WO2022077698A1

WO2022077698A1 - Semiconductor ultrashort pulse laser and manufacturing method therefor

Info

Publication number: WO2022077698A1
Application number: PCT/CN2020/129920
Authority: WO
Inventors: 季海铭; 罗帅; 徐鹏飞; 王岩
Original assignee: 江苏华兴激光科技有限公司
Priority date: 2020-10-13
Filing date: 2020-11-19
Publication date: 2022-04-21
Also published as: CN112086856A; CN112086856B

Abstract

A semiconductor ultrashort pulse laser and a manufacturing method therefor, comprising the following steps: step 1: selecting an N-type substrate; step 2: performing epitaxial growth of a semiconductor dual-mode quantum dot material on the substrate; step 3: photoetching and etching a laser by using a standard semiconductor photoelectronic chip process to form a ridge waveguide structure, and then thinning and polishing the substrate; step 4: depositing a P-surface metal layer and an N-surface metal layer by means of magnetron sputtering or electron beam evaporation, and performing high-temperature annealing to form metal-semiconductor contact; and step 5: performing scribing cleavage and cavity surface coating on the substrate to form the semiconductor ultrashort pulse laser, thereby completing the manufacturing. The semiconductor ultrashort pulse laser based on single-region injection is realized, and the cost is effectively reduced.

Description

A kind of semiconductor ultrashort pulse laser and preparation method thereof

technical field

The invention relates to the technical field of semiconductors, in particular to a semiconductor ultra-short pulse laser and a preparation method thereof.

Background technique

Ultrashort pulses are laser pulses with a duration of only picoseconds ( ^10-12 seconds) or even femtoseconds ( ^10-15 seconds), mainly through gain-switching, Q-switching and locking. technology such as mode-locking. Since its inception in the 1960s, ultra-short pulse lasers have been attracting attention and have had a profound impact on many fields of science and technology, and have won the Nobel Prize in Chemistry in 1999 and the Nobel Prize in Physics in 2005. In just half a century, ultrashort pulse light sources have experienced the development process from dye lasers to Ti:sapphire lasers, to fiber femtosecond lasers, and semiconductor ultrashort pulse lasers. Semiconductor ultrashort pulse laser, as the latest generation of ultrashort pulse light source, although its current pulse width is hundreds of picoseconds, which is larger than that of Ti:sapphire lasers (several picoseconds) and fiber femtosecond lasers (tens of picoseconds), but With a very high repetition frequency, coupled with the advantages of low cost, low power consumption, small size, and easy integration, it has far-reaching application prospects in many fields. Since the cavity length of the semiconductor laser is short (0.1-10mm), and the repetition frequency of the ultrashort pulse is inversely proportional to the cavity length, the pulse repetition frequency of the semiconductor ultrashort pulse laser can reach tens or even hundreds of GHz, which can be applied to Time division multiplexing, all-optical conversion, clock recovery and other communication transmission fields, as well as ultra-fine micromachining, biomedical diagnosis and treatment and other fields.

With the continuous development of semiconductor optoelectronic technology, the active region of semiconductor ultrashort pulse laser has gradually transitioned from bulk material and quantum well to quantum dot material. Ultrashort pulse lasers based on quantum dot materials can further exert the advantages of semiconductor ultrashort pulse light sources, and are currently the research frontier and hotspot of semiconductor ultrashort pulse light sources. In order to improve the performance of semiconductor ultra-short pulse lasers, quantum dot materials have the following advantages: 1) Semiconductor quantum dots are usually grown in a self-organized manner, and the size, composition, and stress distribution of quantum dots can be changed by growth regulation, and the obtained Wide gain spectrum, since the gain bandwidth of the active region of the laser determines the lower limit of the ultra-short pulse width, it is expected to achieve ultra-short pulses with a pulse width of less than 100 fs; 2) The quantum dot material has ultra-fast carrier dynamics, in-band The relaxation time is in the order of ps, and the absorption recovery time can reach 700 fs under reverse bias, which is expected to achieve ultra-short pulses with a THz repetition rate; 3) Quantum dots have significant carrier filling due to the separation of three-dimensional confined energy levels The effect of differential gain with the injection current is more obvious, which is more conducive to the self-starting of passive mode locking.

The traditional semiconductor ultrashort pulse laser realizes the dual-region injection structure by etching an electrically isolated gain region and a saturable absorption region on the upper electrode part of the laser, and the two regions still share a complete resonant cavity. The gain region of the laser is injected with forward current to form radiation, while the saturable absorption region is added with reverse bias voltage to form absorption loss, and stable passive mode locking can be formed within a certain range of dual-region injection conditions. The most common means of short pulse laser output. However, the ultra-short pulse laser with dual-region injection requires two current inputs, while the traditional semiconductor laser for communication and industrial processing uses single-region injection and only needs one current input. Therefore, the fabrication process and packaging test of the dual-zone semiconductor ultra-short pulse laser are more complicated than those of traditional communication and industrial processing semiconductor lasers, and the cost is relatively high.

In view of this, in order to overcome the above-mentioned technical defects, it has become an urgent problem to be solved in the art to provide a semiconductor ultrashort pulse laser and a preparation method thereof.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the shortcomings of the prior art, and to provide a semiconductor ultra-short pulse laser and a preparation method thereof, which can realize a single-region injection semiconductor ultra-short pulse laser and effectively reduce the cost.

In order to solve the above technical problems, the technical scheme of the present invention is: a preparation method of a semiconductor ultra-short pulse laser, the difference of which is that it includes the following steps:

Step 1: Select an N-type substrate;

Step 2: epitaxial growth of semiconductor dual-mode quantum dot material on the substrate;

Step 3: use standard semiconductor optoelectronic chip technology to perform laser lithography and etching to form a ridge waveguide structure, followed by substrate thinning and polishing;

Step 4: depositing the P-side metal layer and the N-side metal layer by magnetron sputtering or electron beam evaporation, and performing high temperature annealing to form a gold semi-contact;

Step 5: dicing and cleaving the substrate and coating the cavity surface to form a semiconductor ultra-short pulse laser, and the preparation is completed.

According to the above technical solution, the step 2 includes the following sub-steps:

Step 21: First, grow the N-type cladding layer and the lower waveguide layer;

Step 22: then prepare a multi-period quantum dot layer on the lower waveguide layer;

Step 23: Continue to grow the upper waveguide layer, the P-type cladding layer and the P-type contact layer.

According to the above technical scheme, each period of the multi-period quantum dot layer includes an InAs quantum dot layer and an InGaAsP isolation layer, and the InAs/QD distribution of dual-mode distribution is formed by means of regulating the growth temperature, the quantum dot nucleation time, and the quantum dot maturing time. InGaAsP quantum dot material.

A semiconductor ultra-short pulse laser prepared according to the above technical scheme is different in that its structure includes an N-type metal electrode region, a semiconductor dual-mode quantum dot material region, and a P-type metal electrode region.

According to the above technical solution, the semiconductor dual-mode quantum dot material region includes semiconductor quantum dot materials with two state density distribution modes, the state density distribution modes are close to normal distribution, and the wavelength range of the state density distribution is 1000nm-2300nm, so The central wavelengths of the two density of states distribution modes are separated by 50nm-200nm.

According to the above technical solution, the semiconductor quantum dot materials of the two density of states distribution modes, wherein the quantum dot material of the density of state distribution mode with the short center wavelength is used as the laser gain region material, and the quantum dot material of the density of state distribution mode with the center wavelength is long. The dot material acts as a saturable absorption zone material.

According to the above technical solution, a wetting layer exists between the quantum dot material and the base material, and the wetting layer has a density of states distribution pattern similar to that of the quantum well material.

According to the above technical solution, the laser energy generated from the laser gain region is greater than the energy level difference of the energy level of the wetting layer of the quantum dot material as the saturable absorption region.

According to the above technical solution, the P-type metal electrode region is a metal material that forms a P-type gold semi-contact with GaAs or InP, and the entire electrode region is a single-polarity carrier input, that is, to the semiconductor dual-mode quantum dots The material region performs hole injection.

According to the above technical solution, the N-type metal electrode region is a metal material that forms N-type gold semi-contact with GaAs or InP, and the entire electrode region is a single-polarity carrier input, that is, to the semiconductor dual-mode quantum dots The material region undergoes electron injection.

Based on the above solution, the present invention discloses a semiconductor ultra-short pulse laser and a preparation method thereof. The laser structure includes a P-type metal electrode region, a semiconductor dual-mode quantum dot material region, and an N-type metal electrode region, wherein the semiconductor dual-mode quantum dots The material region is composed of semiconductor quantum dot material containing two distribution modes of density of states. Semiconductor quantum dots play the roles of laser gain region and saturable absorption region required for ultrashort pulse laser generation at the same time. Among them, the quantum dot material with a short center wavelength density distribution mode is used as a laser gain region material, and has a center wavelength deviation. Quantum dot materials with long DOS distribution patterns are used as saturable absorber materials. In this way, a single-region implanted semiconductor ultra-short pulse laser can be realized, which is compatible with the process fabrication and packaging testing of traditional semiconductor lasers for communication and industrial processing.

Description of drawings

1 is a schematic diagram of the overall structure of a laser according to an embodiment of the present invention;

2 is a schematic diagram of the density of states distribution of quantum dots according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the energy level distribution of quantum dots according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In the following, many aspects of the present invention will be better understood with reference to the accompanying drawings. Features in the figures are not necessarily drawn to scale. Instead, emphasis is placed on clearly illustrating the components of the invention. Furthermore, like reference numerals indicate corresponding parts throughout the several views of the drawings.

The words "exemplary" or "illustrative" as used herein mean serving as an example, instance, or illustration. Any implementation described herein as "exemplary" or "illustrative" is not necessarily to be construed as preferred or advantageous over other implementations. All embodiments described below are exemplary embodiments provided to enable those skilled in the art to make and use examples of the disclosure and are not intended to limit the scope of the disclosure, which is defined by The claims are limited. In other instances, well-known features and methods have been described in detail so as not to obscure the present invention. For the purposes of this description, the terms "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal" and derivatives thereof will be oriented as in FIG. 1 of inventions. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. It should also be appreciated that the specific apparatus and processes illustrated in the drawings and described in the following specification are simple exemplary embodiments of the inventive concepts defined in the appended claims. Therefore, specific dimensions and other physical characteristics associated with the embodiments disclosed herein are not to be construed as limiting, unless the claims expressly state otherwise.

Please refer to FIG. 1 to FIG. 3 , a method for preparing a semiconductor ultra-short pulse laser of the present invention is different in that it includes the following steps:

Step 1: Select a 2-inch N-type InP substrate;

Step 2: using a metal organic chemical vapor deposition (MOCVD) method to perform epitaxial growth of a semiconductor dual-mode quantum dot material on the substrate;

Step 4: depositing the TiPtAu metal layer on the P side and the AuGeNi metal layer on the N side by magnetron sputtering, and performing rapid annealing at 400 degrees Celsius for 60 seconds to form a gold semi-contact;

Specifically, the step 2 includes the following sub-steps:

Step 21: First, grow a 500nm N-type InP cladding layer and a 200nm InGaAsP lower waveguide layer;

Step 22: then prepare a multi-period InAs quantum dot layer on the lower waveguide layer;

Step 23: Continue to grow the 200nm InGaAsP upper waveguide layer, the 1700nm P-type InP cladding layer and the 200nm P-type InGaAs contact layer.

Preferably, each period of the multi-period quantum dot layer includes an InAs quantum dot layer with a deposition amount of 2ML (monolayer) and an InGaAsP isolation layer of 30 nm. By adjusting the growth temperature, quantum dot nucleation time, quantum dot maturation time, etc. The method forms the InAs/InGaAsP quantum dot material with bimodal distribution.

In this embodiment, the semiconductor dual-mode quantum dots use advanced epitaxy methods such as Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapour Deposition (MOCVD) to utilize the lattice loss of InAs and GaAs. The lattice mismatch between InAs and InP is prepared in the Stranski–Krastanov growth mode driven by lattice mismatch stress under the appropriate control of growth temperature or reaction kinetics such as growth pause.

Preferably, the semiconductor dual-mode quantum dot material region includes semiconductor quantum dot materials with two density of states distribution modes, the density of states distribution modes are close to normal distribution (Gaussian distribution), and the wavelength range of the density of states distribution is 1000nm-2300nm , the center wavelengths of the two density of states distribution modes have an interval of 50nm-200nm.

Specifically, the semiconductor quantum dot materials of the two state density distribution modes in the semiconductor dual-mode quantum dot material region simultaneously play the roles of the laser gain region and the saturable absorption region required for the generation of ultra-short pulse lasers, wherein the center wavelength The quantum dot material with the short DOS distribution pattern is used as the material of the laser gain region, and the quantum dot material with the DOS distribution pattern with the longer center wavelength is used as the saturable absorption region material.

Specifically, a wetting layer exists between the quantum dot material and the base material, and the wetting layer has a density of states distribution pattern similar to that of the quantum well material.

Specifically, the laser energy EgQD1 generated from the laser gain region is greater than the energy level difference EgWL2 of the energy level of the wetting layer of the quantum dot material as the saturable absorption region.

Preferably, the P-type metal electrode region is a metal material that forms a P-type gold semi-contact with GaAs or InP, and the entire electrode region is a single-polarity carrier input, that is, to the semiconductor dual-mode quantum dot material region Hole injection is performed.

In this embodiment, the P-type metal electrode is TiPtAu or TiAu alloy metal, and a metal plating layer is formed on the surface of the P-type semiconductor by magnetron sputtering or electron beam evaporation, and then a P-type gold semi-contact is formed by high temperature annealing.

Preferably, the N-type metal electrode region is a metal material that forms N-type gold semi-contact with GaAs or InP, and the entire electrode region is a single-polarity carrier input, that is, to the semiconductor dual-mode quantum dot material region Electron injection is performed.

In this embodiment, the N-type metal electrode is AuGeNi alloy metal, and a metal plating layer is formed on the surface of the N-type semiconductor by magnetron sputtering or electron beam evaporation, and then an N-type gold semi-contact is formed by high temperature annealing.

In the embodiment of the present invention, the working mode of the laser generating ultra-short pulses is: the laser photons generated from the laser gain region are absorbed by the energy level of the wetting layer as the quantum dot material in the saturable absorption region, and only in the time domain each laser mode is synchronized Only when locked, can the absorption of the energy level of the wetting layer of the quantum dot material in the saturable absorption region be overcome, thereby generating an ultrashort pulse laser output.

The above content is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deductions or substitutions can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims

A preparation method of a semiconductor ultra-short pulse laser is characterized in that, comprises the following steps:

Step 1: Select an N-type substrate;

Step 2: epitaxial growth of semiconductor dual-mode quantum dot material on the substrate;

Step 3: use standard semiconductor optoelectronic chip technology to perform laser lithography and etching to form a ridge waveguide structure, followed by substrate thinning and polishing;

Step 4: depositing the P-side metal layer and the N-side metal layer by magnetron sputtering or electron beam evaporation, and performing high temperature annealing to form a gold semi-contact;

Step 5: dicing and cleaving the substrate and coating the cavity surface to form a semiconductor ultra-short pulse laser, and the preparation is completed.
The method for preparing a semiconductor ultrashort pulse laser according to claim 1, wherein the step 2 comprises the following sub-steps:

Step 21: First, grow the N-type cladding layer and the lower waveguide layer;

Step 22: then prepare a multi-period quantum dot layer on the lower waveguide layer;

Step 23: Continue to grow the upper waveguide layer, the P-type cladding layer and the P-type contact layer.
The method for preparing a semiconductor ultra-short pulse laser according to claim 2, wherein each period of the multi-period quantum dot layer comprises an InAs quantum dot layer and an InGaAsP isolation layer, and by regulating the growth temperature, quantum dot nucleation The InAs/InGaAsP quantum dot material with bimodal distribution is formed by means of time and quantum dot aging time.
A semiconductor ultra-short pulse laser prepared according to the method of any one of claims 1 to 3, characterized in that: its structure includes an N-type metal electrode region, a semiconductor dual-mode quantum dot material region, and a P-type metal electrode region.
The semiconductor ultra-short pulse laser according to claim 4, wherein the semiconductor dual-mode quantum dot material region comprises semiconductor quantum dot materials with two state density distribution modes, and the state density distribution modes are close to normal distribution, The wavelength range of the density of states distribution is 1000nm-2300nm, and the center wavelengths of the two density of states distribution modes are separated by 50nm-200nm.
The semiconductor ultra-short pulse laser according to claim 5, wherein: the semiconductor quantum dot materials of the two density of states distribution modes, wherein the quantum dot material of the density of states distribution mode with a short center wavelength is used as the laser gain region material , and the quantum dot material with the density of state distribution mode with long central wavelength is used as the material of the saturable absorption region.
The semiconductor ultrashort pulse laser according to claim 6, wherein a wetting layer exists between the quantum dot material and the base material, and the wetting layer has a density of states distribution pattern similar to that of the quantum well material.
The semiconductor ultrashort pulse laser according to claim 7, wherein the laser energy generated from the laser gain region is greater than the energy level difference of the energy level of the quantum dot material infiltration layer as the saturable absorption region.
The semiconductor ultra-short pulse laser according to claim 4, wherein the P-type metal electrode region is a metal material that forms P-type gold semi-contact with GaAs or InP, and the entire electrode region is a single-polarity current-carrying material Sub-input, that is, performing hole injection into the semiconductor dual-mode quantum dot material region.
The semiconductor ultra-short pulse laser according to claim 4, wherein the N-type metal electrode region is a metal material that forms N-type gold semi-contact with GaAs or InP, and the entire electrode region is a single-polarity current-carrying material Sub-input, that is, performing electron injection into the semiconductor dual-mode quantum dot material region.