JPH1168239A - Manufacturing method of quantum dots - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing a quantum dot, which has a function of 1.3 [μ].
[m] In order to stably obtain InGaAs quantum dots that emit light in the band, the number of repetitions of the alternate supply of the raw material is to be uniquely determined for certain growth conditions by a simple means. SOLUTION: A group III-V semiconductor thin film having a second lattice constant is formed by repeating a step of alternately supplying a group III organic metal material and a group V material on a semiconductor base having a first lattice constant. In the process of producing quantum dots by using the method of the present invention, the group III-V semiconductor thin film is formed using the crystal growth temperature and the number of repetitions N of alternately supplying the raw materials as a growth parameter, and the growth parameter is such that the crystal growth temperature is 30 ° C. or lower. And the number of repetitions N of alternate material supply is M at the number of repetitions N ₀ of alternate material supply when the growth mode of the thin film at each crystal growth temperature changes from two-dimensional growth to three-dimensional growth.
(M> 1) The region R satisfies the condition that changes more than twice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 1.3 ± 0.05 [.mu.m]
The present invention relates to a method for manufacturing a quantum dot that emits light in a wavelength band called a 1.3 [μm] band.

At present, semiconductor lasers using a quantum dot structure capable of realizing three-dimensional quantum confinement as an active layer have been actively studied, and quantum lasers having a crystal composition that emits light in a 1.3 [μm] band have been developed. If the dot can be manufactured, the differential gain is improved depending on the state density of the delta function, and it is expected that the low threshold oscillation exceeding the quantum well laser and the high temperature operation characteristics are improved.

[0003] The present invention intends to disclose means for producing quantum dots having a crystal composition emitting light in the 1.3 [μm] band with good reproducibility.

[0004]

2. Description of the Related Art In the early days of manufacturing quantum dots, an electron lithography technique or a technique for finely processing a semiconductor crystal using a focused ion beam was used.

[0005] However, due to problems such as limitations and damages of nano-scale fine processing, the above-mentioned methods have been abolished, and in recent years, the natural formation technique during crystal growth has been exclusively used.

[0006] There are several methods for producing quantum dots by crystal growth.
This is a method for manufacturing a quantum dot utilizing crystal growth of a lattice mismatched material.

FIG. 3 is a cutaway side view of a main part showing a quantum dot at a key point in a manufacturing process for explaining a conventional technique.

3 (A) 3- (1) Group III-V semiconductor layer 2 having a lattice constant larger than the first lattice constant on a semiconductor substrate 1 having a first lattice constant.
Grow.

In this case, the group III-V semiconductor layer is grown in a two-dimensional layer at the beginning of the growth due to the lattice mismatch.

Referring to FIG. 3B, 3- (2) When the growing semiconductor layer 2 reaches a certain thickness, a nano-scale three-dimensional island 3 is formed thereon. This phenomenon is what is called SK (Transki-Krastan).
ov) growth.

As a material of a quantum dot having a crystal composition that emits light in the 1.3 [μm] band, InGaAs on GaAs is used.
s can be used, and as a crystal growth technique for forming the same, metalorganic vapor phase epitaxy (metalorganic) can be used.
vapor phasepitaxis: MOVP
E) method, molecular beam epitaxial growth (molecula)
r beam epitaxy (MBE) method, MOVP
A method of alternately supplying raw materials by the E method or the MBE method is known.

In any of these growth methods, 1.3 is used.
InGaAs quantum dots emitting in the [μm] band have been obtained, but the growth conditions are not established such that a quantum dot laser that can be used commercially is manufactured.

For example, in the method of alternately supplying a group III organometallic material and a group V material, the number of repetitions of the alternate supply of the material is set to 10 to 24 at a growth temperature of 420 ° C. to 500 ° C. It has been reported that InGaAs quantum dots that emit light in the 1.3 [μm] band can be produced by fixing either one of the growth temperature or the number of repetitions of alternate supply of the raw material and changing the other. This is the result obtained, and there is a problem in adopting it as a stable mass production technology.

That is, in the alternate material supply method, the number of repetitions of alternate material supply depends on the amount of material supply per one time or the material supply time. Not something.

[0015]

According to the present invention, 1.3 is used.
In order to stably obtain InGaAs quantum dots that emit light in the [μm] band, the number of repetitions of the alternate supply of the raw material is to be uniquely determined for certain growth conditions by a simple means.

[0016]

According to the present invention, when a quantum dot is generated by applying the alternate material supply method, the number of repetitions of the alternate material supply is uniquely specified for a certain growth condition. Basically, normalization is performed using the number of repetitions N ₀ when the style changes from two-dimensional growth to three-dimensional growth.

[0017] That is, the two-dimensional repetition count when changing the three-dimensional growth from the growth N ₀ can be determined uniquely with respect to certain growth conditions, the number of repetitions N ₀ M times (M> 1 ) To emit light in the 1.3 [μm] band.
GaAs quantum dots can be obtained.

In the study of the method for alternately supplying the raw material conducted in the practice of the present invention, the crystal growth temperature was set to 10 ° C.
By changing the number of repetitions of alternate supply in increments of up to 20 [° C.] and in increments of two, a clear region exists in the growth parameters of InGaAs quantum dots that emit light in the 1.3 [μm] band. Was found.

FIG. 1 is a map of growth conditions obtained by measuring photoluminescence (PL) of each sample crystal, in which the vertical axis indicates the crystal growth temperature, and the horizontal axis indicates the material alternation. The number of repetitions of the supply is taken, and in each figure in the map, the PL intensity is taken on the vertical axis, and the wavelength [μm] is taken on the horizontal axis.

According to the experiment from which this data was obtained, the crystal growth temperature ranged from 500 ° C. to 560 ° C.
In the range of [° C.] and the number of repetitions N of the alternate material supply, the crystal growth mode was changed from two-dimensional growth to three times.
The number of repetitions N ₀ when changing to dimensional growth is approximately 1.3.
InG that emits light in the 1.3 [μm] band
It has been found that aAs quantum dots can be obtained.

Therefore, the increment of the crystal growth temperature is set to 60
If it is set to 30 [° C.] or less, which is half of [° C.],
A growth temperature range of InGaAs quantum dots emitting light in the 3 [μm] band can be obtained.

When the crystal growth temperature is changed, if the swing width (step width) is made large, for example, 50 ° C., the growth temperature region cannot be limited. That is, in order to determine two growth temperatures, the growth temperature must be at least half of 60 ° C. or less, and therefore 30 ° C. or less.

Regarding the number of repetitions of the alternate material supply, the growth temperature is in the range of 500 ° C. to 560 ° C.
If the number of repetitions N _{0 at which} the growth mode changes from two-dimensional growth to three-dimensional growth is set to 1.3 times or more, it is possible to obtain InGaAs quantum dots that emit light in the 1.3 [μm] band with good reproducibility. it can.

FIG. 2 is a diagram for explaining the crystal growth conditions in the present invention. The vertical axis represents the growth temperature, and FIG.
The number of repetitions N of the alternate material supply is plotted on the horizontal axis.

In the figure, L1 is the boundary of the number of repetitions N ₀ of the alternate material supply at the time when the growth mode changes from two-dimensional growth to three-dimensional growth, and L2 is the number of repetitions of the alternate material supply of 1. The boundary line, 3N ₀ , R is 1.3 [μ
[m] shows growth condition regions in which quantum dots emitting light in the band are obtained. FIG. 2 is extracted from the data shown in FIG.

From the above, in the method of manufacturing a quantum dot according to the present invention, (1) a group III organic metal material and a group V material are alternately supplied on a semiconductor base having a first lattice constant. Group III having a second lattice constant different from the first lattice constant by repeating the process
In the process of forming the group V semiconductor thin film and forming quantum dots, the group III-V semiconductor thin film is formed using the crystal growth temperature and the number of repetitions N of alternately supplying the raw materials as growth parameters, and the growth parameter is a crystal. Growth temperature is 30
[° C.] or less, and the number of repetitions N of alternate material supply is the number of repetitions of alternate material supply when the thin film growth mode changes from two-dimensional growth to three-dimensional growth at each crystal growth temperature. Characterized by being in an area that satisfies the condition that changes by M (M> 1) times or more of N ₀ , or

(2) In the above (1), the semiconductor having the first lattice constant is GaAs, the group III-V semiconductor having the second lattice constant is InGaAs, and the raw material is alternately supplied. The number of repetitions N is at least 1.3 times the number of repetitions N ₀ of the alternate material supply, or

(3) In the above (1) or (2), the crystal growth temperature is selected from the range of 500 ° C. to 560 ° C.

By adopting the above means, 1.3 [μ
m] The crystal growth conditions for stably obtaining InGaAs quantum dots that emit light in the band, that is, the number of repetitions of the alternate supply of raw materials can be uniquely determined with respect to certain growth conditions. It is possible to lower the threshold value of the laser and improve the temperature characteristics.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case of manufacturing a sample having the data shown in FIGS. 1 and 2 will be specifically described as an embodiment of the present invention.

The MOVPE method is applied, and trimethylindium dimethylethylamine (TM
IDMEA: (CH ₃ ) ₃ InN (CH ₃ ) ₂ (C ₂ H
₅ )) Trimethylgallium (TMGa: Ga (C
H ₃ ) ₃ ) Arsine (AsH ₃ ), hydrogen (H ₂ ) as a carrier gas, a growth pressure of 15 [Torr], and a surface index (100) of GaAs.
TMIMEA (2 [seconds]) → TM
Ga (0.3 [sec]) → H ₂ (3 [sec]) → AsH
₃ (7 [sec]) → H ₂ (0.5 [sec]) in this order to form an InGaAs thin film.

The time in parentheses added to the supply order of each raw material is the supply time of each raw material or the purge time depending on H _2. FIG. 1 shows the room temperature of the sample formed as described above at room temperature. It was prepared by measuring a PL spectrum.

When performing the above-mentioned growth, the growth temperature is in the range of 490 ° C. to 580 ° C. and 10 ° C.
The number of repetitions was changed in the range of 12 to 22 times.

After the formation of the InGaAs thin film, a GaAs thin film having a thickness of 30 [nm] was formed at each growth temperature.

The supply time of the above-mentioned group III raw material is set at a temperature of 50.
ALE of InAs and GaAs at 0 ° C. (at
When converted into an omic layer epitaxy (growth rate), the supply rate is equivalent to InAs: 0.5 ML / cycle (ML is a molecular layer) and GaAs: 0.05 ML / cycle.

According to the mapping of the PL spectrum according to the growth temperature and the number of repetitions, that is, from the map of the growth conditions, it is possible to divide the growth conditions into regions in which similar PL spectra can be obtained. The boundaries S1 and S2 of the area are shown.

First, when the number of repetitions is small, the growth mode is two-dimensional growth, and no InGaAs quantum dots are formed. After a certain number of repetitions N ₀ , three-dimensional InGaAs quantum dots are formed. Begin to be.

InGaAs at the beginning of formation
The quantum dots emit light in the 1.2 [μm] band, and the emission half width is as wide as about 100 [meV].
In the range of 00 [° C] to 560 [° C], when the number of repetitions is set to a value larger than a certain value, the half width of light emission shows 30 [meV] to 50 [meV] in the 1.3 [μm] band and emits light sharply. InGaAs quantum dots are obtained.

At each growth temperature, the ratio of the number of repetitions N at which an InGaAs quantum dot emitting light in the 1.3 [μm] band starts to be formed and the number of repetitions N _{0 at which} the two-dimensional growth changes to the three-dimensional growth is: It looks like this: For a temperature of 500 [℃] to 540 [℃] _{N = 18, N 0 = ~14} N / N 0 = ~1.29 temperature 560 when the [℃] _{N = ~18, N 0 = ~22} N / N ₀ = 1.22

Accordingly, the increment of the growth temperature is set at 30 ° C. or less, and the number of repetitions N of the alternate material supply is changed to one of the number of repetitions N ₀ of the alternate material supply when changing from the two-dimensional growth to the three-dimensional growth. By changing to more than 3 times,
The growth parameter region of the InGaAs quantum dot that emits light sharply in the 1.3 [μm] band can be determined.

The growth parameter region surrounded by the boundary line S2 shown in FIG. 1 corresponds to the growth condition region R shown in FIG. 2, and the growth parameter region between the boundary lines S1 and S2 is shown in FIG. It corresponds to the area between the visible boundaries L1 and L2.

[0042]

In the method of manufacturing a quantum dot according to the present invention, the step of alternately supplying a group III organometallic material and a group V material on a semiconductor substrate having a first lattice constant is repeated. In the process of forming a group III-V semiconductor thin film having a second lattice constant different from the lattice constant of the group III and generating quantum dots, the group III-V semiconductor thin film has a crystal growth temperature and a repetition number N of alternately supplying the raw material. The crystal growth temperature varies in steps of 30 ° C. or less, and the number of repetitions N of the alternate supply of the raw material is changed from two-dimensional growth at each crystal growth temperature. It is in a region that satisfies the condition that the number of repetitions N ₀ of the alternate material supply when changing to three-dimensional growth is M (M> 1) times or more.

By adopting the above configuration, 1.3 [μ
m] The crystal growth conditions for stably obtaining InGaAs quantum dots that emit light in the band, that is, the number of repetitions of the alternate supply of raw materials can be uniquely determined with respect to certain growth conditions. It is possible to lower the threshold value of the laser and improve the temperature characteristics.

[Brief description of the drawings]

FIG. 1 shows the photoluminescence (ph) of each sample crystal.
6 is a map of the growth conditions obtained by measuring the luminescence (PL).

FIG. 2 is a diagram for explaining crystal growth conditions in the present invention.

FIG. 3 is a fragmentary side view showing a quantum dot at a key point in a manufacturing process for explaining a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 semiconductor base having first lattice constant 2 group III-V semiconductor layer 3 three-dimensional island (quantum dot)

Claims (3)

[Claims] 1. A group III material having a second lattice constant different from the first lattice constant by repeating a process of alternately supplying a group III metal organic material and a group V material on a semiconductor substrate having a first lattice constant. In the process of forming a group V semiconductor thin film and forming quantum dots, the group III-V semiconductor thin film is formed using a crystal growth temperature and the number of repetitions N of alternate supply of raw materials as a growth parameter, and the growth parameter is When the crystal growth temperature changes at a step width of 30 ° C. or less and the number N of times of alternately supplying the raw material changes, the raw material when the growth mode of the thin film at each crystal growth temperature changes from two-dimensional growth to three-dimensional growth method of manufacturing a quantum dot, characterized in that located in satisfying the region of alternating M (M> 1) number of times of repetition N ₀ of the feed times. 2. The semiconductor having a first lattice constant is GaAs.
And the group III-V semiconductor having the second lattice constant is InGaAs, and the number of repetitions N of the alternate material supply is at least 1.3 times the number of repetitions N ₀ of the alternate material supply. The method for producing a quantum dot according to claim 1. 3. A crystal growth temperature of 500 ° C. to 560.
3. The method according to claim 1, wherein the temperature is selected within a range of [° C.].