Gallium nitride radiation detector

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 conversion type radiation detectors are made of α-Se (amorphous selenium) or CdTe (cadmium telluride) materials, but as is well known, α-Se is very expensive to manufacture and cadmium is a heavy metal that is very harmful to the human body. To solve these problems, there is an urgent need to develop a direct conversion type semiconductor radiation detector.

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

[0004] Recently, in the research field of GaN-based radiation detectors, many results have been reported that have demonstrated their advantages as radiation detectors, particularly their ability to properly detect ultraviolet rays, neutrons, X-rays, etc.

[0005] Most existing GaN-based radiation detectors are formed epitaxially on sapphire (Al2O3) or silicon carbide (SiC) substrates using processes such as MOCVD (metal organic chemical vapor deposition). However, the resulting thin drift layer, which generates electrons and holes due to incident radiation, is thin (less than 30 μm). This thin drift layer results in reduced efficiency and a complex structure. This is due to limitations in the growth method, and the drift layer must have very high electron mobility, so it generally requires a low impurity or doping concentration. Furthermore, defects caused by differences in lattice constants during growth on a heterogeneous substrate and the incorporation of impurities during crystal growth increase the doping concentration, resulting in reduced detector efficiency and response speed. A method is needed to address these issues and fabricate GaN-based radiation detectors with improved efficiency and response speed.

[0006] The matters described in the technical background section of the present invention are prepared to enhance understanding of the background of the invention, and may include matters that are not well-known prior art in the field to which the technology pertains. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 9,402,548 Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a GaN-based radiation detector that can achieve improved efficiency, improved response speed, and a simple structure.

[0009] The technical problems that the present invention aims to achieve are not limited to the technical problems mentioned above, and other technical problems not mentioned will be understood by those skilled in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0010] The GaN-based radiation detector according to the embodiment of the present invention has a 700 cm 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.

[0011] The GaN-based radiation detector according to another embodiment of the present invention has a wavelength of 700 cm 2 / (V·s) or more and a thickness of 300 μm or more, and 16 / cm 3 and a p-type GaN layer doped with an n-doped GaN layer having a doping concentration of 5x10 18 / cm 3 a first p-doped GaN layer doped at the first p-doping concentration of 5×10 19 / cm 3 The semiconductor device includes a second p-doped GaN layer doped at the second doping concentration, 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] A GaN-based radiation detector according to still another embodiment of the present invention has a wavelength of 700 cm 2 / (V·s) or more and a thickness of 300 μm or more, and 16 / cm 3 and a p-type GaN layer doped with an n-doped GaN layer having a doping concentration of 5x10 18 / cm 3 ~5x10 20 / cm 3 The semiconductor device includes a plurality of p-doped GaN layers having a thickness of 1 μm or less, successively doped with different p-doping concentrations within a range; a first metal junction formed on another 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] A part of the p-doped GaN layer may be removed.

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

[0015] The defect concentration in the n-doped GaN layer is 5x10 6 / cm 2 It may be the following:

[0016] A GaN-based radiation detector according to still another embodiment of the present invention has a wavelength of 700 cm 2 / (V·s) or more and a thickness of 300 μm or more, and 16 / cm 3 a first n-doped GaN layer doped at a doping concentration of 5 μm or less, and a second n-type GaN layer having a thickness of 5 μm or less and a doping concentration of 5×10 17 / cm 3a 2n-doped GaN layer doped at a doping concentration equal to or greater than 1000 nm, a first metal junction formed on another surface of the 1n-doped GaN layer, and a second metal junction formed on one surface of the 2n-doped GaN layer.

[0017] A portion of the second n-doped GaN layer may be removable.

[0018] At least a portion of the nitrogen face 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 having improved efficiency and response speed can be realized.

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

[0021] The accompanying drawings are provided to aid in understanding the present invention and, together with the detailed description, provide embodiments of the present invention. However, the technical features of the present invention are not limited to the specific drawings, and the features disclosed in each drawing may be combined with each other to form a new embodiment. The embodiments of the present specification can be better understood by referring to the following description in conjunction with the accompanying drawings, in which like reference numerals refer to identical or functionally similar elements. [Figure 1] 1 shows a schematic cross-sectional view of a GaN-based radiation detector according to an embodiment of the present invention. [Figure 2] 2 shows a modified example of the GaN-based radiation detector according to the embodiment of FIG. 1. [Figure 3] 1. FIG. 3 shows another modified example of the GaN-based radiation detector according to the embodiment of FIG. [Figure 4]FIG. 2 shows a schematic cross-sectional view of a GaN-based radiation detector according to another embodiment of the present invention. [Figure 5] 5 shows a modified example of the GaN-based radiation detector according to the embodiment of FIG. [Figure 6] 5 shows another modified example of the GaN-based radiation detector according to the embodiment of FIG. [Figure 7] FIG. 10 shows a schematic cross-sectional view of a GaN-based radiation detector according to still another embodiment of the present invention. [Figure 8] 8 shows a modified example of the GaN-based radiation detector according to the embodiment of FIG. 7. [Figure 9] 8 shows another modified example of the GaN-based radiation detector according to the embodiment of FIG. 7. [Figure 10] 8 shows another modified example of the GaN-based radiation detector according to the embodiment of FIG. 7. [Figure 11] 8 shows another modified example of the GaN-based radiation detector according to the embodiment of FIG. 7.

[0022] The above-referenced drawings should be understood as not necessarily drawn to scale, but as presenting simplified representations of various features illustrating the basic principles of the invention. The specific design features of the invention, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and environment of use. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand the present invention. However, the present invention may be embodied in various different forms and is not limited to the described embodiments.

[0024] 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 form 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 the stated features, integers, steps, operations, elements, and / or components, but do not exclude 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" denotes a physical relationship between two components, either directly connected to each other or indirectly connected through one or more intermediary components.

[0025] In describing components of the present invention, when a component is described as being "coupled," "coupled," or "connected" to other components, it should be understood that the components may be directly coupled, coupled, or connected to the other components, but that there may also be other components "coupled," "coupled," or "connected" between each component.

[0026] Currently, hydride vapor phase epitaxy (HVPE) is the only technology capable of depositing GaN layers thicker than 100 μm. However, HVPE has been limited in its application due to the drawback of high doping concentrations due to the incorporation of impurities during growth, resulting in reduced electron mobility. In particular, to prevent an increase in n-type impurity concentration due to the incorporation of silicon (Si) or oxygen (O) impurities when growing a thick GaN drift layer using the HVPE method, one approach is to lower the n-type impurity concentration by artificially incorporating p-type impurities such as carbon (C) or iron (Fe). However, this reduces electron mobility, resulting in reduced efficiency and response speed. Therefore, the standard practice for GaN growth using the HVPE method is to minimize silicon or oxygen impurities to achieve an n-type doping concentration of 3x10. 16 / cm 3 Only when the electron mobility is reduced to below 700 cm 2 / (V·s) or more.

[0027] Recently, active research has been conducted into technologies for reducing silicon and oxygen impurities in the HVPE growth method. 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 equipment, with other materials or by changing the source gas used to grow GaN.

[0028] Through the impurity reduction technique in GaN growth by HVPE, the n-type doping concentration is 3x10 16 / cm 3 and electron mobility is 700 cm 2Greater effects can be achieved by using a GaN substrate with a thickness of 300 μm or more as the drift layer, which has a V / (V·s) or higher. Increasing the drift layer thickness not only promotes radiation absorption and allows for the generation of larger currents, but also improves response speed through higher drive voltages. Another advantage is that fewer defects reduce leakage current, which reduces signal noise and increases reliability. Furthermore, a thicker drift layer can generate more electron-hole pairs, allowing for a simplification of the device structure.

[0029] In particular, the use of a thick GaN substrate with low defects, low doping concentration, and high electron mobility naturally results in a thick drift layer and reduced defects. Therefore, even if either the (p)GaN or (n+) layer is removed, the device can be manufactured as a simpler device while still improving its characteristics, which is expected to reduce manufacturing costs. In particular, GaN-based radiation detectors manufactured with this structure have a higher breakdown voltage than existing detectors. Since the breakdown voltage of a device is determined by the doping concentration, defects, and thickness of the drift layer, devices with higher breakdown voltages can be operated at higher voltages and electrons can move more easily at the Schottky junction, which occurs between metal-semiconductor junctions.

[0030] Existing methods can produce 5x10 17 / cm 3 Although it is necessary to use a 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. 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 and the (p+) GaN layer. This is due to the advantage of being able to operate at high voltage and having a Schottky junction. It is also possible to insert a surface roughness structure to help absorb radiation.

[0031] To manufacture elements for GaN-based radiation detectors, the GaN substrate used as the drift layer is designed to reduce the n-type doping concentration by reducing the silicon or oxygen impurities introduced during manufacturing, thereby increasing the electron mobility. 16 / cm 3 n-type doping concentration below 700cm 2 It is preferable that the substrate has an electron mobility of 1 / (V·s) or higher and a thickness of 300 μm or more. A layer of either (p+) GaN or (n+) GaN is grown on the substrate prepared in this way by MOCVD. A portion of the grown MOCVD epitaxial layer is etched to form an electrode. It is also possible to increase the absorption rate of incident radiation by forming a roughened structure on part of one surface of the (n-) GaN layer using an etching method such as wet etching.

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0033] Referring to FIG. 1, a GaN-based radiation detector 10 includes an n-doped GaN layer 11, which corresponds to a GaN substrate used as a drift layer. To improve response speed and reliability, the n-doped GaN layer 11 is doped with n-type 3×10 16 / cm 3 It is doped with a doping concentration of 700 cm 2 The n-doped GaN layer 11 has an electron mobility of 5×10 6 / cm 2 It may be the following:

[0034] A p-doped GaN layer 13 is formed on the top surface of the n-doped GaN layer 11. 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 by forming the GaN layer with a p-type 5×10 18 / cm 3 The doping concentration is 1000 or more, and the thickness is 3 um or less.

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

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

[0037] 2 and 3 show modified examples of the GaN-based radiation detector of FIG. 1. The same reference numerals are used to designate the same parts, and redundant descriptions will be 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 the portion of the p-doped GaN layer 13 may be performed 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 of the portion, and the cathode 15 may be formed to have a larger area to cover the entire area occupied by the anode 17.

[0038] 3, a concave-convex 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 face where many nitrogen atoms are exposed. In this case, the cathode 15 may be formed on the concave-convex structure 19. The concave-convex structure 19 can enhance absorption of radiation to be sensed, for example, X-rays. For example, the concave-convex structure 19 may be formed by a process such as etching.

[0039] 4, a first p-doped GaN layer 21 and a second p-doped GaN layer 23, which are p-doped with different p-doping concentrations, are sequentially formed on an n-doped GaN layer 11, which is the same GaN substrate as in the embodiment of FIG. 1. The first and second p-doped GaN layers 21 and 23 may be formed by doping GaN layers with p-type doping. The first p-doped GaN layer 21 is formed on the top surface of the n-doped GaN layer 11 and has a p-type doping concentration of 5×10. 18 / cm 3 The second p-doped GaN layer 23, doped at the first p-doping concentration above, is formed on the top surface of the first p-doped GaN layer 21 and is p-type with a doping concentration of 5×10 higher than the first p-doping concentration. 19 / cm 3 It may be doped at a second doping concentration equal to or greater than this.

[0040] Metallic junctions 15, 17 acting as electrodes are formed on the bottom surface of the n-doped GaN layer 11 and 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 p-type 5×10 18 / cm 3 ~5x10 20 / cm 3 The p-doped GaN layer may include a plurality of p-doped GaN layers having a thickness of 1 μm or less, successively doped with different p-doping concentrations within the range. In this case, the p-doped GaN layer may be doped with a higher p-type doping concentration as it ascends. For example, as shown in FIG. 4, when two p-doped GaN layers are formed, the lower p-doped GaN layer may have a p-type doping concentration of 5×10 18 / cm 3 ~5x10 20 / cm 3 The upper p-doped GaN layer is doped with a p-doping concentration in the range of 5x10 19 / cm 3 ~5x10 20 / cm 3 In other embodiments, three or more p-doped GaN layers may be formed in sequence.

[0042] 5 and 6 show modified examples of the GaN-based radiation detector of FIG. 4. The same reference numerals are used to designate the same parts, and redundant explanations will be omitted. Referring to FIGS. 5 and 6, portions of the p-doped GaN layers 21 and 23, for example, central portions, may be removed. The removal of the portions of the p-doped GaN layers 21 and 23 may be performed 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 of the portion, and the cathode 15 may be formed to have a larger area to cover the entire area occupied by the anode 17.

[0043] On the other hand, referring to FIG. 6, an uneven 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] A GaN-based radiation detector according to another embodiment of the present invention is shown in Figure 7. 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 and has a dopant concentration of 3×10 16 / cm 3 Doped at a doping concentration of 700 cm 2 The additional n-doped GaN layer 31 has a thickness of 5 μm or less, an n-type dopant concentration of 5×10 17 / cm 3 The doping is carried out at a doping concentration of 1000 ppm or more.

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

[0047] 8 and 9 show modified examples of the GaN-based radiation detector of FIG. 7. The same reference numerals are used to designate the same parts, and redundant descriptions will be 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 the portion of the n-doped GaN layer 31 may be performed 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 removal of the portion, and the anode 17 may be formed to have a larger area to cover the entire area occupied by the cathode 15.

[0048] 9, a concave-convex structure 19 may be formed on at least a portion of the bottom surface exposed by removing a portion of n-doped GaN layer 11, for example, a portion of n-doped GaN layer 31. Here, the bottom surface of n-doped GaN layer 11 may be a nitrogen face where many nitrogen atoms are exposed.

[0049] 10 and 11 show 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.

[0050] 11, a portion of the n-doped GaN layer 31, for example, a central portion thereof, may be removed, and the cathode 15 may be formed to have a ring shape. A concave-convex structure 19 may be formed on the upper surface of the n-doped GaN layer 11, which serves as the GaN substrate, and the anode 17 may be formed on the concave-convex structure 19.

[0051] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims also fall within the scope of the present invention.

Claims

1. 700 cm ２ / (V·s) or more and a thickness of 300 μm or more, and １６ / cm ３ an n-doped GaN layer doped with a doping concentration of: A p-type GaN layer having a thickness of 3 μm or less is formed on one side of the n-doped GaN layer. １８ / cm ３ a p-doped GaN layer doped at a doping concentration of at least a first metal junction formed on another surface of the n-doped GaN layer; a second metallic junction formed on one side of the p-doped GaN layer.

2. 700 cm ２ / (V·s) or more and a thickness of 300 μm or more, and １６ / cm ３ an n-doped GaN layer doped with a doping concentration of: The n-doped GaN layer is formed on one side thereof, and the p-type 5×10 １８ / cm ３ a first p-doped GaN layer doped at the first p-doping concentration; a p-type GaN layer having a doping concentration of 5×10 １９ / cm ３ a second p-doped GaN layer doped at a second doping concentration above; a first metal junction formed on another surface of the n-doped GaN layer; a second metallic junction formed on one side of the second p-doped GaN layer.

3. 700 cm ２ / (V·s) or more and a thickness of 300 μm or more, and １６ / cm ３ an n-doped GaN layer doped with a doping concentration of: The n-doped GaN layer is formed on one side thereof, and the p-type 5×10 １８ / cm ３ ~5x10 ２０ / cm ３ a plurality of p-doped GaN layers having a thickness of 1 μm or less, successively doped with different p-doping concentrations in the range; a first metal junction formed on another surface of the n-doped GaN layer; and second metallic junctions formed on one side of the plurality of p-doped GaN layers.

4. 4. The GaN-based radiation detector according to claim 1, wherein a part of the p-doped GaN layer can be removed.

5. 4. The GaN-based radiation detector according to claim 1, wherein at least a portion of one surface of said n-doped GaN layer has an uneven structure.

6. The defect concentration of the n-doped GaN layer is 5×10 ６ / cm ２ 4. The GaN-based radiation detector according to claim 1, wherein:

7. 700 cm ２ / (V·s) or more and a thickness of 300 μm or more, and １６ / cm ３ a first n-doped GaN layer doped with a doping concentration of: The first n-doped GaN layer is formed on one side of the first n-doped GaN layer, has a thickness of 5 μm or less, and is n-type 5×10 １７ / cm ３ a second n-doped GaN layer doped at a doping concentration of at least a first metal junction formed on another surface of the first n-doped GaN layer; a second metallic junction formed on one side of the second n-doped GaN layer.

8. 8. The GaN-based radiation detector according to claim 7, wherein a portion of the second n-doped GaN layer is removable.

9. 8. The GaN-based radiation detector according to claim 1, wherein at least a portion of the nitrogen face of the n-doped GaN layer is formed to have an uneven structure.

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