A device for obtaining physical parameters of low-dimensional nanodevices through photoelectric response

Abstract

The present invention proposes a device for obtaining physical parameters of low-dimensional nanodevices through photoelectric response, comprising: a light source for irradiating the low-dimensional nanodevice; a current detection unit for detecting the photocurrent generated by the low-dimensional nanodevice under different light intensities, and detecting the dark current generated by the low-dimensional nanodevice under no light source illumination; a light intensity and current relationship acquisition unit for acquiring the relationship between different light intensities and corresponding photocurrents; a parameter acquisition unit for fitting an existing formula for the relationship between light intensity and nanodevice photocurrent according to the light intensity and current relationship to obtain the values ​​of parameters #imgabs0# and #imgabs1#; and a calculation unit for calculating the physical parameters of the low-dimensional nanodevice according to the parameters and other existing formulas, wherein the physical parameters include minority carrier lifetime τ0, surface recombination velocity V srv , depletion region width, doping concentration and mobility.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a device for obtaining physical parameters of low-dimensional nano devices through photoelectric response. Background Art

[0002] Semiconductor nanomaterials have been a promising research area in recent decades due to their applications in optoelectronics. Nanomaterials exhibit properties distinct from those of bulk materials due to quantum confinement and a large surface-to-volume ratio. However, traditional semiconductor characterization methods are difficult for low-dimensional nanodevices. Therefore, a device that can rapidly and non-destructively measure the physical parameters of low-dimensional nanodevices will have significant future applications. Summary of the Invention

[0003] Based on this, in order to solve the above technical problems, a device is provided for obtaining the physical parameters of low-dimensional nanodevices through photoelectric response.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A device for obtaining physical parameters of a low-dimensional nanodevice through photoelectric response, comprising:

[0006] a light source for illuminating the low-dimensional nanodevice;

[0007] a current detection unit, configured to detect the photocurrent generated by the low-dimensional nanodevice when irradiated with different light intensities, and to detect the dark current generated by the low-dimensional nanodevice when no light source is irradiated;

[0008] A light intensity and current relationship acquisition unit is used to acquire the relationship between different light intensities and corresponding photocurrents;

[0009] The parameter acquisition unit is used to fit the formula (1) according to the relationship between light intensity and current to obtain the parameters and The value of

[0010]

[0011] A calculation unit for calculating the The minority carrier lifetime τ0 of the low-dimensional nanodevice is calculated using the value of and formula (2).

[0012]

[0013] The calculation unit also presets the ideal factor η and the parameters based on experience The depletion region width, doping concentration and mobility of the low-dimensional nanodevice are calculated using the values ​​of and formulas (3), (4) and (6).

[0014]

[0015] I dark =μ p pQ ch H ch W ch (4)

[0016]

[0017] In the above formula, I ph is the photocurrent of the nanodevice, P light is the light intensity, is the photocurrent when the depletion region shrinks to zero due to light, that is, the critical photocurrent, η is the ideal factor, the range of the ideal factor is [1,2], usually around 1.5, k is the Boltzmann constant, T is the temperature, q is the unit charge, V bio is the surface potential in the dark field without illumination. The dark field surface potential and the width of the surface depletion region obey the following relationship Here N A is the doping concentration, ε s is the dielectric constant of the semiconductor, W dep is the width of the surface depletion region; is the critical light intensity, that is, the light intensity when the leakage current density is equal to the photocurrent density on the depletion region, α is the light absorption coefficient of the silicon nanowire, is the energy of the photon, H is the physical height of the nanowire, n i is the intrinsic semiconductor electron concentration; I dark is the dark current, W ch is the width of the nanowire channel, H ch is the thickness of the nanowire channel, A ch is the cross-sectional area of ​​the conductive channel, and the expression is the derivative of the cross-sectional area of ​​the conductive channel with respect to the width of the depletion region. “||” means taking the absolute value of the variable between the two vertical lines; μ p is the hole mobility, p is the majority carrier concentration, E ch is the electric field strength.

[0018] Preferably, it also includes a stage located in front of the light source for placing the low-dimensional nanodevice to be tested.

[0019] Preferably, the light source is a laser or a monochromatic light source.

[0020] Preferably, the current in the low-dimensional nanodevice includes dark current and photocurrent.

[0021] Preferably, the low-dimensional nanodevices include nanowires, nanobelts and thin films.

[0022] Preferably, the calculation unit calculates the surface recombination rate V according to the minority carrier lifetime and formula (5) srv

[0023]

[0024] In formula (5), τ b The minority carrier recombination rate in the semiconductor body, SVR is the surface area to volume ratio, τ b is a known parameter

[0025] The device of the present invention can simply and conveniently obtain the physical parameters of low-dimensional nanodevices through photoelectric response, has low equipment requirements, low testing costs, does not require destruction of the nanodevice, and can obtain multiple physical parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the device structure for obtaining physical parameters of low-dimensional nanodevices through photoelectric response according to one embodiment of the present invention.

[0027] Figure 2 Schematic diagram of the current transient response and the relationship between light intensity and current according to an embodiment of the present invention.

[0028] (a) shows the change in current over time when the light is periodically switched on and off. The change in current caused by the light switching is the photocurrent. The light intensity gradually increases with each cycle in the figure. (b) shows the relationship between photocurrent and light intensity. DETAILED DESCRIPTION

[0029] The following will illustrate the implementation of the present invention in conjunction with the drawings in the specification. It should be noted that the implementation methods involved in this specification are not exhaustive and do not represent the only implementation methods of the present invention. The following corresponding embodiments are only for the purpose of clearly illustrating the invention content of the patent of this invention and are not intended to limit its implementation methods. For ordinary technicians in this field, different forms of changes and modifications can be made based on the description of this embodiment. Any obvious changes or modifications that belong to the technical concept and invention content of the present invention are also within the scope of protection of the present invention.

[0030] like Figure 1As shown, the present invention provides an apparatus for obtaining physical parameters of low-dimensional nanodevices through photoelectric response, comprising: a light source 1, a stage 2, a current detection unit 3, a light intensity and current relationship acquisition unit 4, a parameter acquisition unit 5, and a calculation unit 6. Low-dimensional nanodevices include nanowires, nanoribbons, and thin films. In the embodiments of the present invention, the low-dimensional nanodevices are nanowires, fabricated by processing SOI silicon wafers. They can be p-type or n-type nanowires, with any width, for example, 280nm, 240nm, 200nm, or 160nm. The components of the apparatus are described in detail below.

[0031] Light source 1 is used to illuminate the nanowires to be tested. This light source can be a laser or a monochromatic light source. In this embodiment, light source 1 is a commercial laser with a wavelength of, for example, 532 nm. The laser intensity is adjusted by power. Stage 2, located directly below light source 1, is used to place the nanowires to be tested.

[0032] The current detection unit 3 is used to detect the photocurrent generated by the nanowire under different light intensities, and to detect the dark current generated by the nanowire under no light source.

[0033] The light intensity and current relationship acquisition unit 4 is used to acquire the relationship between different light intensities and corresponding photocurrents. Figure 2 (a) shows the change of photocurrent with time under periodic switching light, corresponding to different light intensities. Figure 2 (b) shows the curve of photocurrent changing with light intensity.

[0034] It should be noted that the present invention uses known relationship formulas (1)-(6) for fitting and calculation. Among them, formulas (1)-(3) are the relationship between light intensity and photocurrent of nanodevices (Jiajing He, Kaixiang Chen, Chulin Huang, Xiaoming Wang, Yongning He, Yaping Dan, ACS Nano 14 (2020) 3405-3413). Formula (4) is the relationship between current and electric field intensity under dark field conditions, which is essentially Ohm's law.

[0035] Formulas (1)-(4) are as follows:

[0036]

[0037]

[0038]

[0039] I dark =μ p pQch H ch W ch (4)

[0040] In the above formula (1-4), I ph is the photocurrent of the nanodevice, P light is the light intensity, is the photocurrent when the depletion region shrinks to zero due to light, that is, the critical photocurrent, η is the ideal factor, k is the Boltzmann constant, T is the temperature, q is the unit charge, V bio is the surface potential when there is no light (i.e. dark field). The dark field surface potential and the width of the surface depletion region obey the following relationship Here N A is the doping concentration, ε s is the dielectric constant of the semiconductor, W dep is the width of the surface depletion region; is the critical light intensity, that is, the light intensity when the leakage current density is equal to the photocurrent density on the depletion region, α is the light absorption coefficient of the silicon nanowire, is the energy of the photon, H is the physical height of the nanowire, n i is the intrinsic semiconductor electron concentration; I dark is the dark current, W ch is the width of the nanowire channel (equal to the physical thickness of the nanowire minus the total width of the surface depletion regions on both sides), H ch is the thickness of the nanowire channel (equal to the physical thickness of the nanowire minus the total width of the depletion regions on the upper and lower surfaces), A ch is the cross-sectional area of ​​the conductive material, expressed as is the derivative of the cross-sectional area of ​​the conductive channel with respect to the width of the depletion region. “||” means taking the absolute value of the variable between the two vertical lines; μ p is the hole mobility, p is the majority carrier concentration (in this invention, it is the hole concentration, which is equal to the doping concentration N if the doping impurities are completely ionized or nearly completely ionized). A ), E ch is the electric field intensity. In formula (1), “ln” means taking the natural logarithm of the variable in the brackets.

[0041] Next, the parameter acquisition unit 5 is described. The parameter acquisition unit 5 is used to obtain the relationship between the light intensity and the current obtained in the unit 4 (ie, multiple groups of P light , I ph The value of ) is fitted to formula (1) to obtain the parameters and For example, by illuminating nanowires of different types and widths with light and detecting the current, multiple sets of light intensity and current P are obtained. light , I phThe values ​​of are obtained by fitting formula (1), as shown in Table 1, specifically as shown in columns 3 and 4 of Table 1.

[0042] Table 1

[0043]

[0044]

[0045] Next, the calculation unit 6 is used to calculate the The minority carrier lifetime τ0 and surface recombination velocity V of the low-dimensional nanodevice are calculated using the value of and formula (2). srv Since the parameters have been obtained Substituting the value of into formula (2), and knowing all other parameters, we can obtain the minority carrier lifetime τ0. The calculated τ0 for each case is shown in column 5 of Table 1.

[0046] For the surface recombination rate V srv The calculation unit 6 then calculates the surface recombination rate V according to the minority carrier lifetime τ0 and formula (5) srv .

[0047]

[0048] In formula (5), τ b The minority carrier recombination rate in a semiconductor is a known parameter in the prior art. SVR is the surface-to-volume ratio. srv This is shown in column 6 of Table 1.

[0049] The above has detailed the two physical parameters of nanowires obtained by photoelectric response, namely the minority carrier lifetime τ0 and the surface recombination velocity V srv The following describes how to obtain the other three physical parameters.

[0050] In order to obtain the other three parameters of the nanowire through the photoelectric response, namely the depletion region width W dep , doping concentration p and the corresponding mobility, the present invention introduces the Caughey-Thomas model, which describes the mobility μ(μ of silicon nanowires under the uniform model p ) and the doping concentration p, as shown in Formula 6.

[0051]

[0052] For p-type doped silicon single crystal semiconductor: μ min =47.7cm 2 V-1 s -1 ,μ max =495cm 2 V -1 s -1 ,α1=0.76,N r =6.3×10 16 cm -3 For other semiconductors, these constants will have different values.

[0053] For n-type doped silicon single crystal semiconductor: μ min =65cm 2 V -1 s -1 ,μ max =1330cm 2 V -1 s -1 ,α1=0.72,N r =8.5×10 16 cm -3 For other semiconductors, these constants will have different values.

[0054] In addition, the present invention also assumes that the ideal factor η has a value range of [1, 2], usually around 1.5, and can be fine-tuned based on experience in practical applications.

[0055] The calculation unit is based on the parameters The depletion region width, doping concentration and mobility of the low-dimensional nanodevice are calculated by combining the values ​​of and formulas (3), (4) and (6). For example, by detecting the current of nanowires of different types and widths under light illumination, the depletion region width W of the nanowire is calculated by photoelectric response. dep , doping concentration p (also equal to N A ) and the corresponding mobility μ, as shown in Table 2.

[0056] Table 2

[0057]

[0058] Furthermore, to verify the accuracy of the carrier concentration and mobility inferred from the photoelectric response of the present invention, the present invention conducted Hall effect testing on the nanowires. The Hall effect test was conducted within a magnetic field range of ±2T, a current of less than 100μA, and a room temperature of 300K. The Hall effect test yielded the doping concentration and mobility of the nanowires, the results of which are also listed in Table 2. The values ​​obtained from these Hall effect measurements are not significantly different from the nanowire doping concentration and mobility inferred from the photoelectric effect of the present invention, thus verifying the accuracy of the present invention's device in measuring the physical parameters of low-dimensional nanodevices.

[0059] However, those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A device for obtaining physical parameters of low-dimensional nanodevices through photoelectric response, characterized in that: include: a light source for illuminating the low-dimensional nanodevice; a current detection unit, configured to detect the photocurrent generated by the low-dimensional nanodevice when irradiated with different light intensities, and to detect the dark current generated by the low-dimensional nanodevice when no light source is irradiated; A light intensity and current relationship acquisition unit is used to acquire the relationship between different light intensities and corresponding photocurrents; The parameter acquisition unit is used to fit the formula (1) according to the relationship between light intensity and current to obtain the parameters and The value of A calculation unit for calculating the The minority carrier lifetime τ0 of the low-dimensional nanodevice is calculated using the value of and formula (2). The calculation unit also presets the ideal factor η and the parameters based on experience The depletion region width, doping concentration and mobility of the low-dimensional nanodevice are calculated using the values ​​of and formulas (3), (4) and (6). AND dark =μ p pqE ch H ch IN ch (4) In the above formula, I ph is the photocurrent of the nanodevice, P light is the light intensity, is the photocurrent when the depletion region shrinks to zero due to light, that is, the critical photocurrent, η is the ideal factor, the range of the ideal factor is [1,2], k is the Boltzmann constant, T is the temperature, q is the unit charge, V bio is the surface potential in the dark field without illumination. The dark field surface potential and the width of the surface depletion region obey the following relationship Here N A is the doping concentration, ε s is the dielectric constant of the semiconductor, W dep is the width of the surface depletion region; is the critical light intensity, that is, the light intensity when the leakage current density is equal to the photocurrent density on the depletion region, α is the light absorption coefficient of the silicon nanowire, is the energy of the photon, H is the physical height of the nanowire, n i is the intrinsic semiconductor electron concentration; I dark is the dark current, W ch is the width of the nanowire channel, H ch is the thickness of the nanowire channel, A ch is the cross-sectional area of ​​the conductive channel, and the expression is the derivative of the cross-sectional area of ​​the conductive channel with respect to the width of the depletion region. "||" means taking the absolute value of the variable between the two vertical lines; μ p is the hole mobility, p is the majority carrier concentration, E ch is the electric field strength.

2. The method according to claim 1, characterized in that The value of the ideality factor is 1.

5.

3. The method according to claim 1, characterized in that It also includes a stage, which is located in front of the light source and is used to place the low-dimensional nanodevice to be tested.

4. The method according to claim 3, characterized in that The light source is a laser or a monochromatic light source.

5. The method according to claim 4, characterized in that The current in the low-dimensional nanodevice includes dark current and photocurrent.

6. The method according to claim 5, characterized in that The low-dimensional nanodevices include nanowires, nanobelts and thin films.

7. The method according to claim 6, characterized in that The calculation unit calculates the surface recombination rate V according to the minority carrier lifetime and formula (5): srv In formula (5), τ b The minority carrier recombination rate in the semiconductor body, SVR is the surface area to volume ratio, τ b are known parameters.

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