Semiconductor material minority carrier lifetime detection system and method based on quasi-optical cavity

Abstract

This invention discloses a semiconductor material minority carrier lifetime detection system and method based on a quasi-optical cavity, comprising a microwave signal source, a quasi-optical cavity, a detector, a DC signal detection device, and a pulsed laser source; the output end of the microwave signal source is connected to the input end of the quasi-optical cavity, the output end of the quasi-optical cavity is connected to the input end of the detector, the output end of the detector is connected to the input end of the DC signal detection device, the pulsed laser source is positioned directly over the semiconductor material under test, and the semiconductor material under test is located within the quasi-optical cavity. This system and method are characterized by low sample preparation cost and high sensitivity.

Description

Technical Field

[0001] This invention relates to a minority carrier lifetime detection system and method for semiconductor materials, specifically to a minority carrier lifetime detection system and method for semiconductor materials based on a quasi-optical cavity. Background Technology

[0002] Minority carrier lifetime is a critical parameter for semiconductor materials. Since minority carrier lifetime directly affects the performance of semiconductor devices, its detection is indispensable for the research and development and production of related devices. Furthermore, because minority carrier lifetime is closely related to the manufacturing process, its detection can indirectly assess the process quality of semiconductor materials / devices.

[0003] Microwave photoconductivity attenuation is one of the mainstream methods for minority carrier lifetime detection, offering significant advantages such as non-contact operation and high sensitivity. Based on its working principle, microwave photoconductivity attenuation can be divided into transmission / reflection methods and resonant methods. In the transmission / reflection method, photogenerated carriers in the semiconductor material affect the transmission / reflection of the microwave signal; therefore, minority carrier lifetime detection can be achieved by detecting the time-varying process of the transmission / reflection signal. In the resonant method, the test material is located in a resonant electromagnetic environment, and photogenerated carriers significantly affect the response characteristics of the microwave sensor. Therefore, the resonant method has higher sensitivity than the transmission / reflection method and represents the future development direction of microwave photoconductivity attenuation. Existing resonant microwave photoconductivity attenuation methods mainly include planar resonators and non-planar resonant cavities. For the former, the test material needs to be fabricated into a specific shape and size, resulting in high sample preparation difficulty; for the latter, either the test material is fabricated into a specific shape and size and placed in a specific position within the cavity, or the test material outside the cavity is detected through pinhole coupling, thus also facing problems of high sample preparation cost or limited sensitivity. In summary, existing resonant microwave photoconductive attenuation methods face problems such as difficulty in sample preparation or low sensitivity. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a semiconductor material minority carrier lifetime detection system and method based on a quasi-optical cavity, which has the characteristics of low sample preparation cost and high sensitivity.

[0005] To achieve the above objectives, the semiconductor material minority carrier lifetime detection system based on a quasi-optical cavity described in this invention includes a microwave signal source, a quasi-optical cavity, a detector, a DC signal detection device, and a pulsed laser source;

[0006] The output of the microwave signal source is connected to the input of the quasi-optical cavity, the output of the quasi-optical cavity is connected to the input of the detector, the output of the detector is connected to the input of the DC signal detection device, the pulsed laser source is facing the semiconductor material under test, and the semiconductor material under test is located inside the quasi-optical cavity.

[0007] The collimator is either a plano-concave cavity or a biconcave cavity.

[0008] The semiconductor material under test is placed at the location of the strongest electric field within the quasi-optical cavity.

[0009] The quasi-optical cavity uses single-port feeding or dual-port feeding.

[0010] The microwave signal source is connected to the quasi-optical cavity via a coaxial transmission line or a waveguide transmission line.

[0011] The quasi-optical cavity is connected to the detector via a coaxial transmission line or a waveguide transmission line.

[0012] The DC signal detection device is an oscilloscope.

[0013] The method for detecting minority carrier lifetime in semiconductor materials based on a quasi-optical cavity as described in this invention includes the following steps:

[0014] A continuous wave signal output from a microwave signal source is fed into a quasi-optical cavity and interacts with the semiconductor material under test within the cavity. Simultaneously, a pulsed laser emitted from a pulsed laser source irradiates the semiconductor material under test. Under the irradiation of the pulsed laser, the semiconductor material under test undergoes photoconductive effect, and the output signal of the quasi-optical cavity exhibits time-varying characteristics. The output signal of the quasi-optical cavity enters a detector, and the output signal of the detector is displayed on a DC signal detection device. Since the output signal of the quasi-optical cavity exhibits time-varying characteristics, the output voltage of the detector exhibits an exponential decay law after the illumination ends. The minority carrier lifetime of the semiconductor material under test is obtained based on the time-varying characteristics.

[0015] The present invention has the following beneficial effects:

[0016] In practical operation, the quasi-optical cavity-based minority carrier lifetime detection system and method for semiconductor materials described in this invention replaces the traditional detection cavity with a quasi-optical cavity. The semiconductor material to be tested is directly placed inside the quasi-optical cavity, and the semiconductor material to be tested is irradiated by a pulsed laser emitted from a pulsed laser source. It does not require the material to be made into a specific shape, making the manufacturing process easier. At the same time, because the output signal of the quasi-optical cavity exhibits time-varying characteristics, the output voltage of the detector exhibits an exponential decay law after the illumination ends. The minority carrier lifetime of the semiconductor material to be tested is obtained based on the time-varying characteristics, resulting in high sensitivity. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] Among them, 1 is a microwave signal source, 2 is a detector, 3 is a quasi-optical cavity, 4 is a pulsed laser source, and 5 is a DC signal detection device. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0020] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not drawn to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0021] refer to Figure 1 The semiconductor material minority carrier lifetime detection system based on quasi-optical cavity described in this invention includes a microwave signal source 1, a quasi-optical cavity 3, a detector 2, a DC signal detection device 5, and a pulsed laser source 4;

[0022] The output of microwave signal source 1 is connected to the input of quasi-optical cavity 3. The output of quasi-optical cavity 3 is connected to the input of detector 2. The output of detector 2 is connected to the input of DC signal detection device 5. Pulsed laser source 4 is facing the semiconductor material to be tested. The semiconductor material to be tested is located inside quasi-optical cavity 3.

[0023] Based on the size and doping concentration of the semiconductor material under test, a quasi-optical cavity 3 is designed and optimized. The quasi-optical cavity 3 can be a plano-concave cavity or a bi-concave cavity. Design and optimization parameters include the spherical mirror aperture, the radius of curvature of the spherical mirror, the cavity length, the number of modes, and the cavity wall material. During the design of the quasi-optical cavity 3, the resonant frequency, quality factor, and number of modes must consider the mechanism and laws of microwave-semiconductor interaction to improve detection sensitivity. The semiconductor material under test is placed at a specific location inside the quasi-optical cavity 3, such as the point of strongest electric field. Under the excitation of the pulsed laser emitted from the pulsed laser source 4, it undergoes a photoconductive effect, affecting the output signal of the quasi-optical cavity 3.

[0024] The quasi-optical cavity 3 can be fed by a single port or a dual port; depending on the operating frequency band, it can be fed by coaxial feeding (low frequency band of microwave) or waveguide feeding (high frequency band of microwave), or it can be fed through a reflective surface. The microwave signal source 1 emits a continuous wave signal with a set frequency and power, which enters the quasi-optical cavity 3. When the photoconductive effect occurs, the output signal of the quasi-optical cavity 3 changes accordingly and is detected by the detector 2 outside the quasi-optical cavity 3, and then sent to the DC signal detection device 5, which is an oscilloscope, for display.

[0025] The method for detecting minority carrier lifetime in semiconductor materials based on a quasi-optical cavity as described in this invention includes the following steps:

[0026] A microwave signal source 1 outputs a continuous wave signal with a specific frequency and power, which is then fed into a quasi-optical cavity 3 via a coaxial transmission line or a waveguide transmission line. Within the quasi-optical cavity 3, the signal interacts with the semiconductor material under test, affecting the output signal of the quasi-optical cavity 3. This output signal is then output to a detector 2 via the coaxial transmission line or waveguide transmission line, and the output signal of the detector 2 is displayed on an oscilloscope. Under pulsed laser irradiation, the semiconductor material under test undergoes photoconductive effect, and the output signal of the quasi-optical cavity 3 exhibits time-varying characteristics. Typically, the output voltage of the detector 2 decays exponentially after the irradiation ends. The minority carrier lifetime of the semiconductor material under test is obtained based on these time-varying characteristics.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A semiconductor material minority carrier lifetime detection system based on a quasi-optical cavity, characterized in that, It includes a microwave signal source (1), a quasi-optical cavity (3), a detector (2), a DC signal detection device (5), and a pulsed laser source (4); The output of the microwave signal source (1) is connected to the input of the quasi-optical cavity (3), the output of the quasi-optical cavity (3) is connected to the input of the detector (2), the output of the detector (2) is connected to the input of the DC signal detection device (5), the pulsed laser source (4) is facing the semiconductor material to be tested, and the semiconductor material to be tested is located inside the quasi-optical cavity (3); The quasi-optical cavity (3) is a plano-concave cavity or a bi-concave cavity; The semiconductor material to be tested is placed at the position of strongest electric field within the quasi-optical cavity (3); Based on the size and doping concentration of the semiconductor material to be tested, a quasi-optical cavity (3) is designed and optimized. The quasi-optical cavity (3) is a plano-concave cavity or a double-concave cavity. The design and optimization parameters include the spherical mirror aperture, the spherical mirror radius of curvature, the cavity length, the number of modes, and the cavity wall material. In the design process of the quasi-optical cavity (3), the design of the resonant frequency, quality factor, and number of modes needs to consider the mechanism and law of microwave-semiconductor interaction in order to improve the detection sensitivity.

2. The semiconductor material minority carrier lifetime detection system based on a quasi-optical cavity according to claim 1, characterized in that, The quasi-optical cavity (3) is fed by a single-port or dual-port power supply.

3. The semiconductor material minority carrier lifetime detection system based on a quasi-optical cavity according to claim 1, characterized in that, The microwave signal source (1) is connected to the quasi-optical cavity (3) via a coaxial transmission line or a waveguide transmission line.

4. The semiconductor material minority carrier lifetime detection system based on a quasi-optical cavity according to claim 1, characterized in that, The quasi-optical cavity (3) is connected to the detector (2) via a coaxial transmission line or a waveguide transmission line.

5. The semiconductor material minority carrier lifetime detection system based on a quasi-optical cavity according to claim 1, characterized in that, The DC signal detection device (5) is an oscilloscope.

6. A method for detecting minority carrier lifetime in semiconductor materials based on a quasi-optical cavity, characterized in that, Includes the following steps: The continuous wave signal output from the microwave signal source (1) is fed into the quasi-optical cavity (3) and interacts with the semiconductor material under test in the quasi-optical cavity (3). At the same time, the pulsed laser emitted by the pulsed laser source (4) irradiates the semiconductor material under test. Under the irradiation of the pulsed laser, the semiconductor material under test undergoes photoconductive effect, and the output signal of the quasi-optical cavity (3) exhibits time-varying characteristics. The output signal of the quasi-optical cavity (3) enters the detector (2), and the output signal of the detector (2) is displayed on the DC signal detection device (5). Since the output signal of the quasi-optical cavity (3) exhibits time-varying characteristics, the output voltage of the detector (2) exhibits an exponential decay law after the light irradiation ends. The minority carrier lifetime of the semiconductor material under test is obtained based on the time-varying characteristics.

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