JPS5880879A - Obtaining method for collision ionization coefficient ratio by junction of different semiconductor - Google Patents

Abstract

PURPOSE:To obtain a collision ionization coefficient ratio even by the junction of semiconductros of different types by laminating the semiconductors of different types, and setting both electrons and holes to move in a layer of the semiconductors of different ytpes isolated in space when both are flowed in parallel with the layer. CONSTITUTION:At least three layers and more of an alternative layer of semiconductors A and B to satisfy xA<xB, xA+EgA<xB+EgB, where xA represents electron affinity of the semiconductor B, EgA forbidden band width of the semiconductor A, XB electron affinity of the semiconductor B and EgB forbidden band width of the semiconductor B, and an electric field is applied in parallel with the layer. Further, an acceptor impurity is introduced to the semiconductor A, and a doner impurity is introduced to the semiconductor B, thereby generating an electric field vertical to the layer and accelerating the holes to flow into the layer of the semiconductor A and the electrons to flow into the layer of the semiconductor B.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for artificially obtaining the ionization coefficient ratio of electrons and holes in semiconductor devices using avalanche multiplication, such as light receiving devices and microwave oscillation devices.

Conventionally, devices using avalanche multiplication caused by impact ionization include an invat diode, an avalanche photo diode, and the like. It is known that the response speed, noise, sensitivity, and other operating characteristics of these devices depend on the ionization coefficient ratio (1/II K) of electrons and holes produced by avalanche multiplication. The substances currently known to cause sudden ionization are extremely limited to semiconductor substances such as silicon, germanicum, and gallium phosphide, and the ionization coefficient value thereof is also a value unique to the substance.

To optimize the operation of the device using the avalanche multiplication,
Although it is necessary to set the ionization coefficient ratio to a desired value,
As mentioned above, the number of substances that cause impact ionization is limited, and therefore the value of the ionization coefficient ratio that can be obtained is also limited.
Cases often arise where materials providing optimal properties are not available. For example, in an avalanche photodiode, it is known that the noise caused by the amplification effect during avalanche multiplication is minimized when the ionization coefficient ratio α is infinite or zero. However, in silicon, which has near-infrared KJll&, α〃 is less than 10, and in germanium, which has sensitivity in a longer wavelength range (1/11 is about 2 to 3), it is difficult to use avalanche photo with these materials. - Forming a diode has the disadvantage of increasing noise.

An object of the present invention is to provide a method for obtaining a collision ionization coefficient ratio using an artificially constructed material structure, unlike existing semiconductor materials having a collision ionization coefficient ratio.

A further object of the present invention is to provide a method that makes it possible to obtain impact ionization coefficient ratios that cannot be obtained with existing semiconductor materials.

In the method according to the present invention, when different semiconductors, ie semiconductor great and semiconductor B, are stacked and electrons and holes are flowed in parallel to the layers, the electrons and holes are spatially separated and are placed in different semiconductor layers. By setting the main part to move, it is possible to obtain an impact ionization coefficient ratio even for junctions of different types of semiconductors. That is, χ^ is the electron affinity of the semiconductor great, EgA is the forbidden band width of the semiconductor great, Zat-electron affinity of the semiconductor B, Ega is the semiconductor Bf) the forbidden band width j, , y
Then, ZA (ZB, Zx10EgA <”XB+B
The above object is achieved by forming at least three or more alternating layers of semiconductor A and semiconductor B that satisfy g & (1), and applying an electric field in parallel to the layers.

Furthermore, in the method according to the present invention, when an acceptor impurity is introduced into the semiconductor layer and a donor impurity is introduced into the semiconductor layer, an electric field perpendicular to the layer is generated by K, and holes are introduced into the layer of the semiconductor A, and holes are introduced into the layer of the semiconductor B. This promotes the flow of electrons into the layer. The present invention will be described in detail below.

FIG. 1 is a diagram showing the energy state when alternate layers of semiconductors and semiconductors B satisfying the above equation (1) are formed. At this time, conduction electrons and holes generated in the semiconductor layer due to light irradiation or avalanche multiplication fall into the semiconductor layer. As a result, holes and electrons are transferred to semiconductor A, respectively.
It is separated into layer B. Here, electrons and holes are accelerated parallel to the layer, that is, in the direction perpendicular to the plane of the paper in FIG. 1, to cause impact ionization. When the collision ionization coefficients α and β are respectively k(α^, β^) and (α8.βB) in semiconductor A and semi-quaternary body B, the equilibrium collision ionization coefficients of electrons and holes are Birds are effectively αB and β^. Therefore, α-^ is obtained as the ionization coefficient ratio. As described later, a6 and β^ depend on the applied electric field IK, but if the energy obtained when electrons and regular bills fall into another layer is larger than the forbidden band width Eg, then the ratio of Ki family, sea, is further strengthened in the same electric field.

, Book 81. Carr, Oiko, mentioned above. Ahep in half,
FIG. 2 shows the energy state of alternating layers formed by introducing Kerr impurities. Thus, by applying a vertical electric field to each layer, the JIiK holes in semiconductor A promote the injection of electrons into the layers of semiconductor B.

In the present invention, the combination of semiconductors 4 that satisfies the inner formula is
There are a large number of semiconductors, including A-II group semiconductors, II group semiconductors, Tol group semiconductors, and four combinations thereof. in particular,
Examples include the combination of InAs'' and Ga'8b, and the combination i of 8i and QaP. It shows the dependence on the intensity E. From this figure, it can be seen that the αInA@,,'β axes change depending on the electric field strength. For example, when the electric field strength 113
5 (Calculating αI mountain/'Garb at paste A0 is 56
It is. That is, according to the present invention, by using a structure in which InAs and Ga8b are laminated, it is possible to form a material that provides the ionization coefficient ratio determined from FIG. Figure 4 shows the electric field strength dependence of the impact ionization coefficient βSi of holes in 8i and the equilibrium impact ionization coefficient α (jaP) of electrons in Qt.From this relationship, using the combination of 8i and GaP, method, at an electric field strength of 500 (KV/c),
A substance with an impact ionization coefficient ratio a of 0.02 is obtained.

Figure 5 is an example of a method for producing an avalanche photodiode, etc. according to the present invention using CInAs and Ga8b. In the layered growth diagram, 3 indicates the nIJ region and 4 indicates the p region. All normal epitaxial growth methods such as the layered structure creation kit, [1N growth method (-IJ'g), % phase growth method (CVI)), and molecular beam growth method (2) can be used. Taking the molecular beam growth method as an example, a Ga8b or GaAs substrate is heated (500 to 6
00°C) and supplying In, (ja, As, and 8b as molecular beams onto the substrate), InAs+Ga8b
single-crystal thin films are grown in alternating layers. n area 6. p
For region 4, the sound selective diffusion method or Ion-Impl
By the antat overpass method, Kn is formed or p-type impurities are introduced only in a portion, and a p-n junction is formed in the layered crystal.

Figures (a) and (b) show a method for forming electrodes on the growth layer created by the method of the present invention. Figure 6 God) (
In b), 11.21 is the substrate, 12.22 is the growth layer, 5°1
5 is an electrode. Electrodes are formed on the walls of the mesa structure by mesa-etching the grown layer as shown in FIG. 6(a) or by mesa-etching the grown layer as shown in FIG. 6(b).

In this way, Honbi and Akira's method can be used for devices that use avalanche multiplication by impact ionization, such as Rancieffot diodes, and this results in performance improvements in response speed, noise, and sensitivity compared to conventional devices. Seiko with different characteristics can be obtained.

When an avalanche photodiode is fabricated by the method of the present invention using InAs and Garb, the multiplication noise figure is reduced, so the element noise is reduced, the minimum detectable power is reduced, and the noise is reduced to the same level. If you do this, you will be able to obtain a large multiplication factor. Furthermore, the input signal
There are advantages such as reduced distortion of the output signal and improved surface frequency characteristics. That is, the present invention improves the characteristics of an element using avalanche multiplication.

As explained above, the present invention can achieve the following effects in a device using conventional avalanche multiplication: 1) reduction of noise, 2) improvement of high-frequency wave characteristics and widening the band, and 6) improvement of the minimum detectable input signal. 4) It has effects such as higher efficiency.

[Brief explanation of drawings]

1 and 21 are diagrams each showing the energy key state in the semiconductor product 1 according to the present invention, FIGS. 6 and 4 are diagrams respectively showing the relationship between the ionization coefficient and electric field strength obtained according to the present invention, and FIG. The figure is a diagram explaining the method for creating a layered structure of the present invention, gg
Figure 6 (ml) (b) is a diagram showing a method of forming an electrode on a growth layer obtained by the method of the present invention. 1, 11.21-... Substrate 2, 12, 22... Growth layer 5 fathoms.・n area 4-・ri area 5.15...1 Applicant Hiroyuki Sakaki, Canon Co., Ltd. Su~ N r) r no)

Claims (1)

[Claims] (1) χ^ is the electron affinity of the semiconductor great, Bg^ is also the forbidden band width, χS is the electron affinity of the semiconductor B, l! If 1 is also the forbidden band width, then KA < ze, KA +gg^< z11+B
A method for obtaining an equilibrium ionization coefficient ratio by laminating at least three layers of semiconductor elements and semiconductor B that satisfy the condition gB, and applying an electric field in parallel to the layers.