A high-efficiency unconventional doping method for increasing the carrier concentration of a semiconductor

Abstract

The application discloses a kind of unconventional doping methods of high efficiency to improve semiconductor carrier concentration, it is related to the field of semiconductor technology.A kind of unconventional doping methods of high efficiency to improve semiconductor carrier concentration: manufacture the vacancy defect of semiconductor original element, join a small amount of heteroatomic (stable atom) for stabilizing defect.In argon gas protection environment glove box, accurately weigh raw material, after weighing, be placed in quartz tube vacuum tube, then the quartz tube with raw material is placed in mar furnace, after sufficient reaction, remove quartz tube, quenching in cold water and cool rapidly, then anneal at 450 DEG C, after annealing, pour into agate grinding mortar and grind, then by hot-pressing sintering technology is made into good block material of compactness.The application method can improve the efficiency of semiconductor doping, while improving the carrier concentration of semiconductor in high efficiency without damaging its carrier mobility, greatly improve the electrical properties of semiconductor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor, and particularly relates to a non-conventional doping method for improving the carrier concentration of a semiconductor with high efficiency. BACKGROUND

[0002] Doping of a semiconductor to improve its conductivity is applied as a key technology to adjust the electrical characteristics of semiconductor materials and devices. A semiconductor material with excellent performance should maintain a high mobility on the basis of optimizing the carrier concentration. A common doping technology is to introduce a hetero element into an intrinsic semiconductor to provide carriers as an acceptor impurity or a donor impurity, and the carrier concentration will increase with the increase of the concentration of the acceptor impurity and the donor impurity. Due to the influence of factors such as limited solubility, atomic radius and electronegativity difference of the hetero atom in the crystal, the semiconductor doping process has the problem of low efficiency. The way of adding excess impurities to improve the doping amount inevitably introduces second-phase nano precipitates and scattered carriers to reduce the mobility, which has a negative impact on the improvement of the electrical performance. Another solution is to artificially manufacture defects by preparing components with a deviated mass ratio to increase the carrier concentration, but since most defects have a high formation energy, it is difficult to form point defects at a specific element position, and the deviated mass ratio will also produce impurity precipitates, which are not conducive to the improvement of the conductivity of the semiconductor. Therefore, for a long time, researchers have been committed to exploring new doping processes in semiconductors, trying to find a method that can greatly improve the carrier concentration while having little effect on the carrier mobility. SUMMARY

[0003] The application provides a non-conventional doping method for improving the carrier concentration of a semiconductor with high efficiency. Taking the thermoelectric material Cu3SbSe4 as an example, the problem of low doping efficiency and poor conductivity of the existing semiconductor is solved.

[0004] The application relates to a non-conventional doping method for improving the carrier concentration of a semiconductor with high efficiency, and the operation steps are as follows:

[0005] S1. Accurately weigh the raw materials, and then place them in a quartz tube for vacuum sealing;

[0006] S2. Place the quartz tube containing the raw materials in a molar furnace, and after sufficient reaction, take out the quartz tube and quench it in cold water, and then perform annealing at 450 DEG C;

[0007] S3. Grind the annealed sample in an agate grinding bowl, and then use a hot-press sintering technology to prepare a block material with good compactness.

[0008] Hot-pressing sintering is a powder material forming process in which pressing and sintering are simultaneously performed, and is a process in which powder is loaded in a pressing mold, and is heated to below the melting point while being pressed in one direction or two directions in a special hot press.

[0009] Further, the raw materials are weighed in a glove box with argon.

[0010] The weighed raw materials are more accurate, and meanwhile, the raw materials can be prevented from reacting with the external environment.

[0011] Further, the raw materials are Cu3Sb 1-δ Se4-x CuAlSe2, Cu3Sb 1-δ The mass ratio x of Se4-x CuAlSe2 is 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, or 7wt%.

[0012] In this way, high-quality thermoelectric materials can be obtained.

[0013] Further, the muffle furnace is heated to 900 DEG C at a rate of 5 DEG C / min -1 , and is kept for 12 hours.

[0014] Principle of the present application:

[0015] In the constituent elements of the semiconductor, the element that contributes least to the energy band structure near the Fermi level, i.e., the element that has less influence on the electric transport, is irregularly doped, a point defect is designed at the position of the element, and another impurity element is filled in the vicinity of the position for reducing the defect formation energy, as a stable atom for stabilizing the point defect at the characteristic position, and improving the carrier concentration.

[0016] The semiconductor Cu3SbSe4 of the present application is composed of Cu, Sb, and Se, and Sb is an ideal position for designing defects because it contributes less to the energy band structure near the Fermi level. However, theoretical calculation shows that the Sb defect has a high formation energy, and experiments show that the Sb vacancy cannot form the intrinsic defect alone. Therefore, a vacancy is designed at the position of Sb, and a small amount of Al element is doped, and the filling amount of Al is much smaller than the number of Sb vacancies, for stabilizing the Sb vacancy, as a stable atom, which has little influence on the improvement of the carrier concentration, and the carrier concentration in the doping process is mainly improved by the Sb defect as a donor impurity, for improving the hole concentration, and realizing the conductive behavior conversion of the material from a non-degenerate semiconductor to a degenerate semiconductor. The specific implementation manner is to add CuAlSe2, and the stable atom Al enters Cu3Sb 1-δSe4, so that Sb defects are stabilized and carrier concentration is improved. For semiconductor materials requiring high carrier concentration, the present application is an efficient way to improve carrier concentration by manufacturing intrinsic defects, and a very unconventional doping method by introducing stable atoms to reduce defect formation energy, which can stabilize the semiconductor material with high carrier concentration and high mobility.

[0017] The present application has the following advantages:

[0018] 1. The present application can efficiently improve the efficiency of semiconductor doping.

[0019] 2. The present application method introduces Al as a stable atom at the Sb position to reduce the Sb defect formation energy and further stabilize the Sb defect formation. Since Sb has 5 valence electrons, theoretically one Sb defect can provide 5 hole carriers, while the best hetero-element single Sn doping of the material only provides 1 hole. Compared with the conventional doping method, the efficiency of the present application in improving carrier concentration is greatly improved. By unconventional doping of Cu3SbSe4, the carrier concentration is optimized to improve the electrical performance.

[0020] 3. The semiconductor Cu3SbSe4 prepared by the method of the present application has very excellent electrical performance. The intrinsic carrier concentration of the material is increased from 1.0×10 18 cm -3 to 3.1×10 20 cm -3 , the carrier concentration is increased by two orders of magnitude, and the unconventional doping sample maintains almost unchanged mobility with the increase of carrier concentration. In our various optimization attempts of Cu3SbSe4, the material prepared by the method of the present application has a much higher carrier mobility than other materials under the same carrier concentration. Compared with other copper-based diamond structure thermoelectric materials, it has the highest average power factor (PF, representing the electrical performance of the material) and the highest average thermoelectric value (zT, indicating the conversion efficiency of the material) under the same temperature conditions. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the doping energy diagram of Cu3Sb 1-δ Se4;

[0022] Figure 2 is the relationship diagram of x CuAlSe2 sample fraction and Cu3Sb 1-δ Se4 atomic percentage;

[0023] Figure 3 is the relationship diagram of Cu3Sb 1-δ Se4 and temperature;

[0024] Figure 4Cu3Sb doped for the method of the present invention 1-δ Comparison of Se4 with conventional doping

[0025] Figure 5 Cu3Sb doped for the method of the present invention 1-δ ZT map of Se4

[0026] Figure 6 Cu3SbSe4 of the present invention and Cu3Sb 1-δ Structure diagram of Cu3SbSe4. DETAILED DESCRIPTION

[0027] The present invention will be further described in conjunction with the accompanying drawings and detailed description:

[0028] Example 1

[0029] A non-conventional doping method for efficiently increasing the carrier concentration of semiconductors, the preparation steps are as follows: raw materials are weighed according to the mass ratio Cu3Sb 1-δ Se4-x CuAlSe2(x = 2wt%), the raw materials are accurately weighed in a glove box with an argon protection environment, and then placed in a quartz tube for vacuum sealing; the quartz tube containing the raw materials is placed in a muffle furnace, which is slowly heated to 900°C at a rate of 5°C / min -1 , and kept for 12 hours to allow the raw materials to fully react. Then the quartz tube is taken out and quenched in cold water for rapid cooling, followed by annealing at 450°C. The annealed sample is poured into an agate grinding bowl and carefully ground into powder. Then a dense bulk material is prepared by hot-pressing sintering technology.

[0030] Example 2

[0031] A non-conventional doping method for efficiently increasing the carrier concentration of semiconductors, the preparation steps are as follows: raw materials are weighed according to the mass ratio Cu3Sb 1-δ Se4, CuAlSe2(x = 3wt%), the raw materials are accurately weighed in a glove box with an argon protection environment, and the remaining operation steps are the same as in Example 1.

[0032] Example 3

[0033] A non-conventional doping method for efficiently increasing the carrier concentration of semiconductors, the preparation steps are as follows: raw materials are weighed according to the mass ratio Cu3Sb 1-δ Se4, CuAlSe2(x = 4wt%), the raw materials are accurately weighed in a glove box with an argon protection environment, and the remaining operation steps are the same as in Example 1.

[0034] Example 4

[0035] A non-conventional doping method for improving the carrier concentration of semiconductor with high efficiency, the preparation steps are as follows: the raw materials are weighed according to the mass ratio Cu3Sb 1-δ Se4, CuAlSe2 (x=5wt%), the raw materials are accurately weighed in a glove box with argon protection environment, and the remaining operation steps are the same as those of example one.

[0036] Example five

[0037] A non-conventional doping method for improving the carrier concentration of semiconductor with high efficiency, the preparation steps are as follows: the raw materials are weighed according to the mass ratio Cu3Sb 1-δ Se4, CuAlSe2 (x=6wt%), the raw materials are accurately weighed in a glove box with argon protection environment, and the remaining operation steps are the same as those of example one.

[0038] Example six

[0039] A non-conventional doping method for improving the carrier concentration of semiconductor with high efficiency, the preparation steps are as follows: the raw materials are weighed according to the mass ratio Cu3Sb 1-δ Se4, CuAlSe2 (x=7wt%), the raw materials are accurately weighed in a glove box with argon protection environment, and the remaining operation steps are the same as those of example one.

[0040] The Cu3SbSe4

[0041] As Figure 1 shown, the figure expresses the difficulty of the unconventional doping method of the application, according to the calculation, the Sb defect formation energy is very large, and it is almost impossible to form. Although it is known that the defect can optimize the electrical performance without damaging the Hall mobility, but the conventional method cannot be realized, and it is necessary to reduce its defect formation energy;

[0042] Based on this, a small amount of Al atoms is introduced to reduce the defect formation energy of Sb, so as to stabilize the Cu3Sb 1-δ Se4 sample with Sb vacancies, and good optimization effect is obtained. The Al content is far lower than the concentration of Sb vacancies, by lacking the content of Sb in the process of weighing the raw materials, CuAlSe2 is added to form a composite, as shown in Figure 2 and Figure 6 A small amount of Al will enter the Cu3Sb 1-δ Se4 matrix to stabilize the Sb defect, and the measurement data of electron probe and theoretical calculation can support and prove the formation of Sb defect and the existence of Al in the Cu3Sb 1-δ Se4 matrix.

[0043] As Figure 3As shown, compared with the intrinsic conduction properties shown by the undoped parent Cu3SbSe4, the sample with Sb vacancies designed by the application changes into non-intrinsic conduction properties, the conductivity σ decreases with the increase of temperature, the Seebeck coefficient S increases with the increase of temperature, showing good electrical properties, and finally the parameter power factor PF related to the power density of thermoelectric power generation is greatly improved in the whole temperature range, and the optimization of electrical properties mainly comes from the greatly improved carrier concentration n H .

[0044] As shown in Fig. a in the foregoing Figure 4 , in the experiment of doping Al to stabilize Sb vacancies by the method of the application, with the increase of carrier concentration, the mobility almost remains unchanged, and the average is about 42 cm 2 V -1 s -1 . Figure 4 b indicates that compared with other works, although the conventional doping improves the carrier concentration, the Hall mobility decreases obviously, while the unconventional doping method of the application can efficiently improve the carrier concentration and optimize the electrical properties, and the material still maintains a relatively high mobility, so that the material obtains a relatively high thermoelectric power factor.

[0045] As shown in the foregoing Figure 5 , finally, the Cu3SbSe4 semiconductor with the highest thermoelectric merit is obtained.

[0046] The above is only an embodiment of the application, and the common knowledge of specific structures and properties in the scheme is not described in detail. It should be pointed out that for those skilled in the art, without departing from the structure of the application, a number of modifications and improvements can be made, which should also be regarded as the protection scope of the application, and these will not affect the effect and practicality of the application. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. A method of high efficiency, unconventional doping of semiconductors to increase carrier concentration, characterized in that, The operation steps are as follows: S1. The raw materials are accurately weighed and placed in a quartz tube for vacuum sealing after weighing; S2. The quartz tube containing the raw materials is placed in a muffle furnace, and after sufficient reaction, the quartz tube is taken out and quenched in cold water, and then annealed at 450 DEG C; S3. The sample after annealing is ground into a good block material with good compactness by a hot-pressing sintering technique; The raw materials are weighed in an argon glove box; The raw material is Cu3Sb 1-δ Se4-x CuAlSe2, the mass ratio x = 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt% of Cu3Sb 1-δ Se4-x CuAlSe2, the mass ratio x = 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt% of Cu3Sb In step S2, the muffle furnace is set at 5°C / min. -1 The temperature was increased to 900℃ at a certain rate and held for 12 hours.

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