Surface high-power high-speed directly-modulated quantum dot laser and preparation method thereof

Abstract

The invention specifically discloses a surface high-power high-speed directly-modulated quantum dot laser and a preparation method thereof, an N-type GaAs substrate is sent into an MBE cavity to remove an oxide layer on the surface, and an N-type GaAs contact layer, an N-type AlGaAs limiting layer, a first undoped GaAs waveguide layer, a multi-layer quantum dot active region, a second undoped GaAs waveguide layer and a P-type AlGaAs limiting layer are sequentially grown on the N-type GaAs substrate with the oxide layer on the surface removed. And a P-type GaAs contact layer is formed, so that the surface high-power high-speed directly-modulated quantum dot laser is obtained. According to the method, the number of layers of the quantum dots is greatly increased by accurately controlling the growth conditions of the quantum dots and the thickness of the spacer layer, and the thickness of the active area of the quantum dots is controlled at the same time, so that the differential gain and the carrier injection efficiency of the quantum dots are increased, and the direct modulation rate and the light output power of the quantum dot laser are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of epitaxial growth of semiconductor materials, and particularly relates to a face-phase high-power high-speed direct modulation quantum dot laser and a preparation method thereof. BACKGROUND

[0002] With the rapid development of 5G / 6G communication and data center optical interconnection technology, the optical communication system puts forward urgent needs for core light sources, i.e., lasers, with higher bandwidth, lower power consumption, stronger temperature stability and lower noise. These performance indicators directly determine the transmission rate, noise margin and energy efficiency level of the optical communication system. Among them, the O-band (1260-1360 nm) has become the preferred band for short-distance high-speed optical interconnection due to its low dispersion characteristics.

[0003] InAs quantum dot lasers exhibit significant advantages due to their three-dimensional quantum confinement effect: ultra-low threshold current density, high differential gain, wide gain spectrum, and excellent high-temperature stability. These characteristics make them extremely promising in high-efficiency optical communication, silicon-based photonic integration, and high-temperature application scenarios. Compared with schemes that require external modulators, high-power, directly modulated lasers are particularly suitable for large-scale production and short-distance optical communication applications due to their low cost, small size, and low power consumption. However, the direct modulation bandwidth of current quantum dot lasers still cannot meet the stringent demands of 5G / 6G communication and data centers for ultra-high-speed modulation, which has become a key bottleneck limiting their widespread application.

[0004] The modulation rate bottleneck of quantum dot lasers mainly originates from material growth kinetics limitations and carrier transport mechanisms: (1) Material growth uniformity challenge: During MBE (Molecular Beam Epitaxy) or MOCVD (Metal-organic Chemical Vapor Deposition) growth processes, the size uniformity and density of quantum dots are difficult to accurately control, which leads to uneven distribution of localized state density, causing thermal escape of carriers and wet layer assisted non-radiative recombination, reducing device efficiency; (2) Carrier transport problem in multi-layer structure: The modulation rate of quantum dot lasers is closely related to the differential gain of the active region. Traditional methods often increase the number of quantum dot layers to improve the differential gain and total gain. However, to isolate interlayer stress transmission, multi-layer quantum dot structures require thicker GaAs (gallium arsenide) spacer layers, which severely hinder carrier longitudinal transport efficiency, thereby limiting the improvement of direct modulation rate.

[0005] Therefore, by means of the innovative quantum dot epitaxial growth technology, the problems of quantum dot size / density uniformity control, strain management optimization and high-efficiency carrier transport are systematically solved, so that the direct modulation bandwidth is significantly improved while the high output power is maintained, which has become the core key to promote the quantum dot laser to achieve breakthrough development in the field of high-speed communication. SUMMARY

[0006] The purpose of the present application is to control the thickness of the GaAs spacer layer of the quantum dot active region and the total thickness of the quantum dot active region while improving the number of quantum dot layers by optimizing the epitaxial growth method of the InAs quantum dot active region, to increase the carrier injection efficiency, and to improve the light output power and direct modulation rate of the quantum dot laser.

[0007] To achieve the above purpose, the present application provides a preparation method of a high-power high-speed direct modulation quantum dot laser on one side, which comprises the following steps: S1, sending an N-type GaAs substrate into an MBE chamber, and removing the oxide layer on the surface of the N-type GaAs substrate by high temperature in the MBE chamber; S2, growing an N-type GaAs contact layer on the N-type GaAs substrate with the surface oxide layer removed; S3, growing an N-type AlGaAs confinement layer on the N-type GaAs contact layer; S4, epitaxially growing a first undoped GaAs waveguide layer on the N-type AlGaAs confinement layer; S5, epitaxially growing a multilayer quantum dot active region on the first undoped GaAs waveguide layer; S6, epitaxially growing a second undoped GaAs waveguide layer on the multilayer quantum dot active region; S7, growing a P-type AlGaAs confinement layer on the second undoped GaAs waveguide layer; S8, growing a P-type GaAs contact layer on the P-type AlGaAs confinement layer, thereby obtaining a high-power high-speed direct modulation quantum dot laser.

[0008] Preferably, the specific implementation of the step S1 is to send the N-type GaAs substrate into the MBE chamber with a temperature of 500-700 DEG C for high-temperature deoxidation treatment to remove the oxide layer on the surface of the N-type GaAs substrate.

[0009] Preferably, the specific implementation of the step S2 is to control the temperature in the MBE chamber to be between 500-700 DEG C, and to epitaxially grow a layer of N-type GaAs contact layer with a thickness of 300 nm on the N-type GaAs substrate with the surface oxide layer removed, the growth rate of GaAs being 0.1-1 ML / s, the impurity for doping being Si, and the doping concentration being 1x10 18 –2x10 19 cm-3 between.

[0010] Preferably, step S3 is specifically implemented as follows: controlling the temperature inside the MBE cavity between 550-700℃, and growing an N-type Al layer with a thickness of 1-1.5µm on the N-type GaAs contact layer. x Ga 1-x As the confinement layer, Al x Ga 1-x The growth rate of As is 0.1–1 mL / s, the value of x ranges from 0.2 to 0.5, the impurity is Si, and the doping concentration is 5 × 10⁻⁶. 17 –1×10 19 cm -3 between.

[0011] Preferably, step S4 is specifically implemented by controlling the temperature inside the MBE cavity between 500-700℃, in N-type Al x Ga 1-x An undoped GaAs waveguide layer with a thickness of 30-50 nm is epitaxially grown on the As confinement layer at a growth rate of 0.1-1 mL / s.

[0012] Preferably, the multilayer quantum dot active region in step S5 includes several active regions and several graded active regions. The specific implementation of S5 is as follows: S51. Preset the total number of growth layers n in the quantum dot active region, the number of growth layers m in the active region, and the number of growth layers nm in the gradient active region; S52. On the first undoped GaAs waveguide layer, m active regions are epitaxially grown using a fixed quantum dot growth method, with each active region having a thickness of 22-28 nm. S53. Starting from the (m+1)th layer, the quantum dot growth temperature, As / In ratio, and P-type GaAs are adjusted using gradient control. z P 1-z The growth method of z in the capping layer involves epitaxially growing a gradient active region layer by layer on the m-layer active region until the total number of grown layers of the gradient active region reaches nm layers, thereby obtaining a multilayer quantum dot active region with a total thickness ≤350nm.

[0013] Preferably, the first active region in the m-layer active region in step S52 is specifically implemented as follows: S521. Control the temperature inside the MBE cavity between 400-500℃, and epitaxially grow an undoped In layer with a thickness of 1-2nm on the first undoped GaAs waveguide layer. y Ga 1-y As the impregnation layer, the growth rate is 0.1-1 mL / s, and the value of y ranges from 0.1 to 0.16. S522, control the temperature in the MBE chamber between 400-500℃, control the ratio of As:In between 10-30, and grow N-type doped quantum dots in In y Ga 1-y As wetting layer S523, control the temperature in the MBE chamber between 400-500℃, and grow a 1-3nm-thick undoped In y Ga 1-y As cap layer on the N-type doped quantum dots, with a growth rate of 0.1-1ML / s and y ranging between 0.15-0.2 S524, grow a first undoped GaAs cap layer on the undoped In y Ga 1-y As cap layer S525, control the temperature in the MBE chamber between 550-700℃, and grow a 5-10nm-thick P-type GaAs z P 1-z cap layer on the first undoped GaAs cap layer, with a growth rate of 0.1-1ML / s, z ranging between 0.05-0.1, P-type doping, Be as the doping element, and a doping amount of 8-15 holes per quantum dot S526, control the temperature in the MBE chamber between 550-700℃, and grow a 1-5nm-thick second undoped GaAs cap layer on the P-type GaAs z P 1-z cap layer, with a growth rate of 0.1-1ML / s, thereby obtaining a first active region layer with a thickness of 22-28nm.

[0014] Preferably, the step S7 is implemented by controlling the temperature in the MBE chamber between 550-700℃, and growing a 500-1500nm-thick P-type Al x Ga 1-x As confinement layer on the second undoped GaAs waveguide layer, with a growth rate of 0.1-1ML / s, x ranging between 0.2-0.5, a doping concentration of 5×10 17 –1×10 19 cm -3 , and Be as the doping element.

[0015] Preferably, the step S8 is implemented by controlling the temperature in the MBE chamber between 450-550℃, and growing a 500-1500nm-thick P-type Al x Ga 1-xAs restrict layer, the P-type GaAs contact layer with the thickness of 300-500nm is epitaxially grown on the restrict layer, the growth rate is 0.1-1ML / s, the doping concentration is 1×10 18 -5×10 19 cm -3 , and the impurity is Be.

[0016] The application also provides a planar high-power high-speed direct modulation quantum dot laser prepared by the preparation method of the planar high-power high-speed direct modulation quantum dot laser.

[0017] In the application, the N-type GaAs substrate is sent into an MBE chamber, the surface oxide layer of the N-type GaAs substrate is removed by high temperature in the MBE chamber, and then the N-type GaAs contact layer, the N-type AlGaAs restrict layer, the first undoped GaAs waveguide layer, the multi-layer quantum dot active region, the second undoped GaAs waveguide layer, the P-type AlGaAs restrict layer and the P-type GaAs contact layer are sequentially grown on the N-type GaAs substrate from which the surface oxide layer is removed, so that the planar high-power high-speed direct modulation quantum dot laser is obtained. By controlling the growth conditions of the quantum dots and the thickness of the spacer layer, the thickness of the quantum dot active region is controlled while the number of layers of the quantum dots is greatly increased, so that the differential gain of the quantum dots, the carrier injection efficiency and the light output power and the direct modulation rate of the quantum dot laser are greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a flow chart of a preparation method of a planar high-power high-speed direct modulation quantum dot laser according to the application; Figure 2 is a structural schematic diagram of a planar high-power high-speed direct modulation quantum dot laser according to the application; Figure 3 is a structural schematic diagram of each active region in the application; Figure 4 is a comparison diagram of the influence of undoped and N-type doped quantum dots on the light emitting characteristics according to an embodiment of the application. DETAILED DESCRIPTION

[0019] In order to make the person skilled in the art better understand the technical solutions of the application, the application will be further described in detail below with reference to the drawings.

[0020] Figure 1 shows a flow chart of a preparation method of a planar high-power high-speed direct modulation quantum dot laser according to the application; Figure 2 shows a structural schematic diagram of a planar high-power high-speed direct modulation quantum dot laser according to the application.

[0021] In one embodiment, a preparation method of a planar high-power high-speed direct modulation quantum dot laser comprises the following steps: S1, sending an N-type GaAs substrate into an MBE chamber, removing the oxide layer on the surface of the N-type GaAs substrate by high temperature in the MBE chamber; S2, growing an N-type GaAs contact layer on the N-type GaAs substrate with the surface oxide layer removed; S3, growing an N-type AlGaAs confinement layer on the N-type GaAs contact layer; S4, epitaxially growing a first undoped GaAs waveguide layer on the N-type AlGaAs confinement layer; S5, epitaxially growing a multilayer quantum dot active region on the first undoped GaAs waveguide layer; S6, epitaxially growing a second undoped GaAs waveguide layer on the multilayer quantum dot active region; S7, growing a P-type AlGaAs confinement layer on the second undoped GaAs waveguide layer; S8, growing a P-type GaAs contact layer on the P-type AlGaAs confinement layer, thereby obtaining a face-type high-power high-speed direct modulation quantum dot laser.

[0022] Specifically, the substrate can be an N-type substrate or a semi-insulating substrate, for example, N-type, semi-insulating (SI) type and Si (silicon) substrates of GaAs (gallium arsenide) are all applicable. Taking the N-type GaAs substrate as an example, the N-type GaAs (gallium arsenide) substrate is sent into the MBE chamber, the oxide layer on the surface of the N-type GaAs substrate is removed by high temperature in the MBE chamber, and then an N-type GaAs contact layer, an N-type AlGaAs confinement layer, a first undoped GaAs waveguide layer, a multilayer quantum dot active region, a second undoped GaAs waveguide layer, a P-type AlGaAs confinement layer and a P-type gallium arsenide contact layer are sequentially grown on the N-type GaAs substrate with the surface oxide layer removed.

[0023] In one embodiment, the specific implementation of step S1 is to send the N-type GaAs substrate into the MBE chamber with a temperature of 500-700°C for high-temperature deoxidation treatment to remove the oxide layer on the surface of the N-type GaAs substrate.

[0024] Specifically, the N-type GaAs substrate is sent into the MBE chamber, and the oxide layer on the surface of the N-type GaAs substrate is removed by high temperature (500-700°C) in the MBE chamber.

[0025] In one embodiment, the specific implementation of step S2 is to control the temperature in the MBE chamber to be between 500-700°C, and epitaxially grow a N-type GaAs contact layer with a thickness of 300 nm on the N-type GaAs substrate with the surface oxide layer removed, the growth rate of GaAs is 0.1-1 ML / s (i.e. monolayer / second), the impurity doped is Si, and the doping concentration is 1×1018-2×1019cm-3. 18 –2×10 19 cm-3 between.

[0026] Specifically, a 300 nm thick GaAs contact layer is epitaxially grown on an N-type GaAs substrate with the surface oxide layer removed at a growth rate of 0.1-1 mL / s and a doping concentration of 1 × 10⁻⁶. 18 –2×10 19 cm -3 The doping method is N-type doping (N-type doping is Si doping), and the growth temperature is between 500-700℃.

[0027] In one embodiment, step S3 is specifically implemented as follows: controlling the temperature inside the MBE cavity between 550-700℃, and growing an N-type Al layer with a thickness of 500nm-1.5µm on the N-type GaAs contact layer. x Ga 1-x As the confinement layer, Al x Ga 1-x The growth rate of As is 0.1–1 mL / s, the value of x ranges from 0.2 to 0.5, the impurity is Si, and the doping concentration is 5 × 10⁻⁶. 17 –1×10 19 cm -3 between.

[0028] Specifically, an N-type Al layer with a thickness of 500 nm to 1.5 µm is epitaxially grown on the N-type GaAs contact layer. x Ga 1-x As confinement layer, growth rate is 0.1-1 mL / s, x value is between 0.2-0.5, doping concentration is 5 × 10⁻⁶. 17 –1×10 19 cm -3 The growth temperature is between 550-700℃.

[0029] In one embodiment, step S4 is specifically implemented as follows: controlling the temperature inside the MBE cavity between 500-700℃, in N-type Al x Ga 1-x An undoped GaAs waveguide layer with a thickness of 30-50 nm is epitaxially grown on the As confinement layer at a growth rate of 0.1-1 mL / s.

[0030] Specifically, in N-type Al x Ga 1-x An undoped GaAs waveguide layer with a thickness of 30-50 nm is epitaxially grown on the As confinement layer at a growth rate of 0.1-1 mL / s and a growth temperature of 500-700 °C.

[0031] In one embodiment, the multilayer quantum dot active region in step S5 comprises a plurality of layers of active regions and a plurality of layers of graded active regions, and the specific implementation of S5 is as follows: S51, preset the total number of growth layers n of the quantum dot active region, the number of growth layers m of the active region, and the number of growth layers n-m of the graded active region.

[0032] S52, epitaxially grow m (m < n) layers of active regions on the first undoped GaAs waveguide layer in a fixed quantum dot growth mode, and the thickness of each layer of active region is 22-28 nm.

[0033] Further, referring to Figure 3 , the specific implementation of the first active region in the m layers of active regions in step S52 is as follows: S521, control the temperature in the MBE chamber to be between 400-500°C, and epitaxially grow a layer of undoped In y Ga 1-y As wetting layer with a thickness of 1-2 nm on the first undoped GaAs waveguide layer, and the growth rate is 0.1-1 ML / s, and the value range of y is 0.1-0.16.

[0034] S522, control the temperature in the MBE chamber to be between 400-500°C, and control the ratio of As:In to be 10-30, and epitaxially grow N-type doped quantum dots on the undoped In y Ga 1-y As wetting layer, and the impurity doped is Si.

[0035] Specifically, control the temperature in the MBE chamber to be between 400-500°C, and control the ratio of As:In to be 10-30, and first epitaxially grow 11-15s quantum dots on the undoped In y Ga 1-y As wetting layer, and then in an As-rich environment, open the In shutter and keep it closed for 0.3-0.5s, then open the Si shutter and keep it closed for 0.5-1s, and then N-type dope the quantum dots, the doping concentration is 0.4-1.2 electrons per quantum dot, and the total growth time of the quantum dots is controlled to be 18-20s, thereby obtaining N-type doped quantum dots.

[0036] S523, control the temperature in the MBE chamber to be between 400-500°C, and epitaxially grow a layer of undoped In y Ga 1-y As cap layer with a thickness of 1-3 nm on the N-type doped quantum dots, and the growth rate is 0.1-1 ML / s, and the value range of y is 0.15-0.2.

[0037] S524, epitaxially grow a first undoped GaAs cap layer on the undoped In y Ga 1-y As cap layer.

[0038] Specifically, the temperature in the MBE chamber is controlled between 400-500℃, and undoped In y Ga 1-y A low-temperature undoped GaAs cap layer with a thickness of 5-10nm is epitaxially grown on the GaAs cap layer; the pressure of As is controlled between 1x10 -5 -2x10 -5 mbar, the temperature in the MBE chamber is raised to 550-700℃, and a high-temperature undoped GaAs cap layer with a thickness of 5-10nm is epitaxially grown on the low-temperature undoped GaAs cap layer, and the low-temperature undoped GaAs cap layer and the high-temperature undoped GaAs cap layer together form a first undoped GaAs cap layer.

[0039] S525, the temperature in the MBE chamber is controlled between 550-700℃, and a P-type GaAs z P 1-z cap layer with a thickness of 5-10nm is epitaxially grown on the first undoped GaAs cap layer, the growth rate is 0.1-1ML / s, the value of z is in the range of 0.05-0.1, the doping mode is P-type doping, the doping element is Be, and the control of the doping amount is 8-15 holes / quantum dot.

[0040] S526, the temperature in the MBE chamber is controlled between 550-700℃, and a second undoped GaAs cap layer with a thickness of 1-5nm is epitaxially grown on the P-type GaAs z P 1-z cap layer, the growth rate is 0.1-1ML / s, thereby obtaining a first active region layer with a thickness of 22-28nm.

[0041] The growth mode of S521 to S526 is cycled m times to obtain m layers of active regions. For example, when m=6, the above-mentioned mode is cycled 6 times to obtain 6 layers of active regions.

[0042] S53, starting from the m+1 layer, the growth temperature of the quantum dot, the As / In ratio, and the proportion of z in the P-type GaAs z P 1-z cap layer are adjusted by gradient, and a gradual change active region is epitaxially grown on the m layers of active region layers layer by layer until the total number of growth layers of the gradual change active region reaches n-m layers, thereby obtaining a multilayer quantum dot active region with a total thickness less than or equal to 350nm.

[0043] Specifically, after 6 active regions are grown in a cycle, it is found that growing the 7th layer of quantum dots will cause vertical coupling of quantum dots, which is specifically manifested in the reduction of quantum dot density, sharp increase of quantum dot size and light-emitting wavelength, and great decline of quantum dot uniformity, which in turn leads to rapid widening of half-wave width. Starting from the 7th layer and up to the nth layer, the growth conditions remain unchanged, and the quantum dot growth temperature, As / In ratio and P-type GaAs z P 1-z The ratio of z in the cap layer is specifically: the growth temperature is reduced by 2-5℃ and the As / In ratio is increased by 2-6 for each additional layer of quantum dot active region. z P 1-z The ratio of z in the cap layer is 0.1+ (n-m) x 0.05. For example, when the As / In ratio is controlled to be 30 during the production of the first six layers of active region, the As / In ratio of each gradient active region is increased by 5 starting from the growth of the 7th layer of gradient active region, and the As / In ratio of the nth layer of gradient active region is (n-6) x 5+30. If the growth temperature of the first six layers of active region is 460℃, the temperature from the 7th layer of gradient active region to the nth layer of gradient active region is 460℃-(n-6) x 2℃. Starting from the 7th layer of gradient active region, the P-type GaAs z P 1-z The ratio of z in the cap layer is specifically: the growth temperature is reduced by 2-5℃ and the As / In ratio is increased by 2-6 for each additional layer of quantum dot active region. z P 1-z The ratio of z in the cap layer is 0.1+ (n-m) x 0.05. By increasing the proportion of phosphorus, the stress conduction is controlled, and the stress conduction to the upper layer of gradient active region is greatly inhibited.

[0044] The main purpose of the above method is to force the quantum dots to grow randomly rather than to increase the size of the existing quantum dots by inhibiting the drift distance of As during the nucleation process of quantum dots, thereby inhibiting the stress conduction caused by the spacer layer (i.e. the undoped In y Ga 1-y As cap layer, first undoped GaAs cap layer, P-type GaAs z P 1-z cap layer, second undoped GaAs cap layer) and prevent the formation of columnar quantum dot stacking growth.

[0045] In combination with the above growth conditions, the total number of multilayer quantum dot active regions is controlled to be between 10-15 layers to maintain the total active region thickness between 300-350nm.

[0046] Referring to Figure 4 , Figure 4Figure 2 is a comparison chart of the influence of undoped and N-type doping on the luminescent characteristics of quantum dots in an embodiment of the present application. Figure 4 It can be seen that the above method optimizes the quantum dot density, uniformity, photoluminescence intensity of single-layer quantum dots, and total quantum dot layer number, thereby improving the differential gain of the quantum dots, and further increasing the line width broadening factor of the quantum dots, the light output power of the quantum dot laser, and the direct modulation rate.

[0047] In one embodiment, the step S7 is specifically implemented as follows: controlling the temperature in the MBE cavity to be between 550-700℃, and epitaxially growing a P-type AlxGa1-xAs confinement layer with a thickness of 500-1500nm on the second undoped GaAs waveguide layer, the growth rate of the AlxGa1-xAs being 0.1-1ML / s, x being 0.2-0.5, the doping concentration being 5×10 x Ga 1-x As, and the impurity being Be. 17 –1×10 19 cm -3 .

[0048] Specifically, the temperature is kept unchanged, and a second undoped GaAs waveguide layer is epitaxially grown on the multilayer quantum dot active region, the growth rate being 0.1-1ML / s, and a P-type AlxGa1-xAs confinement layer with a thickness of 500-1500nm is epitaxially grown on the second undoped GaAs waveguide layer, the growth rate of the AlxGa1-xAs being 0.1-1ML / s, x being 0.2-0.5, the doping concentration being 5×10 x Ga 1-x As, the growth temperature being 550-700℃, and the doping mode being Be doping. x –1×10 1-x cm 17 . 19 -3

[0049] In one embodiment, the step S8 is specifically implemented as follows: controlling the temperature in the MBE cavity to be between 450-550℃, and epitaxially growing a P-type GaAs contact layer with a thickness of 300-500nm on the P-type AlxGa1-xAs confinement layer, the growth rate being 0.1-1ML / s, the doping concentration being 1×10 x Ga 1-x As, and the impurity being Be. 18 –5×10 19 cm -3 .

[0050] Specifically, a P-type GaAs contact layer with a thickness of 300-500nm is epitaxially grown on the P-type AlxGa1-xAs confinement layer, the growth rate being 0.1-1ML / s, the doping concentration being 1×10 x Ga 1-x ​​As restricts the layer epitaxial growth a thickness of 300-500nm P-type GaAs contact layer, the growth rate is 0.1-1ML / s, P-type doping doping concentration is 1x10 18 -5x10 19 cm -3 , growth temperature is 450-550℃.

[0051] The preparation method of the above-mentioned surface large-power high-speed direct modulation quantum dot laser controls the growth conditions of the quantum dots and the thickness of the spacer layer, controls the thickness of the quantum dot active region while greatly increasing the number of quantum dot layers, and further increases the differential gain of the quantum dots, the carrier injection efficiency, and greatly improves the direct modulation rate of the quantum dot laser.

[0052] In one embodiment, a surface large-power high-speed direct modulation quantum dot laser is prepared using the preparation method of the surface large-power high-speed direct modulation quantum dot laser as described above.

[0053] In addition, in the present application, the epitaxial preparation tool can be replaced by an organic metal chemical vapor deposition method, and the quantum dot crystal quality prepared by the organic metal chemical vapor deposition method is poor. In addition, the N-type gallium arsenide substrate in the present application can also be replaced by a semi-insulating GaAs substrate or a Si substrate. If epitaxy is performed on a Si substrate, a GaAs / AlGaAs superlattice filter layer needs to be added.

[0054] In the present application, an N-type GaAs (gallium arsenide) substrate is sent into an MBE chamber, the surface oxide layer of the N-type GaAs substrate is removed by high temperature in the MBE chamber, and an N-type GaAs contact layer, an N-type AlGaAs restriction layer, a first undoped GaAs waveguide layer, a multi-layer quantum dot active region, a second undoped GaAs waveguide layer, a P-type AlGaAs restriction layer, and a P-type GaAs contact layer are sequentially grown on the N-type GaAs substrate from which the surface oxide layer is removed, thereby obtaining a large-power high-speed direct modulation quantum dot laser. The method controls the growth conditions of the quantum dots and the thickness of the spacer layer, controls the thickness of the quantum dot active region while greatly increasing the number of quantum dot layers, and further increases the differential gain of the quantum dots, the carrier injection efficiency, and greatly improves the light output power and the direct modulation rate of the quantum dot laser.

[0055] The surface large-power high-speed direct modulation quantum dot laser and the preparation method thereof provided by the present application are described in detail above. In this paper, specific examples are applied to describe the principles and implementation modes of the present application, and the above examples are only used to help understand the core idea of the present application. It should be pointed out that for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for fabricating a planar high-power, high-speed, directly modulated quantum dot laser, characterized in that, The method includes the following steps: S1. The N-type GaAs substrate is sent into the MBE cavity, and the oxide layer on the surface of the N-type GaAs substrate is removed by the high temperature in the MBE cavity. S2. An N-type GaAs contact layer is grown on an N-type GaAs substrate with the surface oxide layer removed; S3. Grow an N-type AlGaAs confinement layer on the N-type GaAs contact layer; S4. Epitaxially grow the first undoped GaAs waveguide layer on the N-type AlGaAs confinement layer; S5. Epitaxially grow a multilayer quantum dot active region on the first undoped GaAs waveguide layer; S6. Epitaxially grow a second undoped GaAs waveguide layer on the active region of a multilayer quantum dot; S7. Grow a P-type AlGaAs confinement layer on the second undoped GaAs waveguide layer; S8. A P-type GaAs contact layer is grown on a P-type AlGaAs confinement layer to obtain a surface-mount high-power, high-speed, directly modulated quantum dot laser.

2. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 1, characterized in that, The specific implementation of step S1 is as follows: the N-type GaAs substrate is sent into the MBE cavity at a temperature between 500-700℃ for high-temperature deoxidation treatment to remove the oxide layer on the surface of the N-type GaAs substrate.

3. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 2, characterized in that, The specific implementation of step S2 is as follows: The temperature inside the MBE cavity is controlled between 500-700℃. An N-type GaAs contact layer with a thickness of 300nm is epitaxially grown on an N-type GaAs substrate with the surface oxide layer removed. The GaAs growth rate is 0.1–1 ML / s, and the impurity is Si with a doping concentration of 1×10⁻⁶. 18 –2×10 19 cm -3 between.

4. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 3, characterized in that, The specific implementation of step S3 is as follows: controlling the temperature inside the MBE cavity between 550-700℃, and growing an N-type Al layer with a thickness of 1-1.5µm on the N-type GaAs contact layer. x Ga 1-x As the confinement layer, Al x Ga 1-x The growth rate of As is 0.1–1 mL / s, the value of x ranges from 0.2 to 0.5, the impurity is Si, and the doping concentration is 5 × 10⁻⁶. 17 –1×10 19 cm -3 between.

5. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 4, characterized in that, The specific implementation of step S4 is as follows: controlling the temperature inside the MBE cavity between 500-700℃, in N-type Al... x Ga 1-x An undoped GaAs waveguide layer with a thickness of 30-50 nm is epitaxially grown on the As confinement layer at a growth rate of 0.1-1 mL / s.

6. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 5, characterized in that, The multi-layer quantum dot active region in step S5 includes several active regions and several gradient active regions. The specific implementation of S5 is as follows: S51. Preset the total number of growth layers n in the quantum dot active region, the number of growth layers m in the active region, and the number of growth layers nm in the gradient active region; S52. On the first undoped GaAs waveguide layer, m active regions are epitaxially grown using a fixed quantum dot growth method, with each active region having a thickness of 22-28 nm. S53. Starting from the (m+1)th layer, the quantum dot growth temperature, As / In ratio, and P-type GaAs are adjusted using gradient control. z P 1-z The growth method of z in the capping layer involves epitaxially growing a gradient active region layer by layer on the m-layer active region until the total number of grown layers of the gradient active region reaches nm layers, thereby obtaining a multilayer quantum dot active region with a total thickness ≤350nm.

7. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 6, characterized in that, The specific implementation method of the first active region in the m-layer active region in step S52 is as follows: S521. Control the temperature inside the MBE cavity between 400-500℃, and epitaxially grow an undoped In layer with a thickness of 1-2nm on the first undoped GaAs waveguide layer. y Ga 1-y As the impregnation layer, the growth rate is 0.1-1 mL / s, and the value of y ranges from 0.1 to 0.

16. S522. Control the temperature inside the MBE cavity between 400-500℃, and control the As:In ratio to be 10-30, in the absence of In doping. y Ga 1- y N-type doped quantum dots are epitaxially grown in the As wetted layer, with Si as the impurity. S523. Control the temperature inside the MBE cavity between 400-500℃, and epitaxially grow an undoped In layer with a thickness of 1-3nm on the N-type doped quantum dots. y Ga 1-y As capping layer, growth rate is 0.1-1 mL / s, and y ranges from 0.15 to 0.2; S524, in undoped In y Ga 1-y The first undoped GaAs capping layer is epitaxially grown on the As capping layer; S525. Control the temperature inside the MBE cavity between 550-700℃, and epitaxially grow a 5-10nm thick P-type GaAs layer on the first undoped GaAs capping layer. z P 1-z The cap layer has a growth rate of 0.1-1 mL / s, a z value ranging from 0.05 to 0.1, is p-type doped with Be as the dopant element, and has a doping concentration of 8-15 holes / quantum dots. S526. Control the temperature inside the MBE cavity between 550-700℃ in P-type GaAs. z P 1-z A second undoped GaAs capping layer with a thickness of 1-5 nm is epitaxially grown on the capping layer at a growth rate of 0.1-1 mL / s, thereby obtaining a first active region layer with a thickness of 22-28 nm.

8. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 7, characterized in that, The specific implementation of step S7 is as follows: controlling the temperature inside the MBE cavity between 550-700℃, and epitaxially growing a P-type Al layer with a thickness of 500-1500nm on the second undoped GaAs waveguide layer. x Ga 1-x As confinement layer, growth rate 0.1-1 mL / s, x 0.2-0.5, doping concentration 5 × 10⁻⁶ 17 –1×10 19 cm -3 The impurity is Be.

9. The method for fabricating a planar high-power high-speed directly modulated quantum dot laser as described in claim 8, characterized in that, The specific implementation of step S8 is as follows: controlling the temperature inside the MBE cavity between 450-550℃, in the P-type Al... x Ga 1-x A p-type GaAs contact layer with a thickness of 300-500 nm is epitaxially grown on the As confinement layer at a growth rate of 0.1-1 mL / s and a doping concentration of 1 × 10⁻⁶. 18 –5×10 19 cm -3 The impurity is Be.

10. A planar high-power high-speed directly modulated quantum dot laser, characterized in that, The quantum dot laser is fabricated using the fabrication method of the planar high-power high-speed direct-modulation quantum dot laser as described in any one of claims 1 to 9.

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