阅读说明：本技术 一种制备超宽发光谱的砷化铟/磷化铟量子点激光器外延片的方法 (Method for preparing ultra-wide light-emitting spectrum indium arsenide/indium phosphide quantum dot laser epitaxial wafer ) 是由 王岩 徐鹏飞 罗帅 季海铭 于 2021-08-11 设计创作，主要内容包括：一种制备超宽发光谱的砷化铟/磷化铟量子点激光器外延片的方法,为在磷化铟衬底上外延生长缓冲层和下分别限制层；再堆叠生长多层量子点有源层；再沉积上分别限制层和欧姆接触层后,完成制备。其通过控制量子点的沉积厚度来调节所生长量子点的大小,同时通过调节量子点盖层两步生长中第一盖层的厚度来调节所生长量子点的高度,以实现不同大小和高度的量子点堆叠生长,进而调节并使得所制备的砷化铟/磷化铟量子点外延片具有超宽发光谱,其步骤简单,操作方便、可控可调节,制得的外延片是制备可调谐激光器的理想材料,具有很强的实用性和广泛的适用性。(A method for preparing indium arsenide/indium phosphide quantum dot laser epitaxial wafer with ultra-wide light-emitting spectrum is to epitaxially grow a buffer layer and a lower limiting layer on an indium phosphide substrate; then, stacking and growing a plurality of quantum dot active layers; and depositing a limiting layer and an ohmic contact layer respectively to finish the preparation. The size of the grown quantum dots is adjusted by controlling the deposition thickness of the quantum dots, the height of the grown quantum dots is adjusted by adjusting the thickness of the first cover layer in the two-step growth of the quantum dot cover layer, so that the stacked growth of the quantum dots with different sizes and heights is realized, and the prepared indium arsenide/indium phosphide quantum dot epitaxial wafer is adjusted and has an ultra-wide luminescence spectrum.)

1. A method for preparing an indium arsenide/indium phosphide quantum dot laser epitaxial wafer with an ultra-wide light-emitting spectrum is characterized by comprising the following steps:

s1: epitaxially growing a buffer layer and a lower respective limiting layer on an indium phosphide substrate;

s2: stacking and growing a plurality of quantum dot active layers on the lower limiting layers respectively;

s3: and respectively depositing a limiting layer and an ohmic contact layer on the quantum dot active layer to finish the preparation.

2. The method of claim 1, wherein the number of stacked layers of the quantum dot active layer is 1 to 30.

3. The method of claim 1, wherein the quantum dot active layer comprises a quantum dot layer and a first cap layer and a second cap layer thereon;

the quantum dot layer includes an indium arsenide quantum dot layer.

4. The method as claimed in claim 3, wherein the quantum dot layer is grown at a temperature of 430-560 ℃ and deposited to a thickness of 1-5 atomic monolayers.

5. The method as claimed in claim 3, wherein the growth temperature of the first cap layer is 430-560 ℃ and the deposition thickness is 1-20 nm.

6. The method of claim 3, wherein the second capping layer has a thickness of less than 60 nm.

7. The method of claim 3, wherein the plurality of quantum dot active layers, the deposited thicknesses of the quantum dot layers being different from each other; the size of the quantum dots is adjusted through the deposition thickness, and the light-emitting wavelength of the quantum dots is further adjusted.

8. The method of claim 3, wherein the plurality of quantum dot active layers, the first cap layers, are deposited at different thicknesses from one another; the height of the finally obtained quantum dots is adjusted through the deposition thickness of the first cover layer, and the light-emitting wavelength of the quantum dots is further adjusted.

9. The method of claim 1, wherein the epitaxial growth comprises molecular beam epitaxy and metal organic chemical deposition.

Technical Field

The invention relates to a method for preparing a laser epitaxial wafer, in particular to a method for preparing an indium arsenide/indium phosphide quantum dot laser epitaxial wafer with an ultra-wide luminescence spectrum, and belongs to the technical field of semiconductors.

Background

The semiconductor quantum dot laser has the characteristics of low line width enhancement factor, high temperature stability, ultra-fast carrier dynamics and the like, and has unique advantages in the aspect of realizing broadband tunability. The method has wide application prospect in the fields of optical fiber communication, biomedical treatment, environmental monitoring and the like.

Of several quantum dot materials, indium arsenide/gallium arsenide quantum dots with a wavelength of about 1.3 μm are of most interest and many good properties are obtained due to the high growth quality of the epitaxial material. However, indium arsenide/gallium arsenide quantum dot materials are difficult to cover 1.55 μm optical communication band, and thus indium arsenide/indium phosphide quantum dot materials are a focus of attention.

The quantum dot formation by using the self-organization growth mode (SK) in the strain heterogeneous epitaxy is the most common quantum dot preparation method applied at present. And at the beginning of growth, the sum of the surface energy and the interface energy of the epitaxial layer is less than the surface energy of the substrate, and the epitaxial layer can completely soak the substrate. However, the mismatch between the epitaxial layer and the substrate material is large, and the strain energy of the system is gradually increased along with the increase of the thickness of the epitaxial layer. When a certain critical thickness is reached (typically a few atomic layers thick), the epitaxial material transforms from two dimensions to three dimensions, forming island-like growth. The SK self-organizing mode has the advantages that a quantum dot structure with few defects can be obtained through simple epitaxy, the luminescence of a single quantum dot is tested by utilizing the micro-region PL, the half width of an emission spectrum is only 0.1meV, and the emission spectrum is in a typical Lorentzian shape.

However, quantum dots grown in SK mode have intrinsic size non-uniformity in practice, resulting in non-uniform broadening of energy levels. The size distribution of quantum dots grown by an SK mode is difficult to control, and the spectrum has large non-uniform broadening (about 20-100 meV range or wider). This is not favorable for the gain of a common laser with a specific wavelength.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a method for preparing an indium arsenide/indium phosphide quantum dot laser epitaxial wafer with an ultra-wide luminescence spectrum.

In order to achieve the above object, the present invention adopts the following technical solutions:

a method for preparing an indium arsenide/indium phosphide quantum dot laser epitaxial wafer with an ultra-wide light-emitting spectrum comprises the following steps:

s1: epitaxially growing a buffer layer and a lower respective limiting layer on an indium phosphide substrate;

s2: stacking and growing a plurality of quantum dot active layers on the lower limiting layers respectively;

s3: and respectively depositing a limiting layer and an ohmic contact layer on the quantum dot active layer to finish the preparation.

The stacking layer number of the quantum dot active layer is 1-30.

The quantum dot active layer comprises a quantum dot layer, a first cover layer and a second cover layer; the quantum dot layer includes an indium arsenide quantum dot layer.

Furthermore, the growth temperature of the quantum dot layer is 430-560 ℃, and the deposition thickness is 1-5 atomic monolayers.

Furthermore, the growth temperature of the first cap layer is 430-560 ℃, and the deposition thickness is 1-20 nm.

Further, the thickness of the second cap layer is less than 60 nm.

Furthermore, the deposition thickness of the quantum dot layers of the multi-layer quantum dot active layer is different; the size of the quantum dots is adjusted through the deposition thickness, and the light-emitting wavelength of the quantum dots is further adjusted.

Furthermore, the deposition thicknesses of the first cover layers of the multiple quantum dot active layers are different; the height of the finally obtained quantum dots is adjusted through the deposition thickness of the first cover layer, and the light-emitting wavelength of the quantum dots is further adjusted.

The epitaxial growth includes molecular beam epitaxy and metal organic chemical deposition.

The invention has the advantages that:

the method for preparing the indium arsenide/indium phosphide quantum dot laser epitaxial wafer with the ultra-wide light-emitting spectrum can be used for preparing the indium arsenide/indium phosphide quantum dot laser epitaxial wafer by Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD), adjusting the size of the grown quantum dots by controlling the deposition thickness of the quantum dots, adjusting the height of the grown quantum dots by adjusting the thickness of a first cover layer in two-step growth of the quantum dot cover layer, so that the stacked growth of the quantum dots with different sizes and heights is realized, the prepared indium arsenide/indium phosphide quantum dot epitaxial wafer is adjusted and made to have the ultra-wide light-emitting spectrum, and the controllable adjustment of the light-emitting wavelength and the spectrum width of the indium arsenide/indium phosphide quantum dot light wavelength within the range from 1.3-1.7 microns to 400nm is realized.

The method for preparing the indium arsenide/indium phosphide quantum dot laser epitaxial wafer with the ultra-wide luminescent spectrum has the advantages of simple steps, convenient operation, controllability and adjustability, and the prepared indium arsenide/indium phosphide quantum dot epitaxial wafer has the ultra-wide luminescent spectrum, is an ideal material for preparing tunable lasers, and has strong practicability and wide applicability.

Drawings

Fig. 1 is a schematic structural diagram of an epitaxial wafer.

Fig. 2 is a graph comparing the photoluminescence spectra of sample 1 and sample 2.

The designations in the drawings have the following meanings: 10. the quantum dot light-emitting diode comprises a substrate, a 20 buffer layer, a 30 lower limiting layer, a 41 first quantum dot active layer, a 42 second quantum dot active layer, a 43 third quantum dot active layer, a 50 upper limiting layer, a 60 ohmic contact layer.

Detailed Description

The invention is described in detail below with reference to the figures and the embodiments.

Example (b): sample 1

A method for preparing an indium arsenide/indium phosphide quantum dot laser epitaxial wafer with an ultra-wide light-emitting spectrum comprises the following steps:

step 1: selecting a substrate 10, the substrate being n^＋The type indium phosphide single-crystal wafer has a crystal orientation of (100), a doping element of Si and a doping concentration of (1-3)×10¹⁸cm^-3。

Step 2: epitaxially growing an indium phosphide buffer layer 20 on the indium phosphide substrate, wherein the indium phosphide buffer layer has a growth thickness of 500nm, and is doped n-type with Si as a doping element at a doping concentration of 1 × 10¹⁸ cm^-3。

And step 3: the lower limiting layer 30 of indium gallium arsenic phosphorus is epitaxially grown on the indium phosphide buffer layer 20, the growth thickness is 200nm, the lower limiting layer is an intrinsic material, and doping is not carried out.

And 4, step 4: through the regulation and control of the deposition thickness of the quantum dots and the thickness of the first cover layer, quantum dot active layers with different sizes and heights of the grown quantum dots are stacked on the limiting layers respectively under the indium gallium arsenic phosphorus:

and epitaxially growing a multi-period indium arsenide quantum dot active layer on the limiting layer 30 under the indium gallium arsenide phosphor respectively, wherein the period number (the number of layers) of the multi-period indium arsenide quantum dot active layer is 1-30. Each quantum dot active layer comprises three layers of structures, namely a quantum dot layer, a first cover layer and a second cover layer.

The quantum dot active layer cycle number selected in this embodiment is 3, and is respectively labeled as the first quantum dot active layer 41, the second quantum dot active layer 42, and the third quantum dot active layer 43.

The first quantum dot layer of the first quantum dot active layer 41 is labeled 411, the corresponding first cap layer is 412, and the second cap layer is 413;

the second quantum dot layer of the second quantum dot active layer 42 is labeled 421, the corresponding first cap layer is 422, and the second cap layer is 423;

the third quantum dot layer of the third quantum dot active layer 43 is labeled 431, and the corresponding first cap layer is 432 and the second cap layer is 433.

Wherein the growth temperature of the first quantum dot layer 411 is 490 deg.c, the deposition rate is 0.25ML/s, and the deposition thickness is 1.5 ML. Then, a first cap layer 412 is grown on the first quantum dot layer 411 at 490 deg.C, with V/III of 200, and a thickness of 8 nm. Then, a second cap layer 413 was grown to a thickness of 35nm at a growth temperature of 550 ℃.

Then, the second quantum dot active layer 42 is grown: first, a second quantum dot layer 421 is grown at a growth temperature of 490 deg.C, a deposition rate of 0.25ML/s, and a deposition thickness of 2.0 ML. A first cap layer 422 is grown on the second quantum dot layer 421 at 490 c to a thickness of 10 nm. A second cap layer 423 layer was then grown to a thickness of 35nm at a growth temperature of 550 c.

Finally, the third quantum dot active layer 43 is grown: first, a third quantum dot layer 431 is grown at a growth temperature of 490 deg.C, a deposition rate of 0.25ML/s, and a deposition thickness of 2.5 ML. A first cap layer 432 is grown on the third quantum dot layer 431 at 490 c with v/iii of 200 and a deposition thickness of 12 nm. A second capping layer 433 was then grown to a thickness of 35nm at a growth temperature of 550 c.

And 5: and depositing the limiting layers 50 on the indium gallium arsenic phosphorus respectively on the indium arsenide quantum dot active layer, wherein the growth thickness is 200nm, the limiting layers are intrinsic materials and are not doped.

Step 6: depositing an InGaAs ohmic contact layer 60 on the respective confinement layer on the InGaAsP with a growth thickness of 200nm, p-doping with Zn element and a doping concentration of 2 × 10¹⁹ cm^-3。

Comparative example: sample 2

To further illustrate the ultra-broad spectrum characteristics of the samples grown according to the method of the present invention, sample 2 was prepared according to the procedure described above for sample 1,

the difference lies in that: the thickness of the first quantum dot layer in the first quantum dot active layer 41 is 2 ML. The rest of the quantum dots adopt the same growth conditions, so that the sizes and the heights of the prepared quantum dots are concentrated in an interval as much as possible.

As shown in fig. 2, a graph comparing the photoluminescence spectra (PL) of sample 1 and sample 2 is shown. From the PL results of the two samples, it can be seen that the method of growing the quantum dot active layer with different sizes and heights of the quantum dots in a stacking manner can effectively widen the light emission spectrum width of the quantum dot active region.

Therefore, based on the method, the growth of the laminated structure quantum dots as the active region of the semiconductor quantum dot laser can enable the laser to have ultra-wide gain spectrum and excellent tunable performance.

The invention adjusts the size of the grown quantum dots by controlling the deposition thickness of the quantum dots, the size and the shape of the quantum dots are different, and the light-emitting wavelength is also different. By adjusting the deposition thickness of the quantum dot layer, the size of the quantum dot can be effectively adjusted, and the light-emitting wavelength of the quantum dot can be further changed. Meanwhile, the change of the height of the quantum dot can also obviously influence the position of the ground state energy level of the quantum dot, so that the light-emitting wavelength of the quantum dot is changed. The height of the quantum dots and the distribution uniformity thereof can be effectively controlled by a two-step covering layer technology.

The process of the two-step capping method is as follows: after the quantum dots are deposited and cured, a first cover layer is grown, and the thickness of the first cover layer is generally lower than the height of the quantum dots. Due to the large lattice mismatch energy between the cap layer and the tops of the quantum dots, the cap layer preferentially grows on the wetting layer between the quantum dots. Since the total thickness of the first cap layer is lower than the height of the larger quantum dots, the tops of the larger quantum dots are exposed to a group V atmosphere. In this way, the top indium arsenide undergoes an exchange reaction with phosphorus atoms in the group V atmosphere, forming an indium (arsenic) phosphide material with a smaller lattice constant than indium arsenide. The newly formed indium (arsenic) phosphide, under stress, tends to migrate the indium atoms to the region in the middle of the spot. As a result, the top indium arsenide of the quantum dots is flattened, and the height of the quantum dots is determined by the thickness of the first cover layer.

The method can realize the controllable adjustment of the light-emitting wavelength and the spectral width of the indium arsenide/indium phosphide quantum dot light wavelength within the range from 1.3-1.7 microns to 400nm, and is an ideal material for preparing tunable lasers.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It should be understood by those skilled in the art that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by using equivalent alternatives or equivalent variations fall within the scope of the present invention.