Photo detector

Abstract

The present disclosure relates to a photodetector comprising: a substrate comprising a crystalline semiconductor; an ohmic electrode disposed on the substrate and ohmic-bonded to the substrate; and a Schottky electrode disposed on the substrate and Schottky-bonded to the substrate, wherein when the surface of the substrate in contact with the ohmic electrode is observed by electron beam backscattering analysis, the surface reveals a (-201) crystal plane.

Description

Technology Field

[0001] The present disclosure relates to a photodetector. Background Technology

[0002] A photodetector is an optoelectric device that operates according to the principle of the photoelectric effect, which was discovered by Einstein in 1905. Generally, a photodetector is formed with a structure comprising an active film sandwiched between two contact electrodes. This active film consists of a photoreactive material that absorbs photon energy from the outside and generates electron-hole pairs (EHPs) through inter-band transitions or energy level transitions within the forbidden band. Photogenerated carriers induced by light are collected at the contact electrodes and provide a photo-induced current to an external circuit. Typical materials for such photoreactive materials include Ge, Si, GaAs, GaP, PbS, InSb, CdSe, CdS, and CdTe.

[0003] Crystal orientation must be considered when manufacturing photodetectors. In the case of crystalline semiconductors, atomic arrangement, defect density, interatomic bond length, and bond energy can vary depending on the crystal plane, and consequently, the band gap and surface barrier height can differ. The problem to be solved

[0004] The problem that the present disclosure aims to solve is to provide a photodetector with reduced contact resistance.

[0005] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description of the invention below. means of solving the problem

[0006] A photodetector according to the present disclosure comprises: a substrate comprising a crystalline semiconductor; an ohmic electrode disposed on the substrate and ohmic-bonded to the substrate; and a Schottky electrode disposed on the substrate and Schottky-bonded to the substrate; wherein, when the surface of the substrate in contact with the ohmic electrode is observed by electron beam backscattering analysis, the surface reveals a (-201) crystal plane.

[0007] The above substrate may include at least one of gallium oxide and gallium nitride.

[0008] The ohmic electrode includes an ohmic finger extending toward the Schottky electrode; and the Schottky electrode may include a Schottky finger extending toward the ohmic electrode.

[0009] The above ohmic finger and the above Schottky finger may each be provided in multiple numbers.

[0010] The plurality of ohmic fingers and the plurality of shortkey fingers can be arranged alternately.

[0011] The substrate includes an ohmic region in which the ohmic electrode is disposed, and the ohmic region may include a trench region in which the substrate is recessed inward.

[0012] The above ohmic electrode can be stacked on the ohmic region to form a step.

[0013] The ohmic electrode and the Schottky electrode may each be composed of one or more materials selected from the group consisting of titanium (Ti), nickel (Ni), gold (Au), titanium-gold (Ti / Au), nickel-gold (Ni / Au), tungsten (W), molybdenum (Mo), tantalum (Ta), titanium silicide (TiSi), tantalum silicide (TaSi), aluminum (Al), aluminum-copper alloy (Al-Cu), aluminum-copper-silicon alloy (Al-Cu-Si), tungsten silicide (WSi), copper (Cu), and tungsten-titanium (TiW).

[0014] The thickness of the ohmic electrode and the Schottky electrode may each be 50 nm or more and 200 nm or less. Effects of the invention

[0015] According to one embodiment of the present disclosure, a photodetector with reduced contact resistance can be provided.

[0016] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by a person skilled in the art from the description of the invention below. Brief explanation of the drawing

[0017] FIGS. 1 to 3 illustrate a photodetector according to one embodiment of the present disclosure. Figure 4 shows a view of a region of Figure 1 measured using an atomic force microscope (AFM). Figure 5 illustrates step difference data calculated based on Figure 4. FIG. 6 illustrates a substrate and an ohmic electrode according to one embodiment of the present disclosure. Figure 7 shows the contact resistance of a substrate by crystal plane measured by the TLM method (transmission line method). Figure 8 illustrates the current-voltage characteristics of a photodetector with a trench junction and a photodetector without a trench junction, depending on the presence or absence of ultraviolet irradiation. Figure 9 illustrates the photoresponsivity over time of a photodetector with a trench junction and a photodetector without a trench junction. Figure 10 shows the average photoresponse and standard deviation of a photodetector with a trench junction and a photodetector without a trench junction. Specific details for implementing the invention

[0018] Hereinafter, the present disclosure will be described in detail with reference to the attached drawings. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively.

[0019] Specific terms used in this specification are for convenience of explanation only and are not intended to limit the exemplified embodiments.

[0020] For example, expressions such as "identical" and "to be identical" indicate not only a strictly identical state, but also a state where tolerances or differences exist in the degree to which the same function is obtained.

[0021] For example, expressions indicating relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "perpendicular," "to the center," "concentric," or "coaxial," not only strictly represent such arrangements but also indicate a state of relative displacement with respect to tolerances or angles or distances to which the same function is obtained.

[0022] To explain the present disclosure, the following description is based on a spatial orthogonal coordinate system formed by mutually orthogonal X-axis, Y-axis, and Z-axis. Each axis direction (X-axis direction, Y-axis direction, Z-axis direction) refers to the two directions in which each axis extends.

[0023] The X, Y, and Z directions mentioned below are for the purpose of explanation to ensure a clear understanding of the present disclosure, and it goes without saying that each direction may be defined differently depending on where the reference is placed.

[0024] The use of terms such as 'first, second, third' attached to the components mentioned below is intended solely to avoid confusion regarding the components being referred to, and is unrelated to the order, importance, or master-subordinate relationship between the components. For example, an invention including only the second component without the first component can be implemented.

[0025] The terms used in this disclosure are for the description of specific embodiments and are not intended to limit the claims. As used in the description of embodiments and in the appended claims, the singular form is intended to include the plural form unless the context clearly indicates otherwise.

[0027] FIGS. 1 to 3 illustrate a photodetector according to one embodiment of the present disclosure. Specifically, FIG. 1 illustrates a photodetector (1) viewed from above, FIG. 2 illustrates a photodetector viewed from the front, and FIG. 3 illustrates a photodetector viewed from the rear.

[0028] A photodetector (1) according to one embodiment of the present disclosure comprises: a substrate (100) including a crystalline semiconductor; an ohmic electrode (200) disposed on the substrate (100) and ohmic-bonded to the substrate (100); and a Schottky electrode (300) disposed on the substrate (100) and Schottky-bonded to the substrate (100). When the surface of the substrate (100) in contact with the ohmic electrode (200) is observed using electron beam backscattering analysis, the surface reveals a (-201) crystal plane.

[0029] Referring to FIGS. 1 to 3, the substrate (100) can form a support that provides structural rigidity to the photodetector (1). Additionally, the doping characteristics of the substrate (100) can be adjusted to enable electron movement necessary for the operation of the photodetector (1) and to enable ohmic junctions or Schottky junctions. On one side of the substrate (100), a layer having a different function can be laminated through thin film deposition, lithography, etc. The performance of the photodetector (1) may vary depending on the shape, thickness, and bonding structure of the layer formed on one side of the substrate (100).

[0030] The above substrate (100) may include at least one of gallium oxide and gallium nitride.

[0031] An ohmic electrode (200) and a Schottky electrode (300) may be disposed on the substrate (100). The ohmic electrode (200) may be ohmic-bonded to the substrate (100). When an N-type semiconductor is used as the substrate (100), the work function of the ohmic electrode (200) may be lower than the work function of the substrate (100).

[0032] The Schottky electrode (300) can be Schottky joined with the substrate (100). When an N-type semiconductor is used as the substrate (100), the work function of the Schottky electrode (300) may be greater than the work function of the substrate (100).

[0033] The substrate (100) may include a crystalline semiconductor. In the case of a crystalline semiconductor, the atomic arrangement, defect density, interatomic bond length, and bond energy may vary depending on the crystal plane. As a result, the band gap and surface barrier height may vary. The performance of the photodetector (1) may vary depending on the crystal plane formed between the substrate (100) and the ohmic electrode (200) or between the substrate (100) and the Schottky electrode (300).

[0034] When the photodetector (1) of the present disclosure observes the surface of the substrate (100) in contact with the ohmic electrode (200) using electron beam backscattering analysis, the surface of the substrate (100) may reveal a (-201) crystal plane.

[0035] Electron backscatter analysis is a method that uses a scanning electron microscope to analyze crystal structure, grain size, and crystal orientation. By using this method, high-energy electron beams are irradiated onto the sample surface, and the backscattered electrons scattered according to the crystal structure are analyzed to identify the sample's crystal structure, grain size, microstructure, and deformation state.

[0036] If the surface of the substrate (100) has a (-201) crystal plane, the contact resistance formed between the substrate (100) and the ohmic electrode (200) can be reduced. In other words, if the surface of the substrate (100) is formed with a (-201) crystal plane, it can exhibit lower contact resistance than if the surface of the substrate (100) is formed with (001), (100), (101), (102), (201), or (010) crystal planes.

[0037] The photodetector (1) of the present disclosure can be formed by considering the anisotropy present in the crystalline semiconductor, unlike the method of plasma treatment on the surface of the semiconductor substrate (100) or selecting a metal by considering the Fermi level of the semiconductor.

[0038] Referring again to FIGS. 1 to 3, the ohmic electrode (200) includes an ohmic finger (210) extending toward the Schottky electrode (300), and the Schottky electrode (300) may include a Schottky finger (310) extending toward the ohmic electrode (200).

[0039] The above ohmic finger (210) and the above Schottky finger (310) can each be multiple.

[0040] The plurality of ohmic fingers (210) and the plurality of Schottky fingers (310) may be arranged alternately. Referring to FIG. 1, the ohmic fingers (210) and the Schottky fingers (310) may be arranged alternately along the direction from the front to the rear of the photodetector (1).

[0041] The ohmic electrode (200) includes a plurality of ohmic fingers (210) extending toward the Schottky electrode (300), and the Schottky electrode (300) includes a plurality of Schottky fingers (310) extending toward the ohmic electrode (200), thereby minimizing the gap between the electrodes while maximizing the contact area of ​​both electrodes. This finger structure can contribute to improving the photoresponse characteristics and response speed of the photodetector by improving the collection efficiency of photogenerated charge carriers and reducing recombination losses.

[0042] In addition, the finger structure is formed on the (-201) crystal surface of the substrate (100) to simultaneously secure low contact resistance and stable electrical contact characteristics, which can be advantageous for implementing a photodetector with high sensitivity.

[0043] Meanwhile, the substrate (100) and the ohmic electrode (200) may be trench-contacted. Here, trench contact refers to the physical contact structure between the substrate (100) and the ohmic electrode (200), rather than being related to the work function. Through trench contact, the contact area between the substrate (100) and the ohmic electrode (200) can be increased, and the photoelectric conversion efficiency can be improved.

[0044] Referring to FIGS. 2 and 3, the substrate (100) includes an ohmic region in which the ohmic electrode (200) is disposed, and the ohmic region may include a trench region in which the substrate (100) is recessed inward.

[0045] The ohmic electrode (200) may be deposited on the ohmic region. At this time, the deposition of the ohmic electrode (200) may begin in the trench region while being recessed inward from the surface of the substrate (100). As a result, the ohmic electrode (200) may be stacked on the ohmic region to form a step.

[0046] Referring to FIG. 1, areas marked with different colors on the ohmic electrode (200) are identified. This is because the refractive index changes due to the step difference of the ohmic electrode (200), and it is confirmed that a step difference is formed on the ohmic electrode (200).

[0047] Figure 4 shows a measurement of one region of Figure 1 using an atomic force microscope (AFM), and Figure 5 shows step difference data calculated based on Figure 4.

[0048] Specifically, FIG. 4 shows the area where the trench structure was formed through the etching of FIG. 1 as measured by an atomic force microscope. FIG. 5 shows only the step difference data of the line parallel to the X-axis extracted from the image of FIG. 4 and plotted as a graph.

[0049] The ohmic electrode (200) and the Schottky electrode (300) may each be composed of one or more selected from the group consisting of titanium (Ti), nickel (Ni), gold (Au), titanium-gold (Ti / Au), nickel-gold (Ni / Au), tungsten (W), molybdenum (Mo), tantalum (Ta), titanium silicide (TiSi), tantalum silicide (TaSi), aluminum (Al), aluminum-copper alloy (Al-Cu), aluminum-copper-silicon alloy (Al-Cu-Si), tungsten silicide (WSi), copper (Cu), and tungsten-titanium (TiW).

[0050] Preferably, the ohmic electrode (200) may include titanium and gold, and the Schottky electrode (300) may include nickel and gold. Although the ohmic electrode (200) and the Schottky electrode (300) are shown as being laminated with one metal in FIGS. 2 and FIGS. 3, it is obvious that the ohmic electrode (200) and the Schottky electrode (300) may be formed by using multiple metals and each of the multiple metals being laminated.

[0051] For example, the ohmic electrode (200) may be formed by first stacking titanium on the substrate (100) and then stacking gold on the titanium. The Schottky electrode (300) may be formed by first stacking nickel on the substrate (100) and then stacking gold on the nickel.

[0052] The thickness of the ohmic electrode (200) and the Schottky electrode (300) may be 50 nm or more and 200 nm or less, respectively. When two different metals are used, the stacking thickness of each of the two different metals may be different. The stacking thickness of the metal that is first stacked on the substrate (100) may be thicker than the stacking thickness of the metal that is later stacked.

[0053] For example, the ohmic electrode (200) may be formed by stacking 50 nm of titanium on the substrate (100) and then stacking 100 nm of gold on the titanium. The Schottky electrode (300) may be formed by stacking 50 nm of nickel on the substrate (100) and then stacking 100 nm of gold on the nickel.

[0054] FIG. 6 illustrates a substrate (100) and an ohmic electrode (200) according to one embodiment of the present disclosure, and FIG. 7 illustrates the contact resistance of the substrate (100) by crystal plane measured through the TLM method (transmission line method).

[0055] When manufacturing the substrate (100), the crystal planes of the substrate (100) can first be identified through electron beam backscattering analysis. Referring to FIG. 6a, once the crystal planes of the substrate (100) are identified, platinum catalysts corresponding to each crystal plane can be patterned. Referring to FIG. 6b, photo-enhanced metal catalyst wet etching can be performed on the substrate (100). At this time, each substrate (100) is immersed in an etching solution of HF (28 mM) and K2S2O8 (10 mM), and UV-C (288.6 μW cm⁻¹) with a wavelength of 185 nm is applied. -2 ) can be investigated. Referring to Fig. 6c, a substrate (100) having a specific crystal plane can be formed by removing the platinum total solvent from aqua regia after etching. Finally, referring to Fig. 6d, an ohmic electrode (200) can be deposited on the substrate (100).

[0056] Referring to FIG. 7, for each crystal plane, a transmission line method (TLM) pattern with channel lengths of 5, 10, 1, 20, 25, and 30 μm can be fabricated to measure the contact resistance. For the surface contact (010) plane, the contact resistance is 5.23 kΩ mm, for the plane contact (001) plane it is 1.37 kΩ mm, for the plane (101) plane it is 1.70 kΩ mm, for the plane (102) plane it is 3.83 kΩ mm, for the plane (201) plane it is 0.66 kΩ mm, and for the plane (-201) plane it is 0.23 kΩ mm. Through this, it is confirmed that the contact resistance can be improved in the case of a plane contact that exposes the (-201) crystal plane.

[0057] Figure 8 illustrates the current-voltage characteristics of a photodetector with a trench junction and a photodetector without a trench junction according to the presence or absence of ultraviolet irradiation, Figure 9 illustrates the photoresponsivity over time of a photodetector with a trench junction and a photodetector without a trench junction, and Figure 10 illustrates the average photoresponsivity and standard deviation of a photodetector with a trench junction and a photodetector without a trench junction.

[0058] For the measurement, ultraviolet light with a wavelength of 254 nm and an irradiation intensity of 1.3 W / m² was used, and the irradiation intensity was set to approximately 1.3 W / m².

[0059] In Fig. 8, the solid line represents the characteristics of a photodetector with a trench junction formed in the non-UV irradiation state, and the dotted line represents the characteristics of the same photodetector with UV irradiation state. On the other hand, the dotted line represents the characteristics of a photodetector without a trench junction formed in the non-UV irradiation state, and the dotted line represents the characteristics of a photodetector with a UV irradiation state.

[0060] In the absence of UV irradiation, the dark current of both photodetectors is maintained at a low level due to the Schottky barrier formed by the Schottky electrode. Meanwhile, when irradiated with UV, the photodetector with the trench junction (2-dot dashed line) exhibits a photocurrent approximately three times higher than that of the photodetector without the trench junction (1-dot dashed line). This is because the trench junction formed on the (-201) crystal plane has lower contact resistance than the planar junction formed on the (010) crystal plane, which can improve photoresponsiveness.

[0061] In Fig. 9, measurements were performed by periodically irradiating with ultraviolet light of a wavelength of 254 nm and an irradiation intensity of 1.3 W / m² under a 0 V bias condition. Referring to Fig. 7, during the periodic irradiation and removal of ultraviolet light, the photocurrent of both photodetectors rapidly rises and falls, exhibiting a repeatedly stable response. These results demonstrate that both photodetectors operate stably without persistent photoconductivity (PPC) phenomena.

[0062] In addition, the photodetector with the trench junction (Device 1) exhibits a photocurrent approximately three times higher than that of the photodetector without the trench junction (Device 2). This result is consistent with the current-voltage characteristics confirmed in Figure 6, further demonstrating that the trench junction structure effectively improves the photoresponse characteristics of the photodetector.

[0063] In Fig. 10, the measurement was performed by irradiating with ultraviolet light of a wavelength of 254 nm and an irradiation intensity of 1.3 W / m² under a 0 V bias condition. Referring to Fig. 8, the photodetector with the trench junction exhibits a photoresponse of approximately 13 mA / W, which is more than three times higher than the approximately 4.5 mA / W of the photodetector without the trench junction. Furthermore, despite the high response characteristics, the photodetector with the trench junction maintains a small standard deviation, confirming that it is a structure capable of simultaneously ensuring high performance and reproducibility.

[0064] On the other hand, photodetectors without trench junctions exhibit relatively low photoresponse, indicating clear limitations in performance levels.

[0065] The present disclosure may be modified and implemented in various forms, and the scope of rights is not limited to the embodiments described above. The contents described above are merely examples applying the principles of the present disclosure, and other configurations may be further included without departing from the scope of the present invention. Explanation of the symbols

[0067] 100: Substrate 200: Ohmic electrode 300: Schottky electrode

Claims

Claim 1 A substrate comprising a crystalline semiconductor; an ohmic electrode disposed on the substrate and ohmic-junctioned with the substrate; The apparatus comprises a Schottky electrode disposed on the substrate and Schottky bonded to the substrate, wherein when the surface of the substrate in contact with the ohmic electrode is observed by electron beam backscattering analysis, the surface reveals a (-201) crystal plane, the substrate comprises at least one of gallium oxide and gallium nitride, the ohmic electrode comprises an ohmic finger extending toward the Schottky electrode, the Schottky electrode comprises a Schottky finger extending toward the ohmic electrode, the ohmic finger and the Schottky finger are each provided in a plurality, the substrate comprises an ohmic region on which the ohmic electrode is disposed, the ohmic region comprises a trench region in which the substrate is recessed inward, the substrate and the ohmic electrode are trench bonded, the trench bond is formed on the (-201) crystal plane, the ohmic electrode is stacked on the ohmic region to form a step, and the thickness of the ohmic electrode and the Schottky electrode is each 50 nm or more. A photodetector characterized by having a thickness of 200 nm or less, wherein the ohmic electrode and the Schottky electrode are each composed of one or more materials selected from the group consisting of titanium (Ti), nickel (Ni), gold (Au), titanium-gold (Ti / Au), nickel-gold (Ni / Au), tungsten (W), molybdenum (Mo), tantalum (Ta), titanium silicide (TiSi), tantalum silicide (TaSi), aluminum (Al), aluminum-copper alloy (Al-Cu), aluminum-copper-silicon alloy (Al-Cu-Si), tungsten silicide (WSi), copper (Cu), and tungsten-titanium (TiW). Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 In claim 1, the plurality of ohmic fingers and the plurality of Schottky fingers are alternately arranged in a photodetector. Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete

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