GaN-based laser diode structure
By using ITO as the ohmic contact layer and Pd as the lithography mask in GaN-based laser diodes to form a ridge structure with a right angle surface, the problem of poor light field restriction effect in the prior art is solved, and good optical restriction effect and cost reduction are achieved.
Patent Information
- Application Number
- CN202510383662.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2025-06-06
AI Technical Summary
When existing low-power GaN single-mode laser diodes realize low threshold current and single-mode lasers, it is difficult to form a ridge structure close to right angles, resulting in poor light field limiting effect, high cost or large optical loss.
ITO is used as the ohmic contact layer and Pd is used as the lithography mask. The ITO side etching angle is larger, and combined with the Pd mask, a right-angle surface ridge structure is formed to achieve good ohmic contact and optical restriction effects.
A good ohmic contact and a ridge structure close to the vertical angle is achieved, achieving a good optical limiting effect while reducing costs and optical loss.
Smart Images
Figure CN120109642A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of semiconductor lasers, and in particular to a GaN-based laser diode structure. Background Art
[0002] Low-power edge-emitting laser diodes, when operated at low currents, must achieve a lower threshold current and form a single-mode laser. Conventional low-power GaN single-mode laser diodes must have a ridge width of less than 2um and a ridge height of nearly 1um. In order to form a good light field confinement effect, the ridge angle is required to be close to a right angle.
[0003] Using ITO as contact and photoresist as mask, the angle of ridge formation is large, which is easy to cause mode leakage and large light loss; using Pd as ohmic contact metal and forming a photolithography mask can form a better angle, but the cost is high and the light limitation is affected. The present invention proposes a GaN-based laser diode structure, using ITO as an ohmic contact layer and Pd as a photolithography mask; using ITO with a larger side etching angle and combining it with a Pd mask to form a right-angle surface; it can form a good ohmic contact and a ridge structure close to a vertical angle, achieving a better optical limitation effect. Summary of the invention
[0004] Based on the technical problems existing in the background technology, the present invention proposes a GaN-based laser diode structure, using ITO as the ohmic contact layer and Pd as the photolithography mask; utilizing the larger side etching angle of ITO and combining it with the Pd mask to form a right-angle surface; it can form a good ohmic contact and a ridge structure close to a vertical angle, achieving a better optical confinement effect.
[0005] A GaN-based laser diode structure proposed in the present invention comprises a GaN substrate, an epitaxial layer is grown on the substrate, the epitaxial layer comprises a lower covering layer, a lower waveguide layer, a quantum well, an upper waveguide layer, an electron blocking layer, an upper covering layer and an epitaxial contact layer which are sequentially arranged from bottom to top; an ohmic contact layer is arranged on the epitaxial layer, a metal covering layer is plated on the ohmic contact layer, a ridge structure with a nearly vertical angle is made along the metal covering layer, the ohmic contact layer, the epitaxial contact layer and the upper covering layer, the ridge structure is covered with an insulating layer and an electron blocking layer, a P electrode is covered on the outer side of the insulating layer, the substrate is thinned, and an N electrode is made to form a laser diode structure.
[0006] Preferably, the lower cover layer is made of N-type AlGaN, the lower waveguide layer is made of N-type InGaN, the quantum well is made of InGaN, the upper waveguide layer is made of P-type InGaN, the electron blocking layer is made of P-type AlGaN, the upper cover layer is made of P-type AlGaN, the epitaxial contact layer is made of P-type GaN, and the insulating layer is made of SiO 2 Insulation layer.
[0007] Preferably, an ITO layer is plated on the epitaxial layer and annealed to form an ohmic contact layer; and the metal covering layer is a metal structure mainly composed of Pd.
[0008] Preferably, ITO is used as the ohmic contact layer and is matched with Pd as the photolithography mask; the boundary of ITO is smaller than that of Pd, and the ITO side etching angle is larger, combined with the Pd mask, to form a right-angle ridge structure.
[0009] Preferably, the refractive index of ITO is 1.8, which is lower than the refractive index of GaN.
[0010] The beneficial effects of the present invention are as follows: ITO is used as an ohmic contact layer and is matched with Pd as a photolithography mask; the refractive index of ITO is relatively low, at 1.8, which is much lower than the refractive index of GaN of 2.4, and the absorption rate is very low in the blue-green light band, which can reduce the thickness of the epitaxial layer and achieve a better optical confinement effect; the ITO side etching angle is larger, combined with the Pd mask to form a right-angle surface; a good ohmic contact and a ridge structure close to a vertical angle can be further formed to achieve a better optical confinement effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is a schematic diagram of the initial structure of a GaN-based laser diode structure proposed by the present invention;
[0012] Figure 2 A schematic diagram of the structure of a GaN-based laser diode after processing proposed by the present invention;
[0013] Figure 3 It is a schematic diagram of the composite structure of ITO and Pd of the present invention.
[0014] In the figure: 1. substrate, 2. lower cover layer, 3. lower waveguide layer, 4. quantum well, 5. upper waveguide layer, 6. electron blocking layer, 7. upper cover layer, 8. epitaxial contact layer, 9. ohmic contact layer, 10. metal cover layer, 11. ridge structure, 12. insulating layer, 13. P electrode, 14. N electrode. DETAILED DESCRIPTION
[0015] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0016] Reference Figure 1-2A GaN-based laser diode structure comprises a GaN substrate 1, an epitaxial layer is grown on the substrate 1, the epitaxial layer comprises a lower covering layer 2, a lower waveguide layer 3, a quantum well 4, an upper waveguide layer 5, an electron blocking layer 6, an upper covering layer 7 and an epitaxial contact layer 8 arranged in sequence from bottom to top; an ohmic contact layer 9 is arranged on the epitaxial layer, a metal covering layer 10 is plated on the ohmic contact layer 9, a ridge structure 11 with a nearly vertical angle is made along the metal covering layer 10, the ohmic contact layer 9, the epitaxial contact layer 8 and the upper covering layer 7, an insulating layer 12 is covered on the ridge structure 11, and the electron blocking layer 6 is covered, a P electrode 13 is covered on the outer side of the insulating layer 12, the substrate 1 is thinned, and an N electrode 14 is made to form a laser diode structure. The lower cover layer 2 is made of N-type AlGaN, the lower waveguide layer 3 is made of N-type InGaN, the quantum well 4 is made of InGaN, the upper waveguide layer 5 is made of P-type InGaN, the electron blocking layer 6 is made of P-type AlGaN, the upper cover layer 7 is made of P-type AlGaN, the epitaxial contact layer 8 is made of P-type GaN, and the insulating layer 12 is made of SiO 2 Insulation layer.
[0017] The present invention adopts a metal structure in which an ITO layer is plated on an epitaxial layer and annealed to form an ohmic contact layer 9; the metal covering layer 10 is mainly composed of Pd. Specifically, ITO is used as the ohmic contact layer 9, and Pd is used as a photolithography mask; the boundary of ITO is smaller than the boundary of Pd, and the side etching angle of ITO is larger, combined with the Pd mask, to form a ridge structure 11 with a right angle surface.
[0018] The present invention also proposes a method for preparing a GaN-based laser diode structure, comprising the following steps:
[0019] S1. Epitaxial growth: using a gallium nitride substrate, an epitaxial layer is grown on substrate 1, the epitaxial layer including a lower cladding layer n-type AlGaN, a lower waveguide layer n-type InGaN, a quantum well InGaN, an upper waveguide layer p-type InGaN, an electron blocking layer p-type AlGaN, an upper cladding layer p-type AlGaN and an epitaxial contact layer p-type GaN;
[0020] S2, an ITO layer is plated on the epitaxial layer, and annealed to form an ohmic contact layer; and a metal covering layer is plated, with a metal structure mainly composed of Pd;
[0021] S3, making a ridge structure, making a ridge structure 11 with a nearly vertical angle along the metal cover layer 10, the ohmic contact layer 9, the epitaxial contact layer 8, and the upper cover layer 7, specifically, using ITO as the ohmic contact layer 9, and using Pd as a photolithography mask; the boundary of ITO is smaller than the boundary of Pd, and the ITO side etching angle is larger, combined with the Pd mask, to form a ridge structure 11 with a right angle surface;
[0022] S4, covered with SiO 2 Insulation layer;
[0023] S5, making a P electrode; thinning the GaN substrate and making an N electrode;
[0024] S6. Finally, the chip is split and a resonant cavity is made on the side of the chip to form a laser diode.
[0025] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A GaN-based laser diode structure, comprising a substrate (1), characterized in that: An epitaxial layer is grown on a substrate (1), the epitaxial layer comprising a lower covering layer (2), a lower waveguide layer (3), a quantum well (4), an upper waveguide layer (5), an electron blocking layer (6), an upper covering layer (7) and an epitaxial contact layer (8) which are arranged in sequence from bottom to top; an ohmic contact layer (9) is arranged on the epitaxial layer, a metal covering layer (10) is plated on the ohmic contact layer (9), a ridge structure (11) with a nearly vertical angle is made along the metal covering layer (10), the ohmic contact layer (9), the epitaxial contact layer (8) and the upper covering layer (7), an insulating layer (12) is covered on the ridge structure (11), and the electron blocking layer (6) is covered, a P electrode (13) is covered on the outer side of the insulating layer (12), the substrate (1) is thinned, and an N electrode (14) is made to form a laser diode structure.
2. A GaN-based laser diode structure according to claim 1, characterized in that: The lower cover layer (2) is made of N-type AlGaN, the lower waveguide layer (3) is made of N-type InGaN, the quantum well (4) is made of InGaN, the upper waveguide layer (5) is made of P-type InGaN, the electron blocking layer (6) is made of P-type AlGaN, the upper cover layer (7) is made of P-type AlGaN, the epitaxial contact layer (8) is made of P-type GaN, and the insulating layer (12) is made of SiO2 insulating layer.
3. A GaN-based laser diode structure according to claim 1, characterized in that: An ITO layer is plated on the epitaxial layer and annealed to form an ohmic contact layer (9); the metal covering layer (10) is a metal structure mainly composed of Pd.
4. A GaN-based laser diode structure according to claim 3, characterized in that: ITO is used as an ohmic contact layer (9) and is matched with Pd as a photolithography mask; the boundary of ITO is smaller than the boundary of Pd, and the ITO side etching angle is larger, combined with the Pd mask, to form a right-angle ridge structure (11).
5. A GaN-based laser diode structure according to claim 4, characterized in that: The refractive index of ITO is 1.8, which is lower than that of GaN.