A method for improving the performance of ohmic contact of antimonide laser

Abstract

The application discloses a method for improving the ohmic contact performance of an antimonide laser. The application belongs to the technical field of semiconductor lasers and relates to a method for improving the ohmic contact performance of an antimonide laser. The application adopts heavy doping to directly serve as a contact layer or introduce heavy doping as a part of an electrode contact layer in an epitaxial structure of the antimonide laser, so as to reduce the contact resistance. Finally, after the growth of the laser structure is completed, a metal electrode thin film is deposited on the surface of the epitaxial wafer after the surface is treated by removing an oxide layer. The application adopts heavy doping to serve as the contact layer or grows heavy doping on a GaSb contact layer to serve as a carrier tunneling layer, so that the reliability and stability of the ohmic contact performance are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more specifically to a method for improving the ohmic contact performance of antimonyide lasers. Background Technology

[0002] Lasers in the 2–5 μm wavelength band have broad application prospects in gas detection, laser communication, lidar, medical diagnostics, infrared countermeasures, environmental monitoring, and industrial sensing. Antimony semiconductors such as GaSb, InSb, AlGaSb, InAsSb, InGaAsSb, and AlGaAsSb have lattice constants around 0.61 nm, and their band gaps are characterized by narrow direct band gaps. The band gap width can be adjusted over a wide range, and they exhibit high mobility, making them the preferred materials for realizing mid-infrared semiconductors. Compared to semiconductor lasers based on InP or GaAs materials, antimony lasers can achieve mid-infrared lasing while exhibiting low nonradiative recombination rates and high quantum efficiency. However, due to the complex physical and chemical properties of antimony materials, antimony laser device fabrication faces a series of key process challenges. For example, the ohmic contact problem in antimony lasers is one of the key technological issues affecting device performance and reliability.

[0003] When a metal and a semiconductor come into contact, electrons will flow from the side with the lower work function (higher Fermi level) to the other until the Fermi level reaches equilibrium. Consequently, the material with the lower work function (higher Fermi level) will carry a small amount of positive charge, while the material with the higher work function (lower Fermi level) will carry a small amount of negative charge, creating a built-in electric field that causes band bending at the semiconductor junction. Antimonide materials have narrow band gaps (GaSb band gap is approximately 0.7 eV) and high interface state density, resulting in a significant Fermi level pinning effect at the metal-semiconductor interface. This reduces the modulating effect of the metal's work function on the Schottky barrier height, leading to a high barrier height at the metal-semiconductor interface, making effective electron injection difficult and hindering the achievement of low-resistance ohmic contacts. Furthermore, the carrier doping concentration in antimonide materials is limited, typically not exceeding [a certain value]. The tunneling effect of charge carriers is weak, resulting in a larger contact resistance.

[0004] Existing antimonide type-I quantum well laser structures typically include: a GaSb substrate, a GaSb buffer layer, an n-type doped AlGaAsSb lower confinement layer, an undoped AlGaAsSb lower waveguide layer, an InGaAsSb / AlGaAsSb quantum well active region, an undoped AlGaAsSb upper waveguide layer, a p-type doped AlGaAsSb upper confinement layer, and a p-type heavily doped GaSb contact layer. The contact layer is used to form ohmic contacts with external electrodes to improve laser efficiency. Ohmic contacts are a crucial process in semiconductor devices, affecting device performance, reliability, and stability. In antimonide lasers, GaSb, as a contact layer, exhibits significant band bending and a high barrier height, limiting carrier injection. Furthermore, the GaSb surface is highly susceptible to oxidation, rapidly forming Sb₂O₃ and Ga₂O₃ layers in air, creating additional barrier layers that severely impact the formation and stability of the ohmic contact. Therefore, solving the ohmic contact problem in antimonide lasers and achieving a stable, low-resistance, and process-controllable ohmic contact structure is one of the key technical problems that urgently need to be solved in antimonide semiconductor lasers. Summary of the Invention

[0005] To address the problems existing in the ohmic contacts of antimonide semiconductor lasers in the prior art, this invention proposes a method to improve the ohmic contact performance of antimonide lasers. This invention employs heavy doping... The pentagonal alloy can be used directly as the electrode contact layer of an antimonide laser, or it can be introduced into the epitaxial structure of an antimonide laser by heavy doping. The pent-element alloy ultrathin layer is used as part of the electrode contact layer to reduce the contact resistance. Finally, after the laser structure is grown, the surface of the epitaxial wafer is treated with deoxidation layer and then a metal electrode film is deposited to passivate the surface of the epitaxial wafer.

[0006] The method includes:

[0007] S1. On an n-type GaSb substrate, using molecular epitaxy, an n-type doped GaSb buffer layer and an n-type doped layer are sequentially epitaxially grown. Lower confinement layer, undoped Lower waveguide layer, active region, undoped upper waveguide layer and p-type doping Upper constraint layer;

[0008] S2, in p-type doping On the upper confinement layer, p-type doped GaSb is epitaxially grown as a contact layer, and heavily p-type doped GaSb is epitaxially grown on the contact layer. , as an ultrathin carrier tunneling layer;

[0009] Or p-type doping p-type heavily doped material is epitaxially grown on the upper confinement layer. , as a contact layer;

[0010] S3. The epitaxial wafer structure processed in step S2 is subjected to oxide layer removal treatment to obtain the epitaxial wafer structure of the metal electrode to be deposited.

[0011] S4. Deposit metal electrodes on the P-side and N-side of the epitaxial wafer structure to be deposited, respectively, to complete the growth of the P-side electrode and the N-side electrode.

[0012] After the S5, P-side electrodes and N-side electrodes are grown, ohmic contacts are formed through rapid annealing processes.

[0013] Furthermore, p-type heavy doping The doping source is Be or Zn, and the doping concentration is... .

[0014] Furthermore, p-type heavy doping middle, The value range is 0.1 to 0.3. The value range is 0.22~0.3, and the component ratio of In to Ga ranges from 0.6 to 0.8. The calculation method is as follows p-type heavy doping The lattice number matches that of GaSb.

[0015] Furthermore, in step S4, the metal electrode material deposited on the P-plane is: Ti / Pt / Au;

[0016] On the N-plane, the deposited metal electrode material is: AuGe / Ni / Au.

[0017] Furthermore, the deoxidation treatment specifically involves immersing the epitaxial wafer structure treated in step S2 in a dilute hydrochloric acid solution with a concentration of HCl:H2O=1:10 for 120 seconds.

[0018] Furthermore, in step S5, the P-side electrode is rapidly annealed at a temperature of 260℃~345℃ to form an ohmic contact;

[0019] The N-side electrode is rapidly annealed at a temperature of 330℃~390℃ to form an ohmic contact.

[0020] Furthermore, in step S2, p-type heavily doped material is epitaxially grown on the contact layer. When using p-type doped GaSb as an ultrathin carrier tunneling layer, epitaxially grown p-type heavily doped... The thickness range is 30nm~100nm.

[0021] Furthermore, in step S2, during p-type doping... p-type heavily doped material is epitaxially grown on the upper confinement layer. When used as a contact layer, epitaxially grown p-type heavily doped material is used. The thickness range is 250nm~500nm.

[0022] The beneficial effects of the method described in this invention are as follows:

[0023] (1) By adopting a design that combines high doping with band engineering, the present invention achieves continuous band transition and low barrier contact at the metal-semiconductor interface, thereby effectively reducing contact resistance and passivating the surface of the epitaxial wafer, and improving the stability and reliability of ohmic contact.

[0024] (2) The invention selected The material's band structure lies between GaSb and InAs, with a small difference between the conduction and valence bands. This allows for a smooth band transition between the GaSb contact layer and the metal, reducing the interface barrier height and improving electron injection efficiency. Simultaneously, The material exhibits high doping concentration tolerance, enabling high carrier concentrations in the interface region. This enhances the quantum tunneling effect of carriers, allowing them to be injected into the interface in a near-linear manner, significantly reducing contact resistance and forming an ohmic contact with near-ideal linear current-voltage characteristics. This structure weakens the influence of the GaSb surface oxide layer on contact characteristics, reducing interface state density and Fermi level pinning effects. Through these methods, this invention achieves a low-contact-resistance, process-controllable, and stable ohmic contact structure, which is beneficial for improving the ohmic contact performance of antimonybide lasers. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the antimonide semiconductor laser described in this invention;

[0026] 1-n type GaSb substrate, 2-n type doped GaSb buffer layer, 3-n type doped Lower confinement layer, 4-undoped Lower waveguide layer, 5-active region, 6-undoped Upper waveguide layer, 7-p type doped Upper limiting layer and 8-contact layer. Detailed Implementation

[0027] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0028] Example 1

[0029] This embodiment provides a method for improving the ohmic contact performance of an antimonyide laser. The structure of the laser is as follows: Figure 1 As shown, the method includes the following steps:

[0030] S1. On an n-type GaSb substrate 1, an n-type doped GaSb buffer layer 2 and an n-type doped layer 3 are sequentially epitaxially grown using molecular epitaxy. Lower confinement layer 3, undoped Lower waveguide layer 4, active region 5, undoped Upper waveguide layer 6 and p-type doping Upper restriction layer 7;

[0031] The active region 5, from bottom to top, includes: undoped... First well layer, undoped Barrier layer and undoped Second well potential layer.

[0032] The relevant operations in step S1 will be introduced with specific examples:

[0033] S11. On an n-type GaSb substrate 1, a doping concentration of 1×10⁻⁶ is epitaxially grown using molecular beam epitaxy. 18 cm -3 The n-type doped GaSb buffer layer 2 has a thickness of 360 nm.

[0034] S12. On the n-type doped GaSb buffer layer 2, an epitaxial growth is performed with a doping concentration of 1×10⁻⁶. 18 cm -3 n-type doping Lower confinement layer 3 has a thickness of 1500 nm;

[0035] S13, In n-type doping Undoped material is epitaxially grown on the lower confinement layer 3. Lower waveguide layer 4, with a thickness of 300nm;

[0036] S14, in undoped state Undoped material is epitaxially grown on the lower waveguide layer 4. The first well layer has a thickness of 10 nm;

[0037] S15, in undoped state On the first well layer, an epitaxially grown undoped layer is formed. The barrier layer is 20 nm thick.

[0038] S16, in undoped Undoped material is epitaxially grown on the barrier layer. The second well layer has a thickness of 10 nm;

[0039] S17, in undoped state On the second well layer, an epitaxially grown undoped layer is formed. Upper waveguide layer 6, with a thickness of 300nm;

[0040] S18, in undoped state On the upper waveguide layer 6, an epitaxial growth doping concentration of 1×10⁶ is formed. 18 cm -3 p-type doping Upper confinement layer 7 has a thickness of 1500 nm;

[0041] S2, in p-type doping On the upper confinement layer 7, p-type doped GaSb is epitaxially grown as a contact layer 8, and p-type heavily doped GaSb is epitaxially grown on the contact layer 8. As an ultrathin carrier tunneling layer; p-type heavily doped The thickness range is 30nm~100nm;

[0042] The relevant operations in step S2 will be introduced with specific examples:

[0043] p-type doping On the upper confinement layer 7, the epitaxial growth doping concentration is 1×10⁻⁶. 18 cm -3 p-type doped GaSb, with a thickness of 300 nm, serves as contact layer 8, and a doping concentration of 5 × 10⁻⁶ is epitaxially grown on contact layer 8. 18 cm -3 p-type heavy doping With a thickness of 50 nm, it serves as an ultrathin carrier tunneling layer;

[0044] p-type heavily doped The composition of In, Al, Ga, As, and Sb in the pentagonal alloy is adjustable, and its lattice constant matches that of GaSb, which has a lattice constant of 6.0959 Å. It is heavily p-type doped. middle, The value range is 0.1 to 0.3. The value range is 0.22~0.3, and the component ratio of In to Ga ranges from 0.6 to 0.8. The calculation method is as follows The As to Sb ratio is used to fine-tune the bandgap, with p-type heavy doping. The doping source is Be or Zn, and it is a heavily p-type doped material. Continuous band transition, carrier doping concentration ≥ 5 × 10 18 cm -3 It has strong tunneling current and low contact resistance.

[0045] S3. The epitaxial wafer structure processed in step S2 is subjected to oxide layer removal treatment to obtain the epitaxial wafer structure of the metal electrode to be deposited.

[0046] The relevant operations of step S3 are described with a specific example: In this embodiment, the sample is soaked in dilute hydrochloric acid with a concentration of HCl:H2O=1:10 and washed in dilute hydrochloric acid for 120s to remove surface oxides.

[0047] S4. Deposit metal electrodes on the P-side and N-side of the epitaxial wafer structure to be deposited, respectively, to complete the growth of the P-side electrode and the N-side electrode.

[0048] On the P-plane, the deposited metal electrode material is: Ti / Pt / Au;

[0049] On the N-plane, the deposited metal electrode material is: AuGe / Ni / Au.

[0050] The relevant operations in step S4 will be introduced with specific examples:

[0051] On the P-side of the epitaxial wafer structure to be deposited with metal electrodes, the P-side electrode growth is completed by depositing a metal electrode material with Ti / Pt / Au = 50nm / 50nm / 300nm.

[0052] On the N-side of the epitaxial wafer structure to be deposited, the N-side electrode is grown by depositing a metal electrode material of AuGe / Ni / Au=5nm / 50nm / 300nm.

[0053] After the S5, P-side electrodes and N-side electrodes are grown, ohmic contacts are formed through rapid annealing processes.

[0054] The relevant operations in step S5 will be introduced with specific examples:

[0055] The P-side electrode is rapidly annealed at a temperature of 260℃~345℃ to form an ohmic contact;

[0056] The N-side electrode is rapidly annealed at a temperature of 330℃~390℃ to form an ohmic contact.

[0057] Example 2

[0058] This embodiment provides a method for improving the ohmic contact performance of an antimonyide laser. The structure of the laser is as follows: Figure 1 As shown, the method includes the following steps:

[0059] In this embodiment, p-type doping On the upper confinement layer 7, the epitaxial growth doping concentration is 5×10⁻⁶. 18 cm -3 p-type heavy doping A layer with a thickness of 300nm is used as contact layer 8;

[0060] Among them, p-type heavy doping The thickness range is 250nm~500nm.

[0061] The remaining steps are the same as in Example 1.

Claims

1. A method for improving the ohmic contact performance of an antimonybide laser, characterized in that, The method includes: S1. On an n-type GaSb substrate (1), an n-type doped GaSb buffer layer (2) and an n-type doped layer (3) are epitaxially grown sequentially using molecular epitaxy. Lower confinement layer (3), undoped Lower waveguide layer (4), active region (5), undoped upper waveguide layer (6) and p-type doping Upper restriction layer (7); S2, in p-type doping p-type doped GaSb is epitaxially grown on the upper confinement layer (7) as a contact layer (8), and p-type heavily doped GaSb is epitaxially grown on the contact layer (8). , as an ultrathin carrier tunneling layer; Or p-type doping On the upper confinement layer (7), a p-type heavily doped layer is epitaxially grown. , as a contact layer (8); p-type heavily doped middle, The value range is 0.1 to 0.

3. The value range is 0.22~0.3, and the component ratio of In to Ga ranges from 0.6 to 0.

8. The calculation method is as follows p-type heavy doping The lattice number matches that of GaSb; S3. The epitaxial wafer structure processed in step S2 is subjected to oxide layer removal treatment to obtain the epitaxial wafer structure of the metal electrode to be deposited. S4. Deposit metal electrodes on the P-side and N-side of the epitaxial wafer structure to be deposited, respectively, to complete the growth of the P-side electrode and the N-side electrode. After the S5, P-side electrodes and N-side electrodes are grown, ohmic contacts are formed through rapid annealing processes.

2. The method for improving the ohmic contact performance of an antimonybide laser according to claim 1, characterized in that, p-type heavily doped The doping source is Be or Zn, and the doping concentration is... .

3. The method for improving the ohmic contact performance of an antimonybide laser according to claim 2, characterized in that, In step S4, the deposited metal electrode material on the P-plane is: Ti / Pt / Au; On the N-plane, the deposited metal electrode material is: AuGe / Ni / Au.

4. The method for improving the ohmic contact performance of an antimonybide laser according to claim 3, characterized in that, The deoxidation process specifically involves soaking the epitaxial wafer structure treated in step S2 in a dilute hydrochloric acid solution with a concentration of HCl:H2O = 1:10 for 120 seconds.

5. A method for improving the ohmic contact performance of an antimonybide laser according to claim 4, characterized in that, In step S5, the P-side electrode is rapidly annealed at a temperature of 260℃~345℃ to form an ohmic contact; The N-side electrode is rapidly annealed at a temperature of 330℃~390℃ to form an ohmic contact.

6. The method for improving the ohmic contact performance of an antimonybide laser according to claim 5, characterized in that, In step S2, p-type heavily doped material is epitaxially grown on the contact layer (8). When using p-type doped GaSb as an ultrathin carrier tunneling layer, epitaxially grown p-type heavily doped... The thickness range is 30nm~100nm.

7. A method for improving the ohmic contact performance of an antimonyide laser according to claim 5, characterized in that, In step S2, during p-type doping... On the upper confinement layer (7), a p-type heavily doped layer is epitaxially grown. When used as a contact layer (8), epitaxial growth of p-type heavily doped material is performed. The thickness range is 250nm~500nm.

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