JP3562841B2 - Semiconductor device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a semiconductor device in which different types of II-VI compound semiconductor films are stacked, and more particularly to a semiconductor device which solves a problem caused by a hetero interface between the two different II-VI compound semiconductor films.
[0002]
[Prior art]
II-VI compound semiconductors are promising as materials for forming light-emitting elements such as short-wavelength (blue) light-emitting diodes and laser diodes. Among the II-VI compound semiconductors, for example, a p-type zinc selenide (ZnSe) compound semiconductor film 2 is formed on the upper surface of a substrate 1 made of gallium arsenide (GaAs) so as to constitute a part of the element. However, when an electrode needs to be deposited on the p-type zinc selenide compound semiconductor film 2, as shown in FIG. 5, when gold (Au) 3 is directly deposited thereon, Is difficult to increase the carrier concentration of the zinc selenide compound semiconductor film (the maximum concentration is about 1 × 10 ¹⁷ cm ⁻³ ), the p-type zinc selenide compound semiconductor film 2 and the gold 3 Does not make ohmic contact, and the device characteristics deteriorate.
[0003]
Therefore, as shown in FIG. 6, a p-type zinc telluride (ZnTe) compound semiconductor film (maximum concentration is about 1 × 10 ¹⁸ cm ⁻³ ) 4 that is a semiconductor that can make ohmic contact with a metal electrode is converted into p-type selenide. It has been studied to form it on the upper surface of the zinc compound semiconductor film 2 and to deposit gold 3 on the upper surface of the p-type zinc telluride compound semiconductor film 4.
[0004]
[Problems to be solved by the invention]
However, in the above structure, at the hetero interface between the p-type zinc selenide compound semiconductor film 2 and the p-type zinc telluride compound semiconductor film 4, a lattice irregularity (due to a difference in lattice constant between the two, that is, a difference in crystal structure). Crystal strain) occurs, which adversely affects the crystal growth of the upper p-type zinc telluride compound semiconductor film 4, making it impossible to form a semiconductor film having a high carrier concentration. Obtaining ohmic contact becomes difficult. In addition, defects also occur in the lower p-type zinc selenide compound semiconductor film 2, which adversely affects device characteristics. Further, since a potential barrier is generated at the junction interface (heterointerface) due to band discontinuity accompanying the junction, it is difficult to improve the device characteristics from this point as well.
[0005]
What has been described above is that not only the heterointerface between the p-type zinc selenide compound semiconductor film 2 and the p-type zinc telluride compound semiconductor film 4 but also II-VI group compound semiconductors having different crystal structures are joined. This is a problem that also occurs at the hetero interface in the case.
[0006]
The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor device which has solved the above-described problems of lattice defects due to lattice irregularities and the problem of potential barrier generation due to band discontinuity. It is to be.
[0007]
[Means for Solving the Problems]
For this purpose, the present invention forms a first semiconductor film made of a group II-VI compound on an upper surface of a substrate, and forms a second semiconductor film made of a group II-VI compound with a higher carrier concentration than the first semiconductor film. In a semiconductor device having a film formed on an upper surface of the first semiconductor film, a third semiconductor film made of a group III-VI layered semiconductor is interposed between the first semiconductor film and the second semiconductor film. It was configured with intervening.
[0008]
In the present invention, it is preferable that the first and second semiconductor films are p-type.
[0009]
In the present invention, the first or second semiconductor film may include one or more elements selected from magnesium, mercury, zinc, and cadmium, and one or more elements selected from sulfur, selenium, and tellurium. It is desirable to consist of a mixed crystal compound of two or more compounds obtained by combining
[0010]
Further, in the present invention, the third semiconductor film is made of one or more elements selected from indium, gallium, and aluminum, and one or more elements selected from selenium, tellurium, and sulfur; A semiconductor film in which the number of atoms of the element and the number of atoms of the group VI element are approximately 1: 1 is desirable.
[0011]
[Action]
In the present invention, since the third semiconductor film made of a layered semiconductor is bonded by van der Waals force itself and is also bonded to the first and second semiconductor films by Van der Waals force, Crystal distortion of the first and second semiconductor films is relaxed, and lattice defects are suppressed. Further, the electric barrier caused by the band discontinuity is reduced, and the device characteristics are improved.
[0012]
【Example】
Hereinafter, examples of the present invention will be described. FIG. 1 is a diagram showing a cross section of a semiconductor device according to one embodiment. The same components as those shown in FIGS. 3 and 4 are denoted by the same reference numerals. In the present embodiment, as shown in FIG. 1, between a p-type zinc selenide compound semiconductor film 2 (first semiconductor film) and a p-type zinc telluride compound semiconductor film 4 (second semiconductor film). Is provided with a layered semiconductor film 5 (third semiconductor film). The layered semiconductor film 5 is made of gallium selenide (GaSe), has an internal structure of a layered structure, and differs from a covalent bond or an ionic bond in which an atomic bond is a normal single crystal structure. It is a connection by the Worth force.
[0013]
Therefore, the bond between the layered semiconductor film 5 and the p-type zinc selenide compound semiconductor film 2 and the bond between the p-type zinc telluride compound semiconductor film 4 are also formed by Van der Waals force. For this reason, the problem of lattice misalignment due to the difference in crystal structure between the p-type zinc selenide compound semiconductor film 2 and the p-type zinc telluride compound semiconductor film 4 is reduced, and the p-type zinc telluride compound semiconductor The adverse effect on the crystallinity of the film 4 is reduced. In addition, a potential barrier due to band discontinuity is reduced, and device characteristics are improved.
[0014]
FIG. 2 is an explanatory diagram of a method of growing the semiconductor device shown in FIG. Here, a case where a molecular beam epitaxial apparatus is used will be described. Reference numeral 11 denotes a chamber (growth chamber), 12 denotes an ultra-high vacuum evacuation pump, 13 denotes a substrate holder, 14 denotes a substrate (substrate indicated by reference numeral 1 in FIG. 1), and 15 denotes the number of constituent atoms of the material to be grown (here, Zn). , Se, Te, and Ga are used, but only two are shown in FIG. 1). Only 16 molecular beam sources are provided, 16 is a shutter of each molecular beam source 15, 17 is a high-frequency radical beam source, 18 is a high-frequency radical beam source. Is a dopant cylinder and 19 is a mass flow controller.
[0015]
The growth is performed in the following procedure.
(1). First, zinc (Zn), selenium (Se), tellurium (Te), and gallium (Ga), which are the raw materials of the compounds ZnSe, ZnTe, and GaSe, are individually charged into the molecular beam source 15.
[0016]
(2). After cleaning the substrate 14, the substrate 14 is mounted on the substrate holder 13, and the inside of the chamber 11 is evacuated to an ultrahigh vacuum (about 10 ⁻⁹ Torr) by the exhaust pump 12. Heat to obtain. During this time, the shutter 16 is entirely closed to prevent the molecular beam from reaching the substrate 14.
[0017]
(3). Next, the substrate 14 is heated to a temperature (about 600 ° C.) at which a surface oxide film (used as a protective film) of the substrate 14 can be removed, and the surface oxide film is evaporated and exhausted to clean the surface [100]. . After that, the temperature of the substrate 14 is lowered to an appropriate growth temperature. Here, the temperature is about 250 ° C.
[0018]
(4). Next, when performing doping, the dopant gas (nitrogen N ₂ ) is adjusted by the mass flow controller 19 so as to obtain an appropriate flow rate from the dopant cylinder 18 and is introduced into the high-frequency radical beam source 17. Then, a radical beam is irradiated with an appropriate output (about 300 W).
[0019]
(5). Thereafter, the shutter 16 is sequentially opened and closed to perform growth so as to obtain the growth structure shown in FIG. Here, the shutter 16 of the molecular beam source 15 of Zn and Se is simultaneously opened to grow a ZnSe film. Here, since nitrogen is doped, a radical beam of nitrogen is irradiated from the radical beam source 17. After a lapse of time to obtain a required film thickness, the opened shutter 16 is closed.
[0020]
(6). Next, the shutter 16 of the molecular beam source 15 of Ga and Se is simultaneously opened to grow a GaSe film. Here, since no doping is performed, the radical beam is not irradiated from the radical beam source 17. After a lapse of time to obtain a required film thickness, the opened shutter 16 is closed.
[0021]
(7). Finally, the shutter 16 of the Zn and Te molecular beam source 15 is simultaneously opened to grow a ZnTe film. Here, since nitrogen is also doped, the radical beam is irradiated from the radical beam source 17. After a lapse of time to obtain a required film thickness, the opened shutter 16 is closed.
[0022]
The results of X-ray diffraction of the material grown according to the above-described example showed better crystallinity than that of the material grown according to the prior art, as shown in FIG. According to the present embodiment, the strength is sharper. Also in the IV (current-voltage) characteristic measurement, as shown in FIG. 4, the one according to the present embodiment has a lower rising voltage and a smaller loss.
[0023]
In the above embodiment, the substrates 1 and 14 are not limited to GaAs, but may be a ZnSe substrate, a substrate having a lattice constant close thereto, or the like.
[0024]
Further, the layered semiconductor film 5 (third semiconductor film) is not limited to GaSe, but includes a group III atom and a VI group (chalcogen) atom in a ratio of approximately 1: 1. Anything that is acceptable. For example, one or more selected from selenium (Se), sulfur (S), tellurium (Te) and the like which are group VI atoms, and indium (In) and gallium (Ga) which are group III atoms. One or more selected from aluminum (Al) may be a layered semiconductor film in which the ratio of the number of Group III atoms is 1 and the ratio of the number of Group VI atoms is also 1.
[0025]
Further, the II-VI compound semiconductor films (first and second semiconductor films) grown on the upper surface of the substrate are not limited to ZnSe and ZnTe. One or more elements selected from the group II elements magnesium (Mg), mercury (Hg), zinc (Zn) and cadmium (Cd), and the group VI elements sulfur (S), selenium (Se), tellurium ( The present invention can be applied to a binary mixed crystal obtained by combining one or two or more selected from Te) or a ternary mixed crystal such as ZnSSe (ternary mixed crystal) or ZnCdSSe (quaternary mixed crystal). However, the II-VI compound semiconductor film (second semiconductor film) constituting the upper layer of the layered semiconductor film (third semiconductor film) needs to be a compound semiconductor such as ZnTe which can increase the carrier concentration. is there. When Te is contained, the carrier concentration can be increased.
[0026]
The growth method for implementing the present invention is not limited to the molecular beam epitaxy (MBE) method, but can be applied to a vapor phase epitaxy (VPE) method and a liquid phase epitaxy (LPE) method.
[0027]
【The invention's effect】
As described above, according to the present invention, the third semiconductor film made of a layered semiconductor is formed on the first semiconductor film made of a II-VI compound semiconductor having a low carrier concentration formed on a substrate, and the II-VI having a high carrier concentration is formed on the first semiconductor film. Since the second semiconductor film made of a group III compound semiconductor is sequentially formed, the interface between the third semiconductor film and the first and second semiconductor films is coupled by van der Waals force, and lattice defects and band defects are generated. There is an advantage that deterioration of device characteristics due to continuation can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a structure of a semiconductor device according to one embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating a schematic configuration of a manufacturing device of the semiconductor device illustrated in FIG. 2;
FIG. 3 is an X-ray diffraction characteristic diagram of a material according to the present embodiment and a conventional material.
FIG. 4 is an IV characteristic diagram of a material according to the present embodiment and a conventional material.
FIG. 5 is a cross-sectional view showing a structure of a semiconductor device in which an electrode is attached to a p-type ZnSe compound semiconductor film.
FIG. 6 is a cross-sectional view illustrating a structure of a semiconductor device in which an electrode is attached to a p-type ZnSe compound semiconductor film via a p-type ZnTe compound semiconductor film.
[Explanation of symbols]
1: substrate, 2: p-type zinc selenide compound semiconductor film (first semiconductor film), 3: p-type zinc telluride compound semiconductor film (second semiconductor film), 4: electrode metal, 5: GaSe Layered semiconductor film (third semiconductor film),
11: chamber, 12: exhaust pump, 13: substrate holder, 14: substrate, 15: molecular beam source, 16: shutter, 17: high-frequency radical beam source, 18: dopant cylinder, 19: mass flow controller.

Claims (4)

A first semiconductor film made of a II-VI compound is formed on the upper surface of the substrate, and a second semiconductor film made of a II-VI compound and having a higher carrier concentration than the first semiconductor film is replaced with the first semiconductor film. In the semiconductor device formed on the upper surface of the film,
A semiconductor device, wherein a third semiconductor film made of a group III-VI layered semiconductor is interposed between the first semiconductor film and the second semiconductor film. 2. The semiconductor device according to claim 1, wherein said first and second semiconductor films are p-type. The first or second semiconductor film is obtained by combining one or more elements selected from magnesium, mercury, zinc, and cadmium with one or more elements selected from sulfur, selenium, and tellurium; The semiconductor device according to claim 1, wherein the semiconductor device is made of a mixed crystal compound of at least the original. The third semiconductor film is made of one or more elements selected from indium, gallium, and aluminum, and one or more elements selected from selenium, tellurium, and sulfur. 4. The semiconductor device according to claim 1, wherein the semiconductor film is a semiconductor film in which the number of atoms of a group VI element is approximately 1: 1.

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