A method for evaluating the photoelectric properties of functional regions within semiconductor materials or devices.

Abstract

A method for evaluating the photoelectric properties of internal functional regions in semiconductor materials or devices. The steps are as follows: A) Pre-treating the semiconductor material or device to form a cross-section passing through the functional region to be evaluated, with nanometer-level flatness, and preparing a common electrode that forms an ohmic contact with the semiconductor material; B) Measuring the electrical distribution of the internal functional regions of the test sample under no-light conditions using the electrical measurement mode of a scanning probe microscope; C) Illuminating the semiconductor material or device with a suitable wavelength light source and measuring the electrical distribution of the internal functional regions of the test sample under illumination conditions; D) Comparing, processing, and analyzing the electrical distributions obtained under no-light and illuminated conditions. This method has nanometer-level spatial resolution and high sensitivity, enabling direct acquisition of the photoelectric properties of the core functional regions inside semiconductor materials and devices. It can be used to accurately locate parts affecting their performance and quantify local photoelectric properties, thereby guiding the analysis, prediction, and optimization of their performance.

Description

Technical Field

[0001] This invention relates to a method for evaluating the photoelectric properties of internal functional regions of semiconductor materials or devices, and particularly to a method for evaluating the properties of internal functional regions of semiconductor materials or devices under photoexcitation conditions, such as carrier distribution. Background Technology

[0002] Semiconductor materials and devices play a crucial role in modern electronics and optoelectronics technologies. Their electrical or optoelectronic performance is primarily determined by their internal functional regions. These functional regions include the active region of light-emitting and laser devices, and the absorption, junction, and multiplication regions of detection devices. Within these regions, charge carriers (electrons and holes) undergo transitions between different energy states under the influence of an electric field or photoexcitation, corresponding to photon emission and absorption, thereby achieving energy conversion or information transfer between electro-optical systems. Therefore, the optoelectronic processes within these functional regions, such as the changes in carrier concentration and their microscopic distribution during photoexcitation, dominate the performance of semiconductor materials or devices.

[0003] Currently, the main methods for measuring and evaluating the photoelectric properties of semiconductor materials and devices are laser beam induced photocurrent (LBIC) and scanning photocurrent imaging (SPCM). Both methods utilize a focused light beam to scan and illuminate the surface or functional areas of a semiconductor device, reading its electrical response. Their advantages include non-destructive measurement and spatial resolution and imaging capabilities. However, these methods have several drawbacks: first, they measure the overall photoelectric response of the device under micro-region excitation, rather than directly extracting the local photoelectric response, making it difficult to eliminate the influence of other regions on the photocurrent; second, the resolution is determined by the size of the light spot, typically hundreds of nanometers or larger, while many functional layers of semiconductor optoelectronic devices are only tens or even a few nanometers thick; and third, these methods usually involve in-plane optical scanning, making it difficult to extract photoelectric features along the device's depth, which is unsuitable for analyzing most vertically structured optoelectronic materials and devices. In addition, there are some techniques that can measure the carrier concentration distribution inside semiconductor materials, such as the electrochemical capacitance voltage method (ECV), which can achieve a resolution at the nanometer level. However, the result is the carrier distribution in the material under no light conditions, which cannot directly reflect the local photoelectric properties. Furthermore, such methods are difficult to effectively analyze devices or materials with complex functional structures.

[0004] The scanning capacitance microscopy technique in scanning probe microscopy is characterized by its high spatial resolution of carrier layout; it can provide information on lateral diffusion depth, draw two-dimensional distribution images of carriers, and display changes in the concentration and polarity of photogenerated carriers in the region under the condition of external laser. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the photoelectric properties of internal functional regions of semiconductor materials or devices, which mainly solves the defects of the prior art. This method uses photoexcitation and combines it with local differential capacitance measurement under no-light conditions. By processing the difference or differentiation of the measurement results, the photoelectric information of the internal functional layer is obtained.

[0006] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0007] A method for evaluating the photoelectric properties of functional regions within semiconductor materials or devices, characterized by the following steps:

[0008] A. Pre-process the semiconductor material or device, i.e., the test sample, to form a cross section passing through the functional area to be evaluated, and the cross section has nanometer-level flatness, and prepare a common electrode that forms an ohmic contact with the semiconductor material;

[0009] B. Under conditions of no light, use the electrical measurement mode of a scanning probe microscope to measure the electrical distribution of the internal functional areas of the test sample.

[0010] C. Select a light source of appropriate wavelength to irradiate the semiconductor material or device, and measure the electrical distribution of the internal functional area of ​​the test sample under illumination conditions.

[0011] D. Compare, process, and analyze the electrical distributions obtained under both light and dark conditions.

[0012] The method for evaluating the photoelectric properties of internal functional regions of semiconductor materials or devices is characterized in that: the measurement of the electrical distribution of the test sample in steps A and B includes using a scanning probe microscope, wherein the electrical measurement mode includes conductive atomic force microscopy mode or scanning capacitance microscopy mode.

[0013] The method for evaluating the photoelectric properties of internal functional regions of semiconductor materials or devices is characterized in that: the light-free measurement conditions in step B require moving the light spot on the probe suspension beam of the scanning probe microscope to a distance of at least 90 micrometers from the tip of the probe to ensure that the functional regions of the semiconductor material or device are not excited by the light spot.

[0014] The method for evaluating the photoelectric properties of internal functional regions of semiconductor materials or devices is characterized in that: in step C, a suitable wavelength of light source is selected to irradiate the semiconductor material or device, wherein the wavelength of the light source is selected so that the energy of the irradiated photons is greater than the bandgap of the semiconductor material in the functional region to be measured. Different wavelengths of light source are selected for different functional regions of different semiconductor materials to irradiate the samples respectively, and step C is repeated for measurement.

[0015] The method for evaluating the photoelectric properties of functional regions within semiconductor materials or devices is characterized in that: step D involves comparing, processing, and analyzing the measured electrical distribution results, including performing differential processing on the electrical distribution under conditions of no and no illumination to obtain the net photoelectric signal distribution of the functional region, which reflects the photoelectric efficiency of the functional region of the semiconductor material or device at the nanoscale; or further, numerically differentiating the relative positions of the photoelectric signal distribution of the functional region to obtain the gradient information of the photoelectric characteristics inside the semiconductor material or device, which reflects the effectiveness of the built-in electric field of the functional region on photogenerated carriers (electrons and holes).

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The method of the present invention has nanometer-level spatial resolution and can measure and evaluate semiconductor materials and devices containing micro-nano functional layers or complex structures.

[0018] 2. The method of the present invention has high sensitivity, and the carrier distribution measurement can be realized under low light intensity conditions.

[0019] 3. The method of the present invention can perform difference calculation and differential calculation on the carrier distribution information to obtain the minority carrier distribution information and the gradient distribution information of photogenerated carriers inside the semiconductor material or device.

[0020] 4. The method of the present invention is convenient to implement, has high measurement reliability, and the detection is non-destructive and repeatable. Attached Figure Description

[0021] Figure 1 This is a structural diagram of a detection system using the method of the present invention.

[0022] Figure 2 This is a schematic diagram of the detection system and detection method of Embodiment 1 of the present invention; wherein 101 is the substrate; 102 is the multiplication layer; 103 is the buffer layer; 104 is the absorption layer; 105 is the gradient layer; 106 is the charge layer; 107 is the scanning capacitance microscopy measurement circuit; 108 is the diffusion layer; 109 is the probe cantilever; and 110 is the growth direction.

[0023] Figure 3 This is a differential capacitance distribution diagram of the InGaAS / InP SPAD cross section along the growth direction in Embodiment 1 of the present invention under conditions of no light and light excitation at a wavelength of 1060nm.

[0024] Figure 4 This is a differential capacitance distribution diagram of the InGaAS / InP SPAD cross section along the growth direction in Embodiment 1 of the present invention under conditions of no light and light excitation at a wavelength of 830nm.

[0025] Figure 5This is a distribution diagram of minority carrier differential capacitance under 1060nm photoexcitation conditions in Embodiment 1 of the present invention.

[0026] Figure 6 The first embodiment of this invention shows the gradient distribution of photogenerated carriers under 1060nm photoexcitation conditions. Detailed Implementation

[0027] Please see Figure 1 This invention discloses a method for evaluating the photoelectric properties of functional regions within semiconductor materials or devices, specifically a method for evaluating the carrier distribution and other properties of functional regions within semiconductor materials or devices under photoexcitation conditions. The method comprises the following steps:

[0028] A. Pre-treatment of the test sample, including the fabrication of the dielectric layer and common electrode. First, pre-treatment is performed to create a nanoscale flat surface on the cross-section of the semiconductor material or device. This can be achieved through dissociation along a specific crystal orientation or by cutting and polishing. Second, a flat surface covered by a thin dielectric layer is formed on the surface or sidewalls of the test sample. For group IV semiconductors, this can be achieved through surface oxidation under ultraviolet irradiation in an ozone environment; for group III-V and other compound semiconductors, it can be achieved using the natural oxide layer of the cross-section. Finally, the common electrode is fabricated by vapor deposition or coating with an appropriate metal layer to form an ohmic contact with the test sample.

[0029] B. Measure the electrical distribution of functional regions within a semiconductor material or device under no-light conditions. This step involves measuring the carrier distribution information of the functional regions within the test sample using scanning capacitance microscopy (SCM). This requires moving the light spot on the probe beam of the scanning probe microscope to a distance of at least 90 micrometers from the tip of the probe to ensure that the functional regions of the semiconductor material or device are not excited by the light spot.

[0030] C. Under photoexcitation conditions, measure the electrical distribution of functional regions within semiconductor materials or devices. This step requires measurement under no-light conditions, selecting a light source with photon energy greater than the bandgap of the semiconductor material under test, adjusting the photoexcitation intensity to irradiate the test sample, and ensuring a stable input of the light source to obtain reliable and repeatable measurement results. Different wavelengths of light sources can be selected for irradiation of functional regions of different semiconductor materials.

[0031] D. Based on the electrical distribution results measured under conditions of no light and light excitation, compare, process and analyze them, including difference calculation and differential calculation; thereby obtaining the net photoelectric signal distribution and gradient information of photoelectric characteristics of the functional regions inside the semiconductor material or device.

[0032] The present invention will be described in detail below with reference to the example of obtaining the carrier spatial distribution of an InGaAs / InP single-photon avalanche diode (SPAD) and the accompanying drawings. However, this is not intended to limit the present invention, that is, the present invention is not limited to this example.

[0033] Figure 2 This is a schematic diagram of the detection system and detection method according to Embodiment 1 of the present invention. The test sample, along the growth direction 110, includes a substrate 101, a buffer layer 103, an absorption layer 104, a gradient layer 105, a charge layer 106, a multiplication layer 102, and a diffusion layer 108; wherein: the absorption layer 104 is undoped i-InGaAs; the gradient layer 105 is undoped i-InGaAsP; and the charge layer 106 is n... - -InP; the multiplication layer 102 is i-InP; the diffusion layer 108 is p. + -InP; where the gradient layer is only tens of nanometers, and the charge layer and multiplication layer are both at the submicron level.

[0034] The sample preparation process includes two steps: sample pretreatment and common electrode preparation. A nanoscale flat test surface is prepared on the sample, requiring the root mean square roughness of the test surface to be no more than 0.2 nanometers. For the InGaAs / InP single-photon avalanche diode (SPAD) in this embodiment, an atomically flat test profile can be obtained by mechanically dissociating it along the

[110] crystal direction through the Zn diffusion region. After successful dissociation, the test profile of the sample is placed vertically with the test surface facing upwards, and the bottom is adhered to the iron sheet with conductive silver paste, simultaneously forming the common electrode. In this embodiment, the natural oxide layer of the InGaAs / InP SPAD is directly used as the dielectric layer.

[0035] Using a Pt-coated Si probe, the light spot of a scanning capacitance microscope system was shone onto the probe cantilever 109, located 90 μm from the tip of the probe. The differential capacitance of the test area was measured using the scanning capacitance microscope under no-light conditions, with an AC bias of 1 V. Two-dimensional differential capacitance data of the carrier distribution characteristics of the test area were recorded through circuit 107. (See...) Figure 3 and Figure 4 Differential capacitance curve under no light conditions.

[0036] An infrared spectrometer was used to illuminate the sample. For the i-InGaAs absorption region, the excitation photon energy hv needed to be sufficient to excite interband transitions in the InGaAs absorption layer, but below the InP band gap. In this embodiment, a laser wavelength of 1060 nm was selected. By quantitatively changing the laser incident power density to alter the illumination intensity, and then measuring the carrier distribution information of the device using a scanning capacitance microscope, the following steps were taken: Figure 3 The figure shows 0.07 mW / cm 2Under light intensity conditions, the dC / dV signal in the absorption region changed from negative (-235.4mV) to positive (19.3mV).

[0037] Similar to the steps described above, testing was conducted under conditions of no light and photoexcitation. However, for the i-InP multiplication region, the photon energy hv of the excitation light used must be sufficient to excite interband transitions in the InP multiplication layer. In this embodiment, the laser wavelength used is 830 nm. See [link to documentation]. Figure 4 The figure shows 0.07 mW / cm 2 Under light intensity conditions, the dC / dV signal in the doubling region also changed from -304.5mV to -158.8mV (the lowest value in the doubling region).

[0038] The electrical distribution results obtained from the measurements are compared, processed, and analyzed in order to... Figure 3 The data measured at 1060nm is the raw data. First, the measurement results under illumination and those under no illumination are processed by difference to obtain the differential capacitance distribution of minority carriers. Clearly, the net photoelectric signal is very strong in the absorption region. (See...) Figure 5 Next, the measurement results under illumination are processed by differentiating the growth direction to obtain the gradient distribution of photogenerated carriers in the device. The gradient extrema at positions 1 and 2 in the figure correspond to the extrema of the field strength inside the device. Furthermore, in this embodiment, the gradient layer and charge layer can be clearly identified under 1060nm illumination. Figure 6 . Figure 4 The electrical distribution results obtained from the measurements can also be compared, processed, and analyzed, which will not be elaborated on here.

Claims

1. A method for evaluating the photoelectric properties of functional regions within semiconductor materials or devices, characterized in that: The steps are as follows: A. Pre-process the semiconductor material or device, i.e., the test sample, to form a cross section passing through the functional area to be evaluated, and the cross section has nanometer-level flatness, and prepare a common electrode that forms an ohmic contact with the semiconductor material; B. Under conditions of no light, use the electrical measurement mode of a scanning probe microscope to measure the electrical distribution of the internal functional areas of the test sample. C. Select a light source of appropriate wavelength to irradiate the semiconductor material or device, and measure the electrical distribution of the internal functional area of ​​the test sample under illumination conditions. D. Compare, process, and analyze the electrical distributions obtained under conditions of no light and light. Steps A and B involve measuring the electrical distribution of the test sample, including using a scanning probe microscope, wherein the electrical measurement modes include conductive atomic force microscopy mode or scanning capacitance microscopy mode. The light-free measurement conditions described in step B require moving the light spot on the probe suspension beam in the scanning probe microscope to a distance of at least 90 micrometers from the tip of the probe to ensure that the functional areas of the semiconductor material or device are not excited by the light spot. In step C, the semiconductor material or device is irradiated with a light source of a suitable wavelength. The selection of the light source wavelength is such that the energy of the irradiated photons is greater than the bandgap of the semiconductor material in the functional region to be measured. Different wavelengths of light sources are selected for the functional regions of different semiconductor materials to irradiate the samples respectively, and step C is repeated for measurement. Step D involves comparing, processing, and analyzing the measured electrical distribution results. This includes performing differential processing on the electrical distribution under both illumination and non-illumination conditions to obtain the net photoelectric signal distribution of the functional region, which reflects the photoelectric efficiency of the functional region of the semiconductor material or device at the nanoscale. Alternatively, the relative positions of the photoelectric signal distribution of the functional region can be numerically differentiated to obtain the gradient information of the photoelectric characteristics inside the semiconductor material or device, which reflects the effectiveness of the built-in electric field of the functional region on photogenerated carriers.

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