Preparation method of I-type quantum well structure based on dipole design

Abstract

The invention relates to the technical field of semiconductor photoelectronics, in particular to a preparation method of an I-type quantum well structure based on dipole design. According to the specific technical scheme, a GaSb substrate is included, a GaSb buffer layer and a quantum well active region Inx1Ga1-x1Asy1Sb1-y1 / Alx2Ga1-x2Asy2Sb1-y2 of three periods are grown on the GaSb substrate layer through the molecular beam epitaxy technology, and x1 is larger than 0 and smaller than 1, x2 is larger than 0 and smaller than 1, y1 is larger than 0 and smaller than 1, y2 is larger than 0 and smaller than 1, y1 is larger than 0 and smaller than 1, and y2 is larger than 0 and smaller than 1. On the basis of a molecular beam epitaxial growth technology, Si donor impurities are doped into the InGaAsSb potential well layer, so that the valence band order is improved, the problems that the valence band order of a well layer material with a high In component in an I-type quantum well is reduced, and carrier leakage is aggravated are solved, the quantum well structure with high radiation recombination efficiency is formed, and the quantum efficiency is improved. And a high-quality active region material is provided for a middle-infrared band laser with the wavelength of 3-5 microns.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronics technology, and more specifically to a method for fabricating a type I quantum well structure based on dipoleization design. Background Technology

[0002] Mid-infrared semiconductor laser sources, due to their unique operating wavelength, possess the potential for wide application in both military and civilian fields, making them a hot topic in semiconductor laser research. Existing 2–5 μm mid-infrared semiconductor lasers mostly employ antimonyide type I quantum wells or cascaded structures as the active material. Among them, antimonyide lasers in the 2–3 μm band (such as GaSb and InGaAsSb-based quantum well structures) have achieved continuous operation at room temperature, with output power reaching hundreds of milliwatts to watts, and electro-optical efficiencies between 10% and 20%, and have been successfully applied in gas sensing, medical applications, and infrared communication. However, extending their application to the 3–5 μm band still faces many technical challenges.

[0003] Antimonide InGaAsSb / AlGaAsSb type I quantum wells have advantages such as simple structure, high quantum efficiency, and easy bandgap cutting. However, as the operating wavelength is extended to the 3-5 μm band, the valence band order of the InGaAsSb well layer material with high In content decreases, which aggravates carrier leakage and affects the output performance of the laser, making it difficult to improve the output power.

[0004] In existing technologies, to extend the operating wavelength of InGaAsSb / AlGaAsSb type I quantum well semiconductor lasers to the 3–5 μm band, an AlGaInAsSb pentagonal alloy barrier structure is fabricated by increasing the In content in the well layer material to compress the band gap. The introduction of the In content shifts the energy band of the barrier region downwards, achieving a larger valence band level at the cost of appropriately reducing the conduction band level, thus improving the hole confinement capability of the valence band and achieving wavelength extension. However, this leads to a downward shift in the overall energy band of the well layer material, weakening the valence band level between the wells and barriers, resulting in a flattening of the valence band of the wells and barriers, a sharp decrease in carrier confinement capability, and limited further wavelength extension. Even with the AlInGaAsSb pentagonal alloy barrier, the valence band shift caused by adjusting the composition is between (50–80) meV, and it is still difficult to effectively solve the problem of insufficient gain capability caused by hole leakage.

[0005] Currently, the realization of the 3–5 μm band typically relies on interband cascade structures and quantum cascade structures; however, this method faces high growth costs and complex technical challenges. In contrast, type I quantum well structures exhibit advantages such as high technological maturity and low production costs, thus possessing greater value in practical applications. Therefore, effectively improving the valence band order of InGaAsSb / AlGaAsSb type I quantum wells to enhance the active region gain capability is a key scientific problem that urgently needs to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for fabricating a type I quantum well structure based on dipoleization design. Using molecular beam epitaxy, Si donor impurities are incorporated into the InGaAsSb potential well layer to increase the valence band order, thus solving the problem of reduced valence band order and increased carrier leakage in type I quantum wells with high In composition. This results in a quantum well structure with high radiative recombination efficiency, providing high-quality active region materials for 3–5 μm mid-infrared lasers.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a method for fabricating a type I quantum well structure based on dipoleization design, comprising a GaSb substrate, on which a GaSb buffer layer and a three-period In quantum well active region are grown by molecular beam epitaxy. x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 , where 0 < x1 < 1, 0 < x2 < 1, 0 < y1 < 1, 0 < y2 < 1.

[0008] Preferably, the thickness of the GaSb buffer layer is 200–300 nm.

[0009] Preferably, the active region In of the quantum well x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 The growth temperature is as follows: start heating at 200℃, deoxygenate after 6 minutes at 500-560℃, and maintain at 450-500℃ for 15 minutes.

[0010] Preferably, the active region In of the quantum well x1 Ga 1-x1 Asy1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 The quantum well layer and the quantum barrier layer are grown alternately for 3 cycles. The thickness of the quantum well layer is 10 nm and the thickness of the quantum barrier layer is 20 nm.

[0011] Preferably, the quantum well layer is In x1 Ga 1-x1 As y1 Sb 1-y1 0 < x1 < 1, 0 < y1 < 1; the quantum barrier layer is Al x2 Ga 1-x2 As y2 Sb 1-y2 , 0 < x2 < 1, 0 < y2 < 1.

[0012] Preferably, the quantum well layer In x1 Ga 1-x1 As y1 Sb 1-y1 Si is doped into the quantum well layer, replacing the group III elements, with a doping amount of 1-5%.

[0013] Preferably, the prepared quantum well is subjected to rapid thermal annealing at a temperature of 400°C for 1 minute.

[0014] The present invention has the following beneficial effects: 1. The dipoleized antimonide type I quantum well structure proposed in this invention introduces an interface dipole into the quantum well, utilizes the band bending generated by the dipole to increase the hole barrier height, enhances its confinement effect on holes, and thus realizes high power output of a high In composition long wavelength antimonide type I quantum well laser.

[0015] 2. The dipole-based quantum well structure proposed in this invention brings the following advantages and effects: (1) Expanding the operating wavelength of quantum well lasers: By improving the InGaAsSb / AlGaAsSb I type quantum well structure through dipoleization, the emission band can be precisely controlled, enabling it to operate in the wavelength range of 2 to 5 μm.

[0016] (2) Enhance the confinement effect of the well barrier on the charge carriers: By using a dipoleized quantum well structure, the band structure is optimized. While the working wavelength is extended, the charge carriers can still be effectively confined in the quantum well, thereby reducing the phenomenon of charge carrier leakage. Attached Figure Description

[0017] Figure 1(a) is a schematic diagram of the "dipolarization" of a type I quantum well containing antimony, and (b) is a schematic diagram of the dipolarization control process. Figure 2 Photoluminescence properties of the quantum well prepared in Example 1 at low temperature (75K) and room temperature, X-ray diffraction curves and atomic force microscopy images; Figure 3 Photoluminescence properties of the quantum well prepared in Example 2 at low temperature (75K) and room temperature, X-ray diffraction curves and atomic force microscopy images; Figure 4 The photoluminescence properties of the quantum well prepared in Example 3 at low temperature (75K) and room temperature, X-ray diffraction curves, and atomic force microscopy images. Detailed Implementation

[0018] 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0020] This invention provides a type I quantum well structure based on dipoleization design, in which Si donor impurities are doped at the quantum well interface during epitaxial growth to replace group III elements in the InGaAsSb well layer. Figure 1 In (a), the left side is a schematic diagram of the quantum well energy band structure, and the atomic distribution at the well-barrier interface is as follows. Figure 1 (a) As shown on the right, at the well-barrier interface, electrons flow from the area with a lower work function to the area with a higher work function, forming an interface dipole layer. The dipoles create a positive charge density in the potential well region, and the direction of the dipoles points from the inside of the semiconductor to the interface. Figure 1 As shown in (a), a dipole layer is formed at the boundary between group III and group V elements. At this time, the polarization effect generated by the dipole layer can shift the energy band of the AlGaAsSb barrier layer downward, increase the valence band order of the barrier well, improve the carrier confinement capability under the premise of wavelength extension, and thereby improve the valence band order of the type I quantum well.

[0021] To achieve the required dipole control in InGaAsSb / AlGaAsSb type I quantum wells, strict control of the atomic arrangement at the quantum well interface is necessary. Specifically, the InGaAsSb layer must have a group III element as the cutoff surface, and the AlGaAsSb barrier layer must have a group V element as the cutoff surface. Furthermore, donor-doped Si atoms must strictly replace the group III elements in the InGaAsSb layer. By ultrafast extraction and switching of the group V beam, control over the nucleus type and migration distance can be achieved. Therefore, directional migration and fusion of multiple lattice types can be realized within a single molecular layer, such as... Figure 1 As shown in (b).

[0022] This invention provides a design method for a dipole-based InGaAsSb / AlGaAsSb type I quantum well structure. Si donor impurities are doped at the quantum well interface to replace group III elements in the InGaAsSb well layer. By increasing the positive charge density at the interface, the interface dipole strength is enhanced, causing a downward shift in the AlGaAsSb barrier layer's energy band, thereby improving the band order of the type I quantum well. By employing interface-induced dipoleization during epitaxial growth, the valence band shift can reach 100–250 meV. Ultimately, this extends the laser wavelength to the 3–5 μm range while simultaneously improving the carrier confinement capability of the active region, thus increasing the laser output power.

[0023] Finally, the optical properties of the material were evaluated by photoluminescence (PL) to verify the effect of Si element introduction into the well layer to induce "dipoleization" on the performance of type I quantum well.

[0024] The present invention provides a fabrication process for a type I quantum well structure based on dipole design, namely the design and fabrication of an InAsGaSb(Si) / AlGaAsSb "dipole-based" quantum well, the specific steps of which are as follows: 1. Band Design In the development of quantum well materials, the first step is band structure design, which involves theoretical calculations to determine the band structure, strain distribution, and composition parameters of the material. The design goal is to optimize the band structure of the InAsGaSb(Si) / AlGaAsSb quantum well by introducing Si, forming a dipole-based quantum well structure, reducing the barrier valence band gap, improving the ability to confine holes, and effectively extending the wavelength.

[0025] 2. Composition and Thickness Design Determine the composition of the InAsGaSb(Si) layer and the AlGaAsSb layer, such as the Si content in InAsGaSb(Si) (1% to 5%), the thickness of the InAsGaSb(Si) layer is 10 nm, and the thickness of the AlGaAsSb layer is 20 nm.

[0026] The number of quantum well cycles (designed to be 3 cycles) is used to achieve target band coverage.

[0027] 3. MBE epitaxial growth After completing the band structure design, the quantum well material was epitaxially grown using molecular beam epitaxy (MBE). The detailed growth steps are as follows: (1) Substrate selection Substrate selection: GaSb substrate; The GaSb substrate was placed in a beaker and ultrasonically cleaned for 20 minutes at 70 Hz with ethanol and deionized water respectively to remove surface dust and oil. Then, it was placed in a drying oven to dry the residual moisture. The cleaned GaSb substrate was placed in a pre-vacuum chamber and degassed at 200°C to remove the gas adsorbed on the substrate surface. The pre-treated GaSb substrate was transferred to a buffer chamber and heated at 400°C to further remove impurities adsorbed on the substrate surface. The beam current monitor was turned on and the sample was blocked with a baffle. The source furnace for the epitaxial material was heated, and the beam current intensity of each source at different temperatures was measured.

[0028] (2) Buffer layer: GaSb Thickness control: 300 nm (molecular beam epitaxy (MBE) growth); The GaSb substrate was transferred to the growth chamber and placed on the sample holder. Under the protection of an antimony molecular beam, the temperature was raised to 600℃ to remove the surface oxide layer. Real-time monitoring was performed using RHEED, and the material was grown layer by layer according to the designed structure. The baffles of the Ga and Sb sources were then opened to grow a GaSb buffer layer with a thickness of 300 nm at a growth temperature of 550℃. The flux of the Group III Ga source was 0.4 ML / s, and the Group V Sb beam current was 6.8 × 10⁻⁶. -6 Torr; Sb / Ga beam ratio of 1.05, reducing interface dislocation density.

[0029] (3) Quantum well active region (MQW): InGaAsSb(Si) / AlGaAsSb (10nm well / 20nm barrier)×3 With the baffles of the Al, In, Si, and As sources removed, three cycles of InGaAsSb(Si) / AlGaAsSb quantum well layers were grown. The AlGaAsSb barrier layer thickness was 20 nm, with Al composition ranging from 0 to 1 and Sb composition ranging from 0 to 1. The InGaAsSb(Si) well layer thickness was 10 nm, with In composition ranging from 0 to 1, Sb composition ranging from 0 to 1, and Si content ranging from 1% to 5%. Turn off the As, Si, In, and Al sources, turn off the Ga source, and under the protection of the Sb source beam, lower the growth temperature to 100°C. Turn off the Sb source, lower the growth temperature to room temperature, and then remove the sample.

[0030] (4) Post-treatment: rapid thermal annealing Temperature: 400°C; Time: 1 minute; Objective: To improve crystal quality and reduce defects.

[0031] (5) Characterization The photoluminescence properties of the quantum well were characterized using Fourier transform infrared spectroscopy. Simultaneously, X-ray diffraction and atomic force microscopy were used to evaluate the crystal growth quality.

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] Example 1 The InAsGaSb(Si) / AlGaAsSb “dipoleized” quantum wells were prepared according to the above preparation process, with the difference that: step (3) In the active region of the quantum well 0.20 Ga 0.80 As 0.10 Sb 0.89 (Si 0.01 ) / Al 0.35 Ga 0.65 As 0.02 Sb 0.98 In a (10nm well / 20nm barrier)×3 matrix, Si is doped at 1%. The specific process is as follows: Growth temperature: Start heating at 200℃, then deoxygenate after 7 minutes at 490℃, and maintain at 470℃ for 15 minutes. Quantum well layer: 10 nm thick; Dynamic parameters: Group III source: In: 0.058 ML / s; Ga: 0.232 ML / s; V-group source: As: 6.5 × 10 -6 Torr; Sb: 3.0×10 -5 Torr; Si beam: 2.5 × 10 -8 Torr; V / III ratio 0.95, As / Sb ratio 0.22; Quantum barrier layer: 20nm thick; Dynamic parameters: Group III source: Al: 0.135 ML / s; Ga: 0.201 ML / s V-group source: As: 1.8 × 10 -6 Torr; Sb: 9.0 × 10 -5 Torr; V / III ratio 1.15, As / Sb ratio 0.02.

[0034] The photoluminescence properties of quantum traps at low temperature (75 K) and room temperature were characterized using a Fourier transform infrared spectrometer at 100 mW and 100 mV. Figure 2 As shown, the central peak of low-temperature luminescence is at 3.88 μm, and the central peak of room-temperature luminescence is at 4.5 μm. Photoluminescence (PL) analysis shows a high signal-to-noise ratio and good luminescence performance. X-ray diffraction (XRD) tests indicate good crystal growth quality. In atomic force microscopy (AFM), the measured surface roughness Rq is 0.238 nm, indicating that the sample has high smoothness and good surface quality.

[0035] Example 2 Same as Example 1, except that: step (3) the active region In of the quantum well 0.35 Ga 0.65 As 0.12 Sb 0.86 (Si 0.02 ) / Al 0.35 Ga 0.65 As 0.02 Sb 0.98 In a (10nm well / 20nm barrier)×3 matrix, 2% Si is doped. The specific process is as follows: Growth temperature: Start heating at 200℃, then deoxygenate after 7 minutes at 520℃, and maintain at 470℃ for 15 minutes. Quantum well layer: 10 nm thick; Dynamic parameters: Group III source: In: 0.126 ML / s; Ga: 0.234 ML / s; V-group source: As: 5.0 × 10 -6 Torr; Sb: 3.6×10 -5 Torr; Si beam: 3.2 × 10 -8 Torr; V / III ratio 1.10, As / Sb ratio 0.14; Quantum barrier layer: 20nm thick; Dynamic parameters: Group III source: Al: 0.110 ML / s; Ga: 0.204 ML / s V-group source: As: 1.1 × 10 -6 Torr; Sb: 5.4 × 10 -5 Torr; V / III ratio 1.20, As / Sb ratio 0.02.

[0036] The photoluminescence properties of quantum traps at low temperature (75 K) and room temperature were characterized using a Fourier transform infrared spectrometer at 100 mW and 100 mV. Figure 3 As shown, the central peak of low-temperature luminescence is 4.32 μm, and the central peak of room-temperature luminescence is 4.78 μm. Pulse analysis shows a high signal-to-noise ratio and good luminescence performance. X-ray diffraction tests indicate good crystal growth quality. In atomic force microscopy characterization, the measured surface roughness Rq is 0.245 nm, indicating that the sample has good smoothness and good surface quality.

[0037] Example 3 Same as Example 1, except that: step (3) the active region In of the quantum well 0.35 Ga 0.65 As 0.21 Sb 0.76 (Si 0.03 ) / Al 0.35 Ga 0.65 As 0.02 Sb 0.98 In a (10nm well / 20nm barrier)×3 matrix, Si is doped at 3%. The specific process is as follows: Growth temperature: Start heating at 200℃, deoxygenate after 7.5 minutes at 505℃, maintain at 485℃ for 15 minutes. Quantum well layer: 10 nm thick; Dynamic parameters: Group III source: In: 0.135 ML / s; Ga: 0.251 ML / s; V-group source: As: 8.0 × 10 -6 Torr; Sb: 2.9×10 -5 Torr; Si beam: 9.6 × 10 -8 Torr; V / III ratio 1.25, As / Sb ratio 0.28; Quantum barrier layer: 20nm thick; Dynamic parameters: Group III source: Al: 0.115 ML / s; Ga: 0.214 ML / s V-group source: As: 1.1 × 10 -6 Torr; Sb: 5.4 × 10 -5 Torr; V / III ratio 1.20, As / Sb ratio 0.02.

[0038] The photoluminescence properties of quantum traps at low temperature (75 K) and room temperature were characterized using a Fourier transform infrared spectrometer at 100 mW and 100 mV. Figure 4 As shown, the central peak of low-temperature luminescence is at 4.73 μm, and the central peak of room-temperature luminescence is at 5.02 μm. Pulse analysis shows a high signal-to-noise ratio and good luminescence performance. X-ray diffraction tests indicate good crystal growth quality. In atomic force microscopy characterization, the measured surface roughness Rq is 0.269 nm, indicating that the sample has good smoothness and good surface quality.

[0039] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for fabricating a type I quantum well structure based on dipoleization design, characterized in that: Includes a GaSb substrate, on which a GaSb buffer layer and a three-period quantum well active region In are grown using molecular beam epitaxy. x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 , where 0 < x1 < 1, 0 < x2 < 1, 0 < y1 < 1, 0 < y2 < 1.

2. The method for fabricating a type I quantum well structure based on dipoleization design according to claim 1, characterized in that: The thickness of the GaSb buffer layer is 200–300 nm.

3. The method for fabricating a type I quantum well structure based on dipoleization design according to claim 1, characterized in that: The active region In of the quantum well x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 The growth temperature is as follows: start heating at 200℃, deoxygenate after 6 minutes at 500-560℃, and maintain at 450-500℃ for 15 minutes.

4. The method for fabricating a type I quantum well structure based on dipoleization design according to claim 3, characterized in that: The active region In of the quantum well x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 The quantum well layer and the quantum barrier layer are grown alternately for 3 cycles. The thickness of the quantum well layer is 10 nm and the thickness of the quantum barrier layer is 20 nm.

5. The method for fabricating a type I quantum well structure based on dipoleization design according to claim 4, characterized in that: The quantum well layer is In x1 Ga 1-x1 As y1 Sb 1-y1 0 < x1 < 1, 0 < y1 < 1; the quantum barrier layer is Al x2 Ga 1- x2 As y2 Sb 1-y2 , 0 < x2 < 1, 0 < y2 < 1.

6. The method for fabricating a type I quantum well structure based on dipoleization design according to claim 5, characterized in that: The quantum well layer In x1 Ga 1-x1 As y1 Sb 1-y1 Si is doped into the quantum well layer, replacing the group III elements, with a doping amount of 1-5%.

7. The method for fabricating a type I quantum well structure based on dipoleization design according to any one of claims 1 to 6, characterized in that: The prepared quantum well was subjected to rapid thermal annealing at a temperature of 400℃ for 1 min.

Images