JPH07105353B2 - Semiconductor diamond and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a diamond having semiconductor characteristics, which is used in electronic devices and the like.

[Conventional technology]

Although diamond has a bandgap of 5.5 eV and is essentially insulating, diamond forms an impurity level by doping with an impurity like Si and Ge to form a P-type and an N-type.
It is of course conceivable to have the semiconductor characteristics of the mold.

In fact, there is a P-type semiconductor containing B in natural diamond, which is called II b diamond. This II
b Diamond can also be manufactured by ultra-high pressure synthesis. However, N-type semiconducting diamond does not exist in nature. In addition, there is no example in which the N-type semiconductivity is confirmed even in the one manufactured by the ultrahigh pressure synthesis method.

[Problems to be solved by the invention]

N-type semiconductor diamond is indispensable for forming a semiconductor diamond device utilizing a PN junction.

However, until now, doping of diamond has been tried by an ultra-high pressure synthesis method or an ion implantation method.
There is no example of obtaining a type semiconductor diamond.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an N-type semiconductor diamond and a method for producing the same.

[Means and Actions for Solving Problems]

The present inventors have decided to use P or As instead of P or As of the V group element which is usually considered as a dopant element for diamond.
It was conceived to use S as a dopant, which has a smaller covalent radius than As and has a value close to that of C. As a result of various experiments and studies, diamond containing S can be produced by, for example, a vapor phase thin film synthesis method, an ultrahigh pressure single crystal synthesis method, an ion implantation method, etc. The S-doped diamond is a donor formed by S. The inventors have found that N-type semiconductivity is exhibited by free electrons from the level, and arrived at the present invention.

That is, the present invention relates to a semiconductor diamond containing S as a dopant element, and one having a S concentration of 1 × 10 ¹⁰ to 1 × 10 ²⁰ [cm ⁻³ ] is particularly preferable.

Furthermore, the present invention uses a raw material gas having a ratio S / C (%) of the number of S atoms and the number of C atoms in the raw material gas of 0.001 to 1.0% as a method for producing a semiconductor diamond containing S. A semiconductor diamond containing S as a dopant element, and a semiconductor diamond containing S as a dopant element by an ultrahigh pressure synthesis method. Provided is a method for producing a semiconductor diamond, and a method for producing a semiconductor diamond, which comprises obtaining a semiconductor diamond containing S as a dopant element by an ion implantation method.

Diamond is composed of a covalent bond of group IV element C. S of Group VI elements that entered diamond as impurities
When is replaced by the lattice position of C, there are two outer shell electrons that are not involved in the covalent bond, and it is considered that these are donor electrons and diamond exhibits N-type semiconductivity. That is, S is doped in diamond to form a donor level in the forbidden band.

Further, it is expected that the donor level can be formed even if S is not substituted at the C lattice position, as in the case where S enters between C lattices and forms a pair with this vacancy.

In fact, it was confirmed that when S-doped diamond was produced based on the above idea, it exhibits N-type semiconductivity.

In the S-doped semiconductor diamond of the present invention, if the S concentration is less than 1 × 10 ¹⁰ to 1 × 10 ²⁰ [cm ⁻¹ ], the resistivity becomes too high to be used as a semiconductor, and 1 × 10 ²⁰ [cm ⁻¹ ].
If it exceeds, the conductive form becomes metallic and the property as a semiconductor is lost.

The S-doped semiconductor diamond of the present invention can be produced by a known technique such as a vapor phase thin film synthesis method, an ultra-high pressure single crystal synthesis method, an ion implantation method, and the S-doped semiconductor obtained by any method. There was no difference in the properties of diamond.

When the S-doped semiconductor diamond of the present invention is produced by the vapor phase thin film synthesis method, it is preferable that the ratio S / C ratio of the number of S atoms to the number of C atoms in the source gas is 0.001% to 1.0%. S in the diamond obtained by performing in this range
1 × 10 ¹⁰ to 1 × 10 ²⁰ [cm ^-1 ] effective concentration as a semiconductor
Because it can be

As a raw material, for example, CH ₄ , C ₂ H ₆ , C ₃ H ₈ as a C supply source
And the like, alcohols such as CH ₃ OH, C ₂ H ₅ OH, and the like, and examples of the S supply source include H ₂ S, CS ₂ , SO ₂ , SF _{6, and the} like.

Various conventional techniques can be applied as a vapor phase thin film synthesis method. As an example, the case of using the microwave plasma CVD method will be described.Introducing a reaction gas into the chamber, while guiding the microwave oscillated from the magnetron to the chamber by the rectangular waveguide, and causing a discharge in the reaction gas in the chamber. Conduct a diamond synthesis reaction.

Specific conditions and methods for obtaining the S-doped diamond of the present invention by the vapor phase thin film synthesis method, the ultrahigh pressure single crystal synthesis method or the ion implantation method will be described in detail in the following examples.

〔Example〕

Example 1 By a known microwave plasma CVD method, a reaction gas composed of CH ₄ : 0.5%, H ₂ S: 0.000005 to 0.005% and the balance H ₂ was used as a raw material on a diamond single crystal substrate (111) surface to form 1.0 A μm thick S-doped diamond film of the present invention was grown. The reaction system pressure is 30 Torr, the microwave is
It was 2.54GHz and output was 350W.

When the resistivity and the hole of the obtained S-doped diamond epitaxial film were measured, it was confirmed that the Hall coefficients were all (-) and that the film was an N-type semiconductor. Further, the S concentration in diamond was measured by STMS.
The measurements of S / C%, free electron density, electron mobility and S concentration are summarized in Table 1. The S concentration of the No. 1 and No. 2 samples is a value estimated from the free electron density.

Example 2 An S-doped diamond single crystal of the present invention was obtained by an ultra-high pressure method by dissolving a diamond powder containing S mixed in an Fe-Ni solvent and placing it under conditions of 5 GPa and about 1400 ° C. for 7 hours. . When this product of the present invention was measured in the same manner as in Example 1, the Hall coefficient was (-).
The ratio S / C (%) of the number of S atoms and the number of C atoms of the raw material, the free electron density, the electron mobility and the S concentration were as shown in Table 2.
The S concentration of No. 9 is an estimated value from the free electron density.

Example 3 S acceleration voltage of 150 KeV and S implantation amount of 10 ¹⁵ by ion implantation method
S was injected into the diamond single crystal under the condition of 1 / cm ² to produce the S-doped diamond of the present invention. After the S-doped diamond thus obtained was annealed in vacuum, hole measurement and resistivity measurement were performed. The Hall coefficient was (-), and it was confirmed to be an N-type semiconductor. The average free electron density of the S injection part is 10 ¹⁶ [1 / cm ³ ] and the electron mobility is 40 [cm ² /
Vs].

〔The invention's effect〕

As is clear from the above description and the results of the examples, the S-containing diamond of the present invention realizes an N-type semiconductor diamond which has never been obtained. Therefore, by using the S-containing diamond of the present invention, it becomes possible to fabricate a diamond semiconductor device utilizing PN junction.

Further, application to a thermistor or application as a diamond coating film which is simply required to have conductivity can be considered. In these cases, polycrystalline diamond is also effective.

As described above, the S-doped diamond of the present invention, which has a wide range of uses as a diamond semiconductor, is advantageous in that it can be easily obtained by applying a known technique in terms of its production method.

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Claims (5)

[Claims] 1. A semiconductor diamond containing S as a dopant element. 2. S is 1 × 10 ¹⁰ to 1 × as a dopant element.
The semiconductor diamond according to claim 1, which is contained at a concentration of 10 ²⁰ [cm ^-3 ]. 3. A ratio of the number of S atoms and the number of C atoms in the source gas.
A method for producing a semiconductor diamond, comprising obtaining a semiconductor diamond containing S by a vapor phase thin film synthesis method using a source gas having an S / C (%) of 0.001% to 1.0%. 4. A method for producing a semiconductor diamond, which comprises obtaining a semiconductor diamond containing S as a dopant element by an ultrahigh pressure synthesis method. 5. A method for producing semiconductor diamond, which comprises obtaining semiconductor diamond containing S as a dopant element by an ion implantation method.