GaN-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 includes: an n-doped GaN layer having an n-type doping concentration of 3 * 1016 / cm < 3 > or less, an electron mobility of 700 cm < 2 > / (V.s) or more, and a thickness of 300 [mu] m or more; a p-doped GaN layer having a p-type doping concentration of 5 * 1018 / cm3 or more, formed on one surface of the n-doped GaN layer, and having a thickness of 3 [mu] m or less; a first metal joint formed on the other surface of the n-doped GaN layer; and a second metal joint formed on one surface of the p-doped GaN layer.

Description

Technical Field

[0001] The present invention relates to GaN (Gallium Nitride) based radiation detectors capable of detecting radiation such as X-rays. Background Art

[0002] Recently, most direct transition radiation detectors are made using α-Se (amorphous selenium) or CdTe (cadmium telluride) materials. As we all know, the manufacture of α-Se is very expensive and cadmium is a heavy metal that is very dangerous to the human body. In order to solve these problems, the development of direct semiconductor radiation detectors is urgent.

[0003] Materials such as GaAs (gallium arsenide), SiC (silicon carbide), Ga2O3 (gallium oxide), and GaN (gallium nitride) are being discussed as suitable materials for direct transition radiation detectors. However, considering durability under radiation, efficiency as a direct transition semiconductor, and process convenience, GaN is known to be the best alternative.

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

[0005] Since most existing GaN-based radiation detectors are formed by epitaxial growth on sapphire (Al2O3) or silicon carbide (SiC) substrates using an MOCVD (metal organic chemical vapor deposition) process, the growth thickness is thin, less than 30 μm, and therefore, the region where incident radiation generates electrons and holes, namely the drift layer, is thin. Due to the use of this thinner drift layer, it has the disadvantages of reduced efficiency and complex structure. This is due to limitations in the growth method. In addition, since the drift layer must have a very high electron mobility, the impurity or doping concentration must be substantially low. In addition, due to defects caused by differences in lattice constants due to growth on different substrates and the mixing of impurities during crystal growth, the doping concentration increases, which leads to a reduction in the efficiency and response speed of the detector. A method for manufacturing a GaN-based radiation detector is needed to solve these problems and have improved efficiency and improved response speed.

[0006] The issues described in the technical background of the present invention are written to increase understanding of the background of the present invention and may include contents that are not known prior arts in the field to which the technology belongs.

[0007] - Prior art document: U.S. Patent Publication No. US9,402,548 (2016.08.02) Summary of the invention

[0008] Technical issues

[0009] The problem to be solved by the present invention is to provide a GaN-based radiation detector capable of improving efficiency, increasing response speed and achieving a simple structure.

[0010] The technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and ordinary technicians in the technical field to which the present invention belongs can understand other technical problems not mentioned from the following description.

[0011] Technical Solution

[0012] A GaN-based radiation detector according to an embodiment of the present invention comprises: a GaN-based radiation detector having a 700 cm 2 / (V·s) or higher electron mobility, a thickness of 300 μm or higher, and a doping concentration of 3×10 16 / cm 3 An n-doped GaN layer having an n-type doping concentration of less than 10 μm; an n-doped GaN layer formed on one surface of the n-doped GaN layer, having a thickness of less than 3 μm and doped with 5×10 18 / cm 3 The above p-type doping concentration is used as a p-type p-doped GaN layer; a first metal contact is formed on the other surface of the n-doped GaN layer; and a second metal contact is formed on one surface of the p-doped GaN layer.

[0013] A GaN-based radiation detector according to another embodiment of the present invention includes: a 700 cm 2 / (V·s) or higher electron mobility, a thickness of 300 μm or higher, and a doping concentration of 3×10 16 / cm 3 An n-doped GaN layer having an n-type doping concentration of 1000 nm and a doping concentration of 5×10 18 / cm 3 a first p-doped GaN layer having a first p-doping concentration of at least 10; formed on one surface of the first p-doped GaN layer and doped with 5×10 19 / cm 3 a second p-doped GaN layer having a second doping concentration of at least one n-doped GaN layer; a first metal contact formed on another surface of the n-doped GaN layer; and a second metal contact formed on one surface of the second p-doped GaN layer.

[0014] A GaN-based radiation detector according to another embodiment of the present invention includes: a 700 cm 2 / (V·s) or higher electron mobility, a thickness of 300 μm or higher, and a doping concentration of 3×10 16 / cm3 An n-doped GaN layer having an n-type doping concentration of 5×10 18 / cm 3 Up to 5×10 20 / cm 3 A plurality of p-doped GaN layers having different p-doping concentrations and a thickness of less than 1 μm; a first metal contact formed on the other surface of the n-doped GaN layer; and a second metal contact formed on one surface of the plurality of p-doped GaN layers.

[0015] A portion of the p-doped GaN layer can be removed.

[0016] At least a portion of one surface of the n-doped GaN layer may have a rough structure.

[0017] The defect concentration of the n-doped GaN layer can be 5×10 6 / cm 2 the following.

[0018] A GaN-based radiation detector according to another embodiment of the present invention includes: a 700 cm 2 / (V·s) or higher electron mobility, a thickness of 300 μm or higher, and a doping concentration of 3×10 16 / cm 3 a first n-doped GaN layer having an n-type doping concentration of less than 5 μm and formed on one surface of the first n-doped GaN layer, having a thickness of less than 5 μm and doped with 5×10 17 / cm 3 a second n-doped GaN layer having an n-type doping concentration above 0.0407 W; a first metal contact formed on the other surface of the first n-doped GaN layer; and a second metal contact formed on one surface of the second n-doped GaN layer.

[0019] A portion of the second n-doped GaN layer can be removed.

[0020] At least a portion of a nitrogen surface of the n-doped GaN layer may be formed to have a roughness structure.

[0021] Effects of the Invention

[0022] According to the present invention, a GaN-based radiation detector with improved efficiency and response speed can be realized.

[0023] Furthermore, various effects that can be obtained or expected due to the embodiments of the present invention are directly or implicitly disclosed in the detailed description of the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following drawings are intended to help understand the present invention and provide embodiments of the present invention and a detailed description. However, the technical features of the present invention are not limited to specific drawings, and the features disclosed in each drawing can be combined with each other to form new embodiments. The embodiments of this specification can be better understood by referring to the following description in conjunction with the drawings, wherein similar reference numerals represent identical or functionally similar elements.

[0025] Figure 1 is a schematic cross-sectional view of a GaN-based radiation detector according to an embodiment of the present invention.

[0026] Figure 2 Shown according to Figure 1 An improved embodiment of a GaN-based radiation detector of an embodiment of the present invention.

[0027] Figure 3 Shown according to Figure 1 Another improved embodiment of the GaN-based radiation detector of the embodiment.

[0028] Figure 4 A schematic cross-sectional view of a GaN-based radiation detector according to another embodiment of the present invention is shown.

[0029] Figure 5 Shown according to Figure 4 An improved embodiment of a GaN-based radiation detector of an embodiment of the present invention.

[0030] Figure 6 Shown according to Figure 4 Another improved embodiment of the GaN-based radiation detector of the embodiment.

[0031] Figure 7 A schematic cross-sectional view of a GaN-based radiation detector according to another embodiment of the present invention is shown.

[0032] Figure 8 Shown according to Figure 7 An improved embodiment of a GaN-based radiation detector of an embodiment of the present invention.

[0033] Fig. 9 Shown according to Figure 7 Another improved embodiment of the GaN-based radiation detector of the embodiment.

[0034] Fig.10 Shown according to Figure 7 Another improved embodiment of the GaN-based radiation detector of the embodiment.

[0035] Fig.11 Shown according to Figure 7 Another improved embodiment of the GaN-based radiation detector of the embodiment.

[0036] It should be understood that the drawings cited above are not necessarily drawn to scale, but are intended to provide simplified representations of various features to illustrate the basic principles of the present invention. For example, the specific design features of the present invention, including specific dimensions, directions, locations and shapes, will be determined in part by specific intended applications and use environments. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various forms and is not limited to the described embodiments.

[0038] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprises" and / or "comprising" as used herein indicate the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, parts and / or their groups. As used herein, the term "and / or" includes any one or all combinations of one or more associated listed items. The term "coupled" represents a physical relationship between two components, wherein the components are directly connected to each other or indirectly connected through one or more intermediate components.

[0039] When describing components of the present invention, when a component is described as being “connected,” “coupled,” or “adjacent” to another component, it should be understood that the component may be directly connected, coupled, or adjacent to another component, but the other component may also be “connected,” “coupled,” or “adjacent” between each component.

[0040] Currently, the only technology that can stack GaN layers with a thickness of more than 100 μm is HVPE (Hydride Vapor Phase Epitaxy), but the use of HVPE technology is limited due to the disadvantages of high doping concentration and low electron mobility caused by impurity mixing during the growth process. In particular, although there is a method of reducing the concentration of n-type impurities by artificially mixing p-type impurities such as carbon (C) or iron (Fe) when growing a thick GaN drift layer using the HVPE method to prevent an increase in the concentration of n-type impurities due to the mixing of silicon (Si) or oxygen (O) impurities, this method causes a decrease in efficiency and response speed due to a decrease in electron mobility. Therefore, it is necessary to reduce the n-type doping concentration to 3×10 16 / cm 3 Below, to increase the electron mobility to 700 cm 2 / (V·s) or above.

[0041] Recently, research on techniques for reducing silicon and oxygen impurities in the HVPE growth method has been actively conducted. In particular, it has been reported that these impurities can be controlled by replacing the quartz tube of the reaction tube material of the HVPE apparatus with a different material or by changing the source gas used to grow GaN.

[0042] If the impurity reduction technology in GaN growth by HVPE is used to achieve a thickness of 300 μm or more and a thickness of 3×10 16 / cm 3 The following n-type doping concentration and 700Cm 2 / (V·s) or more of the electron mobility of the GaN substrate itself as a drift layer, a greater effect can be obtained. Increasing the thickness of the drift layer can promote radiation absorption and form more current, and can also increase the response speed through a higher driving voltage. In addition, it has the advantage of reducing leakage current through defect reduction, thereby reducing signal noise and improving reliability. In addition, since more electron and hole pairs can be generated in a thicker drift layer, the device structure can be simplified.

[0043] In particular, since a thick GaN substrate with low defects, low doping concentration, and high electron mobility can be used, the effects of a thick drift layer and defect reduction can be obtained accordingly, so that even if the (p)GaN or (n+) layer is removed, the device can be manufactured as a simpler device with improved characteristics, so a reduction in manufacturing costs can be expected. 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 the 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, thereby facilitating electron transport at the Schottky contact that occurs between the metal-semiconductor junction.

[0044] In the conventional method, a 5×10 17 / cm 3 However, if a GaN substrate with a low impurity concentration is used, it is sufficient to use only Schottky contacts when removing the (n+)GaN layer. 18 / cm 3 In other words, normal operation can be achieved with only one of the (n+)GaN layer and the (p+)GaN layer. This is due to the advantage of the Schottky contact, as it can be operated at a high voltage. In addition, a surface roughness structure can be inserted to help radiation absorption.

[0045] The GaN substrate used as a drift layer to manufacture GaN-based radiation detector devices reduces the silicon or oxygen impurities mixed during manufacturing, thereby reducing the n-type doping concentration and increasing the electron mobility. At this time, preferably, the GaN substrate has 3×10 16 / cm 3 The following n-type doping concentration, 700Cm 2 / (V·s) or more electron mobility and a thickness of more than 300μm. On the substrate prepared in this way, a layer of (p+)GaN or (n+)GaN is grown by MOCVD. A portion of the grown MOCVD epitaxial layer is etched and an electrode is formed. In addition, a portion of one side of the (n-)GaN layer can be etched by a wet etching method to produce a rough structure, thereby increasing the absorptivity of the incident radiation.

[0046] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0047] See also Figure 1The GaN-based radiation detector 10 includes an n-doped GaN layer 11 that is doped with an n-type, 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 formed by 16 / cm 3 The GaN layer is doped with an n-type doping concentration of 700 cm 2 / (V·s) or more and a thickness of 300 μm or more. In addition, the defect concentration of the n-doped GaN layer 11 can be 5×10 6 / cm 2 the following.

[0048] The 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. 18 / cm 3 The GaN layer is doped with a p-type doping concentration above and has a thickness of 3 μm or less.

[0049] Metal contacts 15 and 17 used as electrodes are respectively formed on the lower surface of the n-doped GaN layer 11 and the upper surface of the p-doped GaN layer 13. The metal contact 15 formed on the lower surface of the n-doped GaN layer 11 serves as a cathode, and the metal contact 17 formed on the upper surface of the p-doped GaN layer 13 serves as an anode. Although not shown in the drawings, an electrical signal generated by detection radiation (e.g., X-rays) can be generated by a circuit electrically connected to the cathode 15 and the anode 17.

[0050] The above-mentioned n-type doping 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.

[0051] Figure 2 and Figure 3 Shows Figure 1 An improved embodiment of a GaN-based radiation detector is provided. The same components are given the same reference numerals, and repeated descriptions are omitted. Figure 2 and Figure 3 , a portion of the p-doped GaN layer 13, such as the central portion thereof, may be removed. The partial removal of the p-doped GaN layer 13 may be accomplished by a process such as etching. In this regard, the anode 17 having a ring shape may be formed in the remaining portion after the partial removal, and the cathode 15 having a larger area may be formed to cover the entire area occupied by the anode 17.

[0052] Also, see Figure 3 , a roughness structure 19 may be formed on a portion of the n-doped GaN layer 1, for example, on at least a portion of the bottom surface. In this regard, the bottom surface of the n-doped GaN layer 11 may be a nitrogen surface where nitrogen atoms are mainly exposed. At this time, a cathode 15 may be formed on the roughness structure 19. The absorption of radiation to be detected (e.g., X-rays) may be increased by the roughness structure 19. For example, the roughness structure 19 may be formed by a process such as etching.

[0053] See also Figure 4 , in the Figure 1 In the embodiment of the present invention, a first p-doped GaN layer 21 and a second p-doped GaN layer 23 having different p-doping concentrations are sequentially formed on an n-doped GaN layer 11 of a GaN substrate having the same p-doping concentration. The first p-doped GaN layer 21 and the second p-doped GaN layer 23 can be formed by using a p-type doped GaN layer. The first p-doped GaN layer 21 is formed on the upper surface of the n-doped GaN layer 11 and can be formed at a thickness of 5×10 18 / cm 3 The first p-doping concentration is doped into a p-type, and the second p-doped GaN layer 23 is formed on the upper surface of the first p-doped GaN layer 21, and can be 5×10 19 / cm 3 The second doping concentration is doped to p-type, and the second doping concentration is greater than the first p-doping concentration.

[0054] Metal contacts 15 and 17 serving as electrodes may be formed on a lower surface of the n-doped GaN layer 11 and an upper surface of the second p-doped GaN layer 23 , respectively, thereby forming a cathode and an anode.

[0055] According to another embodiment of the present invention, the n-doped GaN layer 11 may include a layer having a thickness of less than 1 μm and doped with 5×10 18 / cm 3 Up to 5×10 20 / cm 3 At this time, the p-doped GaN layers can be doped to p-type with a p-doping concentration that is better as they rise. For example, when Figure 4 When two p-doped GaN layers are formed, the lower p-doped GaN layer is doped with a doping range of 5×10 18 / cm 3 Up to 5×10 20 / cm 3 The p-doping concentration of the upper p-doped GaN layer ranges from 5×10 19 / cm 3 Up to 5×10 20 / cm 3 The p-doping concentration of the GaN layer is higher than that of the lower p-doped GaN layer. In addition, in another embodiment, three or more p-doped GaN layers may be formed in sequence.

[0056] Figure 5 and Figure 6 Shows Figure 4 An improved embodiment of a GaN-based radiation detector is disclosed. The same reference numerals are used for the same components, and repeated descriptions are omitted. Figure 5 and Figure 6 , a portion of the p-doped GaN layers 21 and 23, such as the central portion thereof, may be removed. The partial removal of the p-doped GaN layers 21 and 23 may be accomplished by a process such as etching. In this regard, the anode 17 having a ring shape may be formed in the remaining portion after the partial removal, and the cathode 15 having a larger area may be formed to cover the entire area occupied by the anode 17.

[0057] Also, see Figure 6 , the roughness structure 19 may be formed on a portion of the n-doped GaN layer 11 , for example, on at least a portion of a bottom surface thereof.

[0058] Figure 7 A GaN-based radiation detector according to another embodiment of the present invention is shown. Figure 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 bottom surface of the n-doped GaN layer 11 .

[0059] As described above, the n-doped GaN layer 11 is doped with 3×10 16 / cm 3 Below n-type doping concentration, with 700cm 2 / (V·s) or more, and has 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 doped with 5×10 17 / cm 3 Above n-type doping concentration.

[0060] Metal contacts 15 and 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, so that a cathode and an anode can be formed.

[0061] Figure 8 and 9 Shows Figure 7An improved embodiment of a GaN-based radiation detector is disclosed. The same reference numerals are used for the same components, and repeated descriptions are omitted. Figure 8 and 9 , a portion of the n-doped GaN layer 31, for example, a central portion thereof, may be removed. The removal of the portion of the n-doped GaN layer 31 may be performed by a process such as etching. At this time, a cathode 15 having a ring shape may be formed in the remaining portion after the partial removal, and an anode 17 having a larger area may be formed to cover the entire area occupied by the cathode 15.

[0062] Also, see Fig. 9 , the roughness structure 19 may be formed on a portion of the n-doped GaN layer 31, for example, on at least a portion of the bottom surface exposed by removing a portion of the n-doped GaN layer 11. Here, the bottom surface of the n-doped GaN layer 11 may be a nitrogen surface where nitrogen atoms are mainly exposed.

[0063] Fig.10 and Fig.11 Shows Figure 7 Another improved embodiment of a GaN-based radiation detector. 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 .

[0064] Also, see Fig.11 , a portion of the n-doped GaN layer 31, such as the central portion thereof, may be removed, and the cathode 15 having a ring shape may be formed. A roughness structure 19 may be formed on the upper surface of the n-doped GaN layer 11, which is a GaN substrate, and an anode 17 may be formed on the roughness structure 19.

[0065] 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 appended claims also fall within the scope of the present invention.

Claims

1. A GaN-based radiation detector comprising: With 700cm 2 / (V·s) or higher electron mobility, having a thickness of 300 μm or higher and doped with 3×10 16 / cm 3 An n-doped GaN layer having an n-type doping concentration of: formed on one surface of the n-doped GaN layer, having a thickness of 3 μm or less and doped with 5×10 18 / cm 3 The above p-type doping concentration serves as a p-type p-doped GaN layer; a first metal contact formed on another surface of the n-doped GaN layer; as well as A second metal contact is formed on a surface of the p-doped GaN layer.

2. A GaN-based radiation detector comprising: With 700cm 2 / (V·s) or higher electron mobility, having a thickness of 300 μm or higher and doped with 3×10 16 / cm 3 An n-doped GaN layer having an n-type doping concentration of: formed on one surface of the n-doped GaN layer and doped with 5×10 18 / cm 3 a first p-doped GaN layer having a first p-doping concentration; formed on one surface of the first p-doped GaN layer and doped with 5×10 19 / cm 3 a second p-doped GaN layer having a second doping concentration above the above; a first metal contact formed on another surface of the n-doped GaN layer; as well as A second metal contact is formed on a surface of the second p-doped GaN layer.

3. A GaN-based radiation detector comprising: With 700cm 2 / (V·s) or higher electron mobility, a thickness of 300 μm or higher, and a doping concentration of 3×10 16 / cm 3 An n-doped GaN layer having an n-type doping concentration of: formed on one surface of the n-doped GaN layer, sequentially doped with 5×10 18 / cm 3 Up to 5×10 20 / cm 3 a plurality of p-doped GaN layers having different p-doping concentrations and a thickness of less than 1 μm; a first metal contact formed on another surface of the n-doped GaN layer; as well as A second metal contact is formed on one surface of the plurality of p-doped GaN layers.

4. The GaN-based radiation detector according to any one of claims 1 to 3, wherein: A portion of the p-doped GaN layer can be removed.

5. The GaN-based radiation detector according to any one of claims 1 to 3, wherein: At least a portion of one surface of the n-doped GaN layer has a rough structure.

6. The GaN-based radiation detector according to any one of claims 1 to 3, wherein: The defect concentration of the n-doped GaN layer is 5×10 6 / cm 2 the following.

7. A GaN-based radiation detector comprising: With 700cm 2 / (V·s) or higher electron mobility, a thickness of 300 μm or higher, and a doping concentration of 3×10 16 / cm 3 A first n-doped GaN layer having an n-type doping concentration of: formed on one surface of the first n-doped GaN layer, having a thickness of 5 μm or less and doped with 5×10 17 / cm 3 a second n-doped GaN layer having an n-type doping concentration of at least 1:1; forming a first metal contact on another surface of the first n-doped GaN layer; as well as A second metal contact is formed on a surface of the second n-doped GaN layer.

8. The GaN-based radiation detector of claim 7, wherein: A portion of the second n-doped GaN layer can be removed.

9. The GaN-based radiation detector according to any one of claims 1 to 3 and 7, wherein: At least a portion of a nitrogen surface of the n-doped GaN layer is formed to have a roughness structure.

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