Semiconductor laser light emitting chip for laser printer

Abstract

The application relates to the technical field of semiconductor lasers, and discloses a semiconductor laser light-emitting chip for a laser printer, which comprises an N-face electrode, the top of the N-face electrode is connected with a substrate layer, the top of the substrate layer is connected with a buffer layer, the top of the buffer layer is provided with a circular-arc ridge-type strip structure, the circular-arc ridge-type strip structure comprises an N-type limiting layer connected with the buffer layer, an insulating layer wrapped on the two sides of the sidewall of the circular-arc ridge-type strip structure and a P-face electrode, and N-type waveguide layers, N-type barrier layers, quantum well layers, P-type barrier layers, P-type waveguide layers and P-type limiting layers are sequentially arranged between the N-type limiting layer and the P-face electrode from bottom to top. The semiconductor laser light-emitting chip for the laser printer effectively inhibits the leakage of carriers at high temperatures by arranging the barrier layer with high band gap in the epitaxial layer of the semiconductor laser, the preparation method is simple, the process is a mature process at present, and the semiconductor laser light-emitting chip is easy to mass-produce.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to a semiconductor laser light-emitting chip for laser printers. Background Technology

[0002] Laser printers typically use transverse mode semiconductor lasers as their light source. Laser irradiation removes unwanted charges from the surface of the charged toner cartridge, creating a charged latent image. Due to environmental factors and assembly precision requirements, semiconductor lasers generally need a large depth of field. For semiconductor lasers, a large depth of field means a smaller difference in divergence angles between the fast and slow axes, resulting in a circular or near-circular output spot. However, due to the inherent structural limitations of semiconductor lasers, especially transverse mode lasers, the difference in divergence angles between the fast and slow axes is relatively large (typically 30° for the fast axis and 10° for the slow axis), resulting in a typical elongated elliptical spot shape. This leads to low energy efficiency and limited resolution. Furthermore, the significant waste heat generated during printer operation causes the ambient temperature of the semiconductor laser chip to reach very high levels, typically exceeding 80°C. This can lead to severe carrier leakage in the semiconductor laser chip, resulting in decreased photoelectric conversion efficiency and less clear printed text.

[0003] Chinese patent CN 103166108 A discloses a circular spot output low divergence angle side-emitting photonic crystal laser and a composite waveguide device. The method consists of a ridge waveguide structure parallel to the heterojunction direction and an asymmetric photonic crystal structure perpendicular to the heterojunction direction. The combination of the two achieves the low divergence angle and circular spot output of the laser. However, the epitaxial structure in the patent is complex, requiring the growth of dozens of epitaxial layers to form the photonic crystal. This results in a high chip cost. At the same time, due to the effect of the photonic crystal, the chip voltage is very high and the slope efficiency is very low, making it unsuitable for printer applications.

[0004] This invention is proposed to address the problems of low energy utilization, low resolution, large difference in divergence angle between fast and slow axes, and severe carrier leakage at high temperatures in laser printer chips. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a semiconductor laser light-emitting chip for laser printers. It increases the slow-axis divergence angle by fabricating an arc-shaped ridge structure whose depth completely penetrates the waveguide layer, and reduces the fast-axis divergence angle by epitaxially growing a large optical cavity structure and reducing the refractive index difference between the waveguide layer and the confinement layer. A barrier layer with a bandgap wider than the waveguide layer and narrower than the confinement layer is fabricated between the waveguide layer and the quantum well layer. These barrier layers on both sides of the quantum well further confine the charge carriers in the quantum well, reducing carrier leakage at high temperatures, thus solving the problems mentioned in the background technology.

[0006] The present invention provides the following technical solution: a semiconductor laser light-emitting chip for laser printer, comprising an N-face electrode, a substrate layer connected to the top of the N-face electrode, a buffer layer connected to the top of the substrate layer, and an arc-shaped ridge structure on the top of the buffer layer. The arc-shaped ridge structure includes an N-type confinement layer connected to the buffer layer, an insulating layer that only wraps around the two sides of the sidewall of the arc-shaped ridge structure, and a P-face electrode. From bottom to top, an N-type waveguide layer, an N-type barrier layer, a quantum well layer, a P-type barrier layer, a P-type waveguide layer, and a P-type confinement layer are sequentially arranged between the N-type confinement layer and the P-face electrode.

[0007] Preferably, the thickness of the N-type waveguide layer is 400–500 nm, and the thickness of the P-type waveguide layer is 600–700 nm.

[0008] Preferably, the bandgap difference between the waveguide layer and the confinement layer is 0.2 to 0.3 eV.

[0009] Preferably, the bandgap width of the barrier layer is greater than the bandgap width of the waveguide layer and less than the bandgap width of the confinement layer.

[0010] Preferably, the sidewalls of the arc-shaped ridge strip structure are arc-shaped, and the narrowest region of the structure is the intermediate quantum well layer. The etching depth of the arc-shaped ridge strip structure needs to completely penetrate the N-type waveguide layer.

[0011] Preferably, the width of the P-side electrode is 5–7 μm, the width of the N-type confinement layer is 5–6 μm, and the width of the quantum well layer is 2–3 μm.

[0012] Preferably, an electrode contact layer is provided between the P-type confinement layer and the P-surface electrode.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The laser printer uses a semiconductor laser light-emitting chip, which effectively suppresses the leakage of charge carriers at high temperatures by setting a barrier layer with a high bandgap in the epitaxial layer of the semiconductor laser.

[0015] 2. The semiconductor laser light-emitting chip used in this laser printer effectively reduces the fast axis divergence angle by increasing the waveguide layer thickness and reducing the bandgap difference between the waveguide layer and the confinement layer. By setting the ridge strip to an arc shape, the width of the ridge strip near the waveguide layer is minimized, thereby effectively increasing the slow axis divergence angle. The combination of these two features achieves near-circular light spot output and reduces the difference between the fast and slow axis divergence angles. Furthermore, the large upper and lower widths of this type of ridge strip effectively reduce the voltage and impedance of the device and improve the chip's energy utilization rate.

[0016] 3. This invention provides a semiconductor laser light-emitting chip for laser printers, which has a simple preparation method, uses a mature process, and is easy to mass-produce. Attached Figure Description

[0017] Figure 1 This is a cross-sectional schematic diagram of a semiconductor laser light-emitting chip for a laser printer provided by the present invention.

[0018] In the figure: 1. P-type electrode; 2. P-type confinement layer; 3. P-type waveguide layer; 4. P-type barrier layer; 5. Quantum well layer; 6. N-type barrier layer; 7. N-type waveguide layer; 8. N-type confinement layer; 9. Insulating layer; 10. Buffer layer; 11. Substrate layer; 12. N-type electrode. Detailed Implementation

[0019] 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.

[0020] Please see Figure 1 A semiconductor laser light-emitting chip for laser printers includes an N-face electrode 12. A substrate layer 11 is connected to the top of the N-face electrode 12, and a buffer layer 10 is connected to the top of the substrate layer 11. The top of the buffer layer 10 is provided with an arc-shaped ridge structure. The arc-shaped ridge structure is composed of an insulating layer 9, an N-type confinement layer 8, an N-type waveguide layer 7, an N-type barrier layer 6, a quantum well layer 5, a P-type barrier layer 4, a P-type waveguide layer 3, a P-type confinement layer 2, an electrode contact layer, and a P-face electrode 1. The sidewalls of the ridge structure are arc-shaped. The insulating layer 9 is wrapped around the sidewalls of the sidewalls of the ridge structure. The narrowest region of the structure is the middle quantum well layer 5. The upper stage width of the structure is 5-7 μm, the lower stage width is 5-6 μm, and the width of the narrowest region in the middle is 2-3 μm. The etching depth of the structure needs to completely penetrate the N-type waveguide layer 7. The arc-shaped ridge structure can increase the slow axis divergence angle.

[0021] The bottom of the N-type confinement layer 8 is connected to the top of the buffer layer 10. The width of the N-type confinement layer 8 is 5-6 μm. An N-type waveguide layer 7 is epitaxially grown on the top of the N-type confinement layer 8. An N-type barrier layer 6 is grown on the top of the N-type waveguide layer 7. A quantum well layer 5 is grown on the top of the N-type barrier layer 6. A P-type barrier layer 4 is grown on the top of the quantum well layer 5. The band gap of both the P-type barrier layer 4 and the N-type barrier layer 6 is greater than the band gap of the waveguide layer and less than the band gap of the confinement layer. The difference in band gap between the barrier layer and the waveguide layer and the difference in band gap between the barrier layer and the confinement layer are both 0.1-0.2 eV. This configuration can effectively reduce carrier leakage at high temperatures, allowing the device to operate normally at a high temperature of 85°C.

[0022] A P-type waveguide layer 3 is grown on top of the P-type barrier layer 4, a P-type confinement layer 2 is grown on top of the P-type waveguide layer 3, an electrode contact layer is connected to the top of the P-type confinement layer 2, and a P-surface electrode 1 is obtained by electron beam evaporation on the top of the electrode contact layer. The width of the P-surface electrode 1 is 5 to 7 μm.

[0023] Substrate layer 11, buffer layer 10, N-type confinement layer 8, N-type waveguide layer 7, N-type barrier layer 6, quantum well layer 5, P-type barrier layer 4, P-type waveguide layer 3, and P-type confinement layer 2 are all obtained by MOCVD epitaxial growth. Insulating layer 9 is obtained by PECVD growth. N-face electrode 12 and P-face electrode 1 are obtained by electron beam evaporation. These are all conventional processes and will not be described in detail here.

[0024] The thickness of the N-type waveguide layer 7 is 400–500 nm, the thickness of the P-type waveguide layer 3 is 600–700 nm, and the bandgap difference between the waveguide layer and the confinement layer is 0.2–0.3 eV. This chip reduces the fast axis divergence angle by increasing the thickness of the waveguide layer and reducing the gap difference between the waveguide layer and the confinement layer.

[0025] Working principle: This invention reduces the fast axis divergence angle by increasing the waveguide layer thickness and decreasing the bandgap difference between the waveguide layer and the confinement layer, and increases the slow axis divergence angle by using an arc-shaped ridge strip structure. The combination of these two methods achieves near-circular light spot output. Furthermore, by combining these two methods with the method of preparing a barrier layer with a bandgap width greater than that of the waveguide layer and smaller than that of the confinement layer on both sides of the quantum well layer 5, it is possible to enable the semiconductor laser light-emitting chip to output a near-circular light spot at high temperatures.

[0026] The structural preparation methods involved in this application are all prior art. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A semiconductor laser light-emitting chip for a laser printer, comprising an N-sided electrode (12), wherein a substrate layer (11) is connected to the top of the N-sided electrode (12), and a buffer layer (10) is connected to the top of the substrate layer (11), characterized in that: The top of the buffer layer (10) is provided with an arc-shaped ridge structure. The arc-shaped ridge structure includes an N-type confinement layer (8) connected to the buffer layer (10), an insulating layer (9) that only wraps around the two sides of the sidewall of the arc-shaped ridge structure, and a P-type electrode (1). Between the N-type confinement layer (8) and the P-type electrode (1), from bottom to top, there are an N-type waveguide layer (7), an N-type barrier layer (6), a quantum well layer (5), a P-type barrier layer (4), a P-type waveguide layer (3), and a P-type confinement layer (2). The bottom of the N-type confinement layer (8) is connected to the top of the buffer layer (10). An N-type waveguide layer (7) is epitaxially grown on the top of the N-type confinement layer (8). An N-type barrier layer (6) is grown on the top of the N-type waveguide layer (7). A quantum well layer (5) is grown on the top of the N-type barrier layer (6). A P-type barrier layer (4) is grown on the top of the quantum well layer (5). The band gap of both the P-type barrier layer (4) and the N-type barrier layer (6) is greater than the band gap of the waveguide layer and less than the band gap of the confinement layer. The thickness of the N-type waveguide layer (7) is 400~500nm, the thickness of the P-type waveguide layer (3) is 600~700nm, and the bandgap difference between the waveguide layer and the confinement layer is 0.2~0.3eV; The sidewalls of the arc-shaped ridge strip structure are arc-shaped, and the narrowest region of the structure is the middle quantum well layer (5). The etching depth of the arc-shaped ridge strip structure needs to completely penetrate the N-type waveguide layer (7).

2. The semiconductor laser light-emitting chip for a laser printer according to claim 1, characterized in that: The width of the P-side electrode (1) is 5~7 μm, the width of the N-type confinement layer (8) is 5~6 μm, and the width of the quantum well layer (5) is 2~3 μm.

3. The semiconductor laser light-emitting chip for a laser printer according to claim 1, characterized in that: An electrode contact layer is provided between the P-type confinement layer (2) and the P-surface electrode (1).

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