JPH0817264B2 - Quantum box and quantum wire fabrication method, and semiconductor optical amplifier using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used in optical devices such as semiconductor optical amplifiers.

[0002]

2. Description of the Related Art In the field of recent long-distance optical transmission of optical communication, an optical amplifying element plays an important role. As the wavelength multiplexing of optical communication progresses in the future, an optical amplification element that simultaneously amplifies light of a plurality of wavelengths is desired, but it has not been realized yet.

On the other hand, due to the recent demand for higher performance of semiconductor devices such as semiconductor lasers and FET devices, low-dimensional quantum structures such as quantum wires and quantum boxes have attracted attention.

In such a low-dimensional quantum structure, the gain increases at a specific wavelength due to the quantum effect, and the wavelength changes depending on the size of the quantum wire (quantum box). As a characteristic of quantum wires and quantum boxes applied to optical devices and the like, a structure having a size of several tens nm and low damage, uniform and high density is required. To create a quantum structure, 1
Since an unprecedented ultrafine processing technology of the order of 0 nm is required, various measures have been taken.

As the most widely used semiconductor processing method, a pattern formed by photolithography or electron beam lithography on a semiconductor (100) substrate is formed, and then wet chemical etching using a liquid etching solution, Alternatively, there is a method of etching by dry etching using a reactive gas.

FIG. 6 shows a conventional method for producing a quantum box using dry etching (related literature: Applied Physics Letters, 1987, vol. 50, p. 413).

After a semiconductor laminated structure composed of a barrier layer 62 and a quantum well layer 63 is formed on a (100) compound semiconductor substrate 61, a fine dot-shaped mask pattern 64 is formed on the semiconductor laminated structure by electron beam exposure or the like. To form.

The method of forming the dot-shaped mask pattern will be described more specifically. After forming a large number of circular holes on the PMMA resist by electron beam exposure,
A metal is vapor-deposited on it, and then P is lifted off.
A general method is to remove the MMA resist and form a circular dot metal mask on the substrate.

Next, after the lower barrier layer 62 is etched by dry etching using the above-mentioned dot-shaped mask pattern, the barrier layer 62 is embedded and grown to form a quantum box 65.

[0010]

It is important to apply a uniform and high density semiconductor quantum structure such as a quantum box to a device such as a quantum box. The method using etching is suitable for forming a high-density structure because vertical etching is possible, but it is only possible to obtain a structure that directly reflects the large damage and fluctuations in the pattern shape. However, there is a problem in that

Although the method using the (100) substrate and wet etching is a processing method with low damage, it is difficult to obtain a dot shape having a vertical side surface because the etching rate depends on the crystal plane orientation. However, there is a drawback that the undercut is also large, and it is difficult to obtain a high-density structure.

According to the present invention, by producing a quantum box with low damage and high density which is not affected by fluctuations in the shape of an etching mask pattern, or by producing quantum wires by processing with low undercut and low damage, a plurality of wavelengths can be obtained. It is an object of the present invention to realize a semiconductor optical amplification element having a function of simultaneously amplifying the above light.

[0013]

In order to achieve the above object, a method for producing a quantum box or quantum wire of the present invention is
Preparing a conductor (311) B substrate,
Forming a quantum well structure region on a conductor (311) B substrate
Steps and dots or thin lines on the quantum well structure region
Forming an etching mask pattern of
Orientation of the quantum well structure region in which the mask pattern is formed
And a step of immersing in a highly selective etching solution
Method Ru Der.

Here, a dot-shaped or thin line-shaped etching mask is used.
A plurality of mask patterns are formed and their sizes and widths are different from each other.
Different sizes, quantum boxes and quantum wires of different sizes.
Ru preferably der in making.

Furthermore, using such a manufacturing method
Therefore, the semiconductor optical amplifier device of the present invention is provided with a pair of opposing
The electrode means and the electrode means are provided adjacent to either one of the electrode means.
The p-type semiconductor layer and the other electrode means.
N-type semiconductor layer, the p-type semiconductor layer and the n-type semiconductor layer
Semiconductor optical amplifier element having an active layer portion provided between
At least two active layers of different sizes
It has more than one type of quantum box and quantum wire .

[0016]

In the method of manufacturing the quantum box of the present invention , low damage
And high density, and is affected by the fluctuation of the mask pattern shape
Form a quantum box that does not exist.

In addition, in the method for producing a quantum wire of the present invention,
Te is you the formation of high-density quantum wires with low damage.

Then, a semiconductor using such a manufacturing method
The body light amplification element is made up of multiple quantum wires or
Of multiple wavelengths by using quantum boxes in the active layer.
Achieves simultaneous amplification of light.

Further, in this semiconductor optical amplifier device
Shows that quantum wires and boxes have a large gain only at specific wavelengths.
Since it has, it becomes noise other than the signal in the process of optical amplification.
Light Ru is canceled.

[0020]

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a structural diagram of a wavelength discrimination type semiconductor optical amplifier device using a quantum box or a quantum wire.

In FIG. 1A, 11 is p-Al _x G
a _1-x As layer (x = 0.5), 12 n-Al _x Ga _1-x As layer (x = 0.5), 13 undoped Al _x Ga _1-x As (x = 0.
3) region, 14 is a GaAs quantum box, and 15 is an electrode.
Undoped Al _x Ga _1-x As (x = 0.3) region 13 and Ga
The As quantum box 14 constitutes an active layer.

The x direction in the figure is the incident direction of light and the z direction is the injection direction of current. 14 GaAs quantum boxes are shown in Fig. 1.
As shown in (b), three types of quantum boxes having different sizes are provided in the y direction. The three types of quantum boxes have wavelengths of 810,
The size of each quantum box is determined so that it has a peak gain value near 820 and 830 nm.

The operation of the optical amplifying element in this embodiment will be described. An appropriate amount of current is injected from the z direction to inject the current into the GaAs quantum box 14 in the undoped Al _x Ga _1-x As (x = 0.3) region 13.

In this state, undoped Al _x Ga _1-x As
Towards the GaAs quantum box 14 in the (x = 0.3) region 13,
Light having a wavelength width of at least 700 to 900 nm is incident from the x direction.

The light incident on the GaAs quantum box 14 is 81
According to the respective characteristics having the peak value of the gain near 0, 820, 830 nm, approximately 810, 820,
It is amplified at three wavelengths of 30 nm at the same time, and is emitted as output light from the emission end face opposite to the incident end face.

By using quantum boxes of different sizes having a predetermined gain peak value in this way, amplification at a desired wavelength is possible, and since the gain peak of the quantum box is steep, the amplified output light is amplified. Each of the wavelengths is narrowed.

The method for manufacturing this optical amplifying element is the same as the conventional method for manufacturing a semiconductor laser except for the active layer portion.

A method of manufacturing the active layer portion will be described in detail. FIG. 2 is a process diagram of a manufacturing method when a quantum box is used as an active layer portion of the optical amplification element.

A (311) B substrate was used as the GaAs substrate. In FIG. 2, 21 is GaAs (311) B
Substrate, 22 is a barrier layer made of AlGaAs, and 23 is Ga
The quantum well layer made of As and 24 are SiO ₂ mask patterns.

As shown in FIG. 2A, GaAs (31
1) On the (311) B surface of the B substrate 21, a laminated structure composed of the barrier layer 22 and the quantum well layer 23 is formed by crystal growth, and then a SiO ₂ film is deposited.

Next, the SiO ₂ film was exposed to an electron beam to expose the GaAs substrate in the [0-11] direction and [2-3-3] direction.
After forming a rectangular dot pattern consisting of
The dot pattern is formed by S using a hydrofluoric acid-based etching solution.
An etching mask as shown in the drawing is formed by transferring to the iO ₂ film.

Next, as shown in FIG. 2B, SiO ₂
Using the dot mask pattern 24, sulfuric acid (concentration 100
%), Hydrogen peroxide (concentration: 30%), and a plane-orientation-selective etching solution composed of water to a depth at which the quantum well layer exists.

Then, as shown in FIG. 2 (c), after removing the etching mask, the quantum box 25 is formed by buried growth.
Is obtained.

By using the (311) B substrate in the process of such wet etching, (311)
A specific structure related to the plane orientation of the B substrate is obtained.

FIG. 3 shows a schematic structural diagram obtained by using a dot-shaped etching mask. The dotted line in FIG. 3 represents the etching mask. Compound semiconductors such as GaAs have a crystal plane orientation dependence on the wet etching rate,
There is a property that the etching rates of the (100) plane and the (111) A plane are low.

The dot structure shown in FIG. 3 is a triangular structure composed of (100) planes and (111) A planes, which have a low etching rate and appear during the wet etching process, and do not depend on the shape of the etching mask.

Therefore, in forming a mask pattern of the order of 10 nm, there is a phenomenon of mask pattern fluctuation due to the beam stability during electron beam exposure. , It is extremely effective in producing a uniform dot structure that is not affected by fluctuations in the etching mask.

Further, as a feature of the method for producing a dot structure using the wet etching of the (311) B substrate, in addition to the low damage and uniformity, the undercut is relatively vertical and comparative to that when the (100) substrate is used. Sometimes a small structure can be obtained.

Using the (100) substrate, four (10
A square dot structure consisting of (0) planes is created, but (1
11) It has a hem-shaped side that is side A and has a large undercut. On the other hand, the dot structure using the (311) B substrate reflects the crystal plane orientation of the (311) B substrate, and the undercut is half that of the (100) substrate. Wet etching of the (311) B substrate is effective for producing a high-density structure because the undercut is small.

By the above manufacturing method, a plurality of quantum boxes having different sizes can be manufactured in the active layer portion of the semiconductor optical amplifier device.

In this case, the size of the quantum box may be appropriately controlled according to the size of the electron beam exposure pattern.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

The second embodiment uses quantum wires as the active layer portion of the optical amplifying element, and the structure other than this active layer portion is the same as that of the first embodiment.

Also in this embodiment, it is possible to amplify at a desired wavelength by using quantum wires having different sizes (line thicknesses) having a predetermined gain peak value in the same manner as in the first embodiment. 810, 820, 83 at room temperature
Amplification is possible at 0 nm at the same time, and the gain peak of the quantum box is steep, so that the wavelength of the amplified output light can be extremely narrowed.

The method for producing this optical amplifying element is the same as the conventional method for producing a semiconductor laser except for the active layer portion.

FIG. 4 is a process diagram of a manufacturing method when a quantum wire is used as an active layer portion of the light amplification element.

A (311) B substrate was used as the GaAs substrate. In FIG. 4, 41 is GaAs (311) B
Substrate, 42 Barrier layer made of AlGaAs, 43 Ga
The quantum well layer made of As and 44 are SiO ₂ mask patterns.

As shown in FIG. 4A, GaAs (31
1) On the (311) B surface of the B substrate 41, a laminated structure including the barrier layer 42 and the quantum well layer 43 is formed by crystal growth, and then a SiO ₂ film is deposited.

Next, a stripe pattern is formed on the SiO ₂ film by electron beam exposure in the [0-11] direction of the GaAs substrate, and then the stripe pattern is formed into a SiO ₂ film using a hydrofluoric acid-based etching solution. An etching mask is formed by transferring.

Next, as shown in FIG. 4B, a sulfuric acid (concentration 100%) sulfuric acid (concentration 100%) is used by using a SiO ₂ thin line mask pattern 44.
Etching is performed to a depth at which the quantum well layer exists by using a plane orientation selective etching solution composed of hydrogen peroxide (concentration 30%) and water.

Next, as shown in FIG. 4C, after removing the etching mask, the quantum wires 45 are formed by burying growth.
Is obtained.

By using the (311) B substrate in the process of such wet etching, (311)
A specific structure related to the plane orientation of the B substrate is obtained.

FIG. 5 shows a sectional view of a thin line structure region 52 obtained by using the thin line etching mask 51 of this embodiment.

The fine line in FIG. 5 has an etching side surface vertical to the fine line produced by conventional wet etching and has a small undercut.

(11 on the left side of the thin line portion of the thin line structure region 52)
1) The undercut on the etched side surface composed of the A surface is almost zero, and the etched side surface composed of the (111) B surface on the right side has the same inclination as that of the conventional GaAs (100) substrate.

That is, when the (311) B substrate is used,
The undercut is half that in the case of using the conventional GaAs (100) substrate.

According to the method of manufacturing a quantum wire of this embodiment,
Since the undercut is small, it can be seen that it is effective for producing a high-density thin wire structure.

By the above manufacturing method, a plurality of quantum wires having different sizes can be manufactured in the active layer portion of the semiconductor optical amplifier device.

The size of the quantum wire may be controlled by the size of the electron beam exposure pattern.

Further, each of the optical amplifying devices manufactured by the first and second embodiments has a temperature of 81% at room temperature.
The light of three kinds of wavelengths of 0, 820, and 830 nm can be simultaneously amplified, but the light amplification element according to the present invention has a specific 3 It has the function of independently amplifying only different types of light.

[0062]

As described above, the present invention provides (311) B conversion
Wet energy with plane orientation selectivity using a compound semiconductor substrate
Etching mask by providing the etching process
A uniform and high-density amount that is not affected by fluctuations in the shape of the pattern
It realizes a child box .

Alternatively , on a (311) B compound semiconductor substrate
[0-11] direction thin line mask is used to select the plane orientation.
High density due to selective wet etching
It realizes a fine quantum wire .

Further, using such a manufacturing method, the semiconductor
Large gain at a specific wavelength in the active layer of the body light amplification element
If multiple types of quantum wires or boxes with
By installing in parallel with the incident direction of
Wavelength-discriminating light that individually amplifies light of several wavelengths simultaneously
It realizes an amplifying element .

[Brief description of drawings]

FIG. 1 is a structural diagram of a wavelength discrimination type optical amplification element according to the present invention.

FIG. 2 is a process diagram showing a method for manufacturing a quantum box according to the present invention.

FIG. 3 is a schematic structural diagram of a quantum box immediately after wet etching according to the present invention.

FIG. 4 is a process diagram showing a method for producing a quantum wire according to the present invention.

FIG. 5 is a schematic structural diagram of a quantum wire immediately after wet etching in the present invention.

FIG. 6 is a process diagram showing a conventional method of manufacturing a quantum box.

[Explanation of symbols]

11 p-AlGaAs layer 12 n-AlGaAs layer 13 undoped AlGaAs 14 GaAs quantum box 15 electrode 21 GaAs (311) B substrate 22 AlGaAs barrier layer 23 GaAs quantum well layer 24 SiO ₂ mask pattern 25 GaAs quantum box 41 GaAs (311) B Substrate 42 AlGaAs Barrier Layer 43 GaAs Quantum Well Layer 44 SiO ₂ Mask Pattern 45 GaAs Quantum Wire 51 SiO ₂ Mask 52 AlGaAs / GaAs Quantum Well Structure 61 (100) Compound Semiconductor Substrate 62 Barrier Layer 63 Quantum Well Layer 64 Etching Mask Pattern 65 Quantum box

Front page continued (72) Inventor Yukio Toyoda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-63-213384 (JP, A)

Claims (6)

[Claims] 1. A compound semiconductor (311) B substrate is prepared.
And a quantum on the compound semiconductor (311) B substrate.
Forming a well structure region and the quantum well structure region
A dot-shaped etching mask pattern on top of
Process and quantum well structure having the mask pattern
Step of immersing a region in an etching solution with high plane orientation selectivity
And a method for manufacturing a quantum box having. 2. A compound semiconductor (311) B substrate is prepared.
And a quantum on the compound semiconductor (311) B substrate.
Forming a well structure region and the quantum well structure region
On top of the thin line etching mask pattern in the [0-11] direction.
The step of forming a turn, and the mask pattern is formed.
Of quantum well structure region with large plane orientation selectivity
And a step of immersing the quantum wire in a solution. 3. A dot-shaped etching mask pattern
2. A plurality of devices are formed and different in size from each other.
How to make the above quantum box. 4. A fine line-shaped etching mask pattern
The method for producing a fine quantum wire according to claim 2, wherein several pieces are formed and have different widths . 5. A pair of electrode means facing each other, and any one of
A p-type semiconductor layer provided adjacent to one of the electrode means,
An n-type semiconductor layer provided adjacent to one of the electrode means, and
The active provided between the p-type semiconductor layer and the n-type semiconductor layer
A semiconductor optical amplification device having a layer portion, wherein the active layer
Has at least two types of quantum boxes of different sizes
The quantum box is a semiconductor optical amplifier device manufactured by the manufacturing method according to claim 3 . 6. A pair of electrode means facing each other, and any one of
A p-type semiconductor layer provided adjacent to one of the electrode means,
An n-type semiconductor layer provided adjacent to one of the electrode means, and
The active provided between the p-type semiconductor layer and the n-type semiconductor layer
A semiconductor optical amplification device having a layer portion, wherein the active layer
At least two types of quantum wires with different size parts
And the quantum wire is manufactured by the manufacturing method according to claim 4.
Semiconductor optical amplifier device.