Device and method for measuring nanoscale minority carrier diffusion coefficient of semiconductor materials

Abstract

Provided is a device and method for measuring the diffusion coefficient of nanoscale minority carriers of semiconductor materials. The measuring device includes: a light source assembly for generating monochromatic light and pulsed light; a sample stage for carrying a semiconductor sample or a graphite sample; a conductive needle tip for approaching a surface target area of ​​a semiconductor sample or a graphite sample carried on the sample stage, and spaced apart from the semiconductor sample or the graphite sample; and a scanning Kelvin probe microscope connected to the conductive needle tip, and used to obtain a first contact potential difference and a second contact potential difference on the conductive needle tip approaching the surface target area in the absence of light and when monochromatic light is applied, respectively, and used to obtain a third contact potential difference on the conductive needle tip approaching the graphite sample; a spectral detector for obtaining the lifetime of minority carriers in the surface target area when pulsed light is applied; and a calculation device for calculating the diffusion coefficient according to the first contact potential difference, the second contact potential difference, the third potential difference, and the lifetime of minority carriers.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and in particular, relates to a device and method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials. Background Art

[0002] The common method for measuring the carrier diffusion coefficient of semiconductor materials is the Hall method. This measurement method directly uses the Hall effect to test the carrier mobility, and then uses the Einstein relationship Get the carrier diffusion coefficient.

[0003] However, the above measurement method measures the diffusion coefficient of majority carriers. The performance of semiconductor materials is often subject to the dynamic properties of minority carriers. At present, light-excited measurement conditions are usually used to study the diffusion coefficient of minority carriers in semiconductor materials, such as light-induced transient grating technology (LITG) and time-of-flight technology (TOF). However, the spatial resolution of these two methods is limited, and it is impossible to study the influence of nanoscale structures in semiconductor materials on the diffusion coefficient. In addition, for semiconductor materials, defects such as dislocations have a significant impact on the diffusion coefficient, so there is an urgent need to study the influence of nanoscale structures such as defects on the carrier dynamic properties. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned prior art, an apparatus and method for measuring the nanoscale minority carrier diffusion coefficient of a semiconductor material are provided according to an embodiment of the present invention.

[0005] According to one aspect of an embodiment of the present invention, a semiconductor material nanoscale minority carrier diffusion coefficient measurement device is provided, which includes: a light source component for generating monochromatic light and pulsed light; a sample stage for carrying a semiconductor sample or a graphite sample; a conductive needle tip arranged to be relatively movably arranged with the sample stage, the conductive needle tip being used to approach a surface target area of ​​the semiconductor sample or the graphite sample carried on the sample stage, and being spaced apart from the semiconductor sample or the graphite sample; and a scanning Kelvin probe microscope connected to the conductive needle tip, the scanning Kelvin probe microscope being used to obtain a first contact potential difference and a second contact potential difference on the conductive needle tip approaching the surface target area in the absence of light and when the monochromatic light is applied, respectively, and being used to obtain a third contact potential difference on the conductive needle tip approaching the graphite sample; a spectral detector being used to obtain the lifetime of minority carriers in the surface target area of ​​the semiconductor sample when the pulsed light is applied; and a calculation device being used to calculate the diffusion coefficient of nanoscale minority carriers of the semiconductor sample based on the first contact potential difference, the second contact potential difference, the third contact potential difference, and the lifetime of the minority carriers.

[0006] In an example of the semiconductor material nanoscale minority carrier diffusion coefficient measuring device provided in the above aspect, the calculation device includes: a first calculation unit, used to calculate the sum W+L of the width W and the diffusion length L of the space charge region of the surface target area according to the first contact potential difference and the second contact potential difference; a second calculation unit, used to calculate the width W of the space charge region of the surface target area according to the first contact potential difference and the third contact potential difference; a third calculation unit, used to subtract the width W of the space charge region of the surface target area from the sum W+L of the width W and the diffusion length L of the space charge region of the surface target area to obtain the diffusion length L of the space charge region of the surface target area; a fourth calculation unit, used to calculate the nanoscale minority carrier diffusion coefficient D of the semiconductor sample according to the diffusion length L of the space charge region of the surface target area and the minority carrier lifetime τ.

[0007] In an example of the semiconductor material nanoscale minority carrier diffusion coefficient measurement device provided in the above aspect, the fourth calculation unit is further used to calculate the nanoscale minority carrier diffusion coefficient D of the semiconductor sample according to the diffusion length L of the space charge region of the surface target area and the minority carrier lifetime τ using the following formula 1,

[0008] [Formula 1] D = L 2 / τ.

[0009] In an example of the semiconductor material nanoscale minority carrier diffusion coefficient measurement device provided in the above aspect, the first calculation unit is further used to subtract the first contact potential difference from the second contact potential difference to obtain a surface photovoltage spectrum SPV(λ) of the surface target area, and to fit the width W of the space charge region and the diffusion length L of the surface target area W+L using the following formula 2 and the surface photovoltage spectrum,

[0010] [Formula 2]

[0011] Wherein, k0 is the Boltzmann constant, T is the temperature, α(λ) is the absorption coefficient spectrum of the semiconductor sample, R0 is the surface recombination rate of the semiconductor sample, P(λ) is the photon flux density of the monochromatic light incident on the semiconductor sample, and q is the charge of a single electron.

[0012] In an example of the semiconductor material nanoscale minority carrier diffusion coefficient measurement device provided in the above aspect, the second calculation unit is further used to calculate the band bending V of the semiconductor sample according to the third contact potential difference and the first contact potential difference using the following formula 3: b, and using the following formula 4 and according to the energy band bending V of the semiconductor sample b Calculate the width W of the space charge region of the surface target area,

[0013] [Formula 3] V b =(φ graphene -x semicondictor -eV-φ n ) / e

[0014] [Formula 4]

[0015] Wherein, V is equal to the first contact potential difference minus the third contact potential difference, and the distance between the Fermi surface of the semiconductor sample and the top of the valence band is k0 is the Boltzmann constant, T is the temperature, q is the charge of a single electron, N C is the effective state density of the conduction band of the semiconductor sample, N is the carrier concentration of the semiconductor sample, φ graphene is the work function of the graphite sample, χ semiconductor is the affinity of the semiconductor sample.

[0016] According to another aspect of an embodiment of the present invention, a method for measuring the diffusion coefficient of nanoscale minority carriers of semiconductor materials is provided, which comprises: in the case where no light is incident on the semiconductor sample, a first contact potential difference on the conductive tip is obtained by using a scanning Kelvin probe microscope connected to a conductive tip that has approached a surface target area of ​​the semiconductor sample; in the case where monochromatic light is incident on the semiconductor sample, a second contact potential difference on the conductive tip is obtained by using a scanning Kelvin probe microscope connected to a conductive tip that has approached a surface target area of ​​the semiconductor sample; in the case where pulsed light is incident on the semiconductor sample, a lifetime of minority carriers in the surface target area of ​​the semiconductor sample is obtained by using a spectral detector; in the case where no light is incident on a graphite sample, a third contact potential difference on the conductive tip is obtained by using a scanning Kelvin probe microscope connected to a conductive tip that has approached a surface target area of ​​the graphite sample; and the diffusion coefficient of nanoscale minority carriers of the semiconductor sample is calculated based on the first contact potential difference, the second contact potential difference, the third contact potential difference and the lifetime of the minority carriers.

[0017] In an example of the method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials provided in the above aspect, the diffusion coefficient of the nanoscale minority carriers of the semiconductor sample is calculated based on the first contact potential difference, the second contact potential difference, the third potential difference and the lifetime of the minority carriers, specifically including: calculating the sum W+L of the width W and the diffusion length L of the space charge region of the surface target area based on the first contact potential difference and the second contact potential difference; calculating the width W of the space charge region of the surface target area based on the first contact potential difference and the third contact potential difference; subtracting the width W of the space charge region of the surface target area from the sum W+L of the width W and the diffusion length L of the space charge region of the surface target area to obtain the diffusion length L of the space charge region of the surface target area; calculating the nanoscale minority carrier diffusion coefficient D of the semiconductor sample based on the diffusion length L of the space charge region of the surface target area and the lifetime τ of the minority carriers.

[0018] In an example of the method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials provided in the above aspect, the nanoscale minority carrier diffusion coefficient D of the semiconductor sample is calculated based on the diffusion length L of the space charge region of the surface target region and the lifetime τ of the minority carriers, specifically comprising: using the following formula 1 and calculating the nanoscale minority carrier diffusion coefficient D of the semiconductor sample based on the diffusion length L of the space charge region of the surface target region and the lifetime τ of the minority carriers,

[0019] [Formula 1] D = L 2 / τ.

[0020] In an example of the method for measuring the diffusion coefficient of minority carriers in nanoscale semiconductor materials provided in the above aspect, calculating the sum W+L of the width W and the diffusion length L of the space charge region of the surface target area according to the first contact potential difference and the second contact potential difference specifically includes:

[0021] Subtracting the first contact potential difference from the second contact potential difference to obtain a surface photovoltage spectrum SPV(λ) of the surface target area;

[0022] The sum of the width W of the space charge region and the diffusion length L of the surface target region W+L is fitted using the following formula 2 and the surface photovoltage spectrum:

[0023] [Formula 2]

[0024] Wherein, k0 is the Boltzmann constant, T is the temperature, α(λ) is the absorption coefficient spectrum of the semiconductor sample, R0 is the surface recombination rate of the semiconductor sample, P(λ) is the photon flux density of the monochromatic light incident on the semiconductor sample, and q is the charge of a single electron.

[0025] In an example of the method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials provided in the above aspect, calculating the width W of the space charge region of the surface target area according to the first contact potential difference and the third contact potential difference specifically includes:

[0026] The energy band bending V of the semiconductor sample is calculated according to the third contact potential difference and the first contact potential difference using the following formula 3: b ,

[0027] [Formula 3] V b =(φ graphene -x semicondictor -eV-φ n ) / q

[0028] And using the following formula 4 and according to the energy band bending V of the semiconductor sample b Calculate the width W of the space charge region of the surface target area,

[0029] [Formula 4]

[0030] Wherein, V is equal to the first contact potential difference minus the third contact potential difference, and the distance between the Fermi surface of the semiconductor sample and the top of the valence band is k0 is the Boltzmann constant, T is the temperature, q is the charge of a single electron, N C is the effective state density of the conduction band of the semiconductor sample, N is the carrier concentration of the semiconductor sample, φ graphene is the work function of the graphite sample, χ semiconductor is the affinity of the semiconductor sample.

[0031] Beneficial effects: The present invention greatly improves the spatial resolution of measuring the minority carrier diffusion coefficient of semiconductor materials based on a scanning Kelvin probe microscope, thereby realizing the measurement of the minority carrier diffusion coefficient at the nanometer scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other aspects, features and advantages of the embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0033] Figure 1 is a schematic structural diagram of a device for measuring nanoscale minority carrier diffusion coefficient of semiconductor materials according to an embodiment of the present invention;

[0034] Figure 2 is a unit structure diagram of a computing device of a measuring device according to an embodiment of the present invention;

[0035] Figure 3 is a flow chart of a method for measuring a nanoscale minority carrier diffusion coefficient of a semiconductor material according to an embodiment of the present invention;

[0036] Figure 4 is a schematic diagram of a dislocation generated on a semiconductor sample by nanoindentation according to an embodiment of the present invention in a scanning Kelvin probe microscope;

[0037] Figure 5 Figure a is a schematic diagram of the second contact potential difference and surface photovoltage spectrum that vary with wavelength, Figure b is a schematic diagram of the absorption coefficient spectrum of the semiconductor sample, and Figure c is a schematic diagram of the optical power density of the semiconductor sample;

[0038] Figure 6 is a schematic diagram of fitting minority carrier lifetimes at dislocations of semiconductor materials according to an embodiment of the present invention;

[0039] Figure 7 is a graph of a third contact potential difference of a graphite sample according to an embodiment of the present invention;

[0040] Figure 8 It is a schematic diagram of the sum W+L of the width W of the space charge region and the diffusion length L of the surface target region of the semiconductor sample fitted by the least squares data fitting method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be implemented in many different forms, and the present invention should not be construed as being limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and their practical applications, so that other persons skilled in the art can understand the various embodiments of the present invention and various modifications suitable for specific intended applications.

[0042] As used herein, the term "including" and its variations represent open terms, meaning "including but not limited to". The terms "based on", "according to", etc. mean "based at least in part on", "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0043] Next, before describing the specific embodiments of the present invention, some terms used in the embodiments of the present invention are first introduced in detail.

[0044] Scanning Kelvin probe microscope: Scanning Kelvin probe microscope is a test device based on the atomic force microscope. Its common test mode is to raise the needle tip by tens of nanometers on the basis of the first topography scan, scan along the trajectory of the topography scan, and apply an AC voltage with the same frequency as the topography scan on the conductive probe. By compensating the potential difference between the needle tip and the sample on the needle tip, the mechanical vibration of the probe caused by the AC voltage disappears. The compensated potential difference on the needle tip is the measured contact potential difference CPD. Therefore, the main purpose of the scanning Kelvin probe microscope is to simultaneously obtain the nanoscale topography and the contact potential difference CPD between the needle tip and the sample.

[0045] Width of the surface space charge region: For semiconductors, the periodic structure of the crystal is disrupted by defects on the surface, and the termination of this periodic structure on the surface and the surface chemical changes associated with this termination allow the formation of surface states within the semiconductor band gap. The surface state causes charge transfer between the bulk and the surface of the semiconductor, thus establishing a thermal equilibrium between the two. Therefore, the free carrier density near the semiconductor surface deviates from the equilibrium value in the bulk, which leads to the presence of a surface space charge region (SCR) in the semiconductor.

[0046] Surface photovoltage spectrum: Surface photovoltage spectrum SPV(λ) is a mature non-contact semiconductor characterization technology, which reflects the change of surface potential induced by light. Taking N-type semiconductor as an example, most carriers are electrons, some of which are captured by surface states, forming SCR on the surface. When excitation light (whose energy is greater than the semiconductor band gap) acts on the semiconductor surface, non-equilibrium carriers are generated, and the non-equilibrium carriers are redistributed, changing the surface potential of the sample and forming a surface photovoltage (SPV). The SPV that changes with the wavelength of the incident light is called the surface photovoltage spectrum SPV(λ).

[0047] Time-resolved photoluminescence spectroscopy: Time-resolved photoluminescence spectroscopy (TRPL) is a characterization method for studying carrier lifetime, which reflects the process of carrier recombination. For semiconductors, when the energy of pulsed light is greater than the semiconductor band gap and acts on the semiconductor surface, the semiconductor is excited to produce electron-hole pairs. The process in which free electrons fall from the conduction band to the valence band and radiatively recombine with holes to produce light is called photoluminescence (PL). The intensity I of PL changes with time t, which is called time-resolved photoluminescence spectrum (TRPL) and can be obtained by a time-resolved detector. Exponential fitting based on the decay curve of I(t) can obtain the fluorescence lifetime of the carrier.

[0048] Next, a device and method for measuring nanoscale minority carrier diffusion coefficient of semiconductor materials according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0049] In the following introduction to the semiconductor material nanoscale minority carrier diffusion coefficient measurement device and measurement method according to the embodiment of the present invention, the semiconductor sample used may be, for example, a GaN sample, but the present invention is not limited thereto. Further, a sample electrode is provided on the GaN sample, and its function will be described below.

[0050] Figure 1 Schematic diagram of the structure of a device for measuring nanoscale minority carrier diffusion coefficient of semiconductor materials according to an embodiment of the present invention.

[0051] The semiconductor material nanoscale minority carrier diffusion coefficient measurement device according to an embodiment of the present invention comprises: a light source assembly 100, a sample stage 200, a conductive needle tip 300, a scanning Kelvin probe microscope 400, a spectral detector (or time-resolved detector) 500 and a computing device 600.

[0052] Specifically, the light source assembly 100 is used to generate monochromatic light and pulsed light. In the present embodiment, as an example, the light source assembly 100 includes a monochromatic light source 110, a first shutter switch 120, a reflector 130, a pulsed light source 140, a second shutter switch 150, a first semi-transparent semi-reflective mirror 160, a second semi-transparent semi-reflective mirror 170 and an objective lens 180, and the specific functions of these components will be described below.

[0053] The sample stage 200 is used to carry a semiconductor sample or a graphite sample.

[0054] The conductive needle tip 300 and the sample stage 200 are relatively movable. The conductive needle tip 300 is used to approach the surface target area of ​​the semiconductor sample or the graphite sample carried on the sample stage 200, and the conductive needle tip 300 is spaced apart from the semiconductor sample or the graphite sample. There is a surface space charge region SCR in the surface target area.

[0055] The scanning Kelvin probe microscope 400 is connected to the conductive tip 300. The scanning Kelvin probe microscope is used to obtain a first contact potential difference of the conductive tip 300 approaching the surface target area in the absence of light.

[0056] The scanning Kelvin probe microscope 400 is also used to obtain a second contact potential difference of the conductive needle tip 300 approaching the surface target area when adding monochromatic light. Here, specifically, the monochromatic light source 110 generates monochromatic light, and the monochromatic light passes through the opened first shutter switch 120, and is reflected by the reflector 130 and sequentially passes through the first semi-transparent semi-reflective mirror 160, the second semi-transparent semi-reflective mirror 170 and the objective lens 180 to be incident on the surface target area of ​​the semiconductor sample, so that the monochromatic light can be incident on the surface target area of ​​the semiconductor sample, that is, the above-mentioned addition of monochromatic light to the surface target area of ​​the semiconductor sample.

[0057] The scanning Kelvin probe microscope 400 is also used to obtain a third contact potential difference of the conductive tip 300 approaching the graphite sample in the absence of light. Here, it should be noted that the absence of light means that both the first shutter switch 120 and the second shutter switch 150 are closed, and no light is incident on the sample.

[0058] The spectrum detector 500 is used to obtain the lifetime of minority carriers in the surface target area of ​​the semiconductor sample when the pulse light is applied. Here, specifically, the pulse light source 140 generates the pulse light, and the pulse light passes through the opened second shutter switch 150, and is reflected by the first semi-transparent semi-reflective mirror 160, and sequentially passes through the second semi-transparent semi-reflective mirror 170 and the objective lens 180 to be incident on the surface target area of ​​the semiconductor sample (for example, the same dislocation on the semiconductor sample as the incident monochromatic light), and the pulse light excites the semiconductor sample to produce photoluminescence fluorescence, which passes through the objective lens 180 and is reflected by the second semi-transparent semi-reflective mirror 170 to the spectrum detector 500, so that the spectrum detector 500 obtains the change of the fluorescence signal intensity over time I(t), and exponentially fits the change of the fluorescence signal intensity over time I(t) to obtain the lifetime τ of the minority carriers. In this way, the pulse light can be incident on the surface target area of ​​the semiconductor sample, that is, the above-mentioned addition of pulse light to the surface target area of ​​the semiconductor sample.

[0059] The calculation device 600 is used to calculate the diffusion coefficient of the nanoscale minority carriers of the semiconductor sample according to the first contact potential difference, the second contact potential difference, the third potential difference and the lifetime of the minority carriers.

[0060] Figure 2 is a unit structure diagram of a calculation device of a measurement device according to an embodiment of the present invention.

[0061] Refer to Figure 1 and Figure 2 , the computing device 600 of the measuring device according to the embodiment of the present invention includes: a first computing unit 610 , a second computing unit 620 , a third computing unit 630 and a fourth computing unit 640 .

[0062] Specifically, the first calculation unit 610 is used to calculate the sum W+L of the width W and the diffusion length L of the space charge region of the surface target area according to the first contact potential difference and the second contact potential difference.

[0063] In one example, further, the first calculation unit 610 is further used to subtract the first contact potential difference from the second contact potential difference to obtain a surface photovoltage spectrum SPV(λ) of the surface target area, and use the following formula 1 and the surface photovoltage spectrum to fit the width W of the space charge region of the surface target area and the sum W+L of the diffusion length L,

[0064] [Formula 1]

[0065] Wherein, k0 is the Boltzmann constant, T is the temperature, α(λ) is the absorption coefficient spectrum of the semiconductor sample, R0 is the surface recombination rate of the semiconductor sample, P(λ) is the photon flux density of the monochromatic light incident on the semiconductor sample, and q is the charge of a single electron.

[0066] The second calculation unit 620 is used to calculate the width W of the space charge region of the surface target area according to the first contact potential difference and the third contact potential difference.

[0067] In one example, further, the second calculation unit 620 is used to calculate the band bending V of the semiconductor sample according to the third contact potential difference and the first contact potential difference using the following formula 2: b , and using the following formula 3 and according to the energy band bending V of the semiconductor sample b The width W of the space charge region of the surface target area is calculated.

[0068] [Formula 2] V b =(φ graphene -x semicondictor -qV-φ n ) / e

[0069] [Formula 3]

[0070] Wherein, V is equal to the first contact potential difference minus the third contact potential difference, and the distance between the Fermi surface of the semiconductor sample and the top of the valence band is k0 is the Boltzmann constant, T is the temperature, q is the charge of a single electron, N C is the effective state density of the conduction band of the semiconductor sample, N is the carrier concentration of the semiconductor sample, φ graphene is the work function of the graphite sample, χ semiconductor is the affinity of the semiconductor sample.

[0071] The third calculation unit 630 is used to subtract the width W of the space charge region of the surface target region from the sum W+L of the width W of the space charge region of the surface target region and the diffusion length L to obtain the diffusion length L of the space charge region of the surface target region.

[0072] The fourth calculation unit 640 is used to calculate the nanoscale minority carrier diffusion coefficient D of the semiconductor sample according to the diffusion length L of the space charge region of the surface target area and the minority carrier lifetime τ.

[0073] In one example, further, the fourth calculation unit 640 is used to calculate the nanoscale minority carrier diffusion coefficient D of the semiconductor sample according to the diffusion length L of the space charge region of the surface target area and the lifetime τ of the minority carriers using the following formula 4,

[0074] [Formula 4] D = L 2 / τ.

[0075] The above is a detailed description of the semiconductor material nanoscale minority carrier diffusion coefficient measurement device according to an embodiment of the present invention. Next, a semiconductor material nanoscale minority carrier diffusion coefficient measurement method according to an embodiment of the present invention will be described in detail. Figure 3 The figure is a flow chart of a method for measuring the nanoscale minority carrier diffusion coefficient of a semiconductor material according to an embodiment of the present invention.

[0076] Reference Figure 3 , and refer to Figure 1 and Figure 2 In step S310, when no light is incident on the semiconductor sample, a first contact potential difference on the conductive tip 300 is acquired using a scanning Kelvin probe microscope 400 connected to the conductive tip 300 that has approached a target area on the surface of the semiconductor sample.

[0077] Specifically, in one example, the method for implementing step S310 may include:

[0078] Step 1: Place the prepared semiconductor sample on the sample stage 200, and connect the electrode ED of the semiconductor sample to the grounded sample stage 200 to form an electrical connection with the ground. Otherwise, the accumulation of charges on the surface of the semiconductor sample may affect the contact potential difference on the conductive needle tip 300, and grounding the semiconductor sample can release the accumulated charges.

[0079] Step 2: Start the scanning Kelvin probe microscope 400.

[0080] Step 3: Determine the scanning position: Move the sample stage 200, make the conductive needle tip 300 approach the surface of the semiconductor sample in the approximate test area, use the scanning Kelvin probe microscope 400 to test the morphology and potential map of the semiconductor sample, and place the conductive needle tip 300 in the surface target area of ​​the semiconductor sample. In this embodiment, as an example, the surface target area of ​​the semiconductor sample to be tested is the dislocation generated on the semiconductor sample (such as a GaN sample) by nanoindentation, such as Figure 4 As shown. Among them, Figure 4 FIG. 4 is a schematic diagram of a dislocation generated on a semiconductor sample by nanoindentation in a scanning Kelvin probe microscope according to an embodiment of the present invention.

[0081] Step 4: Stable potential test: Turn on the contact potential difference measurement mode of the scanning Kelvin probe microscope 400 to obtain a stable contact potential difference on the surface of the semiconductor sample.

[0082] Step 5: Introduce monochromatic light, that is, turn on the monochromatic light source 110.

[0083] Step 6: Setting the wavelength: Setting the wavelength of the excitation light of the monochromatic light source 110 to the wavelength to be measured. Here, the wavelength can be set to 400nm-350nm, but the present invention is not limited thereto.

[0084] Step 7: Potential in the absence of light: The first shutter switch 120 is closed, and the first contact potential difference CPD on the conductive tip 300 under darkroom conditions is measured using a scanning Kelvin probe microscope 400 connected to the conductive tip 300 that has approached the target surface area of ​​the semiconductor sample. dark .

[0085] In step S320, when monochromatic light is incident on the semiconductor sample, a second contact potential difference on the conductive tip is acquired by using a scanning Kelvin probe microscope 400 connected to the conductive tip 300 that has approached the target surface area of ​​the semiconductor sample.

[0086] Specifically, in one example, the method for implementing step S320 may include:

[0087] Step 1: Light-adding test: The first shutter switch 120 is turned on, and a scanning Kelvin probe microscope 400 connected to a conductive needle tip 300 that has approached the surface target area of ​​the semiconductor sample is used to test the second contact potential difference CPD under a 400 nm wavelength light (monochromatic light). light ,like Figure 5 As shown in the hollow circle in Figure a.

[0088] Step 2: Change the excitation wavelength within the set wavelength range (e.g., 400nm to 350nm above) along with the light excitation wavelength curve, repeat the light addition test in step 1 above, and obtain the CPD light (λ) follows the light excitation wavelength curve within the set wavelength range, such as Figure 5 As shown in the hollow circle curve in Figure a.

[0089] In step S330, when pulse light is incident on the semiconductor sample, the lifetime of minority carriers in the target surface area of ​​the semiconductor sample is acquired using the spectrum detector 500.

[0090] Specifically, in one example, the method for implementing step S330 may include:

[0091] Step 1: turn off the first shutter switch 120 and turn on the pulse light source 140 and the spectrum detector 500.

[0092] Step 2: Obtain the minority carrier lifetime of the semiconductor sample: Open the second shutter switch 150 to introduce the pulse excitation light generated by the pulse light source 140 into the test position at the same dislocation (the test position corresponding to the first and second contact potential differences in the above test), and excite the semiconductor sample to generate photoluminescence fluorescence. The spectrum detector 500 obtains the change of the fluorescence signal intensity over time I(t), and exponentially fits the change of the fluorescence signal intensity over time I(t) to obtain the minority carrier lifetime τ of the semiconductor sample, as shown in FIG. Figure 6 As shown. Among them, Figure 6 Schematic diagram of fitting minority carrier lifetime at dislocations of semiconductor materials according to an embodiment of the present invention.

[0093] In step S340 , in the case where no light is incident on the graphite sample, a third contact potential difference on the conductive tip 300 is acquired by using the scanning Kelvin probe microscope 400 connected to the conductive tip 300 that has approached the target surface area of ​​the graphite sample.

[0094] Specifically, in one example, the method for implementing step S340 may include:

[0095] Step 1: turn off the first shutter switch 120.

[0096] Step 2: Replace the semiconductor sample with a graphite sample, and obtain a third contact potential difference between the conductive tip 300 and the graphite sample using a scanning Kelvin probe microscope 400 connected to the conductive tip 300 that has approached the surface target area of ​​the graphite sample. like Figure 7 As shown. Among them, Figure 7is a graph of a third contact potential difference of a graphite sample according to an embodiment of the present invention.

[0097] In step S350, a diffusion coefficient of nanoscale minority carriers of the semiconductor sample is calculated based on the first contact potential difference, the second contact potential difference, the third potential difference, and the lifetime of the minority carriers.

[0098] Specifically, in one example, the method for implementing step S350 may include:

[0099] Step 1: Calculate the sum W+L of the width W and the diffusion length L of the space charge region of the surface target area according to the first contact potential difference and the second contact potential difference.

[0100] Here, first, the first calculation unit 610 subtracts the first contact potential difference from the second contact potential difference to obtain a surface photovoltage spectrum SPV(λ) of the surface target area, such as Figure 5 As shown in the hollow square curve in Figure a.

[0101] Secondly, we obtain and: The absorption coefficient spectrum of semiconductor samples can be measured by ellipsometer, such as Figure 5 As shown in Figure b, the optical power density P(λ) of the semiconductor sample where monochromatic light is incident on the semiconductor sample can be measured by an optical power meter, as shown in Figure 5 As shown in Figure c.

[0102] Finally, the first calculation unit 610 uses the above formula 1 and fits the sum W+L of the width W of the space charge region and the diffusion length L of the surface target region by a method such as least squares data fitting, such as: Figure 8 As shown. Among them, Figure 8 is the sum W+L of the width W of the space charge region and the diffusion length L of the surface target region of the semiconductor sample fitted by the least squares data fitting method according to an embodiment of the present invention. Figure 8 In the figure, the wavy solid line is the left side of equation 1, the dotted line is the fitting curve calculated using the right side of equation 1, and the smooth solid line is the light absorption coefficient spectrum.

[0103] Step 2: Calculate the width W of the space charge region of the surface target region according to the first contact potential difference and the third contact potential difference. Here, the second calculation unit 620 can calculate the width W of the space charge region of the surface target region using the above equations 2 and 3.

[0104] Step 3: Subtract the width W of the space charge region of the surface target region from the sum W+L of the width W of the space charge region of the surface target region and the diffusion length L to obtain the diffusion length L of the space charge region of the surface target region. Here, the third calculation unit 630 may subtract the width W of the space charge region of the surface target region from the sum W+L of the width W of the space charge region of the surface target region and the diffusion length L to obtain the diffusion length L of the space charge region of the surface target region.

[0105] Step 4: Calculate the nanoscale minority carrier diffusion coefficient D of the semiconductor sample according to the diffusion length L of the space charge region of the surface target area and the minority carrier lifetime τ. Here, the calculation unit 640 calculates the nanoscale minority carrier diffusion coefficient D of the semiconductor sample using the above formula 4.

[0106] In addition, as another embodiment of the present invention, the nanoscale sample stage 200 can be moved to change the measurement position of the sample (other position points of the dislocation), and the above steps can be repeated to obtain the spatial distribution of the diffusion coefficient of the nanoscale semiconductor sample.

[0107] In summary, the device and method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials according to the embodiments of the present invention greatly improve the spatial resolution of measuring the minority carrier diffusion coefficient of semiconductor materials based on a scanning Kelvin probe microscope, thereby realizing the measurement of the nanoscale minority carrier diffusion coefficient.

[0108] The foregoing describes certain embodiments of the present invention. Other embodiments are within the scope of the following claims.

[0109] The terms "exemplary," "example," and the like used throughout this specification mean "used as an example, instance, or illustration" and do not mean "preferred" or "advantageous" over other embodiments. The detailed description includes specific details for the purpose of providing an understanding of the described techniques. However, these techniques can be implemented without these specific details. In some instances, in order to avoid obscuring the concepts of the described embodiments, well-known structures and devices are shown in block diagram form.

[0110] The optional implementation modes of the embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation modes. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

[0111] The above description of the contents of this specification is provided to enable any person of ordinary skill in the art to implement or use the contents of this specification. Various modifications to the contents of this specification will be apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of protection of the contents of this specification. Therefore, the contents of this specification are not limited to the examples and designs described herein, but are consistent with the widest range of principles and novel features disclosed herein.

Claims

1. A device for measuring the diffusion coefficient of nanoscale minority carriers in semiconductor materials, characterized in that: The measuring device comprises: A light source assembly for generating monochromatic light and pulsed light; A sample stage, used for carrying semiconductor samples or graphite samples; a conductive needle tip, which is movably disposed relative to the sample stage, and is used to approach a surface target area of ​​the semiconductor sample or the graphite sample carried on the sample stage, and is spaced apart from the semiconductor sample or the graphite sample; and A scanning Kelvin probe microscope connected to the conductive needle tip, the scanning Kelvin probe microscope is used to obtain a first contact potential difference and a second contact potential difference on the conductive needle tip approaching the surface target area in the absence of light and when the monochromatic light is applied, respectively, and is used to obtain a third contact potential difference on the conductive needle tip approaching the graphite sample; A spectral detector, used for obtaining the lifetime of minority carriers in a target area on the surface of the semiconductor sample when the pulse light is applied; A calculation device, used for calculating the diffusion coefficient of the nanoscale minority carriers of the semiconductor sample according to the first contact potential difference, the second contact potential difference, the third contact potential difference and the lifetime of the minority carriers; Wherein, the computing device comprises: a first calculation unit, for calculating the width of the space charge region of the surface target area according to the first contact potential difference and the second contact potential difference; W and diffusion length L sum W + L ; a second calculation unit, for calculating the width of the space charge region of the surface target area according to the first contact potential difference and the third contact potential difference; W ; The third calculation unit is used to utilize the width of the space charge region of the surface target area. W and diffusion length L sum W + L Subtract the width of the space charge region of the surface target area W , to obtain the diffusion length of the space charge region of the surface target area L ; The fourth calculation unit is used for calculating the diffusion length of the space charge region of the surface target area according to the diffusion length of the space charge region of the surface target area. L and the minority carrier lifetime τ Calculate the nanoscale minority carrier diffusion coefficient of the semiconductor sample D .

2. The device for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials according to claim 1, characterized in that: The fourth calculation unit is further used to use the following formula 1, and according to the diffusion length of the space charge region of the surface target area L and the minority carrier lifetime τ Calculate the nanoscale minority carrier diffusion coefficient of the semiconductor sample D , [Formula 1] .

3. The semiconductor material nanoscale minority carrier diffusion coefficient measuring device according to claim 1 or 2, characterized in that: The first calculation unit is further used to subtract the first contact potential difference from the second contact potential difference to obtain a surface photovoltage spectrum of the surface target area. SPV (λ), and the width of the space charge region of the surface target area is fitted using the following equation 2 and the surface photovoltage spectrum: W and diffusion length L sum W + L , [Formula 2] , in, k 0 is the Boltzmann constant, T is the temperature, α (λ) is the absorption coefficient spectrum of the semiconductor sample, R 0 is the surface recombination rate of the semiconductor sample, P (λ) is the photon flux density of the monochromatic light incident on the semiconductor sample, q is the charge of a single electron.

4. The semiconductor material nanoscale minority carrier diffusion coefficient measuring device according to claim 1 or 2, characterized in that: The second calculation unit is further used to calculate the band bending of the semiconductor sample according to the third contact potential difference and the first contact potential difference using the following formula 3: V b , and using the following formula 4 and according to the energy band bending of the semiconductor sample V b Calculate the width of the space charge region of the surface target area W， [Formula 3] , [Formula 4] , in, V =Equal to the first contact potential difference minus the third contact potential difference, the distance between the Fermi surface of the semiconductor sample and the top of the valence band , k 0 is the Boltzmann constant, T is the temperature, q is the charge of a single electron, N C is the effective density of states of the conduction band of the semiconductor sample, N is the carrier concentration of the semiconductor sample, is the work function of the graphite sample, is the affinity of the semiconductor sample.

5. A method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials, characterized in that: The measuring method comprises: In the absence of light incident on the semiconductor sample, obtaining a first contact potential difference on the conductive tip by using a scanning Kelvin probe microscope connected to a conductive tip that has approached a target area on the surface of the semiconductor sample; When monochromatic light is incident on the semiconductor sample, a second contact potential difference on the conductive tip is obtained by using a scanning Kelvin probe microscope connected to a conductive tip that has approached a target area on the surface of the semiconductor sample; When pulse light is incident on the semiconductor sample, a spectrum detector is used to obtain the lifetime of minority carriers in a target area on the surface of the semiconductor sample; In the absence of light incident on the graphite sample, obtaining a third contact potential difference on the conductive tip using a scanning Kelvin probe microscope connected to a conductive tip that has approached a target area on the surface of the graphite sample; Calculate the diffusion coefficient of the nanoscale minority carriers of the semiconductor sample according to the first contact potential difference, the second contact potential difference, the third potential difference and the lifetime of the minority carriers; The step of calculating the diffusion coefficient of the nanoscale minority carriers of the semiconductor sample according to the first contact potential difference, the second contact potential difference, the third contact potential difference and the lifetime of the minority carriers specifically includes: The width of the space charge region of the surface target area is calculated according to the first contact potential difference and the second contact potential difference. W and diffusion length L sum W + L ; The width of the space charge region of the surface target area is calculated according to the first contact potential difference and the third contact potential difference. W ; Utilize the width of the space charge region of the surface target area W and diffusion length L sum W + L Subtract the width of the space charge region of the surface target area W , to obtain the diffusion length of the space charge region of the surface target area L ; According to the diffusion length of the space charge region of the surface target area L and the minority carrier lifetime τ Calculate the nanoscale minority carrier diffusion coefficient of the semiconductor sample D .

6. The method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials according to claim 5, characterized in that: The diffusion length of the space charge region of the surface target area L and the minority carrier lifetime τ Calculate the nanoscale minority carrier diffusion coefficient of the semiconductor sample D , specifically comprising: using the following formula 1 and according to the diffusion length of the space charge region of the surface target area L and the minority carrier lifetime τ , calculate the nanoscale minority carrier diffusion coefficient of the semiconductor sample D , [Formula 1] .

7. The method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials according to claim 5 or 6, characterized in that: The width of the space charge region of the surface target area is calculated according to the first contact potential difference and the second contact potential difference. W and diffusion length L sum W + L , specifically including: Subtracting the first contact potential difference from the second contact potential difference to obtain a surface photovoltage spectrum of the surface target area SPV (λ); The width of the space charge region of the surface target area is fitted using the following equation 2 and the surface photovoltage spectrum: W and diffusion length L sum W + L , [Formula 2] , in, k 0 is the Boltzmann constant, T is the temperature, α (λ) is the absorption coefficient spectrum of the semiconductor sample, R 0 is the surface recombination rate of the semiconductor sample, P (λ) is the photon flux density of the monochromatic light incident on the semiconductor sample, q is the charge of a single electron.

8. The method for measuring the nanoscale minority carrier diffusion coefficient of semiconductor materials according to claim 5 or 6, characterized in that: The width of the space charge region of the surface target area is calculated according to the first contact potential difference and the third contact potential difference. W , specifically including: The band bending of the semiconductor sample is calculated according to the third contact potential difference and the first contact potential difference using the following formula 3: V b , [Formula 3] , And using the following formula 4 and according to the energy band bending of the semiconductor sample V b Calculate the width of the space charge region of the surface target area W， [Formula 4] , in, V =Equal to the first contact potential difference minus the third contact potential difference, the distance between the Fermi surface of the semiconductor sample and the top of the valence band , k 0 is the Boltzmann constant, T is the temperature, q is the charge of a single electron, N C is the effective density of states of the conduction band of the semiconductor sample, N is the carrier concentration of the semiconductor sample, is the work function of the graphite sample, is the affinity of the semiconductor sample.

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