JPH0419912A - Transparent conductive film - Google Patents

Abstract

PURPOSE:To make corrosion resistance higher by producing transparent conductive film having a band gap of 3eV or more, in a compound semiconductor made from at least one element respectively selected out of the III group elements of the periodic table and the V group elements of the periodic table. CONSTITUTION:Transparent conductive film having a band gap of 3eV or more is produced in a compound semiconductor made from at least one element selected out of the III group element of the periodic table and at least one element selected out of the V group elements of the periodic table. As the III group elements of the periodic table, B, Al, Ga and In are available. And as the V group elements of the periodic table N, P and As are available. Compound semiconductor of GaN and the like, and mixed crystal of GaAlN, GaBN, GaInN, GaAlInN and the like are available as the examples of compound semiconductor made from these elements. And further some of these are doped with Mg, Zn, Cd, Be, Li, Na, SiO, F and the like to control resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transparent conductive film with excellent corrosion resistance, which is particularly suitable as an electrode for solar cells, liquid crystal displays, and EL displays.

[Prior Art] Transparent conductive films that are transparent and conductive in the visible light region are generally used as transparent electrodes in amorphous silicon solar cells, liquid crystal displays, and EL displays, or as antistatic films for various purposes. ing. As materials for these transparent conductive films, A u [Ph
1los.

Hag, Ser, 7.46.381 (1955)
] Ag N, 0ptSoc, AL+ 40.2
03 (1950)], In 20
x [Jpn, J, ^pp1. Phys, 8.
681 (1969) Ko Sn O2[Va
Cuum, 3. 375 (1953)] Z n O
[Can, J. Phys., 60.1387 (1
There are oxide semiconductor thin films such as 982), but currently 1n
A transparent conductive film called ITO, which is made by adding Sn to 20z, is widely used.

ITCI is a conductive film that is transparent in the visible range and has a band gap of about 4 eV, and has a resistivity of about 10→Ω(1), but it still has problems in corrosion resistance.

Although ITO films have excellent properties in terms of transparency and conductivity, they are extremely susceptible to oxidation and reduction, and
Easily etched with acids, etc. For example, if an ITO film formed by vapor deposition on a glass substrate is immersed in concentrated hydrochloric acid, it will dissolve in a few seconds.

Furthermore, since In203, which is the main component of the ITO film, has a weak bond between indium and oxygen, if it is exposed to an atmosphere containing hydrogen at high temperatures, oxygen will be liberated, indium will precipitate, and transparency will be lost. This becomes a big problem when using an ITO film as an electrode for an amorphous silicon solar cell because a plasma CVD method using hydrogen plasma is often used to form the amorphous silicon film.

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems, the present invention aims to provide a transparent conductive film with excellent corrosion resistance in place of the ITO film.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and is composed of at least one element selected from group I elements of the periodic table.
The present invention provides a transparent conductive film having a band gap of 3 eV or more in a compound semiconductor composed of at least one element selected from a group V element of the periodic table and a group V element of the periodic table.

The present invention will be explained in more detail below.

In the present invention, as the periodic table group I element, s SA
I, Ga SI n, and at least one element among these is included.

Furthermore, examples of Group I elements of the periodic table include N, P, and As, and at least one element among these is included.

Examples of compound semiconductors made of these compounds include compound semiconductors such as GaN, GaA IN, and Ga BN.

There are mixed crystal compound semiconductors such as GaInN and GaA 11 nN, and these include ~Ig, Zn, Cd, Be, L
There is also one in which the resistivity is controlled by doping with i, Na, Si% 0% F, etc.

As the material used to form these films, for example, an elemental metal, a hydride, or a halide can be used.

As the film forming method, commonly used methods can be used, such as vacuum evaporation method, MBE method, CVD method, M
There are OCVD methods, reactive evaporation methods, ion beam evaporation methods, and sputtering methods.

The transparent conductive film of the present invention has a band gap of 3 eV or more, and has a visible range (light wavelength of 400 to 800 nm).
It is characterized by having a transmittance of 70% or more. Furthermore, it is possible to make the band gap large, and it is possible to provide transparency in the ultraviolet region.

Regarding conductivity, it is necessary that the resistivity is 10 -2 Ωcm or less, but this can be controlled by manipulating the film forming conditions and the amount of doping. For example, GaN
In this case, it is possible to raise the substrate temperature, increase the number of nitrogen defects, increase the carrier density, and lower the resistivity.

These transparent conductive films have excellent corrosion resistance, especially in nitride films.

In addition, the thickness of such a transparent conductive film is determined by the required resistance value,
Although it can be determined by optical characteristics,
It is usually about 500 to 2 μm.

Sapphire, quartz, Z
There are nS, ZnO1Si, SiC, etc.

Next, an example of a film forming method will be described, but the method is not particularly limited thereto.

The apparatus is equipped with an evaporation crucible (Knudsen cell) 2, an electron beam evaporation device 3, a cranking gas cell 5, and a substrate heating holder 6 in a vacuum container 1 as shown in FIG.
Use IBE equipment.

Ga metal is put in the evaporation crucible 2 and heated to 900 to 1000°C.
Heat to.

The cracking gas cell 4 is installed so as to spray the gas onto the substrate 7. Introduced gas includes NH3, N2 H4
The introduction m is 1-50cc/rIin. The degree of vacuum in the vacuum container is 1 to 5 x 10' T during film formation.
It will be about orr.

Using a sapphire single crystal substrate etc. for the substrate, 600~1
A GaN film is formed without heating to 000°C.

After film formation, the substrate temperature is lowered while introducing NH3. In the manner described above, a transparent GaN film can be obtained.

[Example code] The present invention will be explained in more detail with reference to Examples below.

Example 1 An MBE apparatus as shown in FIG. 1 was used as the apparatus.

Ga metal was placed in the evaporation crucible 2 and heated to 940°C. The cracking gas cell 4 was installed so that the gas outlet sprayed onto the substrate 7. NH3 is used as the introduced gas,
The amount introduced was 3ec/1Tlin. Moreover, this gas cell is capable of heating gas in the presence of a catalyst, and the gas was heated to about 300° C. while it was in contact with alumina. A sapphire single crystal substrate (1102) plane is used as the substrate.65
Heated to 0°C.

The degree of vacuum in the vacuum container is 1 to 5 x 10' To
It was about rr.

Under these experimental conditions, one-time open film formation was performed to obtain a GaN film with a film thickness of 150 OA. This film had a transmittance of 80% or more in the visible range (light wavelengths of 400 to 800 r+m) and a resistivity of 10-3 Ωσ. The bandgap size obtained from the spectroscopic results was about 3.2 eV. Further, this film was left in aqua regia for 1 hour and was not eroded at all. Further, an amorphous Si film was formed on this film by plasma CVD, but no deterioration of the GaN film was observed.

Example 2 An MBE apparatus similar to that of Example 1 as shown in FIG. 1 was used.

Ga metal was placed in the evaporation crucible 2 and heated to 940'C. Put A1 metal into the crucible of the electron beam evaporation device 3,
The output of the electron beam was adjusted so that the atomic ratio of the A1 metal in the thin film was about one-tenth that of the Ga metal, and the film was heated and evaporated.

Hereinafter, a film was formed under the same conditions as in Example 1 except that the substrate heating temperature was 1000°C.
An AIN film was obtained. According to compositional analysis using atomic absorption spectrometry,
The atomic ratio of A1 was about 10% of Ga. In the visible range (light wavelength 400-800r+m), this film has a
% or more, and the resistivity was 10-2Ω. The bandgap size obtained from the spectroscopy results is 3.6
There was eV. Also, this membrane was left in aqua regia for 1 hour,
It wasn't eroded at all.

Example 3 An MBE apparatus similar to that of Example 1 as shown in FIG. 1 was used.

Ga metal was placed in the evaporation crucible 2 and heated to 940°C. Put Mg metal in the other side of evaporation crucible 2,
Heated to 0°C.

Thereafter, film formation was performed under the same conditions as in Example 1 at the same time to obtain a GaN film doped with Mg having a thickness of about 1500 nm.

This film had a transmittance of 80% or more in the visible range (light wavelength of 400 to 800 nm), and a resistivity of 10°1Ω mark. This confirmed that the conductivity could be controlled. The size of the band gap obtained from the spectroscopy results is
It was about 3.2 eV. Further, this film was left in aqua regia for 1 hour and was not eroded at all.

Example 4 An MBE apparatus similar to that of Example 1 as shown in FIG. 1 was used.

Ga metal was placed in the evaporation crucible 2 and heated to 940°C. In the other side of the evaporation crucible 2, put In metal,
heated to ℃.

The following is Example 1 except that the heating temperature of the substrate was 700°C.
An open film was formed under the same conditions and at the same time, and the film thickness was 150OA.
A Ga1nN film was obtained. According to the composition analysis by atomic absorption method, the atomic ratio of In was about 5% of Ga. In the visible range (wavelength of light 400~g (lonm)), this film
It had a pass rate of 7096 or more and a resistivity of 104Ω. The size of the band gap obtained from the spectroscopy results is
Approximately 3. It was Oe■. Further, this membrane was left in aqua regia for 1 hour, but no corrosion occurred.

Example 5 An MBE apparatus similar to that of Example 1 as shown in FIG. 1 was used.

Ga metal was placed in the evaporation crucible 2 and heated to 940°C. The cracking gas cell 4 was installed so that the gas outlet sprayed onto the substrate 7. N2 H4 was used as the introduced gas, and the amount introduced was 3 cc/11 inch. Moreover, this gas cell is capable of heating gas in the presence of a catalyst, and the gas was heated to about 300° C. while it was in contact with alumina. The gas cell 5 was configured to spray a gas onto the substrate 7 through its outlet. PCl3 is used as the introduced gas, and the amount introduced is ice/l1i.
It was set as n. The substrate is a sapphire single crystal substrate (1102)
A surface was used and heated to 650°C.

The degree of vacuum in the vacuum container is 1 to 5 x 10' Torr during film formation.
It was about r.

Under these experimental conditions, one-time open film formation was performed to obtain a GaPN film with a film thickness of 1500 Å. This film had a transmittance of 80% or more in the visible range (light wavelengths of 400 to 800 r+m), and a resistivity of 10 -3 Ω. The size of the band gap obtained from the spectroscopy results is approximately 3.0
It was eV. Further, this membrane was left in aqua regia for 1 hour, but no corrosion occurred.

Example 6 A CVD apparatus as shown in FIG. 2 was used, which was equipped with a boat 9 containing Ga metal in a quartz tube 8, a basic holder 10, and gas introduction nozzles 11 and 12.

The quartz tube 8 is heated by a tubular furnace and the boat 9 is 900 yen.
℃, and the basic holder 10 was adjusted to 10 DO'C. A sapphire single crystal substrate (1102) plane was used as the substrate.

HCI gas was flowed through the gas introduction nozzle 11 at a rate of 5 cc/min so that the gas could come into contact with the gallium metal. NH3 gas was flowed through the gas introduction nozzle 12 at a rate of 200 cc/min, and was mixed with GaCl gas above the substrate 7.

In addition to this, N2 gas was flowed through the quartz tube 8 at 1000 cc/min as a carrier gas.

Under these experimental conditions, one-time open film formation was performed to obtain a GaN film with a thickness of approximately 20 μm. This film had a transmittance of 70% or more in the visible range (light wavelength of 400 to 800 nm), and a resistivity of 10-3Ω. The bandgap size obtained from the spectroscopic results was about 3.2 eV. Further, this film was left in aqua regia for 1 hour and was not eroded at all.

Example 7 A vacuum evaporation apparatus as shown in FIG. 3 was used, which was equipped with an evaporation crucible 2, a plasma source 13, and a substrate heating boulder B in a vacuum container 1.

Ga metal was placed in the evaporation crucible 2 and heated to 940°C.

The plasma source 13 was installed so that the plasma gas outlet sprayed onto the substrate 7. N2 was used as the introduced gas, and the amount introduced was 5 cc/min. Further, this plasma source is capable of plasma heating the gas using high frequency waves.

A sapphire single crystal substrate (1102) plane was used as the substrate and heated to 650°C.

The degree of vacuum in the vacuum container is 1 to 5 x 10'To during film formation.
It was about rr.

Under these experimental conditions, one-time open film formation was performed to obtain a GaN film with a thickness of approximately 1,500 yen. This film had a transmittance of 8096 or more in the visible range (light wavelengths of 400 to 800 nm) and a resistivity of 10 -3 Ω. The bandgap size obtained from the spectroscopic results was about 3.2 eV. Further, this film was left in aqua regia for 1 hour, but was not corroded at all.

Example 8 An ion beam evaporation apparatus as shown in FIG. 4 was used, which was equipped with an evaporation crucible 2, an ion beam gun J4, and a substrate heating holder 6 in a vacuum vessel l.

Ga metal was placed in the evaporation crucible 2 and heated to 940°C. The ion beam gun 14 had its beam exit facing toward the substrate 7. N ions are used as the ion beam, and the beam current and acceleration voltage are approximately 1+nA, respectively.
50 [IV. Further, this ion beam gun is designed to obtain N ions using DC arc discharge plasma. A sapphire single crystal substrate (1102) was used as the substrate, heated to 600°C @ The degree of vacuum in the vacuum chamber was 1 to 5 x 10' T during film formation.
It was about orr.

Under these experimental conditions, one-time open film formation was performed to obtain a GaN film with a film thickness of 15,002 mm. This film had a transmittance of 8096 or more in the visible range (light wavelengths of 400 to 800 nm) and a resistivity of 10 -3 Ω. The width of the band gap obtained from the spectroscopic results was about 3.2 eV. Further, this film was left in aqua regia for 1 hour, but was not corroded at all.

[Effects of the Invention] As described above, the transparent conductive film of the present invention has excellent corrosion resistance and is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the MBE apparatus used in Examples 1 to 5, and FIGS. 2 to 4 are explanatory diagrams of the apparatus used in Examples 6 to 8, respectively. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... Evaporation crucible, 3... Electron beam evaporation device, 4... Cracking gas cell, 5... Gas cell, 6
... Substrate heating holder 7 ... Substrate, butt ... Quartz tube, 9 ... Boat, 10 ... Substrate holder 11.12
...Gas introduction nozzle, 13...Plasma source, 14.
...Ion beam gun. Figure ＼ Figure

Claims (1)

[Claims] A compound semiconductor consisting of at least one element selected from group III elements of the periodic table and at least one element selected from group V elements of the periodic table, with a band gap of 3e.
A transparent conductive film having V or more.