Gallium nitride-based radiation detector

Abstract

The present invention relates to a GaN-based radiation detector capable of detecting radiation such as X-rays. The GaN-based radiation detector comprises: an n-doped GaN layer with an n-type doping concentration of 3x1016 / cm3 or less, which has an electron mobility of 700 cm2 / (V·s) or higher and a thickness of 300 um or greater; a p-doped GaN layer with a p-type doping concentration of 5x1018 / cm3 or more, which is formed on one surface of the n-doped GaN layer and has a thickness of 3 um or less; a first metal junction formed on the other surface of the n-doped GaN layer; and a second metal junction formed on one surface of the p-doped GaN layer.

Description

gallium nitride radiation detector

[0001] The present invention relates to a gallium nitride (GaN)-based radiation detector capable of detecting radiation such as X-rays.

[0002] Most current direct-transition radiation detectors are manufactured from α-Se (amorphous selenium) or CdTe (cadmium telluride). However, α-Se is known to be very expensive to manufacture, and cadmium is a heavy metal that is highly hazardous to the human body. To address these issues, the development of direct-transition semiconductor radiation detectors is urgently needed.

[0003] Materials suitable for direct-transition radiation detectors include GaAs (gallium arsenide), SiC (silicon carbide), Ga2O3 (gallium oxide), and GaN (gallium nitride). However, considering its radiation resistance, efficiency as a direct-transition semiconductor, and process convenience, GaN is known to be the best alternative.

[0004] Recently, in the research field of GaN-based radiation detectors, many results have been reported proving their advantages as radiation detectors, and in particular, they have been reported to be able to appropriately detect ultraviolet rays, neutrons, and X-rays.

[0005] Most existing GaN-based radiation detectors are formed by epitaxial growth using processes such as MOCVD (metal organic chemical vapor deposition) on sapphire (Al2O3) or silicon carbide (SiC) substrates. However, the growth thickness is thin, less than 30 μm. This results in a thin drift layer, where electrons and holes are generated by incident radiation. This thin drift layer, which must be utilized, has the disadvantages of reduced efficiency and a complex structure. This is due to limitations in the growth method, and since the drift layer must have very high electron mobility, it must have a low impurity or doping concentration. Furthermore, defects caused by differences in lattice constants due to growth on heterogeneous substrates and the incorporation of impurities during crystal growth increase the doping concentration, which causes a decrease in detector efficiency and response speed. A method that can solve these problems and manufacture a GaN-based radiation detector with improved efficiency and response speed is required.

[0006] The matters described in the technical background of this invention are written to enhance understanding of the background of the invention and may include matters that are not already known in the field to which this technology belongs.

[0007] -Prior art document: U.S. Patent No. US9,402,548 (August 2, 2016)

[0008] The problem to be solved by the present invention is to provide a GaN-based radiation detector capable of improving efficiency, improving response speed, and implementing a simple structure.

[0009] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0010] A GaN-based radiation detector according to an embodiment of the present invention has a wavelength of 700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3 An n-doped GaN layer doped with a doping concentration below; formed on one surface of the n-doped GaN layer and having a thickness of 3 μm or less and a p-type of 5x10 18 / cm 3 A p-doped GaN layer doped with a doping concentration above; a first metal junction formed on the other side of the n-doped GaN layer; and a second metal junction formed on one side of the p-doped GaN layer.

[0011] A GaN-based radiation detector according to another embodiment of the present invention has a wavelength of 700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3 An n-doped GaN layer doped with a doping concentration below; formed on one side of the n-doped GaN layer and having a p-type thickness of 5x10 18 / cm 3 A first p-doped GaN layer doped with a first p-doping concentration above; formed on one surface of the first p-doped GaN layer and having a p-type doping concentration greater than the first p-doping concentration of 5x10 19 / cm 3 A second p-doped GaN layer doped with a second doping concentration above; a first metal junction formed on the other side of the n-doped GaN layer; and a second metal junction formed on one side of the second p-doped GaN layer.

[0012] According to another embodiment of the present invention, a GaN-based radiation detector has a wavelength of 700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3An n-doped GaN layer doped with a doping concentration below; formed on one side of the n-doped GaN layer and having a p-type thickness of 5x10 18 / cm 3 5x10 20 / cm 3 A plurality of p-doped GaN layers having a thickness of 1 μm or less, which are sequentially doped with different p-doping concentrations within a range; a first metal junction formed on another surface of the n-doped GaN layers; and a second metal junction formed on one surface of the plurality of p-doped GaN layers.

[0013] A portion of the above p-doped GaN layer may be a structure that can be removed.

[0014] At least a portion of one surface of the above n-doped GaN layer may have a rough structure.

[0015] The defect concentration of the above n-doped GaN layer is 5x10 6 / cm 2 It could be as follows:

[0016] According to another embodiment of the present invention, a GaN-based radiation detector has a wavelength of 700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3 A first n-doped GaN layer doped with a doping concentration below; formed on one surface of the first n-doped GaN layer and having a thickness of 5 μm or less and an n-type of 5x10 17 / cm 3 A second n-doped GaN layer doped with a doping concentration above; a first metal junction formed on the other side of the first n-doped GaN layer; and a second metal junction formed on one side of the second n-doped GaN layer.

[0017] A portion of the second n-doped GaN layer may be a structure that can be removed.

[0018] At least a portion of the nitrogen surface of the above n-doped GaN layer can be formed to have a rough structure.

[0019] According to the present invention, a GaN-based radiation detector having improved efficiency and response speed can be implemented.

[0020] In addition, various effects that can be obtained or expected due to embodiments of the present invention are disclosed directly or implicitly in the detailed description of the embodiments of the present invention.

[0021] The accompanying drawings, which are intended to aid in understanding the present invention, provide embodiments of the present invention along with a detailed description. However, the technical features of the present invention are not limited to any specific drawings, and the features disclosed in each drawing may be combined to form new embodiments. The embodiments of the present specification may be better understood by referring to the following description in conjunction with the accompanying drawings, in which similar reference numerals designate identical or functionally similar elements.

[0022] FIG. 1 illustrates a schematic cross-sectional view of a GaN-based radiation detector according to an embodiment of the present invention.

[0023] FIG. 2 shows a modified example of a GaN-based radiation detector according to the embodiment of FIG. 1.

[0024] FIG. 3 shows another modified example of a GaN-based radiation detector according to the embodiment of FIG. 1.

[0025] FIG. 4 illustrates a schematic cross-sectional view of a GaN-based radiation detector according to another embodiment of the present invention.

[0026] FIG. 5 shows a modified example of a GaN-based radiation detector according to the embodiment of FIG. 4.

[0027] FIG. 6 shows another modified example of a GaN-based radiation detector according to the embodiment of FIG. 4.

[0028] FIG. 7 illustrates a schematic cross-sectional view of a GaN-based radiation detector according to another embodiment of the present invention.

[0029] FIG. 8 shows a modified example of a GaN-based radiation detector according to the embodiment of FIG. 7.

[0030] FIG. 9 shows another modified example of a GaN-based radiation detector according to the embodiment of FIG. 7.

[0031] FIG. 10 shows another modified example of a GaN-based radiation detector according to the embodiment of FIG. 7.

[0032] FIG. 11 shows another modified example of a GaN-based radiation detector according to the embodiment of FIG. 7.

[0033] It should be understood that the drawings referenced above are not necessarily drawn to scale and are intended to provide brief representations of various features that illustrate the fundamental principles of the present invention. For example, specific design features of the present invention, including specific dimensions, orientations, positions, and shapes, will be determined in part by the specific intended application and usage environment.

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the described embodiments.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It should also be understood that the terms "comprises" and / or "comprising," as used herein, indicate the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The term "coupled" indicates a physical relationship between two components in which the components are directly connected to one another or are indirectly connected through one or more intervening components.

[0036] In describing the components of the present invention, when it is described that a component is “connected,” “coupled,” or “connected” to another component, it should be understood that the component may be directly connected, coupled, or connected to the other component, but another component may also be “connected,” “coupled,” or “connected” between each component.

[0037] Currently, HVPE (hydride vapor phase epitaxy) is almost the only technology that can stack GaN layers thicker than 100 μm. However, the HVPE technology has been limited in its use due to the disadvantages of high doping concentration and low electron mobility caused by the mixing of impurities during growth. In particular, when growing a thick GaN drift layer using the HVPE method, there is a method to lower the concentration of n-type impurities by artificially mixing p-type impurities such as carbon (C) or iron (Fe) to prevent an increase in the concentration of n-type impurities due to the mixing of silicon (Si) or oxygen (O) impurities. However, this causes a decrease in efficiency and response speed due to the decrease in electron mobility. Therefore, basically, the n-type doping concentration through a technology that minimizes silicon or oxygen impurities during GaN growth using the HVPE method is 3x10 16 / cm 3 Electron mobility must also be reduced to 700 Cm 2 / (V·s) can be improved to more than that.

[0038] Recently, active research has been conducted on technologies for reducing silicon and oxygen impurities in HVPE growth. In particular, it has been reported that controlling these impurities is possible by replacing the quartz tube, the reactor material in the HVPE device, with a different material or by changing the source gas used for GaN growth.

[0039] Impurity reduction technology in GaN growth by HVPE allows n-type doping concentration to be 3x10 16 / cm 3 Below and electron mobility is 700 Cm 2Utilizing a GaN substrate with a thickness of 300 μm or more (V·s) as the drift layer can yield even greater results. Increasing the drift layer thickness promotes radiation absorption, allowing for greater current generation and faster response times through higher operating voltages. Furthermore, defect reduction reduces leakage current, thereby reducing signal noise and enhancing reliability. Furthermore, a thicker drift layer can generate more electron-hole pairs, allowing for simpler device structures.

[0040] In particular, when using a thick GaN substrate with low defects, low doping concentration, and high electron mobility, a thick drift layer and defect reduction effect can be naturally obtained, so that even if either the (p) GaN or (n+) layer is removed, the device can be manufactured as a simpler device with improved characteristics, and the manufacturing cost can also be reduced. In particular, a GaN-based radiation detector manufactured with this structure has a higher breakdown voltage than a conventional detector. Since the breakdown voltage of a device is determined by the doping concentration, defects, and thickness of the drift layer, a device with a higher breakdown voltage can be driven at a higher voltage, which facilitates electron movement at the Schottky junction that occurs between metal-semiconductor junctions.

[0041] In the conventional method, 5x10 on a sapphire or silicon carbide substrate 17 / cm 3 Although it is necessary to use the doped (n+) GaN layer, if a GaN substrate with a low impurity concentration is used, it is sufficient to remove the (n+) GaN layer and use only the Schottky contact. Also, 5x10 18 / cm 3The doped (p+) GaN layer can also be removed. This means that normal operation can be achieved with only one of the (n+) GaN and (p+) GaN layers. This is due to the advantage of high-voltage operation, which allows for Sharkey junctions. Furthermore, a surface roughness structure can be inserted to aid radiation absorption.

[0042] The GaN substrate used as a drift layer to manufacture devices for GaN-based radiation detectors reduces the n-type doping concentration and increases electron mobility by reducing silicon or oxygen impurities mixed in during manufacturing. At this time, the GaN substrate is 3x10 16 / cm 3 Below n-type doping concentration, 700 Cm 2 It is desirable to have an electron mobility of / (V·s) or more and a thickness of 300 μm or more. On the substrate prepared in this way, one layer of (p+) GaN or (n+) GaN is grown through MOCVD. A portion of the grown MOCVD epilayer is etched to form an electrode. In addition, a portion of one surface of the (n-) GaN layer can be etched with a rough structure using an etching method such as wet etching to increase the absorption rate of incident radiation.

[0043] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0044] Referring to Fig. 1, the GaN-based radiation detector (10) includes an n-type doped n-doped GaN layer (11), and the n-doped GaN layer (11) corresponds to a GaN substrate to be used as a drift layer. In order to improve the response speed and reliability, the n-doped GaN layer (11) is 3x10 n-type GaN layers. 16 / cm 3 It is formed by doping with a doping concentration below 700 cm 2 / (V·s) or more and a thickness of 300 μm or more. Furthermore, the defect concentration of the n-doped GaN layer (11) is 5x106 / cm 2 It could be as follows:

[0045] A p-doped GaN layer (13) is formed on the upper surface of the n-doped GaN layer (11), and for example, the p-doped GaN layer (13) can be formed by a method such as MOCVD. The p-doped GaN layer (13) is formed by forming a 5x10 p-type GaN layer. 18 / cm 3 It is formed by doping with the above doping concentration and has a thickness of 3 um or less.

[0046] Metal junctions (15, 17) acting as electrodes are formed on the lower surface of the n-doped GaN layer (11) and the upper surface of the p-doped GaN layer (13), respectively. The metal junction (15) formed on the lower surface of the n-doped GaN layer (11) acts as a cathode, and the metal junction (17) formed on the upper surface of the p-doped GaN layer (13) acts as an anode. Although not shown in the drawing, an electric signal generated by detection of radiation, for example, X-rays, can be generated through an electric circuit electrically connected to the cathode (15) and the anode (17).

[0047] The n-type doping described above can be achieved by n-type doping using silicon (Si) as a dopant, and silane (SiH4) can be used as a dopant source. In addition, p-type doping can be achieved by p-type doping using magnesium (Mg) as a dopant, and biscyclopentadienyl-magnesium can be used as a dopant source.

[0048] FIGS. 2 and 3 illustrate modified examples of the GaN-based radiation detector of FIG. 1. The same reference numerals are used for the same parts, and redundant descriptions are omitted. Referring to FIGS. 2 and 3, a portion of the p-doped GaN layer (13), for example, a central portion, may be removed. The removal of a portion of the p-doped GaN layer (13) may be accomplished through a process such as etching. At this time, the anode (17) may be formed to have a ring shape in the portion remaining after the partial removal, and the cathode (15) may be formed to have a larger area so as to cover the entire area occupied by the anode (17).

[0049] Meanwhile, referring to FIG. 3, a rough structure (19) may be formed on a portion of the n-doped GaN layer (11), for example, at least a portion of the bottom surface. Here, the bottom surface of the n-doped GaN layer (11) may be a nitrogen surface with a large exposure of nitrogen atoms. At this time, the cathode (15) may be formed on the rough structure (19). The absorption of radiation to be detected, for example, X-rays, may be increased by the rough structure (19). For example, the rough structure (19) may be formed through a process such as etching.

[0050] Referring to FIG. 4, a first p-doped GaN layer (21) and a second p-doped GaN layer (23) are sequentially formed on an n-doped GaN layer (11), which is the same GaN substrate as the embodiment of FIG. 1, and are doped with different p-doping concentrations. The first and second p-doped GaN layers (21, 23) can be formed by doping the GaN layer with a p-type. The first p-doped GaN layer (21) is formed on the upper surface of the n-doped GaN layer (11) and is 5x10 p-type. 18 / cm 3 The first p doping concentration may be doped above, and the second p-doped GaN layer (23) is formed on the upper surface of the first p-doped GaN layer (21) and is p-type with a thickness of 5x10 greater than the first p doping concentration. 19 / cm3 It can be doped with the second doping concentration above.

[0051] Metal junctions (15, 17) acting as electrodes can be formed on the lower surface of the n-doped GaN layer (11) and the upper surface of the second p-doped GaN layer (23), respectively, thereby forming a cathode and an anode.

[0052] According to another embodiment of the present invention, 5x10 p-type GaN layers (11) are formed on the n-doped GaN layer described above. 18 / cm 3 5x10 20 / cm 3 It can include multiple p-doped GaN layers having a thickness of 1 μm or less, which are successively doped with different p-doping concentrations within a range. In this case, the p-doped GaN layers can be doped to p-type with better p-doping concentrations as they go upward. For example, when two p-doped GaN layers are formed as shown in FIG. 4, the lower p-doped GaN layer has a thickness of 5x10 18 / cm 3 5x10 20 / cm 3 The p-doped GaN layer is doped with a p-doping concentration within the range, and the p-doped GaN layer above it is 5x10 19 / cm 3 5x10 20 / cm 3 It is doped with a p-doping concentration within the range. In another embodiment, three or more p-doped GaN layers may be formed sequentially.

[0053] FIGS. 5 and 6 illustrate modified examples of the GaN-based radiation detector of FIG. 4. The same reference numerals are used for the same parts, and redundant descriptions are omitted. Referring to FIGS. 5 and 6, a portion of the p-doped GaN layer (21, 23), for example, a central portion, may be removed. The removal of a portion of the p-doped GaN layer (21, 23) may be accomplished through a process such as etching. At this time, the anode (17) may be formed to have a ring shape in the portion remaining after the partial removal, and the cathode (15) may be formed to have a larger area so as to cover the entire area occupied by the anode (17).

[0054] Meanwhile, referring to FIG. 6, a rough structure (19) may be formed on a portion of the n-doped GaN layer (11), for example, at least a portion of the bottom surface.

[0055] FIG. 7 illustrates a GaN-based radiation detector according to another embodiment of the present invention. Referring to FIG. 7, the same n-doped GaN layer (11) as described above is provided, and an additional n-doped GaN layer (31) is formed on the lower surface of the n-doped GaN layer (11).

[0056] As described above, the n-doped GaN layer (11) is n-type and has a thickness of 3x10 16 / cm 3 Doped with a doping concentration below 700 cm 2 / (V·s) or more electron mobility and a thickness of 300 μm or more. The additionally formed n-doped GaN layer (31) has a thickness of 5 μm or less and is 5x10 of n-type. 17 / cm 3 It is doped with the above doping concentration.

[0057] Metal bonds (15, 17) are formed on the lower surface of the n-doped GaN layer (31) and the upper surface of the n-doped GaN layer (11), respectively, thereby forming a cathode and an anode.

[0058] FIGS. 8 and 9 illustrate modified examples of the GaN-based radiation detector of FIG. 7. The same reference numerals are used for the same parts, and redundant descriptions are omitted. Referring to FIGS. 8 and 9, a portion of the n-doped GaN layer (31), for example, a central portion, may be removed. The removal of a portion of the n-doped GaN layer (31) may be accomplished through a process such as etching. At this time, the cathode (15) may be formed to have a ring shape in the portion remaining after the partial removal, and the anode (17) may be formed to have a larger area so as to cover the entire area occupied by the cathode (15).

[0059] Meanwhile, referring to FIG. 9, a rough structure (19) may be formed on at least a portion of the bottom surface exposed by removal of a portion of the n-doped GaN layer (11), for example, a portion of the n-doped GaN layer (31). Here, the bottom surface of the n-doped GaN layer (11) may be a nitrogen surface where many nitrogen atoms are exposed.

[0060] FIGS. 10 and 11 illustrate other modified examples of the GaN-based radiation detector of FIG. 7. Referring to FIG. 10, the anode (17) may be formed to have a ring shape, and the cathode (15) may be formed to have a larger area corresponding to the entire area occupied by the anode (17).

[0061] Meanwhile, referring to FIG. 11, a part of the n-doped GaN layer (31), for example, the central portion, may be removed, and the cathode (15) may be formed to have a ring shape. A rough structure (19) may be formed on the upper surface of the n-doped GaN layer (11), which is a GaN substrate, and the anode (17) may be formed on the rough structure (19).

[0062] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. 700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3 An n-doped GaN layer doped with a doping concentration below; It is formed on one side of the above n-doped GaN layer and has a thickness of 3 um or less and is p-type and 5x10 18 / cm 3 A p-doped GaN layer doped with a doping concentration above; a first metal junction formed on the other side of the n-doped GaN layer; and A GaN-based radiation detector comprising a second metal junction formed on one surface of the p-doped GaN layer. 2.700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3 An n-doped GaN layer doped with a doping concentration below; It is formed on one side of the above n-doped GaN layer and is 5x10 p-type. 18 / cm 3 A first p-doped GaN layer doped with a first p-doping concentration above; It is formed on one side of the first p-doped GaN layer and is p-type and has a doping concentration of 5x10 greater than the first p doping concentration. 19 / cm 3 A second p-doped GaN layer doped with a second doping concentration above; a first metal junction formed on the other side of the n-doped GaN layer; and A GaN-based radiation detector comprising a second metal junction formed on one surface of the second p-doped GaN layer. 3.700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3 An n-doped GaN layer doped with a doping concentration below; It is formed on one side of the above n-doped GaN layer and is 5x10 p-type. 18 / cm 3 5x10 20 / cm 3 A plurality of p-doped GaN layers having a thickness of less than 1 μm, successively doped with different p-doping concentrations falling within a range; a first metal junction formed on the other side of the n-doped GaN layer; and A GaN-based radiation detector comprising a second metal junction formed on one surface of the plurality of p-doped GaN layers.

4. In any one of paragraphs 1 to 3, A GaN-based radiation detector having a structure in which a portion of the above p-doped GaN layer can be removed.

5. In any one of paragraphs 1 to 3, A GaN-based radiation detector having at least a portion of one surface of the n-doped GaN layer having a rough structure.

6. In any one of paragraphs 1 to 3, The defect concentration of the above n-doped GaN layer is 5x10 6 / cm 2 GaN-based radiation detectors. 7,700 cm 2 / (V·s) or more electron mobility and thickness of 300 um or more, n-type 3x10 16 / cm 3 A first n-doped GaN layer doped with a doping concentration below; It is formed on one side of the first n-doped GaN layer and has a thickness of 5 um or less and is n-type 5x10 17 / cm 3 A second n-doped GaN layer doped with a doping concentration above; a first metal junction formed on the other side of the first n-doped GaN layer; and A GaN-based radiation detector comprising a second metal junction formed on one surface of the second n-doped GaN layer.

8. In paragraph 7, A GaN-based radiation detector having a structure in which a portion of the second n-doped GaN layer can be removed.

9. In any one of paragraphs 1 to 3 and paragraph 7, A GaN-based radiation detector, wherein at least a portion of the nitrogen surface of the above n-doped GaN layer is formed to have a rough structure.

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