A diluted magnetic semiconductor thin film for In-based semiconductor material and a method for preparing the same

Abstract

The application belongs to the technical field of semiconductor thin film materials, and particularly relates to a diluted magnetic semiconductor thin film for In-based semiconductor materials. 2‑x M x O3, the doping element is a non-magnetic transition metal M, which is one or more of Fe, Mn, Co or Ni, and 0 < x < 0.1. The application adopts a laser pulse deposition technology (PLD) based on a ceramic target material to prepare an InO-based diluted magnetic semiconductor thin film with room-temperature ferromagnetism by means of a transition metal ion as a donor doping mode. The PLD technology of the application can incorporate a high proportion of transition metal ions into the InO lattice, and a large number of lattice defects can be introduced by controlling the deposition conditions, so that a ferromagnetic thin film material higher than room temperature is induced, which can be applied to spin electronic devices.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor thin film materials, and particularly relates to a magnetic semiconductor thin film for In-based semiconductor materials and a preparation method thereof. BACKGROUND

[0002] In recent years, with the continuous reduction in the size of chips, the volume of transistors is increasingly close to the physical size limit, and the development of traditional semiconductor technology will inevitably encounter a bottleneck. Spintronics is an effective solution to break through this bottleneck.

[0003] Spintronic devices are a new type of multi-performance device that can realize mutual regulation of the charge state and spin state of electrons in the same system. Compared with traditional microelectronic devices, spintronic devices have the advantages of non-volatile storage memory, high operation speed, low power consumption and high integration. Therefore, spintronic devices such as spin-LED and spin-FET will have a revolutionary impact on the global semiconductor industry. The "up" and "down" of the magnetic spin can be used as the logic units "on" and "off" and applied to the chips of future computers.

[0004] However, due to the low spin injection efficiency between metals and semiconductors, spintronic devices have not been fully integrated into the mainstream semiconductor industry. In order to achieve effective control of the spin state of electrons in semiconductors, a new material with both semiconductor and magnetic properties needs to be developed. Diluted magnetic semiconductors (DMS) refer to magnetic semiconductors formed by replacing some atoms in traditional semiconductors with transition metal elements. Due to the properties of both semiconductors and magnets, both the charge state and spin state of electrons can be applied in this material, and it is considered to be the best material for manufacturing spintronic devices. DMS based on wide-bandgap oxide semiconductors has been widely reported to have room-temperature ferromagnetism, however, there are almost no reports in the prior art indicating whether the ferromagnetism of these oxide-based DMS is carrier-mediated. In oxide-based DMS, many factors, such as vacancies, lattice distortion or interstitials, can affect ferromagnetism. Therefore, the carrier-mediated mechanism is not clear. The applicant of the present application previously filed a Chinese invention patent ZL 202011490687.3, which provides a ZnO-based diluted magnetic semiconductor thin film with room-temperature ferromagnetism and a preparation method thereof. The chemical formula of the thin film composition is Zn 1-x M x O, which is doped with a non-magnetic element M, and M is one of Cu, Na, Li or Ag; however, the thin film can only be used for Zn-based semiconductors, and there is no report of a diluted magnetic semiconductor thin film for In-based semiconductor materials in the prior art. SUMMARY

[0005] An object of the present application is to provide a diluted magnetic semiconductor thin film for In-based semiconductor material, which is doped with transition metal elements and has room-temperature ferromagnetism.

[0006] Another object of the present application is to provide a preparation method for the above-mentioned InO-based diluted magnetic semiconductor thin film.

[0007] To achieve the above object, the present application provides the following technical solutions.

[0008] An object of the present application is to provide a diluted magnetic semiconductor thin film for In-based semiconductor material, which is doped with transition metal elements and has room-temperature ferromagnetism.

[0009] The thin film is prepared by the following steps: In 2-x M x O3 ceramic target is prepared by isostatic pressing solid-phase reaction synthesis process, and the thin film is prepared by laser pulse deposition, wherein the power of laser in the laser pulse deposition process is 100-300 mJ, the thickness of the film is controlled to be 30-100 nm, and the oxygen partial pressure PO2 is between 10 -3 ~10 -8 torr.

[0010] The chemical composition of the thin film is In 2-x Fe x O3, and x=0.05.

[0011] The thin film with the chemical formula In 1.95 Fe 0.05 O3 is doped with 5% molar Fe, and the film deposition is completed under the oxygen partial pressure of 10 -3 , 10 -5 and 10 -7 torr.

[0012] The room-temperature saturation magnetization MS of the semiconductor thin film is 2-14 emu / cm 3 .

[0013] A preparation method for the above-mentioned diluted magnetic semiconductor thin film for In-based semiconductor material, which comprises the following steps:

[0014] (1) In 2-x M x O3 ceramic target is prepared by isostatic pressing solid-phase reaction synthesis process;

[0015] (2) Clean and dry substrates are placed in a PLD system reaction chamber, and the reaction chamber is vacuum-extracted to ≤1×10-8 torr, heating the substrate to a temperature of 400-700°C, and then vacuum pumping the reaction chamber to ≤ 1 x 10 -8 torr;

[0016] (3) the power of the laser is 100-300 mJ, the thickness of the film is controlled to be 30-100 nm, the substrate temperature is varied between 400-700°C, the oxygen partial pressure (P02) is varied between 10 -3 -10 -8 torr, and the saturation magnetization increases with the decrease of the oxygen partial pressure, while avoiding the formation of dopant clusters or second phases, to obtain a transition metal element-doped InO-based diluted magnetic semiconductor film with room-temperature ferromagnetism.

[0017] In step (1), the In 2-x M x O3 ceramic target is prepared by an isostatic pressing solid-phase reaction synthesis process, comprising the following steps: taking In2O3, Fe2O3 (MnO, CoO, NiO) raw materials according to the stoichiometric ratio of In, M and O in In 2-x M x O3, mixing them thoroughly, pre-pressing them into a shape, then isostatic pressing them, and finally firing them by a solid-phase reaction method to obtain the In 2-x M x O3 ceramic target.

[0018] In step (1), the In2O3, Fe2O3, MnO, CoO and NiO raw materials are all high-purity raw materials with a purity of ≥ 99.99%, and the firing temperature of the solid-phase reaction method is 800-1200°C, and the holding time is at least 10 hours.

[0019] In step (2), the substrate material is Si, SiO2 or MgO.

[0020] In step (3), the film thickness and / or saturation magnetization are adjusted by controlling the following deposition parameters:

[0021] When the film thickness is 30-50 nm, the deposition temperature is 600±20°C, the oxygen partial pressure is 10 -3 -10 -8 torr, and the deposition time is 7-13 min.

[0022] When the film thickness is 50-100 nm, the deposition temperature is 600±20°C, the oxygen partial pressure is 10 -3 -10 -8 torr, and the deposition time is 13-25 min.

[0023] The room-temperature saturation magnetization is 2-5 emu / cm 3at 600 ± 20 °C and 10 -5 ~ 10 -3 torr.

[0024] The room temperature saturation magnetization is 12 ~ 14 emu / cm 3 at 600 ± 20 °C and 10 -7 torr.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] Spintronic devices require high degree of carrier-mediated DMS because the properties of spintronic devices need to be controlled by carriers. Therefore, it is very important to study whether the oxide-based DMS is carrier-mediated ferromagnetic. Among the known materials, Mn-doped GaAs is carrier-mediated. However, the low Curie temperature (173 K) makes it difficult to be applied in practice. The Curie temperature can be roughly expressed as: T C ∝ P 1 / 3 , where P is the hole concentration. DMS based on wide band gap oxide semiconductor has been widely reported to have room temperature ferromagnetism. However, few reports indicate whether the ferromagnetism of these oxide-based DMS is carrier-mediated. In oxide-based DMS, many factors, such as vacancies, lattice distortion or interstitials, can all affect the ferromagnetism. Therefore, the carrier-mediated mechanism is not clear. In the preparation of oxide-based DMS, the change of deposition temperature, oxygen partial pressure or post-annealing temperature, as well as the injection of other ions, can be used to adjust the carrier type and concentration. The present application uses non-equilibrium physical deposition technology, in which a high proportion of transition element dopant is doped in wide band gap oxide semiconductor, to provide sufficient magnetic moment, introduce specific lattice defects, provide high carrier concentration, and change the distribution of dopants in the material by adjusting the deposition parameters, i.e. by increasing the doping concentration, reducing the oxygen partial pressure, so that the dopants tend to gather in the interface region of the film and the substrate, to prepare transition metal element doped DMS with room temperature ferromagnetism. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 TEM image of Fe-doped InO thin film prepared in an embodiment of the present application: deposited on MgO substrate at 10 -3 torr, 10 - 5 torr and 10 -7 torr.

[0028] Figure 2 XRD image of Fe-doped InO thin film prepared in an embodiment of the present application: deposited on MgO substrate at 10 -3 torr, 10- 5 torr and 10 -7 torr were deposited on MgO substrates.

[0029] Figure 3 M-H curve of Fe-doped InO thin film prepared in the embodiment of the present application at room temperature: the oxygen partial pressure was 10 - 3 torr, 10 -5 torr and 10 -7 torr were deposited on MgO substrates; the inset shows an enlarged display of the low magnetic field region.

[0030] Figure 4 TEM and EDS spectrum of Fe-doped InO thin film prepared in the embodiment of the present application: the oxygen partial pressure was 10 - 3 torr, 10 -5 torr and 10 -7 torr were deposited on MgO substrates.

[0031] Figure 5 Depth distribution curve of In, O and Fe elements of Fe-doped InO thin film prepared in the embodiment of the present application: the oxygen partial pressure was 10 -7 torr were deposited on MgO substrates. DETAILED DESCRIPTION

[0032] The present application will be described in further detail below with specific embodiments.

[0033] A preparation method of a diluted magnetic semiconductor thin film for In-based semiconductor material is as follows:

[0034] (1) In 2-x M x O3 ceramic target is prepared by isostatic pressing solid phase reaction synthesis process;

[0035] (2) clean and dry substrate is put into a PLD system reaction chamber, the reaction chamber is vacuumed to ≤1×10-8torr, the substrate temperature is heated to 400-700℃, and then the reaction chamber is vacuumed to ≤1×10-8torr again;

[0036] (3) the power of laser is 100-300mJ, the thickness of film is controlled to 30-100nm, the oxygen partial pressure (PO2) is changed between 10-3-10-8torr, and the transition metal element-doped InO-based diluted magnetic semiconductor thin film with room temperature ferromagnetism is obtained by avoiding formation of dopant clusters or second phase during film deposition.

[0037] In step (1), the isostatic pressing solid phase reaction synthesis process is used to prepare In2-x M x O3 ceramic target material, comprising the following steps: according to In 2-x M x O3 stoichiometric ratio of In2O3, Fe2O3 (MnO, CoO, NiO) raw materials, after mixing, first pre-pressing, then using isostatic pressing, finally with solid phase reaction method firing to obtain the In 2-x M x O3 ceramic target material.

[0038] The In 2-x M x O3 ceramic target material preparation method In2O3, Fe2O3 (MnO, CoO, NiO) raw materials are high purity raw materials, purity ≥ 99.99%.

[0039] The solid phase reaction method for preparing In 2-x M x O3 ceramic target material firing temperature 800-1200℃, holding time at least 10 hours.

[0040] In step (2), the substrate material is Si, SiO2 or MgO.

[0041] Embodiment:

[0042] In2O3 film (In 1.95 Fe 0.05 O3) doped with 5% molar Fe is deposited at 10 -3 torr:

[0043] (1) In 1.95 Fe 0.05 O3 target material is prepared by using standard isostatic pressing solid phase reaction synthesis process. According to the stoichiometric ratio of In 1.95 Fe 0.05 O3 corresponding elements, high purity (≥99.99%) In2O3 and Fe2O3 are weighed by electronic balance, mixed thoroughly, first pre-pressing (60MPa), then cold isostatic pressing (150MPa), finally placed in a tube furnace and gradually heated to 1200℃, and kept for 10 hours.

[0044] (2) The substrate (MgO) is cleaned of foreign matter on the surface in an ultrasonic cleaning instrument, dried with N2 and placed in the deposition chamber of the pulsed laser deposition device.

[0045] (3) The clean and dry substrate is placed in the deposition chamber of the PLD device, then the vacuum degree in the deposition chamber is pumped to 1×10 -7 torr or below, the substrate temperature is heated to 600℃, and then the reaction chamber is vacuum pumped to 1×10-7 torr or less;

[0046] (4) The power of the laser is adjusted to 180 mJ, the oxygen partial pressure (P O2 ) is set to 10 -5 torr, and the formation of dopant clusters or second phases is avoided, and thin film deposition is performed to obtain an In 1.95 Fe 0.05 O3 film, the thickness of the film is controlled to be about 40 nm, and the obtained room temperature magnetic properties are: 5 emu / cm 3 .

[0047] Figure 2 The XRD pattern of the Fe-doped InO thin film prepared in the embodiment of the present application is deposited on an electrode substrate MgO at an oxygen partial pressure of 10 -3 torr, 10 - 5 torr, and 10 -7 torr. As can be seen from the figure, the XRD spectrum of the In 1.95 Fe 0.05 O3 film has several peaks (222), (400) and (444) corresponding to In2O3, indicating that the In 1.9 Fe 0.1 O3 films grown at different oxygen partial pressures have a high texture of body-centered cubic hematite crystal structure.

[0048] The present application aims at the problem of low spin injection efficiency between existing metals and semiconductors, and through a non-equilibrium film preparation technology, a high proportion of transition element dopants is doped in a wide-gap oxide semiconductor, specific lattice defects are introduced, a transition metal element-doped DMS is prepared, and room temperature ferromagnetism is realized.

[0049] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, several improvements can be made without departing from the principles of the present application, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A diluted magnetic semiconductor thin film for an In-based semiconductor material, characterized by: The thin film adopts a transition metal element doped InO-based semiconductor material, and the general formula of the chemical composition is In 2-x M x O3, the doping element M is one or several of Fe, Mn, Co or Ni, wherein 0 < x ≤ 0.1; The film is prepared by the following steps: In 2-x M x O3 ceramic target material is prepared by laser pulse deposition, in which the power of laser is 100-300 mJ, the thickness of film is controlled to be 30-100 nm, the oxygen partial pressure PO2 is between 10 -3 ~10 -8 torr; the saturation magnetization increases with the decrease of oxygen partial pressure; By increasing the doping concentration, reducing the oxygen partial pressure, making the dopant tend to gather in the interface region of the film and the substrate, a transition metal element doped DMS is prepared, and has room temperature ferromagnetism as follows: The semiconductor thin film has a room temperature saturation magnetization MS of 2 to 14 emu / cm 3 .

2. The diluted magnetic semiconductor thin film according to claim 1, wherein: The chemical composition of the thin film is In 2- x Fe x O3, x = 0.

05.

3. The diluted magnetic semiconductor thin film according to claim 2, wherein: The chemical formula is In 1.95 Fe 0.05 O3 thin film, doped with 5% molar Fe in In2O3, was deposited at 10 -3 , 10 -5 and 10 -7 torr oxygen partial pressure.

4. The method of claim 1, wherein the method is performed by the steps of: The method comprises the following steps: ​ (1) InGaO3: (Mg, Zn) ceramic target is prepared by isostatic pressing solid phase reaction synthesis process 2-x M x O3 ceramic target (2) Place the clean dry substrate into the PLD system reaction chamber, vacuum pump the chamber to < 1 x 10 -8 torr, heat the substrate temperature to 400-700°C, and then vacuum pump the chamber to < 1 x 10 -8 torr; (3) The power of the laser is 100-300 mJ, the thickness of the film is controlled to be 30-100 nm, the substrate temperature is varied between 400-700 °C, the oxygen partial pressure (P02) is varied between 10 -3 -10 -8 torr, the saturation magnetization increases with the decrease of the oxygen partial pressure, and the transition metal element-doped InO-based diluted magnetic semiconductor film with room-temperature ferromagnetism is obtained by depositing the film while avoiding the formation of dopant clusters or second phases, and the room-temperature saturation magnetization MS of the semiconductor film is 2-14 emu / cm 3 .

5. The preparation method according to claim 4, characterized in that, In step (1), the isostatic pressing solid-phase reaction synthesis process is used to prepare In 2-x M x O3 ceramic target material, including the following steps: according to In 2-x M x The stoichiometric ratio of In, M, and O in O3 is determined by weighing In2O3 and one or more raw materials selected from Fe2O3, MnO, CoO, and NiO. After thorough mixing, the mixture is first pre-pressed, then isostatically pressed, and finally calcined using a solid-state reaction method to obtain the desired In content. 2-x M x O3 ceramic target material.

6. The production method according to claim 5, wherein In step (1), In2O3, Fe2O3, MnO, CoO and NiO raw materials are high-purity raw materials, and the purity is all ≥99.99%; the firing temperature of the solid-phase reaction method is 800-1200 ℃, and the holding time is at least 10 hours.

7. The preparation method according to claim 4, characterized in that, In step (2), the substrate is Si, SiO2 or MgO.

8. The preparation method according to claim 4, characterized in that, In step (3), the film thickness and / or saturation magnetization are adjusted by controlling the following deposition parameters: The film thickness is 30-50 nm, the deposition temperature is 600±20℃, the oxygen partial pressure is 10 -3 -10 -8 torr, and the deposition time is 7-13 min. The film thickness is 50-100 nm, the deposition temperature is 600±20℃, the oxygen partial pressure is 10 -3 -10 -8 torr, and the deposition time is 13-25 min. Saturation magnetization at room temperature 2-5 emu / cm 3 600 ± 20 °C, oxygen partial pressure 10 -5 ~ 10 -3 torr; Saturation magnetization at room temperature is 12-14 emu / cm 3 600 ± 20 °C, oxygen partial pressure 10 -7 torr.

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