CN115171944A

CN115171944A - Based on GaAs/Al x Ga 1-x As heterojunction beta radiation volt effect nuclear battery

Info

Publication number: CN115171944A
Application number: CN202210799059.6A
Authority: CN
Inventors: 陆景彬; 张雪; 郑人洲; 王宇; 陈子怡; 梁磊; 曾玉刚
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2022-07-08
Filing date: 2022-07-08
Publication date: 2022-10-11

Abstract

The invention discloses a method based on GaAs/Al _x Ga _1‑x As heterojunction beta radiative voltaic effect nuclear cells. The basic structure of which is a radioactive source ⁶³ Ni, p-face electrode, p-type GaAs cap layer, p-type Al _x Ga _1‑x As window layer, p-type Al _x Ga _1‑x As emitting layer and n-type Al _x Ga _1‑x As basic unit, n type GaAs buffer layer, n face electrode. In the nuclear battery structure, the cap layer is heavily doped, which is beneficial to ohmic contact. The window layer uses wide band gap AlGaAs, and the potential barrier difference formed by the window layer and the emission layer can inhibit the diffusion of minority electrons and reduce the recombination of the minority electrons at an interface. The core region of the nuclear battery is the emissive layer and the base layer, and the core region generates electron-hole pairs, which are then separated by a built-in electric field. The buffer layer inhibits the diffusion of a few holes, improves the stability of the semiconductor device, improves the performance of the device and prolongs the service life of the device. The GaAs/Al _x Ga _1‑x As heterozygote cells are capable of generating larger built-in potential differencesThe open-circuit voltage is higher, the output power of the battery is improved, and the output performance of the battery is improved.

Description

Based on GaAs/Al x Ga 1-x As heterojunction beta radiation volt effect nuclear battery

Technical Field

The invention belongs to the field of semiconductor device technology and nuclear energy technology utilization, and particularly relates to a GaAs/Al-based semiconductor device _x Ga _1-x As heterojunction beta radiant voltaic effect nuclear cells.

Background

The micro-electro-mechanical system is an integration of a micro-circuit and a micro-machine on a chip according to functional requirements, has a size generally in a millimeter or micron scale, is an important research field of current interdiscipline subjects, and relates to a plurality of scientific and technical projects such as electronic engineering, material engineering, mechanical engineering, information engineering and the like. The micro electro mechanical system has the following characteristics of (1) miniaturization; the micro electro mechanical system device has small volume, light weight, low energy consumption, small inertia, high resonant frequency and short response time. (2) mass production; hundreds of microelectromechanical devices or complete microelectromechanical systems may be fabricated simultaneously on a single piece of silicon using silicon micromachining processes. The mass production can greatly reduce the production cost. (3) integration: multiple sensors or actuators with different functions, different sensitive directions or actuating directions can be integrated into a single body, or form a micro sensor array, a micro actuator array, or even integrate multiple functional devices together to form a complex microsystem. The integration of microsensors, microactuators, and microelectronic devices can produce microelectromechanical systems with high reliability and stability. (4) convenient expansion: because the mems technology is modular, the equipment operators only need to directly increase the number of devices/systems when increasing the system capacity, rather than calculating the required number of devices/systems in advance. (5) multidisciplinary crossing: microelectromechanical systems (mems) are involved in many disciplines, electronic, mechanical, materials, manufacturing, information and automation, physics, chemistry, and biology, and have integrated many of the most sophisticated efforts in today's scientific and technological development. Conventional micro-cells include primarily micro-chemical, battery micro-fuel cells, micro-solar cells, and the like. Compared with the traditional micro battery, the beta radiation volt effect nuclear battery has the characteristics of miniaturization, integration, light weight, long service life, high energy density, stable output performance and the like. In 1953, rapppaport et al produced the first pn junction beta-emitter voltaic effect nuclear cell. Since then, beta-radiation volt-effect nuclear batteries have received extensive attention from researchers and have been rapidly developed. In 2019, reyyan KavakYu gun et al studied and compared GaN nuclear cells and GaN-Si heterojunctions cells for the first time. Compared with a GaN nuclear battery, the GaN-Si heteronuclear battery has higher electron-hole pair collection efficiency. Moreover, the GaN-Si heterojunction battery has lower reverse saturation current, and higher open-circuit voltage is obtained, so that the output power of the battery is increased, and the output performance of the battery is improved. In addition, in the heterojunctions, the energy level height at the heterojunction interface is reduced, which is beneficial to the drift motion of the current carrier; the electron-hole pair recombination rate at the heterojunction interface is low because the depletion layer separates the electron-hole pairs, resulting in a reduced electron-hole pair recombination rate.

The beta-radio-voltaic effect nuclear battery consists of a beta radioisotope source and a semiconductor energy converter. When energetic particles released by the radioisotope interact with the semiconductor energy converter, the semiconductor is affected by the energetic particles and valence electrons in some covalent bonds gain enough energy to break loose the covalent bond and jump to the conduction band as free electrons while leaving the same number of holes in the covalent bond. Due to the existence of the hole, valence electrons in the adjacent covalent bonds can easily skip to fill the hole, so that the hole is transferred to the adjacent covalent bonds, and then the new hole is filled by the adjacent valence electrons, namely the generation process of the electron-hole pair. For a heterojunction, the primary role of the heterojunction interface between a p-type semiconductor and an n-type semiconductor is to separate electron-hole pairs while generating a built-in electric field. The built-in voltage is determined by the fermi levels of the two materials, the diffusion of majority carriers creates a built-in electric field, and the drift of minority carriers creates a reverse saturation current. After being separated by the built-in electric field, the electron-hole pairs are transmitted to an external circuit through electrons and holes, and then current is generated.

In beta-radiation volt-effect nuclear batteries, the commonly used radioactive sources are mainly ³ H、 ⁶³ Ni、 ⁹⁰ Sr/ ⁹⁰ Y、 ¹⁴⁷ Pm, etc. for ¹⁴⁷ Pm source, the maximum decay energy is very high, or a gamma emitter. But the lattice structure of the semiconductor material is seriously damaged, so that lattice displacement defects are caused, the minority carrier lifetime of the semiconductor material is reduced due to the lattice displacement defects, and the collection of electron-hole pairs is reduced. For the ⁹⁰ Sr/ ⁹⁰ A source of Y-radiation, ⁹⁰ the Y source is ⁹⁰ The Sr source generates beta decay to generate a daughter nucleus with a very short half-life ⁹⁰ The half-life of the Sr source is longer. ⁹⁰ Sr/ ⁹⁰ The average decay energy of the Y source is very large, around 1.1 MeV. ³ The specific power of beta particles released by decay of the H source is higher, the half life is moderate, but the average energy and the maximum energy are lower, so that ³ The H source generates fewer electron-hole pairs in the semiconductor material, resulting in a lower battery output. In addition to this, the present invention is, ³ the H source is gaseous and inconvenient to store. ⁶³ The half-life of the Ni source is long, and the average energy and the maximum energy of the energy-carrying beta particles released by the Ni source are moderate. Therefore, in the field of beta-radiation volt effect nuclear batteries, it is common ⁶³ Ni is used as a radioactive source.

Gallium arsenide is a second generation semiconductor material, belonging to the group iii-v compound semiconductors. The forbidden band width is larger than that of silicon, and the electron mobility is 6 times higher than that of silicon. The semiconductor device made of gallium arsenide has the advantages of good high-frequency, high-temperature and low-temperature performances, low noise, strong radiation resistance and the like, and the gallium arsenide becomes a necessity of ultrahigh-speed and ultrahigh-frequency devices and integrated circuits. In 2011, chen oceans et al measured the generation and recombination of electron-hole pairs in gaas semiconductors by beta particles for the first time and compared the measured short circuit current to an ideal value. In 2012, lidamask et al prepared pin and p + pinn + junctions ⁶³ Ni-GaAs cell, and found a p + pinn + junction ⁶³ The conversion efficiency of the Ni-GaAs cell is a pin junction ⁶³ 1.45 times of Ni-GaAs cell. Since then, more and more people have started to research on gallium arsenide semiconductor materials. In a pn junction, the p-region semiconductor and the n-region semiconductor are of the same materialThe pn junction of (a) is collectively called a homojunction, and pn junctions in which p-region semiconductors and n-region semiconductor materials are different are collectively called heterojunctions. The heteronodule battery has a lower reverse saturation current and a higher open circuit voltage, so that the output power of the battery is increased. Moreover, since GaAs and Al _x Ga _1-x The maximum lattice mismatch of the As two materials is 0.16%<0.5%, indicating GaAs and Al _x Ga _1-x As lattice matching is good. Thus, gaAs/Al _x Ga _1-x As is capable of forming a heterojunction. The conduction band and the valence band are discontinuous due to the difference of the forbidden band width and the electron affinity of two materials composing the heterojunction, so that the energy band of the heterojunction at the interface is mutated. Furthermore, the discontinuity of the conduction and valence bands will prevent carriers from flowing through the interface, which effect on the carriers is not present in a homojunction.

Disclosure of Invention

In order to solve the defects of the semiconductor structure in the conventional nuclear battery, the invention provides a GaAs/Al-based nuclear battery _x Ga _1-x As heterojunction beta radiative voltaic effect nuclear cells. GaAs/Al _x Ga _1-x As heterojunctions have a nuclear cell structure with multiple types of semiconductor materials, different thicknesses, and different doping concentrations. The GaAs/Al _x Ga _1-x The As heterogeneous nodule battery can realize higher open-circuit voltage, and further improve the output power of the battery, thereby improving the output performance of the battery.

In order to achieve the purpose, the technical solution of the invention is as follows:

GaAs/Al _x Ga _1-x as heterojunction cell basic structure: radiation source ⁶³ Ni, p-face electrode, p-GaAs, p-Al _x Ga _1-x As, p-type Al _x Ga _1-x As, n-type Al _x Ga _1-x As, n-type GaAs, n-side electrode. (see FIG. 1 and FIG. 1 for an illustration).

The radioactive source has surface emergent activity density of 6mCi/cm ² Thin sheet cuboid solid radioactive source ⁶³ Ni。

The first layer of the heterojunction transduction unit is a GaAs cap layer, and the p-type doping concentration range is 1 multiplied by 10 ¹⁸ cm ^-3 ～5×10 ¹⁹ cm ^-3 The thickness range is 0.01-0.1 μm. The cap layer is heavily doped, which is beneficial to ohmic contact.

The second layer of the heterojunction energy conversion unit is Al _x Ga _1-x An As window layer with p-type doping concentration in the range of 1 × 10 ¹⁸ cm ^-3 ～1×10 ¹⁹ cm ^-3 The thickness range is 0.01-0.1 μm. The window layer uses wide band gap material AlGaAs, the potential barrier difference formed by the window layer and the emission layer can inhibit the diffusion of minority electrons, reflect the minority electrons diffused to the interface back, and reduce the recombination of the minority electrons at the interface. According to the calculation result, the larger the Al coefficient, the better, the Al coefficient should be more than 0.7.

The third layer of the heterojunction energy conversion unit is Al _x Ga _1-x As emitting layer with p-type doping concentration in the range of 1 × 10 ¹⁸ cm ^-3 ～1×10 ¹⁹ cm ^-3 The thickness range is 3-4 μm. According to the calculation result, the smaller the Al coefficient, the better, the smaller the Al coefficient should be less than 0.5.

The fourth layer of the heterojunction energy conversion unit is Al _x Ga _1-x As base layer, n-type doping concentration range is 1 × 10 ¹⁸ cm ^-3 ～1×10 ¹⁹ cm ^-3 The thickness range is 2.5-3.5 μm. According to the calculation result, the output power is increased and then reduced along with the increase of the Al coefficient, and the Al coefficient ranges from 0.2 to 0.6. The core region of the nuclear battery is the emissive layer and the base layer, and the core region generates electron-hole pairs, which are then separated by a built-in electric field.

The fifth layer of the heterojunction transduction unit is a GaAs buffer layer, and the n-type doping concentration range is 1 multiplied by 10 ¹⁴ cm ^-3 ～1×10 ¹⁶ cm ^-3 The thickness range is 0.1-1 μm. The buffer layer inhibits the diffusion of the minority holes, reflects the minority holes diffused to the interface back, and simultaneously improves the stability, the performance and the service life of the semiconductor device.

The p-side electrode is made of Ti/Pt/Au alloy, the n-side electrode is made of Au/Ge/Ni alloy, and the thickness of the p-side electrode and the thickness of the n-side electrode are 260nm.

The external lead 9, the external lead 11 and the load 8 form a loop to generate current.

Drawings

FIG. 1 shows GaAs/Al of the present invention _x Ga _1-x The basic structure of the As heterojunction cell is shown in the figure. The mark in the figure is: 1 is a radioactive source ⁶³ Ni,2 is p-face electrode, 3 is p-type GaAs cap layer, 4 is p-type Al _0.9 Ga _0.1 An As window layer, 5 a p-type GaAs emission layer, and 6 an n-type Al _0.4 Ga _0.6 An As base layer, 7 an n-type GaAs buffer layer, 8 an n-face electrode, 9 a lead, 10 a load, and 11 a lead.

Detailed Description

For a better understanding of the present invention, reference is now made to FIG. 1. The nuclear battery structure is sequentially as follows from top to bottom: radiation source ⁶³ Ni, p-side electrode, p-type GaAs, p-type Al _x Ga _1-x As, p-type Al _x Ga _1-x As, n-type Al _x Ga _1-x As, n-type GaAs, n-plane electrode.

The main contents of the research of the beta radiation volt effect nuclear battery comprise: self-absorption of the radioactive source, energy deposition distribution of the radioactive source in the semiconductor material and transport and collection of carriers.

The phenomenon of energy loss during transport of particles released by decay of a radioisotope source inside the source is known as the self-absorption effect. Along with the increase of the thickness of the radioactive source, the particle emergent activity is increased, the energy loss in the radioactive source is strengthened, and the self-absorption effect of the radioactive source is gradually strengthened.

The radioactive source is ⁶³ A Ni source having a surface emission activity density of 6mCi/cm ² 。

Simulation of radioactive source using monte carlo method ⁶³ The energy deposition distribution of Ni in the semiconductor material further obtains the generation rate distribution of electron-hole pairs. As the penetration depth increases, the electron-hole pair generation rate tends to decrease in the e-index.

COMSOL software is the first real multi-physical-field coupling analysis software in the world, and as a large finite element calculation simulation platform, the COMSOL software can realize direct full-coupling numerical simulation of multi-scale and multi-physical fields. COMSOL software can simulate the generation and recombination of electron-hole pairs, wherein the concentration distribution of carriers can be simulated by utilizing the generation rate of the electron-hole pairs, and the recombination rate distribution of the electron-hole pairs can be obtained by adopting a Shockley-Read-Hall recombination model for the recombination of the electron-hole pairs. By optimizing the doping concentration and thickness of the semiconductor material, battery output performance parameters such as short-circuit current, open-circuit voltage, output power and the like of the heterogeneous nodule battery are obtained. The optimization results are as follows:

the semiconductor material of the cap layer is GaAs, and the p-type doping concentration is 2 multiplied by 10 ¹⁹ cm ^-3 The thickness is 0.01 μm to 0.02 μm and preferably 0.01 μm. The cap layer is favorable for ohmic contact when heavily doped. Furthermore, the capping layer is only for the purpose of increasing the formation of a good ohmic contact, so the thinner the capping layer is, the better. The smaller the thickness of the cap layer, the closer the depletion layer is to the region with high generation rate of electron-hole pairs, which is beneficial to the collection of the electron-hole pairs.

The semiconductor material of the window layer is Al _0.9 Ga _0.1 As, p-type doping concentration of 9X 10 ¹⁸ cm ^-3 The thickness is 0.01 μm to 0.02 μm and preferably 0.01 μm. The larger the Al coefficient of the window layer is, the larger the forbidden bandwidth is, so that the larger the potential barrier difference formed with the emission layer is, the diffusion of minority electrons is favorably inhibited, and the recombination of the minority electrons at an interface is reduced.

The semiconductor material of the emitting layer is GaAs, and the p-type doping concentration is 1 × 10 ¹⁹ cm ^-3 The thickness is 3.4 μm to 3.8 μm, and preferably 3.6 μm. The smaller Al coefficient of the emitting layer leads to the smaller forbidden bandwidth, so that the larger potential barrier difference formed by the emitting layer and the window layer is, the diffusion of minority electrons is favorably inhibited, and the recombination of the minority electrons at an interface is reduced.

The semiconductor material of the base layer is Al _0.4 Ga _0.6 As, n-type doping concentration is 8 x 10 ¹⁸ cm ^-3 The thickness is 2.8 μm to 3.2 μm and preferably 3 μm. The larger the Al coefficient of the base layer is, the larger the energy level of the base layer is, the smaller the energy level of the base layer is, and the larger the potential barrier difference formed by the emitter layer is. The larger the potential barrier difference formed by the emission layer and the base layer is, the larger the output power is, and the improvement of the output performance of the battery is facilitated.

The bufferThe semiconductor material of the layer is GaAs, and the n-type doping concentration is 1 × 10 ¹⁶ cm ^-3 The thickness is 0.1 μm to 0.2 μm and preferably 0.1 μm. The buffer layer is not too thick, so that the stability of the semiconductor device is improved, the performance of the device is improved, and the service life of the device is prolonged.

The p-surface electrode is Ti/Pt/Au alloy, the n-surface electrode is Au/Ge/Ni alloy, and the thickness of the p-surface electrode is 260nm. The surface of the electrode is welded with a lead wire to facilitate the connection of an external circuit.

In conclusion, the embodiment of the invention specifies a GaAs/Al based material _x Ga _1-x The specific technical scheme of the As heterojunction beta radiation volt effect nuclear battery. It should be noted that the above description is only a specific example of the present invention, and it is not intended to limit the design and fabrication of the nuclear battery of the present invention. In the description of the invention, for simplicity and clarity of illustration of structure and principles, reference is made to the accompanying drawings in which figure 1 illustrates general structure and principles and is not necessarily drawn to scale.

Claims

1. Based on GaAs/Al _x Ga _1-x As heterojunction beta radiation volt effect nuclear battery, its characterized in that, nuclear battery structure from supreme down do in proper order: radiation source ⁶³ Ni, p-face electrode, p-type GaAs cap layer, p-type Al _x Ga _1-x As window layer, p-type Al _x Ga _1-x As emitting layer and n-type Al _x Ga _1-x As basic unit, n type GaAs buffer layer, n face electrode.

2. GaAs/Al based on claim 1 _x Ga _1-x As heterojunction beta radiation volt effect nuclear battery, characterized in that the selected radiation source is ⁶³ Ni having a surface emission activity density of 6mCi/cm ² 。

3. GaAs/Al based on claim 1 _x Ga _1-x The As heterojunction beta radiation volt effect nuclear battery is characterized in that the doping concentration of the p-type GaAs cap layer is 2 multiplied by 10 ¹⁹ cm ^-3 Thickness of 0.01 μm。

4. GaAs/Al based on claim 1 _x Ga _1-x As heterojunction beta-radiative voltaic effect nuclear cell, characterized in that said p-type Al _x Ga _1-x As window layer doping concentration is 9 x 10 ¹⁸ cm ^-3 The thickness was 0.01. Mu.m.

5. GaAs/Al based on claim 1 _x Ga _1-x As heterojunction beta-radiometric voltaic effect nuclear cell, characterized in that said p-type Al _x Ga _1-x As emitting layer doping concentration is 1 x 10 ¹⁹ cm ^-3 The thickness was 3.6. Mu.m.

6. GaAs/Al based on claim 1 _x Ga _1-x As heterojunction beta-radiometric voltaic effect nuclear cell, characterized in that said n-type Al _x Ga _1-x As base layer doping concentration is 8 multiplied by 10 ¹⁸ cm ^-3 The thickness was 3 μm.

7. GaAs/Al-based semiconductor device as defined in claim 1 _x Ga _1-x The As heterojunction beta radiation volt effect nuclear battery is characterized in that the doping concentration of the n-type GaAs buffer layer is 1 multiplied by 10 ¹⁶ cm ^-3 The thickness was 0.1. Mu.m.

8. GaAs/Al based on claim 1 _x Ga _1-x The As heterojunction beta radiation volt effect nuclear battery is characterized in that the p-surface electrode is made of Ti/Pt/Au alloy, the n-surface electrode is made of Au/Ge/Ni alloy, and the thickness of the N-surface electrode is 260nm.