Gallium nitride-based radiation detector

Abstract

The present disclosure relates to a GaN-based radiation detector capable of detecting radiation such as X-rays. The radiation detector comprises a GaN layer in which a region generating electron-hole pairs by energy of incident radiation is doped, wherein the doped GaN layer is doped with a doping substance having an atomic number of at least 45. The doping of the GaN layer generating electron-hole pairs with a doping substance having an atomic number of at least 45 lowers the band gap energy, resultantly lowering the electron-hole pair generation energy, thereby enabling radiation detection with lower radiation energy.

Description

gallium nitride radiation detector

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

[0002] Recently, radiation detectors have been evolving toward photon counting, a direct detection method. This is because photon-counting radiation detectors offer the advantages of improved resolution and material-specific analysis. Photon-counting radiation detectors made from Cadmium Telluride (CdTe) have been developed. However, CdTe is inherently highly toxic, posing environmental concerns. Furthermore, its low strength makes chip manufacturing difficult. To overcome these shortcomings, materials such as GaAs (gallium arsenide), SiC (silicon carbide), Ga2O3 (gallium oxide), and GaN (gallium nitride) have been considered as suitable radiation detectors. Among these materials, GaN is known to be a promising alternative due to its durability under radiation, efficiency as a direct-transition semiconductor, and ease of processing. Recently, efforts have been made to fabricate photon-counting radiation detectors using GaN.

[0003] A GaN-based radiation detector fabricated with a HEMT (High Electron Mobility Transistor) structure or a PIN diode structure has been introduced. Since the HEMT structure is a horizontal structure, it is difficult to implement smaller pixels, which limits its resolution, so it is ultimately desirable to implement it with a PIN diode structure. When implementing a PIN diode-structured radiation detector using GaN, the I layer (intrinsic layer) plays a key role in determining the characteristics of the radiation detector. Here, the role of the GaN-based I layer is to absorb the energy of radiation internally when radiation is incident, generating electron-hole pairs, and the generated electron-hole pairs become current and are detected.

[0004] However, due to the material properties of GaN, its high bandgap energy requires more energy to generate electrons and holes. While GaN has the advantage of being resistant to external noise due to its large bandgap energy, the requirement for higher electron-hole generation energy also presents the problem of requiring stronger radiation energy to be transmitted to the subject. This increase in radiation energy is particularly undesirable when the subject is a human body.

[0005] Also, as is known, in order to promote the generation of electron-hole pairs in GaN-based radiation detectors, it is required to reduce crystal defects in GaN and minimize impurities, but this also has physical limitations in maximizing the generation of electron-hole pairs. For example, the defect density of commercially available GaN substrates is approximately 5x10 6 / cm 2 , the impurity concentration is 5x10 16 / cm 3 This is ideal. Therefore, while improvements can be made, a method that can further maximize the generation of electron-hole pairs is urgently needed.

[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] The problem to be solved by the present invention is to provide a GaN-based radiation detector capable of detecting radiation using less radiation energy than conventional ones.

[0008] 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.

[0009] A radiation detector according to an embodiment of the present invention includes a doped GaN layer in which a region generating electron-hole pairs by the energy of incident radiation is doped with a doping material having an atomic number of 45 or higher.

[0010] According to another embodiment of the present invention, a radiation detector comprises a doped GaN layer in which a region generating electron-hole pairs by the energy of incident radiation is doped, and the doped GaN layer is doped with one or more doping materials selected from the group consisting of Ag (silver), In (Indium), Sn (Tin), Ir (Iridium), Pt (Platinum), Au (Gold), Pb (Lead), and Er (Erbium).

[0011] The above doped GaN layer may be additionally doped with one or more of C (Carbon) and Fe (Iron). This additional doping can partially reduce the electron concentration unnecessarily increased by the doping with Ag, etc. described above.

[0012]

[0013] *The above doped GaN layer may have a band gap energy of 2 to 2.8 eV and an electron-hole pair creation energy of 3.4 to 7.2 eV.

[0014] The above doped GaN layer is 0.5 cm when irradiated with 100 keV energy. 2 / g or more can have a linear attenuation coefficient.

[0015] A radiation detector according to another embodiment of the present invention may further include an n-doped GaN layer and a p-doped GaN layer respectively disposed on upper and lower sides of the doped GaN layer.

[0016] A radiation detector according to another embodiment of the present invention may further include a pair of electrodes each disposed on the upper and lower sides of the doped GaN layer.

[0017] The above doped GaN layer may be doped with 5 to 40% of the above doping material.

[0018] The thickness of the above doped GaN layer can be in the range of 10 to 2000 μm. Setting the thickness within this range enables the generation of more electron-hole pairs by incident radiation and the generation of a larger current.

[0019] According to another embodiment of the present invention, a radiation detector includes a GaN layer in a region that generates electron-hole pairs by the energy of incident radiation. The GaN layer includes a doped GaN layer and an undoped GaN layer, and the doped GaN layer is doped with a doping material having an atomic number of 45 or higher.

[0020] According to another embodiment of the present invention, a radiation detector includes a GaN layer in a region that generates electron-hole pairs by the energy of incident radiation. The GaN layer includes a doped GaN layer and an undoped GaN layer, and the doped GaN layer is doped with one or more doping materials selected from the group consisting of Ag (silver), In (Indium), Sn (Tin), Ir (Iridium), Pt (Platinum), Au (Gold), Pb (Lead), and Er (Erbium).

[0021] When including a doped GaN layer and an undoped GaN layer, the doped GaN layer can be doped with a doping material at a ratio of 5 to 100%. The thickness of each layer can be reduced through a multiple layer structure, and the doping concentration can be easily controlled by reducing the thickness of the layer, thereby enabling high concentration doping. In addition, as described above, in the case of a single doped GaN layer, the doping ratio is limited to 5 to 40% to prevent the band gap from becoming too low and noise generation from increasing, but in the case of multiple layers, noise generation can be reduced by inserting an undoped GaN layer.

[0022] According to the present invention, by doping a GaN layer that generates electron-hole pairs with a doping material having an atomic number of 45 or higher, the band gap energy can be lowered, thereby lowering the electron-hole pair generation energy, and thereby radiation detection can be performed with lower radiation energy.

[0023] 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.

[0024] FIG. 1 is a cross-sectional view showing a GaN-based radiation detector according to an embodiment of the present invention.

[0025] Figure 2 is a graph showing the simulation results of the linear attenuation coefficient of a material according to radiation energy.

[0026] FIG. 3 is a cross-sectional view showing a GaN-based radiation detector according to another embodiment of the present invention.

[0027] 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.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the 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 one or all combinations of one or more of the associated listed items. The term "coupled" indicates a physical relationship between two components, wherein the components are directly connected to one another or are indirectly connected through one or more intervening components.

[0029] When describing a component of the present invention, if 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 that another component may also be "connected," "coupled," or "connected" between the components. Furthermore, when describing a component of the present invention, if it is described that a component is positioned "above" or "below" another component, it should be understood that it includes not only cases where a component is positioned directly above or directly below the other component, but also cases where another component is positioned between the two components.

[0030] FIG. 1 illustrates a cross-section of a GaN-based radiation detector (10) according to an embodiment of the present invention. Referring to FIG. 1, the GaN-based radiation detector (10) includes an n-doped GaN layer (11) doped with n type, a p-doped GaN layer (12) doped with p type, and a doped GaN layer (13). The GaN-based radiation detector (10) is based on a GaN material and implements a radiation detection function through a PIN diode structure. The doped GaN layer (13) corresponds to an I layer, which is a core layer of the PIN diode structure, and absorbs the energy of incident radiation to generate electron-hole pairs.

[0031] The n-type doping of the n-doped GaN layer (11) can be achieved by n-type doping using silicon (Si) as a dopant, and silane (SiH4) can be used as a dopant source. The p-type doping of the p-doped GaN layer (12) can be achieved by p-type doping using magnesium (Mg) as a dopant, and biscyclopentadienyl-magnesium can be used as a dopant source.

[0032] In order to improve the generation rate of electron-hole pairs of a radiation detector, a material having an atomic number of 45 or higher is doped into the GaN intrinsic layer (13), thereby implementing a doped GaN layer (13). At this time, the ratio of the doped material is doped at 5 to 40% with respect to Ga (gallium). If the doping is performed at a ratio greater than 40%, there is a problem that the band gap energy is excessively reduced, which increases the generation of noise, and if the doping is performed at a ratio less than 5%, the desired degree of reduction in band gap energy is not achieved. Therefore, in the embodiment of the present invention, a doping ratio of 5 to 40% was selected. In order to improve the absorption of radiation energy, considering that atoms with more electrons are advantageous, a doped GaN layer (13) can be formed by doping materials with a higher atomic number than Ga, such as Ag (silver), In (Indium), Sn (Tin), Ir (Iridium), Pt (Platinum), Au (Gold), Pb (Lead), and Er (Erbium). By doping these materials, the band gap energy (E) of GaN can be increased. g ) can be reduced, and the reduced band gap energy leads to a decrease in the electron-hole pair generation energy, thereby generating more electrons and holes for the same radiation energy.

[0033] The electron-hole pair creation energy (ε) has a value that is basically proportional to the band gap energy of the material, and can be expressed as a value according to the following mathematical equation 1.

[0034] [Mathematical Formula 1]

[0035]

[0036] Here, E g represents the band gap energy, and hω r represents the optical phonon losses, and γ represents the average number of optical phonons.

[0037] Since the electron-hole pair generation energy is roughly proportional to the band gap energy, lowering the band gap energy can lower the electron-hole pair generation energy. Based on this point, lowering the band gap energy of the GaN intrinsic layer (13) through doping can simultaneously lower the electron-hole pair generation energy. This doping can reduce the band gap energy of GaN and generate more electron-hole pairs through more radiation energy absorption in the doped material. The more electron-hole pairs generated act as more current to the detector, so that a GaN-based radiation detector that can operate at lower radiation energy compared to general GaN can be manufactured. In particular, doping with In can be easily achieved as it is a material that is widely used in the manufacture of GaN devices, and there are cases where it has been doped with Ir and Er or for the manufacture of other devices.

[0038] Figure 2 is a graph showing the simulation results of the linear attenuation coefficient of four materials (CdTe, GaN, InGaN, IrGaN) according to radiation energy. Referring to the results shown in Figure 2, it can be seen that the linear attenuation coefficient increases for incident radiation of about 100 KeV when doped with In or Ir compared to general GaN. This means that the incident radiation can react more with the material and generate more electron-hole pairs. Therefore, doping GaN with a material with an atomic number of 45 or higher can dramatically improve the radiation incidence efficiency.

[0039] The doped GaN layer (13) may be additionally doped with one or more of C (Carbon) and Fe (Iron). When doping GaN with materials such as Ag (silver), In (Indium), Sn (Tin), Ir (Iridium), Pt (Platinum), Au (Gold), Pb (Lead), and Er (Erbium) described above, there may be a problem that an unnecessary increase in electron concentration may occur. When electron-hole pairs are generated in the I layer, i.e., the doped GaN layer (13), these move to the upper and lower electrodes and generate current. However, if the electron concentration increases too much when doping GaN in the I layer, the movement of the generated electrons and holes is hindered, thereby reducing the amount of current generated. At this time, additional addition of C and Fe can reduce some of the unnecessary increase in electron concentration.

[0040] Metal junctions (15, 16) 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 (12), 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 (16) formed on the upper surface of the p-doped GaN layer (12) 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 (16), thereby enabling radiation detection.

[0041] FIG. 3 illustrates a cross-section of a GaN-based radiation detector (20) according to another embodiment of the present invention. Referring to FIG. 3, a GaN intrinsic layer (23) is provided between an n-doped GaN layer (21) and a p-doped GaN layer (22), and the GaN intrinsic layer (23) includes at least one pair of doped GaN layers (231) and undoped GaN intrinsic layers (232). The doped GaN layer (231) may be formed by doping GaN with a material having an atomic number of 45 or higher, similarly to the embodiment described above. The doped GaN layer (231) may be formed to have a thickness of 2 nm to 2 μm, and may be formed by growing as a single layer, as exemplarily illustrated in FIG. 3. Alternatively, the doped GaN layer (231) may be formed in an island or dot structure rather than a single layer structure. By forming the GaN intrinsic layer (23) by combining the doped GaN layer (231) and the undoped GaN intrinsic layer (232), the ease of manufacturing can be improved. The structure having multiple layers can reduce the thickness of each layer, and as each layer becomes thinner, the doping concentration can be easily controlled, enabling high-concentration doping. In addition, the occurrence of defects can be reduced by inserting an undoped layer in the middle. When formed with a single layer, the band gap may become too small, which may increase the occurrence of noise, but when formed with multiple thin layers, the occurrence of noise can be reduced by inserting undoped GaN layers. Taking this into account, when inserting an undoped GaN layer (232), the doping concentration of the doped GaN layer (231) can be doped at a higher doping ratio than in the embodiment described above, for example, can be doped at a doping ratio in the range of 5 to 100%.

[0042] Furthermore, metal junctions (25, 26) acting as electrodes are formed on the lower surface of the n-doped GaN layer (21) and the upper surface of the p-doped GaN layer (22), respectively.

[0043] Example: Fabrication of a radiation detector using doped GaN

[0044] The growth of doped GaN for the manufacture of radiation detectors can be accomplished in various ways, for example, by MOVPE or HVPE growth methods. Doped GaN can be grown by additionally adding a doping material during the growth of GaN. In the radiation detector, the region where electron-hole pairs are generated by incident radiation can be doped with a material having an atomic number of 45 or higher. In this embodiment, In (Indium) is used as the material having an atomic number of 45 or higher. When doping a material into GaN, doping is mostly done by replacing Ga, and the doped GaN is In. (x) Ga (1-x) It can be expressed in the form of N, where x represents the doping amount. For example, if the value of x is 0.3, it means that In occupies 30% and Ga occupies 70%. In other words, since 30% of the space that was originally filled with 100% Ga is now occupied by In, Ga becomes 70%.

[0045] When growing GaN, the appropriate doping material is a material with an atomic number of 45 or higher, and can be one or more of the following materials: Ag (silver), In (Indium), Sn (Tin), Ir (Iridium), Pt (Platinum), Au (Gold), Pb (Lead), and Er (Erbium). When doping the GaN intrinsic layer, C (Carbon) or Fe (Iron) can be doped simultaneously with the doping of a material with an atomic number of 45 or higher.

[0046] At this time, the doped GaN layer was 0.5 cm when radiation with an energy of 100 KeV was incident. 2 / g or more. The doping concentration of the doped material to form the doped GaN layer can be adjusted to fall within the range of 5 to 40%, and the thickness of the doped GaN layer can fall within the range of 10 to 2000 μm. This thickness range was set considering that, in a PIN structure radiation detector, theoretically, the thicker the I layer, the more electron-hole pairs the incident radiation can create and the larger the current. In this case, if the GaN layer is a composite structure of a doped layer and an undoped layer, the thickness of each layer can be set smaller.

[0047] P-type and n-type doping can be added to the upper and lower portions of the grown doped GaN layer, and additional p-type and n-type layers can be stacked. In addition, a metal junction can be formed to form an electrode structure for measuring the current generated by the incident radiation.

[0048] 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. A region that generates electron-hole pairs by the energy of incident radiation includes a doped GaN layer, A GaN-based radiation detector in which the above doped GaN layer is doped with a doping material having an atomic number of 45 or higher.

2. A region that generates electron-hole pairs by the energy of incident radiation includes a doped GaN layer, A GaN-based radiation detector in which the above doped GaN layer is doped with one or more doping materials selected from the group consisting of Ag (silver), In (Indium), Sn (Tin), Ir (Iridium), Pt (Platinum), Au (Gold), Pb (Lead), and Er (Erbium).

3. In paragraph 1 or 2, A GaN-based radiation detector wherein the above doped GaN layer is additionally doped with at least one of C (Carbon) and Fe (Iron).

4. In paragraph 1 or 2, A GaN-based radiation detector wherein the doped GaN layer has a band gap energy of 2 to 2.8 eV and an electron-hole pair creation energy of 3.4 to 7.2 eV.

5. In paragraph 1 or 2, The above doped GaN layer is 0.5 cm when irradiated with 100 keV energy. 2 A GaN-based radiation detector having a linear attenuation coefficient of / g or greater.

6. In paragraph 1 or 2, A GaN-based radiation detector further comprising an n-doped GaN layer and a p-doped GaN layer respectively disposed on upper and lower sides of the above-described doped GaN layer.

7. In paragraph 1 or 2, A GaN-based radiation detector further comprising a pair of electrodes each arranged on the upper and lower sides of the doped GaN layer.

8. In paragraph 1 or 2, A GaN-based radiation detector in which the doped GaN layer is doped with 5 to 40% of the doping material.

9. In paragraph 1 or 2, A GaN-based radiation detector, wherein the thickness of the doped GaN layer is in the range of 10 to 2000 μm.

10. The region that generates electron-hole pairs by the energy of the incident radiation includes a GaN layer, The above GaN layer includes a doped GaN layer and an undoped GaN layer, A GaN-based radiation detector in which the above doped GaN layer is doped with a doping material having an atomic number of 45 or higher.

11. The region that generates electron-hole pairs by the energy of the incident radiation includes a GaN layer, The above GaN layer includes a doped GaN layer and an undoped GaN layer, A GaN-based radiation detector in which the above doped GaN layer is doped with one or more doping materials selected from the group consisting of Ag (silver), In (Indium), Sn (Tin), Ir (Iridium), Pt (Platinum), Au (Gold), Pb (Lead), and Er (Erbium).

12. In paragraph 10 or 11, A GaN-based radiation detector further comprising an n-doped GaN layer and a p-doped GaN layer respectively disposed on the upper and lower sides of the GaN layer.

13. In paragraph 10 or 11, A GaN-based radiation detector in which the doped GaN layer is doped with the doping material at a level of 5 to 100%.

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