A state density coupled semiconductor laser

Abstract

The present invention relates to the field of semiconductor technology, and in particular to a state density coupled semiconductor laser, which is different in that it includes a substrate, and a buffer layer, a lower waveguide layer, a multi-period quantum well layer, a multi-period quantum dot layer, an upper waveguide layer, a cladding layer and a contact layer grown sequentially on the substrate. The present invention can realize a semiconductor laser with a low threshold, easy wavelength control and high temperature stability.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a state density coupling semiconductor laser. Background Art

[0002] Since the breakthrough in the preparation technology of semiconductor quantum dot materials in the 1990s, semiconductor quantum dot lasers have attracted great attention from scientists due to their many advantages. Quantum dots have the ability to restrict carrier motion in three dimensions, while quantum wells can only restrict carrier motion in one dimension. Therefore, quantum dot lasers have better temperature stability, higher differential gain, smaller frequency chirp effect and other superior performances than quantum well lasers. However, at present, semiconductor quantum dot materials are mainly prepared by self-organized growth, and there is a certain size distribution, which will cause the state density distribution of semiconductor quantum dots to be relatively wide. For example, the half-width of the ground state state density distribution of InP-based InAs quantum dot materials can reach 100 millielectron volts or even higher. The wide distribution of state density will have two effects on InP-based InAs quantum dot lasers. First, the peak gain of the laser will decrease, and second, the laser lasing wavelength is difficult to control. Technicians urgently need to overcome the adverse effects of the wide distribution of state density of InP-based InAs quantum dot materials on laser performance and improve the performance of InP-based InAs quantum dot lasers.

[0003] Compared with InAs quantum dots, although InGaAsP quantum wells have disadvantages in carrier confinement capability and differential gain, they also have the following advantages: first, the state density distribution is concentrated; second, the material gain is high; third, the lasing wavelength can be adjusted by precisely controlling technical means such as increasing or decreasing the thickness of the quantum well and the stress on the quantum well.

[0004] In view of this, in order to overcome the above technical defects, providing a state density coupled semiconductor laser has become an urgent problem to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a state density coupled semiconductor laser, which can realize a semiconductor laser with low threshold, easy wavelength control and high temperature stability.

[0006] To solve the above technical problems, the technical solution of the present invention is: a state density coupled semiconductor laser, which is different in that it includes a substrate, and a buffer layer, a lower waveguide layer, a multi-period quantum well layer, a multi-period quantum dot layer, an upper waveguide layer, a cladding layer and a contact layer grown in sequence on the substrate.

[0007] According to the above technical solution, each period of the multi-period quantum well layer includes a quantum well layer and a quantum barrier layer grown on the quantum well layer.

[0008] According to the above technical solution, the number of periods of the multi-period quantum well layer is 1-5.

[0009] According to the above technical solution, each period of the multi-period quantum dot layer includes a quantum dot layer and a capping layer grown on the quantum dot layer.

[0010] According to the above technical solution, the number of periods of the multi-period quantum dot layer is 1-10.

[0011] According to the above technical solution, there is an overlapping portion between the state density distribution of the quantum well ground state energy level in the multi-period quantum well layer and the state density distribution of the quantum dot ground state energy level in the multi-period quantum dot layer.

[0012] According to the above technical solution, the energy of the photons emitted by the multi-period quantum well layer is within the distribution range of the ground state energy level state density of the multi-period quantum dot layer.

[0013] According to the above technical solution, there is no carrier tunneling between the multi-period quantum well layer and the multi-period quantum dot layer.

[0014] According to the above technical solution, there is no position alternation between the periods of the multi-period quantum well layer and the multi-period quantum dot layer.

[0015] According to the above technical solution, the distance between the multi-period quantum well layer and the multi-period quantum dot layer is not less than 10 nanometers.

[0016] From the above scheme, the present invention discloses a state density coupled semiconductor laser, the laser active region structure includes quantum well material and quantum dot material at the same time, combining the advantages of high gain of quantum well material, concentrated state density distribution, easy control of lasing wavelength and strong carrier confinement ability of quantum dot material. On the one hand, this structure can adjust the lasing wavelength of the quantum well material part to promote the quantum dot energy level state at this wavelength to achieve stimulated radiation amplification, thereby achieving the effect of adjusting the lasing wavelength of the quantum dot material part; on the other hand, it can utilize the state density coupling of the quantum well and quantum dot material at the lasing wavelength, so that the gain of the laser comes from both the quantum dot material and the quantum well material, so that the gain of the entire laser active region is enhanced by the high gain of the quantum well material. This state density coupled semiconductor laser active region structure can realize a semiconductor laser with low threshold, easy wavelength control and high temperature stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the coupling of state density between quantum dot material and quantum well material in an embodiment of the present invention;

[0019] Among them: 1-substrate; 2-buffer layer; 3-lower waveguide layer; 4-multi-period quantum well layer (41-quantum well layer, 42-quantum barrier layer); 5-multi-period quantum dot layer (51-quantum dot layer, 52-cap layer); 6-upper waveguide layer; 7-cladding layer; 8-contact layer. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] Hereinafter, many aspects of the present invention will be better understood with reference to the accompanying drawings. The components in the accompanying drawings are not necessarily drawn to scale. Instead, emphasis is placed on clearly illustrating the components of the present invention. In addition, in several views of the accompanying drawings, the same reference numerals indicate corresponding parts.

[0022] As used herein, the words "exemplary" or "illustrative" mean used 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 of the implementations described below are exemplary implementations, which are provided to enable those skilled in the art to make and use embodiments of the present disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. In other implementations, well-known features and methods are described in detail so as not to obscure the present invention. For the purposes of the description herein, the terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," and their derivatives will be used interchangeably. Figure 1 The invention is directed to the invention of the present invention. Moreover, there is no intention to be bound by any express or implied theory given in the preceding technical field, background technology, summary of the invention or the detailed description below. It should also be understood that the specific devices and processes shown in the drawings and described in the following description are simple exemplary embodiments of the inventive concepts defined in the appended claims. Therefore, specific dimensions and other physical characteristics related to the embodiments disclosed herein should not be understood as limiting unless the claims explicitly state otherwise.

[0023] Please refer to Figure 1 and Figure 2 The present invention is a state density coupled semiconductor laser, which is different in that it includes an InP substrate 1, and an InP buffer layer 2, an InGaAsP lower waveguide layer 3, a multi-period quantum well layer 4, a multi-period quantum dot layer 5, an InGaAsP upper waveguide layer 6, an InP cladding layer 7 and an InGaAs contact layer 8 grown in sequence on the InP substrate 1.

[0024] Specifically, each period of the multi-period quantum well layer 4 includes an InGaAsP quantum well layer 41 and an InGaAsP quantum barrier layer 42 grown on the InGaAsP quantum well layer 41 .

[0025] Preferably, the period number of the multi-period quantum well layer 4 is 1-5.

[0026] Specifically, each period of the multi-period quantum dot layer 5 includes an InAs quantum dot layer 51 and an InGaAsP cap layer 52 grown on the InAs quantum dot layer 51 .

[0027] Preferably, the period number of the multi-period quantum dot layer 5 is 1-10.

[0028] Specifically, there is an overlapping portion between the state density distribution of the quantum well ground state energy level in the multi-period quantum well layer 4 and the state density distribution of the quantum dot ground state energy level in the multi-period quantum dot layer 5 .

[0029] Specifically, the energy of the photons emitted by the multi-period quantum well layer 4 is within the distribution range of the ground state energy level state density of the multi-period quantum dot layer 5 .

[0030] Specifically, there is no carrier tunneling between the multi-period quantum well layer 4 and the multi-period quantum dot layer 5 .

[0031] Specifically, there is no position alternation between the periods of the multi-period quantum well layer 4 and the multi-period quantum dot layer 5 .

[0032] Preferably, the distance between the multi-period quantum well layer 4 and the multi-period quantum dot layer 5 is not less than 10 nanometers.

[0033] The method for preparing the state density coupled semiconductor laser according to the embodiment of the present invention is as follows:

[0034] The laser structure is epitaxially grown on an N-type InP substrate 1 by using a metal organic chemical vapor deposition (MOCVD) method.

[0035] First, an N-type InP buffer layer 2 is grown, and the thickness of the buffer layer 2 is 100-500 nanometers.

[0036] An InGaAsP lower waveguide layer 3 is grown, and the thickness of the InGaAsP lower waveguide layer 3 is 50-200 nanometers.

[0037] A multi-period quantum well layer 4, the multi-period quantum well layer 4 is above the InGaAsP lower waveguide layer 3; the number of periods of the multi-period quantum well layer 4 is 1-5, and each period includes: an InGaAsP quantum well layer 41, the thickness of the InGaAsP quantum well layer 41 is 1-8 nanometers; an InGaAsP quantum barrier layer 42, the thickness of the InGaAsP quantum barrier layer 42 is 5-50 nanometers.

[0038] A multi-period quantum dot layer 5, the multi-period quantum dot layer 5 is above the multi-period quantum well layer 4; the number of periods of the multi-period quantum dot layer 5 is 1-10, and each period includes: an InAs quantum dot layer 51, the deposition thickness of the InAs quantum dot layer 51 is 0.5-2 nanometers; an InGaAsP cap layer 52, the thickness of the InGaAsP cap layer 52 is 5-50 nanometers.

[0039] An InGaAsP upper waveguide layer 6 is formed on the multi-period quantum dot layer 5 and has a thickness of 50-200 nanometers.

[0040] The P-type InP cladding layer 7 and the P-type InGaAs contact layer 8 are continuously grown.

[0041] The distance between the multi-period quantum well layer 4 and the multi-period quantum dot layer 5 is not less than 10 nanometers, and there is no carrier tunneling between the multi-period quantum well layer 4 and the multi-period quantum dot layer 5 .

[0042] The multi-period quantum well layer 4 and the multi-period quantum dot layer 5 are respectively located on one side of the lower waveguide layer 3 and the upper waveguide layer 6 in the vertical growth direction and do not alternate.

[0043] The ground state energy level state density distributions of the multi-period quantum well layer 4 and the multi-period quantum dot layer 5 overlap, such as Figure 2 In this way, the state density coupling of the quantum well and quantum dot materials existing at the lasing wavelength can be utilized, so that the gain of the laser comes from both the multi-period quantum well layer 4 and the multi-period quantum dot layer 5, and the gain of the entire laser active region is enhanced by the high gain of the quantum well material.

[0044] In the embodiment of the present invention, both InGaAsP quantum well material and InAs quantum dot material are included as gain media. Compared with quantum dot material, the lasing wavelength of quantum well material is easier to control, for example, by increasing or decreasing the thickness of quantum well, the stress on quantum well and other technical means to accurately adjust the emission wavelength of quantum well material. Figure 2As shown, for the same multi-period quantum dot layer 5, different state density distributions and lasing wavelengths can be achieved by adjusting the thickness or stress of the quantum wells in the multi-period quantum well layer 4. Since the lasing wavelength of the multi-period quantum well layer 4 can drive the quantum dot energy level state at the wavelength to achieve stimulated emission amplification, the lasing wavelength of the multi-period quantum dot layer 5 can be adjusted by conveniently adjusting the lasing wavelength of the multi-period quantum well layer 4, and finally the purpose of easily regulating the lasing wavelength of the active region structure of the state density coupled semiconductor laser is achieved.

[0045] The above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A density-of-state coupled semiconductor laser, characterized in that: It includes a substrate, and a buffer layer, a lower waveguide layer, a multi-period quantum well layer, a multi-period quantum dot layer, an upper waveguide layer, a cladding layer and a contact layer grown sequentially on the substrate; There is an overlapping portion between the quantum well ground state energy level state density distribution in the multi-period quantum well layer and the quantum dot ground state energy level state density distribution in the multi-period quantum dot layer; The energy of the photons emitted by the multi-period quantum well layer is within the distribution range of the ground state energy level state density of the multi-period quantum dot layer.

2. The state density coupled semiconductor laser according to claim 1, characterized in that: Each period of the multi-period quantum well layer includes a quantum well layer and a quantum barrier layer grown on the quantum well layer.

3. The density-of-state coupled semiconductor laser according to claim 2, characterized in that: The period number of the multi-period quantum well layer is 1-5.

4. The density-of-state coupled semiconductor laser according to claim 1, characterized in that: Each period of the multi-period quantum dot layer includes a quantum dot layer and a capping layer grown on the quantum dot layer.

5. The state density coupled semiconductor laser according to claim 4, characterized in that: The period number of the multi-period quantum dot layer is 1-10.

6. The state density coupled semiconductor laser according to claim 1, characterized in that: There is no carrier tunneling between the multi-period quantum well layer and the multi-period quantum dot layer.

7. The state density coupled semiconductor laser according to claim 1, characterized in that: There is no position alternation between the periods of the multi-period quantum well layer and the multi-period quantum dot layer.

8. The state density coupled semiconductor laser according to claim 7, characterized in that: The distance between the multi-period quantum well layer and the multi-period quantum dot layer is not less than 10 nanometers.

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