阅读说明：本技术 InAs/InSb复合型量子点及其生长方法 (InAs/InSb composite quantum dot and growth method thereof ) 是由 袁野 牛智川 苏向斌 杨成奥 张宇 于 2019-11-08 设计创作，主要内容包括：一种InAs/InSb复合型量子点及其生长方法,该生长方法包括对衬底进行脱氧处理,得到第一衬底；在第一衬底上生长缓冲层；在缓冲层上生长InAs/InSb复合型量子点层；在InAs/InSb复合型量子点层上生长盖层,即完成所述InAs/InSb复合型量子点的生长。本发明采用新型的外延方式生长InAs/InSb复合型量子点,有效规避了InAsSb量子点外延时带来的表面活性剂效应,获得了良好的量子点形貌,同时也实现了量子点的能级改善,便于实现获得发光质量良好的长波长量子点。(An InAs/InSb composite quantum dot and a growing method thereof are disclosed, the growing method comprises the steps of carrying out deoxidation treatment on a substrate to obtain a first substrate; growing a buffer layer on a first substrate; growing an InAs/InSb composite quantum dot layer on the buffer layer; and growing a cover layer on the InAs/InSb composite quantum dot layer to finish the growth of the InAs/InSb composite quantum dot. The InAs/InSb composite quantum dot is grown in a novel epitaxial mode, the surfactant effect caused by external time delay of the InAsSb quantum dot is effectively avoided, the good quantum dot appearance is obtained, the energy level improvement of the quantum dot is realized, and the long-wavelength quantum dot with good light-emitting quality is conveniently obtained.)

1. A growth method of InAs/InSb composite quantum dots comprises the following steps:

deoxidizing the substrate to obtain a first substrate;

growing a buffer layer on a first substrate;

growing an InAs/InSb composite quantum dot layer on the buffer layer;

and growing a cover layer on the InAs/InSb composite quantum dot layer to finish the growth of the InAs/InSb composite quantum dot.

2. The growing method according to claim 1,

the growth method of the InAs/InSb composite quantum dot layer comprises the following steps: and growing a pre-deposition layer on the buffer layer, and then growing InAs/InSb composite quantum dots on the pre-deposition layer to obtain the InAs/InSb composite quantum dot layer.

3. The growing method according to claim 1,

changing the temperature of the substrate during the deoxidation treatment step of the substrate, observing the change of a substrate surface reconstruction pattern, and recording the transition temperature Tc of the surface reconstruction from 'multiplying 2' to 'multiplying 4';

the growth temperature of the InAs/InSb composite quantum dots is 10-20 ℃ lower than the transition temperature Tc.

4. The growing method according to claim 1,

the InAs/InSb composite quantum dots are periodic InAs/InSb layers;

the growth time of the InSb layer in the InSb/InAs layer is 0.5-4.5 seconds;

the growth time of the InAs layer in the InSb/InAs layer is 0.5-4.5 seconds;

the material adopted by the predeposition layer comprises 2 MLInAs.

5. The growing method according to claim 1,

and performing degassing cleaning treatment before performing deoxidation treatment on the substrate.

6. The growing method according to claim 5,

the degassing cleaning process specifically includes: the substrate is degassed and cleaned for more than 4 hours in a vacuum environment at 180 to 200 ℃, and then a precleaning treatment is carried out for more than 1 hour at 400 to 420 ℃ in the vacuum environment.

7. The growing method according to claim 1,

the deoxidation temperature in the deoxidation treatment step is at least 40 ℃ higher than the deoxidation point temperature of the substrate;

the deoxidation treatment step is carried out in an As atmosphere.

8. The growing method according to claim 1,

the substrate is an N-type GaAs (001) substrate;

the buffer layer is made of GaAs;

the thickness of the buffer layer is 200 to 300 nanometers;

the growth temperature of the buffer layer is 610-630 ℃;

the material adopted by the cover layer comprises GaAs.

9. The growing method according to claim 1,

the cover layers comprise a first GaAs cover layer and a second GaAs cover layer;

the growth temperature of the first GaAs cover layer is 515-525 ℃;

the thickness of the first GaAs cover layer is 20 to 25 nanometers;

the growth temperature of the second GaAs cover layer is 620-640 ℃;

the thickness of the second GaAs cover layer is 20 to 25 nanometers.

10. An InAs/InSb composite quantum dot obtained by the growth method of any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of semiconductors, in particular to an InAs/InSb composite quantum dot and a growth method thereof.

Background

With the development of optical fiber communication and high-speed information, semiconductor lasers are used as light sources for optical fiber communication, and the requirements for the performance of semiconductor lasers are higher and higher. The InAs quantum dot laser based on GaAs substrate material epitaxy has the advantages of low threshold current density, high differential gain, high temperature stability, high modulation speed, low frequency chirp effect and the like due to the three-dimensional quantum confinement effect, and becomes an excellent choice for optical communication transmission light sources. However, due to the limitation of the energy band structure, the room temperature luminescence wavelength limit of the InAs quantum dot laser is about 1310nm, and it is difficult to reach the currently best optical fiber transmission low-loss window 1550 nm. Therefore, the emission wavelength of the quantum dot laser is further red-shifted to become an important direction for quantum dot research.

A novel mode for realizing the red shift of the wavelength of the quantum dots is to adopt InAsSb quantum dots to replace InAs quantum dots, and utilize a narrower band gap structure (0.106eV) of InAsSb to realize the red shift of the wavelength, however, because InAsSb has larger lattice mismatch relative to a GaAs substrate, when the InAsSb is used as a quantum dot material, the quantum dots are often saturated when the deposition amount is lower, the point also limits the luminous wavelength of InAsSb as the quantum dot material, and the surfactant effect of Sb can also deteriorate the appearance of the quantum dots, and a quantum short line is formed to weaken the three-dimensional quantum limiting effect of the quantum dots, so that the optical effect of the quantum dots is reduced. Therefore, how to alleviate the large lattice mismatch caused by the release of InAsSb and how to avoid the surfactant effect caused by Sb elements become important problems in the research of InAsSb quantum dots.

Disclosure of Invention

In view of the above, one of the main objectives of the present invention is to provide an InAs/InSb composite quantum dot and a method for growing the same, so as to at least partially solve at least one of the above technical problems.

In order to achieve the above object, according to an aspect of the present invention, there is provided a method for growing an InAs/InSb composite quantum dot, including:

deoxidizing the substrate to obtain a first substrate;

growing a buffer layer on a first substrate;

growing an InAs/InSb composite quantum dot layer on the buffer layer;

and growing a cover layer on the InAs/InSb composite quantum dot layer to finish the growth of the InAs/InSb composite quantum dot.

As a further aspect of the invention, the InAs/InSb composite quantum dot is obtained by adopting the growth method.

Based on the technical scheme, compared with the prior art, the InAs/InSb composite quantum dot and the growth method thereof have at least one of the following advantages:

(1) the InAs/InSb composite quantum dots are grown in a novel epitaxial mode, so that the surfactant effect caused by external time delay of the InAsSb quantum dots is effectively avoided, the good quantum dot appearance is obtained, the energy level of the quantum dots is improved, and the long-wavelength quantum dots with good light-emitting quality are conveniently obtained;

(2) according to the invention, 2ML (ML refers to a monoatomic layer) InAs quantum dots are epitaxially grown, and then InAs/InSb composite quantum dots are epitaxially grown on the InAs quantum dots which are already formed into islands, so that the problem that the InAsSb quantum dots are easily saturated prematurely due to large stress is solved, the quantum dot epitaxy with large deposition amount is realized, and a foundation is laid for further red shift of wavelength;

(3) the growth temperature of the quantum dots selected in the invention is 515-525 ℃, the deposition amount of 2ML InAs and the GaAs low-high temperature mixed growth of the cover layer are the results of experimental optimization, the thickness of the InAs layer in the InAs/InSb composite quantum dots and the thickness of the InSb layer are further adjusted according to the growth parameters optimized by the experiments, and the luminous wavelength and luminous efficiency of the composite quantum dots can be further improved by the growth cycle number.

Drawings

FIG. 1 is a schematic structural diagram of an InAs/InSb composite quantum dot in an embodiment of the invention;

FIG. 2 is a schematic diagram of the overall structure of an InAs/InSb composite quantum dot in the embodiment of the invention;

FIG. 3 is an AFM side view of a typical single point of an InAs/InSb composite quantum dot in an embodiment of the invention;

FIG. 4 is a comparison graph of the PL spectrum (77K) of the InAs/InSb composite quantum dot overall structure and the PL spectrum of 2ML InAs quantum dots in the embodiment of the invention.

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

The invention discloses a growth method of InAs/InSb composite quantum dots, which comprises the following steps:

deoxidizing the substrate to obtain a first substrate;

growing a buffer layer on a first substrate;

growing an InAs/InSb composite quantum dot layer on the buffer layer;

and growing a cover layer on the InAs/InSb composite quantum dot layer to finish the growth of the InAs/InSb composite quantum dot.

The growth method of the InAs/InSb composite quantum dot layer comprises the following steps: and growing a pre-deposition layer on the buffer layer, and then growing InAs/InSb composite quantum dots on the pre-deposition layer to obtain the InAs/InSb composite quantum dot layer.

Wherein, the substrate temperature is changed during the deoxidation treatment step to observe the substrate surface reconstruction pattern change, and the transition temperature Tc of the surface reconstruction from 'multiplying 2' to 'multiplying 4' is recorded;

the growth temperature of the InAs/InSb composite quantum dots is 10-20 ℃ lower than the transition temperature Tc.

The InAs/InSb composite quantum dots are periodic InAs/InSb layers;

wherein the growth time of the InSb layer in the InSb/InAs layer is 0.5-4.5 seconds;

wherein the growth time of the InAs layer in the InSb/InAs layer is 0.5-4.5 seconds;

wherein the material adopted by the pre-deposition layer comprises 2ML InAs.

Wherein, the substrate is subjected to a degassing cleaning process before being subjected to a deoxidation process.

Wherein the degas clean process step specifically comprises: the substrate is degassed and cleaned for more than 4 hours in a vacuum environment at 180 to 200 ℃, and then a precleaning treatment is carried out for more than 1 hour at 400 to 420 ℃ in the vacuum environment.

Wherein the deoxidation temperature in the deoxidation treatment step is at least 40 ℃ higher than the deoxidation point temperature of the substrate;

wherein the deoxidation treatment step is carried out in an As environment.

Wherein the substrate is an N-type GaAs (001) substrate;

the buffer layer is made of GaAs;

wherein the buffer layer has a thickness of 200 to 300 nanometers;

wherein the growth temperature of the buffer layer is 610-630 ℃;

wherein, the material adopted by the cover layer comprises GaAs.

Wherein the cap layer comprises a first GaAs cap layer and a second GaAs cap layer;

wherein the growth temperature of the first GaAs cover layer is 515 to 525 ℃;

wherein the thickness of the first GaAs cover layer is 20 to 25 nanometers;

wherein the growth temperature of the second GaAs cover layer is 620-640 ℃;

wherein the thickness of the second GaAs cap layer is 20 to 25 nanometers.

The invention also discloses an InAs/InSb composite quantum dot obtained by adopting the growth method.

In an exemplary embodiment, the method for epitaxially growing InAs/InSb composite quantum dots by using a digital alloy growth mode comprises the following steps:

A. preparing a GaAs substrate, and performing degassing cleaning treatment;

B. deoxidizing the substrate, changing the temperature of the substrate, observing the change of the surface reconstruction pattern, and recording the temperature Tc of the surface reconstruction converted from 'multiplied by 2' to 'multiplied by 4';

C. growing a buffer layer;

D. growing an InAs/InSb composite quantum dot layer;

E. and growing a GaAs cover layer.

Wherein the substrate type is an N-type GaAs (001) substrate.

Wherein, the buffer layer is made of GaAs.

The growth method of the InAs/InSb composite quantum dot layer comprises the following steps: growing a 2ML (ML refers to a monoatomic layer) InAs pre-deposition layer on the buffer layer, sequentially and periodically growing InSb/InAs on the InAs pre-deposition layer, and finally growing a 40-50nm GaAs cover layer.

The GaAs cover layers with the thickness of 40-50nm comprise a first GaAs cover layer with the thickness of 20-25nm and grown at a low temperature (515-.

The substrate is deoxidized and the temperature of the substrate is changed to observe the change of the surface reconstruction pattern, the temperature Tc of the surface reconstruction from 'multiplied by 2' to 'multiplied by 4' is recorded, the temperature of the deoxidized point of the substrate is 630 ℃, then the temperature is raised to 650 DEG and 670 ℃, the substrate is deoxidized and degassed, after 5 minutes, the temperature is reduced to 610 DEG and 630 ℃, the GaAs buffer layer is grown for 5 minutes, then the temperature is reduced to 500 ℃, the change of the surface reconstruction pattern from 'multiplied by 2' to 'multiplied by 4' is observed through a Reflection High Energy Electron Diffractometer (RHEED), and the reconstruction transition temperature Tc is recorded.

Sequentially and periodically growing InSb/InAs on the InAs pre-deposition layer; the growth time of the InSb layer and the InAs layer is 4s and 1s respectively.

The technical solution of the present invention is further illustrated by the following specific embodiments in conjunction with the accompanying drawings. It should be noted that the following specific examples are given by way of illustration only and the scope of the present invention is not limited thereto.

The growth method for epitaxially growing the InAs/InSb composite quantum dots by using the growth method of the digital alloy in the embodiment includes:

A. preparing a GaAs substrate, and performing degassing cleaning treatment;

B. deoxidizing the substrate and observing the surface reconstruction;

C. growing a buffer layer;

D. growing InAs/InSb composite quantum dots;

E. and growing a GaAs cover layer.

Wherein the substrate type in the step A is an N-type GaAs (001) substrate.

Wherein the substrate in step A is in a vacuum environment (less than 10 deg.C) at 190 deg.C^-8Torr) for more than 4 hours, and then continuing to perform a pre-cleaning treatment at 420 ℃ for more than 1 hour in a vacuum environment.

Wherein the deoxidation temperature in the step B is 40 ℃ above the deoxidation point temperature, and the deoxidation treatment is carried out in an As environment.

Wherein the As pressure is 3E-6Torr and the deoxidation temperature is 660 ℃ for 5 minutes. After 5 minutes, the temperature was reduced to 620 ℃ and the GaAs layer was grown for 5 minutes, then the temperature was reduced to 500 ℃ and the surface reconstruction pattern change was observed, recording the temperature Tc at which the surface reconstruction changed from 'by 2' to 'by 4'.

Wherein, the epitaxial thickness of the GaAs buffer layer in the step C is 200nm, the growth temperature is 620 ℃, and the V/III (namely the beam flow ratio of the V group element to the III group element) ratio is 20 times.

The InAs/InSb composite quantum dot structure is shown in figure 1, the InAs pre-deposition layer adopted in the step D is 2ML, InSb/InAs periodically grows on the InAs pre-deposition layer in sequence, and finally a GaAs cover layer of 40nm grows.

Wherein the growth temperature of the 2ML InAs pre-deposition layer is 520 ℃, the growth speed of the InAs is 0.05ML/s, the island forming time is 34s, the V/III ratio is 25 times, and the growth time is 40 s.

Wherein, the structure of the compound quantum dot layer of InAs/InSb comprises an N layer of aML InSb/bML InAs (wherein the theory of a, b and N can be any value)

In this embodiment, N is 5, a is 0.2, and b is 0.05.

The growth temperature of the InAs/InSb composite quantum dot is 520 ℃, wherein the V/III ratio of the InSb layer is 10 times, and the V/III ratio of the InAs layer is 25 times.

Wherein the thickness of the GaAs cover layer is 40 nm.

The 40nmGaAs cover layer is composed of a 20nm first GaAs cover layer (growth temperature of 520 ℃) and a 20nm second GaAs cover layer (growth temperature of 630 ℃).

In the InAs/InSb composite quantum dot overall structure grown in this embodiment, a three-layer quantum dot structure is adopted, and a layer of bare quantum dots is grown again on the surface layer to test the performance of the quantum dots, as shown in fig. 2.

In the AFM image (as shown in fig. 3) and the 77K fluorescence spectrogram (as shown in fig. 4) of the InAs/InSb composite quantum dot of the present embodiment, it can be seen that the InAs/InSb composite quantum dot has effectively avoided the quantum stub effect introduced by Sb, the AFM result is a substantially semi-elliptical structure, and compared with the conventional InAs quantum dot, the wavelength of the fluorescence spectrum is red-shifted from about 1040nm to 1200nm, so that a good wavelength red-shift effect is achieved.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.