A preparation method of a type-I quantum well structure based on dipole design

Abstract

The application relates to the field of semiconductor optoelectronic technology, and particularly relates to a preparation method of a type-I quantum well structure based on a dipole design. The specific technical scheme is as follows: a GaSb substrate, a GaSb buffer layer and three periods of quantum well active region In x1 Ga 1‑ x1 As y1 Sb 1‑y1 / Al x2 Ga 1‑x2 As y2 Sb 1‑y2 , wherein 0 The application is based on a molecular beam epitaxy growth technology, Si donor impurities are doped in an InGaAsSb potential well layer, a valence band step is improved, the problem that the valence band step of a high-In-component well layer material in a type-I quantum well is reduced and the problem that carrier leakage is aggravated are solved, a quantum well structure with high radiation recombination efficiency is formed, and high-quality active region materials are provided for 3-5 mu m mid-infrared waveband lasers.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor optoelectronics, and particularly relates to a preparation method of a type-I quantum well structure based on a dipole design. BACKGROUND

[0002] A mid-infrared waveband semiconductor laser light source has the potential to be widely applied in military and civilian fields due to its unique working waveband, and has become a hotspot in the research of semiconductor lasers. Existing 2-5 mu m mid-infrared waveband semiconductor lasers mostly use antimony compound type-I quantum wells or cascade structures as active region materials. Among them, 2-3 mu m waveband antimony compound lasers (such as GaSb, InGaAsSb-based quantum well structures) have realized continuous operation at room temperature, the output power can reach hundreds of milliwatts to watts, the electro-optical efficiency is between 10% and 20%, and the antimony compound lasers have been successfully applied in the fields of gas sensing, medical treatment and infrared communication. However, there are still many technical challenges in extending them to the 3-5 mu m waveband.

[0003] The antimony compound InGaAsSb / AlGaAsSb type-I quantum well has the advantages of simple structure, high quantum efficiency and easy realization of energy band clipping. When the working wavelength is extended to the 3-5 mu m waveband, the valence band step of the high-In-content InGaAsSb well layer material is reduced, which exacerbates the carrier leakage and affects the output performance of the laser, and the output power of the laser is difficult to improve.

[0004] In the prior art, in order to extend the working wavelength of the InGaAsSb / AlGaAsSb type-I quantum well semiconductor laser to the 3-5 mu m waveband, the In component in the well layer material is increased to compress the band gap, an AlGaInAsSb five-element alloy barrier structure is prepared, the introduction of the In component moves the energy band of the barrier region downward as a whole, and a larger valence band step is obtained at the cost of appropriately reducing the conduction band step, the hole confinement ability of the valence band is improved, and the wavelength is extended. However, this will cause the overall energy band of the well layer material to move downward, weaken the valence band step between the well and the barrier, cause the valence band of the well and the barrier to be flattened, and the carrier confinement ability to sharply decrease, and the wavelength further expands. Even if the AlInGaAsSb five-element alloy barrier changes the valence band offset caused by the adjustment of the components to be between (50-80) meV, the problem of insufficient gain caused by the hole leakage is still difficult to effectively solve.

[0005] At present, the 3-5 mu m band is usually realized by means of band gap cascade structure and quantum cascade structure, however, the method faces high growth cost and complex technical challenges. In comparison, the type I quantum well structure exhibits the advantages of high technical maturity and low production cost, and therefore has more significant value in practical application. Therefore, effectively improving the valence band gap of the InGaAsSb / AlGaAsSb type I quantum well to enhance the gain capability of the active region is a key scientific problem to be solved. SUMMARY

[0006] In view of the deficiencies in the prior art, the application provides a preparation method of a type I quantum well structure based on dipole design, which is based on molecular beam epitaxy growth technology, and the valence band gap is improved by doping Si donor impurities in the InGaAsSb potential well layer, so as to solve the problem that the reduction of the valence band gap of the high-In-content well layer material in the type I quantum well aggravates the carrier leakage, and form a quantum well structure with high radiation recombination efficiency, thereby providing high-quality active region material for 3-5 mu m mid-infrared band lasers.

[0007] To achieve the above object, the application is implemented by the following technical scheme:

[0008] The application discloses a preparation method of a type I quantum well structure based on dipole design, which comprises a GaSb substrate, a GaSb buffer layer and three periods of quantum well active region In x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 , wherein 0 < x1 < 1, 0 < x2 < 1, 0 < y1 < 1 and 0 < y2 < 1.

[0009] Preferably, the thickness of the GaSb buffer layer is 200-300 nm.

[0010] Preferably, the growth temperature of the quantum well active region In x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 is as follows: the temperature is increased to 200 DEG C, the temperature is deoxidized after 6 min at 500-560 DEG C, and the temperature is maintained at 450-500 DEG C for 15 min.

[0011] Preferably, the growth temperature of the quantum well active region In x1 Ga1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 First quantum well layer and quantum barrier layer are alternately grown for 3 periods, the thickness of the quantum well layer is 10nm, and the thickness of the quantum barrier layer is 20nm.

[0012] 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.

[0013] Preferably, the quantum well layer In x1 Ga 1-x1 As y1 Sb 1-y1 is doped with Si, the III group element in the quantum well layer is replaced, and the doping amount is 1-5%.

[0014] Preferably, the prepared quantum well is subjected to rapid thermal annealing treatment, the annealing temperature is 400℃, and the time is 1min.

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

[0016] 1. The dipole Sb chalcogenide type I quantum well structure provided by the present application introduces interface dipoles in the quantum well, uses the energy band bending generated by the dipoles to improve the hole barrier height, improves the restriction on holes, and thus realizes high-power output of the Sb chalcogenide type I quantum well laser with high In component and long wavelength.

[0017] 2. The dipole quantum well structure provided by the present application has the following advantages and effects:

[0018] (1) Expanding the working wavelength of the quantum well laser: through the improvement of the InGaAsSb / AlGaAsSb type I quantum well structure by dipole, the light emitting wavelength is accurately controlled, and the quantum well laser can work in the wavelength range of 2-5um.

[0019] (2) Enhancing the restriction on carriers by the well and barrier: through the dipole quantum well structure, the energy band structure is optimized, the carriers can still be effectively restricted in the quantum well while the working wavelength is expanded, and thus the carrier leakage phenomenon is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Fig. 1 is a schematic diagram of "dipole" of antimonide type I quantum well, and Fig. 2 is a schematic diagram of dipole regulation process;

[0021] Figure 2 Fig. 3 is photoluminescence performance of quantum well prepared in Example 1 at low temperature 75K and room temperature, X-ray diffraction curve and atomic force microscope image;

[0022] Figure 3 Fig. 4 is photoluminescence performance of quantum well prepared in Example 2 at low temperature 75K and room temperature, X-ray diffraction curve and atomic force microscope image;

[0023] Figure 4 Fig. 5 is photoluminescence performance of quantum well prepared in Example 3 at low temperature 75K and room temperature, X-ray diffraction curve and atomic force microscope image. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0025] If not specifically indicated, the technical means used in the examples is the conventional means well known to those skilled in the art.

[0026] The present application provides a type I quantum well structure based on dipole design, in which Si donor impurities are doped at the interface of quantum well during epitaxial growth, replacing the group III elements in InGaAsSb well layer. Figure 1 In (a), the left side is a schematic diagram of quantum well energy band, and the atomic distribution at the well-barrier interface is as shown in Figure 1 As shown on the right side of (a), at the well-barrier interface, electrons flow from the low work function to the high work function, forming an interface dipole layer, and the dipole forms a positive charge density in the potential well region, and the direction of the dipole points from the inside of the semiconductor to the interface, i.e. Figure 1 As shown in (a), the dipole layer is formed at the interface of group III and group V elements, at this time, the polarization effect generated by the dipole layer can make the energy band of AlGaAsSb barrier layer move downward, increase the barrier potential well valence band step, and improve the carrier confinement ability under the premise of wavelength expansion, thereby improving the valence band step of type I quantum well.

[0027] For the InGaAsSb / AlGaAsSb I-type quantum well dipole regulation requirements, the atomic arrangement of the quantum well interface needs to be strictly controlled, that is, the InGaAsSb layer takes the III group element as the cutoff surface, and the AlGaAsSb barrier layer takes the V group element as the cutoff surface; On this basis, the donor doping Si atom needs to be strictly replaced in the III group element of the InGaAsSb layer. Through the ultrafast extraction and switching of the V group beam, the control of the crystal nucleus type and migration distance is realized. Therefore, multiple types of lattice directional migration and fusion can be realized in one molecular layer, such as Figure 1 (b) shown.

[0028] The application provides a design method based on a dipole InGaAsSb / AlGaAsSb I-type quantum well structure, Si donor impurities are doped at the quantum well interface to replace the III group elements in the InGaAsSb well layer. By increasing the positive charge density at the interface, the interface dipole strength is improved, the AlGaAsSb barrier layer band is lowered, and the I-type quantum well band step is improved. The dipole is induced at the interface during epitaxial growth, the valence band offset can reach 100-250 meV, and finally the wavelength of the laser is expanded to 3-5 μm, and the carrier confinement capability of the active region is improved, and the output power of the laser is improved.

[0029] Finally, the optical performance of the material is evaluated by photoluminescence (PL) to verify the improvement of the I-type quantum well performance induced by the "dipole" effect of the Si element introduced into the well layer.

[0030] The preparation process of the I-type quantum well structure based on the dipole design provided by the application is the design and preparation of the InAsGaSb(Si) / AlGaAsSb "dipole" quantum well, and the specific steps are as follows:

[0031] 1. Band design

[0032] In the development of quantum well materials, first of all, the band design needs to be carried out, and the band structure, strain distribution and composition parameters of the material are determined through theoretical calculation. The design goal is to optimize the band structure of the InAsGaSb(Si) / AlGaAsSb quantum well by introducing Si elements, form a dipole quantum well structure, reduce the barrier layer valence band gap, improve the restriction ability to holes, and effectively expand the wavelength.

[0033] 2. Composition and thickness design

[0034] The composition of the InAsGaSb(Si) layer and the AlGaAsSb layer is determined, such as the composition of Si (1%-5%) in InAsGaSb(Si), the thickness of the InAsGaSb(Si) layer is 10 nm, and the thickness of the AlGaAsSb layer is 20 nm.

[0035] Number of quantum well periods (designed as 3 periods) to achieve target band coverage.

[0036] 3. MBE epitaxial growth

[0037] After completing the band design, epitaxial growth of quantum well material is achieved through molecular beam epitaxy (MBE) technology. The following are the detailed growth steps:

[0038] (1) Substrate selection

[0039] Substrate selection: GaSb substrate;

[0040] Place the GaSb substrate in a beaker and clean it with ethanol and deionized water using 70 Hz frequency ultrasonic cleaning for 20 min to remove surface dust and oil stains. Then place it in a drying oven to dry the residual moisture. Place the cleaned GaSb substrate in a pre-evacuated chamber and perform a 200°C heating degassing treatment to remove adsorbed gases on the substrate surface. Transfer the preliminarily treated GaSb substrate to a buffer chamber and perform a 400°C heating treatment to further remove impurities adsorbed on the substrate surface. Open the beam monitor and block the sample holder with a baffle. Heat the source furnace required for epitaxy and measure the beam intensity of each source at different temperatures.

[0041] (2) Buffer layer: GaSb

[0042] Thickness control: 300 nm (molecular beam epitaxy MBE growth);

[0043] Transfer the GaSb substrate to the growth chamber and place it on the sample holder. Under the protection of antimony molecular beam, heat it to 600°C to remove the surface oxide layer and monitor it in real time with RHEED. According to the designed structure, grow the material layer by layer. Open the Ga source and Sb source baffle and grow the GaSb buffer layer. The growth thickness is 300 nm, the growth temperature is 550°C, the III group Ga source flux is 0.4 ML / s, the V group Sb beam is 6.8 x 10 -6 Torr; Sb / Ga beam ratio 1.05, reduce interface dislocation density.

[0044] (3) Quantum well active region (MQW Active Region): InGaAsSb(Si) / AlGaAsSb (10 nm well / 20 nm barrier) x 3

[0045] Open the shutter of Al source, In source, Si source and As source, grow 3 cycles of InGaAsSb(Si) / AlGaAsSb quantum well layer, the thickness of AlGaAsSb barrier layer is 20nm, the range of Al component is 0-1: the range of Sb component is 0-1; the thickness of InGaAsSb(Si) well layer is 10nm, In component 0-1, Sb component 0-1, Si content 1%-5%;

[0046] Close the As source, Si source, In source, Al source, close the Ga source, under the protection of Sb source beam current, reduce the growth temperature to 100℃, close the Sb source, reduce the growth temperature to room temperature, take out the sample.

[0047] (4) Post-processing: rapid thermal annealing treatment

[0048] Temperature: 400°C;

[0049] Time: 1 minute;

[0050] Purpose: to improve the crystal quality and reduce defects.

[0051] (5) Characterization

[0052] The photoluminescence performance of the quantum well is characterized by using a Fourier transform infrared spectrometer. At the same time, X-ray diffraction and atomic force microscopy are used to evaluate the crystal growth quality.

[0053] The application will be further described below in combination with specific examples.

[0054] Example 1

[0055] According to the above preparation process, InAsGaSb(Si) / AlGaAsSb "dipole" quantum well is prepared, except that: in step (3), the In 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 of the quantum well active region in 10nm well / 20nm barrier)×3 is doped with 1% Si. The specific process is as follows:

[0056] Growth temperature: 200℃ start to rise, deoxidize at 490℃ for 7min, maintain at 470℃ for 15min

[0057] Quantum well layer (well): thickness 10nm;

[0058] Kinetic parameters:

[0059] Group III source: In: 0.058 ML / s; Ga: 0.232 ML / s;

[0060] Group V source: As: 6.5 x 10 -6 Torr; Sb: 3.0 x 10 -5 Torr;

[0061] Si flux: 2.5 x 10 -8 Torr;

[0062] V / III ratio 0.95, As / Sb ratio 0.22;

[0063] Barrier: thickness 20 nm;

[0064] Kinetic parameters:

[0065] Group III source: Al: 0.135 ML / s; Ga: 0.201 ML / s

[0066] Group V source: As: 1.8 x 10 -6 Torr; Sb: 9.0 x 10 -5 Torr;

[0067] V / III ratio 1.15, As / Sb ratio 0.02.

[0068] The photoluminescence properties of the quantum well at low temperature 75 K and room temperature were characterized using a Fourier transform infrared spectrometer under the conditions of 100 mW and 100 mV, as shown in Figure 2 the center peak of the low-temperature luminescence is 3.88 pm, and the center peak of the room-temperature luminescence is 4.5 pm, the PL shows a high signal-to-noise ratio, and the luminescence performance is good. X-ray diffraction test indicates that the crystal growth quality is good; in the characterization of atomic force microscopy, the measured surface roughness Rq is 0.238 nm, which indicates that the sample has high smoothness and good surface quality.

[0069] Example 2

[0070] The same as Example 1, except that: in step (3), the quantum well active region In 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 (10 nm well / 20 nm barrier) x 3, Si doped 2%. The specific process is as follows:

[0071] Growth temperature: 200 °C ramp up, 520 °C, 7 min for desorption, 470 °C for 15 min

[0072] Quantum well layer (well): thickness 10 nm;

[0073] Kinetic parameters:

[0074] Group III source: In: 0.126 ML / s; Ga: 0.234 ML / s;

[0075] Group V source: As: 5.0 x 10 -6 Torr; Sb: 3.6 x 10 -5 Torr;

[0076] Si flux: 3.2 x 10 -8 Torr;

[0077] V / III ratio 1.10, As / Sb ratio 0.14.

[0078] Quantum barrier layer (Barrier): thickness 20 nm;

[0079] Kinetic parameters:

[0080] Group III source: Al: 0.110 ML / s; Ga: 0.204 ML / s

[0081] Group V source: As: 1.1 x 10 -6 Torr; Sb: 5.4 x 10 -5 Torr;

[0082] V / III ratio 1.20, As / Sb ratio 0.02.

[0083] The photoluminescence properties of the quantum well at low temperature 75 K and room temperature were characterized using a Fourier transform infrared spectrometer under the conditions of 100 mW and 100 mV, as shown in Figure 3 the center peak position of low temperature luminescence was 4.32 pm, the center peak position of room temperature luminescence was 4.78 pm, the PL showed high signal-to-noise ratio, and the luminescence performance was good. X-ray diffraction test indicated that the crystal growth quality was good; in the characterization of atomic force microscope, the measured surface roughness Rq was 0.245 nm, which indicated that the sample had good smoothness and good surface quality.

[0084] Example 3

[0085] The same as example 1, except that: step (3) quantum well active region In 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 (10nm well / 20nm barrier) x 3, Si doped 3%. The specific process is as follows:

[0086] Growth temperature: 200℃ start to rise, deoxidize after 505℃, 7.5min, maintain 485℃ for 15min

[0087] Quantum well layer (well): thickness 10nm;

[0088] Kinetic parameters:

[0089] Group III source: In: 0.135 ML / s; Ga: 0.251 ML / s;

[0090] Group V source: As: 8.0x10 -6 Torr; Sb: 2.9x10 -5 Torr;

[0091] Si beam current: 9.6x10 -8 Torr;

[0092] V / III ratio 1.25, As / Sb ratio 0.28;

[0093] Quantum barrier layer (Barrier): thickness 20nm;

[0094] Kinetic parameters:

[0095] Group III source: Al: 0.115 ML / s; Ga: 0.214 ML / s

[0096] Group V source: As: 1.1x10 -6 Torr; Sb: 5.4x10 -5 Torr;

[0097] V / III ratio 1.20, As / Sb ratio 0.02.

[0098] The photoluminescence performance of the quantum well at low temperature 75K and room temperature was characterized using a Fourier transform infrared spectrometer under the condition of 100mW, 100mV, as shown in Figure 4 The low-temperature luminescence center peak position is 4.73μm, and the room-temperature luminescence center peak position is 5.02μm, the PL shows high signal-to-noise ratio, and the luminescence performance is good. X-ray diffraction test indicates that the crystal growth quality is good; in the atomic force microscope characterization, the measured surface roughness Rq is 0.269 nm, which indicates that the sample has good smoothness and good surface quality.

[0099] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A method for fabricating a type-I quantum well structure based on dipole engineering design, characterized in that: including a GaSb substrate, a GaSb buffer layer and a 3-period quantum well active region In x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 wherein 0 < x1 < 1, 0 < x2 < 1, 0 < y1 < 1, 0 < y2 < 1 In x1 Ga 1-x1 As y1 Sb 1-y1 , 0 < x1 < 1, 0 < y1 < 1; quantum barrier layer is Al x2 Ga 1-x2 As y2 Sb 1-y2 , 0 < x2 < 1, 0 < y2 < 1; the quantum well layer In x1 Ga 1-x1 As y1 Sb 1-y1 doped with Si, substituting III group elements in the quantum well layer, doping amount is 1-5%.

2. The method of claim 1, wherein the method comprises: The thickness of the GaSb buffer layer is 200-300 nm. ​ 3. The method of claim 1, wherein the method comprises: The quantum well active region In x1 Ga 1-x1 As y1 Sb 1-y1 / Al x2 Ga 1-x2 As y2 Sb 1-y2 The growth temperature is: 200℃ start to heat, 500-560℃, 6min after deoxidation, 450-500℃ maintain 15min. ​ 4. The method of claim 3, wherein the method further comprises: The quantum well active region In 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 alternately grown for 3 periods, the thickness of the quantum well layer is 10 nm, and the thickness of the quantum barrier layer is 20 nm.

5. The method of claim 1 to 4, wherein the method is characterized by: The prepared quantum well is subjected to rapid thermal annealing treatment, the annealing temperature is 400 DEG C, and the time is 1 min.

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