CN101195743A - Structure and preparation method of MnInAs/GaAs quantum dot sample with photomagnetic properties - Google Patents

Abstract

A kind of optical magnetic property of the present invention contains the structure of MnInAs/GaAs quantum dot sample, comprises: a substrate; A buffer layer, this buffer layer is deposited on the substrate, and it can effectively prevent the dislocation in the substrate from possibly extending to In the epitaxial layer; an insulating layer, the insulating layer is deposited on the buffer layer; a quantum dot injection layer, the quantum dot injection layer is deposited on the insulating layer 30, and it has good light-emitting properties; a surface cover layer, the surface A capping layer is deposited on the quantum dot implantation layer.

Description

Structure and preparation method of MnInAs/GaAs quantum dot sample with photomagnetic properties

technical field

The invention relates to the technical field of preparation of dilute magnetic semiconductor quantum dots, in particular to a method for preparing a structure with photomagnetic properties containing MnInAs/GaAs quantum dot samples.

Background technique

Diluted magnetic materials are research hotspots in recent years, because they can be used in magneto-optical, information storage, giant magnetoresistance and other applications. III-V semiconductors are the main materials for preparing high-speed electronic devices, lasers, etc., and the development of III-V dilute magnetic semiconductors can combine dilute magnetic properties with the optoelectronic properties of current electronic devices, while for GaAs, InAs, and InSb In other words, Mn ions are close to the atomic radius of cations, and Mn has a large intrinsic magnetic moment, so it is considered to be the first choice for magnetic doping ions in III-V semiconductors. However, the low solubility of Mn in III-V semiconductors made it difficult to prepare III-Mn-V dilute magnetic semiconductors. Until 1989, Hono and others successfully made InMnAs by low-temperature epitaxy. Since then, dilute magnetic semiconductors such as GaMnAs A lot of research has been done on the structure, magnetism, and transport of ions. Generally, the method of preparing III-Mn-V dilute magnetic semiconductor is mainly low-temperature epitaxy. GaMnAs and InMnAs prepared by this method have better lattice periodicity, and the Mn content can even reach more than 10%. It is found that Mn can replace cations in the material. positions, and form acceptors and ionize holes at the same time, and these magnetic Mn ions form ferromagnetic order with holes as the medium to make the material obtain low-temperature ferromagnetism. Through appropriate low-temperature annealing treatment, its Curie transition temperature can reach 150K about.

However, in the low-temperature epitaxial preparation process, the growth conditions determine that it must be grown at a higher As pressure and a lower temperature, so there are a large number of As donors and defects in the material, which makes GaMnAs quantum wells or InMnAs grown by low-temperature epitaxy Quantum dots do not have luminescent properties, which hinders the further application of these materials.

Ion implantation method is a traditional doping method. This method is simple to operate, and the depth of ion doping is controllable. When implanted at higher energy, the dispersion of ions is also better. Currently, ion implantation methods in microelectronics technology application is more common. However, due to the large damage to the substrate caused by ion implantation, it is difficult to guarantee the luminescence performance of the implanted material for optoelectronic materials, such as GaAs.

The invention utilizes the strong luminescence performance of the quantum dot material, and realizes that the quantum dot sample after ion implantation and annealing has luminescence performance. The principle is that after the carriers are captured by the quantum dots, they are restricted in the three-dimensional direction and are not easy to escape, thereby reducing the probability of the carriers (photogenerated carriers or electrically excited carriers) being captured by defects, so that Although the implantation process brings defects to the material, the effect of defects on the luminescence properties of quantum dots is suppressed, so the material still has certain luminescence properties. When the appropriate implant dose and annealing process are selected, the Mn quantum dot material has optical and magnetic properties at the same time. This makes this material more widely used in magneto-optic, spin injection, quantum storage and other fields.

Contents of the invention

The object of the present invention is to provide a method for preparing a structure containing MnInAs/GaAs quantum dot samples with photomagnetic properties, which can be applied in the technical fields of magneto-optic, spin injection, and quantum storage.

The present invention has a structure with photomagnetic properties containing MnInAs/GaAs quantum dot samples, which is characterized in that it comprises:

a substrate;

A buffer layer deposited on the substrate, which can effectively prevent dislocations in the substrate from extending into the epitaxial layer;

an insulating layer deposited on the buffer layer;

A quantum dot injection layer, the quantum dot injection layer is deposited on the insulating layer 30, and it has good luminescent properties;

A surface capping layer is deposited on the quantum dot injection layer.

The material of the substrate is GaAs.

The material of the buffer layer is n+-GaAs, and the thickness of the buffer layer is 500 nanometers.

The material of the insulating layer is GaAs, and the thickness of the insulating layer is 50 nanometers.

The quantum dot injection layer is a three-period quantum dot injection layer, and each period includes two molecular single-layer manganese-containing InAs quantum dot layers and a 20-nanometer-thick manganese-containing GaAs material.

The material of the surface cover layer is GaAs with a thickness of 45 nanometers.

A method for preparing a structure of a MnInAs/GaAs quantum dot sample with photomagnetic properties according to the present invention is characterized in that it comprises the following steps:

Step 1: depositing a buffer layer on the substrate;

Step 2: depositing an insulating layer on the buffer layer;

Step 3: depositing a quantum dot injection layer on the insulating layer;

Step 4: Depositing a surface cap layer on the quantum dot injection layer;

Step 5: using ion implantation to implant Mn ions into the quantum dot implantation layer;

Step 6: Rapidly anneal the injected sample to complete the fabrication of the sample structure.

The material of the substrate is GaAs.

The material of the buffer layer is n+-GaAs, and the thickness of the buffer layer is 500 nanometers.

The material of the insulating layer is GaAs, and the thickness of the insulating layer is 50 nanometers.

The quantum dot injection layer is a three-period quantum dot injection layer, and each period includes two molecular single-layer manganese-containing InAs quantum dot layers and a 20-nanometer-thick manganese-containing GaAs material.

The material of the surface cover layer is GaAs with a thickness of 45 nanometers.

Wherein the temperature when depositing the buffer layer and the insulating layer on the substrate is 580°C.

Wherein the temperature when depositing the quantum dot injection layer on the insulating layer is reduced to 500°C.

The energy of the Mn ion implantation is 160keV, and the implantation dose is between 2×10 ¹⁵ cm ⁻² and 2×10 ¹⁶ cm ⁻² .

The rapid annealing described therein has an annealing temperature between 750° C. and 850° C., a time of 5-30 seconds, and an annealing protective atmosphere of N ₂ .

Significance compared with background technology

The present invention has the following meanings:

The invention prepares quantum dot materials with both magnetic properties and luminous properties for the first time. Compared with the current international low-temperature growth GaMnAs and other materials, the growth method has the characteristics of simple process, and can adjust the emission wavelength of quantum dot samples within a certain range, which is more flexible and adapts to the needs of different purposes.

Description of drawings

In order to further illustrate the specific technical content of the present invention, below in conjunction with embodiment and accompanying drawing detailed description as follows, wherein:

Fig. 1 is the structural representation of the material of quantum dot of the present invention;

Fig. 2 is a schematic diagram of the sample after Mn ion implantation.

Fig. 3 is a photofluorescence spectrum measured at a temperature of 77K after rapid annealing of a quantum dot sample implanted with Mn ions at 850°C.

Fig. 4 is a hysteresis loop diagram measured on a quantum superconducting interferometer at a temperature of 5K after rapid annealing at 850°C for a quantum dot sample implanted with Mn ions.

Detailed ways

Please refer to shown in Fig. 1, a kind of optical magnetic property of the present invention contains the structure of MnInAs/GaAs quantum dot sample, comprises:

A substrate 10, the material of the substrate 10 is GaAs;

A buffer layer 20, this buffer layer 20 is deposited on the substrate 10, it can effectively prevent dislocations in the substrate from possibly extending to the epitaxial layer, the material of the buffer layer 20 is n+-GaAs, the thickness of the buffer layer is 500 nm;

An insulating layer 30, the insulating layer 30 is deposited on the buffer layer 20, the material of the insulating layer 30 is GaAs, and the thickness of the insulating layer 30 is 50 nanometers;

A quantum dot injection layer 40, the quantum dot injection layer 40 is deposited on the insulating layer 30, it has good luminous properties, the quantum dot injection layer 40 is a quantum dot injection layer of 3 periods, each period includes 2 Molecular monolayer of manganese-containing InAs quantum dot layer and 20 nm thick manganese-containing GaAs material;

A surface capping layer 50, the surface capping layer 50 is deposited on the quantum dot injection layer 40, the material of the surface capping layer 50 is GaAs, and the thickness is 45 nanometers.

Please refer to Fig. 1 again and in conjunction with Fig. 2, a method for preparing the structure of a photomagnetic property containing MnInAs/GaAs quantum dot sample of the present invention comprises the following steps:

Step 1: Deposit a buffer layer 20 on the substrate 10, the material of the substrate 10 is GaAs, the material of the buffer layer 20 is n+-GaAs, and the thickness of the buffer layer is 500 nanometers;

Step 2: depositing an insulating layer 30 on the buffer layer 20, the material of the insulating layer 30 is GaAs, and the thickness of the insulating layer 30 is 50 nanometers;

Wherein the temperature when depositing the buffer layer 20 and the insulating layer 30 on the substrate 10 is 580°C;

Step 3: Depositing a quantum dot injection layer 40 on the insulating layer 30, the quantum dot injection layer 40 is a quantum dot injection layer of 3 periods, and each period includes 2 molecular single-layer manganese-containing InAs quantum dot layers and 20 Nano-thick manganese-containing GaAs material;

Wherein the temperature when depositing the quantum dot injection layer 40 on the insulating layer 30 is reduced to 500°C;

Step 4: depositing a surface capping layer 50 on the quantum dot injection layer 40, the material of the surface capping layer 50 is GaAs, and the thickness is 45 nanometers;

Step 5: Implanting Mn ions into the quantum dot implantation layer 40 by means of ion implantation; wherein the energy of Mn ion implantation is 160keV, and the implantation dose is between 2×10 ¹⁵ cm ⁻² and 2×10 ¹⁵ cm ⁻² ;

Step 6: Rapidly anneal the implanted sample at a temperature of 750° C. to 850° C. for 5 to 30 seconds. The annealing atmosphere is N ₂ to complete the fabrication of the sample structure (see FIG. 2 ).

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram of the structure of the original quantum dot sample used in the present invention, that is, three periods of InAs quantum dots grown by self-organization.

The self-organized growth InAs quantum dot samples used are deposited on GaAs substrate 10 by molecular beam epitaxy equipment (MBE). The specific method is to first deposit a 500nm n+-GaAs buffer layer 20 on the substrate 10 at a temperature of 580°C. Due to the precise characteristics of molecular beam epitaxy equipment, the buffer layer 20 has a high degree of lattice integrity and extremely low dislocations. , it can effectively prevent the dislocations in the substrate 10 from extending into the epitaxial layer, especially into the quantum dot injection layer, which will affect the luminescent properties of the Mn-containing quantum dots, so the growth temperature is relatively high, and the selected is 580°C. A 50nm GaAs insulating layer 30 is then deposited on the buffer layer 20 , and the insulating layer 30 can effectively prevent electrons in the buffer layer 20 from diffusing to the quantum dot injection layer 40 after the sample is injected into Mn. After the deposition of the insulating layer 30 is completed, the temperature is lowered to 500° C., and the InAs quantum dot injection layer 40 is deposited for 3 periods. The structure of each layer of quantum dot injection layer 40 includes 2 molecular monolayers of InAs quantum dot layers and a 20 nanometer thick GaAs capping layer (not shown). Since InAs and GaAs have a large lattice mismatch, when depositing If the thickness of InAs is relatively thick, the energy can be reduced through the island structure, thereby forming InAs quantum dots. In the InAs quantum dot layer, two InAs monolayers are deposited first, and then a 20nm GaAs capping layer is grown after a 30-second pause. In order to obtain stronger luminous intensity, three periods of quantum dot layers were deposited to form the quantum dot injection layer 40 . After the quantum dot injection layer 40 is deposited, the temperature is raised to 580°C, and a 45nm thick GaAs capping layer 50 is deposited on the three periods of the quantum dot layer. The thickness of the GaAs capping layer 50 is calculated by combining the implantation energy. When Mn ions are vertically injected into the sample with an energy of 160keV, calculated by computer simulation software, Mn ions will be distributed near the surface of 80 nanometers, and the longitudinal distribution width is 80 nanometers, so Mn ions are basically distributed near the three-layer quantum dots, that is near the quantum dot injection layer 40 .

Figure 2 is a schematic diagram of Mn+ ion distribution after annealing of high-energy Mn ion-implanted samples when quantum dots are doped in the present invention, where the size of the dots does not represent any meaning, and only indicates the location of the distribution of Mn ions.

Mn ion implantation energy is selected as 160keV, and it is vertically implanted into the quantum dot sample at room temperature, ignoring the channel effect in the implantation process, and using computer simulation software to estimate the depth of ion implantation under 160keV implantation energy is 80 nm, and the distribution width is 40 nm. Therefore, it can be seen that the implanted Mn ions are basically distributed near the three-period quantum dot layer, that is, near the quantum dot implantation layer 40 . The injection dose can be between 2×10 ¹⁵ cm ^-2 and 2×10 ¹⁶ cm ^-2 , and the sample will have low-temperature ferromagnetic and optical properties after rapid annealing, and the luminescence and magnetic properties come from the quantum dot injection layer 40 .

Fig. 3 is the PL spectrum measured at a temperature of 77K after rapid annealing at a temperature of 850°C for 5 seconds of a sample E prepared by the present invention (sample Mn implantation dose is 1×10 ¹⁶ cm ^-2 ) (including before implanting Mn ions PL spectrum of the sample).

Since the implantation brings a large number of non-recombination centers, it is necessary to anneal the sample implanted with Mn ions in order to obtain the luminescence of the implanted sample. In order to avoid the formation of MnAs clusters caused by long annealing time, it is necessary to select high temperature rapid annealing. The annealing temperature can be selected from 750° C. to 850° C., and the annealing time is 5-30 seconds. During annealing, _N2 is used as a protective atmosphere, and a clean GaAs sheet can be covered on the sample to reduce the volatilization of As and damage the performance of the sample. Photofluorescence test experiment (PL) equipment is Fourier transform infrared spectrometer (FTIR), the detector is InGaAs photodiode, the excitation light source is argon ion laser, the wavelength is 514nm, the excitation energy is I0=100mW, and the spot diameter is in the range of 100um Inside. Figure 3 shows the PL spectrum of E sample after annealing with implanted Mn ion dose of 1×10 ¹⁶ cm ^-2 . It can be seen from the figure that the PL luminescence performance of the annealed E sample is better, and the peak position is blue-shifted compared with the original sample.

Fig. 4 is a hysteresis loop measured on a quantum superconducting interferometer at a temperature of 5K after rapid annealing of quantum dot samples implanted with Mn ions (a dose of 1E16cm ^-2 ) at 750°C and 850°C.

The magnetic properties are measured on a quantum superconducting interferometer (SQUID), the sample is kept clean, the size is 5×5mm ² , the measurement is non-contact, the direction of the applied magnetic field is parallel to the film surface, and the low-temperature hysteresis Both lines have subtracted the diamagnetic signal of the substrate.

Claims (16)

1. a tool magnetooptical property contains the structure of MnInAs/GaAs quantum dot sample, it is characterized in that, comprising:

One substrate;

One buffer layer, this buffer layer deposition are at substrate, and it can stop the dislocation in the substrate may extend to epitaxial film effectively;

One insulation layer, this insulating layer deposition is on buffer layer;

One quantum dot input horizon, this quantum dot input horizon is deposited on the insulation layer 30, and it has good luminosity;

One surperficial cap rock, this surface cover is deposited upon on the quantum dot input horizon.

2. contain the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 1, it is characterized in that the material of wherein said substrate is GaAs.

3. contain the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 1, it is characterized in that the material of wherein said buffer layer is n+-GaAs, the thickness of this buffer layer is 500 nanometers.

4. contain the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 1, it is characterized in that the material of wherein said insulation layer is GaAs, the thickness of this insulation layer is 50 nanometers.

5. the structure that contains the MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 1, it is characterized in that, wherein said quantum dot input horizon is the quantum dot input horizon for 3 cycles, and each cycle comprises the manganiferous GaAs material of 2 manganiferous InAs quantum dot layers of molecular monolayer and 20 nanometer thickness.

6. contain the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 1, it is characterized in that the material of wherein said surperficial cap rock is GaAs, thickness is 45 nanometers.

7. a tool magnetooptical property contains the preparation method of the structure of MnInAs/GaAs quantum dot sample, it is characterized in that, comprises the steps:

Step 1: on substrate, deposit buffer layer;

Step 2: depositing insulating layer on buffer layer;

Step 3: deposition quantum dot input horizon on insulation layer;

Step 4: deposition surface cap rock on the quantum dot input horizon;

Step 5: adopt ion implantation method, in the quantum dot input horizon, inject the Mn ion;

Step 6: the sample short annealing after will injecting, finish the making of sample structure.

8. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 7, it is characterized in that the material of wherein said substrate is GaAs.

9. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 7, it is characterized in that the material of wherein said buffer layer is n+-GaAs, the thickness of this buffer layer is 500 nanometers.

10. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 7, it is characterized in that the material of wherein said insulation layer is GaAs, the thickness of this insulation layer is 50 nanometers.

11. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 7, it is characterized in that, wherein said quantum dot input horizon is the quantum dot input horizon for 3 cycles, and each cycle comprises the manganiferous GaAs material of 2 manganiferous InAs quantum dot layers of molecular monolayer and 20 nanometer thickness.

12. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 1, it is characterized in that the material of wherein said surperficial cap rock is GaAs, thickness is 45 nanometers.

13. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 7, it is characterized in that wherein the temperature when substrate deposition buffer layer and insulation layer is 580 ℃.

14. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample, it is characterized in that wherein the temperature during deposition quantum dot input horizon is reduced to 500 ℃ on insulation layer by the described tool magnetooptical property of claim 7.

15. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 7, it is characterized in that the energy when wherein Mn is ion implantation is 160keV, implantation dosage is 2 * 10 ¹⁵Cm ^-2To 2 * 10 ¹⁶Cm ^-2Between.

16. contain the preparation method of the structure of MnInAs/GaAs quantum dot sample by the described tool magnetooptical property of claim 7, it is characterized in that, wherein said short annealing, its annealing temperature is between 750 ℃-850 ℃, and the time is 5-30 second, and the annealed protective atmosphere is N ₂

Images