Gallium nitride-based radiation detectors

Abstract

The present invention relates to a GaN-based radiation detector capable of detecting radiation such as X-rays. 2 / (V·s) or more and a thickness of 300 μm or more, and 16 / cm 3 and an n-doped GaN layer doped at a doping concentration of 5×10 .mu.m or less, formed on one side of the n-doped GaN layer and having a thickness of 3 .mu.m or less, and 18 / cm 3 a p-doped GaN layer doped at a doping concentration of at least 1000 nm, 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.

Description

[Technical Field]

[0001] The present invention relates to a GaN-based radiation detector capable of detecting radiation such as X-rays. [Background technology]

[0002] Recently, most direct-transfer type radiation detectors are manufactured using α-Se (amorphous selenium) or CdTe (cadmium telluride). As is well known, α-Se is extremely expensive to manufacture, and cadmium is a heavy metal that is highly harmful to the human body. Therefore, there is an urgent need to develop direct-transfer type semiconductor radiation detectors to address these issues.

[0003] Materials such as GaAs (gallium arsenide), SiC (silicon carbide), Ga2O3 (gallium oxide), and GaN (gallium nitride) are considered suitable for direct conversion radiation detectors. However, considering radiation resistance, efficiency as a direct conversion semiconductor, and ease of manufacturing, GaN is said to be the best alternative.

[0004] Recently, numerous studies in the field of GaN-based radiation detectors have demonstrated their advantages as radiation detectors, particularly their ability to appropriately detect ultraviolet light, neutrons, and X-rays.

[0005] Existing GaN-based radiation detectors are mostly formed by epitaxial growth on sapphire (Al2O3) or silicon carbide (SiC) substrates by processes such as MOCVD (metal organic chemical vapor deposition). Therefore, the growth thickness is as thin as 30 μm or less, and the drift layer, which is the generation region of electrons and holes due to the incident radiation, is thin. Since such a thin drift layer must be utilized, it has the disadvantages of efficiency reduction and structural complexity. This is due to the limitations in the growth method. In the case of the drift layer, the electron mobility must be very high, so basically the impurity or doping concentration must be low. In addition, due to the defects caused by the difference in lattice constants due to growth on different substrates and the influence of impurity incorporation during crystal growth, the doping concentration increases, inducing a decrease in the efficiency and response speed of the detector. There is a need for a method that can solve such problems and manufacture a GaN-based radiation detector with improved efficiency and response speed.

[0006] The matters described in the technical background part of the present invention are created to enhance the understanding of the background of the invention and can include matters that are not well-known prior art in the field to which the technology belongs.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[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 realizing a simple structure.

[0009] The technical problem to be achieved by the present invention is not limited to the technical problems mentioned above, and other technical problems not mentioned will be understood by those with ordinary knowledge in the technical field to which the present invention belongs from the following description.

Means for Solving the Problem

[0010] The GaN-based radiation detector according to an embodiment of the present invention has an electron mobility of 700 cm 18 ,

[0012] , , , 3 , 3 , 19 / (V·s) or more and a thickness of 300 μm or more, and is an n-type GaN layer doped with a doping concentration of 3×10 16 / cm 3 or less, a p-doped GaN layer formed on one surface of the n-doped GaN layer, having a thickness of 3 μm or less, and being p-type and doped with a doping concentration of 5×10 18 / cm 3 or more, 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.

[0011] The GaN-based radiation detector according to another embodiment of the present invention has an electron mobility of 700 cm 2 / (V·s) or more and a thickness of 300 μm or more, and is an n-type GaN layer doped with a doping concentration of 3×10 16 / cm 3 or less, a first p-doped GaN layer formed on one surface of the n-doped GaN layer, being p-type and doped with a first p-doping concentration of 5×10 18 / cm 3 or more, a second p-doped GaN layer formed on one surface of the first p-doped GaN layer, being p-type and doped with a second doping concentration of 5×10 19 / cm 3 or more, 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 second p-doped GaN layer.

[0012] Another embodiment of the present invention provides a GaN-based radiation detector with a 700 cm² radiation level. 2 It has an electron mobility of ≥ / (V·s) and a thickness of ≥300 μm, and is n-type with a 3x10 16 / cm 3 An n-doped GaN layer doped with the following doping concentrations, and a p-type GaN layer formed on one surface of the n-doped GaN layer, with a 5x10x width. 18 / cm 3 ~5x10 20 / cm 3 The invention comprises a plurality of p-doped GaN layers having a thickness of 1 μm or less, which are continuously doped with different p-doping concentrations belonging to a range; 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 plurality of p-doped GaN layers.

[0013] The structure may allow for the removal of a portion of the p-doped GaN layer.

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

[0015] The defect concentration of the n-doped GaN layer is 5 x 10 6 / cm 2 The following is also acceptable.

[0016] Another embodiment of the present invention provides a GaN-based radiation detector with a 700 cm² radiation level. 2 It has an electron mobility of ≥ / (V·s) and a thickness of ≥300 μm, and is n-type with a 3x10 16 / cm 3 A first n-doped GaN layer doped with the following doping concentrations, and a 5x10 n-type GaN layer formed on one surface of the first n-doped GaN layer, having a thickness of 5 μm or less. 17 / cm 3The material comprises a secondn-doped GaN layer doped with the above doping concentration, a first metal junction formed on the other side of the firstn-doped GaN layer, and a second metal junction formed on one side of the secondn-doped GaN layer.

[0017] The structure may allow a portion of the 2n-doped GaN layer to be removed.

[0018] At least a portion of the nitrogen surface of the n-doped GaN layer may be formed to have an uneven structure. [Effects of the Invention]

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

[0020] In addition, various other effects that can be obtained or anticipated by embodiments of the present invention are disclosed directly or implicitly in the detailed description of embodiments of the present invention. [Brief explanation of the drawing]

[0021] The following drawings are provided to aid in understanding the present invention and, together with a detailed description, provide embodiments relating to the present invention. However, the technical features of the present invention are not limited to specific drawings, and the features disclosed in each drawing may be combined with each other to form new embodiments. Embodiments in this specification may be better understood by referring to the following description in relation to the attached drawings, where similar reference numerals refer to the same or functionally similar elements. [Figure 1] A schematic cross-sectional view of a GaN-based radiation detector according to an embodiment of the present invention is shown. [Figure 2] A modified example of the GaN-based radiation detector according to the embodiment of Figure 1 is shown. [Figure 3] Other modified examples of GaN-based radiation detectors according to the embodiment of Figure 1 are shown. [Figure 4]A schematic cross-sectional view of a GaN-based radiation detector according to another embodiment of the present invention is shown. [Figure 5] A modified example of the GaN-based radiation detector according to the embodiment shown in Figure 4 is presented. [Figure 6] Figure 4 shows another modified example of a GaN-based radiation detector according to the embodiment. [Figure 7] A schematic cross-sectional view of a GaN-based radiation detector according to another embodiment of the present invention is shown. [Figure 8] A modified example of the GaN-based radiation detector according to the embodiment shown in Figure 7 is presented. [Figure 9] Figure 7 shows another modified example of a GaN-based radiation detector according to the embodiment. [Figure 10] Figure 7 shows another modified example of a GaN-based radiation detector according to the embodiment. [Figure 11] Figure 7 shows another modified example of a GaN-based radiation detector according to the embodiment.

[0022] The drawings referenced above should be understood not as illustrations corresponding to the accumulation, but rather as simplified representations of various features illustrating the basic 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 specific intended applications and usage environments. [Modes for carrying out the invention]

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be embodied in a variety of different forms and is not limited to the embodiments described.

[0024] The terms used herein are for the purpose of describing specific embodiments and are not intended to limit the invention. As used herein, a singular form is intended to include multiple forms unless the context clearly indicates otherwise. As used herein, the terms “includes” and / or “contains” indicate the presence of an explicitly stated feature, integer, stage, actuation, element and / or component, but should be understood not to exclude the presence or addition of one or more other features, integers, stages, actuation, components and / or groups thereof. As used herein, the terms “and / or” include any one or all of the one or more items enumerated in relation. The term “combined” indicates a physical relationship between two components that are directly linked to each other or indirectly linked through one or more intermediary components.

[0025] When describing the components of the present invention, if it is stated that one component is “linked,” “joined,” or “connected” to another component, it should be understood that the component may be directly linked, joined, or connected to the other component, but other components may also be “linked,” “joined,” or “connected” between each component.

[0026] Currently, HVPE (hydride vapor phase epitaxy) is virtually the only technology capable of stacking GaN layers to a thickness of 100 μm or more. However, HVPE technology has been limited in its use due to the disadvantage that impurities can be introduced during growth, leading to increased doping concentration and reduced electron mobility. In particular, when growing thick GaN drift layers using the HVPE method, there is a method to reduce the concentration of n-type impurities by artificially introducing p-type impurities such as carbon (C) or iron (Fe) to prevent an increase in n-type impurity concentration due to the introduction of silicon (Si) or oxygen (O) impurities. However, in this case, a decrease in electron mobility leads to a decrease in efficiency and response speed. Therefore, basically, when growing GaN using the HVPE method, the n-type doping concentration through a technology that minimizes silicon or oxygen impurities is 3 x 10⁻¹⁶. 16 / cm 3 Only when reduced to below 700 cm can the electron mobility also be reduced to 700 cm. 2 It can be improved to (V·s) or better.

[0027] Recently, there has been active research on techniques for reducing silicon and oxygen impurities in HVPE growth methods. In particular, it has been reported that these impurities can be controlled by replacing the quartz tube, which is the reaction tube material of the HVPE apparatus, with another material, or by changing the source gas used to grow GaN.

[0028] Through impurity reduction techniques in GaN growth using HVPE, the n-type doping concentration is reduced to 3 x 10⁻¹⁰. 16 / cm 3 The following is true, and the electron mobility is 700 cm. 2By utilizing the GaN substrate itself, with a thickness of 300 μm or more and a value of / (V·s) or higher, as the drift layer, greater effects can be obtained. Increasing the thickness of the drift layer promotes radiation absorption, which not only allows for the formation of a larger current but also improves the response speed with a higher drive voltage. Furthermore, it has the advantage of reducing leakage current and signal noise by reducing defects, thereby increasing reliability. In addition, since a thicker drift layer can generate more electron and hole pairs, it is also possible to simplify the device structure.

[0029] In particular, when using thick GaN substrates with low defects, low doping concentrations, and high electron mobility, a naturally thicker drift layer and defect reduction effect can be obtained. Therefore, even if one of the (p)GaN or (n+) layers is removed, the device can be manufactured as a simpler element with improved properties, and thus a reduction in manufacturing cost can be expected. In particular, GaN-based radiation detectors manufactured with such a structure have a higher breakdown voltage than existing detectors. Since the breakdown voltage of an element is determined by the doping concentration, defects, and thickness of the drift layer, elements with a higher breakdown voltage can be driven at higher voltages, and electron transfer at the Schottky junction between the metal-semiconductor junction is easier.

[0030] Existing methods involve placing 5x10 on a sapphire or silicon carbide substrate. 17 / cm 3 As mentioned above, the doped (n+)GaN layer must always be used, but when using GaN substrates with low impurity concentrations, it is sufficient to remove the (n+)GaN layer and utilize only the Schottky contact. 18 / cm 3The doped (p+)GaN layer may also be removed. In other words, normal operation is possible even with only one of the (n+)GaN layer or (p+)GaN layer present. This is due to the advantage of being able to operate at high voltages, which allows for Schottky junctions. Furthermore, it is possible to insert surface irregularities to aid in radiation absorption.

[0031] To manufacture elements for GaN-based radiation detectors, the GaN substrate used as a drift layer reduces the amount of silicon or oxygen impurities introduced during manufacturing, thereby lowering the n-type doping concentration and increasing electron mobility. At this time, the GaN substrate is 3 x 10 16 / cm 3 The following are the n-type doping concentrations, 700 cm³. 2 It is preferable to have an electron mobility of 1 / (V·s) or higher and a thickness of 300 μm or higher. On the substrate prepared in this way, one layer of (p+)GaN or (n+)GaN is grown by MOCVD. A portion of the grown MOCVD epitaxial layer is etched to form electrodes. Alternatively, the absorption rate of incident radiation can be increased by forming a rough structure on a portion of one surface of the (n-)GaN layer using an etching method such as wet etching.

[0032] Embodiments of the present invention will be described below with reference to the drawings.

[0033] Referring to Figure 1, the GaN-based radiation detector 10 includes an n-doped GaN layer 11, which is doped with n-type GaN, and the n-doped GaN layer 11 corresponds to the GaN substrate used as a drift layer. To improve response speed and reliability, the n-doped GaN layer 11 is made of n-type GaN with a 3x10 ratio. 16 / cm 3 Formed by doping with the following concentrations, 700 cm 2 It has an electron mobility of ≥ / (V·s) and a thickness of ≥300 μm. Furthermore, the defect concentration of the n-doped GaN layer 11 is 5 × 10⁻¹⁰ 6 / cm 2 The following is also acceptable.

[0034] A p-doped GaN layer 13 is formed on the upper surface of an n-doped GaN layer 11, and for example, the p-doped GaN layer 13 may be formed by a method such as MOCVD. The p-doped GaN layer 13 is formed when the GaN layer is p-type and 5x10 18 / cm 3 Formed by doping with the above doping concentrations, and having a thickness of 3 μm or less.

[0035] Metal junctions 15 and 17, which act as electrodes, are formed on the bottom surface of the n-doped GaN layer 11 and on the top surface of the p-doped GaN layer 13, respectively. The metal junction 15 formed on the bottom surface of the n-doped GaN layer 11 acts as a cathode, and the metal junction 17 formed on the top surface of the p-doped GaN layer 13 acts as an anode. Although not shown in the drawings, an electrical circuit electrically connected to the cathode 15 and anode 17 can generate an electrical signal generated by sensing radiation, such as X-rays.

[0036] The aforementioned n-type doping can be performed using silicon (Si) as a dopant, and silane (SiH4) can be used as the dopant source. Similarly, p-type doping can be performed using magnesium (Mg) as a dopant, and biscyclopentadienyl-magnesium can be used as the dopant source.

[0037] Figures 2 and 3 show modified examples of the GaN-based radiation detector of Figure 1. The same parts are denoted by the same reference numerals, and redundant explanations are omitted. Referring to Figures 2 and 3, a portion of the p-doped GaN layer 13, for example, the central portion, may be removed. The removal of a portion of the p-doped GaN layer 13 can be carried out by a process such as etching. In this case, the anode 17 may be formed to have a ring shape in the portion remaining after the removal, and the cathode 15 may be formed to cover a larger area so as to cover the entire region occupied by the anode 17.

[0038] On the other hand, referring to Figure 3, a textured 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 the nitrogen surface, where nitrogen atoms are more exposed. In this case, the cathode 15 may be formed on the textured structure 19. The textured structure 19 can enhance the absorption of the radiation to be detected, such as X-rays. For example, the textured structure 19 may be formed by a process such as etching.

[0039] Referring to Figure 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 in the embodiment of Figure 1, with different p-doping concentrations. The first and second p-doped GaN layers 21 and 23 may be formed by doping the GaN layers in the p-type. The first p-doped GaN layer 21 is formed on the upper surface of the n-doped GaN layer 11 and is p-type with a width of 5x10 18 / cm 3 The GaN layer 23, doped with the above 1st p-doping concentration and 2nd p-doped, is formed on the upper surface of the GaN layer 21 that is p-type and has a higher doping concentration of 5x10 than the 1st p-doping concentration. 19 / cm 3 Doping may be performed at the above second doping concentration.

[0040] Metal junctions 15 and 17, which act as electrodes, are formed on the bottom surface of the n-doped GaN layer 11 and on the top surface of the second p-doped GaN layer 23, respectively, thereby forming a cathode and an anode.

[0041] According to another embodiment of the present invention, a 5x10 p-type layer is laid on the aforementioned n-doped GaN layer 11. 18 / cm 3 ~5x10 20 / cm 3 It may include multiple p-doped GaN layers having a thickness of 1 μm or less, which are successively doped with different p-doping concentrations belonging to a range. In this case, the p-doped GaN layers can be doped with p-type at better p-doping concentrations as you move upwards. For example, as shown in Figure 4, when two p-doped GaN layers are formed, the lower p-doped GaN layer is 5 x 10⁻¹⁶ 18 / cm 3 ~5x10 20 / cm 3 The GaN layer above is doped with a p-doping concentration that falls within the range, and the upper p-doped GaN layer has a higher concentration of 5x10. 19 / cm 3 ~5x10 20 / cm 3 The GaN is doped with a p-doping concentration that falls within a specified range. In other embodiments, three or more p-doped GaN layers may be formed sequentially.

[0042] Figures 5 and 6 show modified examples of the GaN-based radiation detector of Figure 4. The same parts are denoted by the same reference numerals, and redundant explanations are omitted. Referring to Figures 5 and 6, a portion of the p-doped GaN layers 21 and 23, for example, the central portion, may be removed. The removal of a portion of the p-doped GaN layers 21 and 23 can be carried out by a process such as etching. In this case, 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 cover a larger area so as to cover the entire region occupied by the anode 17.

[0043] On the other hand, referring to Figure 6, a rough structure 19 may be formed on a part of the n-doped GaN layer 11, for example, at least a part of the bottom surface.

[0044] Figure 7 shows a GaN-based radiation detector according to the present invention and other embodiments. Referring to 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.

[0045] As mentioned above, the n-doped GaN layer 11 is n-type with a density of 3 x 10⁶. 16 / cm 3 The following doping concentrations were used, and 700cm 2 It has an electron mobility of ≥ / (V·s) and a thickness of ≥300 μm. The additionally formed n-doped GaN layer 31 has a thickness of ≤5 μm and is n-type with a width of 5x10 17 / cm 3 The doping will be performed at the above concentrations.

[0046] Metal junctions 15 and 17 are formed on the bottom surface of the n-doped GaN layer 31 and the top surface of the n-doped GaN layer 11, respectively, thereby forming a cathode and an anode.

[0047] Figures 8 and 9 show modified examples of the GaN-based radiation detector of Figure 7. The same parts are denoted by the same reference numerals, and redundant explanations are omitted. Referring to Figures 8 and 9, a portion of the n-doped GaN layer 31, for example, the central portion, may be removed. The removal of a portion of the n-doped GaN layer 31 can be carried out by a process such as etching. In this case, 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 cover a larger area so as to cover the entire region occupied by the cathode 15.

[0048] On the other hand, referring to Figure 9, a rough structure 19 may be formed on at least a portion of the bottom surface exposed by removing a part of the n-doped GaN layer 11, for example, a part of the n-doped GaN layer 31. Here, the bottom surface of the n-doped GaN layer 11 may be a nitrogen surface with a large amount of exposed nitrogen atoms.

[0049] Figures 10 and 11 show other modified examples of the GaN-based radiation detector of Figure 7. Referring to Figure 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 total area occupied by the anode 17.

[0050] On the other hand, referring to Figure 11, a portion 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 textured 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 textured structure 19.

[0051] While embodiments of the present invention have been described above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art, utilizing the basic concepts of the present invention as defined in the claims, also fall within the scope of the present invention.

Claims

1. 700 cm ２ It has an electron mobility of 1 / (V·s) or higher and a thickness of 300 μm or higher, and is n-type with 3 x 10 １６ / cm ３ n-doped GaN layers doped with the following doping concentrations, Formed on one surface of the n-doped GaN layer, having a thickness of 3 μm or less, and p-type with 5 x 10 １８ / cm ３ A p-doped GaN layer doped with the above doping concentrations, A first metal joint formed on the other side of the n-doped GaN layer, A GaN-based radiation detector comprising a second metal junction formed on one surface of the p-doped GaN layer.

2. 700 cm ２ It has an electron mobility of 1 / (V·s) or higher and a thickness of 300 μm or higher, and is n-type with 3 x 10 １６ / cm ３ n-doped GaN layers doped with the following doping concentrations, Formed on one surface of the n-doped GaN layer, the first p-doped GaN layer doped with a p-type first p-doping concentration of 5x10 １８ / cm ３ or higher, and Formed on one surface of the first p-doped GaN layer, it is p-type and has a higher concentration of 5 x 10 than the first p-doping concentration. １９ / cm ３ The GaN layer doped with the above second doping concentration and the second p doped layer, A first metal joint formed on the other side of the n-doped GaN layer, 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 It has an electron mobility of 1 / (V·s) or higher and a thickness of 300 μm or higher, and is n-type with 3 x 10 １６ / cm ３ n-doped GaN layers doped with the following doping concentrations, Formed on one surface of the aforementioned n-doped GaN layer, it is p-type and 5 x 10 １８ / cm ３ ~5x10 ２０ / cm ３ Multiple p-doped GaN layers having a thickness of 1 μm or less, continuously doped with different p-doping concentrations belonging to a range, A first metal joint formed on the other side of the n-doped GaN layer, A GaN-based radiation detector comprising a second metal junction 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 an uneven structure.

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

7. 700 cm ２ It has an electron mobility of 1 / (V·s) or higher and a thickness of 300 μm or higher, and is n-type with 3 x 10 １６ / cm ３ A first n-doped GaN layer doped with the following doping concentrations, Formed on one surface of the first n-doped GaN layer, having a thickness of 5 μm or less, and in n-type, 5 x 10 １７ / cm ３ The 2n-doped GaN layer, doped with the above doping concentrations, A first metallic junction formed on the other surface of the first n-doped GaN layer, A GaN-based radiation detector comprising a second metal junction formed on one surface of the second n-doped GaN layer.

8. The GaN-based radiation detector according to claim 7, wherein a portion of the secondn-doped GaN layer can be removed.

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

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