Method for measuring dislocation density and spatial distribution characteristic of tellurium-cadmium-mercury p-on-n material interface

Abstract

The invention discloses a method for measuring interface dislocation density and spatial distribution characteristics of a mercury cadmium telluride p-on-n material, and belongs to the field of photoelectric material preparation. The method comprises the following steps: (1) testing the total thickness of a p-on-n material; (2) carrying out dislocation corrosion; (3) measuring the density of the dislocation corrosion pit; (4) testing the residual thickness of the material; (5) repeating the steps (2)-(4) until the residual thickness is less than or equal to 0.1 micron; (6) drawing a changing curve of the thickness and the dislocation density; (7) determining interface dislocation density and dislocation space distribution characteristics, namely, a first peak value on the curve is the interface dislocation density between the p-type layer and the n-type layer, and a second peak value is the interface dislocation density between the n-type layer and the substrate; and the dislocation space distribution characteristic of the p-on-n material is reflected through the relationship between the curve dislocation density and thickness. The method solves the problems of difficulty in interface dislocation density testing and dislocation space distribution characteristics caused by difficulty in appearance of corrosion pits in section corrosion measurement, and is simple to operate and high in accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric material preparation, and specifically relates to a method for measuring the dislocation density and spatial distribution characteristics of the interface of mercury cadmium telluride (HgCdTe) p-on-n material, which is used to reveal the dislocation density and spatial distribution characteristics of the interface of HgCdTe p-on-n material. Background Art

[0002] The bandgap of mercury cadmium telluride (Hg1-xCdxTe) can be continuously tuned within the 0 to 1.6 eV range depending on the component x, enabling detection across the entire infrared band. Hg1-xCdxTe infrared focal plane detectors are the most urgently needed and widely used key components in optoelectronic systems for weaponry, with applications in precision guidance, missile defense warning, Earth observation, deep space exploration, and other fields. The development of infrared focal plane detectors toward higher resolution, higher sensitivity, and higher operating temperatures has placed higher demands on device performance, particularly dark current control.

[0003] HgCdTe focal plane devices primarily have two structures: n-on-p and p-on-n. From a device structural design perspective, there's no clear distinction between n-on-p and p-on-n device structures. N-on-p devices use p-type materials as their absorption layer, which have a low minority carrier lifetime, making it difficult to control dark current at a low level. P-on-n devices, on the other hand, use n-type HgCdTe as their absorption layer, which has a relatively low carrier concentration. Because the minority carrier lifetime of n-type HgCdTe is superior to that of p-type materials, p-on-n devices exhibit even lower dark current. Theoretically, the dark current of p-on-n devices can be two orders of magnitude lower than that of n-on-p devices.

[0004] P-on-n devices can be fabricated through As ion implantation and in-situ growth. However, As ion implantation introduces lattice damage to the material and requires high-temperature activation, which is detrimental to the fabrication of high-performance infrared detectors. In-situ growth of p-on-n double-layer heterojunction materials allows for in-situ doping and activation during the growth process, avoiding ion implantation damage and high-temperature activation. This is a promising technology for developing high-performance p-on-n long-wave / very long-wave, and high-temperature HgCdTe devices with high sensitivity and resolution.

[0005] However, as a p-on-n double-layer heterojunction material, the interface is a key factor affecting the performance of infrared detectors. Excessively high interface dislocation density will lead to an increase in defect-assisted tunneling current in the junction region, increasing dark current and directly affecting the infrared detector's infrared performance. Characterizing the interface dislocation density and dislocation spatial distribution characteristics is key to achieving the preparation and optimization of high-quality p-on-n double-layer heterojunction materials, and it restricts the development of high-performance p-on-n long-wave / very long-wave and high-temperature HgCdTe devices. Traditional cross-sectional cleavage etching has difficulty exposing the dislocation density at the interface and can only obtain local dislocation density, making it difficult to reveal the lateral dislocation density and spatial distribution characteristics of the entire interface. Summary of the Invention

[0006] The present invention aims to solve the difficulties in testing the dislocation density at the p-on-n heterojunction interface and revealing the spatial distribution characteristics of dislocations. It aims to overcome the difficulty of visualizing corrosion pits in traditional cross-sectional corrosion measurements, and provide a basis for optimizing the interface quality and overall performance of p-on-n materials.

[0007] The technical solution of the present invention is: A method for measuring the dislocation density and spatial distribution characteristics of the interface of mercury cadmium telluride p-on-n material, comprising: (1) Total thickness test of p-on-n materials; (2) Using an etchant to perform dislocation etching through an etching process; (3) Dislocation corrosion pit density measurement; (4) Material remaining thickness test; (5) Repeat steps (2) to (4) until the remaining thickness is ≤ 0.1 μm; (6) Draw the thickness and dislocation density curve; (7) Determine the interface dislocation density and dislocation spatial distribution characteristics, that is, the first peak on the curve is the interface dislocation density between the p-type layer and the n-type layer, and the second peak is the interface dislocation density between the n-type layer and the substrate; the relationship between the dislocation density and thickness of the curve reflects the dislocation spatial distribution characteristics of the p-on-n material.

[0008] Furthermore, the mercury cadmium telluride p-on-n double-layer heterojunction material can be prepared by methods such as vapor phase epitaxy, liquid phase epitaxy, or ion diffusion to control element distribution.

[0009] Furthermore, the dislocation etching agent adopts an aqueous solution prepared with solutes such as potassium dichromate and nitric acid, and the corrosion rate is adjusted by controlling the concentration. The corrosion rate is v, and the v value can be designed after comprehensive consideration of the accuracy requirements and the removal thickness h to achieve precise control of the removal thickness, thereby achieving accurate measurement of the dislocation density.

[0010] Advantages of the present application The present application realizes the accurate measurement of the dislocation density of the TeCdHg p-on-n double heterojunction material interface by the curve of the dislocation density changing with the thickness obtained by the continuous corrosion under the thickness monitoring and the dislocation density testing, solves the problems of the interface dislocation density testing difficulty and the dislocation spatial distribution characteristics caused by the difficulty in the appearance of the corrosion pits existing in the cross-section corrosion measurement, realizes the accurate measurement of the dislocation density of the TeCdHg p-on-n material interface and the revelation of the dislocation spatial distribution characteristics, provides the basis for the interface quality and the overall performance optimization of the p-on-n material, and supports the development of the high-performance p-on-n structure infrared detector. The method is simple in operation and high in accuracy, provides the basis for the interface quality optimization of the material quality, and supports the development and batch production of the high-performance p-on-n structure infrared detector. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The flowchart of the method of the present application.

[0012] Figure 2 The schematic diagram of the TeCdHg p-on-n material structure.

[0013] Figure 3 The measurement results of the dislocation density and the dislocation spatial distribution of the TeCdHg p-on-n material interface. DETAILED DESCRIPTION

[0014] A measurement method of the dislocation density and the spatial distribution characteristics of a TeCdHg p-on-n material interface, comprising: (1) Total thickness testing of the material: using an infrared spectrometer to measure the total thickness of the TeCdHg p-on-n material after growth, denoted as h0=12.4 μm; (2) Dislocation corrosion: preparing a corrosion agent, the corrosion agent is an aqueous solution containing potassium dichromate, nitric acid and other solutes, the corrosion rate is controlled by the concentration and the ratio of the solutes, and the corrosion time is determined by the required removal thickness, and the removal thickness is controlled between 0.2 microns and 0.3 microns; (3) Dislocation etch pit density measurement: using an optical microscope to test and count the number of dislocation etch pits under each field of view after each etching process under the conditions of fixed magnification and fixed field size, the measurement field area is 14045.24 μm 2 , and the dislocation etch pit density N1 is obtained; (4) Residual thickness testing: using an infrared spectrometer to measure the total thickness of the TeCdHg p-on-n double heterojunction material after etching, denoted as h1; (5) Repeat steps (2) to (4) until the remaining thickness is ≤ 0.1 μm, and obtain multiple remaining thicknesses h2, h3, ..., hi of the p-on-n double-layer heterojunction material, and multiple dislocation etching pit densities N2, N3, ..., Ni, where i ≥ 2 represents the number of etching times; (6) Plotting the thickness and dislocation density curve: plotting the dislocation corrosion pit density versus thickness curve; (7) Determine the interface dislocation density and dislocation spatial distribution characteristics. The interface dislocation density between the p-type layer and the n-type layer is determined based on the first peak on the curve drawn in step (6). The interface dislocation density between the n-type layer and the substrate is determined based on the second peak on the curve. The dislocation spatial distribution characteristics of the p-on-n material are reflected by the relationship between the dislocation density and the thickness of the curve.

[0015] Example 1 A method for measuring the dislocation density and spatial distribution characteristics of the interface of mercury cadmium telluride p-on-n material, the specific embodiment of which is as follows: (1) Total thickness test: The total thickness of the grown HgCdTe p-on-n material was measured using an infrared spectrometer, which was recorded as h0 = 12.6 μm. (2) Dislocation etching: Prepare a dislocation etching agent, which is an aqueous solution containing potassium dichromate, nitric acid and other solutes. The etching rate is regulated by the concentration and ratio of the solutes, and the etching time is determined by the removal thickness requirement. The removal thickness is controlled between 0.2 μm and 0.3 μm. In the embodiment, the first etching time is 20 s. (3) Dislocation corrosion pit density measurement: Use an optical microscope to test and count the number of dislocation corrosion pits in each field of view after each etching process under fixed magnification and fixed field of view size, measure the field of view area, and obtain the dislocation corrosion pit density N1; in the embodiment, the dislocation corrosion pit density N1 after the first etching is 2.85×10 4 pieces / cm 2 ; (4) Remaining thickness test: The total thickness of the HgCdTe p-on-n double-layer heterojunction material after corrosion was measured using an infrared spectrometer, which was recorded as h1 = 12.2 μm; (5) Repeat steps (2) to (4) until the remaining thickness is ≤ 0.1 μm, and obtain multiple remaining thicknesses h2, h3, ..., hi of the p-on-n double-layer heterojunction material, and multiple dislocation etching pit densities N2, N3, ..., Ni, where i ≥ 2 represents the number of etching times; (6) Draw the thickness and dislocation density curve: Draw the dislocation corrosion pit density versus thickness curve; the results are as follows Figure 3 As shown; (7) Determine the interface dislocation density and dislocation spatial distribution characteristics. According to the first peak on the curve drawn in step (6), the interface dislocation density between the p-type layer and the n-type layer is determined to be 2.28×10 5 pieces / cm 2 According to the second peak on the curve, the interface dislocation density between the n-type layer and the substrate is determined to be 3.30×10 5 pieces / cm 2 The relationship between dislocation density and thickness is used to reflect the spatial distribution characteristics of dislocations in p-on-n materials: the dislocation density of p-type materials is 1.42×10 4 pieces / cm 2 to 4.98×10 4 pieces / cm 2 At the interface between the p-type layer and the n-type layer, dislocation density multiplication occurs, and the peak dislocation density at the first interface reaches 2.28×10 5 pieces / cm 2 As the etching depth increases, it gradually enters the n-type layer, and the dislocation density decreases and stabilizes at 2.20×10 4 pieces / cm 2 to 8.80×10 4 pieces / cm 2 level, which is comparable to that of a single-layer n-type HgCdTe material. As the etching time increases, the material thickness decreases, and the dislocation density gradually increases near the interface between the n-type layer and the substrate. The peak dislocation density at the second interface reaches 3.30×10 5 pieces / cm 2 With further etching, the number of dislocation etch pits decreases, the dislocation density decreases, and the dislocation density returns to the level of the CdZnTe substrate. According to the above embodiment, the interface dislocation density and dislocation spatial distribution characteristics of the HgCdTe p-on-n material are obtained.

Claims

1. A method for measuring the dislocation density at the interface of HgCdTe p-on-n material, characterized in that: The following steps are involved: (1) Total thickness test of p-on-n materials; (2) Using an etchant to perform dislocation etching through an etching process; (3) Dislocation corrosion pit density measurement; (4) Material remaining thickness test; (5) Repeat steps (2) to (4) until the remaining thickness is ≤ 0.1 μm; (6) Draw the thickness and dislocation density curve; (7) Determine the interface dislocation density and dislocation spatial distribution characteristics, that is, the first peak on the curve is the interface dislocation density between the p-type layer and the n-type layer, and the second peak is the interface dislocation density between the n-type layer and the substrate; the relationship between the dislocation density and thickness of the curve reflects the dislocation spatial distribution characteristics of the p-on-n material.

2. The method for measuring the interface dislocation density of HgCdTe p-on-n materials according to claim 1, characterized in that: In step (1), the total thickness test uses an infrared spectrometer to measure the total thickness of the grown HgCdTe p-on-n material.

3. The method for measuring the interface dislocation density of HgCdTe p-on-n materials according to claim 2, characterized in that: In step (3), the dislocation corrosion pit density is measured by using an optical microscope to test and count the number of dislocation corrosion pits in each field of view after each etching process under fixed magnification and fixed field of view size conditions, measure the field of view area, and obtain the dislocation corrosion pit density.

4. The method for measuring the interface dislocation density of HgCdTe p-on-n materials according to claim 3, characterized in that: In step (4), the remaining thickness test uses an infrared spectrometer to measure the thickness of the mercury cadmium telluride p-on-n double-layer heterojunction material after corrosion.

5. The method for measuring the interface dislocation density of HgCdTe p-on-n materials according to claim 1, characterized in that: The mercury cadmium telluride p-on-n double-layer heterojunction material is prepared by methods such as vapor phase epitaxy, liquid phase epitaxy or ion diffusion to control element distribution.

6. The method for measuring the interface dislocation density of HgCdTe p-on-n materials according to claim 1, characterized in that: The dislocation etching agent is an aqueous solution prepared with potassium dichromate or nitric acid solute.

7. The method for measuring the interface dislocation density of HgCdTe p-on-n materials according to claim 1, characterized in that: The corrosion rate v is adjusted by controlling the concentration of the dislocation etchant. The v value is designed based on the accuracy requirement and the removal thickness h. The corrosion time is determined by the removal thickness requirement to achieve precise control of the removal thickness, thereby achieving accurate measurement of the dislocation density.

8. The method for measuring the interface dislocation density of HgCdTe p-on-n materials according to claim 7, characterized in that: The removal thickness of dislocation corrosion is controlled between 0.2 microns and 0.3 microns.

9. A method for measuring the spatial distribution characteristics of interface dislocations in mercury cadmium telluride p-on-n materials, characterized in that: The curve drawn in step (6) of the method for measuring the interface dislocation density of a mercury cadmium telluride p-on-n material according to any one of claims 1 to 8 reflects the dislocation spatial distribution characteristics of the p-on-n material through the relationship between the dislocation density and the thickness of the curve.

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