Asymmetric spin injection vertical cavity surface emitter and preparation method thereof

Abstract

The invention discloses an asymmetric spin injection vertical cavity surface emitter and a preparation method thereof, and belongs to the technical field of semiconductor lasers, the emitter comprises a GaAs substrate, a GaNnAs spin enhancement layer, a GaAs transition layer and an asymmetric heterogeneous barrier structure, the GaNnAs spin enhancement layer and the GaAs transition layer are sequentially grown on the substrate, the asymmetric heterogeneous barrier structure is prepared on the surface of the transition layer, the asymmetric heterogeneous barrier structure is composed of an Al2O3 insulating layer and an MgO tunneling layer, wherein the Al2O3 insulating layer is used for blocking electrons from passing through, and the MgO tunneling layer is used for allowing electrons in a specific spinning direction to pass through in a tunneling manner. A Pt spin Hall effect generation layer is deposited on the heterogeneous barrier structure, a transverse strip-shaped electrode is formed, and a lower DBR reflector, an active layer, an oxidation limiting layer and an upper DBR reflector are sequentially grown above the transverse strip-shaped electrode. According to the invention, by introducing the quantum Hall effect and the heterogeneous barrier structure of the non-magnetic material, direct electric control of the polarization state of the VCSEL is realized, the spin injection efficiency and the polarization control capability are improved, and the compatibility with the existing VCSEL process is maintained at the same time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and in particular to an asymmetric spin-injected vertical cavity surface emitter and its fabrication method. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs), as a novel type of semiconductor laser, have been widely used in optical communication, sensing, optical interconnects, lidar, and many other fields due to their numerous advantages, including low threshold current, low power consumption, fast modulation speed, excellent beam quality, and low cost. However, traditional gallium arsenide-based VCSELs, due to crystal symmetry and competition for higher-order modes, cannot achieve stable control over the polarization direction of the output laser, typically exhibiting a dual-polarization state or unstable polarization state. This uncontrolled polarization phenomenon severely restricts the performance of VCSELs in applications with strict requirements for polarization stability and a single polarization mode, such as high-precision optical components, atomic sensing, and quantum communication.

[0003] To effectively address the polarization control problem of VCSELs, researchers have proposed a series of improvement schemes. One common approach is to introduce asymmetric structures within the resonant cavity, such as surface gratings or non-circular oxide apertures, to selectively suppress one polarization mode by artificially introducing birefringence, thereby achieving single-polarization output. These passive polarization control methods improve the polarization stability of VCSELs to some extent, but they still have significant limitations when facing high-speed modulation and large-scale integrated applications.

[0004] Meanwhile, the concept of "spin laser" has emerged in recent years, opening up entirely new avenues for polarization control of VCSELs. The principle of spin-injected VCSELs is to inject electrons (or holes) with specific spin directions into the active region, enabling the lasing light to acquire a corresponding circularly polarized state or polarization-selective gain. This method holds promise for achieving high-speed, direct polarization modulation, which can be used to encode polarized qubits in quantum communication and is also of paramount importance in integrated photonics.

[0005] Currently, achieving spin-polarized carrier injection mainly relies on ferromagnetic materials or magnetically doped semiconductors as spin injection sources. For example, ferromagnetic electrodes or spin injection layers are introduced into VCSEL structures, and their spontaneous magnetization generates spin-polarized electrons in a specific direction. However, this approach has several significant drawbacks. First, the ferromagnetic material needs to be kept magnetized at room temperature, and the device's operation is easily affected by external magnetic fields and temperature disturbances, leading to highly unstable spin injection efficiency. Simultaneously, the magnetic components themselves introduce additional noise and losses, thus affecting the overall performance of the laser. Second, the heterogeneous integration process of the ferromagnetic layer and the semiconductor is complex and may introduce interface defects and stress, reducing device reliability. Furthermore, some studies have attempted to use optical methods (such as circularly polarized pumping) to generate spin carriers, but optical pumping systems are not only complex but also difficult to integrate.

[0006] In summary, under current technological conditions, there is a lack of efficient spin injection schemes that do not require traditional ferromagnetic materials and are easily integrated to achieve direct electrical control of the polarization state of VCSELs. Therefore, there is an urgent need to develop a novel asymmetric spin-injection vertical-cavity surface emitter (VCSEL) capable of generating and injecting carriers with selected spin polarization directions into VCSELs without the need for ferromagnetic materials, thereby achieving effective control of the laser polarization state to meet the growing demand for high-performance optoelectronic devices. Summary of the Invention

[0007] The purpose of this invention is to provide an asymmetric spin-injected vertical cavity surface emitter (VCSEL) and its fabrication method, thereby overcoming the shortcomings of existing VCSELs, such as unstable polarization control and the low efficiency and poor compatibility of traditional spin injection methods. To this end, this invention provides the following technical solution:

[0008] In one aspect, the present invention provides an asymmetric spin-injected vertical cavity surface emitter, comprising a GaAs substrate; a GaMnAs spin enhancement layer and a GaAs transition layer, wherein the GaMnAs spin enhancement layer and the GaAs transition layer are sequentially grown on the GaAs substrate; an asymmetric hetero barrier structure, comprising an Al2O3 insulating layer and an MgO tunneling layer, wherein the Al2O3 insulating layer and the MgO tunneling layer are fabricated on the surface of the GaAs transition layer; a Pt spin Hall effect generating layer, deposited on the asymmetric hetero barrier structure, forming a lateral strip electrode; and a lower DBR mirror, an active layer, an oxide confinement layer, and an upper DBR mirror sequentially grown above the lateral strip electrode.

[0009] The above structure aims to propose an asymmetric spin-injected vertical cavity surface emitter. Through the multi-physics field synergistic control of the spin Hall effect, asymmetric tunneling barrier, and auxiliary electric field, it realizes the on-demand injection and dynamic manipulation of high-purity spin-polarized carriers, providing a technical foundation for the development of high-speed polarization reconfigurable lasers.

[0010] Furthermore, the asymmetric heterogeneous barrier structure consists of a laterally parallel Al2O3 insulating layer and an MgO tunneling layer, wherein the Al2O3 insulating layer is used to block electrons from passing through, and the MgO tunneling layer is used to allow electrons with specific spin directions to tunnel through.

[0011] Furthermore, the thickness of the Al2O3 insulating layer is 3~5nm; the thickness of the MgO tunneling layer is 1~2nm.

[0012] Furthermore, the thickness of the Pt spin Hall effect generating layer is 20~30nm.

[0013] Furthermore, the lower DBR mirror is composed of a p-type doped GaAs / AlGaAs multilayer stack; the active layer is composed of an InGaAs quantum well and a GaAs barrier layer; and the upper DBR mirror is composed of an n-type doped GaAs / AlGaAs multilayer stack.

[0014] Furthermore, the two ends of the transverse strip electrode extend to the electrode pad area to form a first electrode and a second electrode.

[0015] Furthermore, the asymmetric spin-injected vertical cavity surface emitter also includes a third electrode located above the upper DBR mirror, the third electrode being used to apply an auxiliary voltage.

[0016] On the other hand, the present invention also provides a method for fabricating an asymmetric spin-injected vertical cavity surface emitter (VCSEL), used to fabricate the asymmetric spin-injected VCSEL as described in any of the above-mentioned claims. The fabrication method includes the following steps: sequentially growing a GaMnAs spin enhancement layer and a GaAs transition layer on a GaAs substrate; fabricating an Al2O3 insulating layer and an MgO tunneling layer on the surface of the GaAs transition layer to form an asymmetric hetero barrier structure; depositing a Pt spin Hall effect generation layer on the asymmetric hetero barrier structure and forming a transverse strip electrode; and sequentially growing a lower DBR mirror, an active layer, an oxide confinement layer, and an upper DBR mirror above the transverse strip electrode.

[0017] Furthermore, the step of sequentially growing a GaMnAs spin enhancement layer and a GaAs transition layer on a GaAs substrate includes: sequentially epitaxially growing the GaMnAs spin enhancement layer and the GaAs transition layer on the GaAs substrate using molecular beam epitaxy or metal-organic chemical vapor deposition.

[0018] Further, the step of preparing the Al2O3 insulating layer and the MgO tunneling layer on the surface of the GaAs transition layer includes: preparing the Al2O3 insulating layer and the MgO tunneling layer on the surface of the GaAs transition layer using photolithography and thin film deposition techniques.

[0019] Compared with the prior art, the present invention discloses at least the following beneficial effects:

[0020] This invention proposes a highly efficient spin injection scheme that eliminates the need for ferromagnetic materials by introducing the quantum Hall effect and heterogeneous barrier structure of nonmagnetic materials, enabling direct electrical control of the polarization state of VCSELs. This innovation not only improves spin injection efficiency and polarization control capability but also maintains compatibility with existing VCSEL processes, providing a new technological path for the development of high-performance optoelectronic devices. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a cross-sectional view of the vertical cavity surface emitter structure of the present invention;

[0023] Figure 2 This is a top view of the vertical cavity surface emitter structure of the present invention;

[0024] In the figure: 100, GaAs substrate; 200, GaMnAs spin enhancement layer; 300, GaAs transition layer; 400, Al2O3 insulating layer; 500, MgO tunneling layer; 600, Pt spin Hall effect generating layer; 700, electrode one; 800, lower DBR mirror; 900, active layer; 1000, oxide confinement layer; 1100, upper DBR mirror; 1200, electrode three; 1300, electrode two. Detailed Implementation

[0025] 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.

[0026] In existing technologies, traditional VCSELs suffer from difficulties in stably controlling the polarization direction of the output laser due to crystal symmetry and competition between higher-order modes. Spin injection using ferromagnetic materials suffers from magnetization instability and poor process compatibility. This application addresses the problems of unstable polarization control and low spin injection efficiency in existing VCSELs by introducing the synergistic effect of a GaMnAs spin enhancement layer 200, an Al2O3 / MgO asymmetric heterostructure barrier, and a Pt spin Hall effect layer to achieve highly efficient spin-polarized electron injection. Specifically, the spin Hall effect of the Pt layer generates a spin-polarized current, which is selectively tunneled through the asymmetric heterostructure barrier. The GaMnAs layer then enhances the spin polarization, ultimately achieving spin-related radiative recombination in the active region, resulting in polarization-controllable laser output. This approach avoids the drawbacks of traditional ferromagnetic materials, improves spin injection efficiency and polarization control stability, and maintains good compatibility with existing VCSEL processes.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Reference Figure 1 and Figure 2As shown, this embodiment provides an asymmetric spin-injected vertical-cavity surface emitter (VCSEL). The laser is based on a GaAs substrate 100, and from bottom to top, it integrates a GaMnAs spin enhancement layer 200, a GaAs transition layer 300, a laterally asymmetric heterogeneous barrier structure, and a Pt spin Hall effect generation layer 600. The asymmetric heterogeneous barrier structure consists of laterally parallel Al2O3 insulating layers 400 and MgO tunneling layers 500. The Al2O3 insulating layer 400 forms a high barrier, while the MgO tunneling layer 500 achieves selective tunneling of spin-polarized electrons through its sub-nanometer thickness. The Pt spin Hall effect generation layer 600 laterally covers the heterogeneous barrier structure, with its two ends connected to electrode 700 and electrode 1300, respectively, and generates a spin Hall-polarized electron flow through lateral current driving. Below the Pt layer, the lateral boundary between the MgO tunneling layer 500 and the Al2O3 insulating layer 400 matches the current direction of the Pt layer, allowing only spin-polarized electrons from one edge to tunnel into the GaAs transition layer 300. A GaMnAs spin enhancement layer 200 is positioned between the GaAs transition layer 300 and the lower DBR mirror 800, enhancing the injected electron polarization rate through spin-related scattering. The VCSEL core structure includes a p-type doped lower DBR mirror 800, an active layer 900 with multiple quantum wells, an oxide confinement layer 1000, and an n-type doped upper DBR mirror 1100. An electrode 1200 is placed on the lower DBR surface to apply an auxiliary vertical electric field. The spin polarization direction is controlled by switching the lateral current direction between electrode 700 and electrode 1300. Combined with voltage modulation of electrode 1200, the tunneling efficiency is controlled, ultimately achieving reversible manipulation of the spin-related recombination process within the active layer 900 and dynamic modulation of the laser polarization state. The core innovation of this invention lies in the synergistic effect of the Pt spin Hall effect and the asymmetric tunneling barrier, combined with the GaMnAs spin filtering enhancement mechanism, to achieve the directional injection of high-purity spin-polarized carriers with a completely non-magnetic structure, thus breaking through the limitations of magnetic noise and process compatibility of traditional ferromagnetic injection devices.

[0029] In one specific embodiment, the fabrication steps of the aforementioned spin-injected vertical-cavity surface-emitting laser include: First, a GaMnAs spin enhancement layer 200 and a GaAs transition layer 300 are sequentially epitaxially grown on a GaAs substrate 100, with the layer thickness and doping concentration precisely controlled using molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD) techniques. Subsequently, an asymmetric heterogeneous barrier structure is fabricated on the surface of the GaAs transition layer 300 using photolithography and thin-film deposition techniques: the left-side region is defined using a first photolithographic mask, and an Al2O3 insulating layer 400 with a thickness of 3-5 nanometers is grown using atomic layer deposition (ALD) to form a high barrier; then, the right-side region is defined using a second photolithographic mask, and an MgO tunneling layer 500 with a thickness controlled at 1-2 nanometers is deposited using electron beam evaporation to reduce the tunneling barrier. After stripping the photoresist, the laterally parallel Al2O3 insulating layer 400 and MgO tunneling layer 500 are formed. Next, a Pt spin Hall effect generation layer 600 with a thickness of about 20-30 nanometers is deposited on top of the heterogeneous barrier layer, and is formed into a horizontal strip electrode by photolithography and lift-off process, extending to the electrode pad area at both ends (electrode 1 700; electrode 2 1300).

[0030] After completing the spin-injection structure, the VCSEL core functional layers are grown sequentially on the GaAs substrate 100: a lower DBR mirror 800 is fabricated using a p-type doped GaAs / AlGaAs multilayer stack; an active layer 900 containing InGaAs / GaAs multiple quantum wells is grown on it; an oxide confinement layer 1000 is formed in the AlGaAs layer through an oxidation process to limit the current aperture and optical field distribution; finally, an n-type doped upper DBR mirror 1100 is grown. To achieve electrical connection, an electrode 1200 is fabricated on the top of the device, and an ohmic contact is formed on the surface of the upper DBR mirror 1100 through sputtering and alloying processes.

[0031] During device operation, the negative terminal of the current source is connected to electrode 1300, and the positive terminal is connected to electrode 700, driving a transverse current to flow through the Pt spin Hall effect generation layer 600 to generate a polarized electron flow through the spin Hall effect. Simultaneously, an auxiliary voltage source (positive terminal connected to electrode 1200, negative terminal connected to electrode 700) is applied, forming a vertical electric field between the MgO tunneling layer 500 and the underlying structure, promoting the tunneling injection of electrons with specific spin directions. After spin filtering by the GaAs transition layer 300 and the GaMnAs spin enhancement layer 200, the spin-polarized electrons enter the active layer 900, where they undergo spin-related radiative recombination with holes injected into the p-type region. By reversing the current direction in the Pt layer, the injection direction of the spin-polarized electrons can be switched, thereby dynamically controlling the polarization state of the output laser.

[0032] It should be noted that the thicknesses of the Al2O3 insulating layer 400 and the MgO tunneling layer 500, the patterned design of the Pt spin Hall effect generation layer 600, and the number of cycles in the DBR stack in this embodiment can all be adjusted according to actual needs. For example, the MgO layer can be replaced with HfO2 to adjust the barrier height; the Pt layer can also be replaced with high spin-orbit coupling materials such as Ta / W; and the quantum well composition of the active layer 900 can be adapted to the emission requirements in the 850nm to 1550nm wavelength band. Such equivalent improvements based on process compatibility are all within the scope of protection of the claims of this invention.

[0033] To address the polarization control issues of existing VCSEL technologies, this invention proposes a vertical-cavity surface-emitting laser (VCSEL) structure utilizing the spin Hall effect and spin electron injection for polarization control. This structure generates a spin-polarized current by introducing the quantum Hall effect of a non-magnetic material and combines this with a heterogeneous barrier to achieve carrier injection in a single spin direction, thereby efficiently controlling the output polarization of the VCSEL. This design aims to significantly improve spin injection efficiency and polarization control capability while avoiding the use of traditional ferromagnetic materials, thus reducing device noise and maintaining compatibility with existing VCSEL manufacturing processes.

[0034] This invention also provides a method for fabricating an asymmetric spin-injected vertical cavity surface emitter, used to fabricate the asymmetric spin-injected vertical cavity surface emitter described in the above embodiments. The fabrication method includes the following steps:

[0035] Step S1: Forming the basic layer structure

[0036] A GaMnAs spin enhancement layer 200 and a GaAs transition layer 300 are sequentially grown on a GaAs substrate 100. The GaAs substrate 100 is a single-crystal gallium arsenide material with excellent semiconductor properties, making it an ideal substrate material for fabricating III-V group semiconductor devices. In this embodiment, the surface of the GaAs substrate 100 is chemically mechanically polished to a surface roughness of less than 0.5 nm to ensure the quality of subsequent epitaxial layers. The GaMnAs spin enhancement layer 200 is a dilute magnetic semiconductor material formed by doping GaAs with Mn elements. It possesses spin-dependent scattering characteristics, which can enhance the spin polarization of passing electrons. When spin-polarized electrons pass through the GaMnAs layer, the local magnetic moment generated by Mn ions interacts with the electron spin, resulting in electrons with different spin directions experiencing different scattering probabilities, thereby enhancing the spin polarization effect. The GaAs transition layer 300 is an undoped or lightly doped GaAs material. Its main function is to act as a buffer layer, reducing lattice mismatch and interface defects between the GaMnAs layer and the subsequent heterostructure, while maintaining the spin coherence of spin-polarized electrons and preventing spin relaxation. The growth of the base layer structure can be achieved using molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). By precisely controlling the growth parameters, such as the growth temperature (500-600℃) and growth rate (0.5-1 μm / h), high-quality GaMnAs spin-enhanced layer 200 and GaAs transition layer 300 can be obtained.

[0037] Step S2: Forming an asymmetric heterogeneous barrier structure

[0038] An Al2O3 insulating layer 400 and an MgO tunneling layer 500 are fabricated on the surface of the GaAs transition layer 300 in the base layer structure. The Al2O3 insulating layer 400 is an alumina thin film grown by atomic layer deposition (ALD) with a thickness of 3-5 nm and a wide bandgap (approximately 8.8 eV), forming a high barrier to electrons. In this embodiment, the Al2O3 insulating layer 400 covers the left side of the GaAs transition layer 300 surface, and its pattern is defined by photolithography. The MgO tunneling layer 500 is a magnesium oxide thin film deposited by electron beam evaporation with a thickness of 1-2 nm and a bandgap of approximately 7.8 eV. However, due to its extremely thin thickness, electrons can pass through through it via quantum tunneling. The MgO tunneling layer 500 covers the right side of the GaAs transition layer 300 surface, forming a laterally parallel structure with the Al2O3 insulating layer 400. The asymmetric heterogeneous barrier structure consists of a high barrier of Al2O3 and a low barrier of MgO, with the key being the difference in barrier height and interface characteristics between the two materials. The Al2O3 layer completely blocks electrons from passing through, while the MgO layer allows electrons to tunnel through in specific spin directions. By precisely controlling the thickness and interface quality of the two materials, selective transport of spin-polarized electrons can be achieved. In practice, the left-side region is first defined using a first photolithography mask, and an Al2O3 insulating layer 400 is grown using ALD. Then, the right-side region is defined using a second photolithography mask, and an MgO tunneling layer 500 is deposited using electron beam evaporation. Finally, the photoresist is removed using a lift-off process, forming a complete asymmetric hetero barrier structure.

[0039] Step S3: Forming a spin-injection structure

[0040] A platinum (Pt) spin Hall effect generation layer is deposited on a heterogeneous barrier structure to form lateral strip electrodes. The Pt spin Hall effect generation layer 600 is a thin platinum film with a thickness of 20-30 nm deposited by magnetron sputtering or electron beam evaporation. Pt has a strong spin-orbit coupling effect, and when current passes through it, spin-polarized electrons accumulate at its edges. In this embodiment, the Pt layer covers the entire surface of the heterogeneous barrier structure, and lateral strip patterns are formed by photolithography and etching processes. The lateral strip electrodes refer to the metal electrodes formed at both ends of the Pt layer, labeled as Electrode 1 700 and Electrode 2 1300, respectively. The electrode material can be a metal stack such as Ti / Au or Ti / Pt / Au, with a thickness of 100-200 nm. The electrodes are prepared by electron beam evaporation deposition and lift-off processes to form good ohmic contact with the Pt layer. The spin injection structure consists of the Pt spin Hall effect generation layer 600 and the lateral strip electrodes. When a transverse current is applied between electrode 700 and electrode 1300, the Pt layer exhibits a spin Hall effect, accumulating electrons with opposite spin directions at its two edges. Due to the presence of the underlying asymmetric hetero barrier structure, only electrons with specific spin directions can tunnel into the lower structure. In practice, a Pt thin film is first deposited by sputtering, followed by the formation of strip patterns using photolithography and ion beam etching. Electron metal is then deposited via electron beam evaporation, and finally, the electrodes are fabricated using a lift-off process. The entire process requires strict control of process parameters to ensure the crystal quality of the Pt layer and the contact characteristics of the electrodes.

[0041] Step S4: Forming the VCSEL core structure

[0042] A p-type doped lower DBR mirror 800, an InGaAs / GaAs multi-quantum-well active layer 900, an oxide confinement layer 1000, and an n-type doped upper DBR mirror 1100 are sequentially grown on a spin-injection structure. The p-type doped lower DBR mirror 800 consists of a multilayer stack of p-type doped GaAs / AlGaAs, with each layer's thickness designed according to a quarter-wavelength optical thickness, forming the bottom mirror of the laser resonator. The InGaAs / GaAs multi-quantum-well active layer 900, composed of InGaAs quantum wells and GaAs barrier layers, is located at the point of maximum standing wave field in the resonator and is used to achieve carrier recombination luminescence. The oxide confinement layer 1000 is a high-Al content AlGaAs layer, with a current-confining aperture formed by selective wet oxidation, having a thickness of 30-50 nm and an oxide aperture diameter of 3-10 μm. The oxide confinement layer 1000 not only defines the current injection region but also provides lateral optical confinement. The n-type doped upper DBR mirror 1100 is composed of an n-type doped GaAs / AlGaAs multilayer stack, with a structure similar to the lower DBR, and together they form the laser resonant cavity. The VCSEL core structure consists of the above functional layers. By precisely controlling the material and geometric parameters of each layer, efficient optical confinement and carrier injection are achieved, ultimately generating laser output. In actual implementation, the growth of each functional layer adopts MOCVD technology, and the growth of the active region and the DBR mirror requires precise control of composition, thickness, and doping concentration. The oxide confinement layer 1000 is formed through a subsequent oxidation process, and the oxidation conditions need to be strictly controlled to obtain the ideal aperture size and shape.

[0043] Step S5: Achieve spin-polarized electron injection and polarization-controlled laser output

[0044] A transverse current is driven by a transverse strip electrode, combined with an auxiliary voltage, to achieve spin-polarized electron injection and generate polarization-controlled laser output. The transverse current refers to the current flowing between electrode 1 (700) and electrode 2 (1300), and its direction determines the spin polarization direction generated by the spin Hall effect in the Pt layer. A forward current generates one spin polarization, while a reverse current generates the opposite spin polarization. The auxiliary voltage is a vertical voltage applied between electrode 3 (1200) (located on the upper DBR surface) and electrode 1 (700). Its main function is to form a vertical electric field in the MgO tunneling layer (500), promoting the tunneling injection of spin-polarized electrons while suppressing reverse injection. Polarization-controlled laser output means that the output polarization state of the laser can be actively controlled by adjusting the transverse current and the auxiliary voltage. When the injected spin polarization direction changes, the spin characteristics of carrier recombination in the active region change accordingly, resulting in a change in the polarization state of the output laser. This embodiment can achieve circularly polarized or linearly polarized output. In practice, a suitable auxiliary voltage is first applied to establish a vertical electric field, and then a transverse current is applied to drive the spin Hall effect. By monitoring the laser output characteristics, the current and voltage parameters can be optimized to obtain the best polarization control effect. The current and voltage can be adjusted through external circuitry, with a response time on the order of nanoseconds.

[0045] In practice, there is a close synergy between the various steps: the basic layer structure formed in step S1 provides the foundation for subsequent spin enhancement and electron transport; the asymmetric heterostructure barrier structure prepared in step S2 enables spin-selective transport; the spin injection structure in step S3 converts current into spin polarization; the VCSEL core structure constructed in step S4 enables laser generation; and step S5 achieves polarization modulation through electrical control. The entire process is constructed sequentially from bottom to top, with each functional layer working collaboratively to ultimately achieve polarization-controllable laser output.

[0046] The method for fabricating a vertical-cavity surface-emitting laser (VCSEL) provided in this application involves sequentially growing a GaMnAs spin enhancement layer 200 and a GaAs transition layer 300 on a GaAs substrate 100 to form a base layer structure; fabricating an Al2O3 insulating layer 400 and an MgO tunneling layer 500 on the surface of the transition layer to form an asymmetric heterogeneous barrier structure; depositing a platinum spin Hall effect generation layer on the heterogeneous barrier structure and forming a transverse strip electrode; and finally, sequentially growing a p-type doped lower DBR mirror 800, an InGaAs / GaAs multi-quantum-well active layer 900, an oxide confinement layer 1000, and an n-type doped upper DBR mirror 1100 to form the VCSEL core structure. By driving a transverse current through the transverse strip electrode, combined with an auxiliary voltage, spin-polarized electron injection is achieved, generating polarization-controllable laser output. This method utilizes the synergistic effect of the spin Hall effect and the asymmetric heterogeneous barrier to achieve efficient spin injection and polarization control, avoiding the shortcomings of traditional ferromagnetic materials, and offering advantages such as good process compatibility and stable polarization control.

[0047] The core of this invention lies in utilizing the quantum Hall effect of non-magnetic materials to generate spin-polarized current. The quantum Hall effect is a quantum phenomenon that occurs under a strong magnetic field, enabling electrons to move along specific paths in a two-dimensional plane, thereby achieving spin polarization. Through a carefully designed non-magnetic material structure, a stable spin-polarized current can be induced without an external magnetic field. This spin-polarized current is then injected into the active region of a VCSEL, enabling direct control of the laser polarization state.

[0048] To ensure efficient injection of carriers with a single spin direction into the active region of the VCSEL, this invention employs a heterogeneous barrier structure. The heterogeneous barrier effectively filters and guides spin-polarized carriers, ensuring that only carriers with a specific spin direction can enter the active region and participate in the laser emission process. This structure not only improves the efficiency of spin injection but also enhances the stability of polarization control.

[0049] Furthermore, this invention places particular emphasis on compatibility with conventional VCSEL processes. By employing non-magnetic materials and existing semiconductor manufacturing techniques, this structure can be seamlessly integrated into existing VCSEL production processes without requiring large-scale modifications to existing technologies. This not only reduces manufacturing costs but also ensures that devices can be mass-produced, meeting market demand for high-performance VCSELs.

[0050] In fields such as quantum communication, the demand for polarization-stabilized single-mode lasers is growing. The spin-injected VCSEL structure of this invention can provide stable polarization output, meeting the stringent requirements of these high-end applications for laser polarization stability and a single polarization mode. Through this innovative spin-injection mechanism, the application prospects of VCSELs in high-precision optical components, atomic sensing, and quantum communication will be significantly expanded.

[0051] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0052] 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 vertical cavity surface emitter with asymmetric spin injection, characterized in that, include: GaAs substrate (100); A GaMnAs spin-enhanced layer (200) and a GaAs transition layer (300) are grown sequentially on the GaAs substrate (100). An asymmetric heterogeneous barrier structure comprising an Al2O3 insulating layer (400) and an MgO tunneling layer (500), wherein the Al2O3 insulating layer (400) and the MgO tunneling layer (500) are prepared on the surface of the GaAs transition layer (300); A Pt spin Hall effect generating layer (600) is deposited on the asymmetric hetero barrier structure and forms a transverse strip electrode; a lower DBR mirror (800), an active layer (900), an oxide confinement layer (1000), and an upper DBR mirror (1100) are sequentially grown above the transverse strip electrode.

2. The asymmetric spin-injected vertical cavity surface emitter according to claim 1, characterized in that, The asymmetric heterogeneous barrier structure consists of a laterally parallel Al2O3 insulating layer (400) and an MgO tunneling layer (500), wherein the Al2O3 insulating layer (400) is used to block electrons from passing through, and the MgO tunneling layer (500) is used to allow electrons with a specific spin direction to tunnel through.

3. The asymmetric spin-injected vertical cavity surface emitter according to claim 1, characterized in that, The thickness of the Al2O3 insulating layer (400) is 3~5nm; the thickness of the MgO tunneling layer (500) is 1~2nm.

4. The asymmetric spin-injected vertical cavity surface emitter according to claim 1, characterized in that, The thickness of the Pt spin Hall effect generating layer (600) is 20~30nm.

5. The asymmetric spin-injected vertical cavity surface emitter according to claim 1, characterized in that, The lower DBR mirror (800) is composed of a p-type doped GaAs / AlGaAs multilayer stack; the active layer (900) is composed of an InGaAs quantum well and a GaAs barrier layer; and the upper DBR mirror (1100) is composed of an n-type doped GaAs / AlGaAs multilayer stack.

6. The asymmetric spin-injected vertical cavity surface emitter according to claim 1, characterized in that, The two ends of the transverse strip electrode extend to the electrode pad area to form the first electrode and the second electrode.

7. The asymmetric spin-injected vertical cavity surface emitter according to claim 1, characterized in that, It also includes a third electrode located above the upper DBR reflector (1100), the third electrode being used to apply an auxiliary voltage.

8. A method for fabricating an asymmetric spin-injected vertical-cavity surface emitter, used to fabricate the asymmetric spin-injected vertical-cavity surface emitter according to any one of claims 1 to 7, characterized in that, Includes the following steps: A GaMnAs spin-enhanced layer (200) and a GaAs transition layer (300) are sequentially grown on a GaAs substrate (100). An Al2O3 insulating layer (400) and an MgO tunneling layer (500) are prepared on the surface of the GaAs transition layer (300) to form an asymmetric heterogeneous barrier structure; A Pt spin Hall effect generating layer (600) is deposited on the asymmetric heterogeneous barrier structure to form a transverse strip electrode; A lower DBR mirror (800), an active layer (900), an oxide confinement layer (1000), and an upper DBR mirror (1100) are sequentially grown above the transverse strip electrode.

9. The method for fabricating an asymmetric spin-injected vertical cavity surface emitter according to claim 8, characterized in that, The step of sequentially growing a GaMnAs spin enhancement layer (200) and a GaAs transition layer (300) on a GaAs substrate (100) includes: sequentially epitaxially growing the GaMnAs spin enhancement layer (200) and the GaAs transition layer (300) on the GaAs substrate (100) using molecular beam epitaxy or metal-organic chemical vapor deposition.

10. The method for fabricating an asymmetric spin-injected vertical cavity surface emitter according to claim 8, characterized in that, The steps of preparing an Al2O3 insulating layer (400) and an MgO tunneling layer (500) on the surface of the GaAs transition layer (300) include: preparing the Al2O3 insulating layer (400) and the MgO tunneling layer (500) on the surface of the GaAs transition layer (300) by photolithography and thin film deposition technology.

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