JP3760478B2 - Method for producing group III-V compound semiconductor device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a semiconductor element such as a field effect transistor, a photodiode or a light emitting diode (LED) having a group III-V nitride semiconductor layer exhibiting n-type conductivity, and more particularly, a group VI atom is doped. The present invention relates to a group III-V nitride semiconductor device.
[0002]
[Prior art]
Aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), and their mixed crystals III-V nitride semiconductor layers can be used as buffer layers, active layers, contact layers, etc. It is used for optical devices such as electronic devices and ultraviolet detectors. In these semiconductor elements, a III-V nitride semiconductor layer having a conductivity type of n-type or p-type doped by intentionally adding impurities is used.
[0003]
The p-type group III-V nitride semiconductor layer is doped with atoms belonging to group II of the periodic table of elements such as zinc (Zn) and magnesium (Mg) in a vapor phase growth method such as MOVPE. Is obtained. On the other hand, in order to obtain a group III-V nitride semiconductor layer exhibiting n-type conductivity, group IV silicon (Si) has been conventionally used as a dopant. Group VI atoms also act as n-type impurities in principle for III-V nitride semiconductors.
[0004]
In III-V nitride semiconductors, like other III-V compound semiconductors such as GaAs, for example, group atoms such as Si are vacancy of group III atoms in the semiconductor layer. That is, by occupying the position of gallium (Ga) vacancies (represented by (Ga) v) and releasing thinly-bound electrons from the relationship of valence, n-type conduction is caused in the semiconductor layer Gives sex. If this is expressed schematically, it will become like Formula (1).
Si + (Ga) _V → Si _Ga + E ^- ・ ・ ・ ・ ・ Formula (1)
In formula (1), the symbol Si _Ga Is (Ga) _V Represents a Si atom occupying ^- Means an electron which causes the n-type conductivity emitted thereby.
[0005]
FIG. 1 illustrates the dependence of the V / III ratio on the vacancy concentration at a certain growth temperature in the vapor phase growth of the III-V compound semiconductor layer by the MOVPE method. As shown in FIG. 1, a III-V compound semiconductor (Ga) _V The concentration (130) of the group III atom vacancy is, for example, the amount of the group V atom relative to the amount of the group III atom in the growth environment when the III-V compound semiconductor layer is vapor-phase grown by the MOVPE method. Increasing the ratio tends to increase. Therefore, in order to obtain an n-type group III-V nitride semiconductor layer by doping Si, it is efficient to increase the density of group III atom vacancies according to formula (1). I understand. For example, when an n-type group III-V nitride semiconductor doped with Si, such as GaN, is obtained by the MOVPE method, the amount of group V element N in the growth environment is adjusted to the group III element. It is necessary to increase the concentration of atoms.
[0006]
The vapor phase growth of the III-V nitride semiconductor layer by the VPE method or the MBE method is not limited to the MOVPE method, and ammonia (NH _Three ) Is used as an N source. As a raw material for Group III constituent atoms, trimethylgallium ((CH _Three ) _Three Ga), trimethylaluminum ((CH _Three ) _Three Al) and trimethylindium ((CH _Three ) _Three Organometallic compounds such as In) are used. In general, these organometallic compounds can be easily and irreversibly decomposed at low temperatures to supply metal atoms to the growth system. But NH _Three In contrast to these organometallic compounds, they are hardly decomposable at low temperatures and exhibit reversible degradation.
This NH _Three As a result, the V / III ratio cannot be easily increased due to the disproportionate disproportionability and reversibility of the decomposition reaction compared to the organic group III compounds. That is, inefficiency of doping of the group IV atoms such as Si into the group III-V nitride semiconductor layer has been caused.
[0007]
FIG. 2 shows that the inventors set the growth temperature to 750 ° C. _Three The dependence of the sheet resistance on the V / III ratio when Si is doped into GaN by the MOVPE method using N as the N source is illustrated. The V / III ratio referred to here is NH used as a raw material for GaN film formation. _Three And (CH _Three ) _Three Supply ratio of Ga to the growth reaction system, that is, NH _Three / (CH _Three ) _Three The supply ratio of the raw material to the growth reaction system represented by Ga is shown. The sheet resistance is inversely proportional to the carrier concentration, and generally takes a low value as the carrier concentration increases. As shown in FIG. 2, although the sheet resistance tends to decrease as the V / III ratio increases, for example, the V / III ratio normally employed for MOVPE growth of a GaAs layer is an order of magnitude larger. Finally 10 ¹⁵ -10 ¹⁶ cm ^-3 A low carrier concentration can be obtained. As shown in FIG. 2, in the vapor phase growth of GaAs by the atmospheric pressure MOVPE method, the carrier concentration is 10 even when the V / III ratio is 20 to 30 and the low ratio side. ¹⁸ cm ^-3 Thus, an n-type layer with a high carrier concentration that can be sufficiently used as an active layer, a contact layer, or the like of a normal semiconductor element, which has a low sheet resistance exceeding 1 can be obtained. Thus, the efficiency of doping the Group IV atom into the nitrogen-containing Group III-V compound layer is extremely poor. 10 as above ¹⁵ -10 ¹⁶ cm ^-3 A nitrogen-containing compound layer having a low carrier concentration is generally difficult to use as an active layer of a semiconductor device. Even in a field effect transistor, the active layer has 10 ¹⁷ cm ^-3 Some n-type semiconductor layer is required. That is, the low doping efficiency of the Group IV atom with respect to the III-V group compound layer has resulted in the low productivity of the semiconductor device using the n-type nitrogen-containing compound layer.
[0008]
The low doping efficiency of Group IV atoms for III-V nitride semiconductors is (Ga) _V This is due to the low concentration of. As in the experimental example described above, when the V / III supply ratio of the raw material is set much higher than that of GaAs, for example, a semiconductor layer having a high carrier concentration corresponding to the actual V / III ratio in the growth reaction system. Enough to get easily (Ga) _V Means that the concentration of is still reached.
[0009]
In III-V compound semiconductors, the concentration of group III atoms ([III] _V Represented by ) And vacancy concentration of group V atoms ([V] _V Represented by The relationship expressed by the following equation (2) is established at a certain temperature.
[III] _V × [V] _V = C (constant) ... Equation (2)
That is, at a certain temperature [III] _V And [V] _V The product value of is a positive constant. From the relationship expressed by this formula (2) [III] _V Conversely, if the concentration of is [V] _V The concentration of is known to increase. Thus, for example, in the case of GaN, (Ga) _V As the concentration of N decreases, N vacancies ((N) _V ) Concentration ([N] _V ) Increases.
[0010]
[V] _V In order to obtain a III-V nitride semiconductor layer exhibiting n-type conduction in a high state, it is convenient to dope a group VI atom instead of a group IV atom. This is because, as shown in the following formula (3), if the vacancies of the group V atoms are occupied by hexavalent sulfur (S) atoms, for example, free electrons that cause n-type conduction can be emitted from the valence relationship. It is.
S + (V) _V → S _V + E ^- ・ ・ ・ ・ ・ Formula (3)
Where S _V Shows a state in which the vacancies of the group V atoms are occupied by the S atoms.
[0011]
Conventionally, hydrogen sulfide (H) has been used as a doping gas for doping group III atoms such as S and selenium (Se) into a group III-V compound semiconductor. ₂ S) and hydrogen selenide (H ₂ Se) is used. For example, (CH _Three ) _Three An n-type GaAs layer is grown by MOVPE using Ga as a Ga source. Also (CH _Three ) _Three Even in the MOCVD growth of InP using In as the In source, H ₂ An n-type InP layer doped with S using S as a doping gas is obtained. However, these trialkyl Group III compounds, which generally exhibit Lewis acidity, generally react readily with Lewis basic Group V hydrogen compounds at room temperature and inhibit normal MOVPE growth. Compared with trialkyl compounds of In and Ga, trialkylAl compounds having a strong Lewis acidity generate a solid material that is difficult to dissociate by an electron donating / accepting reaction represented by the following formula (4) even at room temperature (Gmelin Handbuch der Anorganischen Chemie (Achte vollih neu bearbeite Auflag), Springer-Verlag (1981), p. 56.).
Al (C ₂ H _Five ) _Three (G) + H ₂ Se (g) → Al ₂ Se (s) Formula (4)
In the equation (4), the symbols (g) and (s) indicate that these substances are in a gas state and a solid state at room temperature, respectively. For example, Al _x Ga _1-x When controlling the composition ratio of Al in As (x represents the composition ratio), if such a reaction occurs, the consumption of Al in the production of solids may result in the case where the desired Al composition ratio cannot be obtained. . If the composition ratio of Al is different from the designed value, Al having the desired band gap _x Ga _1-x As layer is not obtained. Forbidden band fluctuations due to the instability of the Al composition can be attributed to electrical characteristics such as electron mobility in semiconductor devices that use band discontinuities at heterojunctions such as high mobility field effect transistors. It is not preferable because it causes instability. For this reason, in the group III-V compound semiconductor layer containing Al, there is almost no example in which an n-type conductive layer doped with S, which is a Group VI element, is practically used as one layer constituting a semiconductor element. It can be inferred in principle that the group VI atoms act as n-type dopants for III-V nitride semiconductors such as GaN, and it has been proposed that the group VI atoms be n-type dopants. Although (Japanese Patent Laid-Open No. 5-190903), a semiconductor element including a group III-V nitride semiconductor layer exhibiting n-type conduction obtained by doping a group VI atom has not been put into practical use.
[0012]
The reaction shown in formula (4) is represented by (CH ₃ ) ₃ Ga or (CH ₃ ) ₃ It also occurs with trialkyl compounds such as In. However, a trialkyl compound of Ga or In is not a conspicuous reaction because Lewis acidity is generally weaker than that of an Al trialkyl compound. In any case, the situation is the same in the conventional vapor phase growth method such as MOVPE method of a group III-V nitride semiconductor using a trialkyl compound as a group III atom source. [V] superior in obtaining an n-type nitride semiconductor layer by doping _V In order to obtain an n-type semiconductor layer in spite of its high state VI When doping a group atom, there has been a problem associated with the reaction of Lewis acid and Lewis base as described above.
[0013]
As a group III atom supply source, it is appropriate to use a group III trialkyl compound because it has an appropriate vapor pressure and has a high purity for growing a semiconductor layer. To obtain the n-type group III-V nitride semiconductor layer by doping the group VI atom, the trialkyl compound of group III is used as the source of the group II atom to overcome the above-mentioned conventional problems. Therefore, new Group VI compounds that can avoid and suppress Lewis acid / base reactions with these trialkyl Group III compounds are desired. However, new compounds containing Group VI elements that meet this purpose and are suitable as doping materials have not yet been proposed.
[0014]
As a compound that becomes a doping material for the semiconductor layer, one of the necessary conditions is that it contains a group VI, but not all compounds containing a group VI atom are suitable as a doping material. For example, a compound containing an oxygen (O) atom, such as a carboxyl group (—COOH), a ketone group (═CO), a nitroso group (—NO), or nitro (—NO) ₂ ) A compound containing a Group VI atom to which a substituent such as a group is added is not preferable regardless of a gas phase method such as VPE, MOVPE, or MBE. This is because when a mixed crystal such as AlN, AlInN, GaInN, or AlGaInN containing oxidizable Al atoms as constituent atoms is grown, the Al atoms are oxidized by oxygen and a high-quality Al-containing film is not formed.
[0015]
Further, when the compound containing a Group VI atom as a doping material is an organic compound, there is a concern that carbon (C) is mixed into the III-V nitride semiconductor layer. For example, an organic alkyl compound such as trimethylgallium and hydrogen sulfide (H as a doping source of ammonia and a group VI element as a nitrogen source) ₂ The concentration of carbon atoms in the GaN layer containing sulfur (S) grown by the MOCVD method under reduced pressure using S) is 10 ¹⁸ cm ^-3 Sometimes high and low concentrations were reached. If such a high concentration of carbon is mixed in the originally colorless and transparent GaN semiconductor layer, it may be a cause of impairing the transparency of the GaN layer. An opaque semiconductor layer, not limited to GaN, is, for example, a semiconductor element composed of a semiconductor layer that is required to transmit light, such as a light emitting diode, and the like. Bring about a bug. Therefore, when selecting an organic compound containing a Group VI element, an organic compound that easily decomposes and produces a decomposition product that can be easily discharged from the growth reaction system is selected by a decomposition method such as thermal decomposition or photolysis. There is a need to. However, organic compounds containing Group VI atoms that are considered suitable as dopants have not been systematically presented so far, and a slight amount of diethyl sulfide ((C ₂ H _Five ) ₂ S) is only presented. However, this diethyl sulfide has an ethyl group (C) which is a sulfur (S) atom and two aliphatic hydrocarbon substituents. ₂ H _Five -) Is an added compound. The number of carbon atoms constituting the ethyl group is 2, and the space area occupied by the molecule itself is small. Therefore, the space around the sulfur atom cannot be occupied so as to surround the sulfur atom. Therefore, it is not sufficient to suppress the electron donating / accepting reaction with the trialkyl compound.
[0016]
[Problems to be solved by the invention]
In the present invention, the III-V nitride semiconductor layer is doped with a group VI atom by utilizing the intrinsic height of the vacancy concentration of the group V atom in the group III-V nitride semiconductor layer. In obtaining an n-type group III-V nitride semiconductor layer required for constituting a semiconductor device, an electron donating / accepting reaction with a group III trialkyl compound exhibiting Lewis acidity can be suppressed and avoided, and An organic compound containing a Group VI element capable of suppressing carbon contamination is presented as a new doping material, and a semiconductor device including an n-type Group III-V nitride semiconductor layer doped with a Group VI atom is provided. To do.
[0017]
[Means for Solving the Problems]
The present invention has been developed to solve the above-described problems, and is a group III-V nitride semiconductor doped with a group VI element using a specific organic compound.
That is, the semiconductor device of the present invention is a group III-V compound semiconductor device containing at least one element of aluminum, gallium, indium and a group III (element periodic table, hereinafter the same) element and nitrogen. This is a group VI element doped with an organic compound that satisfies the following requirements as a doping source.
The organic compound used as a dopant is a constituent requirement
a) A chain hydrocarbon compound containing at least one element selected from sulfur, selenium, and teru and a hydrocarbon group having 3 or more carbon atoms
b) Aromatic hydrocarbon compounds containing at least one element of sulfur, selenium and tellurium
c) An alicyclic hydrocarbon compound containing at least one element of sulfur, selenium, and tellurium
d) A heterocyclic hydrocarbon compound containing at least one element of sulfur, selenium, and tellurium
Shall be satisfied.
As constituents desired for the organic compounds used as these dopants,
i) Contains Group VI elements.
ii) Substituents other than the skeleton do not contain a bond between a carbon atom and a nitrogen atom.
iii) Substituents other than the skeleton do not contain a bond between a carbon atom and a hydrogen atom.
iv) Does not contain oxygen atoms.
Etc.
These representative compounds are listed below structurally.
In the present invention, the above compound is doped with one or more Group VI elements of S, Se, or Te, and the carbon concentration is 8 × 10 8. ¹⁶ cm ^-3 Provided is a semiconductor device provided with the following nitrogen-containing III-V compound semiconductor layer.
[0018]
Examples of III-V nitride semiconductors according to the present invention include GaN, AlN, InN, AlGaN, GaInN, AlInN, and AlGaInN. Further, a III-V nitride semiconductor containing arsenic (As) or phosphorus (P) as a Group V element in addition to N also corresponds to the present invention. This includes GaNAs, GaNP, AlNAs, AlNP, InNAs, InNP, AlGaNAs, AlGaNP, GaInNAs, GaInNP, AlInNAs, AlInNP, AlGaInNAs, AlGaInNP, GaNPAs, AlNPAs, InNPAs, AlGaInNPAs, etc., and thallium (Tl) compounds. is there.
[0019]
A chain hydrocarbon group is a methyl group (CH _Three -), An ethyl group (CH _Three CH ₂ -Or C ₂ H _Five -) Or a propyl group (CH _Three CH ₂ CH ₂ -Or C _Three H ₇ -) And the like, a group in which one H of hydrogen atoms (H) constituting a straight chain or branched saturated aliphatic compound is eliminated. That is, when the number of carbon atoms (C) is expressed by a positive integer (n) (n ≧ 1), C _(n) H _{(2n + 1)} It is group represented by-.
[0020]
C _(n) H _{(2n + 1)} In the present invention, unsaturated hydrocarbon groups represented by-are collectively treated as aliphatic hydrocarbon groups. This includes ethylene or ethene groups (C ₂ H _Three -Or H ₂ C = CH-) or 1-butene group (HC = CHCH) ₂ CH ₂ -) Or 2-butene group (H ₂ CHC = CHCH ₂ -) Or an octene group (C ₈ H ₁₅ -) Etc. are mentioned. Here, for convenience, saturated and unsaturated aliphatic hydrocarbon groups (alkyl group and alkene group) are represented by the symbol R or R ′.
[0021]
In the present invention, a compound in which two hydrocarbon groups are bonded to at least one group VI atom of S, Se, and Te can be used. Oxygen (O) atoms are also inappropriate for Group VI atoms. Two hydrocarbon groups bonded to at least one group VI atom among S, Se, and Te may be the same or different from each other. If it shows with said symbol, the linear aliphatic compound which the group VI atom and two hydrocarbon groups couple | bonded among S, Se, and Te will be R-VI-R, R-VI-R ', etc. It can be expressed with a form.
[0022]
In the linear R-VI-R type aliphatic compound according to the present invention, hydrogen is bonded to the Group VI element that has been conventionally used as an n-type dopant for III-V compound semiconductors. For example, hydrogen sulfide (H ₂ S) and hydrogen selenide (H ₂ Compared to Group VI hydrides such as Se), a methyl group (CH) consisting of at least one carbon atom and at least three hydrogen atoms occupying a larger space volume than a hydrogen atom. _Three -) Etc. are added to Group VI elements. For this reason, it is not easy for the group VI atom in the compound according to the present invention to be sufficiently close to the group III atom of the trialkyl compound of the group III element that is Lewis acidic and susceptible to electrophilic reaction. Disappear. As a result, trialkyl compounds of group III elements and hydrogen sulfide (H ₂ S) and hydrogen selenide (H ₂ It is possible to further reduce the conventional gas phase polymerization reaction that hinders the smooth vapor phase growth caused by the electron donating / accepting reaction occurring between Se) and the like.
[0023]
In the R-VI-R type or RSR 'type compound described above, the conventional conjugation reaction with the trialkyl compound which is the starting material of the Group III atom due to the steric hindrance of the hydrocarbon group is R In the compound of -VI-R type or R-VI-R 'type, this is particularly remarkably avoided in the compound having at least one hydrocarbon group having 3 or more carbon atoms constituting the group. The hydrocarbon group having 3 or more carbon atoms constituting the group includes an isopropyl group having 3 carbon atoms (CH _Three (CH _Three ) CH-) or an isobutyl group having 4 carbon atoms (-CH ₂ CH (CH _Three ) CH _Three ) Etc. However, as the number of carbon atoms constituting the hydrocarbon group increases, the melting point of the compound generally increases. For example, diethyl sulfide having a straight-chain hydrocarbon group and an ethyl group having 2 carbon atoms is liquid at room temperature, but in dinordodecyl sulfide having a dodecyl group having 12 carbon atoms. Becomes solid at room temperature with a melting point of 38-40 ° C. Even if it is a solid at room temperature, it can be a dopant source for vapor phase growth if it exhibits an appropriate sublimation pressure. However, if it is intended to supply the dopant source to the vapor phase growth system by bubbling operation, the vapor source is removed from room temperature. It is desirable that the compound has a melting point within a temperature range of 70 to 80 ° C., which is a general heat resistant temperature of parts such as valves constituting the phase growth equipment. Therefore, when supplying the dopant source to the vapor phase growth system by bubbling operation of the liquid source, a compound having a hydrocarbon group having 3 or more carbon atoms and generally 12 to 15 or less is used. Is desirable.
[0024]
In the present invention, it is necessary to select a compound that does not contain a bond (N—H bond) between a nitrogen atom (N) and a hydrogen atom (H) in the substituent. In a nitrogen-containing III-V compound semiconductor layer such as GaN, for example, NH _Three If N—H bonds derived from substituents remain in the layer due to addition of N source such as in the vapor phase growth system, insufficient thermal decomposition of the compound to be mixed, etc., carriers also present in the layer This is because electrical activation as a conductive carrier is hindered. Therefore, in the present invention, for example, an amine group (NH is highly likely to cause the incorporation of NH bonds into the nitrogen-containing group III-V compound semiconductor layer. ₂ Compounds having a hydrocarbon group to which-) is added and compounds having a hydrocarbon group having an amine group as a substituent are excluded.
[0025]
In the present invention, a compound containing an aliphatic hydrocarbon group and an aromatic hydrocarbon group having a substituent or a functional group containing a bond (CN bond) between a carbon atom (C) and a nitrogen atom (N) Excluded. This is to avoid the operational dangers related to vapor phase growth due to the high possibility that harmful cyanic substances are generated by thermal decomposition.
[0026]
An example of a compound in which a substituent that does not contain an N—H bond or a C—N bond is bonded to the Group VI element is, for example, two identical linear saturated aliphatic hydrocarbon groups bonded to the Group VI element. Aliphatic compounds. For example, dinormal propyl sulfide ((CH _Three (CH ₂ ) ₂ ) ₂ S), dinormal butyl sulfide ((CH _Three (CH ₂ ) _Three ) ₂ S), dinormal amyl sulfide (dinormal pentyl sulfide) ((CH _Three (CH ₂ )Four ) ₂ S), dinormal hexyl sulfide ((CH _Three (CH ₂ ) _Five ) ₂ S), di-normal heptyl sulfide ((CH _Three (CH ₂ ) ₆ ) ₂ S), di-normal octyl sulfide ((CH _Three (CH ₂ ) ₇ ) ₂ S), di-nornorolyl sulfide ((CH _Three (CH ₂ ) ₈ ) ₂ S), di-normal decyl sulfide ((CH _Three (CH ₂ ) ₉ ) ₂ S), dinormaldodecyl sulfide ((CH _Three (CH ₂ ) ₁₁ ) ₂ Examples of the compound include R—S—R type (— represents a bond) such as S).
[0027]
An R—S—R ′ type aliphatic compound in which two different linear saturated aliphatic hydrocarbon groups (indicated by R and R ′) are bonded to the Group VI atom is also referred to in the present invention. It is an example of a compound formed by bonding a hydrocarbon compound to a group element. This includes methyl normal propyl sulfide (CH _Three (CH ₂ ) ₂ SCH _Three ), Normal butyl methyl sulfide (CH) _Three (CH ₂ ) _Three SCH _Three ), Normal heptyl methyl sulfide (CH) _Three (CH ₂ ) ₆ SCH _Three ), Methyl normal octyl sulfide (CH) _Three (CH ₂ ) ₇ SCH _Three ), Methyl normal nonyl sulfide (CH _Three (CH ₂ ) ₈ SCH _Three ), Normal decyl methyl sulfide (CH) _Three (CH ₂ ) ₉ SCH _Three ), Normal decyl methyl sulfide (CH) _Three (CH ₂ ) ₁₁ S CH _Three ), Ethyl normal propyl sulfide (CH _Three CH ₂ S (CH ₂ ) ₂ CH _Three ), Normal butyl ethyl sulfide (CH _Three (CH ₂ ) _Three SCH ₂ CH _Three ), Amyl ethyl sulfide (CH _Three (CH ₂ ) 4 SCH ₂ CH _Three ), Normal decyl ethyl (CH _Three (CH ₂ ) ₉ SCH _Three ), Normal butyl normal propyl sulfide (CH) _Three (CH ₂ ) _Three S (CH ₂ ) ₂ CH _Three )and so on.
[0028]
Examples of the compound in which an aromatic hydrocarbon group and a Group VI atom are bonded include, for example, thiophenol (Ph · S · H; Ph is a phenyl group (C ₆ H _Five -). ), 2-tertiarybutylthiophenol, 4-tertiarybutylthiophenol, phenyl selenol (Ph · Se · H), methylphenyl sulfide (Ph · S · CH) _Three ), 2,6-dimethylthiophenol, 3,4-dimethylthiophenol and 3,5-dimethylthiophenol, 2,4-ditertiary butylthiophenol, phenyl normal propyl sulfide (Ph · S · ( CH ₂ ) ₂ CH _Three ), Isopropylphenyl sulfide (Ph · S · CH (CH _Three ) ₂ ) And o-, m- and p-thiocresol congeners (CH _Three Ph.S.H), benzyl methyl sulfide (PhCH) ₂ ・ S ・ CH _Three ), Benzyl ethyl sulfide (PhCH ₂ ・ S ・ CH ₂ CH _Three Examples thereof include compounds containing a phenyl group such as
[0029]
Dibenzyl selenide ((PhCH ₂ ) ₂ Se) and dibenzyl sulfide ((PhCH ₂ ) ₂ The hydrocarbon groups contained as in S) may all be aromatic hydrocarbon groups.
[0030]
A compound containing a Group VI atom and a plurality of aromatic hydrocarbon groups can also be exemplified as a compound formed by bonding an aromatic hydrocarbon group and a Group VI atom. For example, 2-thionaphthol (also referred to as 2-Thionophthol, Naphthalene-2-thiol or 2-Mercaptonaphthalene) and thionaphthene (also referred to as Thionaphthene or 1-Benzothiophene) correspond to this.
[0031]
When the compound containing an aromatic hydrocarbon group as described above is thermally decomposed, for example, the aromatic hydrocarbon group formed by bonding with a Group VI atom is separated while maintaining its form, so that the aromatic ring There is an advantage that the hydrocarbon fragments generated by decomposition are few, and the contamination of the carbon into the growth layer due to the doping of the group VI atoms is reduced.
[0032]
In the present invention, a cycloaliphatic carbonization which contains a group VI element as a doping source, does not contain a bond between a carbon atom and a nitrogen atom or a bond between a nitrogen atom and a hydrogen atom and does not contain an oxygen atom as a substituent. A hydrogen compound (an alicyclic compound for short) is used.
The reason for eliminating the bond between the carbon atom and the nitrogen atom or the bond between the nitrogen atom and the hydrogen atom is as described above.
The cycloaliphatic compound of the present invention includes cyclohexylmethyl sulfide in which a cyclohexane ring and a methyl group are bonded to a sulfur (S) atom, a cyclohexan sulfide having a cyclohexane ring and an S atom bonded, and a phenyl group that is an aromatic hydrocarbon group. An example is cyclopropyl phenyl sulfide with (Ph-).
[0033]
In the present invention, a group VI atom and a hydrocarbon containing multiple bonds such as a double bond between carbon atoms (-C = C-; symbol-represents a single bond = represents a double bond, respectively). A compound containing a bond is used as a dopant source. There will be one pi (π) bond in the double bond and two π bonds in the triple bond. The hydrocarbon group possessing this π bond will be separated from the Group VI element by thermal decomposition. Even when the bond is broken and released, thermal structural stability is maintained by conjugation by the π bond. As a result, in a hydrocarbon group including multiple bonds, the possibility of generating fragments such as radicals containing carbon by splitting into smaller molecules is reduced. Therefore, there is an advantage that the contamination of carbon into the growth layer is reduced.
[0034]
Group VI atoms and carbon atoms The child joins and 2 Hydrocarbons containing multiple bonds such as double bonds Elementary An example of the compound is an aliphatic compound in which the same unsaturated aliphatic hydrocarbon group is bonded. For example, diallyl sulfide ((CH ₂ = CHCH ₂ ) ₂ S) R—S—R type compounds. An unsaturated aliphatic hydrocarbon group containing a double bond and a saturated hydrocarbon group VI Tribe atom The compound bonded to the allyl methyl sulfide (CH ₂ = CHCH ₂ SCH ₃ ), Allyl ethyl sulfide (CH ₂ = CHCH ₂ SCH ₂ CH ₃ ), Allyl normal hexyl sulfide ( (CH ₂ = CHCH ₂ ) ₂ S (CH ₂ ) ₅ CH ₃ ), Allyl normal dodecyl sulfide ( (CH ₂ = CHCH ₂ ) ₂ S (CH ₂ ) ₁₁ CH ₃ R—S—R′-type linear hydrocarbon group such as The It can be illustrated.
[0035]
The above-mentioned compounds listed as examples are examples of compounds containing an aliphatic unsaturated hydrocarbon group and a bond of S as a Group VI element, but the compounds are not limited to these, for example, aromatic A compound in which a group hydrocarbon group and an unsaturated aliphatic hydrocarbon group are bonded to a group VI element may be used. The group VI element may be Se, tellurium (Te), or the like.
[0036]
Examples of compounds containing one aromatic hydrocarbon group and an unsaturated aliphatic hydrocarbon group include benzylmethallyl sulfide (PhCH ₂ ・ S ・ CH ₂ C (CH _Three ) = CH ₂ ) And the like.
[0037]
In the hydrocarbon group represented by R or R ′, the space volume occupied by the hydrocarbon group increases as the number of carbon atoms constituting the hydrocarbon group increases. For example, a methyl group (CH _Three Compared with-), the ethyl group (CH _Three CH ₂ The space volume occupied by-) is large. When a hydrocarbon group with a large number of carbon atoms is added to a Group VI element, for example, an electrophilic reaction to the Group VI atom due to steric hindrance due to the large volume occupied by the hydrocarbon group. It becomes difficult to cause. Even if the number of carbon atoms constituting the group is the same, the branched hydrocarbon group has a larger volume of space than the straight chain hydrocarbon group. For example, as compared with a normal propyl group which is an example of a linear hydrocarbon group, an isopropyl group which is an example of a branched group has a larger spatial occupation area and is still bonded to the group VI. The effect of shielding atoms against the approaching molecule is further increased. Therefore, it has been widely used (CH _Three ) _Three Ga or (CH _Three ) _Three There is an advantage that the coupling reaction, which has been a problem in the past with an electrophilic compound with a trialkyl compound such as Al, can be suppressed.
[0038]
A compound formed by combining a branched hydrocarbon group and a Group VI element includes diisopropyl sulfide (((CH _Three ) ₂ CH ₂ ) ₂ S), diisoamyl sulfide (((CH _Three ) ₂ CHCH ₂ CH ₂ ) ₂ S) etc. can be illustrated. These are examples of R-VI-R type compounds in which the same branched hydrocarbon group is bonded to a Group VI element (the symbol VI represents a Group VI atom). RSR ′ type compounds in which different hydrocarbon groups are bonded to Group VI elements include tertiary butylmethyl (CH _Three SC (CH _Three ) _Three ), Tertiary butyl ethyl sulfide (CH _Three CH ₂ SC (CH _Three ) _Three ), Normal butyl isopropyl sulfide (CH) _Three (CH ₂ ) _Three SCH ((CH _Three ) CH _Three ), Normal butyl isobutyl sulfide (CH _Three (CH ₂ ) _Three SCH ₂ CH (CH _Three ) CH _Three ), Secondary butyl methyl sulfide (CH) _Three SCH (CH) _Three CH ₂ CH _Three ), Secondary butyl tertiary butyl sulfide (CH) _Three CH ₂ CH (CH _Three ) S (CH ₂ ) _Three CH _Three ), Secondary ibutyl isobutyl sulfide ((CH _Three ) ₂ CHCH ₂ SCH (CH _Three ) CH ₂ CH _Three ), Tertiary amyl methyl sulfide (CH) _Three CH ₂ C (CH _Three ) ₂ SCH _Three ) And the like. The above example is an example of a compound containing S as group VI, but the group VI atom is not limited to S.
[0039]
In addition, a compound having a branched hydrocarbon group and an unsaturated hydrocarbon group containing a double or triple multiple bond is also treated herein as a compound having a branched hydrocarbon group according to the present invention. For compounds in which a branched hydrocarbon group and an unsaturated aliphatic hydrocarbon group containing a double bond are bonded to a Group VI atom, allyl isopropyl sulfide (CH ₂ = CHCH ₂ SCH (CH _Three ) ₂ ), Diallyl secondary butyl sulfide (CH) ₂ = CHCH ₂ SCH (CH _Three ) CH ₂ CH _Three ), Allyl secondary butyl sulfide (CH ₂ = CHCH ₂ SCH (CH _Three ) CH ₂ CH _Three And the like. These compounds have different hydrocarbon groups bonded to each other, but for compounds in which the same hydrocarbon group is bonded to a group atom, dimethallyl sulfide ((CH ₂ = C (CH _Three ) CH ₂ ) ₂ S) etc. can be illustrated. A compound containing a branched aliphatic hydrocarbon group is a compound of the R-VI-R type or RSR 'type if classified from the structure.
[0040]
In the present invention, a compound containing a plurality of Group VI atoms in the same molecule is used as a doping source. When the hydrocarbon group bonded to the group VI atom is the same, and there are a plurality of group VI atoms in the same molecule, the total number of atoms constituting the molecule (here, (a)) ) To the total number of group VI atoms (here, referred to as (b)) ((b / a)), for example, normal heptylmethyl sulfide (CH) containing one S group VI atom _Three (CH ₂ ) ₆ ・ S ・ CH _Three ), (A) = 27 and (b) = 1, so (b / a) is about 0.037. On the other hand, although the type of the aliphatic hydrocarbon group bonded to S of the Group VI atom and the number of groups by type are the same, 2,9-dithiadecane ((CH _Three ・ S ・ (CH ₂ ) ₆ ・ S ・ CH _Three ), (A) becomes 28 due to the increase of one S atom. In this case, since (b) = 2, (b / a) = 0.071, and the constituent ratio occupied by the group VI atoms increases with respect to the number of atoms constituting the molecule. Thus, for example, if the number of moles of the compound serving as the dopant source supplied to the vapor phase growth system is the same, the group VI released from the same volume (supply amount) of molecules by, for example, thermal decomposition There is an advantage that an increase in the amount of elements is brought about. Examples of these compounds include 1,2-benzenedithiol (C _Four H ₆ S ₂ ) And other aromatic compounds, and 1,10-decanedithiol (H · S · (CH ₂ ) _Ten -H-S- (CH such as S / H) ₂ ) N-SH type (n is a positive integer of 0 or more), 2,6-dithiaheptane (CH _Three ・ S ・ (CH ₂ ) _Three ・ S ・ CH _Three R-S- (CH ₂ ) _n There are -S-R type (n is a positive integer of 0 or more) aliphatic compounds. Such a compound is an example of a compound containing a plurality of Group VI atoms in the same molecule, although it does not contain bonds between Group VI atoms.
[0041]
A compound containing a plurality of Group VI atoms in the same molecule and bonded to each other among Group VI atoms is further superior in thermal decomposability. Examples of the bond between Group VI atoms include, for example, (-S-S-) (-represents a bond), (-Se-Se-), (-Te-Te-) and the like. Saying that they are connected. Around the Group VI atoms forming such a mutual bond, electrons that do not contribute to the bonding exist as non-bonding electron pairs. If there are negatively charged electron pairs around each other group VI atom to which they are bonded, repulsion between pairs of electrons having the same negative charge occurs. This electrical repulsive force facilitates the breakage of bonds between Group VI atoms. This facilitates the decomposition of the compound and is advantageous for releasing Group VI atoms into the vapor phase growth system.
[0042]
Examples of the compound containing a plurality of Group VI atoms in the same molecule and including a bond between Group VI atoms include the following compounds (1) to (4) wherein b is 2 Can be illustrated.
(1) Dimethyl disulfide ((CH _Three ) ₂ S ₂ ), Diethyl disulfide ((CH _Three CH ₂ ) ₂ S ₂ ), Dinormalpropyl disulfide ((CH _Three (CH ₂ ) ₂ ) ₂ S ₂ ), Dinormal hexyl disulfide ((CH _Three (CH ₂ ) _Five ) ₂ S ₂ ), Dinormal heptyl disulfide ((CH _Three (CH ₂ ) ₆ ) ₂ S ₂ ) And other saturated hydrocarbon groups and diallyl disulfide ((CH ₂ = CHCH ₂ ) ₂ S ₂ ) And the like, for example, a skeleton having an unsaturated hydrocarbon group, for example, R-VI-VI-R type (symbol VI represents a Group VI atom), and an aliphatic system in which an aliphatic hydrocarbon group is added and bonded Compound. Also, diphenyl diselenide (Ph-Se-Se-Ph), dibenzyl diselenide (PhCH ₂ -Se-Se-CH ₂ Ph), dibenzyl disulfide (PhCH ₂ -S-S-CH ₂ For example, the skeleton is Ph-VI-VI-Ph type or PhCH. ₂ -VI-VI-CH ₂ Aromatic compound for Ph type.
(2) Aromatic groups are arranged symmetrically with respect to bonds between Group VI atoms such as 2,2′-dipyridyl disulfide, 4,4′-dipyridyl disulfide, di (2-thienyl) disulfide, etc. Aromatic compounds.
(3) An alicyclic compound such as dicyclohexyl disulfide.
(4) A compound having an asymmetric structure with respect to bonding between Group VI atoms, in which different hydrocarbon groups are bonded to Group VI atoms that are bonded to each other.
[0043]
In the present invention, an alicyclic compound, an aromatic compound, a derivative thereof or a substituted product thereof containing a hetero (hetero) ring is used as a dopant source. However, the derivative and the substituent do not include a substituent having a bond between a carbon atom and a nitrogen atom and a bond between a nitrogen atom and a hydrogen atom. The reason is as described above. It shall not contain oxygen atoms.
[0044]
In particular, an alicyclic compound, an aromatic compound, a derivative thereof, or a substituent thereof having a heterocycle having a group VI element as a hetero atom is used as a dopant source.
[0045]
In particular, an alicyclic compound, an aromatic compound, a derivative thereof, or a substituent thereof containing a heterocycle having a nitrogen atom and a Group VI element as a hetero atom is used as a dopant source.
[0046]
In brief, an alicyclic compound composed of a heterocyclic ring is a compound having a cyclic structure in which one hydrocarbon group is bent in a ring shape and both ends of the group are bonded to a Group VI element. One example of this compound is hexamethylene sulfide ((CH ₂ ) ₆ S) and the like. When there is one group VI atom as a hetero atom, a methylene group (CH ₂ -) Etc. are bonded. Since the hydrocarbon group is generally an electron donating group, the electron density around the methylene groups at both ends and the hetero atom increases. There are also non-bonding electron pairs of Group VI atoms around the Group VI heteroatoms. Due to this electron pair and the deviation of the electron density in the hydrocarbon group constituting the ring, an electric repulsion occurs between the heteroatom and both ends of the hydrocarbon group constituting the ring, and the heteroatom and the hydrocarbon Is broken. Thereby, there is an advantage that the heterocycle is broken and the heteroatom is easily released.
[0047]
In the same manner as described above, a hetero (hetero) cyclic alicyclic compound including a hetero (hetero) ring having a plurality of group VI atoms of periodic periodicity as atoms constituting the ring, and its substitute, It is easy to cleave with the bonded methylene group or the like. Therefore, there is an advantage that hetero atoms can be easily released. Further, if a plurality of Group VI heteroatoms are included, the number of non-bonded electron pairs present around the Group VI atoms increases. Thereby, there is an advantage that the molecule is further easily cleaved by repulsion between electron pairs existing in the molecule. Examples of these compounds are Dithianes. A homologue such as 1,3-dithiane or 1,4-dithiane or a phenyl group added to dithiane, for example, an alicyclic compound having a 6-membered ring structure such as 2-phenyl-1,3-dithiane, Examples thereof include alicyclic compounds having a 5-membered ring structure such as dithiolane. Dithianes and dithiolanes are heterocycles containing two S atoms as ring constituent atoms, but even if they are other group VI elements such as Se, regardless of the group VI atoms constituting the heterocycles. I do not care. Also, the group VI constituent atoms constituting the heterocycle may be different.
[0048]
In the present invention, an aromatic heterocyclic compound having a hetero ring containing a group VI element as a constituent atom of at least one ring, a derivative thereof, or a substituent thereof is used as a dopant source. However, the derivative and the substituent do not include a substituent having a bond between a carbon atom and a nitrogen atom and a bond between a nitrogen atom and a hydrogen atom. This is because there is an advantage that decomposition of the compound is facilitated by an electric repulsive force between a π electron existing in the ring and a non-bonded electron pair of the Group VI hetero atom.
[0049]
This includes thiophene having a heterocycle containing S (Thiophen: C _Four H _Four S). Thiophene derivatives added with aliphatic hydrocarbon groups such as 2-mercaptothiophene, 2,5-dimethylthiophene, and normal amylthiophene, and aromatic groups containing phenyl groups such as 2-phenylthiothiophene and 3-phenylthiothiophene Examples are compounds.
[0050]
Further, a compound containing a plurality of heterocycles containing S corresponds to an aromatic heterocyclic compound having a heterocyclic ring containing a Group VI element as a constituent atom of at least one ring, and a derivative or substituted product thereof. These include, for example, 3,4-dimethylthienothiophene, 2,2′-dithienyl and 3,3′-dithienyl with a 5-membered heterocycle containing two S as heteroatoms.
[0051]
In addition, aromatic compounds having a structure in which a 5-membered ring and a 6-membered ring are condensed such as 3-methylbenzothiophene and 5-methylbenzothiophene can also be exemplified.
[0052]
In addition, compounds having a structure in which two 6-membered rings and one 5-membered ring are condensed, such as dibenzothiophene, can also be exemplified. Examples of the compound consisting of a heterocyclic ring containing selenium (Se) containing a Group VI element other than S include 2,5-dimethylbenzselenazole. There are no restrictions on the type of group VI atom constituting the heterocycle and the number or quantity of the ring attached to the heterocycle.
[0053]
In vapor phase growth of nitrogen-containing III-V compound semiconductor layers such as GaN, AlN, InN, or mixed crystals thereof, NH is used as described above. _Three Is frequently used as an N source. NH _Three Therefore, the growth of these nitrogen-containing group III-V compound semiconductor layers has been conventionally carried out usually at a high temperature of about 1000 ° C. and at a minimum of about 800 ° C. At such a high temperature, N volatilization from the growth layer also becomes intense, resulting in a nitrogen-containing III-V compound semiconductor layer that is stoichiometrically unbalanced. In the present invention, a compound containing a nitrogen atom as a hetero atom and a group VI element is obtained in order to obtain a conductive layer that overcomes the conventional situation and is excellent in stoichiometry and exhibits n-type conduction. It is used as a dopant source for group atoms.
[0054]
Examples of typical compounds containing both N atom and Group VI atom according to the present invention are illustrated in the following 6 items.
[0055]
A compound having an aromatic heterocycle containing one N atom as a heteroatom and a group containing a Group VI atom such as a mercapto group (-SH), etc., and having only a 6-membered heterocycle Mercaptopyridine and the like.
[0056]
A compound comprising an aromatic heterocycle containing two N atoms as a heteroatom and a group containing a Group VI atom such as a mercapto group (-SH) or a Group VI atom, for example, a 5-membered ring 2-mercaptoimidazole having a structure, 2-mercapto-1-methylimidazole having an alkyl substituent of imidazole, 2-mercaptobenzimidazole having a condensed structure of a 5-membered ring and a 6-membered ring, and an alkyl-substituted product Imidazoles such as 2-mercapto-5-methylbenzimidazole.
[0057]
Pyrimidines such as 2-mercaptopyrimidine, 4,6-diamino-2-mercaptopyrimidine, and 4,6-diamino-2-methylmercaptopyrimidine having a 6-membered ring structure.
[0058]
A compound comprising an alicyclic heterocycle having one N atom as a heteroatom and a group VI atom or a group containing a group VI atom.
[0059]
A compound comprising an alicyclic heterocycle having two N atoms as heteroatoms and a group VI atom or a group containing a group VI atom. As an example, 2-imidazolidinethione containing a double bond between an alicyclic heterocycle containing two N heteroatoms and an S atom outside the ring.
[0060]
3-mercapto-, which is a compound having a heterocycle having three or more N atoms as heteroatoms and a group VI atom or a group containing a group VI atom, and having a mercapto (-SH group) as an example Triazoles such as 1,2,4-triazole and 3-mercapto-4-methyl-1,2,4-triazole.
[0061]
In the present invention, a compound containing both a nitrogen atom and a Group VI element as a hetero atom constituting a ring is used as a doping source for the reasons described above. Examples of representative compounds are shown in the following 4 items.
[0062]
This is an aromatic heterocyclic compound containing one N heteroatom and one group VI atom such as S or Se as a heteroatom, such as 2-mercaptothiazole, 2-isopropyl-4 -There are heterocyclic compounds with a 5-membered ring structure such as methylthiazole.
[0063]
For example, thiazoles such as 2-mercaptobenzothiazole and 2-mercapto-4-phenylthiazole having a condensed structure of a 5-membered heterocycle and a 6-membered ring group, and 2-mercaptobenzselenazole (C ₇ H _Four Selenazoles such as NSe-SH.
[0064]
For example, thiazolines such as 2-mercaptothiazoline containing one double bond in the ring.
[0065]
A compound having a heterocycle having two N heteroatoms and one Group VI atom as heteroatoms. For example, thiadiazoles such as 4,5-diphenyl-1,2,3-thiadiazole, 2-mercapto-5-methyl-1,3,4-thiadiazole, and 2,5-dimercapto-1,3,4-thiadiazole.
[0066]
The above description is a classification example for convenience based on the structure of a functional group or a heterocyclic ring, and includes, for example, an aromatic heterocyclic ring containing one N atom as a hetero atom and a mercapto group (-SH). 2-mercaptopyridine can also be classified as a compound containing two Group VI atoms identical to one N atom. Similarly, 2-mercaptobenzselenazole (C) which is an aromatic heterocyclic compound containing one N heteroatom and one group VI atom such as S or Se as a heteroatom. ₇ H _Four NSe-SH) or the like is a compound containing two Group VI atoms different from one N atom when attention is paid to the number of atoms constituting the NSe-SH).
[0067]
The above-described compounds or derivatives or substitutes thereof do not contain an oxygen atom. When oxygen atoms are released into the vapor phase growth reaction system with the decomposition of these compounds, for example, oxidizable (CH _Three ) _Three This is because Al and the like are oxidized, so that growth of an AlN film or an AlGaN mixed crystal film having a good film quality is hindered. For example, a compound containing a branched hydrocarbon group is diisobutylsulfone ((CH _Three ) ₂ CHCH ₂ ) ₂ S ₂ O ₂ A compound containing an oxygen atom such as) is not preferred. Even compounds having an aromatic heterocycle containing one N atom as a heteroatom and a mercapto group (-SH), such as 2,8-dimercapto-6-hydroxypurine, etc. A compound in which a hydroxyl group (OH-) containing an oxygen atom is added as a substituent is not preferred.
[0068]
When the group VI atom is doped into the nitrogen-containing group III-V compound semiconductor layer by vapor deposition, there is no particular limitation on the growth method of the compound semiconductor layer. Conventional MOVPE methods and VPE growth methods can be used. A growth method such as a molecular beam epitaxy (MBE) method or a chemical beam epitaxy (CBE) method can also be used. There are MBE methods such as gas source (GS) MBE and organic metal (MO) MBE depending on the form of the raw material used, but any of them can be used. There is no limitation on the Ga, Al, In, or N raw material for growing the nitrogen-containing III-V compound semiconductor layer.
[0069]
For example, the MOCVD method is broadly classified into a normal pressure method in which the growth reaction is performed under substantially atmospheric pressure (normal pressure) and a reduced pressure method in which the growth reaction is performed under reduced pressure. In any method, the growth of the nitrogen-containing group III-V compound semiconductor layer is conventionally performed in a temperature range of about 300 ° C. to about 1000 ° C. Therefore, doping can also be performed in this temperature range. . Sufficient thermal energy is given to desorb hydrocarbon groups etc. from group VI elements, and from the viewpoint of suppressing the generation of extra fragments due to desorbed hydrocarbon groups etc. at higher temperatures than necessary. For example, the doping temperature is preferably in the range of about 400 ° C. to about 800 ° C. In addition, in doping using the compound according to the present invention, it is not necessary to uniformly set the doping temperature (growth temperature). You can change the temperature. Further, in the case where a nitrogen-containing III-V compound semiconductor layer using the compound according to the present invention as a doping source is provided as one constituent layer of a laminated structure, the temperature at which the doping layer is provided and the other laminated structure constituent layers The growth temperature may be the same or different.
[0070]
When the compound according to the present invention is used as a doping source, a number of techniques can be used for its usage. For example, if the compound according to the present invention is liquid at room temperature, it can be supplied as a doping source into the vapor phase growth reaction system by performing a bubbling operation with an inert gas such as hydrogen, nitrogen or argon. The compound that performs the bubbling operation may be a simple substance or a mixture of the compounds according to the present invention. Moreover, you may dilute and use the compound concerning this invention to a suitable density | concentration. For example, a gas (gas) containing the compound according to the present invention at a concentration of about several ppm to several percent may be used as the doping source.
[0071]
There is no specific method for adding a doping source comprising the compound according to the present invention to the vapor phase growth reaction system. For example, in a general MOCVD or VPE facility, the starting material vapor or the like may be merged with a carrier gas such as hydrogen for transporting it into the reactor. In this case, there is no restriction on the position where the doping source is joined to the pipe or the like through which the carrier gas flows. Moreover, you may make it reach | attain to a reaction furnace independently, without making it merge with carrier gas etc.
[0072]
Benzyl 2-chloroethyl sulfide (PhCH ₂ S (CH ₂ ) ₂ Cl), halogen substitution products such as 2,3,4-tribromothiophene and 2,3,5-tribromothiophene are not suitable for the MOVPE method among the vapor phase growth methods, but are suitable for the halogen VPE and hydride VPE methods. It can be used as a dopant for Group VI elements.
[0073]
The compound according to the present invention is used as a doping source for the group VI element, and is grown by the vapor phase growth method exemplified above, and the carbon concentration to which the group VI element is added is 8 × 10 8. ¹⁶ cm ^-3 A semiconductor device is configured using the following nitrogen-containing III-V compound semiconductor layer. As a result of intensive studies by the present inventor, for example, conventional (CH _Three ) _Three Ga / NH _Three / H ₂ In the gas phase reaction system, H ₂ When a GaN film was obtained using S as a doping source of S, the carbon concentration in the film was 8 × 10 ¹⁶ cm ^-3 The degree became high. The mechanism of carbon contamination is not fully understood, but Lewis basic H ₂ S and Lewis acidic (CH _Three ) _Three It was presumed that the methyl radical that was eliminated during the formation of the complex due to the electron accepting / donating reaction with Ga was the source of carbon contamination.
[0074]
On the other hand, the compound according to the present invention has an advantage that the complex formation reaction with the Lewis acidic substance is suppressed in the first place due to the steric hindrance effect of the hydrocarbon group bonded to the Group VI element or the conjugation effect in the ring. . In addition, an aromatic ring group or an alicyclic hydrocarbon group, etc. added to a Group VI element, in the compound, an aromatic ring group or an alicyclic hydrocarbon group released from the Group VI element, etc. Since it is easy to form a thermally stable compound, a fragment containing carbon such as a radical is hardly generated. Thereby, in the compound according to the present invention, the degree of carbon contamination in the nitrogen-containing group III-V compound semiconductor growth layer can be suppressed, and the carbon concentration in the layer can be reduced to 8 × 10. ¹⁶ cm ^-3 The following can be suppressed. In the growth layer in which the carbon concentration is suppressed to a low level, the impurity concentration in the layer is reduced, so that there is an advantage that an improvement in electrical characteristics such as an improvement in electron mobility is brought about. In addition, since the concentration of carbon atoms remaining in the layer is suppressed to a low level, when carbon is intentionally added, the residual carbon concentration with respect to the carbon concentration to be doped is reduced even when a low concentration carbon doping is performed. The ratio is reduced, so that the variation of the total carbon atom concentration in the layer due to the residual carbon concentration of the total carbon concentration represented by the sum of the residual carbon concentration and the doping carbon concentration can be reduced.
[0075]
In the present invention, the carbon concentration is 8 × 10. ¹⁶ cm ^-3 For example, a semiconductor device such as a field effect transistor or a light-emitting diode is configured using a nitrogen-containing III-V compound semiconductor layer to which a Group VI element is added. Carbon concentration is 8x10 ¹⁶ cm ^-3 If it becomes below, the transparency of a nitrogen-containing III-V compound semiconductor layer will not be impaired. Further, if the carbon concentration is lower than this concentration, for example, the mobility is not significantly reduced. In the field effect transistor using the layer whose electron mobility is improved by reducing the carbon concentration in the layer as described above, the FET characteristics such as mutual conductance are improved.
[0076]
【Example】
Example 1
The present invention will be described based on an example in which an AlN layer formed by adding Se as a Group VI element is obtained by a vapor phase growth method.
FIG. 3 shows a schematic diagram of the vapor phase growth equipment used for the MOCVD growth described in this example.
[0077]
As a Se doping source (101), diphenyl diselenide (C ₆ H _Five -Se-Se-C ₆ H _Five ; Ph · Se · Se · Ph) was used. Ph, Se, Se, and Ph were stored in a stainless steel container (102) having an internal volume of about 150 cc. The temperature of the container (102) for storing Ph, Se, Se, and Ph was maintained at 75 ° C by a thermostatic bath (107) in order to liquefy Ph, Se, Se, and Ph having a melting point of about 62 ° C. The material, internal volume, and set temperature of the container (102) are not limited to the above values.
[0078]
(103) is trimethylaluminum ((CH _Three ) _Three Al). (CH _Three ) _Three Al was stored in a stainless steel container (104). (CH _Three ) _Three The container for Al (104) was kept at 25 ° C. by a thermostatic bath (107). The temperature of each container ((102) and (104)) containing the doping source (101) and the Al source (103) is maintained by the thermostat (107) before the substrate heating operation described later is performed. It was. The set temperature is not limited to this. As a nitrogen source, liquefied ammonia gas (NH _Three ) (126) was used.
[0079]
High purity nitrogen (N) used as a raw material transfer gas (110) for Ph, Se, Se, and Ph in the container (102) ₂ ) Gas was circulated and bubbled. N used for bubbling ₂ The gas flow rate was set to 150 cc / min. Gas for bubbling Ph, Se, Se, and Ph as a doping source of a group VI element is not necessarily N. ₂ However, the present invention is not limited thereto, and may be an inert gas such as hydrogen gas or argon gas, or a mixed gas obtained by mixing them. (CH in container (104) _Three ) _Three In Al (103), high-purity hydrogen gas used as a raw material carrying gas (110) was circulated at a flow rate of 25 cc / min and bubbled. Ph, Se, Se, Ph and (CH _Three ) _Three Al bubbling operation was started about 30 minutes before the heating operation of the substrate (115) described later.
[0080]
Before the start of AlN film formation on the substrate, Ph, Se, Se, Ph, and (CH _Three ) _Three The raw material transfer gas (110) containing Al vapor passes through the pipes ((113-1) and (113-2)) corresponding to the respective raw materials, and the valves ((114-2) in the open state). And (114-4)) to the exhaust pipe (112).
[0081]
After placing a {0001} -plane-oriented sapphire (single crystal alumina) substrate as a substrate (115) on a heating body (117) in the growth reaction vessel (108), piping (111) is placed in the growth reaction vessel (108). ) Through which hydrogen carrier gas (109) was introduced. The flow rate of the hydrogen carrier gas (109) was 7.0 l / min. Twenty minutes after the introduction of the hydrogen carrier gas (109) into the growth reaction vessel (108) was started, energization of the heating body (117) was started and the substrate (115) was heated to 700 ° C. The pressure in the growth reaction vessel (108) was almost atmospheric pressure.
[0082]
After the temperature of the substrate (115) reaches 700 ° C. and held for 20 minutes, the valves ((114-2) and (114-4)) are switched from the open state to the closed state, and conversely, the valve ((114- 1) and (114-3)) are opened from the closed state, and the above-mentioned Ph · Se · Se · Ph and (CH _Three ) _Three A raw material carrying gas (110) containing Al was introduced into the pipe (111) and merged with the hydrogen carrier gas (109). NH as N source at the same time _Three The gas (126) was introduced into the pipe (111) using the pipe (125) and merged with the hydrogen carrier gas (109). NH _Three The flow rate of the gas (126) is V / III ratio, ie NH to the reaction vessel (108). _Three / (CH _Three ) _Three The Al supply ratio was set to about 1000.
[0083]
While maintaining the temperature of the substrate (115) at 700 ° C. and maintaining the pressure in the growth reaction vessel (108) at almost atmospheric pressure, the hydrogen carrier gas (109) containing this raw material component is introduced into the growth reaction vessel (108). Was introduced into the gas nozzle (118) provided above the substrate (115) and continuously supplied to the surface of the sapphire C-plane substrate (115) for 40 minutes.
[0084]
By the above vapor phase growth operation, an AlN growth layer in which Se having a thickness of about 0.14 μm was added on the sapphire substrate (115) was obtained. From the result of semi-quantitative analysis by secondary ion mass spectrometry (SIMS), the total concentration of Se atoms in the AlN growth layer is 10 ¹⁸ cm ^-3 It was near. The AlN growth layer exhibited n-type conduction, and the sheet resistance at room temperature was about 2800 Ω / □. Carbon concentration is 3 × 10 ¹⁵ cm ^-3 Met. This sheet resistance is about an order of magnitude lower than the value obtained at the same V / III ratio as in the present example using conventional Si as a dopant. Compared with the conventional example, the doping efficiency is improved. It was accepted.
[0085]
Ph, Se, Se, Ph and (CH _Three ) _Three Al-containing bubbling gas and NH _Three The mixing order when the hydrogen gas containing hydrogen is merged with the hydrogen carrier gas is not limited to the flow chart shown in FIG. 3, and may be mixed in any order.
[0086]
(Example 2)
The present invention will be described in detail based on an example in which a light emitting diode (LED) as an example of a semiconductor device is configured. FIG. 4 shows a schematic view of atmospheric pressure MOCVD vapor phase growth used to obtain a laminated structure for LED applications of this example. FIG. 5 is a schematic sectional view of an LED according to the present invention. The substrate (115) was an aluminum (Al) disk having a diameter of about 62.5 mm. The thickness of the substrate (115) was about 500 μm.
[0087]
On the surface of the substrate (115), a GaN layer (121) doped with sulfur (S), an AlGaN layer (122), an AlGaN layer (124) and a GaN layer (123) are sequentially formed by an atmospheric pressure MOCVD method. Deposited.
[0088]
As a doping source (101) of S, diallyl sulfide (CH) consisting of a bond of an allyl group containing a double bond of a carbon atom as a hydrocarbon group and an S atom. ₂ = CHCH ₂ -S-CH ₂ CH = CH ₂ ) Was used. Diallyl sulfide was stored in a stainless steel bubbler container (102). The temperature of the container (102) was kept at 70 ° C. by a thermostatic bath (107).
[0089]
Each of the Al source (103) and the Ga source (105) includes (CH _Three ) _Three Al and (CH _Three ) _Three Ga was used. (CH _Three ) _Three Al in a stainless steel bubbler container (104), (CH _Three ) _Three Ga was individually stored in a stainless steel bubbler container (106). The container (104) for storing the Al source was kept at 25 ° C. by a thermostatic bath (107). The container (106) for storing the Ga source was kept at 0 ° C. by the thermostatic bath (107). As the nitrogen source (119), pyrrole was used. The nitrogen source was stored in a stainless steel container (120) and kept at 60 ° C. by a thermostatic bath (107). The temperature of each container ((104), (106) and (120)) containing the Al source (103), Ga source (105) and N source (119) is set in advance before the substrate heating operation described later is performed. , And kept stable at each of the above temperatures. The set temperature is not limited to this. In the present example, all the raw materials of the Group III and Group V elements were used in a liquid state, but the usage form of the raw materials is not limited to this.
[0090]
Before the start of film formation of the GaN layer (121) to which S, which is a group VI element, is added on the substrate (115), a diallyl sulfide dopant source (101), an Al source (103), Ga In the container that houses the source (105) and the N source (119), high-purity hydrogen (H ₂ ) Gas was circulated and bubbled. H used for bubbling ₂ The gas flow rates were 120 cc / min for the dopant source (101), 55 cc / min for the Al source (103), 35 cc / min for the Ga source (105), and 180 cc / min for the N source (119), respectively. I set it. The raw material transfer gas (110) accompanied by the vapor of each raw material passes through the pipes ((113-1) to (113-4)) corresponding to the respective raw materials, and the valve ((114-2), (114-4), (114-6), and (114-8)) were passed through and circulated through the exhaust pipe (112). The gas to be bubbled is not necessarily H ₂ However, the present invention is not limited thereto, and may be an inert gas such as nitrogen gas or argon gas, or a mixed gas obtained by mixing them. These bubbling operations started about 30 minutes before the heating operation of the substrate (115) described later. Hydrogen was circulated as a carrier gas at a flow rate of 7 liters in the pipe (111) for circulating the carrier gas communicating with the reactor (108).
[0091]
The temperature of the substrate (115) placed on the heating body (117) in the growth reaction vessel (108) reaches 680 ° C. from room temperature by starting energization of the resistance heating type heating body (117). The temperature was raised to. After 20 minutes have passed since reaching the same temperature, the valve (114-8) is changed from the open state to the closed state, and conversely, the valve (114-7) is changed from the closed state to the open state, and the steam from the N source (119) is accompanied. The hydrogen carrier gas containing the raw material gas provided immediately above the substrate (115) in the reaction vessel (108) by joining the raw material transfer gas (110) to the hydrogen carrier gas (109) flowing through the pipe (111) (109) was passed through the gas nozzle (118) for spraying the surface of the substrate (115) and supply to the surface of the substrate (115) was started.
[0092]
Similarly, after 20 minutes have passed since the temperature of the substrate (115) reached 680 ° C., the vapor of the dopant source (101) that was circulated in the pipe (113-1) and circulated in the exhaust side pipe (112) was used. The accompanying material transfer gas (110) was merged with the hydrogen carrier gas (109) flowing in the pipe (111) by reversing the open / closed state of the valves ((114-1) and (114-2)).
[0093]
An environment is created in which a gas containing each vapor of the dopant source (101) and the N source (119) is blown to the surface of the substrate (115) through the nozzle (108). After 5 minutes, the inside of the pipe (113-3) is created. Hydrogen carrier gas (110) in the pipe (111) by reversing the open / close state of the valve ((114-5) and (114-6)) of the raw material carrier gas (110) accompanying the vapor of the circulating Ga source (105) 109). Thereby, the growth of GaN formed by adding S was started. While maintaining the pressure in the reaction vessel (108) at approximately atmospheric pressure, the film formation was continued for 40 minutes, whereby the GaN layer (121) having a film thickness of about 0.4 μm added to the substrate (115) Deposited on top.
[0094]
Thereafter, the valve (114-5) attached to the pipe (113-3) for the Ga source (105) is closed, and conversely, the valve (114-6) is opened and the Ga source (105) is again accompanied. The raw material transfer gas (110) to be conducted was led to the exhaust side pipe (112), and the supply of the Ga source (105) to the reaction furnace (108) was temporarily stopped. On the other hand, the supply of N source (119) continued.
[0095]
After the supply of the Ga source (105) to the growth reactor (108) has been suspended for 5 minutes, the Ga source is again operated by operating the valve ((114-5) and (114-6)). The raw material transport gas (110) containing (105) was joined to the hydrogen carrier gas (109). At the same time, by reversing the open / close state of the valves ((114-3) and (114-4)) attached to the pipe (113-2) with the raw material carrying gas (110) accompanied by the Al source (103), the reaction A hydrogen carrier gas (109) containing an Al source (103) was sprayed on the surface of the substrate (115) through the inside of the nozzle (118) installed in the container (108). In this state, the hydrogen carrier gas (109) also includes a dopant source (101) and an N source (119). Supply of the hydrogen carrier gas (109) containing the dopant source (101), Al source (103), Ga source (105), and N source (119) to the surface of the substrate (115) was continued for 30 minutes. . As a result, an AlGaN layer (122) having a thickness of about 0.4 μm formed by adding S was grown. The concentration of S atoms in the AlGaN layer (122) is about 4 × 10 according to SIMS analysis. ¹⁸ cm ^-3 Met.
[0096]
Next, the open / close state of the valves ((114-1) and (114-2)) is reversed, and the raw material transfer gas (110) containing the vapor of the dopant source (101) joins the hydrogen carrier gas (109). Stopped. That is, the supply of the dopant source (101) to the growth reaction furnace (108) was stopped. Supply of the Al source (103), Ga source (105), and N source (119) to the reactor (108) was continued. At the same time as the addition of the dopant source (101) to the hydrogen carrier gas (109) was stopped, dimethylzinc ((CH _Three ) ₂ Hydrogen gas (126) containing Zn at a concentration of about 100 ppm by volume was merged with the hydrogen carrier gas (109). The flow rate of the gas (126) is such that the concentration of Zn atoms in the AlGaN layer (124) is about 1 × 10. ¹⁸ cm ^-3 It adjusted so that it might become. The flow rate was generally 150 cc / min to 200 cc / min in this example. (CH _Three ) ₂ The supply of hydrogen gas (126) containing Zn was continued for 45 minutes, and an AlGaN layer (124) formed by adding Zn having a thickness of about 0.6 μm was deposited.
[0097]
Thereafter, the joining of the raw material transfer gas (110) containing the Al source (103) vapor to the hydrogen carrier gas (109) was stopped. N source (119) and (CH _Three ) ₂ Supply of the hydrogen gas (126) containing Zn to the growth reactor (108) was continued. After 5 minutes have passed since the supply of the Al source (103) was stopped, the raw material transfer gas (110) containing the vapors of the Ga source (105) and the dopant source (101) again merged with the hydrogen carrier gas (109). I let you. Thereby, Ga source (103) and N source (119) and (CH _Three ) ₂ A GaN layer formed by adding a hydrogen carrier gas (109) containing a hydrogen gas (126) containing Zn to the surface of the substrate (115) through the nozzle (118) in the reaction furnace (108) and adding Zn. (123) was deposited. The film thickness of the GaN layer (123) was 0.3 μm. The growth of each of the nitrogen-containing group III-V compound semiconductor layers ((121) to (124)) was performed while maintaining the pressure in the growth reaction vessel (108) at almost atmospheric pressure. For example, the growth may be performed under a reduced pressure of several torr to several hundred torr, that is, the growth may be performed by a reduced pressure MOCVD method. Moreover, there is no problem even if the growth pressure is changed for each layer.
[0098]
With the above configuration, the LED application comprising a total of four layers including the GaN layer (121) and the AlN layer (122) according to the present invention obtained by adding S as a Group VI element on the Al substrate (115). A laminated structure was obtained. The carbon atom concentration in the GaN layer and AlN layer ((121) and (122)) to which S is added is 2 × 10 according to SIMS analysis. ¹⁵ cm ^-3 Was less than. The nitrogen-containing III-V group compound species and the number of stacked layers constituting the stacked structure are not limited to this example. Further, the Group VI element added to the nitrogen-containing III-V group compound layer is not limited to S, and may be, for example, Se or Te. Further, for example, various Group VI elements such as S and Se may be added to the nitrogen-containing III-V compound layer.
[0099]
The above laminated structure was processed by applying a conventional general photolithography technique, etching technique, etc., and an LED as shown in the schematic sectional view of FIG. 5 was constructed.
The periphery of the electrode (127) on the surface side of the laminated structure is made of silicon oxide (SiO _x ). This coating film is not limited to silicon oxide, and may be composed of silicon nitride. The electrode (128) on the back surface side was made the substrate (115) itself by utilizing the good electrical conductivity of Al as the substrate (115).
[0100]
【The invention's effect】
In a nitrogen-containing group III-V compound semiconductor, by using a specific organic compound containing a group VI element as a doping source, the doping efficiency of the group VI semiconductor can be easily increased. Mixing of carbon into the layer can be suppressed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a general V / III ratio dependency of a vacancy concentration of a Group III element and a Group V element.
FIG. 2 is a diagram showing an example of V / III ratio dependence of sheet resistance of a GaN growth layer and a GaAs growth layer doped with Si.
3 is a schematic cross-sectional view of a vapor phase growth apparatus according to Example 1. FIG.
4 is a schematic cross-sectional view of a vapor phase growth apparatus according to Example 2. FIG.
FIG. 5 is a schematic cross-sectional view of a semiconductor device according to the present invention.
[Explanation of symbols]
(101) Dopand source of group VI elements
(102) Group VI element dopant source storage container
(103) Aluminum (Al) source
(104) Al source storage container
(105) Gallium (Ga) source
(106) Ga source storage container
(107) Constant temperature layer
(108) Growth reaction vessel
(109) Carrier gas
(110) Raw material transfer gas
(111) Piping to the growth reaction vessel
(112) Exhaust piping
(113-1) Piping for circulating a raw material carrying gas containing a dopant source
(113-2) Piping for circulating raw material transport gas containing Al source
(113-3) Piping for circulating a raw material carrying gas containing a Ga source
(113-4) Piping for circulating a raw material transport gas containing a nitrogen source
(114-1) Valve
(114-2) Valve
(114-3) Valve
(114-4) Valve
(114-5) Valve
(114-6) Valve
(114-7) Valve
(114-8) Valve
(115) Substrate
(116) Compound semiconductor growth layer
(117) Heating body
(118) Nozzle
(119) Nitrogen (N) source
(120) Stainless steel container for N source storage
(121) Gallium nitride (GaN) growth layer to which Group VI element is added
(122) Aluminum nitride gallium (AlGaN) growth layer to which Group VI element is added
(123) GaN growth layer
(124) AlGaN growth layer
(125) Cylinder gas piping
(126) Gas stored in a cylinder
(127) Surface electrode
(128) Back electrode
(129) A line schematically showing a change in the vacancy concentration of the group V element
(130) A line schematically showing changes in the vacancy concentration of group III elements
(131) A curve schematically showing a change in sheet resistance of a GaN growth layer doped with a group IV element
(132) A curve schematically showing a change in sheet resistance of a GaAs growth layer doped with a group IV element

Claims (6)

A method for producing a group III-V compound semiconductor device comprising at least one element of aluminum, gallium, and indium and a group V element containing at least nitrogen, wherein at least one of sulfur, selenium, and tellurium is used as a dopant material. A method for producing a group III-V compound semiconductor device, comprising using a chain hydrocarbon compound containing a seed element and a hydrocarbon group having 3 or more carbon atoms. 2. The method for producing a group III-V compound semiconductor device according to claim 1, wherein the chain hydrocarbon compound is linear. 2. The method for producing a group III-V compound semiconductor device according to claim 1, wherein the chain hydrocarbon compound is branched. A method for producing a group III-V compound semiconductor device comprising at least one element of aluminum, gallium, and indium and a group V element containing at least nitrogen, wherein at least one of sulfur, selenium, and tellurium is used as a dopant material. An aromatic hydrocarbon compound containing a seed element is used. A method for producing a group III-V compound semiconductor element. A method for producing a group III-V compound semiconductor device comprising at least one element of aluminum, gallium, and indium and a group V element containing at least nitrogen, wherein at least one of sulfur, selenium, and tellurium is used as a dopant material. A method for producing a group III-V compound semiconductor device, comprising using an alicyclic hydrocarbon compound containing a seed element. A method for producing a group III-V compound semiconductor device comprising at least one element of aluminum, gallium, and indium and a group V element containing at least nitrogen, wherein at least one of sulfur, selenium, and tellurium is used as a dopant material. A method for producing a Group III-V compound semiconductor device, comprising using a heterocyclic hydrocarbon compound containing a seed element.

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