JPH04352365A - Semiconductor electron-emitting element - Google Patents

Abstract

PURPOSE:To provide a semiconductor electron-emitting element whose emission current density is high by using a diamond semiconductor layer provided with a crystal orientation property. CONSTITUTION:A C-axis orientation-property graphite layer (not shown in the figure) having a thickness of 2nm or higher is formed on a p<+> semiconductor element 101 by using an ion beam apparatus; in addition, a p-type diamond layer 102 having a thickness of 1mum is formed on it by a thermal filament CVD method. An n-type diamond layer 104 as an electron avalanche-inducing layer is formed on the p-type diamond layer 102; a p-n junction between the p-type diamond layer 102 and the n-type diamond layer 104 is reverse-biased (voltage: Vb). Thereby, an avalanche amplification is induced and electrons (e) are emitted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor electron-emitting device using a diamond semiconductor layer.

0002

[Prior Art] Conventionally, among semiconductor electron-emitting devices, those using avalanche amplification are
There are elements in which a junction is formed between a type semiconductor and an n-type semiconductor (pn junction type element), and an element in which a Schottky junction is formed between a semiconductor layer and a metal or a metal compound (Schottky junction type element).

As a pn junction type semiconductor electron emitting device using the above avalanche amplification, for example, US Pat.
59678 and US Pat. No. 4,303,930 are known.

This semiconductor electron-emitting device has a p-type semiconductor layer and an n-type semiconductor layer formed on a semiconductor substrate, and a metal such as cesium is further attached to the surface of the n-type semiconductor layer to form an electron-emitting region. A reverse bias voltage is applied to a diode formed by a p-type semiconductor layer and an n-type semiconductor layer to cause avalanche amplification, thereby making the electrons hot and emitting the electrons from the electron emitting section.

Further, as a Schottky junction type semiconductor electron-emitting device using the above-mentioned avalanche amplification, for example, a junction is formed between a p-type semiconductor layer and a metal electrode, and a reverse bias voltage is applied to this junction to perform avalanche amplification. There are some that heat up the electrons by causing them to emit electrons from the electron emitting part.

By the way, in order to obtain a large amount of electron emission current when emitting electrons from a semiconductor electron emitting device using avalanche amplification as in the conventional example, a very large amount of current must be applied to the device. Normally, when emitting electrons from a pn junction as described above, a current density of 10,000 amperes or more is required.

[0007] In conventional semiconductor electron-emitting devices, when a large current as described above is passed through the device, the device generates heat, which destabilizes the electron-emitting characteristics of the device and shortens the life of the device. .

[0008] Therefore, an electron-emitting device that generates little local heat generation has been desired.

[0009] Furthermore, in the prior art example of the pn junction type described above, a material with a low work function is used in order to lower the work function of the electron emitting portion and suppress the reverse bias voltage. Conventionally, materials such as cesium have been used as low work function materials in order to emit electrons without increasing the reverse bias voltage too much, but since low work function materials such as cesium are chemically active, It was difficult to expect stable operation due to the effects of local heat generation in the semiconductor layer. For this reason, there has been a desire for an electron-emitting device that can also use relatively stable materials as work function-lowering materials.

Further, in the case of a conventional Schottky junction type electron-emitting device, a material that can form a Schottky junction and has a low work function is desired as the electrode material. However, in conventional Schottky junction type electron-emitting devices, the selection range of electrode materials is narrow due to the tendency of electrode materials to migrate due to local heating of the semiconductor layer and the large energy band gap of semiconductors. The problem was that it was difficult to select materials to improve the stability of the materials. Furthermore, when a layer of cesium or cesium oxide is formed on the surface of the electron emitting section in order to lower the work function of the electron emitting section, problems similar to those of the above-mentioned pn junction type conventional example occur. Therefore, there has been a desire for an electron-emitting device that generates less localized heat and allows a wider selection of materials for the Schottky electrode.

[0011] From the above points of view, an electron-emitting device using a diamond semiconductor layer is expected. The diamond semiconductor layer has the highest thermal conductivity among substances at room temperature, has a wide band gap (5.4 eV), has strong heat resistance, and has a wide range of material selection for Schottky electrodes.

0012

[Problems to be Solved by the Invention] However, in the conventional semiconductor electron-emitting device described above, it is necessary to use an epitaxially grown diamond film or a diamond film with controlled orientation in order to improve the emission current density. By scratching using diamond abrasive grains, etc.
A problem with techniques that increase nucleation is that it is difficult to control crystal orientation.

The present invention was made in view of the problems of the conventional techniques described above, and an object thereof is to provide a semiconductor electron-emitting device having a high emission current density by using a diamond semiconductor layer having crystal orientation. shall be.

[0014]

[Means for Solving the Problems] In a semiconductor electron-emitting device using a diamond semiconductor layer of the present invention, a C-axis oriented graphite layer with a thickness of 2 nm or more and a diamond semiconductor layer having crystal orientation are provided on a substrate. are formed in sequence.

[0015] Furthermore, in the semiconductor electron-emitting device,
The diamond semiconductor layer having crystal orientation is a p-type layer, and an n-type semiconductor layer having a smaller energy gap than the diamond semiconductor layer is formed on the p-type layer.
One is an n-junction type, the n-type semiconductor layer is a diamond layer, and the diamond semiconductor layer having crystal orientation is a p-type layer, and a Schottky electrode layer is formed on the p-type layer. Some are Schottky junction types.

[0016]

[Function] The function of the present invention will be explained below together with the findings obtained in making the present invention.

As a result of intensive studies on substrate pretreatment methods, the inventors of the present invention found that by forming a C-axis oriented graphite layer on a substrate, a graphite layer with high nucleation density and good smoothness can be obtained.
111} plane-oriented diamond crystals were found to be formed.

The C-axis oriented graphite layer of the present invention has crystallinity and does not include an amorphous carbon layer. Amorphous carbon, under a diamond-forming atmosphere,
It easily scatters and is not useful for diamond formation. On the other hand, graphite having crystallinity has a certain degree of stability in a diamond-forming atmosphere and has a function of supporting diamond formation.

Although the formation of C-axis oriented graphite on the substrate used in the present invention is not particularly limited, for example, in a gas atmosphere mainly composed of hydrocarbons such as CH4,
The substrate is heated to 1200°C or higher under atmospheric pressure, or CH
4 etc. hydrocarbon gas or carbon hydrogen gas and H2, H
There is a method in which a diluent gas such as e, Ar, etc. is made into a plasma state and sprayed onto a substrate heated to 700° C. or higher.

On the C-axis oriented graphite formed by these methods, {
111} plane-oriented diamond crystals are formed. By using the {111} plane-oriented diamond semiconductor layer as described above, a semiconductor electron-emitting device with a high emission current density can be obtained.

The semiconductor electron-emitting device used in the present invention has negative electron affinity (Negative Electron A).
Any type of method may be used, such as one using a high-density chromatography (Ffinity) or one using electron avalanche amplification.

Here, an example using avalanche amplification will be explained.

FIGS. 3A and 3B are energy band diagrams of a pn junction type semiconductor electron-emitting device in which the electron avalanche inducing layer is an n-type semiconductor layer. In the figure, p indicates a p-type semiconductor layer, n indicates an n-type semiconductor layer, and T indicates a layer of a low work function material.

Note that p-type and n-type semiconductors in the present invention also refer to so-called p+ and n+ semiconductors containing impurities at a high concentration, unless otherwise specified.

FIG. 3A shows a pn junction between a p-type diamond layer and an n-type diamond layer.

As shown in FIG. 3(a), a reverse bias (
voltage Vb), the vacuum rank Evac is changed to p
The energy level can be lower than the conduction band Ec of the type semiconductor layer, and a large energy difference ΔE (=EC −E
vac) can be obtained.

By causing avalanche amplification in this state, it becomes possible to generate a large number of electrons, which were minority carriers in the p-type diamond layer, thereby increasing the electron emission efficiency. In addition, since the electric field within the depletion layer gives energy to the electrons, the electrons become hot and their kinetic energy increases, causing energy loss due to scattering of electrons with potential energy greater than the work function φWK of the surface of the n-type diamond layer. It is possible to jump out from the surface without any

FIG. 3(b) shows a p-type diamond layer (energy gap Eg1) and an n-type semiconductor layer (energy gap Eg2) having a smaller band gap than diamond.
) shows an energy band diagram when a heterojunction is used.

In such an electron-emitting device using pn junction type avalanche amplification, heat generation can be further reduced by lowering the resistance value of the n-type semiconductor.

Generally, in the case of a material with a large band gap such as diamond, the effective density of states in the conduction band is small, so the resistivity of the semiconductor is reduced to 10-4 Ω like Si or Ge.
・It is difficult to lower it to about cm. Therefore, by forming an n-type semiconductor layer with a smaller band gap than the p-type diamond layer on the p-type diamond layer to lower the resistance of the n-type semiconductor layer, it is possible to further reduce heat generation. A highly stable electron-emitting device can be obtained.

Furthermore, since a diamond layer is used as the p-type semiconductor layer, the band gap Eg of diamond is
1 is wide, a large energy difference ΔE can be obtained with a small reverse bias potential. For this reason, as in the past,
There is no need to intentionally form a layer of a chemically unstable low work function material such as cesium on the surface of the n-type semiconductor layer, and a layer of a chemically stable material with a relatively high work function can be formed. . Diamond energy band gap E
Since g1 is 5.4 eV and the activation energy of a p-type semiconductor is 0.37 eV when boron is used as an impurity,
Work function φWK of the material layer formed on the surface of the n-type semiconductor layer
is 5.0 eV or less, application of a relatively low reverse bias voltage Vb satisfies ΔE>0, and electron emission becomes possible.

Next, a Schottky junction type electron emitting device in which the electron avalanche inducing layer is a Schottky electrode will be described with reference to FIG.

FIG. 4 is an energy band diagram of a Schottky junction type electron-emitting device in which the electron avalanche inducing layer is a Schottky electrode. In the figure, p indicates a p-type semiconductor layer, and T indicates a Schottky electrode.

As shown in FIG. 4, a reverse bias (voltage Vb) is applied between the junction between the p-type semiconductor layer and the thin film Schottky electrode.
By doing so, the vacuum level EVAC can be set to an energy level lower than the conduction band level EC of the p-type semiconductor layer, and the energy difference ΔE (=EC - Evac) becomes large, making it possible to emit electrons.

By causing avalanche amplification in this state, it becomes possible to generate a large number of electrons, which were minority carriers, in the p-type semiconductor layer, thereby increasing the electron emission efficiency. In addition, since the electric field within the depletion layer gives energy to the electrons, the electrons become hot and their kinetic energy becomes greater than the temperature of the lattice system, and electrons with a potential greater than the surface work function lose energy due to scattering. It becomes possible to cause electron emission to occur without accompanying.

When diamond is used for the p-type layer, due to its large band gap, a good Schottky junction can be formed by constructing the electrode from a material with a wide work function range, and the work function of the electrode material can have a very wide tolerance range. Furthermore, since the Schottky electrode material can be selected from materials with a wide range of work functions, a Schottky junction that can stably emit electrons can be formed.

The material of the Schottky electrode used in the Schottky junction type semiconductor electron-emitting device of the present invention clearly exhibits Schottky characteristics with respect to the p-type diamond layer. In general, a linear relationship exists between the work function φWK and the Schottky barrier height φBn for an n-type semiconductor (Physics of Semi
conductorDevicesSze' 27
4p 76(b) JOHN WILEY & SON
S), as the work function φWK becomes smaller, the Schottky barrier height φBn decreases. In general, the Schottky barrier height φBp for a p-type semiconductor and the Schottky barrier height φBn for an n-type semiconductor have a relationship of approximately φBp+φBn=Eg/q (q is charge). The key barrier height φBp is φBp=Eg/q−φBn. As mentioned above, by using materials with small work functions,
A good Schottky diode can be configured for the p-type semiconductor layer.

[0038]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

(Example 1) In this example, a pn junction type electron-emitting device using avalanche amplification in which the electron avalanche inducing layer is an n-type semiconductor layer will be explained with reference to FIGS. 1(a) and (b). do.

FIG. 1(a) is a plan view of the pn junction type electron-emitting device of this embodiment, and FIG. 1(b) is a cross-sectional view taken along the line A--A.

In the figure, 101 is a p+ type semiconductor substrate, and in this example Si (100) was used. 102
is a p-type diamond layer. 103 is a mask for insulating selective deposition, and here a SiO2 layer is used. 10
4 is an n-type diamond layer which is an electron avalanche inducing layer, 105 is an ohmic contact electrode made of titanium (Ti), 106 is an insulating layer, and 107 is an extraction electrode. 108 is the p+ type semiconductor substrate 1
This is an ohmic contact electrode made of Al vapor-deposited on the back surface of 01. 109 is a power supply for applying a reverse bias voltage Vb between the ohmic contact electrode 105 and the ohmic contact electrode 108;
0 is a power source for applying an extraction voltage Vg between the electrode 105 and the extraction electrode 107. 111 is Ag as a material that lowers the work function (work function: 4.26
eV) work function lowering material layer.

The above device was manufactured by the following method. (1) First, a graphite layer (not shown) was formed on the p+ type semiconductor substrate 101 using an ion beam apparatus as shown in FIG.

The method for forming the graphite layer will now be explained.

In the ion beam apparatus shown in FIG.
01 is a vacuum chamber, 502 is an ion beam source, and 503 is a gas inlet to which a gas cylinder and a gas flow rate regulator (not shown) are connected. Reference numeral 504 is an exhaust port that can be connected to a turbo-molecular pump and a rotary pump (not shown) to exhaust air up to 10-6 Torr. 505 is an ion beam, 506 is a substrate heating holder, and 100 is a power supply and temperature controller (not shown).
It can be heated up to 0°C. 507 is a base body such as the p+ type semiconductor substrate 101 or the like.

For forming the C-axis oriented graphite layer, for example, the vacuum chamber 501 is heated to 5×10 −6 Torr using an exhaust device.
After evacuation to r, the base 507 is heated to 700° C., and methane gas is supplied to the ion beam source 502 at 5
The methane ion beam is introduced at a pressure of r, and ionization is performed by irradiating the substrate 507 with a methane ion beam at an acceleration voltage of 5 kV and a beam current density of 0.5 mA/cm2. Under these conditions, a C-axis oriented graphite layer of about 2000 Å is formed after 10 minutes of irradiation.

In the case of this example, the formation conditions are as follows: substrate temperature 7
50℃, pressure 4 x 10-4 Torr, methane gas 50S
By introducing CCM, acceleration voltage is 2kV and current density is 0.6mA/c.
As m2, a C-axis oriented graphite layer of about 500 Å was formed by film formation for 2 minutes. (2) Next, a 1 μm thick p-type diamond layer 102 was formed by hot filament CVD. The formation conditions were: substrate temperature 1000°C, pressure 100 Torr, gas flow rate: 2
00SCCM, CH4:1SCCM, 100ppm
B2 H6 (hydrogen dilution): 1 SCCM, filament temperature: 2100°C.

The diamond crystal formed in this example was
When the orientation was measured by line diffraction method, it was found that {111
}It was found that the crystal had plane orientation. (3) Next, an insulating selective deposition mask 103 of SiO2 was formed at a predetermined position by a photolithography resist process. (4) Next, an n-type diamond layer 104 was formed by hot filament CVD. The formation conditions were as follows: gas flow rate: H2: 200SCCM, CH4: 1SCCM, 100
ppm pH3 (hydrogen dilution): Same as above (2) except that it was 5SCCM.

The n-type diamond layer 104 is not deposited on the insulating selective deposition mask 103, but is selectively deposited only in the opening of the insulating selective deposition mask 103 (the exposed part of the p-type diamond layer 102). did. (5) Next, the ohmic contact electrode 105 and the work function lowering material layer (1
00 Å thick) 111, the SiO2 insulating layer 106, and the polysilicon lead electrode 107 were all formed into predetermined shapes.

When a reverse bias voltage Vb is applied between the ohmic contact electrodes 105 and 108 of the semiconductor electron-emitting device manufactured as described above, electrons are injected from the p-type diamond layer 102 to the n-type diamond layer 104. The electrons pass through the n-type diamond layer 104 and the work function lowering material layer 111 and leak out into the vacuum region, and then the extraction electrode 107 and the ohmic contact electrode 10.
By applying an extraction voltage Vg between 5 and 5, electrons e- could be emitted to the outside of the device.

The emission current density at this time was approximately five times greater than that of the device in which a diamond layer was formed in the same manner as in the above example without forming a C-axis oriented graphite layer.

(Examples 2 to 8) Next, semiconductor electron-emitting devices were formed by changing the substrate temperature or the graphite layer thickness during the formation of the graphite layer by the same process as in Example 1 (Example 2). ~8), and its emission current density was measured. Table 1 shows a comparison between the graphite layer forming conditions at this time and the emission current density of an element in which no graphite layer was formed.

◎: Very good orientation ○: Good orientation △: Oriented ×: No orientation *: Emission current density ratio for the device in which a diamond layer was formed without forming a graphite layer It is also clear from Table 1 As shown above, in the case of Examples 2 to 4 in which a graphite layer of a certain length (100 nm) was formed at a graphite layer forming temperature of 700°C or higher, the graphite layer was formed at a graphite layer forming temperature (650°C) lower than 700°C. Compared to Comparative Example 1, in which a film was formed, a better emission current density could be obtained in each case. In addition, Example 5 in which the graphite layer forming temperature was kept constant (800°C) and the thickness of the graphite layer to be formed was varied between 2 nm and 1 μm.
In the case of ~8, a very good C-axis orientation of the graphite layer could be obtained, and the electron emission density could also be sufficiently improved. On the other hand, in the case of Comparative Example 2 in which the formation temperature was 800°C and the thickness of the graphite layer was 1.5 nm, which is thinner than 2 mm, the orientation was very good, but
Regarding the electron emission density, a satisfactory effect could not be obtained.

As is clear from Examples 1 to 8 above, in order to form a C-axis oriented graphite layer, it is desirable to heat the substrate temperature to 700° C. or higher, more preferably 750° C. or higher. The thickness of the C-axis oriented graphite layer is 2 nm or more, preferably 10 nm or more and 1 μm or less, and more preferably 50 nm or more and 500 nm or less. If the thickness is less than 2 nm, it will scatter in the diamond forming atmosphere, and the effect of improving the emission current will not be sufficiently obtained, and even if the thickness is 1 μm or more, the above effect will not be improved.

[0054] The conditions for forming the graphite layer are not limited to those mentioned above, but as a raw material gas,
For example, other hydrocarbon gases such as ethylene, acetin, and benzene, and additive gases such as H2, Ar, and He may be introduced into the hydrocarbon gas. Further, the accelerating voltage can be selected within the range of 0.1 kV to 50 kV.

Furthermore, the method of forming the graphite layer is not limited to the method described above, and other methods such as
The present invention can also be achieved by a VD method, a plasma CVD method, or the like.

It is preferable to make the n-type semiconductor layer as thin as possible in the pn junction type devices shown in Examples 1 to 8 as described above, and when using a diamond layer as the n-type semiconductor layer, it is preferable to make the n-type semiconductor layer as thin as possible. It can be formed by adding elements of group V of the periodic table such as nitrogen and phosphorus, lithium, and the like. As a method for adding these impurities, a method of adding these impurity-containing gases to a source gas, an ion implantation method, etc. can be used. When using a semiconductor other than diamond as the n-type semiconductor layer, semiconductor materials of Group II, Group III, Group V, and Group VI of the periodic table such as Si, Ge, In, As, and P are used. or a combination thereof, furthermore, amorphous silicon or amorphous carbide can be used. These materials can be doped with impurities of 1×10 20 atoms/cm 3 or more, and the specific resistance value of the n-type semiconductor layer can be made as low as about 10 −4 Ω·cm.

[0057] Furthermore, the work function lowering material layer formed on the electron avalanche inducing layer is made of an energy that is obtained by reducing the activation energy when doping with an impurity element due to the wide energy band gap of diamond (5.4 eV). Electron emission can be performed more efficiently by using a material with the following work function. Materials that can be used when boron is used as an impurity include materials listed in Periodic Table 1A.
Materials with a work function of 5.0 eV or less among the elements of Groups 7A to 7A and Groups 2B to 4B, Ir, Pt, Au, etc. of the elements of Group 8 and 1B of the periodic table. elements, lanthanoid elements, and various metal silicides,
Some metal borides and metal carbides can also be used. Further, a combination of the above-mentioned elements and materials may be used.

Among these work function decreasing materials, Au,
Elements such as Ir, Pd, Pt, Ag, Cu, and Ph are particularly preferred because they have low resistance and are difficult to migrate. In addition, these materials are chemically stable compared to work function-lowering materials such as cesium that are formed on the surface of conventional semiconductor electron-emitting devices, and have a relatively low degree of vacuum (10-3To
rr), it is possible to stably emit electrons.

[0059] These materials can be deposited on semiconductors with extremely good controllability, such as by electron beam evaporation.
By depositing to a thickness of less than 100 Å, preferably from a monolayer to a few atomic layers, hot electrons can pass through these low work function materials without significant loss of energy, resulting in stable electron emission. It can be performed.

[0060] In Examples 1 to 8 described above, the case where a diamond layer was used as the n-type layer was shown, but the same effect can be obtained by using an n-type semiconductor layer having a smaller band gap than the p-type diamond layer. Can be done.

(Embodiment 9) Next, a Schottky junction type electron-emitting device will be explained with reference to FIGS. 2(a) and 2(b).

FIG. 2(a) is a plan view, and FIG. 2(b) is a plan view.
) is a sectional view taken along line A-A.

In the figure, 201 is a p + -type semiconductor substrate, and in this example Si (100) was used. 202
is a p-type diamond layer. 203 is a mask for insulating selective deposition, and here a SiO2 layer is used. 20
4 is a p+ type diamond layer, 205 is a Schottky electrode, here tungsten (work function: 4
．． 55 eV) was used. 206 is an insulating layer, 207
is an extraction electrode. Reference numeral 208 denotes an ohmic contact electrode in which Al is vapor-deposited on the back surface of the p+ type semiconductor substrate 201. 209 is a power supply for applying a reverse bias voltage Vb between the Schottky electrode 205 and the ohmic contact electrode 208, and 210 is a power supply for applying an extraction voltage Vg between the Schottky electrode 325 and the extraction electrode 207. It is a power source for

The above device was manufactured by the following method. (1) First, in the same manner as in Example 1, a 100 nm thick C-axis oriented graphite layer was formed on a p+ type semiconductor substrate 201. (2) Next, a 1 μm thick p-type diamond layer 202 was formed on this graphite layer by hot filament CVD. The formation conditions were: substrate temperature of 1000°C, pressure of 100 Torr, gas flow rate of H2: 200SCCM,
CH4: 1SCCM, 100ppm B2 H6 (hydrogen dilution): 1SCCM, filament temperature 2100℃
And so.

The diamond crystal formed in this example was
The orientation was measured using line diffraction and found to be good.
111} plane orientation. (3) Next, an insulating selective deposition mask 203 of SiO2 was formed at a predetermined position by a photolithography resist process. (4) Next, a p+ type diamond layer 204 was formed to a thickness of 1000 mm by hot filament CVD. The formation conditions were gas flow rate H2: 200SCCM, CVH
4:1 SCCM, 100 ppm B2 H6 (hydrogen dilution): Same as above (2) except that 5 SCCM was used.

This p+ type diamond layer 204 is made of Si
It did not precipitate on the O2 insulating selective deposition mask 203, but selectively deposited only in the opening of the insulating selective deposition mask 203 (exposed part of the p-type diamond layer 202). (5) Next, a Schottky electrode (100 mm thick) 20 made of tungsten was made using photolithography technology.
5. An insulating layer 206 made of SiO2 and an extraction electrode 207 made of polysilicon were both formed into predetermined shapes.

When a reverse bias voltage Vb is applied between the Schottky electrode 205 and the ohmic contact electrode 208 of the semiconductor electron-emitting device manufactured as described above, the p+ type diamond layer 204 and the Schottky electrode 20
Avalanche amplification occurs at the interface with Schottky electrode 205, and the generated hot electrons pass through the Schottky electrode 205 and seep into the vacuum region. Furthermore, by applying an extraction voltage Vg between the extraction electrode 207 and the Schottky electrode 205, Electrons e- could be emitted to the outside of the device.

The emission current density at this time was significantly increased by about 6 times compared to the device in which a p-type diamond layer was formed in the same manner as in the above example without forming a C-axis oriented graphite layer. .

The material for the Schottky electrode in the Schottky junction type semiconductor electron-emitting device as described above is a material that does not easily migrate even at high temperatures, and also has a wide energy band gap of diamond (5.4
If a material having a work function less than the activation energy when doped with an impurity element (eV) is used, electron emission can be performed more efficiently. Materials that can be used when boron is used as an impurity include materials with a work function of 5.0 eV or less among elements of Groups 1A to 7A of the periodic table and Groups 2B to 4B of the periodic table; Among the elements of Group 8 and Group 1B of the Table of Contents, Ir,
Elements such as pt and Au, lanthanoid elements, and some of various metal silicides, metal borides, and metal carbides can also be used. Further, a combination of the above-mentioned elements and materials may be used.

Among these Schottky electrodes, high melting point metals such as tungsten, tantalum, and molybdenum, various metal silicides, metal borides, metal carbides, etc. are used to replace cesium, which is formed on the surface of conventional semiconductor electron-emitting devices. They are chemically stable compared to low work function materials such as PD, PT, Au, Ir, Ag, Cu, PH, etc., which have low resistance and are difficult to migrate, so they are preferably used.
Stable electron emission is possible even at a relatively low degree of vacuum (approximately 10 −3 Torr).

[0071] The work function of these materials is 1.5 to 5.0.
eV, which makes a good Schottky electrode for all p-type semiconductor layers. These Schottky electrode materials can be deposited on semiconductors with extremely good controllability by electron beam evaporation, etc., and can be deposited to a thickness of 1000 Å or less, more preferably 500 Å or less, to prevent generation near Schottky junctions. The hot electrons can be passed through the Schottky electrode without significant loss of energy, making it possible to perform stable electron emission.

By using the Schottky electrode described above, a good Schottky junction type semiconductor electron-emitting device can be obtained.

The formation of the p-type diamond layer in the semiconductor electron-emitting devices shown in each of Examples 1 to 9 described above is performed using the known hot filament CVD method or microwave plasma CVD method.
Gas phase synthesis methods such as the D method, magnetic field microwave plasma CVD method, direct current plasma CVD method, RF plasma CVD method, and combustion flame method can be used.

As carbon raw materials, hydrocarbon gases such as methane, ethane, ethylene, and acetylene, alcohols, liquid organic compounds such as acetone, carbon monoxide, etc. can be used, and hydrogen, oxygen, chlorine, fluorine, etc. A gas containing can be added.

Further, as an impurity for forming the p-type diamond layer, an element of group III of the periodic table, such as boron, can be used. The method of adding boron is as follows:
A method of adding a boron-containing compound to the source gas, an ion implantation method, etc. can be used.

[0076]

[Effects of the Invention] As explained above, the present invention provides the following effects.

(1) By forming a C-axis oriented graphite layer on a substrate, it is possible to easily form a {111}-plane oriented diamond layer with high nucleation density and good smoothness on top of the C-axis oriented graphite layer. Therefore, the emission current density can be improved.

(2) In a p-n junction type device, by using a diamond layer as the p-type layer, it is possible to obtain excellent thermal conductivity and stable electron emission characteristics with less local heat generation of the device due to heat dissipation. , the life of the element becomes longer.

(3) In a pn junction type device, by using an n-type semiconductor layer with a smaller energy gap than the diamond layer, which is a p-type layer, it becomes possible to emit electrons with a smaller reverse bias voltage and also to reduce heat generation. This enables highly stable electron emission.

(4) In a p-n junction type element, by forming both the p-type layer and the n-type layer with diamond layers, the energy band combination at the junction interface is smooth and there is little scattering of electrons, resulting in good electron emission. characteristics are obtained.

(5) In the Schottky junction type device, by making the diamond semiconductor layer a p-type layer, the range of materials to be used as the Schottky electrode can be expanded,
It becomes possible to form a Schottky junction that can emit electrons more stably. (6) By using the semiconductor electron-emitting device of the present invention, highly reliable displays, EB (electron beam) drawing devices, vacuum tubes, electron beam printers, memories, etc. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a semiconductor electron-emitting device of the present invention, (a) is a plan view, and (b) is an A-A
FIG.

FIG. 2 is a diagram showing another embodiment of the semiconductor electron-emitting device of the present invention, (a) is a plan view, and (b) is an A-
It is an A-line sectional view.

FIG. 3 is a diagram showing an example of an energy band of a pn junction type electron-emitting device; (a) is a schematic diagram of an energy band in a pn junction type semiconductor electron-emitting device made of p-type diamond and n-type diamond; (b) is a schematic diagram of energy bands in a hetero pn junction type semiconductor electron-emitting device.

FIG. 4 is a schematic diagram showing an example of energy bands in a Schottky junction type semiconductor electron-emitting device.

FIG. 5 is a diagram showing an example of an ion beam apparatus used for forming a C-axis oriented graphite layer.

[Explanation of symbols]

101, 201 p+ type semiconductor substrate 102, 2
02 p-type diamond layer 103, 203
Insulating selective deposition mask 104 N-type diamond layer 105, 108, 208 Ohmic contact electrode 106, 206 Insulating layer 107, 207 Leading electrode 109, 110, 209, 210 Power source 111
Work function lowering material layer 204 p+ type diamond layer 205
Schottky electrode 501 Vacuum chamber 502 Ion beam source 503 Gas inlet 504 Exhaust port 505 Ion beam 506 Substrate heating holder 507 Substrate

Claims (4)

[Claims] 1. A semiconductor electron-emitting device using a diamond semiconductor layer, comprising a C-axis oriented graphite layer having a thickness of 2 nm or more and a diamond semiconductor layer having crystal orientation formed in this order on a substrate. A semiconductor electron-emitting device characterized by: 2. The diamond semiconductor layer having crystal orientation is a p-type layer, and the diamond semiconductor layer is of a p-n junction type, in which an n-type semiconductor layer having a smaller energy gap than the diamond semiconductor layer is formed on the p-type layer. The semiconductor electron-emitting device according to claim 1, characterized in that: 3. The semiconductor electron-emitting device according to claim 2, wherein the n-type semiconductor layer is a diamond layer. 4. The diamond semiconductor layer according to claim 1, wherein the diamond semiconductor layer having crystal orientation is a p-type layer, and is of a Schottky junction type in which a Schottky electrode layer is formed on the p-type layer. semiconductor electron-emitting device.