A nuclear battery structure and preparation method thereof

Abstract

The present invention relates to the field of nuclear battery technology, and specifically discloses a nuclear battery structure, which includes: a first nuclear battery chip, a second nuclear battery chip, and a radioactive isotope source layer located between the first nuclear battery chip and the second nuclear battery chip, wherein the first nuclear battery chip and the second nuclear battery chip both include a first conductive type substrate, a first conductive type epitaxial layer, a second conductive type epitaxial layer with a first doping concentration, a second conductive type epitaxial layer with a second doping concentration, a second conductive type ohmic contact layer, and a metal bonding layer sequentially arranged on the first conductive type substrate, the radioactive isotope source layer is in contact with the metal bonding layer of the first nuclear battery chip and the metal bonding layer of the second nuclear battery chip, respectively, and the first conductive type ohmic contact layer is arranged on one side of the first conductive type substrate away from the radioactive isotope source layer. The present invention also discloses a method for preparing a nuclear battery. The nuclear battery structure provided by the present invention can improve energy conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear batteries, and in particular to a nuclear battery structure and a method for preparing the nuclear battery. Background Art

[0002] Radioisotope batteries, also known as nuclear batteries, are devices that use the energy released by the decay of radioisotopes to generate electricity.

[0003] With the development of micro-electromechanical systems, the issue of energy supply is particularly important. As electronic products are miniaturized, micro-miniaturized, and integrated, energy must also be miniaturized and micro-miniaturized. Nuclear batteries have the advantages of small size, long life, light weight, no influence of external environment, high specific power, and easy miniaturization, making them an ideal energy source for micro-electromechanical systems. Due to its excellent characteristics, it can be used in aerospace, deep sea, polar regions, and other places that require long-term power supply and unattended operation.

[0004] In recent years, research on nuclear batteries has been extensive. Improving the energy conversion efficiency of nuclear batteries has always been the focus of research. Semiconductor nuclear batteries use the radiovoltaic effect of semiconductors to convert the decay of isotope source energy into electrical energy. Gallium nitride (GaN), as a third-generation semiconductor material, has the characteristics of strong radiation resistance and high bandgap width, and is particularly suitable for making nuclear battery materials. One way to form a gallium nitride-based nuclear battery is to use a PIN-type diode structure as the main body, on which the isotope source is integrated through bonding and other methods, and finally packaged into a nuclear battery.

[0005] At present, the general method of packaging nuclear batteries is to bond or plate the isotope source layer onto the surface of the nuclear battery, which has limitations in improving the energy conversion efficiency of nuclear batteries. Summary of the invention

[0006] The present invention provides a nuclear battery structure and a method for preparing the nuclear battery, which solve the problem of low energy conversion efficiency of the nuclear battery existing in the related art.

[0007] As a first aspect of the present invention, a nuclear battery structure is provided, which includes: a first nuclear battery chip, a second nuclear battery chip and a radioactive isotope source layer located between the first nuclear battery chip and the second nuclear battery chip, the first nuclear battery chip and the second nuclear battery chip each including a first conductive type substrate, a first conductive type epitaxial layer, a second conductive type epitaxial layer with a first doping concentration, a second conductive type epitaxial layer with a second doping concentration, a second conductive type ohmic contact layer and a metal bonding layer sequentially arranged on the first conductive type substrate toward the radioactive isotope source layer, the radioactive isotope source layer is in contact with the metal bonding layer of the first nuclear battery chip and the metal bonding layer of the second nuclear battery chip respectively, and a first conductive type ohmic contact layer is arranged on a side of the first conductive type substrate of the first nuclear battery chip and the second nuclear battery chip facing away from the radioactive isotope source layer.

[0008] Further, when the first nuclear battery chip and the second nuclear battery chip both include an N-type nuclear battery chip and a P-type nuclear battery chip, when the first nuclear battery chip and the second nuclear battery chip are both the N-type nuclear battery chips, the first conductivity type is N-type and the second conductivity type is P-type; when the first nuclear battery chip and the second nuclear battery chip are both P-type nuclear battery chips, the first conductivity type is P-type and the second conductivity type is N-type.

[0009] Furthermore, the first conductive type epitaxial layer includes an N-type gallium nitride epitaxial layer, the thickness of the N-type gallium nitride epitaxial layer is between 3 μm and 10 μm, and the doping concentration of the N-type gallium nitride epitaxial layer is between 1×10 15 cm -3 ~2×10 15 cm -3 between.

[0010] Furthermore, the second conductivity type epitaxial layer of the first doping concentration includes a P-type gallium nitride epitaxial layer, the thickness of the P-type gallium nitride epitaxial layer is between 0.1 μm and 0.2 μm, and the doping concentration of the P-type gallium nitride epitaxial layer is between 4×10 17 cm -3 ~5×10 17 cm -3 between.

[0011] Furthermore, the second conductivity type epitaxial layer of the second doping concentration includes a P+ type gallium nitride epitaxial layer, the thickness of the P+ type gallium nitride epitaxial layer is between 5nm and 10nm, and the doping concentration of the P+ type gallium nitride epitaxial layer is between 2×10 19 cm -3 ~5×10 19 cm -3 between.

[0012] Furthermore, the first conductive type substrate includes an N-type gallium nitride substrate, and a thickness of the N-type gallium nitride substrate is between 300 μm and 500 μm.

[0013] Further, the second conductive type ohmic contact layer includes a P-type ohmic contact layer, and the P-type ohmic contact layer includes a Ti metal layer with a thickness of 100 nm.

[0014] Further, the first conductive type ohmic contact layer includes an N-type ohmic contact layer, and the N-type ohmic contact layer includes a Ti metal layer and an Al metal layer, and the thickness of the Ti metal layer is 100 nm, and the thickness of the Al metal layer is 3 μm.

[0015] Furthermore, the metal bonding layer includes a P-type metal bonding layer, and the P-type metal bonding layer includes an Al metal layer with a thickness of 3 μm.

[0016] As another aspect of the present invention, a method for preparing a nuclear battery is provided, which is used to prepare the nuclear battery structure described above, and comprises:

[0017] providing a first conductive type substrate;

[0018] growing a first conductivity type epitaxial layer on the first conductivity type substrate;

[0019] Growing a second conductivity type epitaxial layer with a first doping concentration on the first conductivity type epitaxial layer;

[0020] growing a second conductivity type epitaxial layer with a second doping concentration on the second conductivity type epitaxial layer with the first doping concentration;

[0021] Depositing a metal layer on the second conductive type epitaxial layer and etching to obtain a second conductive type ohmic contact layer;

[0022] Depositing a metal layer on the second conductive type ohmic contact layer and etching to obtain a metal bonding layer;

[0023] Depositing a metal layer on a surface of the first conductive type substrate away from the first conductive type epitaxial layer to obtain a first conductive type ohmic contact layer, and annealing to obtain a first nuclear battery chip;

[0024] Repeat the above steps to obtain a second nuclear battery chip;

[0025] The radioactive isotope source layer is placed between the first nuclear battery chip and the second nuclear battery chip, and the radioactive isotope source layer is respectively fixed to the first nuclear battery chip and the second nuclear battery chip and then packaged.

[0026] Wherein, a first conductive type ohmic contact layer is disposed on a side of the first conductive type substrate of the first nuclear battery chip and the second nuclear battery chip facing away from the radioactive isotope source layer.

[0027] The nuclear battery structure provided by the present invention packages two nuclear batteries face to face, places a radioactive isotope source layer between two nuclear battery chips, and then packages them. The nuclear battery structure is equivalent to having two depletion regions, which improves the collection efficiency of electron-hole pairs, thereby improving the energy conversion efficiency of the nuclear battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0029] Figure 1 This is a schematic structural diagram of the nuclear battery structure provided by the present invention.

[0030] Figure 2 This is a schematic structural diagram of the first core battery chip or the second core battery chip provided by the present invention.

[0031] Figure 3 This is a schematic diagram of the structure of the nuclear battery after packaging provided by the present invention. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] In this embodiment, a nuclear battery structure is provided. Figure 1 is a schematic diagram of a nuclear battery structure provided according to an embodiment of the present invention, Figure 2 is a schematic diagram of the structure of the first core battery chip or the second core battery chip, such as Figure 1 and Figure 2 As shown, it includes: a first nuclear battery chip 10, a second nuclear battery chip 20 and a radioactive isotope source layer 8 located between the first nuclear battery chip 10 and the second nuclear battery chip 20. The first nuclear battery chip 10 and the second nuclear battery chip 20 both include a first conductive type substrate 1, a first conductive type epitaxial layer 2, a second conductive type epitaxial layer 3 with a first doping concentration, a second conductive type epitaxial layer 4 with a second doping concentration, a second conductive type ohmic contact layer 5 and a metal bonding layer 6 arranged in sequence on the first conductive type substrate 1 toward the radioactive isotope source layer 8. The radioactive isotope source layer 8 is in contact with the metal bonding layer of the first nuclear battery chip 10 and the metal bonding layer of the second nuclear battery chip 20 respectively. The first conductive type ohmic contact layer 7 is arranged on the side of the first conductive type substrate 1 of the first nuclear battery chip 10 and the second nuclear battery chip 20 facing away from the radioactive isotope source layer 8.

[0036] The nuclear battery structure provided by the embodiment of the present invention packages two nuclear batteries face to face, places the radioisotope source layer between the two nuclear battery chips, and then packages them. The nuclear battery structure is equivalent to having two depletion regions, which improves the collection efficiency of electron-hole pairs, thereby improving the energy conversion efficiency of the nuclear battery.

[0037] Specifically, when the first nuclear battery chip 10 and the second nuclear battery chip 20 both include an N-type nuclear battery chip and a P-type nuclear battery chip, when the first nuclear battery chip and the second nuclear battery chip are both the N-type nuclear battery chips, the first conductivity type is N-type and the second conductivity type is P-type; when the first nuclear battery chip and the second nuclear battery chip are both P-type nuclear battery chips, the first conductivity type is P-type and the second conductivity type is N-type.

[0038] It should be noted that the first nuclear battery chip 10 and the second nuclear battery chip 20 in the embodiment of the present invention are both described by taking an N-type nuclear battery chip as an example.

[0039] Specifically, the first conductive type epitaxial layer 2 includes an N-type gallium nitride epitaxial layer, the thickness of the N-type gallium nitride epitaxial layer is between 3 μm and 10 μm, and the doping concentration of the N-type gallium nitride epitaxial layer is between 1×10 15 cm -3 ~2×10 15 cm -3 between.

[0040] Specifically, the second conductivity type epitaxial layer 3 of the first doping concentration includes a P-type gallium nitride epitaxial layer, the thickness of the P-type gallium nitride epitaxial layer is between 0.1 μm and 0.2 μm, and the doping concentration of the P-type gallium nitride epitaxial layer is between 4×10 17 cm -3 ~5×10 17 cm -3 between.

[0041] Specifically, the second conductive type epitaxial layer 4 of the second doping concentration includes a P+ type gallium nitride epitaxial layer, the thickness of the P+ type gallium nitride epitaxial layer is between 5nm and 10nm, and the doping concentration of the P+ type gallium nitride epitaxial layer is between 2×10 19 cm -3 ~5×10 19 cm -3 between.

[0042] Specifically, the first conductive type substrate 1 includes an N-type gallium nitride substrate, and the thickness of the N-type gallium nitride substrate is between 300 μm and 500 μm.

[0043] In the embodiment of the present invention, the resistivity of the N-type gallium nitride substrate is 0.015Ω•cm.

[0044] Specifically, the second conductive type ohmic contact layer 5 includes a P-type ohmic contact layer, and the P-type ohmic contact layer includes a Ti metal layer with a thickness of 100 nm.

[0045] Specifically, the first conductive type ohmic contact layer 7 includes an N-type ohmic contact layer, and the N-type ohmic contact layer includes a Ti metal layer and an Al metal layer, wherein the thickness of the Ti metal layer is 100 nm, and the thickness of the Al metal layer is 3 μm.

[0046] In the embodiment of the present invention, the metal bonding layer includes a P-type metal bonding layer, and the P-type metal bonding layer includes an Al metal layer with a thickness of 3 μm.

[0047] As another embodiment of the present invention, a method for preparing a nuclear battery is provided, which is used to prepare the nuclear battery structure described above, wherein: Figures 1 to 3 As shown, including:

[0048] A first conductive type substrate 1 is provided. In the embodiment of the present invention, an N-type gallium nitride substrate material is prepared. The N-type substrate is grade B, with a typical thickness of 300-500 um and a resistivity of 0.015 Ω•cm.

[0049] A first conductive type epitaxial layer 2 is grown on the first conductive type substrate 1. Specifically, the epitaxial layer 2 is grown on an N-type gallium nitride substrate with a thickness between 3 μm and 10 μm and a doping concentration between 1×10 15 cm -3 ~2×10 15 cm -3 An initial N-type GaN epitaxial layer between;

[0050] A second conductive type epitaxial layer 3 with a first doping concentration is grown on the first conductive type epitaxial layer 2. Specifically, a P type epitaxial layer with a thickness between 0.1 μm and 0.2 μm and a doping concentration between 4×10 17 cm -3 ~5×10 17 cm -3 between;

[0051] A second conductive type epitaxial layer 4 with a second doping concentration is grown on the second conductive type epitaxial layer 3 with the first doping concentration. Specifically, a highly doped P+ epitaxial layer is grown on the P type epitaxial layer, with a thickness between 5 nm and 10 nm and a doping concentration between 2×10 19 cm -3 ~5×10 19 cm -3 between;

[0052] Depositing a metal layer on the second conductive type epitaxial layer and etching to obtain a second conductive type ohmic contact layer;

[0053] Depositing a metal layer on the second conductive type ohmic contact layer and etching to obtain a metal bonding layer;

[0054] Depositing a metal layer on a surface of the first conductive type substrate away from the first conductive type epitaxial layer to obtain a first conductive type ohmic contact layer, and rapidly annealing at a high temperature of 1050° C. for 3 minutes to finally obtain a first nuclear battery chip;

[0055] Repeat the above steps to obtain a second nuclear battery chip;

[0056] The radioactive isotope source layer is placed between the first nuclear battery chip and the second nuclear battery chip, and the radioactive isotope source layer is respectively fixed to the first nuclear battery chip and the second nuclear battery chip and then packaged.

[0057] Wherein, a first conductive type ohmic contact layer is disposed on a side of the first conductive type substrate of the first nuclear battery chip and the second nuclear battery chip facing away from the radioactive isotope source layer.

[0058] It should be noted that the second conductive type ohmic contact layer 5 includes a P-type ohmic contact layer, and the P-type ohmic contact layer includes a Ti metal layer with a thickness of 100nm; the first conductive type ohmic contact layer 7 includes an N-type ohmic contact layer, and the N-type ohmic contact layer includes a Ti metal layer and an Al metal layer, and the thickness of the Ti metal layer is 100nm, and the thickness of the Al metal layer is 3μm; in an embodiment of the present invention, the metal bonding layer includes a P-type metal bonding layer, and the P-type metal bonding layer includes an Al metal layer with a thickness of 3μm.

[0059] In the embodiment of the present invention, the radioisotope source layer 8 is made of Sr 90 Or Pm 147 A radiation source is provided, wherein a radioactive isotope source layer 8 is placed between two nuclear battery chips, fixed to the two chips, and then packaged into a tube shell 10. The tube shell 10 is provided with a tube shell cover plate 9. A P-side electrode line connected to the radioactive isotope source layer 8 is connected to a tube shell surface pin 13 of the tube shell 10, and an N-side electrode line 12 connected to the N-type ohmic contact layer is connected to another tube shell surface pin 13 of the tube shell 10.

[0060] In summary, the nuclear battery structure prepared by the nuclear battery preparation method provided in the embodiment of the present invention can improve the collection efficiency of electron-hole pairs, greatly improve the energy conversion efficiency of the nuclear battery, and the preparation process is simple and the preparation cost is low.

[0061] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A nuclear battery structure, characterized in that: include: A first nuclear battery chip, a second nuclear battery chip, and a radioactive isotope source layer located between the first nuclear battery chip and the second nuclear battery chip, wherein the first nuclear battery chip and the second nuclear battery chip each include a first conductive type substrate, a first conductive type epitaxial layer, a second conductive type epitaxial layer with a first doping concentration, a second conductive type epitaxial layer with a second doping concentration, a second conductive type ohmic contact layer, and a metal bonding layer sequentially arranged on the first conductive type substrate toward the radioactive isotope source layer, the radioactive isotope source layer is in contact with the metal bonding layer of the first nuclear battery chip and the metal bonding layer of the second nuclear battery chip, respectively, and a first conductive type ohmic contact layer is arranged on a side of the first conductive type substrate of the first nuclear battery chip and the second nuclear battery chip facing away from the radioactive isotope source layer; The first conductive type epitaxial layer includes an N-type gallium nitride epitaxial layer, the thickness of the N-type gallium nitride epitaxial layer is between 3 μm and 10 μm, and the doping concentration of the N-type gallium nitride epitaxial layer is between 1×10 15 cm -3 ~2×10 15 cm -3 between; The second conductivity type epitaxial layer of the first doping concentration includes a P-type gallium nitride epitaxial layer, the thickness of the P-type gallium nitride epitaxial layer is between 0.1 μm and 0.2 μm, and the doping concentration of the P-type gallium nitride epitaxial layer is between 4×10 17 cm -3 ~5×10 17 cm -3 between; The second conductivity type epitaxial layer of the second doping concentration includes a P+ type gallium nitride epitaxial layer, the thickness of the P+ type gallium nitride epitaxial layer is between 5nm and 10nm, and the doping concentration of the P+ type gallium nitride epitaxial layer is between 2×10 19 cm -3 ~5×10 19 cm -3 between; The first conductive type substrate includes an N-type gallium nitride substrate, and the thickness of the N-type gallium nitride substrate is between 300 μm and 500 μm; The second conductive type ohmic contact layer includes a P-type ohmic contact layer, and the P-type ohmic contact layer includes a Ti metal layer with a thickness of 100 nm; The first conductive type ohmic contact layer includes an N-type ohmic contact layer, and the N-type ohmic contact layer includes a Ti metal layer and an Al metal layer, and the thickness of the Ti metal layer is 100 nm, and the thickness of the Al metal layer is 3 μm; The metal bonding layer includes a P-type metal bonding layer, and the P-type metal bonding layer includes an Al metal layer with a thickness of 3 μm.

2. A method for preparing a nuclear battery, used for preparing the nuclear battery structure according to claim 1, characterized in that: include: providing a first conductive type substrate; growing a first conductivity type epitaxial layer on the first conductivity type substrate; Growing a second conductivity type epitaxial layer with a first doping concentration on the first conductivity type epitaxial layer; growing a second conductivity type epitaxial layer with a second doping concentration on the second conductivity type epitaxial layer with the first doping concentration; Depositing a metal layer on the second conductive type epitaxial layer and etching to obtain a second conductive type ohmic contact layer; Depositing a metal layer on the second conductive type ohmic contact layer and etching to obtain a metal bonding layer; Depositing a metal layer on a surface of the first conductive type substrate away from the first conductive type epitaxial layer to obtain a first conductive type ohmic contact layer, and annealing to obtain a first nuclear battery chip; Repeat the above steps to obtain a second nuclear battery chip; The radioactive isotope source layer is placed between the first nuclear battery chip and the second nuclear battery chip, and the radioactive isotope source layer is respectively fixed to the first nuclear battery chip and the second nuclear battery chip and then packaged. Wherein, a first conductive type ohmic contact layer is disposed on a side of the first conductive type substrate of the first nuclear battery chip and the second nuclear battery chip facing away from the radioactive isotope source layer.

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