A photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide

Abstract

The present invention relates to a photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide, comprising: preparing a p-GaAs sample and two pairs of strip electrodes; placing the sample in a vacuum dewar flask, connecting a pair of electrodes with leads, and connecting to a voltage preamplifier; the laser emitted by the laser passes through an attenuator, a chopper, a polarizer, a photoelastic modulator and a lens, so that the laser is vertically incident on the sample; the sample generates a photocurrent under laser irradiation, inputs the voltage preamplifier, extracts the ordinary photocurrent and the circularly polarized light-related photocurrent through the first and second phase-locked amplifiers, respectively, and allows the sample to deflect continuously for a set number of times, and collects current data once each time the set angle changes; applying voltage to the preamplifier and repeating the test once; rotating the sample by 90 degrees, connecting another pair of electrodes with leads, and repeating the above test process; comparing the obtained data, and distinguishing the crystal orientation and crystal orientation according to the size of the signal. The method is conducive to simply, quickly and effectively locating the crystal orientation of p-type gallium arsenide.

Description

Technical Field

[0001] The invention belongs to the technical field of spin electronics, and in particular relates to a photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide. Background Art

[0002] As the feature size of integrated circuits continues to decrease, the difficulty and cost of process development are increasing dramatically. The quantum effects brought by the nanoscale feature size will also cause the device to fail, and Moore's Law will be difficult to maintain. Therefore, a new device principle is urgently needed, and manipulating the spin freedom of electrons to realize new devices and new chip functions has become a research idea.

[0003] The spin diffusion length in semiconductor materials can reach 1000nm. There are fewer carriers in semiconductors, which are suitable for studying the behavior of single electron spins. Semiconductors are selective in absorbing light, so circularly polarized light can be used to inject spin electrons. Conversely, the information carried by the electron spin state can also be transferred to photons for information transmission, realizing optical spin electronics. Among them, III-V semiconductors have unique electrical and optical properties, and have shown important value in optical communications, microwave devices, lighting, displays, photovoltaics, light detection, basic science and other fields. People hope to combine spin electronics with mature semiconductor growth processes and micro-nano processing processes to achieve device integration, so accurate positioning of the crystal orientation is of great significance to the subsequent semiconductor processing. Generally, the positioning of the crystal orientation needs to be tested by a crystal orientation detector, but the testing process of the crystal orientation detector is relatively cumbersome and not suitable for application in large-scale production. Summary of the invention

[0004] The object of the present invention is to provide a photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide, which method is conducive to simply, quickly and effectively locating the crystal orientation of p-type gallium arsenide.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide, comprising the following steps:

[0006] Step S1, using molecular beam epitaxy technology to grow a layer of GaAs doped with Be on a GaAs substrate with a (001) crystal plane, and then growing the doped GaAs along the

[110] and The p-GaAs sample was cut into a square shape along the

[110] and

[110] directions. Two pairs of strip electrodes are made with the crystal orientation facing each other;

[0007] Step S2, placing the sample in a vacuum Dewar flask, and using silver wires as leads to connect two electrodes of one pair of electrodes respectively, connecting the electrode leads to the terminals of the Dewar flask, and then connecting the two electrodes on the sample to the input end of the voltage preamplifier through the terminals of the Dewar flask;

[0008] Step S3, the laser emitted by the laser passes through the attenuator, chopper, polarizer, photoelastic modulator and lens, firstly irradiates the light spot on the midpoint of the line connecting the two electrodes on the sample, and then amplifies the light spot through the lens to cover the entire sample, so that the laser is vertically incident on the sample;

[0009] Step S4: The sample generates a photocurrent under laser irradiation, which is collected by two electrodes and then input into a voltage preamplifier, and respectively input into a first lock-in amplifier and a second lock-in amplifier, and then collected by a data acquisition card; the photocurrent consists of two parts, the first part is a common photocurrent, which is consistent with the chopping frequency of the chopper, extracted by the first lock-in amplifier, and recorded as I PC The second part is the photocurrent associated with circularly polarized light, which is the difference between the photocurrent generated by left-handed circularly polarized light and the photocurrent generated by right-handed circularly polarized light, which is the same as the frequency of the photoelastic modulator, and is extracted by the second lock-in amplifier and recorded as I CPGE ;

[0010] Step S5: Start the motor for driving the vacuum dewar flask to rotate, and let the sample deflect continuously for a set number of times. Collect data once every time the set angle changes. and Where n represents the number of deflections; then a voltage V is applied to the preamplifier, and the above test process is repeated to collect make get

[0011] Step S6, disconnect the lead wire from the electrode, rotate the sample 90°, and connect the two electrodes of another pair of electrodes with the lead wire, and then repeat steps S3-S5 to collect and

[0012] Step S7, by obtaining Comparative analysis was performed to distinguish between

[110] and Crystal direction.

[0013] Furthermore, the thickness of the epitaxial layer of GaAs doped with Be element is in the range of 10 nm to 10 μm.

[0014] Furthermore, the electrodes on the sample are indium electrodes, and are annealed at 400° C. in a vacuum environment for 10 minutes; the two pairs of electrodes are covered with opaque tape to prevent the light spot from hitting the electrodes.

[0015] Furthermore, in step S3, the first harmonic modulation frequency of the photoelastic modulator is 50KHz, the angle between the main axis direction of the photoelastic modulator and the polarization direction of the polarizer is 45°, the phase delay of the photoelastic modulator is the laser wavelength multiplied by 1 / 4; and the chopping frequency of the chopper is 200 to 4000Hz.

[0016] Furthermore, in step S3, the wavelength of the laser corresponds to a photon energy greater than the band gap of p-GaAs, and the laser power is 10 to 260 mW.

[0017] Furthermore, in step S4, the operating frequency of the chopper is input to the reference frequency input terminal of the first phase-locked amplifier, the output terminal of the current preamplifier is connected to the input terminal of the first phase-locked amplifier, the output terminal of the first phase-locked amplifier is connected to the data acquisition card, and the current signal is collected through the data acquisition card; the frequency of the photoelastic modulator at one frequency is input to the reference frequency input terminal of the second phase-locked amplifier, the output terminal of the current preamplifier is connected to the input terminal of the second phase-locked amplifier, the output terminal of the second phase-locked amplifier is connected to the data acquisition card, and the current signal is collected through the data acquisition card.

[0018] Furthermore, in step S5, the motor drives the sample to deflect left and right so that the incident angle of the laser on the sample surface varies between -60° and +60°.

[0019] Furthermore, in step S5, the voltage applied is 0.1-3V.

[0020] Furthermore, in step S7, all collected I CPGE When the incident angle of the laser on the sample surface is in the range of -(30~50)° and (30~50)°, the signal with a larger absolute value is

[110] crystal orientation, and the smaller is Crystal orientation; compare all the collected I PC When the incident angle is between -10° and 10°, the larger the signal value is, the

[110] crystal orientation is, and the smaller the signal value is. Crystal direction.

[0021] Compared with the prior art, the present invention has the following beneficial effects: it provides a photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide, which measures the crystal orientation of p-type gallium arsenide in a simple and easy way, is simple and easy to operate, has low cost, and has strong practicality and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of the method implementation of the embodiment of the present invention.

[0023] Figure 2Schematic diagram of a measurement system for implementing the method in an embodiment of the present invention.

[0024] Figure 3 is the P-type gallium arsenide

[110] crystal orientation and CPGE current variation with angle of crystal orientation.

[0025] Figure 4 is the P-type gallium arsenide

[110] crystal orientation and Photoconductivity of the crystal orientation varies with angle. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0027] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] like Figure 1 , 2 As shown, this embodiment provides a photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide, comprising the following steps:

[0030] Step S1, using molecular beam epitaxy (MBE) to grow a layer of GaAs doped with Be on a GaAs substrate with a (001) crystal plane, and then growing the doped GaAs along the

[110] and The p-GaAs sample was cut into a square shape along the

[110] and

[110] directions. Two pairs of strip electrodes are made with the crystal directions facing each other.

[0031] The thickness of the epitaxial layer of GaAs doped with Be is in the range of 10 nm to 10 μm. In this embodiment, a 2 μm thick epitaxial layer of GaAs doped with Be is grown with a doping density of 5e16 cm 3 Then the doped GaAs is placed along

[110] and The p-GaAs samples were cut into 6×6 mm squares.

[0032] In this embodiment, the electrodes on the sample are indium electrodes, and are annealed at 400° C. in a vacuum environment for 10 minutes; the two pairs of electrodes are covered with opaque tape to prevent the light spot from hitting the electrodes.

[0033] Step S2, placing the sample in a vacuum Dewar flask, and using silver wire as a lead to connect the two electrodes of one pair of electrodes respectively, connecting the electrode leads to the terminal posts of the Dewar flask, and then connecting the two electrodes on the sample to the input end of the voltage preamplifier through the terminal posts of the Dewar flask.

[0034] Step S3, the laser emitted by the laser passes through the attenuation plate, chopper, polarizer, photoelastic modulator and lens, first allowing the light spot to irradiate the midpoint of the line connecting the two electrodes on the sample, and then the light spot is magnified by the lens to cover the entire sample, so that the laser is vertically incident on the sample and the laser incident surface is perpendicular to the line connecting the two electrodes.

[0035] The one-fold modulation frequency of the photoelastic modulator is 50KHz, the angle between the main axis direction of the photoelastic modulator and the polarization direction of the polarizer is 45°, and the phase delay of the photoelastic modulator is the laser wavelength multiplied by 1 / 4. The chopping frequency of the chopper is 200 to 4000 Hz. In this embodiment, the chopping frequency is 240 Hz.

[0036] The wavelength of the laser corresponds to a photon energy greater than the band gap of p-GaAs, and the laser power is 10 to 260 mW. In this embodiment, the laser wavelength is 910 nm and the power is 180 mW.

[0037] Step S4: The sample generates a photocurrent under laser irradiation, which is collected by two electrodes and then input into a voltage preamplifier, and respectively input into a first lock-in amplifier and a second lock-in amplifier, and then collected by a data acquisition card; the photocurrent consists of two parts, the first part is a common photocurrent, which is consistent with the chopping frequency of the chopper, extracted by the first lock-in amplifier, and recorded as I PC The second part is the photocurrent associated with circularly polarized light, which is the difference between the photocurrent generated by left-handed circularly polarized light and the photocurrent generated by right-handed circularly polarized light, which is the same as the frequency of the photoelastic modulator, and is extracted by the second lock-in amplifier and recorded as I CPGE .

[0038] Specifically, the operating frequency of the chopper is input to the reference frequency input terminal of the first phase-locked amplifier, the output terminal of the current preamplifier is connected to the input terminal of the first phase-locked amplifier, the output terminal of the first phase-locked amplifier is connected to the data acquisition card, and the current signal is collected through the data acquisition card; the frequency of the photoelastic modulator at one frequency is input to the reference frequency input terminal of the second phase-locked amplifier, the output terminal of the current preamplifier is connected to the input terminal of the second phase-locked amplifier, the output terminal of the second phase-locked amplifier is connected to the data acquisition card, and the current signal is collected through the data acquisition card.

[0039] Step S5: Start the motor for driving the vacuum dewar flask to rotate, and let the sample deflect continuously for a set number of times. Collect data once every time the set angle changes. and Where n represents the number of deflections; then apply a voltage V of 0.1 to 3V to the preamplifier, and repeat the above test process to collect make get

[0040] In this embodiment, the motor drives the sample to deflect left and right, so that the incident angle of the laser on the sample surface slowly rotates from -60° to +60°.

[0041] Step S6, disconnect the lead wire from the electrode, rotate the sample 90°, and connect the two electrodes of another pair of electrodes with the lead wire, and then repeat steps S3-S5 to collect and

[0042] Step S7: and Input data analysis software for comparative analysis to distinguish

[110] crystal orientation and Crystal direction.

[0043] Specifically, comparing all the collected I CPGE When the incident angle is between -(30~50)° and (30~50)°, the signal with a larger absolute value is

[110] and the signal with a smaller absolute value is Crystal orientation; compare all the collected I PC When the incident angle is between -10° and 10°, the larger the signal value is, the

[110] crystal orientation is, and the smaller the signal value is. Crystal direction.

[0044] In this embodiment, all the collected I CPGE When the incident angle is ±40°, the signal with a larger absolute value is

[110] and the signal with a smaller absolute value is Crystal orientation; compare all the collected I PCWhen the incident angle is 0°, the larger the signal value is, the

[110] crystal direction is, and the smaller the signal value is. Crystal direction.

[0045] Figure 3 In this embodiment, the P-type gallium arsenide

[110] crystal orientation and CPGE current variation with angle of crystal orientation. Figure 3 In the figure, the horizontal axis is the angle from -60 degrees to +60 degrees, the vertical axis is the CPGE current, the unit is nanoampere (nA), the black solid square is the CPGE current of the

[110] crystal orientation, and the black hollow square is CPGE current in the crystal direction.

[0046] Figure 4 In this embodiment, the P-type gallium arsenide

[110] crystal orientation and Photoconductivity of the crystal orientation varies with angle. Figure 4 In the figure, the horizontal axis is the angle from -60 degrees to +60 degrees, the vertical axis is the photoconductivity, the unit is nanoampere (nA), the black solid square is the photoconductivity of the

[110] crystal direction, and the black hollow square is Photoconductivity in the crystal direction.

[0047] like Figure 3 , 4 As shown, the photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide provided in this embodiment is: by exciting the circularly polarized photocurrent effect (CPGE) of P-GaAs with a laser of 910nm wavelength, it is found that the maximum CPGE current of the

[110] crystal orientation is 12.4nA, and the photoconductivity is 2900nA at normal incidence, which is drawn with a solid square in the figure; The maximum CPGE current of the

[110] crystal direction is 2.3 nA, and the photoconductivity is 2510 nA at normal incidence, which is indicated by hollow squares in the figure. The CPGE current and photoconductivity of the two crystal directions are very different. The

[110] crystal direction is much larger than We believe that for the epitaxial P-GaAs layer on the GaAs substrate, doping will cause surface band bending, and the surface layer can be regarded as D 2d When factors such as atomic segregation or asymmetric doping destroy the symmetric interface, the system symmetry is reduced to C 2v In C 2v In the system, Rashba and Dresselhauss spin-orbit coupling effects exist simultaneously. The CPGE current caused by the Rashba spin-orbit coupling effect is called J R , the CPGE current caused by the Dresselhauss spin-orbit coupling effect is called J D When the laser is When the incident light is incident on the

[110] crystal orientation, the CPGE current measured perpendicular to the incident plane, that is, on the

[110] crystal orientation electrode, is expressed as J R +J D When the laser is incident along the

[110] crystal direction, perpendicular to the incident surface, that is, The CPGE current measured on the crystal-oriented electrode is expressed as J R -J D , J R +J D Will be much larger than J R -J D In addition, the photoconductivity measured on the

[110] crystal electrode is much larger than that of Photoconductivity measured in the crystal direction.

[0048] In order to further verify the correctness of this method, the present invention also tested the use of molecular beam epitaxy (MBE) technology to grow a 2-micron thick undoped gallium arsenide layer on a gallium arsenide substrate with a (001) crystal plane, called a semi-insulating gallium arsenide sample. On this sample, we found that the CPGE current signal and photoconductivity of the two crystal directions were very small, and there was no obvious difference. It can be seen that the huge difference between the two crystal directions in P-GaAs is caused by doping, therefore, further proving the correctness of this method.

[0049] In summary, the present invention proposes a simple and easy-to-operate method to distinguish the crystal orientation of p-type gallium arsenide. In this method, the laser passes through a chopper, a polarizer, a photoelastic modulator and a lens in sequence, and irradiates the sample surface at a certain incident angle. At the same time, appropriate forward and reverse voltages are applied to the sample. The ordinary photocurrent and the photocurrent related to circularly polarized light are extracted through a phase-locked amplifier, and then the CPGE current and photoconductivity of the two crystal orientations are obtained by simple calculation. Then, the size is judged. The larger the signal, the

[110] crystal orientation, and the smaller the signal, the Towards.

[0050] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A photoelectric method for distinguishing the crystal orientation of p-type gallium arsenide, characterized in that: The steps include: Step S1, using molecular beam epitaxy technology to grow a layer of GaAs doped with Be on a GaAs substrate with a (001) crystal plane, and then growing the doped GaAs along the [110] and The p-GaAs sample was cut into a square shape along the [110] and [110] directions. Two pairs of strip electrodes are made with the crystal orientation facing each other; Step S2, placing the sample in a vacuum Dewar flask, and using silver wires as leads to connect two electrodes of one pair of electrodes respectively, connecting the electrode leads to the terminals of the Dewar flask, and then connecting the two electrodes on the sample to the input end of the voltage preamplifier through the terminals of the Dewar flask; Step S3, the laser emitted by the laser passes through the attenuator, chopper, polarizer, photoelastic modulator and lens, firstly irradiates the light spot on the midpoint of the line connecting the two electrodes on the sample, and then amplifies the light spot through the lens to cover the entire sample, so that the laser is vertically incident on the sample; Step S4: The sample generates a photocurrent under laser irradiation, which is collected by two electrodes and then input into a voltage preamplifier, and respectively input into a first lock-in amplifier and a second lock-in amplifier, and then collected by a data acquisition card; the photocurrent consists of two parts, the first part is a common photocurrent, which is consistent with the chopping frequency of the chopper, extracted by the first lock-in amplifier, and recorded as I PC The second part is the photocurrent associated with circularly polarized light, which is the difference between the photocurrent generated by left-handed circularly polarized light and the photocurrent generated by right-handed circularly polarized light, which is the same as the frequency of the photoelastic modulator, and is extracted by the second lock-in amplifier and recorded as I CPGE ; Step S5: Start the motor for driving the vacuum dewar flask to rotate, and let the sample deflect continuously for a set number of times. Collect data once every time the set angle changes. and Where n represents the number of deflections; then a voltage V is applied to the preamplifier, and the above test process is repeated to collect make get Step S6, disconnect the lead wire from the electrode, rotate the sample 90°, and connect the two electrodes of another pair of electrodes with the lead wire, and then repeat steps S3-S5 to collect and Step S7, by obtaining and Comparative analysis was performed to distinguish between [110] and Crystal orientation; Compare all the collected I CPGE When the incident angle of the laser on the sample surface is in the range of -(30~50)° and (30~50)°, the signal with a larger absolute value is [110] crystal orientation, and the smaller is Crystal orientation; compare all the collected I PC When the incident angle is between -10° and 10°, the larger the signal value is, the [110] crystal orientation is, and the smaller the signal value is. Crystal direction.

2. The optoelectronic method for distinguishing the crystal orientation of p-type gallium arsenide according to claim 1, characterized in that: The thickness of the epitaxial layer of GaAs doped with Be element is in the range of 10 nm to 10 μm.

3. The optoelectronic method for distinguishing the crystal orientation of p-type gallium arsenide according to claim 1, characterized in that: The electrodes on the sample are indium electrodes and are annealed at 400° C. in a vacuum environment for 10 minutes; two pairs of electrodes are covered with opaque tape to prevent the light spot from hitting the electrodes.

4. The optoelectronic method for distinguishing the crystal orientation of p-type gallium arsenide according to claim 1, characterized in that: In step S3, the one-fold modulation frequency of the photoelastic modulator is 50KHz, the angle between the main axis direction of the photoelastic modulator and the polarization direction of the polarizer is 45°, the phase delay of the photoelastic modulator is the laser wavelength multiplied by 1 / 4; and the chopping frequency of the chopper is 200-4000Hz.

5. The optoelectronic method for distinguishing the crystal orientation of p-type gallium arsenide according to claim 1, characterized in that: In step S3, the wavelength of the laser corresponds to a photon energy greater than the band gap of p-GaAs, and the laser power is 10 to 260 mW.

6. The optoelectronic method for distinguishing the crystal orientation of p-type gallium arsenide according to claim 1, characterized in that: In the step S4, the operating frequency of the chopper is input to the reference frequency input terminal of the first lock-in amplifier, the output terminal of the current preamplifier is connected to the input terminal of the first lock-in amplifier, the output terminal of the first lock-in amplifier is connected to the data acquisition card, and the current signal is collected by the data acquisition card; The frequency of the photoelastic modulator is input into the reference frequency input of the second lock-in amplifier, the output of the current preamplifier is connected to the input of the second lock-in amplifier, the output of the second lock-in amplifier is connected to the data acquisition card, and the current signal is collected through the data acquisition card.

7. The optoelectronic method for distinguishing the crystal orientation of p-type gallium arsenide according to claim 1, characterized in that: In step S5, the motor drives the sample to deflect left and right so that the incident angle of the laser on the sample surface varies between -60° and +60°.

8. The optoelectronic method for distinguishing the crystal orientation of p-type gallium arsenide according to claim 1, characterized in that: In the step S5, the voltage applied is 0.1-3V.

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