CN101527174B - Schottky type nuclear battery and preparation method thereof - Google Patents

Abstract

The invention discloses a Schottky type nuclear battery and a preparation method thereof. The Schottky type nuclear battery with a substrate-n-type GaN doped layer-insulating GaN doped layer structure is grown through the composite epitaxial technology of one MOCVD epitaxy and one HVPE epitaxy. The device material structure is then sputtered using a semiconductor micromachining process to generate the corresponding contact electrode to prepare the basic battery device. The isotope is coupled to the Schottky contact electrode, and the nuclear battery is packaged and prepared. Since the life of the nuclear battery depends on the half-life of the isotope, the present invention can flexibly use isotope types with simple protection (pure β isotopes), greatly improving the energy conversion efficiency and energy density (energy volume) of the nuclear battery, and extending the life of the nuclear battery. service life, and also creates an effective way for nuclear waste to be turned into treasure and rationally utilized.

Description

Schottky nuclear battery and its preparation method

technical field

The invention relates to a semiconductor nuclear battery device, in particular to a radiation volt effect nuclear battery in a primary conversion nuclear battery, and belongs to the field of energy applications.

Background technique

Generally speaking, batteries include chemical batteries and physical batteries. Chemical batteries mainly include dry batteries, storage batteries, fuel cells, microbial batteries, etc. These are commonly used battery types in human life, but the energy volume of such batteries is relatively small and cannot meet the needs of long-term power supply. Physical batteries mainly include solar cells and nuclear batteries. Nuclear batteries are also called isotope batteries or atomic batteries, which are batteries that directly convert the radioactive energy of atomic nuclei into electrical energy. According to different energy sources, nuclear batteries can be divided into heat source nuclear batteries and radiation energy nuclear batteries. Heat source nuclear batteries use isotope decay heat, such as thermoelectric effect nuclear batteries; radiant energy nuclear batteries use the ray energy generated when isotopes decay, this energy is far greater than decay heat, such as volt effect nuclear batteries. According to the number of energy conversion processes, it can be divided into primary conversion nuclear batteries (such as thermoelectric effect and volt effect nuclear batteries) and secondary conversion nuclear batteries (such as radiation-photovoltaic effect nuclear batteries). Generally, the efficiency of primary conversion nuclear batteries is higher. For secondary conversion of nuclear batteries. The nuclear battery involved in the present invention belongs to the radiation energy nuclear battery in the primary conversion nuclear battery, that is, the radiation volt effect nuclear battery. Many electron-hole pairs are generated in the material, and the electron-hole pairs drift to the Schottky junction and the N-type side respectively under the built-in electric field of the Schottky junction of the nuclear battery, and a large amount of holes will be collected on the Schottky junction side. On the N-type side, a large number of electrons will be collected. Connect the Schottky contact electrode to the N electrode and add a load, and a current will be generated in the circuit. The Schottky contact electrode is equivalent to the positive pole of the battery, and the N electrode Equivalent to the negative terminal of the battery.

The issue of nuclear waste is one of the biggest obstacles to the further development of nuclear energy in the world today. It will be a very meaningful and valuable thing to make good use of these special garbage and turn waste into treasure. It will be possible to use nuclear waste to generate electricity , on the whole, will produce huge economic benefits and extensive social benefits.

Nuclear batteries have the advantages of small size, light weight, long life (determined by half-life), high reliability, and high energy density. Micro-nano electromechanical systems, mobile phones, laptops and other electronic products, and even electric vehicles have broad application prospects.

Contents of the invention

The purpose of the present invention is to provide a Schottky nuclear battery and its preparation method, which integrates isotopes and GaN Schottky junction semiconductor devices through a simple and mature preparation process, and then directly and efficiently converts isotope decay energy into electrical energy , to be used in industry and life.

Technical solution of the present invention is:

A kind of _Schottky type nuclear battery, it is characterized in that: comprise _Al2O3 substrate, n-type doped layer, the insulating layer of surface area less than n-type doped layer, Schottky contact electrode, n-type contact electrode and isotope layer; wherein the n-type doped layer is a silicon-doped GaN layer with a doping concentration between 1×10 ¹⁸ /cm ³ and 1×10 ¹⁹ /cm ³ , and is provided on the polished surface of the Al ₂ O ₃ substrate; insulation The layer is arranged on the surface of the n-type GaN doped layer; the Schottky contact electrode and the n-type contact electrode are respectively arranged on the surface of the GaN insulating layer and the n-type GaN doped layer; the pure β isotope layer is arranged on the Schottky contact on the electrode.

Further, the aforementioned Schottky-type nuclear battery, wherein the Al ₂ O ₃ substrate is β-phase sapphire, (001) crystal phase, with a thickness of 200-600 μm; the thickness of the n-type GaN doped layer is 1 ~3μm, where the Si doping is achieved by controlling the doping concentration between 1×10 ¹⁸ /cm ³ and 1×10 ¹⁹ /cm ³ and injecting SiH ₄ during MOCVD epitaxy; the thickness of the insulating layer is 15-100 μm; the n-type contact electrode is obtained by depositing Ti/Al/Ti/Au, wherein the thickness of Ti is 20-80 nm, the thickness of Al is 20-100 nm, the thickness of Ti is 20-200 nm, and the thickness of Au is 100-300 nm; the The Schottky contact electrode is obtained by depositing Ni/Au, wherein the thickness of Ni is 5-20nm; the thickness of Au is 10-25nm.

Furthermore, in the aforementioned Schottky-type nuclear battery, a GaN Schottky semiconductor device is respectively bonded to the upper and lower surfaces of the isotope layer.

Furthermore, in the Schottky-type nuclear battery mentioned above, a gallium nitride buffer layer may be further provided between the Al ₂ O ₃ substrate and the n-type GaN doped layer.

The above-mentioned Schottky type nuclear battery is prepared according to the following steps:

(1) Use MOCVD epitaxy method to grow n-type doped layer on the polished surface of Al ₂ O ₃ substrate, and control the doping concentration between 1×10 ¹⁸ /cm ³ and 1×10 ¹⁹ /cm ³ during MOCVD epitaxy SiH ₄ is introduced between them;

(2) using the HVPE epitaxy method to grow a GaN insulating layer on the n-type GaN doped layer;

(3) using semiconductor processing to obtain n-type doped layer steps on the surface of the n-type doped layer;

(4) Magnetron sputtering and deposition of Ti/Al/Ti/Au alloy on the exposed n-type GaN step surface to form an n-type contact electrode, and magnetron sputtering and deposition of a complete coverage of Ni on the surface of the GaN insulating layer /Au alloy to form a Schottky contact electrode;

(5) bonding the isotope layer on the surface of the Schottky contact electrode;

(6) Carry out nuclear battery packaging.

Further, in step (1), a gallium nitride buffer layer with a thickness of about 20 nm is epitaxially deposited on the polished surface of the Al ₂ O ₃ substrate.

The application of the technical scheme of the invention greatly improves the energy conversion efficiency and energy density (energy capacity) of the nuclear battery, prolongs the service life of the nuclear battery, and creates an effective way for nuclear waste to be turned into treasure and rationally utilized.

Description of drawings

Fig. 1 is the axial sectional schematic diagram of an embodiment of Schottky type nuclear battery of the present invention;

Fig. 2 is a schematic top view of the embodiment of the nuclear battery shown in Fig. 1;

Fig. 3 is a schematic axial cross-sectional view of another embodiment of the Schottky nuclear battery of the present invention.

Wherein, the meaning of each reference mark is:

1-Al ₂ O ₃ substrate, 2-n-type GaN doped layer, 3-insulating layer, 4-Schottky contact electrode, 5-n-type contact electrode, 6-isotope layer, 7-gallium nitride buffer layer .

Detailed ways

Below in conjunction with embodiment and accompanying drawing thereof, the present invention is described in further detail:

Embodiment one:

As shown in Fig. 1, the structural axial cross-sectional schematic diagram of an embodiment of a nuclear battery, first prepare an Al ₂ O ₃ disc, which can be purchased from the market to obtain a single-sided polished C-plane β-Al ₂ O ₃ substrate 1 with a diameter of 2 inches, Its thickness is 300 μm.

Then perform the Schottky wafer growth process: use MOCVD epitaxial growth equipment, first pass the Al ₂ O ₃ substrate 1 at 1100°C for about 2 minutes for ammonia nitriding, and then lower the temperature to 570°C and pass through trimethylgallium epitaxial gallium nitride (GaN) buffer layer 7 of about 20nm with ammonia gas, and then heated up to 1150°C to ^{pass trimethylgallium} , ammonia gas and Silane epitaxy of n-GaN doped layer 2 of about 2 μm, and then cool down to room temperature, take out the sample; put the sample into the HVPE system, raise the temperature to 1070 and pass in hydrogen chloride, ammonia gas and metal gallium to epitaxy 20 μm of GaN insulating layer 3, and then Cool down to room temperature and remove the sample.

Next, use ultraviolet lithography machine photolithography and ICP etching technology, obtain n-type steps on the surface of n-type GaN doped layer 2; Use magnetron sputtering technology to deposit Ti (20nm)/Al ( 20nm)/Ti(20nm)/Au(300nm) (i.e. Ti deposition 20nm, Al deposition 20nm, Ti deposition 20nm, Au deposition 300nm) n-type contact electrode 5 is prepared; Schottky contact electrode 4 is prepared by depositing Ni(5nm)/Au(10nm) by controlled sputtering technology; the flake nickel-63 isotope layer 6 is bonded on Schottky contact electrode 4; GaN Schottky is made by packaging nuclear battery.

Embodiment two:

First prepare an Al ₂ O ₃ wafer, which can be purchased from the market to obtain a single-sided polished 2-inch C-plane β-Al ₂ O ₃ substrate 1 with a thickness of 400 μm.

Then carry out the Schottky wafer growth process: use MOCVD epitaxial growth equipment, first raise the temperature to 1150°C, and pass trimethylgallium, ammonia and silane under the stable condition of controlling the silicon doping concentration at 1×10 ¹⁹ /cm ³ Epitaxial n-GaN doped layer 2 of about 2 μm, then lowered to room temperature, and took out the sample; put the sample into the HVPE system, heat up to 1070°C and pass in hydrogen chloride, ammonia gas and metal gallium to epitaxially 20 μm GaN insulating layer 3, and then Cool down to room temperature and remove the sample.

Next, use ultraviolet lithography machine photolithography and ICP etching technology, obtain n-type steps on the surface of n-type GaN doped layer 2; Use magnetron sputtering technology to deposit Ti (20nm)/Al ( 20nm)/Ti(20nm)/Au(300nm) (i.e. Ti deposition 20nm, Al deposition 20nm, Ti deposition 20nm, Au deposition 300nm) n-type contact electrode 5 is prepared; Ni(6nm)/Au(12nm) was deposited by controlled sputtering technology to prepare the Schottky contact electrode 4, thereby completing the preparation of the GaN Schottky semiconductor device.

Finally, a GaN Schottky semiconductor device prepared by the previous steps is respectively bonded on the upper and lower sides of the flaky promethium-147 isotope layer 7 (the isotope layer 6 is connected to the Schottky contact electrode of each GaN Schottky semiconductor device respectively. Bonding, as shown in Figure 3), the package is made of GaN Schottky nuclear battery. This will double the energy conversion efficiency.

Embodiment three:

The preparation method is the same as that of the above two examples. The battery structure can be either the single structure of Example 1 or the composite structure of Example 2. The difference of this example is that the isotope layer 6 can also use nuclear waste strontium-90 , can also realize the preparation of high-efficiency radiovoltaic effect nuclear battery.

It should be noted that in all implementations including the above three examples, the thickness of the Schottky contact electrode cannot exceed 40nm (calculated on one side for the situation described in Example 2), otherwise it will affect the nuclear battery. conversion efficiency. Moreover, different nuclear batteries can be integrated in a certain way to obtain higher voltage or current nuclear batteries to meet the needs of different situations.

From the point of view of expanding applications, photolithography technology is used to transfer the micro-energy layout (each nuclear cell is a circular surface with a diameter of 200 μm, as shown in Figure 2) to the wafer on a 2-inch GaN Schottky wafer, and CMP is used to Thinning and polishing Al ₂ O ₃ to 100 μm, using a laser scribing machine to cut into squares with a side length of 220×220 μm, and then using a splitter to split the above squares into individual micro-energy nuclear battery devices, which can be compared with the effect The MEMS are bonded or integrated together to provide energy to the MEMS.

Due to the use of the above-mentioned technical solutions, the present invention has the following advantages compared with the prior art:

1. In the prior art, the nuclear batteries put into use are mainly thermoelectric effect nuclear batteries, which are used on spacecraft. Thermoelectric efficiency If nuclear batteries want to obtain higher efficiency, they must have a certain power, so they are not suitable for low-power and micro-system power supply places. With the rapid development of MEMS and NEMS, the demand for micro-energy will also increase rapidly, which is also an important application field of the present invention. Because the nuclear battery of the present invention can be manufactured with a small volume and a simple structure, the power of a single battery can be between 1 μW and 5W. In addition, the isotopes used in the thermoelectric effect nuclear battery are Pu-238 and Po-210, which are highly toxic and unsafe to use; and the nuclear battery designed in the present invention can use nontoxic isotopes such as tritium, Ni, Pm, etc. Safe use; moreover, the theoretical conversion efficiency of the thermoelectric effect nuclear battery is far lower than that of the radiovoltaic effect nuclear battery of the present invention.

2. Because what the GaN Schottky nuclear battery of the present invention uses is the most mature third-generation semiconductor material GaN, it has wider bandwidth than the Si material in the prior art (Si nuclear battery), and better resistance Radiation and temperature resistance properties. Therefore, the efficiency of the GaN Schottky nuclear battery of the present invention is much higher than that of the Si nuclear battery (the maximum conversion efficiency of Si is 15%, while the maximum conversion efficiency of GaN Schottky can be as high as 30%).

To sum up, the Schottky nuclear battery and the preparation method thereof of the present invention provide a feasible technical solution. The energy conversion efficiency and energy density (energy capacity) of the nuclear battery are greatly improved, the service life of the nuclear battery is prolonged, and an effective way is created for turning nuclear waste into treasure and rationally utilizing it. The above are only some specific application examples of the present invention, and do not constitute any limitation to the protection scope of the present invention. All technical solutions formed by equivalent transformation or equivalent replacement fall within the protection scope of the present invention.

Claims (8)

1. Schottky-type nuclear battery, characterized in that: the surface of the _Al2O3 substrate at the bottom of the battery is provided with an n-type doped layer, and the surface of _the n-type doped layer is provided with an intrinsic GaN insulating layer whose surface area is smaller than that of the n-type doped layer layer, the Schottky contact electrode and the n-type contact electrode are respectively arranged on the surface of the corresponding insulating layer and the n-type doped layer, and a pure β isotope layer with the same surface area is provided on the surface of the Schottky contact electrode, wherein the n-type doped The impurity layer is a GaN layer doped with silicon with a doping concentration ranging from 1×10 ¹⁸ /cm ³ to 1×10 ¹⁹ /cm ³ , and the thickness of the insulating layer is 15˜100 μm. 2. The Schottky-type nuclear battery according to claim 1, characterized in that: the pure β isotope layer is nickel-63, promethium-147 or strontium-90. 3. The Schottky-type nuclear battery according to claim 1, characterized in that: a GaN buffer layer is provided between the Al ₂ O ₃ substrate and the n-type doped layer. 4. The Schottky-type nuclear battery according to claim 3, wherein the n-type doped layer has a thickness of 1-3 μm. 5. The Schottky-type nuclear battery according to claim 1, characterized in that: the thickness of the Schottky contact electrode is 15-30 nm. 6 . The Schottky-type nuclear battery according to claim 1 , characterized in that: the surface area of the isotope layer is consistent with the surface area of the Schottky contact electrode, and its value is between 0.01-1800mm ² . 7. A method for preparing the Schottky nuclear battery as claimed in claim 1, characterized in that: comprising the steps of: (1) Use MOCVD epitaxy method to grow n-type doped layer on the polished surface of Al ₂ O ₃ substrate, and control the doping concentration between 1×10 ¹⁸ /cm ³ and 1×10 ¹⁹ /cm ³ during MOCVD epitaxy SiH ₄ is introduced between them; (2) Using the HVPE epitaxy method to grow a GaN insulating layer with a thickness of 15-100 μm on the n-type GaN doped layer; (3) using semiconductor processing to obtain n-type doped layer steps on the surface of the n-type doped layer; (4) Magnetron sputtering and deposition of Ti/Al/Ti/Au alloy on the exposed n-type GaN step surface to form an n-type contact electrode, and magnetron sputtering and deposition of a complete coverage of Ni on the surface of the GaN insulating layer /Au alloy to form a Schottky contact electrode; (5) bonding the isotope layer on the surface of the Schottky contact electrode; (6) Carry out nuclear battery packaging. 8. A kind of method for preparing Schottky type nuclear battery according to claim 7, is characterized in that: in step (1) on the polished surface of described Al ₂ O ₃ substrate earlier epitaxial gallium nitride buffer layer.

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