. The method of claim 9,
Wherein the substrate and the molybdenum sulfide film are combined to form a rectilinear junction. 9. The method of claim 8,
Wherein the first temperature is from room temperature to 600 ° C. 9. The method of claim 8,
Further comprising performing a rapid thermal process (RTP) to enhance bonding between the upper electrode and the lower electrode. 13. The method of claim 12,
Wherein the rapid thermal annealing is performed for a first time,
Wherein the first time is from 5 minutes to 60 minutes. 13. The method of claim 12,
Wherein the temperature of the rapid thermal annealing is 100 to 1000 ° C. 9. The method of claim 8,
The deposition of the molybdenum sulfide film,
And growing the molybdenum sulfide film in a vertical direction. 16. The method of claim 15,
The molybdenum sulfide film grows preferentially in the vertical direction,
Wherein the growth rate of the molybdenum sulfide film in the vertical direction is larger than the growth rate in the horizontal direction. 9. The method of claim 8,
Forming the upper contact,
And forming the upper contact in a grid shape. 9. The method of claim 8,
Wherein a horizontal area of the upper contact is smaller than a horizontal area of the lower contact. 9. The method of claim 8,
Wherein the molybdenum sulfide film comprises MoS ₂ .

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