A method of processing a semiconductor laser

Abstract

The application discloses a method for processing a semiconductor laser, which comprises the following steps: in the preparation process of the semiconductor laser, irradiating the semiconductor laser by using a preset irradiation source to improve the modulation bandwidth of the semiconductor laser, wherein the irradiation source is a particle irradiation source. By irradiating the semiconductor laser by using the preset irradiation source in the preparation process of the semiconductor laser, the modulation bandwidth of the semiconductor laser can be improved in a simpler and lower-cost method without affecting other performances of the semiconductor laser, and the dynamic performance of the semiconductor laser can be optimized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more particularly to a method for processing semiconductor lasers. Background Technology

[0002] Semiconductor lasers are lasers that use semiconductor materials as their working medium. Their working principle is to achieve population inversion of non-equilibrium charge carriers between the energy bands (conduction band and valence band) of the semiconductor material, or between the energy bands of the semiconductor material and the impurity (acceptor or donor) energy levels, through a certain excitation method. When a large number of electrons and holes in the population inversion state recombine, stimulated emission is generated.

[0003] Modulation bandwidth, as a crucial dynamic operating parameter of semiconductor lasers, directly affects the device's data transmission capability. However, in practical applications, the high-speed modulation characteristics of semiconductor lasers are limited by their internal response characteristics and external parasitic responses. With the development of the information age, the optical communication field has placed higher demands on bandwidth capacity and data transmission rates. Therefore, there is an urgent need to improve the modulation bandwidth of semiconductor lasers to further enhance data transmission rates.

[0004] To improve the modulation bandwidth of semiconductor lasers, current research focuses on optimizing device structure and manufacturing processes to reduce parasitic capacitance or optimize photon lifetime. However, these methods still face challenges such as complex implementation processes, high manufacturing costs, and the potential for compromising other device performance characteristics. Summary of the Invention

[0005] This application provides a method for processing semiconductor lasers. By irradiating and modifying the semiconductor laser, the modulation bandwidth of the semiconductor laser can be increased in a simpler and lower-cost manner without affecting other performance characteristics, which is beneficial for optimizing the dynamic performance of the semiconductor laser.

[0006] The present invention provides the following technical solution through an embodiment of the present invention:

[0007] A method for processing a semiconductor laser includes: irradiating the semiconductor laser with a preset irradiation source during the fabrication process of the semiconductor laser to improve the modulation bandwidth of the semiconductor laser, wherein the irradiation source is a particle irradiation source.

[0008] Preferably, before performing particle irradiation treatment on the semiconductor laser using a preset irradiation source, the method further includes: adjusting the irradiation flux of the preset irradiation source according to the structure of the semiconductor laser and the particle type of the preset irradiation source.

[0009] Preferably, the step of irradiating the semiconductor laser with a preset irradiation source during the fabrication process of the semiconductor laser includes: irradiating the packaged semiconductor laser with a preset irradiation source after the semiconductor laser is packaged.

[0010] Preferably, the step of irradiating the semiconductor laser with a preset irradiation source during the fabrication process of the semiconductor laser includes: irradiating the semiconductor laser with a preset irradiation source before the semiconductor laser is packaged.

[0011] Preferably, the step of irradiating the semiconductor laser with a preset irradiation source during the fabrication process of the semiconductor laser includes: irradiating the semiconductor laser with a preset irradiation source after the quantum well has been grown and before the distributed Bragg mirror has been grown.

[0012] Preferably, the step of using a preset irradiation source to perform particle irradiation treatment on the semiconductor laser includes: uniformly covering the semiconductor laser with rays emitted by the irradiation source according to a preset irradiation direction to perform irradiation treatment on the semiconductor laser.

[0013] Preferably, the angle between the preset irradiation direction and the normal direction of the semiconductor laser is less than 90 degrees.

[0014] Preferably, the preset irradiation source is a heavy ion irradiation source.

[0015] Preferably, the semiconductor laser is a vertical-cavity surface-emitting laser, the irradiation source is tantalum ions, the irradiation energy ranges from one megaelectron volts to one billion electron volts, and the irradiation flux ranges from 0 to 1 × 10⁻⁶. 8 ions / cm 2 .

[0016] Preferably, the vertical-cavity surface-emitting laser is a gallium arsenide-based vertical-cavity surface-emitting laser with a communication wavelength of 850 nm and a small-signal modulation bandwidth of 10 GHz.

[0017] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0018] This invention provides a method for processing a semiconductor laser. During the fabrication process of the semiconductor laser, the laser is irradiated using a preset irradiation source to increase its modulation bandwidth. The irradiation source is a particle irradiation source. This irradiation process does not require optimization of the semiconductor laser structure or manufacturing process. It achieves a simpler and lower-cost method to increase the modulation bandwidth of the semiconductor laser without affecting other performance characteristics, thus facilitating the optimization of the semiconductor laser's dynamic performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of an irradiated semiconductor laser in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of an exemplary VCSEL device structure in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the irradiation treatment of VCSEL in an embodiment of the present invention;

[0023] Figure 4 This is a graph showing the modulation bandwidth of VCSELs with different radiative fluxes under small-signal modulation response testing in an embodiment of the present invention.

[0024] Figure 5 This is a graph showing the relationship between the modulation bandwidth and the square root of the bias current for VCSELs with different radiative flux in embodiments of the present invention.

[0025] The reference numerals in the attached figures are as follows:

[0026] Irradiation source 10; semiconductor laser 20; N-type ohmic contact 201; substrate 202; lower DBR (N-type) 203; quantum well 204; oxide confinement layer 205; upper DBR (P-type) 206; P-type ohmic contact 207. Detailed Implementation

[0027] The inventors of this application have conducted long-term research on the limitation of high-speed modulation characteristics in semiconductor lasers. Taking the Vertical Cavity Surface Emitting Laser (VCSEL) as an example, current approaches to addressing the limitation of high-speed modulation characteristics in VCSELs mainly focus on optimizing the VCSEL device structure. For example, using a distributed Bragg reflector (DBR) with a gradient interface to reduce photon lifetime; increasing the lower mesa diameter to improve thermal diffusion and alleviate self-heating effects, thereby improving modulation bandwidth; or optimizing the oxide aperture size based on the device injection current to achieve higher modulation bandwidth.

[0028] However, the inventors discovered through research that improving modulation bandwidth by optimizing device structural parameters requires multiple design optimizations and experimental testing analyses, making the implementation quite complex. The mesa diameter has a significant impact on the threshold current, which increases with increasing mesa diameter. At the same injection current, smaller oxide apertures in the VCSEL result in higher thermal resistance, faster temperature rise, and easier saturation of optical output power. These factors are detrimental to VCSELs.

[0029] In addition, the inventors also considered optimizing the VCSEL manufacturing process. For example, using dry etching instead of wet etching to fabricate the mesa structure can reduce parasitic capacitance, increase modulation bandwidth, and provide better high-speed modulation performance. A low-k-value benzocyclobutene (BCB) planarization technique is employed to reduce the parasitic capacitance between VCSEL electrodes, thereby decreasing the parasitic cutoff frequency of the VCSEL. Then, a shallow surface etching technique is used to reduce photon lifetime and obtain a higher modulation bandwidth. However, compared to wet etching, dry etching is more expensive. BCB is an insulating resin material; if BCB residue remains during VCSEL fabrication, it will affect the ohmic contact and degrade the device's conductivity.

[0030] In other words, current research on improving the modulation bandwidth of VCSELs mainly focuses on techniques such as optimizing the epitaxial structure, reducing device parasitic capacitance, or optimizing photon lifetime. Therefore, this application provides a method for processing semiconductor lasers. By irradiating and modifying the semiconductor laser, the modulation bandwidth of the semiconductor laser can be improved in a simpler and lower-cost manner without affecting other performance characteristics, further optimizing the dynamic performance of the semiconductor laser.

[0031] The overall concept of the technical solution in this application is as follows: By irradiating the semiconductor laser with a preset irradiation source during the fabrication process of the semiconductor laser, the modulation bandwidth of the semiconductor laser is improved, wherein the irradiation source is a particle irradiation source.

[0032] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments in this specification primarily use a VCSEL laser as an example for illustration; the method for processing semiconductor lasers provided in this application can also be applied to other types of semiconductor lasers.

[0033] This invention provides a method for processing a semiconductor laser. Specifically, as shown in the embodiments of the present invention... Figure 1 As shown, the processing method includes irradiating the semiconductor laser 20 with a preset irradiation source 10 during the fabrication process of the semiconductor laser to improve the modulation bandwidth of the semiconductor laser.

[0034] In this embodiment, the irradiation source 10 is a particle irradiation source. The particle type of the preset irradiation source 10 can be heavy ions or protons and electrons with sufficient energy. For example, the particle type of the preset irradiation source 10 can be tantalum (Ta) ions.

[0035] In practical applications, the irradiation dose can be adjusted appropriately according to the specific structure of the semiconductor laser 20 and the particle type of the irradiation source 10, so as to ensure that the dynamic characteristics are improved while having minimal impact on other static characteristics of the semiconductor laser 20.

[0036] Therefore, in one optional embodiment, before irradiating the semiconductor laser 20 with the preset irradiation source 10, the process may further include: adjusting the irradiation flux of the preset irradiation source 10 according to the structure of the semiconductor laser 20 and the particle type of the preset irradiation source 10. Taking an oxide-limited VCSEL laser as an example, the irradiation flux can be appropriately adjusted according to the specific VCSEL structure and the particle type of the irradiation source 10, and then, during the VCSEL fabrication process, tantalum ions with the adjusted irradiation flux are used to irradiate the VCSEL.

[0037] Understandably, the structure of a VCSEL laser mainly consists of an upper DBR, a lower DBR, and a quantum well. The main principle is that population inversion is achieved in the excited material within the quantum well through electrical injection, and the resonant cavity composed of the upper DBR, lower DBR, and active region oscillates and selects modes, ultimately emitting laser light. For example, the fabrication process of a VCSEL may include: growing a lower DBR and a quantum well on a gallium arsenide (GaAs) substrate; after the lower DBR and quantum well are grown, the upper DBR is grown, and so on until the upper DBR is fully grown. Further steps include: evaporating Ti / Pt / Au contact rings on a highly p-doped GaAs contact layer as standard P electrodes; dry etching circular mesa surfaces using inductively coupled plasma (ICP); wet oxidation of the chip in an oxidation furnace to prepare the required oxide hole size and shape; rotating the BCB onto the sample for planarization; evaporating Ti / Au interconnects and bonding pads on the BCB; evaporating AuGe / Ni / Au-n contacts on the back of the device to prepare N electrodes, followed by rapid thermal annealing in an N2 environment; a series of processes on the epitaxial wafer until a semiconductor laser chip with a complete structure is fabricated; the packaging stage; and post-packaging stages, etc. Packaging can refer to ensuring the semiconductor laser has a coplanar "ground-signal-ground" (GSG) high-speed electrode structure, enabling electrical signal output and protecting the die for normal operation.

[0038] The proposed method of using an irradiation source 10 to irradiate the semiconductor laser 20 can be flexibly applied to different stages of the semiconductor laser 20 fabrication process. Irradiation can be performed at any stage, such as after semiconductor laser packaging is completed, after device growth is completed (but before device packaging), or after quantum well growth but before DBR growth. No specific stage is limited here.

[0039] Taking VCSEL as an example, in one optional implementation, the prepared VCSEL chip can first undergo the above-mentioned irradiation modification treatment, and then the irradiated VCSEL chip can be packaged into a GSG microstrip for easy subsequent dynamic testing. Alternatively, the above-mentioned irradiation modification treatment can be performed after the VCSEL chip is packaged into a GSG microstrip. The goal is to achieve the desired effect of generating photon absorption centers in the DBR and / or non-radiative recombination centers in the quantum well, thereby improving the modulation bandwidth of the semiconductor laser.

[0040] The inventors of this application tested a VCSEL irradiated by irradiation source 10. Under appropriate radiation flux, the modulation bandwidth of the VCSEL was improved. This demonstrates that appropriate irradiation treatment can improve the dynamic performance of semiconductor lasers. The underlying principle is as follows: Firstly, radiation reduces the reflectivity of the DBR, generating photon absorption centers in the DBR, shortening the photon lifetime, and thus reducing the damping rate, resulting in a flatter modulation response. Secondly, radiation-induced defects act as nonradiative recombination centers in the quantum well, shortening the nonradiative recombination lifetime and reducing the carrier lifetime, ultimately increasing the modulation bandwidth of the semiconductor laser and further improving its dynamic performance.

[0041] Specifically, carrier lifetime refers to the time during which electrons are continuously excited from the valence band to the conduction band, generating electron-hole pairs, under thermal equilibrium conditions, and simultaneously disappearing due to recombination. At equilibrium, the generation rate of electrons and holes equals the recombination rate, thus maintaining a constant carrier density in the semiconductor. The recombination between carriers causes them to gradually disappear; the average duration of this carrier lifetime is called carrier lifetime.

[0042] Furthermore, to achieve better irradiation effects and further improve the modulation bandwidth of the semiconductor laser 20, the aforementioned irradiation treatment of the semiconductor laser 20 using a preset irradiation source 10 may include: uniformly covering the semiconductor laser with a particle beam emitted from the irradiation source according to a preset irradiation direction, thereby irradiating the semiconductor laser. The angle between the preset irradiation direction and the normal direction of the semiconductor laser 20 is less than 90 degrees. In specific implementation, the particle beam can be incident from the top, obliquely, or bottom of the semiconductor laser 20, etc., without limitation, thus allowing for flexible placement of the irradiation equipment providing the irradiation source 10. Figure 1 Taking the incident light from the top of the semiconductor laser 20 as an example.

[0043] In the specific implementation process, taking the irradiation treatment of the packaged VCSEL with Ta ions after the VCSEL chip is packaged as an example. Figure 2 A schematic diagram of an exemplary VCSEL device structure is shown, such as... Figure 2 As shown, the working process of this VCSEL includes: electrical injection into the VCSEL through the P-type ohmic contact 207, limiting the injection current and optical field through the oxide confinement layer 205, achieving population inversion of the excited material in the quantum well 204, and oscillating mode selection through the resonant cavity composed of the upper DBR (P-type) 206, the quantum well 204 and the lower DBR (N-type) 203, and finally emitting laser light in a direction perpendicular to the VCSEL substrate.

[0044] like Figure 3 As shown, for Figure 2The VCSEL shown in the figure uses a particle beam emitted from a Ta ion irradiation source 10 to irradiate the VCSEL. The Ta ions can be incident vertically on the top of the VCSEL structure, so that the particle beam uniformly covers the entire VCSEL device.

[0045] Specifically, to more intuitively demonstrate the impact of irradiation treatment on the modulation bandwidth of semiconductor lasers, the following tests were conducted on the VCSEL irradiated with Ta ions provided in this embodiment. Specifically, a GaAs-based VCSEL with an 850nm communication wavelength and a small-signal modulation bandwidth of 10GHz was used, and Ta ions with an irradiation energy of 1907MeV (megaelectron volts) were provided. The irradiation flux range was set from 0 to 1×10⁻⁶. 8 ions / cm 2 Irradiation dose of 0.5 × 10⁻⁶ 7 and 1×10 8 ions / cm 2 The VCSEL was irradiated with three different radiant fluences, and the small-signal modulation response test results of the VCSEL under the three different radiant fluences were obtained.

[0046] like Figure 4 The figure shows the relationship between the modulation response and frequency of the VCSEL. This experiment shows that without Ta ion irradiation treatment ( Figure 4 The original line has a maximum modulation bandwidth of 13.030 GHz and an irradiance of 5 × 10⁻⁶ GHz. 7 ions / cm 2 After Ta ion irradiation treatment, the maximum modulation bandwidth is 13.430 GHz, and the irradiation fluence is 1×10⁻⁶. 8 ions / cm 2 After Ta ion irradiation treatment, the maximum modulation bandwidth was 13.929 GHz. The results indicate that within the range of 0–1 × 10⁻⁶ GHz... 8 ions / cm 2 Between the two phases, the maximum modulation bandwidth (f) of the VCSEL 3dBm The value will increase with increasing radiation flux. Specifically, after 1×10⁻⁶... 8 ions / cm 2 The maximum modulation bandwidth of the VCSEL treated with Ta ions was increased by about 7% compared to the untreated VCSEL.

[0047] Specifically, to quantitatively describe the impact of irradiation on the dynamic performance of semiconductor lasers, the effect was derived from the variation of the modulation-current efficiency factor (MCEF). The MCEF factor is defined as the efficiency of VCSEL modulation bandwidth as a function of current, and is an important parameter for quantitatively describing dynamic performance. The slope of the relationship between the VCSEL modulation bandwidth and the square root of the bias current is extracted, and this slope is the MCEF factor. VCSELs were irradiated with three different radiant fluences, and the relationship between the modulation bandwidth and the square root of the bias current under these three different radiant fluences was obtained.

[0048] like Figure 5 As shown, this represents the modulation bandwidth (f) of the VCSEL. 3dB ) and the square root of the bias current (II) th ) 1 / 2 The experiment showed that, without Ta ion irradiation treatment ( Figure 5 The original line (MCEF factor is 2.246), with an irradiation dose of 5 × 10⁻⁶. 7 ions / cm 2 After Ta ion irradiation, the MCEF factor was 2.513, and the irradiation dose was 1×10⁻⁶. 8 ions / cm 2 After Ta ion irradiation treatment, the MCEF factor was 2.797. The results indicate that within the range of 0–1 × 10⁻⁶, the MCEF factor is [missing value]. 8 ions / cm 2 Between fluences, the MCEF factor increases with increasing radiation fluence. The irradiated fluence is 1×10⁻⁶. 8 ions / cm 2 The MCEF factor of VCSELs treated with Ta ions increased by about 25% compared with untreated VCSELs, indicating that appropriate irradiation treatment of VCSELs is beneficial and improves the dynamic performance of VCSELs.

[0049] The table below shows a comparison of the maximum modulation bandwidth and MCEF factor of VCSELs exposed to different irradiation doses.

[0050]

[0051] It should be noted that, in addition to Ta ions, other heavy ion types can also be used as irradiation sources. As long as the static characteristics are not affected, the appropriate type of irradiated particle, energy and irradiation flux range can be selected.

[0052] This embodiment provides a method for processing semiconductor lasers, employing irradiation modification technology to treat semiconductor lasers (e.g., VCSELs). The irradiation source can be selected from various high-energy particles, and the irradiation direction can be any direction less than 90 degrees. The irradiation modification technology can be applied to multiple stages in the device fabrication process. For example, as described above, VCSELs can be irradiated with Ta ions. The energy, irradiation flux range, and incident direction of the Ta ions can be appropriately adjusted according to the VCSEL. After irradiation treatment with the aforementioned irradiation source, the modulation bandwidth of the VCSEL is improved under an appropriate irradiation flux.

[0053] In summary, the method for processing semiconductor lasers provided by this invention employs irradiation modification technology to irradiate the semiconductor laser, shortening the photon lifetime of the DBR and the carrier lifetime of the quantum well, increasing the modulation bandwidth and MCEF factor, thereby improving the dynamic performance of the semiconductor laser. Compared to optimizing the device structure, it improves the dynamic performance of the device without optimizing the design parameters of the device structure itself. Compared to optimizing the device manufacturing process, it is lower in cost, simpler in operation, and easier to implement. Furthermore, irradiation modification technology can be flexibly applied to multiple stages in the device fabrication process.

[0054] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0055] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for processing a semiconductor laser, characterized in that, include: In the fabrication process of a semiconductor laser, the semiconductor laser is irradiated using a preset irradiation source to improve its modulation bandwidth. The semiconductor laser is a vertical-cavity surface-emitting laser (VCSEL), the irradiation source is tantalum ions, the irradiation energy ranges from one megaelectron volts to one billion electron volts, and the irradiation flux ranges from 0 to 1 × 10⁻⁶. 8 ions / cm 2 .

2. The method as described in claim 1, characterized in that, Before subjecting the semiconductor laser to particle irradiation treatment using a preset irradiation source, the process further includes: The irradiance of the preset irradiation source is adjusted according to the structure of the semiconductor laser and the particle type of the preset irradiation source.

3. The method as described in claim 1, characterized in that, The process of fabricating a semiconductor laser, which involves irradiating the semiconductor laser using a preset irradiation source, includes: After the semiconductor laser is packaged, the packaged semiconductor laser is irradiated using a preset irradiation source.

4. The method as described in claim 1, characterized in that, The process of fabricating a semiconductor laser, which involves irradiating the semiconductor laser using a preset irradiation source, includes: Before the semiconductor laser is packaged, it is irradiated using a preset irradiation source.

5. The method as described in claim 1, characterized in that, The process of fabricating a semiconductor laser, which involves irradiating the semiconductor laser using a preset irradiation source, includes: After the quantum well is grown, but before the distributed Bragg mirror is grown, the semiconductor laser is irradiated using a preset irradiation source.

6. The method as described in claim 1, characterized in that, The process of irradiating a semiconductor laser with a preset irradiation source includes: The particle beam emitted by the irradiation source uniformly covers the semiconductor laser in a preset irradiation direction, thereby irradiating the semiconductor laser.

7. The method as described in claim 6, characterized in that, The angle between the preset irradiation direction and the normal direction of the semiconductor laser is less than 90 degrees.

8. The method as described in claim 1, characterized in that, The vertical-cavity surface-emitting laser is a gallium arsenide-based vertical-cavity surface-emitting laser with a communication wavelength of 850 nm and a small-signal modulation bandwidth of 10 GHz.

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