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. The present invention finds practical application in the formation of power cell devices, as well as in other applications. [Background technology]

[0002] A power cell provides a self-contained source of electrical energy to drive an external load. A common example of a power cell is the 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, defined by the type of material and weight. Due to limitations in the energy storage and energy density of electrochemical batteries with respect to their mass, various attempts have been made to produce alternative power cells, such as batteries powered by radioisotopes, due to the higher theoretical limit of 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. Thus, RTGs are generally used with very high-energy radioisotopes, such as Pu-238, to generate the power source, and typically require substantial shielding. Additionally, the 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. Light emitted by the luminescent material is absorbed by a 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 the luminescent material being subject to radiation damage from 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 use 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 performance of the cell over time.

[0006] US Patent No. 5,399,633 discloses a solid-state nuclear battery comprising a relatively high-energy radiation source with associated heat generation and a bulk crystalline semiconductor such as AlGaAs that is characterized by the generation of defects in response to the radioisotope. The materials are selected such that radiation damage is repaired by annealing at the high operating temperature of the battery. The device suffers from low efficiency, necessitating the use of a high-energy radiation source, and also from the need for high operating temperatures in order to function.

[0007] US Patent No. 5,399,633 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] A further such device is disclosed in US Pat. No. 5,399,633, which describes a beta cell incorporating an icosahedral boride compound, a beta radiation source, and a means for transferring electrical energy to an external load. The production of boron arsenide and boron phosphide is expensive, which increases the cost of producing these types of devices. Furthermore, the manufacture of such devices involves high health, safety, and environmental risks associated with handling arsenide and phosphide materials.

[0009] US Patent No. 5,399,633 (Kinetic Energy Australia Pty Ltd) discloses a radioisotope generator using ZnO as the semiconductor, with energy being 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. Pat. No. 5,260,621 [Patent Document 2] U.S. Pat. No. 5,859,484 [Patent Document 3] U.S. Pat. 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 a broad 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 producing 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 radiation 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 the 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's energy. In a preferred form, the predominant radiation from the radionuclide is in the form of x-ray and / or gamma ray radiation. Effect of the Invention

[0015] In a preferred implementation, 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 capable of continuing effective operation for extended periods of time despite the constant irradiation inherent in such devices. [Brief description 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. [Diagram 2] 1 is a cross-sectional view of an embodiment of a multi-layer generating structure according to the present invention. [Diagram 3] 13 is a graph showing voltage performance in a first test example. [Figure 4] 13 is a graph showing a current generated in a second test example. [Diagram 5] 13 is a graph showing a current generated in a third test example. [Figure 6] FIG. 2 is a cross-sectional view of a single set of gamma generating structures. [Figure 7] FIG. 6 is a cross-sectional view of an array of the set according to FIG. [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. [Figure 10] FIG. 8 is a cross-sectional view of the design of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 the envisioning of many possible implementations using the principles of the present invention, e.g., number of layers, additional layers, alternative radioisotopes (or combinations thereof), etc.

[0019] The present invention uses several principles in common with the invention described in U.S. Patent No. 6,393,363, the disclosure of which is incorporated herein by reference, and which teaches in particular 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 to the exclusion of 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, whereas 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 a manner much like standard photovoltaic materials in some respects. However, the energy of individual photons shifts dramatically from a few eV with infrared, visible, or ultraviolet light, 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 have a lower interaction with gamma-ray photons compared to beta particles, in other words, the radiation cross section is smaller, the 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 inherent 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, but the 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 described further below.

[0025] It is preferable 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 were to occur, it would interfere with the desired solid-state structure and degrade the performance of the structure.

[0026] Figure 1 shows a power generating structure according to one embodiment of the present invention. The radioisotope material 7 is placed in the middle. On either side, layers are placed to receive radiation from the radioisotope, preferably gamma and / or x-rays. In this embodiment, these are the top contact 6, the n-type layer 5, the intrinsic n-type layer 4, the p-type layer 3, the bottom contact 2, and the non-conductive substrate 1. The remainder of the structure is formed from a suitable scaffolding material on which to place the substrate and the radioisotope. The structural scaffolding material can be divided into "structurally integral", which are typically steel or aluminium sheets, angle bars, rods or tubes, and "racking system", which are non-conductive materials, either ceramic or polymeric, including Macor or polystyrene as examples.

[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 Al being up to 10% but preferably having an atomic ratio of about 98 Zn to 2 Al.

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

[0030] As p-type materials a wide variety of materials are possible, for example 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), cobalt titanium oxide (96-4 Co-Ti). To avoid misunderstandings, all these ratios are expressed as the number of atoms in 100, and not as weight percentages. In principle, other salts with alternative anions can be used, for example nitrides, but the choice of material is preferably such that the decomposition products are not harmful or destructive to the structure. Given the intended radiation environment, the level of conversion of the anions to the parent elements 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] The radioisotopic material may be a single isotope, a mixture of isotopes, or even a mixture of radioactive and stable materials. A single element is preferred because it simplifies eventual disposal and waste management. Isotopes that may be used in embodiments of the 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 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, so 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, Top metal contact 0.2~5μm.

[0035] The inventors have determined that, in general, increasing the percentage of dopant in the n-type layer requires an increase in the thickness of the intrinsic ZnO layer, and similarly, decreasing the dopant requires a decrease in 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 appreciated 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. The preparation of the layers is preferably performed by magnetron sputtering (DC and / or RF).

[0036] FIG. 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 is increased.

[0037] Figure 6 shows a cartridge 20 having 50 layers of the power generation 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] 7-10 show a production structure 30 in which twelve units of the cartridge 20 of FIG. 6 are arranged in two layers of six units and radioisotopes are inserted as sealed sources in three openings 32, 32A, 32B.

[0039] Figure 8 is an external view of the power generation structure 30. The isotope loader vessel 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 vessel 35 is used to safely and easily transfer the isotope cores from the transport vessel to the power unit. Once the isotope is loaded, the power cell unit structure is sealed and the loader structure is removed and thus available to be used to load 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 generating system shown in Figures 9 and 10 incorporates appropriate shielding for use of the system as a stand alone generating unit. Shielding requires the appropriate selection 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 generating unit 30 shown in Figure 9 has a central 1m 3 The generator unit 30 incorporates 300 mm of steel / iron containment around a walled cavity. As mentioned above, the cavity holds a number of cartridges 10 and three radioisotope loading channels. As shown in Figure 10, the generator unit 30 also has 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 FIG. 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 FIG. 9 may use an internal 1m 3 This involves removing the containment from around the walled cavity and incorporating the containment into a separate structure or building (wall), the preferred material of construction being concrete 1.5m thick.

[0042] The materials in the above examples have been shown to be radiation resistant 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 a sandwich of semiconductor materials and exposes the arrangement to radiation from a radionuclide material. 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 is a potential difference between the electrodes to allow the electrical energy generated 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 at 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 level radiation sources and high activity densities, however most semiconductor materials cannot withstand such high energy levels and are structurally degraded by exposure.

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

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

[0047] A number of metal materials and metal alloys were tested for suitability as electrodes, namely 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. In addition, different electrode configurations were investigated, where in a first configuration the electrode covered the entire surface of the zinc oxide layer, and 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, preferably 250 nm. 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-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] It was observed that there was negligible difference in the results for the different configurations, suggesting that the comb-grid configuration with its low metal usage is a viable option, and it will be understood that other geometries and configurations are 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 15000 Curies, with 10000 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 a practical system may have many different dimensions and may have single or multiple layers, or may be formed as the above cartridge with 50 or more layers. The substrate (sandwich) may be of any suitable area, for example 75 cm2. 2 ~62500cm 2 has been found to be appropriate.

[0052] It will be appreciated that structures having multiple layers of radionuclides 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 ​​1.0 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 a variety of 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) / min (average 420,000 rads (Rad) / hr), or 1.2 x 1013 photons / sec (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 100 mV, The average power generated, P IRR is 35.4mW, Maximum theoretical power output P Max is calculated to be 3.304 W. Conversion efficiency = P IRR / P Max =35.4 / 3304=1.07%.

[0056] Prolonged exposure to such high gamma fields would typically irreversibly damage 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, POBox 9001, Beer Sheva 84190, Israel).

[0058] In a separate test, 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 graphs of Co7 and Co9 in both "dark" and x-ray (200kV / 4.5mA) irradiation at 1000 kV. Both semiconductor wafers showed a strong response to x-ray photons. Co7 had negligible leakage current in both forward and reverse bias. Co9 had leakage current above +3v under dark conditions. At 5v, Co7 produced about 30mA of current. At 5v, Co9 produced about 15mA 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 lower than the calculated difference at about 4.1.

[0061] Across multiple individual semiconductor wafers, it was observed that at a distance of 5 cm, doubling the current from 4.5 mA to 9 mA resulted in a 1.2-fold increase in voltage and a current value 1.5 times that produced by the semiconductor. Thus, doubling the photon flux resulted in a 1.8-fold increase in power, a slightly lower increase 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 is 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, the activity of the radioisotope was approximately 535 TBq, and the measured dose rate was 76.3 Gy / min. The distance from the radioisotope to the semiconductor wafer was measured and estimated to be 10 cm. The gamma radiation impinging on the array was 1.83×10-1 J·s -1 It is.

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

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

Claims

1. A generator system comprising a radionuclide material and a sandwich structure, wherein the sandwich structure comprises 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 being in direct contact with the n-type semiconductor material and the other electrode being in contact with the p-type semiconductor material, forming a metal-semiconductor junction therebetween, and radiation emission received from the radionuclide material being converted into electrical energy at the metal-semiconductor junction, and metal electrodes, an electrical contact connected to the electrodes to allow the electrical energy to flow easily when connected to a load, A generator system comprising.

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

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

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

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

6. 10 or more repetitions of the sandwich structure are arranged in a unit, and a plurality of such units are arranged in a shielded cavity, the cavity also containing one or more sections of radioactive material. The generator system according to claim 2.

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

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

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

10. A power supply device comprising a housing surrounding the generator system according to claim 1 or claim 2.

Images