CN112557343B - Integrated system for detecting defects and electrical properties of high-resistance semiconductor material and testing method thereof - Google Patents
Integrated system for detecting defects and electrical properties of high-resistance semiconductor material and testing method thereof Download PDFInfo
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Abstract
The invention discloses a multifunctional integrated system for detecting defects and electrical properties of a high-resistance semiconductor material and a testing method thereof. The system is based on a photo-generated current transient spectrum testing method, is provided with a low-temperature micro-current transportation constant temperature table, and utilizes programming software such as LABVIEW and the like to autonomously compile corresponding interface programs, measurement and data acquisition processing programs, so that a computer-controlled photo-generated current transient spectrum testing platform is constructed, and the deep energy level defect characterization function of the semiconductor is realized. The system integrates a low-temperature photoconductive test function and an available carrier capture characteristic to analyze a defect behavior function. The method provides a key and reliable characterization means for researching complex deep level defects in the semiconductor material and the influence mechanism of the deep level defects on the electrical performance of the device.
Description
Technical Field
The invention relates to an integrated system for detecting defects and electrical properties of a high-resistance semiconductor material and a testing method thereof, in particular to a multifunctional integrated system and a testing method capable of accurately analyzing specific defects and influences of the specific defects on the electrical properties of the material, which are applied to the technical field of semiconductors.
Background
In the semiconductor field, the evaluation of semiconductor defect characteristics is the most important process for detecting whether semiconductor materials and devices are excellent, and particularly, the existence of deep level defects in semiconductors often plays a decisive role in the performance of devices such as large-scale integrated circuit chips. The resistivity and carrier mobility lifetime product (μτ) of a semiconductor are important parameters for measuring the electrical properties of a material, and various defects in the material have corresponding effects on the material. Impurities and shallow level defects in semiconductors tend to change the concentration of carriers, thereby affecting the resistivity of high-resistance semiconductors; and some deep level defects with energy level positions close to the center of the forbidden band can reduce the carrier mobility life product and deteriorate the electrical performance of the device due to the characteristics of short capture time and long capture time. Therefore, the deep energy level defect and the effect thereof in the crystal are tested, analyzed and researched, and the cause of the deep energy level defect is very important in practical significance, so that the deep energy level defect is researched deeply, the improvement of a corresponding material growth process is facilitated for people, and the application universality of the material is enlarged.
In recent years, the technology for researching deep level defects is endless, and photo-generated current transient spectrum (PICTS) is one of the main technologies for detecting and identifying deep level defects in semiconductors, is different from the common Deep Level Transient Spectrum (DLTS) technology, and takes into consideration the situation that a high-resistance semiconductor is filled with empty energy levels due to lower concentration of carriers in the material, namely, the capturing time is long, fills the application blank of a DLTS test system on the high-resistance semiconductor material, and widens the range requirement of an original deep level transient spectrometer on the forbidden band width of the test material. However, the characterization of defects of the semiconductor material is not fine enough in the prior art, the detection parameters are not rich enough, and the reliability and the accuracy are still to be further improved.
Disclosure of Invention
The invention aims to provide an integrated system for detecting defects and electrical properties of a high-resistance semiconductor material and a testing method thereof, which are used for detecting the defects and the electrical properties of the high-resistance semiconductor material based on the accurate characterization of the defects in the high-resistance semiconductor material and the testing of the electrical properties such as resistivity, mobility life product and the like, so as to research influence effects of different defects on the electrical properties of the high-resistance semiconductor material, in particular to influence mechanisms of carrier transport characteristics. The system is based on a photo-generated current transient spectrum (PICTS) testing method, is provided with a low-temperature micro-current transportation constant temperature table, and utilizes LABVIEW programming software to autonomously compile corresponding interface programs, measurement and data acquisition processing programs, so that a computer-controlled photo-generated current transient spectrum testing platform is constructed, and the deep energy level defect characterization function of a semiconductor is realized; the multiband laser pulse system, the sub-forbidden band light auxiliary excitation system and the method are introduced, and specific defects are excited or saturated through sub-forbidden band auxiliary irradiation in the heating process from low temperature to high temperature according to research requirements, so that the fine characterization of key defects is realized; meanwhile, the system integrates a low-temperature photoconductive test function, and acquires carrier capture characteristics to analyze defect behavior functions. The method provides a key and reliable characterization means and method for researching the defects of the semiconductor material, particularly the complex deep energy level defects in the third-generation wide bandgap semiconductor material and the influence mechanism of the deep energy level defects on the device performance.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
an integrated system for detecting defects and electrical properties of a high-resistance semiconductor material comprises a photo-generated current transient spectrum device for characterizing the defects of the high-resistance semiconductor material, wherein the photo-generated current transient spectrum device comprises a light excitation device, a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller, a direct-current power supply, a current amplifier, an oscilloscope and a computer;
the light excitation device adopts a multiband laser and a chopper, a semiconductor pump laser with a certain wavelength is selected from the multiband laser as an excitation light source according to the forbidden bandwidth of a test material of a high-resistance semiconductor material, an adjustable mechanical beam chopper is matched at the outlet of the laser light source to obtain excitation light with stable laser intensity, stable pulse period and stable light filling time, and the mechanical beam chopper controls a shutter of the laser beam irradiation time period to obtain the required excitation light;
or the light excitation device adopts a pulse laser generator with adjustable wavelength to provide stable and fixed-period laser;
a low-temperature constant-temperature system for placing high-resistance semiconductor materials is arranged in a test system of the whole photo-generated current transient spectrum device, so that a sample chamber is constructed by adopting a cryostat and consists of a temperature controller and the cryostat, the temperature controller is utilized to regulate and control the test temperature in the cryostat, and the temperature rising rate and the acquisition of temperature data are controlled manually or manually; the cryostat outputs an analog signal of photocurrent and a digital signal of real-time temperature, and analysis of defect parameters in a transient spectrum of the photo-generated current is carried out through subsequent signal processing; the two important test part components are a current amplifier for collecting and processing photocurrent transient signals and an oscilloscope for observing the change of photo-generated current in real time respectively; the method comprises the steps of providing a set direct-current bias voltage on a high-resistance semiconductor material and amplifying output current through a current amplifier, so that detection and analysis hardware guarantee and system conditions are provided for analysis and calculation of photo-generated current, and the amplified photo-current signal is recorded and observed through an oscilloscope, and is transmitted to a computer; the interface of each hardware and the processing and analysis of signals are realized through a Labview program software system;
the integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material further comprises at least one of a sub-forbidden band light auxiliary PICTS test system, a low-temperature photoconductive test system and a Hall effect test system; performing defect characterization of the high-resistance semiconductor material by using a photo-generated current transient spectrum device, performing auxiliary characterization of specific defects of the high-resistance semiconductor material by using a sub-forbidden band light auxiliary PICTS test system, and acquiring material carrier transport characteristic information of the high-resistance semiconductor material by using a low-temperature photoconductive test system so as to analyze defect performance; performing hall effect testing of electrical and optical inputs using a hall effect testing system;
the sub-forbidden band light auxiliary PICTS test system comprises an optical excitation device, a sub-forbidden band light radiation device, a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller, a direct-current power supply, a current amplifier, an oscilloscope and a computer; the sub-band gap light auxiliary PICTS test system is based on PICTS test of a photo-generated current transient spectrum device, and based on an original light excitation device serving as an excitation light source, a sub-band gap light radiation device is added, and irradiates a beam of sub-band gap light to continuously irradiate a high-resistance semiconductor material serving as a test sample to obtain influence information of the sub-band gap light on crystal defects; the wavelength of illumination of the sub-forbidden band is changed, so that different defects are controlled to be excited one by one, and influence information and data of single defects on carrier transport performance are obtained;
the low-temperature photoconductive test system comprises a light excitation device, a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller, a direct-current power supply, a current amplifier, an oscilloscope and a computer; the low-temperature photoconductive test system acquires the change of photocurrent and dark current in the heating process according to the experimental principle of direct current photoconductive by combining a low-temperature control device, fits the acquired photocurrent I-V curve by using a Hecht theory method, and calculates and acquires the mobility life product value of the current carrier;
the Hall effect test system comprises a direct current power supply, a magnetic field generating device, a current amplifier, an oscilloscope and a computer, wherein the magnetic field generating device is arranged outside a sample room and is used for applying a magnetic field to a high-resistance semiconductor material arranged in the sample room, the magnetic field generating device provides electric energy through the direct current power supply to generate an adjustable magnetic field, and a temperature-changing Hall effect test is implemented by means of the direct current power supply and a cryostat so as to obtain the resistivity, the carrier life product and the electrical property of a Hall coefficient of the high-resistance semiconductor material; and simultaneously, laser is applied to interfaces of different materials to acquire the electrical property information of the material represented by the optical Hall test of the material.
Preferably, the refrigeration medium of the cryostat is liquid nitrogen or liquid helium.
Preferably, the high-resistance semiconductor material is heated by the heat-conducting metal plate, and the computer regulates and controls the heat output of the heat-conducting metal plate by controlling the temperature controller.
Preferably, for the low-temperature photoconductive test system, sub-forbidden band illumination condition is added in a direct-current photoconductive experiment, and according to photon energy provided by sub-forbidden band lights with different wavelengths and energy level positions corresponding to each defect in a high-resistance semiconductor material, influence information of each defect on carrier transport characteristics is identified one by one, so that influence mechanism information of each defect on the carrier transport characteristics and information of a mechanism capable of effectively improving the carrier transport characteristics in the semiconductor by sub-forbidden band illumination are obtained.
Preferably, the sub-band light radiation device of the sub-band light auxiliary PICTS test system radiates sub-band light with the wavelength of 860-1550nm to continuously irradiate the high-resistance semiconductor material.
Preferably, for a Hall effect test system, ohmic contact electrodes for Hall effect test are adopted, the electrodes are led out and connected to 4 binding posts of a cryostat, the output voltage of a direct-current voltage source is applied to 2 electrodes in the ohmic contact electrodes, the other 2 electrodes read out the Hall voltage, and Hall effect test parameters of a Hall coefficient, resistivity and carrier mobility life product are calculated according to a Hall effect test principle formula; based on the Hall effect test, laser is applied to the surface of the high-resistance semiconductor material to replace a direct-current voltage source, and the Hall voltage before and after the irradiation of the high-resistance semiconductor material and corresponding electrical parameters are tested, and meanwhile, the optical Hall effect and the electrical parameters of lasers with different wavelengths are detected.
The invention relates to a test method for detecting defects and electrical properties of a high-resistance semiconductor material, which is an integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material;
based on a light-generated current transient spectrum, utilizing multi-band laser and sub-forbidden band light to assist in irradiation to obtain inner deep energy level defect information of the high-resistance semiconductor material, and enabling researchers to autonomously design a specific defect characterization experiment according to research objects and tasks by adopting selection of lasers with different bands and selection and combination of different auxiliary sub-forbidden band light wavelengths;
the integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material integrates a low-temperature photoconductive system and a Hall effect test system, acquires the electrical properties of the high-resistance semiconductor material, and acquires the electrical property information of the conductivity type, the resistivity, the carrier life product and the Hall coefficient;
the change of the carrier mobility life product under the irradiation of the sub-forbidden band lights with different wavelengths is compared and analyzed to obtain the effect result of single defect on the carrier transport performance;
meanwhile, the voltage polarity at two ends of the illumination surface is changed to control the properties of main unbalanced carriers flowing through the semiconductor, so that the obtained change of illumination current is mainly generated by the influence of defects on electrons or holes, namely, the electron current is mainly or the hole current is mainly, and then the mobility lifetime product is obtained by fitting a Hecht equation, and is used as the mobility lifetime product of a certain carrier.
The invention discloses a multifunctional integrated system for detecting defects and electrical properties of a high-resistance semiconductor material, which comprises PICTS test, sub-forbidden band light auxiliary PICTS test, low-temperature photoconductive test and Hall effect test, and is used for respectively realizing the high-resistance semiconductor defect characterization function, the accurate characterization function of specific defects, the function of acquiring carrier transport characteristics of the material so as to analyze the defect performance and the Hall effect test function, and integrating and selecting four system structures with corresponding functions. The PICTS test part is mainly used for testing high-resistance materials, so that photocurrent generated by laser irradiation with fixed wavelength on a sample is very small, and an unobvious signal is unfavorable for later analysis, so that by providing a proper direct-current bias voltage on the sample and amplifying output current through a current amplifier, the accuracy of analysis and calculation of photo-generated current is ensured, and the accuracy of experimental results is ensured. The amplified photocurrent signal is recorded and observed through an oscilloscope, and the change of the real-time photo-generated current is transmitted to a computer. Finally, interfaces of all hardware and processing and analyzing signals are realized through a written Labview program. The method is characterized in that sub-band illumination condition is added in a direct current photoconductive experiment, and according to photon energy provided by sub-band light with different wavelengths and energy level positions corresponding to defects in a high-resistance semiconductor material, influence information of the defects on carrier transport characteristics is identified one by one, so that influence mechanism data of the defects on the carrier transport characteristics and a mechanism that the sub-band illumination can effectively improve the transport characteristics in the semiconductor are obtained. PICTS test under the assistance of sub-forbidden band light realizes the accurate characterization function of specific defects, namely, on the basis of PICTS test, a beam of sub-forbidden band light is added to continuously irradiate a test sample on the basis of the original excitation light source so as to explore the influence of the sub-forbidden band light on crystal defects. Under the irradiation of auxiliary sub-forbidden band light, the absorption between intrinsic bands is basically negligible, impurities and deep energy level absorption are dominant, and the efficiency of sub-forbidden band light excitation of free carriers is determined. The wavelength of the illumination of the sub-forbidden band is changed, so that different defects are controlled to be excited one by one, and the influence of single defects on the carrier transport performance is studied. The low-temperature photoconductive test makes the research more detailed and specific, can distinguish the specific influence of defects on the transport performance of different carriers and analyze the influence of different defects on the electrical performance of the material, in particular the influence on the transport performance of the carriers. The Hall effect test is based on a PICTS system, a magnetic field is applied outside a sample chamber with a specific size which is laid out, and the electric properties such as conductivity type, resistivity, carrier life product and Hall coefficient of the high-resistance material are obtained by means of the temperature-changing Hall effect test implemented by a direct-current power supply and a cryostat; and simultaneously, laser is applied to interfaces of different materials to explore the electrical properties of the material to be characterized by the optical Hall test of the material.
Compared with the prior art, the invention has the following obvious prominent substantive features and obvious advantages:
1. the invention utilizes multi-band laser and sub-forbidden band light to assist in irradiation to study the defects of the deep energy level in the semiconductor, and can provide researchers with a specific characterization experiment for specific defects by adopting the selection of lasers with different bands and the selection and combination of different auxiliary sub-forbidden band light wavelengths according to study objects and tasks;
2. the invention integrates a low-temperature photoconductive technology and a Hall effect test to obtain the electrical property of the high-resistance semiconductor material on the basis of a photon-generated current transient spectrum, and is used for researching the influence mechanism of various defects in the material on the electrical property of the material, in particular to the carrier transport characteristic; providing a system platform and a technical method for researching the critical and reliable defect and electrical property detection of the third-generation wide bandgap semiconductor material;
3. the method is simple and feasible, integrates system functions, has relatively low cost and is suitable for popularization and use.
Drawings
FIG. 1 is a schematic diagram of a high resistance semiconductor defect and electrical performance integrated detection system according to a third embodiment of the present invention. And a system structure diagram containing PICTS test, sub-forbidden band light auxiliary PICTS test, low-temperature photoconductive test and Hall effect test.
FIG. 2 is a chart showing the PICTS signal spectrum of a CZT crystal irradiated by light of a light source with a sub-forbidden band of 860nm superimposed on a 730nm excitation light source according to a third embodiment of the present invention. Wherein fig. 2 (a) is a spectrum without sub-bandgap light irradiation; FIG. 2 (b) is a spectrum superimposed with 860nm sub-band-gap light irradiation.
Fig. 3 is a map of defect concentration calculated from the PICTS spectrum shown in fig. 2. Gray bars indicate no sub-band light irradiation, and black bars indicate light irradiation superimposed with 860nm sub-band.
FIG. 4 is a plot of photocurrent generated by 730nm laser irradiation at different temperatures and carrier mobility lifetime obtained by fitting the Hecht equation according to the fourth embodiment of the present invention, wherein FIG. 4 (a) is a plot of photocurrent versus voltage generated by 730nm laser irradiation at different temperatures; fig. 4 (b) is a carrier mobility lifetime product graph.
Detailed Description
The foregoing aspects are further described in conjunction with specific embodiments, examples of which are set forth below:
embodiment one:
in this embodiment, referring to fig. 1, an integrated system for detecting defects and electrical properties of a high-resistance semiconductor material includes a photo-generated current transient spectrum device for characterizing defects of a high-resistance semiconductor material 4, where the photo-generated current transient spectrum device includes a photo-excitation device, a sample chamber, and a signal acquisition processing system; the signal acquisition and processing system comprises a temperature controller 1, a direct current power supply 2, a current amplifier 8, an oscilloscope 9 and a computer 10;
the light excitation device adopts a multiband laser and a chopper 6, a semiconductor pump laser with a certain wavelength is selected from the multiband laser as an excitation light source according to the forbidden bandwidth of a test material of a high-resistance semiconductor material 4, an adjustable mechanical beam chopper is matched at the outlet of the laser light source to obtain excitation light with stable laser intensity, stable pulse period and stable light filling time, and the mechanical beam chopper controls a shutter of the laser beam irradiation time period to obtain the required excitation light;
a low-temperature constant-temperature system for placing a high-resistance semiconductor material 4 is arranged in a test system of the whole photo-generated current transient spectrum device, so that a sample chamber is constructed by adopting a cryostat 5 and consists of a temperature controller 1 and the cryostat 5, the temperature controller 1 is used for carrying out required regulation and control on the test temperature in the cryostat 5, and the temperature rising rate and the acquisition of temperature data are controlled manually or manually; the cryostat 5 outputs an analog signal of photocurrent and a digital signal of real-time temperature, and analysis of defect parameters in a transient spectrum of the photo-generated current is carried out through subsequent signal processing; the two important test part components are a current amplifier 8 for collecting and processing photocurrent transient signals and an oscilloscope 9 for observing the change of photo-generated current in real time; by providing a set direct current bias voltage on the high-resistance semiconductor material 4 and amplifying the output current through the current amplifier 8, detection and analysis hardware guarantee and system conditions are provided for the analysis and calculation of the photo-generated current, and the amplified photo-current signal is recorded and observed through the oscilloscope 9, and the real-time photo-generated current change is transmitted to the computer 10; the interface of each hardware and the processing and analysis of signals are realized through a Labview program software system;
the integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material further comprises at least one of a sub-forbidden band light auxiliary PICTS test system, a low-temperature photoconductive test system and a Hall effect test system; performing defect characterization of the high-resistance semiconductor material 4 by using a photo-generated current transient spectrum device, performing auxiliary characterization of specific defects of the high-resistance semiconductor material 4 by using a sub-forbidden band light auxiliary PICTS test system, and acquiring material carrier transport characteristic information of the high-resistance semiconductor material 4 by using a low-temperature photoconductive test system so as to analyze defect performance; performing hall effect testing of electrical and optical inputs using a hall effect testing system;
the sub-forbidden band light auxiliary PICTS test system comprises an optical excitation device, a sub-forbidden band light radiation device 7, a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller 1, a direct current power supply 2, a current amplifier 8, an oscilloscope 9 and a computer 10; the sub-forbidden band light auxiliary PICTS test system is based on PICTS test of a photo-generated current transient spectrum device, and based on an original light excitation device serving as an excitation light source, a sub-forbidden band light radiation device 7 is added, and the sub-forbidden band light radiation device 7 radiates a beam of sub-forbidden band light to continuously irradiate a high-resistance semiconductor material 4 serving as a test sample so as to obtain influence information of the sub-forbidden band light on crystal defects; the wavelength of illumination of the sub-forbidden band is changed, so that different defects are controlled to be excited one by one, and influence information and data of single defects on carrier transport performance are obtained;
the low-temperature photoconductive test system comprises a light excitation device, a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller 1, a direct current power supply 2, a current amplifier 8, an oscilloscope 9 and a computer 10; the low-temperature photoconductive test system acquires the change of photocurrent and dark current in the heating process according to the experimental principle of direct current photoconductive by combining a low-temperature control device, fits the acquired photocurrent I-V curve by using a Hecht theory method, and calculates and acquires the mobility life product value of the current carrier;
the Hall effect test system comprises a direct current power supply 2, a magnetic field generating device 3, a current amplifier 8, an oscilloscope 9 and a computer 10, wherein the magnetic field generating device 3 is arranged outside a sample room and applies a magnetic field to a high-resistance semiconductor material 4 arranged in the sample room, the magnetic field generating device 3 provides electric energy through the direct current power supply 2 to generate an adjustable magnetic field, and the temperature-changing Hall effect test is implemented by means of the direct current power supply 2 and a cryostat 5 to obtain the resistivity, the carrier life product and the electrical property of a Hall coefficient of the high-resistance semiconductor material 4; and simultaneously, laser is applied to interfaces of different materials to acquire the electrical property information of the material represented by the optical Hall test of the material.
The embodiment is based on the system to obtain accurate characterization of defects in the high-resistance semiconductor material and test electrical properties such as resistivity, mobility service life product and the like, so as to research influence effects of different defects on the electrical properties of the high-resistance semiconductor material, in particular to influence mechanisms of carrier transport characteristics. The system of the embodiment is based on a photo-generated current transient spectrum (PICTS) testing method, is provided with a low-temperature micro-current transportation constant temperature table, and utilizes LABVIEW programming software to autonomously compile corresponding interface programs, measurement and data acquisition processing programs, so that a computer-controlled photo-generated current transient spectrum testing platform is constructed, and the deep energy level defect characterization function of a semiconductor is realized; the multiband laser pulse system, the sub-forbidden band light auxiliary excitation system and the method are introduced, and specific defects are excited or saturated through sub-forbidden band auxiliary irradiation in the heating process from low temperature to high temperature according to research requirements, so that the fine characterization of key defects is realized; meanwhile, the system integrates a low-temperature photoconductive test function, and acquires carrier capture characteristics to analyze defect behavior functions. The method provides a key and reliable characterization means and method for researching the defects of the semiconductor material, particularly the complex deep energy level defects in the third-generation wide bandgap semiconductor material and the influence mechanism of the deep energy level defects on the device performance.
Embodiment two:
this embodiment is substantially the same as the first embodiment, and is characterized in that:
in this embodiment, referring to fig. 1, a test method for detecting defects and electrical properties of a high-resistance semiconductor material is provided, and the integrated system for detecting defects and electrical properties of a high-resistance semiconductor material according to the first embodiment is utilized;
based on a light-generated current transient spectrum, utilizing multi-band laser and sub-forbidden band light to assist in irradiation to obtain inner deep energy level defect information of the high-resistance semiconductor material, and enabling researchers to autonomously design a specific defect characterization experiment according to research objects and tasks by adopting selection of lasers with different bands and selection and combination of different auxiliary sub-forbidden band light wavelengths;
the integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material integrates a low-temperature photoconductive system and a Hall effect test system, acquires the electrical properties of the high-resistance semiconductor material, and acquires the electrical property information of the conductivity type, the resistivity, the carrier life product and the Hall coefficient;
the change of the carrier mobility life product under the irradiation of the sub-forbidden band lights with different wavelengths is compared and analyzed to obtain the effect result of single defect on the carrier transport performance;
meanwhile, the voltage polarity at two ends of the illumination surface is changed to control the properties of main unbalanced carriers flowing through the semiconductor, so that the obtained change of illumination current is mainly generated by the influence of defects on electrons or holes, namely, the electron current is mainly or the hole current is mainly, and then the mobility lifetime product is obtained by fitting a Hecht equation, and is used as the mobility lifetime product of a certain carrier.
The PICTS hardware structure is assembled by the optical excitation device, the sample chamber and the signal acquisition processing system, the interface and the signal processing program of each hardware are realized by the written Labview program, the PICTS test platform is realized, and meanwhile, the excitation light source and the auxiliary sub-forbidden band light source which can be flexibly combined are provided, so that the low-temperature photoconductive test function is integrated. In addition, a magnetic field adjustable magnet is provided, and a Hall effect testing system is integrated. The method is based on a photo-generated current transient spectrum (PICTS) testing method, is provided with a low-temperature micro-current transportation constant temperature table, and utilizes programming software such as LABVIEW and the like to autonomously compile corresponding interface programs, measurement and data acquisition processing programs, so that a computer-controlled photo-generated current transient spectrum testing platform is constructed, and the deep energy level defect characterization function of a semiconductor is realized; the multiband laser pulse system and the sub-forbidden band light auxiliary excitation technology are introduced, and specific defects can be excited or saturated through sub-forbidden band auxiliary irradiation in the heating process from low temperature to high temperature according to research requirements, so that the fine characterization of key defects is realized; meanwhile, the system integrates a low-temperature photoconductive test function, and can acquire carrier capture characteristics to analyze defect behavior functions. The method provides a key and reliable characterization means and method for researching the defects of the semiconductor material, particularly the complex deep energy level defects in the third-generation wide bandgap semiconductor material and the influence mechanism of the deep energy level defects on the electrical performance of the device.
Embodiment III:
this embodiment is substantially identical to the previous embodiment, except that:
in this embodiment, referring to the PICTS test and the sub-band light assisted irradiation PICTS test in fig. 1, in the PICTS characterization semiconductor deep level defect test system, a beam of sub-band light with wavelength of 860nm is added based on the original 730nm excitation light source to continuously irradiate the test sample, the detection object is a high-resistance compound semiconductor Cadmium Zinc Telluride (CZT) crystal, the PICTS signal spectrum under the condition that the sub-band light is not added is shown in fig. 2 (a), when we irradiate a beam of laser with wavelength of 860nm to the crystal surface to perform PICTS defect characterization, the signal spectrum is shown in fig. 2 (b), and the defect concentration of the CZT is calculated to have obvious change, as shown in fig. 3. As can be seen from fig. 3, under the condition of 860nm subforbidden band light irradiation, the concentrations of four defects except for impurity defects with energy level positions of 0.08eV are obviously reduced, so that it is considered that the subforbidden band light energy excites all defect energy levels with activation energy smaller than photon energy, electrons or holes in the defect energy levels are transited through absorbing photon energy, and are re-excited into conduction bands or valence bands, and the ionization state of the defects is changed, so that the defect concentration obtained by PICTS detection is changed. Therefore, the wavelength of the illumination of the sub-forbidden band is changed, so that different defects are controlled to be excited one by one, and the influence of single defects on the carrier transport performance is studied.
Embodiment four:
this embodiment is substantially identical to the previous embodiment, except that:
in this embodiment, according to the position of the CZT crystal defect level obtained by the PICTS test system, the experiment selects sub-forbidden band lights with wavelengths of 860nm, 480 nm,1064nm,1342nm and 1550nm to be respectively added into the direct current photoconductive experiment for irradiation, and the 1342nm sub-forbidden band light corresponds to the CZT valence band to Te cd 2+ The 1064nm sub-bandgap light corresponds to a valence band peak to Te sp The 980nm sub-bandgap light corresponds to the conduction band bottom to V cd 2- Corresponding to 860nm is conduction band bottom to (In cd + -V cd 2- ) - Is a function of the energy of the (c). The effect result of single defect on the carrier transport performance can be obtained by comparing and analyzing the change of the carrier mobility life product under the irradiation of the sub-forbidden band lights with two adjacent wavelengths. Meanwhile, the voltage polarities at the two ends of the illumination surface are changed, the properties of main unbalanced carriers flowing through the crystal are controlled as shown in fig. 4, so that the obtained illumination current changes are mainly generated by the influence of defects on electrons or holes, namely, the electron current is mainly or the hole current is mainly, and the mobility life product obtained by fitting a Hecht equation can be used as the mobility life product of a certain carrier, so that the research is more detailed and concrete, and the concrete influence of the defects on the transport properties of different carriers can be distinguished and analyzed.
Fifth embodiment:
this embodiment is substantially identical to the previous embodiment, except that:
in the embodiment, according to the PICTS test system, a magnetic field with a magnetic field of 1T is applied, an ohmic contact electrode for Hall effect test is prepared on the surface of a regular rectangular CZT wafer polished by a physical-chemical-mechanical polishing (CMP) by using a gold chloride solution, the electrode is led out and connected to 4 binding posts of a cryostat, a direct-current voltage source is adjusted to 50V, the direct-current voltage source is applied to 2 electrodes, the other 2 electrodes read out Hall voltages, and parameters such as CZT Hall coefficient, resistivity, carrier mobility lifetime product and the like are calculated according to a Hall effect test principle formula. Based on the test, laser is applied to the surface of the wafer to replace a direct-current voltage source, the Hall voltage before and after illumination and corresponding electrical parameters are tested, and the optical Hall effect and the electrical parameters of lasers with different wavelengths are explored.
The Hall effect test is based on a PICTS system, a magnetic field is applied outside a sample chamber with a specific size which is laid out, and the electric properties such as conductivity type, resistivity, carrier life product and Hall coefficient of the high-resistance material are obtained by means of the temperature-changing Hall effect test implemented by a direct-current power supply and a cryostat; and simultaneously, laser is applied to interfaces of different materials to explore the electrical properties of the material to be characterized by the optical Hall test of the material.
Example six:
this embodiment is substantially identical to the previous embodiment, except that:
in this embodiment, the light excitation device of the light-generated current transient spectrum device adopts a pulse laser generator with adjustable wavelength to provide stable and fixed-period laser, so as to realize excitation light with stable laser intensity, stable pulse period and stable light filling time, and provide laser irradiation experimental conditions for the light-generated current transient spectrum.
Embodiment seven:
this embodiment is substantially identical to the previous embodiment, except that:
in this embodiment, the refrigeration medium of the cryostat 5 is liquid nitrogen or liquid helium. The high-resistance semiconductor material 4 is heated by the heat-conducting metal plate, and the computer 10 regulates and controls the heat output of the heat-conducting metal plate by controlling the temperature controller 1.
In this embodiment, the sub-band light radiation device 7 of the sub-band light auxiliary PICTS test system irradiates sub-band light with a wavelength of 860-1550nm to continuously irradiate the high-resistance semiconductor material 4.
The embodiment provides effective equipment guarantee for realizing temperature field control corresponding to test conditions, and provides proper conditions of a sub-forbidden band light wavelength range for sub-forbidden band light auxiliary PICTS test.
Example eight:
this embodiment is substantially identical to the previous embodiment, except that:
in this embodiment, for the low-temperature photoconductive test system, sub-band illumination conditions are added in the dc photoconductive experiment, and according to photon energy provided by sub-band light with different wavelengths and energy level positions corresponding to each defect in the high-resistance semiconductor material 4, influence information of each defect on carrier transport characteristics is identified one by one, so as to obtain influence mechanism information of each defect on carrier transport characteristics and information of a mechanism by which sub-band illumination can effectively improve the carrier transport characteristics in the semiconductor. The embodiment optimizes the sub-forbidden band light assisted PICTS test method and realizes accurate characterization of specific defects.
In summary, the multifunctional integrated system for detecting defects and electrical properties of a high-resistance semiconductor material according to the above embodiments, and a testing method for obtaining accurate characterization of defects in the high-resistance semiconductor material and electrical properties such as resistivity, mobility lifetime product and the like based on the system, thereby researching the influence effect of different defects on the electrical properties of the high-resistance semiconductor material, especially the influence mechanism of carrier transport characteristics. The system is based on a photo-generated current transient spectrum PICTS test method, is provided with a low-temperature micro-current transportation constant temperature table, and utilizes LABVIEW programming software to autonomously compile corresponding interface programs, measurement and data acquisition processing programs, so that a computer-controlled photo-generated current transient spectrum test platform is constructed, and the deep energy level defect characterization function of a semiconductor is realized; the multiband laser pulse system and the sub-forbidden band light auxiliary excitation technology are introduced, and specific defects can be excited or saturated through sub-forbidden band auxiliary irradiation in the heating process from low temperature to high temperature according to research requirements, so that the fine characterization of key defects is realized; meanwhile, the system integrates a low-temperature photoconductive test function, and can acquire carrier capture characteristics to analyze defect behavior functions. The method provides a key and reliable characterization means and method for researching the defects of the semiconductor material, particularly the complex deep energy level defects in the third-generation wide bandgap semiconductor material and the influence mechanism of the deep energy level defects on the electrical performance of the device.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the embodiments described above, and various changes, modifications, substitutions, combinations or simplifications made under the spirit and principles of the technical solution of the present invention can be made according to the purpose of the present invention, and all the changes, modifications, substitutions, combinations or simplifications should be equivalent to the substitution, so long as the purpose of the present invention is met, and all the changes are within the scope of the present invention without departing from the technical principles and the inventive concept of the present invention.
Claims (7)
1. The integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material comprises a light-generated current transient spectrum device, and is characterized by the defects of the high-resistance semiconductor material (4), and is characterized in that: the light-generated current transient spectrum device comprises a light excitation device, a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller (1), a direct current power supply (2), a current amplifier (8), an oscilloscope (9) and a computer (10);
the light excitation device adopts a multiband laser and a chopper (6), a semiconductor pump laser with a certain wavelength is selected from the multiband laser as an excitation light source according to the forbidden bandwidth of a test material of a high-resistance semiconductor material (4), an adjustable mechanical beam chopper is matched at the outlet of the laser light source to obtain excitation light with stable laser intensity, a pulse period and stable light filling time, and the mechanical beam chopper controls a shutter of the laser beam irradiation time period to obtain the required excitation light;
or the light excitation device adopts a pulse laser generator with adjustable wavelength to provide stable and fixed-period laser;
a low-temperature constant-temperature system for placing a high-resistance semiconductor material (4) is arranged in a test system of the whole photo-generated current transient spectrum device, so that a sample chamber is constructed by adopting a low-temperature thermostat (5), the sample chamber consists of a temperature controller (1) and the low-temperature thermostat (5), the temperature controller (1) is used for carrying out required regulation and control on the test temperature in the low-temperature thermostat (5), and the temperature rising rate and the acquisition of temperature data are controlled manually or manually; the cryostat (5) outputs an analog signal of photocurrent and a digital signal of real-time temperature, and analysis of defect parameters in a photogenerated current transient spectrum is carried out through subsequent signal processing; wherein the two important test part components are a current amplifier (8) for collecting and processing photocurrent transient signals and an oscilloscope (9) for observing the change of photo-generated current in real time; by providing a set direct current bias voltage on the high-resistance semiconductor material (4) and amplifying the output current through a current amplifier (8), detection and analysis hardware guarantee and system conditions are provided for the analysis and calculation of the photo-generated current, and the amplified photo-current signal is recorded and observed through an oscilloscope (9) and transmitted to a computer (10); the interface of each hardware and the processing and analysis of signals are realized through a Labview program software system;
the integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material further comprises a sub-forbidden band light auxiliary PICTS test system, a low-temperature photoconductive test system and a Hall effect test system; performing defect characterization of the high-resistance semiconductor material (4) by using a photo-generated current transient spectrum device, performing auxiliary characterization of the defect of the high-resistance semiconductor material (4) by using a sub-forbidden band light auxiliary PICTS test system, and acquiring material carrier transport characteristic information of the high-resistance semiconductor material (4) by using a low-temperature photoconductive test system so as to analyze defect performance; performing hall effect testing of electrical and optical inputs using a hall effect testing system;
the sub-forbidden band light auxiliary PICTS test system comprises an optical excitation device, a sub-forbidden band light radiation device (7), a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller (1), a direct current power supply (2), a current amplifier (8), an oscilloscope (9) and a computer (10); the sub-band gap light auxiliary PICTS test system is based on PICTS test of a photo-generated current transient spectrum device, and based on an original light excitation device serving as an excitation light source, a sub-band gap light radiation device (7) is added, and the sub-band gap light radiation device (7) radiates a beam of sub-band gap light to continuously irradiate a high-resistance semiconductor material (4) serving as a test sample so as to obtain influence information of the sub-band gap light on crystal defects; the wavelength of illumination of the sub-forbidden band is changed, so that different defects are controlled to be excited one by one, and influence information and data of single defects on carrier transport performance are obtained;
the low-temperature photoconductive test system comprises a light excitation device, a sample chamber and a signal acquisition and processing system; the signal acquisition and processing system comprises a temperature controller (1), a direct current power supply (2), a current amplifier (8), an oscilloscope (9) and a computer (10); the low-temperature photoconductive test system acquires the change of photocurrent and dark current in the heating process according to the experimental principle of direct current photoconductive by combining a low-temperature control device, fits the acquired photocurrent I-V curve by using a Hecht theory method, and calculates and acquires the mobility life product value of the current carrier;
the Hall effect test system comprises a direct current power supply (2), a magnetic field generating device (3), a current amplifier (8), an oscilloscope (9) and a computer (10), wherein the magnetic field generating device (3) is arranged outside a sample room to apply a magnetic field to a high-resistance semiconductor material (4) arranged in the sample room, the magnetic field generating device (3) provides electric energy through the direct current power supply (2) to generate an adjustable magnetic field, and the temperature-changing Hall effect test is implemented by means of the direct current power supply (2) and a cryostat (5) to obtain the resistivity, the carrier life product and the electrical property of a Hall coefficient of the high-resistance semiconductor material (4); and simultaneously, laser is applied to interfaces of different materials to acquire the electrical property information of the material represented by the optical Hall test of the material.
2. The integrated system for detecting defects and electrical properties of high resistance semiconductor materials of claim 1, wherein: the refrigeration medium of the cryostat (5) adopts liquid nitrogen or liquid helium.
3. The integrated system for detecting defects and electrical properties of high resistance semiconductor materials of claim 1, wherein: the high-resistance semiconductor material (4) is heated by the heat-conducting metal plate, and the computer (10) regulates and controls the heat output of the heat-conducting metal plate by controlling the temperature controller (1).
4. The integrated system for detecting defects and electrical properties of high resistance semiconductor materials of claim 1, wherein: for the low-temperature photoconductive test system, sub-band illumination condition is added in a direct-current photoconductive experiment, and the influence information of each defect on the carrier transport characteristic is identified one by one according to photon energy provided by sub-band light with different wavelengths and energy level positions corresponding to each defect in the high-resistance semiconductor material (4), so as to obtain the influence mechanism information of each defect on the carrier transport characteristic and the mechanism information of sub-band illumination capable of effectively improving the carrier transport characteristic in the semiconductor.
5. The integrated system for detecting defects and electrical properties of high resistance semiconductor materials of claim 1, wherein: the sub-band light radiation device (7) of the sub-band light auxiliary PICTS test system continuously irradiates the high-resistance semiconductor material (4) with sub-band light with the radiation wavelength of 860-1550 nm.
6. The integrated system for detecting defects and electrical properties of high resistance semiconductor materials of claim 1, wherein: for a Hall effect test system, ohmic contact electrodes for Hall effect test are adopted, the electrodes are led out and connected to 4 binding posts of a low-temperature thermostat (5), the output voltage of a direct-current voltage source is applied to 2 electrodes in the ohmic contact electrodes, the other 2 electrodes read out the Hall voltage, and Hall effect test parameters of a Hall coefficient, resistivity and carrier mobility life product are calculated according to a Hall effect test principle formula; based on the Hall effect test, laser is applied to the surface of the high-resistance semiconductor material (4) to replace a direct-current voltage source, and the Hall voltage and corresponding electrical parameters before and after irradiation of the high-resistance semiconductor material (4) are tested, and meanwhile, the optical Hall effect and the electrical parameters of lasers with different wavelengths are detected.
7. A test method for detecting defects and electrical properties of a high-resistance semiconductor material, using the integrated system for detecting defects and electrical properties of a high-resistance semiconductor material according to claim 1, characterized in that:
based on a light-generated current transient spectrum, utilizing multi-band laser and sub-forbidden band light to assist in irradiation to obtain inner deep energy level defect information of the high-resistance semiconductor material, and carrying out characterization experiments on defects of the high-resistance semiconductor material by adopting selection of lasers with different bands and selection and combination of different auxiliary sub-forbidden band light wavelengths;
the integrated system for detecting the defects and the electrical properties of the high-resistance semiconductor material integrates a low-temperature photoconductive system and a Hall effect test system, acquires the electrical properties of the high-resistance semiconductor material, and acquires the electrical property information of the conductivity type, the resistivity, the carrier life product and the Hall coefficient;
the change of the carrier mobility life product under the irradiation of the sub-forbidden band lights with different wavelengths is compared and analyzed to obtain the effect result of single defect on the carrier transport performance;
meanwhile, the voltage polarity at two ends of the illumination surface is changed to control the properties of main unbalanced carriers flowing through the semiconductor, so that the obtained change of illumination current is mainly generated by the influence of defects on electrons or holes, namely, the electron current is mainly or the hole current is mainly, and then the mobility lifetime product is obtained by fitting a Hecht equation, and is used as the mobility lifetime product of a certain carrier.
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