JPH09148624A - Manufacture of semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reproducibility of characteristics in the manufacture of a semiconductor element of a quantum dot structure. SOLUTION: When semiconductor microcrystal is formed in a quantum dot structure, different lattice constant is selected from the lattice constant in a bulk state of the semiconductor crystal which forms microcrystal and the lattice constant in bulk state of semiconductor crystal forming energy barrier. Etching pits are formed on the surface by etching the base layer crystal just before the growth of the semiconductor microcrystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element manufacturing method and a semiconductor element manufactured by the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a semiconductor device provided with semiconductor quantum dots manufactured by using the above-mentioned three-dimensional growth has poor reproducibility in characteristics such as light emission intensity and light receiving sensitivity, and a device having stable characteristics can be obtained. There was a problem such as not.

[0003]

This is because the density of the semiconductor crystallites in the quantum dots changes with each crystal growth. The present invention, in order to solve the above problems, in a semiconductor device using a semiconductor quantum dot structure, a semiconductor quantum dot for controlling the density of the crystallites with good reproducibility to obtain sufficient stability of device characteristics. A method of manufacturing a structure is provided.

[0004]

In order to solve the above-mentioned problems, a manufacturing method provided by the present invention is a semiconductor microcrystal made of a semiconductor having a cross-sectional size of about the de Broglie wavelength of an electron, and a potential energy. Is higher than the potential energy of the semiconductor microcrystal and functions as an energy barrier.
In manufacturing a semiconductor device having a three-dimensional quantum well (quantum dot), metal organic chemical vapor deposition (MO) is used for crystal growth.
In order to form the microcrystals by the CVD method, the lattice constant of the semiconductor crystals forming the microcrystals in the bulk state and the base during the growth of the microcrystals and the covering of the microcrystals after the growth of the microcrystals are required. When crystal growth is performed by utilizing three-dimensional growth of a lattice-mismatched system, semiconductor microcrystals are selected by selecting those having a lattice constant that differs by 1% or more in the bulk state of the semiconductor crystal that is grown to form an energy barrier. Immediately before the crystal growth, the crystal surface is etched to form etch pits on the surface, and subsequently semiconductor microcrystals and subsequent crystal growth are carried out.

When a quantum dot structure is manufactured by using the above method, Al is used as a semiconductor crystal forming a microcrystal.
_x Ga _1-x As (0 ≦ x ≦ 1) is used as a semiconductor crystal that forms an energy barrier, and GaAS _1-y P _y (0.2
It is preferable to use 5 ≦ y ≦ 1).

[0006]

By using the above-described manufacturing method, it is possible to obtain stable density reproducibility of fine crystals in the quantum dot structure as compared with the conventional one. Further, in a semiconductor element using this, reproducibility of characteristic values such as light emission intensity and light receiving sensitivity can be improved as compared with the conventional one.

[0007]

Next, an embodiment of the present invention will be described with reference to the drawings. First, the density reproducibility of GaAs microcrystals was investigated. The sample was manufactured by the following method. As the substrate, an n-type GaP semiconductor substrate whose plane orientation was off by 2 ° from the (100) plane in the <110> direction was used. The epitaxial growth was performed by a metal organic chemical vapor deposition method (MOCVD method). First, the substrate, which has been cleaned with an organic solvent and whose surface has been etched, is set in a reaction furnace of an MOCVD apparatus. This is heated to the growth temperature, and Ga is deposited on this substrate.
The P buffer layer and the GaAs _0.50 P _0.50 base layer are sequentially grown, and then the crystal growth is temporarily stopped. This substrate is cooled down to around room temperature and then taken out of the reaction furnace. Next, the surface of the substrate is etched with a hydrochloric acid / nitric acid-based etching solution to form minute etch pits on the surface. Then, this substrate was set again in the reaction furnace of the MOCVD apparatus and heated to form GaAs microcrystals by crystal growth. As a comparison, a sample was formed in which GaAs microcrystals were continuously formed without performing the growth interruption and etching.

The method used for forming the GaAs microcrystals utilizes a pseudo three-dimensional growth generally called SK mode growth, which is seen in the epitaxial growth of lattice mismatching system. In this embodiment, GaAs _0.50 P
_{When a} crystal having a lattice mismatching ratio such as GaAs with respect to the lattice constant of the _0.50 underlying crystal in the bulk state, that is, having a different lattice constant in the bulk state is epitaxially grown, the crystal is initially grown. Is known to have a three-dimensional island shape. If the crystal growth is continued as it is, these island-shaped crystals become large and coalesce due to the so-called Ostwald growth / sintering effect.
The shape changes to a three-dimensional film. This early growth 3
It is known that the shape and size of a three-dimensional island crystal, its variation, and the density depend on the material of the semiconductor crystal, the lattice mismatch rate, the plane orientation of the underlying crystal, and the like.

Further, it is known that this island-like growth is preferentially started from atomic steps or recesses on the underlying crystal. Therefore, it is possible to artificially control the generation of island crystals by forming minute recesses such as etch pits on the underlying crystal. Etch pits are formed by a phenomenon in which the etching rate is selectively increased at the position of a defect penetrating the crystal surface. In the case of this embodiment, an etch pit is formed by a crystal defect caused by a lattice mismatch between the GaP substrate and the GaAsP base crystal. Therefore, the density of GaAs microcrystals can be controlled by the defect density, and the defect density is GaAsP.
Since it depends on the thickness of the underlying crystal and the structure of the intermediate layer between the substrate and the GaP substrate, the defect density can be controlled by this thickness and structure. That is, the density of fine crystals can be controlled by the structure from the substrate to the base crystal.

FIG. 1 shows the Ga produced repeatedly 5 times.
9 is a table comparing changes in density of As semiconductor microcrystals. As shown in the figure, the density reproducibility is better when the growth interruption / etching is performed, as compared with the case where the growth interruption / etching is not performed. Quantum dots
It is a quantum well in which carriers are confined in zero dimensions, and the density of states function of carriers in a quantum dot becomes a delta function. Therefore, for example, when this is used for the light-receiving layer of the light-receiving element, light other than light with energy determined by the quantum level, that is, light with higher energy and light with lower energy, is ideally not absorbed, so it is extremely narrow. A light receiving element in the wavelength band is realized. Further, for example, when this is used for a light emitting layer of a light emitting element, light other than light having energy determined by a quantum level, that is, light having higher energy and light having lower energy, does not ideally emit light, and thus is extremely narrow. A light emitting device having a line width is realized. Since the characteristic value of the quantum dot effect changes depending on the density of the microcrystal, a method for obtaining the same density of the microcrystal with good reproducibility has been desired. But,
In the quantum dot device utilizing the three-dimensional growth that has been manufactured so far, it was impossible to repeatedly manufacture a device having uniform performance because the density of microcrystals was poor in reproducibility.

In order to confirm the effect of the present invention, growth interruption
10 each with and without etching
A light-receiving element having a quantum dot structure as a light-receiving layer was manufactured. FIG. 2 is a sectional view showing the structure. This light receiving element comprises an n-type GaP (100) 2 ° off <110> substrate 10 and a buffer layer 11 made of n-type GaP and an n-type Gp.
a quantum dot structure light-receiving layer 15 (thickness 0) composed of a base layer 12 (thickness 3 μm) made of aAs _0.60 P _0.40 , an i-type GaAs _0.60 P _0.40 energy barrier layer 13 and GaAs microcrystals 14. .2 μm), p-type GaAs
_0.60 P _0.40 emitter layer 16 (thickness 0.
4 μm), a window layer 17 (thickness 0.5 μm) made of p-type GaP, and a p-electrode 18 and an n-electrode 19 are formed. A lattice mismatch of about 1.6% between the bulk lattice constant of GaAs _0.60 P _0.40 used as the energy barrier layer 13 and the bulk lattice constant of GaAs used as the microcrystals (quantum dots) 14. Exists.

FIG. 3 shows the normalized output current when the light from the LED is incident on the above-mentioned light receiving element.
In the figure, (a) shows that the etching was performed just before the growth of the semiconductor microcrystal, and (b) shows that the etching was not performed immediately before the growth. It is shown that (a) according to the present invention has excellent reproducibility as compared with (b). Although the GaAsP-based mixed crystal semiconductor was selected as the material in this embodiment, regardless of this, for example, InGaA
The present invention can be realized by using other semiconductor materials such as sP. Further, in the above-mentioned embodiment, hydrochloric acid-
Although the nitric acid-based etching solution was used, another etching solution may be used, or etching may be performed in the reaction furnace with an etching gas. Further, although the light receiving element is manufactured in the above-mentioned embodiment, the present invention has the same effect in other semiconductor elements such as a light emitting element.

[0013]

As described above, according to the present invention, it is possible to manufacture a semiconductor element using a quantum dot structure with good reproducibility of characteristic values.

[Brief description of the drawings]

FIG. 1 is a diagram showing an effect of improving reproducibility by etching.

FIG. 2 is a sectional view showing a structure of a light receiving element that is an embodiment of the present invention.

FIG. 3 is a graph showing the reproducibility of the current output of the light receiving element.

[Explanation of symbols]

10 ... Semiconductor substrate, 11 ... Buffer layer, 12 ... N-type Ga
As _0.60 P _0.40 base layer, 13 ... i-type GaAs
_0.60 P _0.40 energy barrier layer, 14 ... GaAs
Quantum dots, 16 ... P-type GaAs _0.60 P _0.40 emitter layer, 17p-type GaP window layer, 18 ... P electrode, 19 ... N electrode.

Claims (2)

[Claims] 1. A crystallite having a cross-sectional size of about the de Broglie wavelength of an electron, and a semiconductor having a potential energy higher than that of the semiconductor crystallite and functioning as an energy barrier. A semiconductor device having a zero-dimensional quantum well (hereinafter referred to as a quantum dot) is formed by a metal organic chemical vapor deposition method (hereinafter, MOC).
In the case of manufacturing by the VD method), when the crystallites are formed, the lattice constant in the bulk state of the semiconductor crystal forming the crystallites is different from the lattice constant in the bulk state of the semiconductor crystal forming the energy barrier. And the etching of the surface of the underlying crystal immediately before the crystal growth of the semiconductor microcrystals to form an etch pit on the surface, followed by the growth of the semiconductor microcrystals and subsequent crystals. Law. 2. The semiconductor crystal material of the quantum dot structure comprises Al _x Ga as a semiconductor crystal forming microcrystals.
_1-x As (0 ≦ x ≦ 1) is used as a semiconductor crystal that surrounds the microcrystal and forms an energy barrier, and is GaAs _1-y P.
The semiconductor device according to claim 1, wherein _y (0.25 ≦ y ≦ 1) is used.