generator system

Abstract

1. A generator system comprising a radionuclide material (7) and a sandwich structure comprising a layer of n-type semiconductor material (5), a layer of intrinsic n-type semiconductor material (4), a layer of p-type semiconductor material (3), metal electrodes (2, 6) one electrode 6 in direct contact with the n-type semiconductor material and the other electrode 2 in contact with the p-type semiconductor material forming a metal-semiconductor junction therebetween, whereby radioactive radiation received from the radionuclide material is converted to electrical energy at the metal-semiconductor junction, and electrical contacts connected to the electrodes that facilitate the flow of the electrical energy when connected to a load.

Description

[Technical Field]

[0001] The present invention relates to the field of power generation, and in particular to electrical energy generated from energy from radioactive emissions. Practical applications of the present invention can be found in the formation of power cell devices and in other applications. [Background technology]

[0002] A power cell provides a self-contained source of electrical energy for driving an external load. A common example of a power cell is an electrochemical battery. Electrochemical batteries are effective in providing power needs over a period of time at a relatively low cost, but the limiting factor is the available energy, which is defined by the type and weight of materials. Due to limitations in the energy storage and energy density of electrochemical batteries relative to their mass, various attempts have been made to produce alternative power cells, such as batteries powered by radioisotopes, which have a higher theoretical limit for energy density.

[0003] There are several different types of radioisotope-powered batteries. One such type is the radiant heat generator (RTG), which uses the heat generated during the decay of radioactive material to generate electrical energy. These devices have low efficiency in converting thermal energy to electrical energy. Therefore, RTGs are generally used with very high-energy radioisotopes, such as Pu-238, to generate electrical power, and typically require substantial shielding. Furthermore, their power output is low.

[0004] Another type of radioisotope-powered power cell is an indirect conversion device that uses a radioisotope, a luminescent material, and a photovoltaic cell. Decay particles emitted by the radioisotope excite the luminescent material. The light emitted by the luminescent material is absorbed by the photovoltaic cell to generate electricity. This type of cell generally has low efficiency due to the two-step conversion and a relatively short lifespan due to radiation damage to the luminescent material caused by the radiation.

[0005] Another example of a radioisotope-powered power cell is a direct conversion device that uses a radioisotope and a semiconductor material. Conventional semiconductors have limited utility in this application because they suffer collateral radiation damage from the decay products of the radioisotope. In particular, incident high-energy beta particles create defects in the semiconductor, scattering and trapping the generated charge carriers. This damage accumulates, reducing the cell's performance over time.

[0006] U.S. Patent No. 5,999,623 discloses a solid-state nuclear battery that includes a relatively high-energy radiation source with accompanying heat generation and a bulk crystalline semiconductor, such as AlGaAs, that is characterized by defects that develop in response to the radioisotope. The materials are selected so that radiation damage can be repaired by annealing at the battery's high operating temperature. This device suffers from low efficiency, requiring the use of a high-energy radiation source, and also from the need for high operating temperatures to function.

[0007] U.S. Patent No. 5,999,623 teaches a solid-state radioisotope-powered semiconductor battery that includes a substrate of a crystalline semiconductor material, such as GalnAsP. The battery preferably uses a radioisotope that emits only low-energy particles to minimize degradation of the semiconductor material, with the goal of maximizing lifetime. The effect of using a low-energy source material is a lower maximum power output.

[0008] Another such device is disclosed in U.S. Patent No. 6,277,999, which describes a beta cell incorporating an icosahedral boride compound, a beta radiation source, and a means for transmitting electrical energy to an external load. The production of boron arsenide and boron phosphide is expensive, resulting in high costs for manufacturing these types of devices. Furthermore, the manufacture of such devices poses high health, safety, and environmental risks associated with handling arsenide and phosphide materials.

[0009] Patent document 4 (Kinetic Energy Australia Pty Ltd) discloses a radioisotope generator that uses ZnO as a semiconductor, with energy generated at the metal-semiconductor junction. This allows for good durability and relatively high power production. However, the disclosed arrangement is particularly effective for radioisotope sources that emit primarily beta particles, but is less effective for x-ray and gamma ray emitters. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 5,260,621 [Patent Document 2] U.S. Patent No. 5,859,484 [Patent Document 3] U.S. Patent No. 6,479,919 [Patent Document 4] International Publication No. 2016 / 074044 Summary of the Invention [Problem to be solved by the invention]

[0011] It is an object of the present invention to provide a radioisotope power cell that provides an improved balance between durability and power output, particularly for x-ray and gamma ray emitting radiation sources. [Means for solving the problem]

[0012] In its broadest form, the present invention provides a generator having a multi-layer structure including a radionuclide material, an n-type semiconductor layer, an intrinsic n-type material, a p-type material layer, and a metal electrode.

[0013] According to one aspect, the present invention provides a method for manufacturing a semiconductor device comprising: A generator system is provided that includes a radionuclide material and a sandwich structure, the sandwich structure comprising: a layer of n-type semiconductor material; a layer of intrinsic n-type semiconductor material; a layer of p-type semiconductor material; metal electrodes, one electrode in direct contact with the n-type semiconductor material and the other electrode in contact with the p-type semiconductor material, forming a metal-semiconductor junction therebetween, and wherein radioactive radiation received from the radionuclide material is converted into electrical energy at the metal-semiconductor junction; electrical contacts connected to the electrodes that facilitate the flow of electrical energy when connected to a load; Includes:

[0014] In a preferred form, the generator includes multiple sets of layers to increase the effective capture of the radionuclide energy. In a preferred form, the predominant radiation from the radionuclide is in the form of x-ray and / or gamma ray radiation. [Effects of the Invention]

[0015] In preferred implementations, the present invention allows for the efficient generation of energy from suitable x-ray and / or gamma-ray emitting radioisotopes, and also provides a structure that can continue to operate effectively for extended periods of time despite the constant irradiation inherent in such devices. [Brief explanation of the drawings]

[0016] Exemplary embodiments of the invention are described below with reference to the drawings.

[0017] [Figure 1] 1 is a cross-sectional view of an implementation of a single generating structure according to the present invention. [Figure 2] 1 is a cross-sectional view of an embodiment of a multi-layer generating structure according to the present invention. [Figure 3] 10 is a graph showing voltage performance in a first test example. [Figure 4] 10 is a graph showing the current generated in the second test example. [Figure 5] 10 is a graph showing the current generated in a third test example. [Figure 6] FIG. 1 is a cross-sectional view of a single set of gamma generating structures. [Figure 7] 6 is a cross-sectional view of an array of the set according to FIG. 5. [Figure 8] FIG. 1 is an external view of an embodiment of a practical system. [Figure 9] FIG. 8 is a cross-sectional view of the design of FIG. 7. [Figure 10] FIG. 8 is a cross-sectional view of the design of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described primarily with reference to specific exemplary embodiments. It will be understood that the principles of the present invention may be implemented using variations of the features of the specific implementations shown and described. The nature of the present invention thus allows for many possible implementations using the principles of the present invention, such as different numbers of layers, additional layers, alternative radioisotopes (or combinations thereof), etc.

[0019] The present invention shares several principles with the invention described in U.S. Patent No. 6,279,949, filed by the present inventors, the disclosure of which is incorporated herein by reference. In particular, U.S. Patent No. 6,279,949 teaches the importance and advantages of using ZnO as an intrinsic n-type semiconductor material.

[0020] However, the present invention is primarily concerned with the generation of electrical energy using radioisotopes that produce x-rays and gamma rays, in particular (although not excluding other radioisotopes).

[0021] The mechanism or mode of action of beta particles when impacting our semiconductor materials is very different from the mechanism or mode of action of x-ray and gamma ray photons. All things being equal, beta collisions at typical energies have a much greater effect on atomic structure than x-ray and gamma ray photons. Beta particles typically remove electrons and atoms and excite electrons, while x-ray and gamma ray photons are less likely to remove atoms but will remove electrons and excite electrons.

[0022] The inventors have observed that gammavoltaic structures function in some respects in much the same way as standard photovoltaic materials. However, the energy of individual photons shifts dramatically from a few eV with infrared, visible, or ultraviolet radiation to keV and MeV with x-ray and gamma-ray photons. Under such conditions, typical photovoltaic semiconductor structures degrade and fail relatively quickly due to radiation-induced damage.

[0023] Because x-ray photons interact less with gamma-ray photons than beta particles, i.e., the radiation cross section is smaller, practice of the present invention seeks to increase the energy captured by adding p-type material to the structure. It has also been observed by the inventors that multiple layers of such sandwich structures are particularly advantageous.

[0024] Zinc oxide is an intrinsic n-type semiconductor, and at equilibrium the material exhibits n-type semiconducting properties. Aluminum zinc oxide (AlZnO) is an n-type semiconductor, similar to zinc oxide, except that aluminum enhances the n-type properties of the semiconductor. Aluminum is added as a dopant, preferably in the range of about 0.5% to about 10%. The thickness of the ZnO layer must be adjusted depending on the level of dopant in the AlZnO, as further described below.

[0025] It is desirable to have a layer of intrinsic ZnO between the n-type and p-type materials for several reasons. It provides an adjustable built-in voltage (Vb) for the structure. It also acts as a barrier to prevent migration of dopant material from n-type to p-type and vice versa. If such migration occurs, it can interfere with the desired solid-state structure and degrade the performance of the structure.

[0026] FIG. 1 shows a power-generating structure according to one embodiment of the present invention. The radioisotope material 7 is centrally located. On either side are layers for receiving radiation from the radioisotope, preferably gamma and / or x-rays. In this embodiment, these are a top contact 6, an n-type layer 5, an intrinsic n-type layer 4, a p-type layer 3, a bottom contact 2, and a non-conductive substrate 1. The remainder of the structure is formed from a suitable framework material for disposing the substrate and radioisotope. The framework material can be divided into a "structurally integral" structure, typically a steel or aluminum sheet, angle bar, rod, or tube, and a "racking system," which is a non-conductive material, either ceramic or polymeric, including, by way of example, Macor or polystyrene.

[0027] The top and bottom contacts are formed from a metal such as copper, aluminum, a copper-aluminum alloy, a copper-iron-aluminum alloy, gold, silver, nickel, cobalt, tin, or a nickel-vanadium alloy.

[0028] The n-type layer may be formed from any suitable material, preferably aluminum zinc oxide, with the Al being up to 10%, but preferably in an atomic ratio of about 98 Zn to 2 Al.

[0029] The intrinsic n-type material is preferably ZnO.

[0030] A wide variety of p-type materials are possible, including nickel vanadium oxide (93-7 Ni-V), nickel oxide, nickel cobalt oxide (98-2 Ni-Co), cobalt oxide, cobalt copper oxide (98-2 Co-Cu), nickel copper oxide (98-2 Ni-Cu), copper oxide, cobalt nickel oxide (98-2 Co-Ni), nickel chromium oxide (90-10 Ni-Cr), nickel platinum oxide (98-2 Ni-Pt), copper chromium oxide (99-1 Cu-Cr), cobalt platinum oxide (98-2 Co-Pt), and cobalt titanium oxide (96-4 Co-Ti). To avoid misunderstanding, all these ratios are expressed as atoms per 100, not as weight percent. In principle, other salts with alternative anions, such as nitrides, could be used, but the material should preferably be selected so that decomposition products are not harmful or destructive to the structure. Given the intended radiation environment, the level of conversion of the anion to the parent element is expected to be low, e.g., chlorides are not recommended and oxides are preferred.

[0031] The substrate may be formed from any suitable radiation-curable material, for example, silicon, quartz, sapphire, float glass, Schott Borofloat glass, phosphate glass, calcium fluoride.

[0032] Radioisotopic materials may be a single isotope, a mixture of isotopes, or even a mixture of radioactive and stable materials. Single elements are preferred because they simplify ultimate disposal and waste management. Isotopes that may be used in embodiments of the present invention include cesium-137, cobalt-60, europium-152, gadolinium-153, germanium, iridium-192, iron-55, krypton-85, ruthenium-106, selenium-75, sodium-22, strontium-90, and ytterbium-169. These isotopes may be intentionally produced for use in embodiments of the present invention or may be by-products or waste products from other processes. Over time, as radioactive decay occurs, the material will have a mixture of different isotopes as a result of the decay process, and it will be understood that additional isotopic decay modes of these isotopes may also be present within the material.

[0033] The invention can also be deployed to generate power from "waste" x-rays or gamma rays from other processes, in which case the x-ray or gamma ray source would likely be located to one side rather than in the center.

[0034] The thickness of each layer will vary depending on the particular material selected and the overall system geometry. Typical thicknesses are as follows: · Substrate 0.25mm~10mm, Bottom metal contact 0.2~5μm, ·P-type layer 0.2~5μm, ·Intrinsic layer 0.2~2μm, ·N-type layer 0.2~5μm, Upper metal contact 0.2~5μm.

[0035] The inventors have determined that, in general, increasing the percentage of dopant in an n-type layer requires increasing the thickness of the intrinsic ZnO layer, and similarly, decreasing the dopant requires decreasing the thickness of the ZnO layer. This is also true for p-type materials. The appropriate thicknesses of the different layers are material-specific, and the interrelationship between the dopant and the layer material is an important variable. It will be understood that appropriate trials will be required for the layers selected in any design to determine the optimal thickness of each layer, depending on the materials selected. Layer preparation is preferably performed by magnetron sputtering (DC and / or RF).

[0036] Figure 2 shows how the structure can be expanded to provide multiple layers to allow interaction with gamma and x-ray photons. N layers of material can be placed in both directions away from the radioisotope. It will be appreciated that adding layers provides additional opportunities for generating electrical power from the same radiation source. In effect, the radiation cross section of the structure increases.

[0037] Figure 6 shows a cartridge 20 having 50 layers of power generating structure 10 for use as a component of a larger system. In this structure, there is a sequence of structures as in Figure 2, but excluding the radioisotope layer 7. Instead of four repetitions of layers as shown in Figure 2, in this alternative implementation there are 50 repetitions of the sequence of layers.

[0038] 7 to 10 show a generation structure 30 in which twelve units of the cartridge 20 of FIG. 6 are arranged in two layers of six units, and radioactive isotopes are inserted as sealed sources into three openings 32, 32A, 32B.

[0039] Figure 8 is an external view of the power generation structure 30. The isotope loader container 35 at the top allows the radioactive source to be reliably and safely loaded into the power generation structure 30. The loader may be moved into the appropriate position to load the cores into each opening. This can be seen more clearly in Figures 9 and 10. The isotope loader container 35 is used to safely and easily transfer the isotope cores from the shipping container to the power unit. Once the isotope is loaded, the power cell unit structure is sealed and the loader structure is removed and therefore available for use in loading another unit.

[0040] It will be appreciated that pure beta-emitting isotopes require thin shielding or containment, while gamma and x-ray radiation require more substantial construction. The larger power generation system shown in Figures 9 and 10 incorporates appropriate shielding for use of the system as a stand-alone power generation unit. The shielding requires the appropriate choice and thickness of high density material such as depleted uranium, tungsten, lead, steel or iron, or a less dense material with appropriate thickness / width such as concrete or water. The power generation unit 30 shown in Figure 9 has a central 1 m 3 The generator unit 30 incorporates 300 mm of steel / iron containment around a walled cavity. As mentioned above, the cavity holds multiple cartridges 10 and three radioisotope loading channels. As shown in Figure 10, the generator unit 30 also includes a gate track 33, a gamma gate 36, a cover plate 37, a bearing cartridge 38, and a ball screw 39.

[0041] Alternative implementations may use different shielding materials, with corresponding changes in size and construction. For example, in the embodiment of Figure 9, the steel / iron containment may be replaced with a 1.5m thick concrete outer casing, or water with a head height of 4m to 5m. A further embodiment of Figure 9 may use an internal 1m 3 The containment is removed from around the walled cavity and the containment is incorporated into a separate structure or building (wall), the preferred material of the structure being concrete 1.5m thick.

[0042] The materials in the above examples have demonstrated radiation resistance up to 15 megarads (150,000 Gray).

[0043] An embodiment of the present invention provides a power generation system that uses n-type semiconductor material with metal electrodes in contact with the sandwich of semiconductor materials and exposes the arrangement to radiation from radionuclide materials. The radioactive radiation is converted to electrical energy at the metal-semiconductor junctions formed between the electrodes and the n-type and p-type semiconductor materials. It is important that there be a potential difference between the electrodes to allow the generated electrical energy to flow. Therefore, there must be a significant difference in the metal-to-semiconductor contact area between the electrodes so that a larger charge is generated on one electrode compared to the other. The electrode with the larger charge accumulation effectively becomes the negative terminal, and the other electrode becomes the positive terminal.

[0044] To maximize power generation in radioisotope power cells, it is desirable to use relatively high energy levels of the radiation source and high activity densities, however most semiconductor materials cannot withstand such high energy levels and suffer structural degradation from exposure.

[0045] In practical experiments, thin films of zinc oxide are formed on substrates by reactive DC magnetron sputtering or electrochemical vapor deposition, with the deposited films having surfaces ranging from 5 cm x 5 cm to 250 cm x 250 cm. Current deposition techniques allow for larger panels, e.g., 1 m 2 It is now possible to produce panels exceeding this limit.

[0046] The substrate consisted of a first layer of glass. The substrate further consisted of a layer of doped metal oxide material, which formed the surface onto which the zinc oxide was deposited. The metal oxide can be either p-type or n-type in nature, thereby providing either n-type or p-type semiconductor material adjacent each plane of the zinc oxide thin film, with appropriate doping.

[0047] Many metal materials and metal alloys were tested for their suitability as electrodes: aluminum, cobalt, cobalt-copper, cobalt-nickel, cobalt-platinum, cobalt-titanium, copper, copper-chromium, nickel, nickel-cobalt, nickel-copper, nickel-chromium, nickel-platinum, nickel-vanadium, and zinc. Additionally, different electrode configurations were investigated: in one configuration, the electrode covered the entire surface of the zinc oxide layer; in a second configuration, a comb-like or finger-like grid formation was used on the zinc oxide surface. Typical thicknesses of the metal electrode materials ranged from 100 to 1000 nm, with 250 nm being preferred. The metal electrodes in this example were deposited using sputtering techniques.

[0048] Test results have found that aluminum, cobalt, cobalt-copper, cobalt-nickel, cobalt-platinum, cobalt-titanium, copper, copper-chromium, nickel, nickel-cobalt, nickel-cobalt, nickel-copper, nickel-chromium, nickel-platinum, nickel-vanadium, and zinc all produce linear and symmetrical current-voltage curves at the metal-semiconductor junction, indicating a desirable degree of ohmic contact between these metals and the respective n-type or p-type semiconductor materials.

[0049] Negligible differences in results were observed for the different configurations, suggesting that the comb-grid configuration, which uses less metal, is a viable option. It will be understood that other geometries and configurations are also contemplated within the scope of the present invention.

[0050] While any suitable isotope can be used, currently preferred materials are sealed sources containing cobalt-60, cesium-137, or europium-152. Sealed sources of these materials come in many different forms and shapes, for example, rods, pencils, or pucks. In principle, the invention can be practiced using sealed sources of any shape, but the preferred sealed source form for use in the configuration of Figure 9 is a rod or pencil. Our preferred single source activity has a maximum activity of 15,000 curies, with 10,000 curies being easier to transport and handle.

[0051] Next, a specific example of a power supply device using a generator system will be described below. It will be understood that the components in an actual system may have many different dimensions, may have single or multiple layers, or may be formed as a cartridge of the above-mentioned 50 or more layers. The substrate (sandwich) may be of any suitable area, for example 75 cm 2 ~62500cm 2 has been found to be appropriate.

[0052] It will be appreciated that structures having multiple layers of radionuclide may be used, with multiple sandwich structures being added to provide the desired power level. It will also be appreciated that while the structures described are generally square in shape, the structures may be of any desired shape and may be curved in a preferred implementation, provided that appropriate spacing can be maintained.

[0053] Tests were conducted to evaluate the output performance and radiation exposure stability of an example system according to the present invention. The structure for this test was approximately 75 cm 2 The wafers were 100 mm in diameter, providing a surface area of ​​100 μm. The structure used 250 μm of metal electrodes, 1.0 μm of doped metal oxides (n-type and p-type), and 0.5 μm of ZnO. Two separate arrays, identified as Co7 and Co9, were tested in various configurations, both separately and connected together in series and parallel.

[0054] In one experiment, Co7 and Co9 were connected and exposed to a cobalt-60 source for 36 hours, delivering a dose rate of approximately 15.12 megagrays (MGy) of gamma radiation during the performance test period. The cobalt-60 source used delivered an average gamma dose of 70 grays (Gy) / minute (average 420,000 rads / hour), or 1.2 x 10 photons / second (each photon having an average energy of >1.1 MeV) into the test chamber.

[0055] The electrical performance of the device was relatively stable and did not change during the test period. The internal voltage before and after irradiation was about 20 mV, and the average generated voltage under irradiation, V IRR was about 100 mV. Figure 3 shows the voltage performance in the first test example. The measured average current I IRR is 354mA, The measured average voltage V IRR is 100mV, The average power generated, P IRR is 35.4mW, Maximum theoretical power output P Max is calculated as 3.304W, Conversion efficiency = P IRR / P Max =35.4 / 3304=1.07%.

[0056] Prolonged exposure to such high gamma fields typically irreversibly damages semiconductor materials. However, in this test, the device was "radiation hard" at 150 kGy (15 MRad). The electrical output remained substantially unchanged during and after exposure.

[0057] The reference is "Radiation Hardness Test for Gamma Probe; U. Wengrowicz, R. Seif, J. Nir, E. Gonen and D. Tirosh; Nuclear Research Center - Negev, PO Box 9001, Beer Sheva 84190, Israel."

[0058] In separate tests, Co7 and Co9 devices were irradiated with x-rays at photon energies / photon fluxes of 100 kV / 4.5 mA, 100 kV / 9 mA, and 200 kV / 4.5 mA at a distance of approximately 10 cm.

[0059] Figure 4 shows that the x-ray radiation impinging on the wafer is 3.446 mJ·s -1 Figure 1 shows IV plots of Co7 and Co9 under both "dark" and x-ray (200 kV / 4.5 mA) irradiation. Both semiconductor wafers showed a strong response to x-ray photons. Co7 had negligible leakage current under both forward and reverse bias. Co9 had leakage current above +3v under dark conditions. At 5v, Co7 produced approximately 30 mA of current. At 5v, Co9 produced approximately 15 mA of current.

[0060] Across multiple individual semiconductor wafers, at a distance of 5 cm, it was observed that doubling the voltage from 100 kV to 200 kV doubled the voltage and increased the current generated by the semiconductor by a factor of 1.9. Thus, doubling the photon voltage increased the power by a factor of 3.8. This increase is slightly less than the calculated difference of about 4.1.

[0061] Across multiple individual semiconductor wafers, at a distance of 5 cm, it was observed that doubling the current from 4.5 mA to 9 mA resulted in a 1.2-fold increase in voltage, resulting in a current 1.5 times that produced by the semiconductor. Thus, doubling the photon flux resulted in a 1.8-fold increase in power, slightly less than the calculated difference of about 2x.

[0062] It was observed that adding a semiconductor layer increases the power output, thus achieving higher voltages and currents, which are greater than the sum of the individual cell performance tests.

[0063] The series and parallel configuration of layers helps to stabilize the output current and voltage of the semiconductor array.

[0064] In separate tests, Co7 and Co9 devices were irradiated with gamma photons from cobalt-60, with the activity of the radioisotope being approximately 535 TBq and the measured dose rate being 76.3 Gy / min. The distance from the radioisotope to the semiconductor wafer was measured and estimated to be 10 cm. The gamma radiation striking the array was 1.83 × 10-1 J·s -1 is.

[0065] Figure 5 shows a graph of the parallel array consisting of Co7 and Co9 in both the "dark" and gamma photon irradiation. As shown in the graph, the parallel array exhibited a strong response to x-ray photons. The leakage current of the array was negligible. At 5v, the array produced a current of approximately 2.5 mA.

[0066] It has been observed that adding more semiconductor layers increases the overall power output, and that configuring layers in series and parallel helps to stabilize the output current and voltage of the semiconductor array.

Claims

1. 1. A generator system including a radionuclide material and a sandwich structure, said sandwich structure comprising: a layer of n-type semiconductor material; a layer of intrinsic n-type semiconductor material; a layer of p-type semiconductor material; metal electrodes, one electrode in direct contact with the n-type semiconductor material and the other electrode in contact with the p-type semiconductor material, forming a metal-semiconductor junction therebetween, and wherein radioactive radiation received from the radionuclide material is converted to electrical energy at the metal-semiconductor junction; electrical contacts connected to the electrodes that facilitate the flow of electrical energy when connected to a load; a generator system,

2. 10. The generator system of claim 1, wherein the generator system includes multiple repetitions of the sandwich structure such that the radiation emission from the radionuclide material passes through the multiple repetitions of the metal-semiconductor junction.

3. 3. The generator system according to claim 1 or claim 2, wherein the intrinsic n-type semiconductor material is zinc oxide.

4. 3. The generator system according to claim 1 or claim 2, wherein the n-type semiconductor material is aluminum zinc oxide.

5. 5. The generator system of claim 4, wherein the aluminum zinc oxide has an atomic ratio of 98 Zn to 2 Al.

6. 3. The generator system of claim 2, wherein ten or more iterations of the sandwich structure are arranged in a unit, and a plurality of such units are arranged within a shielded cavity, the cavity also containing one or more sections of radioactive material.

7. The generator system of claim 1 , wherein the sandwich structure is formed on a substrate.

8. The generator system of claim 3, wherein the thin layer of zinc oxide has a thickness of 150 to 1500 nm.

9. 9. The generator system of claim 8, wherein the thin layer of zinc oxide has a thickness of 1250 nm or less.

10. A power supply device comprising a housing enclosing the generator system of claim 1 or claim 2.

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