JP6055325B2 - Method for manufacturing nitride semiconductor crystal - Google Patents

Description

  The present invention relates to a method for producing a nitride semiconductor crystal by metal organic vapor phase epitaxy.

  Nitride semiconductor materials composed of nitrogen compounds of Group III elements (B, Al, Ga, In, etc.) are light receiving / emitting devices (LEDs, semiconductor lasers, photodiodes, superluminescent diodes, phototransistors, solar cells, etc.), Electronic devices other than light emitting and receiving devices (diodes, transistors, bipolar electronic devices, unipolar electronic devices, integrated devices, etc.), electronic devices such as spintronic devices, photocatalytic devices, electron tubes, semiconductor substrates, laser media, magnetic semiconductors, fluorescence It can be applied to functional materials such as the body. In order to manufacture these devices and functional materials, it is necessary to form nitride semiconductor crystals while controlling conductivity, composition, and the like.

However, nitride semiconductor materials still have insufficient control of p-type conductivity, and there is a problem that the carrier concentration cannot be increased sufficiently. Normally, p-type conductivity of a nitride semiconductor is controlled using Mg as an acceptor impurity. For example, when the carrier concentration is increased to about 10 ¹⁸ / cm ³ , the activation rate of the acceptor impurity is several percent. It is difficult to increase the carrier concentration any more.

As a technique for tackling this problem, there is a simultaneous doping technique disclosed in Patent Document 1. The technique of Patent Document 1 is a GaN crystal growth technique using atomic N ⁺ gas obtained by irradiating an N ₂ gas source with electromagnetic waves as a nitrogen source, and acceptor impurities such as Si or O as donor impurities. Co-doping with Mg or Be.

In the technique of Patent Document 1, the impurity material is finally supplied onto the substrate as an atomic beam and taken into the GaN crystal. The atomic ratio of the acceptor impurity and the donor impurity is set to 2: 1, and doping is performed simultaneously. . A p-type acceptor (for example, Mg ⁺ _Ga ) and an n-type donor (for example, Si ⁻ _Ga ) introduced into a GaN crystal are charged to + and −, respectively, and electrostatic energy is stabilized by forming a pair. . Furthermore, when another acceptor atom is added here, it works effectively as an acceptor, enabling high-concentration doping, achieving a high carrier concentration, and also enabling efficient activation as an acceptor. is there.

JP-A-10-101696

  In normal p-type doping that controls the p-type conductivity of a nitride semiconductor using Mg as an acceptor impurity, it is difficult to increase the carrier concentration as described above. Further, the impurity level is typically deep at a value exceeding 100 meV, which is a problem because it brings about a low activation rate at room temperature and a large variation in resistivity and carrier concentration due to temperature.

  The technique disclosed in Patent Document 1 is not based on an ordinary MOCVD (Metal Organic Chemical Vapor Deposition) crystal growth method using a hydride such as ammonia as a nitrogen raw material. This crystal growth method using a hydride such as ammonia as a group V source gas is generally superior to other methods in consideration of crystal quality, controllability, reproducibility, and productivity, so it can be used for mass production of various devices. Although applied, Patent Document 1 does not disclose an effective co-doping technique in this growth technique.

  Even if the simultaneous doping technique whose principle is proposed in Patent Document 1 is applied to the MOCVD crystal growth method, it is still difficult to stably obtain a high carrier concentration and a high activation rate. It is also difficult to stably realize a p-type semiconductor crystal with a shallow impurity level.

In the nitride semiconductor crystal, the atomic density of group III element or group V element is in the middle of the order of 10 ²² / cm ³ , and this number is the number of acceptor sites that a certain acceptor atom can take. On the other hand, the acceptor concentration range that is required to be controlled in the p-type layer of the semiconductor device is about 10 ¹⁷ to 10 ²⁰ / cm ³ , and at most one acceptor atom is used in several hundreds. In the middle of 10 ¹⁸ / cm ³ , the acceptor sites are replaced in a sparse state, which is 1 or less per 10000, and distributed in the crystal.

  The principle shown in Patent Document 1 is that two acceptor atoms and one donor atom interact with each other in the crystal and stabilize, so that they are arranged at neighboring sites in the crystal. It is necessary to However, in a normal MOCVD crystal growth method using a hydride gas as a nitrogen source, an acceptor source (if Mg of the same impurity species as Patent Document 1 is used, the source gas is an organometallic compound source of Mg) and a donor source ( If Si is the same impurity species as in Patent Document 1, the source gas is controlled to flow into the growth apparatus so that Si hydride) is taken into the crystal at a predetermined atomic ratio. Even so, since the distribution of acceptor atoms (or donor atoms) is extremely sparse as described above, even if two acceptor atoms and one donor atom are conveniently incorporated so as to be arranged in the vicinity in the crystal. Absent.

Acceptor atoms and donor atoms tend to be scattered and incorporated in the crystal, and the probability of the stabilization principle proposed in Patent Document 1 is very low, resulting in an efficient doping technique. Absent. In addition, in the GaN crystal growth technique using atomic N ⁺ gas obtained by irradiating an N ₂ gas source with electromagnetic waves as a nitrogen source in Patent Document 1, there is no particular contrivance for this problem. It is estimated that there is a problem.

  An object of the present invention is to provide a method for producing a p-type nitride semiconductor crystal excellent in controllability using a metal organic vapor phase epitaxy method.

  In order to achieve the above object, the present invention provides a metal organic vapor phase growth method using a group III element organometallic compound, a hydride of nitrogen, and an organic compound having a CO—C—C partial structure as raw materials. Thus, a method for producing a nitride semiconductor crystal in which C atoms and O atoms are simultaneously incorporated into the crystal to obtain p-type conductivity is obtained.

  According to the present invention, both the C atom and the O atom in the organic compound raw material for realizing the p-type semiconductor crystal are incorporated into the N atom site that should act as an acceptor and a donor, respectively. Therefore, a manufacturing method excellent in controllability of the p-type nitride semiconductor crystal can be provided by using a metal organic chemical vapor deposition method.

It is a perspective view of the board | substrate with which the nitride semiconductor layer of 1st Embodiment was formed. It is a schematic diagram of the MOCVD apparatus used in 1st Embodiment. It is a schematic diagram of the p-type nitride semiconductor crystal produced with the conventional doping method. It is a schematic diagram of the p-type nitride semiconductor crystal produced with the doping method of 1st Embodiment. It is a figure which shows the organic compound which has the partial structure of C-O-C. It is a sequence diagram which shows the supply method of each raw material at the time of growing the p-type semiconductor crystal of 2nd Embodiment. It is a sequence diagram which shows the supply method of each raw material at the time of growing the p-type semiconductor crystal of 3rd Embodiment. It is a figure which shows the organic compound which has the partial structure of C-O-C. It is a figure which shows the organic compound which has the partial structure of C-O-C. It is a figure which shows the organic compound which has the partial structure of C-O-C.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The figure showing the wafer is a schematic diagram for showing the concept. In the figure, the length, width, thickness, etc. are appropriately changed for the sake of clarity and simplification, and the actual dimensional relationship It does not represent. In particular, the thickness is shown relatively appropriately enlarged. Moreover, in each figure, the same code | symbol is attached | subjected to the same or substantially the same structure.

  The crystal growth of the nitride semiconductor in each embodiment is performed by an MOCVD apparatus. The MOCVD apparatus has a mechanism for heating a substrate placed in the furnace, a mechanism for introducing gas into the furnace, and a mechanism for discharging gas in the furnace. In the MOCVD growth method of the nitride semiconductor in each embodiment, as a gas introduced into the furnace, a group III element organometallic compound is used as a group III element raw material, and a nitrogen hydride as a group V element raw material, for example, Use ammonia or hydrazine. Further, an organic compound having a C—O—C partial structure is used as a raw material for realizing a p-type semiconductor crystal. Further, as the gas introduced into the furnace, a gas containing a carrier gas (typically hydrogen or nitrogen) and a dopant material for realizing an n-type semiconductor crystal is also used as appropriate.

<First Embodiment>
FIG. 1 is a perspective view of a substrate on which a nitride semiconductor layer according to the first embodiment is formed. A nitride semiconductor layer 12 and a p-type nitride semiconductor layer 13 are sequentially formed on the substrate 11. The substrate 11 is composed only of a base material such as sapphire, ruby, gallium oxide, nitride semiconductor (GaN, AlN, AlGaN, etc.), SiC, ZrB ₂ , Si, etc. A material obtained by forming another material on a base material made of a material as appropriate and used as a crystal growth substrate for a nitride semiconductor can be used. The surface of the substrate 11 may be uneven or may have a mask-like film forming material. In these cases, the surface of the substrate 11 may not be uniform or flat.

  Next, a method for forming the nitride semiconductor layer 12 and the p-type nitride semiconductor layer 13 will be described. FIG. 2 is a schematic diagram of the MOCVD apparatus used in the first embodiment. The MOCVD apparatus 20 includes a furnace 21, a stage 22 provided in the furnace 21 and provided with a substrate heating mechanism, and various pipes for supplying raw materials to the furnace 21.

  First, the substrate 11 is placed on the stage 22, and the substrate 11 is heated to a predetermined temperature suitable for growing the nitride semiconductor layer 12 and maintained at that temperature. Subsequently, a nitride semiconductor layer 12 is formed on the substrate 11 by supplying a group III element material and an ammonia gas, which is a nitrogen material, using a carrier gas containing hydrogen.

  The nitride semiconductor layer 12 serves as a base layer when the p-type nitride semiconductor layer 13 is formed, and the crystallinity can be made better than when the p-type nitride semiconductor layer 13 is formed directly on the substrate. Contribute to sex control.

Subsequently, the temperature of the substrate 11 is maintained at a predetermined temperature of 900 to 1100 ° C. suitable for growing the p-type nitride semiconductor layer 13, and trimethyl, which is a group III element raw material, is used using a carrier gas containing hydrogen. Gallium (TMG), ammonia gas, which is a raw material of nitrogen, and dimethyl ether (CH ₃ —O—CH ₃ ) are supplied as raw materials for realizing a p-type semiconductor crystal, and the nitride semiconductor layer 12 is made of GaN. A p-type nitride semiconductor layer 13 is formed.

Here, dimethyl ether is an organic compound having a C—O—C partial structure. The produced p-type GaN crystal incorporated O 2 × 10 ¹⁸ / cm ³ and C 4 × 10 ¹⁸ / cm ³ . When the carrier concentration is measured at room temperature, it is about 1.5 × 10 ¹⁸ / cm ³ , and the activation rate of Mg acceptor normally used in doping of p-type impurities of GaN is only on the order of several percent. A high activation rate was obtained.

  When the activation energy of the acceptor level was evaluated by measuring the temperature dependency of the carrier concentration, it was about 2 to 70 meV in consideration of variations and errors. This is a much shallower acceptor level compared to the activation energy of Mg acceptor normally used in doping of p-type impurities of GaN exceeding 100 meV.

  When a nitride semiconductor having such an excellent p-type characteristic is used for a p-type layer of a device, for example, a p-type layer of an LED, light emission due to reduction in driving voltage and easy injection of carriers into the active layer Improved characteristics such as increased efficiency are obtained. In addition, since the acceptor level is shallow, the change in characteristics of the p-type layer due to temperature is small, and as a result, a device having excellent characteristics in which the temperature change in drive voltage and light emission efficiency is small can be realized. Such excellent p-type characteristics are advantageous not only for LEDs but also for the other types of devices described above.

  FIG. 3 is a schematic diagram of a p-type nitride semiconductor crystal produced by a conventional doping method, and FIG. 4 is a schematic diagram of a p-type nitride semiconductor crystal produced by the doping method of the first embodiment. Each figure shows only the group V atom site of the nitride semiconductor crystal.

  C atoms can replace N atoms in the nitride semiconductor crystal and become an acceptor due to lack of electrons, and O atoms can replace N atoms in the nitride semiconductor crystal and leave electrons to become donors. As shown in FIG. 3, in conventional doping, acceptor atoms (for example, C atoms) are incorporated in isolation (single doping). Even if each source gas is introduced without any special idea so that the acceptor and the donor are taken in at the same time, the existence of acceptor atoms and donor atoms is sparse, so the probability that they exist in isolation as in FIG. Is expensive.

  On the other hand, according to the growth method of the first embodiment, an organic compound having a C—O—C bond is used as a raw material for realizing a p-type semiconductor crystal. As shown in FIG. 4, C atoms and O atoms are directly taken into neighboring sites, and two charged acceptor atoms and one donor atom are taken so as to interact with each other in the crystal.

  This is referred to herein as molecular doping. This term only conceptually refers to a state in which a plurality of acceptor / donor atoms interact with each other, and is not a physically exact term, but is expressed as such for convenience.

  As described above, according to the method of the present embodiment, a phenomenon in which two acceptor atoms and one donor atom are taken into a neighboring site, that is, molecular doping occurs surely, which is disclosed in Patent Document 1. The mechanism is activated very efficiently in the crystal. That is, the two acceptor atoms and one donor atom incorporated in these neighboring sites become a total acceptor that lacks one electron and becomes an acceptor. The energy of the hole bound by is small, and therefore, a shallow acceptor with a small activation energy can be realized. As a result, high concentration doping and high carrier concentration can be realized with good reproducibility and stability, and the activation of the acceptor becomes efficient.

  In addition, having a bond in which an O atom is sandwiched between C atoms, such as C—O—C, has an important meaning in realizing efficient doping. When an O atom and a C atom are independently incorporated into a nitride semiconductor crystal, the C atom can be an acceptor, but the O atom is almost a donor. Since such a donor compensates the target p-type conductivity by the amount generated, a major problem in the p-type crystal manufacturing method by co-doping that arises because the acceptor impurity and the donor impurity are supplied simultaneously. It is. In that respect, since the raw material for realizing the p-type semiconductor crystal of the present invention is a bond in which O atoms are sandwiched between C atoms, O atoms can be separated from any C atom and incorporated. This is particularly effective in realizing efficient doping.

  Furthermore, in this embodiment, since dimethyl ether, which is an organic compound having two C atoms and one O atom, is used, two C atoms and one O atom are taken into a neighboring site as a set. Convenient.

  Moreover, when AlGaN (Al composition 1 to 100%) was used as the p-type nitride semiconductor layer 13, the p-type control superior to that of the prior art was made possible as described above. In this case, trimethylaluminum (TMA) was used as a group III element material in addition to TMG according to the Al composition. In particular, a nitride semiconductor having a high Al composition has been difficult to realize a p-type having a low resistance in the prior art, and thus the merit of the present technology is great.

  Further, when GaInN (In composition: 1 to 100%) was used as the p-type nitride semiconductor layer 13, the p-type control superior to that of the prior art was possible as described above. In this case, trimethylindium (TMI) was used as a group III element material in addition to TMG according to the In composition.

  Further, when AlInN (In composition of 1 to 99%) was used as the p-type nitride semiconductor layer 13, the p-type control superior to that of the prior art was made possible as described above. From this, the p-type nitride semiconductor layer 13 can also be expected to have excellent p-type controllability in all compositions of the compound AlGaInN.

  In this embodiment, dimethyl ether is used as an organic compound having a C—O—C bond that realizes a p-type semiconductor crystal, but has another C—O—C partial structure shown in FIG. Organic compounds may be used.

  As described above, the organic compound raw material having a C—O—C partial structure for realizing a p-type semiconductor crystal is not simply used as a raw material for incorporating a C atom as an acceptor. And O atoms are used simultaneously as raw materials for incorporating them in the vicinity in the crystal. Some crystal growth conditions desirable for realizing such a method of incorporation are shown below.

  It is desirable that the organic compound material for realizing the p-type semiconductor crystal is supplied into the furnace 21 after being diluted with a carrier gas. This is because, when supplied at a high concentration, they react with each other before reaching the substrate 11 and proper doping cannot be performed.

  The organic compound raw material is supplied as follows. In the case of an organic compound raw material that is in a gaseous state or can be supplied in a gaseous state at a predetermined temperature, it is filled in a gas cylinder, supplied with a required amount during growth, and further diluted with a carrier gas before being introduced into the furnace 21. To do. In the case of an organic compound raw material that is in a liquid state at a predetermined temperature, the cylinder is filled and kept at a constant temperature, and during the growth, the liquid is bubbled with a carrier gas to evaporate the raw material evaporated into the carrier gas in the cylinder. It is taken out and, if necessary, further diluted with a carrier gas and introduced into the furnace 21. In the case of an organic compound raw material that is in a solid state at a predetermined temperature, the cylinder is filled and kept at a constant temperature, and the carrier gas is supplied to the cylinder after the material sublimated to the carrier gas in the cylinder during growth. If necessary, it is further diluted with a carrier gas and then introduced into the furnace 21.

  It is desirable that the surface on which the p-type nitride semiconductor is grown has a predetermined off angle from the main surface of the nitride semiconductor. This is because there is an atomic step state on the surface suitable for supplying an organic compound raw material for realizing the p-type semiconductor crystal in this embodiment and incorporating both C atoms and O atoms into the crystal at the same time. It is. When the crystal growth surface is the (0001) plane, a surface having an off angle in the range of 0.05 to 0.8 ° in an arbitrary direction from the (0001) plane is preferable. It is also possible to use other crystal growth surfaces.

  Next, a specific example of manufacturing conditions in the first embodiment will be described with reference to FIG. Here, the organic compound raw material is sufficiently diluted with a carrier gas and then supplied into the furnace 21. In FIG. 2, for the supply-side piping, only the system for supplying raw materials and other gases into the furnace 21 is shown for simplification of the drawing. Actually, a line for exhausting directly to the outside of the apparatus connected by the switching valve, a line for purging the piping, and safety are ensured in order to quickly switch the gas supply into the furnace 21. A line or the like is provided, and a valve and a flow rate controller are provided as appropriate, but these are omitted in the figure.

  First, a gas cylinder prepared by diluting dimethyl ether to 1% with nitrogen is prepared. This cylinder is connected to the impurity material system connected to the group V line in FIG. When the p-type nitride semiconductor layer 13 is formed, a source gas is supplied from a cylinder and immediately further diluted with a carrier gas that is nitrogen, and then the reactor is formed in the furnace 21 through a group V source line. Impurity raw material (dimethyl ether) is supplied.

  The gas after dimethyl ether is diluted is preferably 0.01 to 10000 ppm. More preferably, the dilution is 1 to 1000 ppm. By doing so, it is possible to prevent mutual reaction in the piping before reaching the substrate 11, and good doping and control thereof are possible. In addition, the numerical value of dilution can be defined by the molar ratio of dimethyl ether and dilution gas. Further, after joining the group V raw material line, since the group V raw material, for example, ammonia is introduced into the group V line, it is further diluted. In this case, the dilution ratio is set to 1/2000 to 1/2. Preferably, it is in the range of 1/1000 to 1/2.

In addition, the supply amount of dimethyl ether is preferably 1 / 10,000,000 or less and 1/100 or less of the supply amount of the group III raw material when forming the p-type nitride semiconductor layer 13. By doing so, appropriate doping becomes possible. A more preferable range is 1 / 100,000 or more and 1/1000 or less. By doing so, it becomes possible to control the carrier concentration of the p layer suitable as a component of the electronic device to about 10 ¹⁷ to 10 ²⁰ / cm ³ .

  In addition, although nitrogen was illustrated as a gas which dilutes an impurity raw material, the gas generally used as carrier gas, such as inert gas, such as helium and argon, and hydrogen, can also be used.

Second Embodiment
In the second embodiment, when the p-type semiconductor crystal is grown, the supply amount of the organic compound raw material is synchronized with periodically changing the supply ratio of the hydride of nitrogen that is the V group raw material and the III group raw material. A method of periodically changing is used.

  This is done as follows. When growing the p-type semiconductor crystal, the supply ratio of the hydride of nitrogen, which is a group V material, and the III material is periodically changed. This is performed alternately between a first period in which group III elements are preferentially arranged on the growing crystal surface and a second period in which group V atoms (N atoms) are preferentially arranged on the growing crystal surface. Then, in accordance with the second period, the crystal growth of the nitride semiconductor is performed by supplying the organic compound or increasing the supply amount of the organic compound.

  In other words, the organic compound material is supplied in a relatively small amount in the first period in which the supply ratio of the group III element is relatively large, and is supplied in a relatively large amount in the second period in which the supply ratio of the group V material is relatively large. Is.

  As a result, both the C atom and the O atom in the organic compound raw material for realizing the p-type semiconductor crystal are surely taken in by the group V atom (N atom) site that should act as an acceptor and a donor, respectively. Therefore, a mechanism for expressing good p-type controllability works effectively.

  A method of supplying each raw material when growing the p-type semiconductor crystal of the present embodiment will be described more specifically using the sequence of FIG. Group III raw materials are supplied periodically and intermittently by having a first period with a large supply amount (IIImax) and other periods as a period with a small supply amount (IIImin). IIImin is preferably 0, but may be a sufficiently small supply amount, for example, a supply amount greater than 0 and not more than one fifth of IIImax.

  Group V raw materials are supplied periodically and intermittently by having a second period in which the supply amount is large (Vmax) during IIImin and making the other period a period with a small supply amount (Vmin). . Vmin is preferably 0. However, in order to suppress the elimination of the group V element, the supply amount may be greater than 0 and equal to or less than 1/5 of Vmax.

  Here, the first period and the second period are completely separated, and correspond to period A and period B in FIG. With the above sequence, so-called alternate supply is realized. Although only about two cycles are shown in FIG. 6, in practice, a very large number of cycles are repeated.

  The supply amount of the organic compound raw material for realizing the p-type semiconductor crystal is increased (Dmax) in accordance with (according to) the second period. In other periods, the supply amount is reduced (Dmin). Dmin is preferably 0, but can be a non-zero value considerably less than Dmax. Thereby, the organic compound raw material for realizing the p-type semiconductor crystal is substantially supplied in the second period, and C atoms and O atoms contained therein are taken into the group V site.

  Thus, the C atom in the organic compound raw material for realizing the p-type semiconductor crystal substitutes the group V atom (N atom) of the nitride semiconductor crystal to become an acceptor, and the O atom is a nitride. Impurity atoms that can substitute for V-group atoms (N atoms) in the semiconductor crystal and leave electrons to become donors, both of which are incorporated into the V-group site, and thus the mechanism of this embodiment is manifested. Therefore, since it is only necessary to operate these atoms so as to be easily incorporated into the group V site at the same time, the organic compound raw material for realizing the p-type semiconductor crystal is very compatible with the alternate supply growth method. Therefore, according to the present embodiment, an effectively good p-type nitride semiconductor crystal can be realized more stably and with good reproducibility.

  Note that the sequence shown in FIG. 6 shows an example, and the specific method of implementation is not limited to this. In the present embodiment, a period during which the supply of any raw material is small (or absent) is provided between the first period and the second period, but this period is not essential. For example, the supply of the group V raw material may be decreased and the supply of the group III raw material may be increased at the same time, or there may be a slight overlap time. In addition, the supply of the group III raw material may be reduced, and at the same time the supply of the group V raw material may be increased, or there may be a slight overlap time.

  In the present embodiment, the supply of the p-type impurity material is matched with the increase or decrease of the supply of the group V material, but this is not essential. There may be a time when a large amount of the p-type impurity material is supplied when a large amount of the group V material is supplied, and there may be a deviation in the increase / decrease timing. Furthermore, in the alternate supply method, a method is also known in which a certain amount of Group V material is supplied and only a Group III material is intermittently supplied (Vmax = Vmin in FIG. 6). Even in such a case, if there is a time when a large amount of the p-type impurity material is supplied in a period in which the supply ratio of the group V material is relatively large, it can be regarded as a variation of the present embodiment.

<Third Embodiment>
In the third embodiment, the timing for supplying the organic compound in the second embodiment is changed. This is done as follows. When growing the p-type semiconductor crystal, the supply ratio of the hydride of nitrogen, which is a group V material, and the III material is periodically changed. This is performed alternately between a first period in which group III elements are preferentially arranged on the growing crystal surface and a second period in which group V atoms (N atoms) are preferentially arranged on the growing crystal surface. The crystal growth of the nitride semiconductor is performed by supplying an organic compound or increasing the supply amount of the organic compound from the first period and the subsequent second period to before the second period.

  In other words, the organic compound raw material is relatively small in the first period in which the supply ratio of the group III element is relatively large and the second period in which the supply ratio of the group V raw material is relatively large. A relatively large amount is supplied during this period.

  Thereby, before the group V element reaches the site, both C atom and O atom are incorporated into the group V atom (N atom) site in an appropriate amount. Therefore, a mechanism that exhibits good p-type controllability works effectively.

  A method of supplying each raw material when growing the p-type semiconductor crystal of the present embodiment will be described more specifically using the sequence of FIG. Group III raw materials are supplied periodically and intermittently by having a first period with a large supply amount (IIImax) and other periods as a period with a small supply amount (IIImin). IIImin is preferably 0, but may be a sufficiently small supply amount, for example, a supply amount greater than 0 and not more than one fifth of IIImax.

  Group V raw materials are supplied periodically and intermittently by having a second period in which the supply amount is large (Vmax) during IIImin and making the other period a period with a small supply amount (Vmin). . Vmin is preferably 0. However, in order to suppress the elimination of the group V element, the supply amount may be greater than 0 and equal to or less than 1/5 of Vmax.

  Here, the first period and the second period are completely separated, and correspond to period A and period B in FIG. With the above sequence, so-called alternate supply is realized. Although only about two cycles are shown in FIG. 7, actually, a very large number of cycles are repeated.

  The supply amount of the organic compound raw material for realizing the p-type semiconductor crystal is increased (Dmax) during the first and second periods. In other periods, the supply amount is reduced (Dmin). Dmin is preferably 0, but can be a non-zero value considerably less than Dmax. Thus, prior to the period in which the group V atoms are preferentially arranged on the growth surface with respect to the growth surface to which the group III atoms are sufficiently supplied during the first and second periods, the p-type semiconductor crystal is formed. The organic compound raw material for realization will be supplied, and the C atom and O atom contained therein are incorporated into the group V site. Therefore, according to the present embodiment, an effectively good p-type nitride semiconductor crystal can be realized more stably and with good reproducibility.

  Note that the sequence shown in FIG. 7 shows an example, and the specific method of implementation is not limited to this. In the present embodiment, a period during which the supply of any raw material is small (or absent) is provided between the first period and the second period, but this period is not essential. For example, the supply of the group V raw material may be decreased and the supply of the group III raw material may be increased at the same time, or there may be a slight overlap time.

  In the present embodiment, the supply of the p-type impurity material may be shifted in the increase / decrease timing. In particular, it is reasonable that the reduction to Dmin may be extended to the time when the group V raw material is reduced or slightly beyond that in view of the purpose of promoting the incorporation of the impurity raw material into the group V site. . Therefore, in the third embodiment, the first period and the second period are alternately performed, and the organic compound is formed between the first period and the subsequent second period until the second period and the subsequent first period. Alternatively, the crystal growth of the nitride semiconductor may be performed by supplying or increasing the supply amount of the organic compound.

  Furthermore, in the alternate supply method, a method is also known in which a certain amount of Group V material is supplied and only a Group III material is intermittently supplied (Vmax = Vmin in FIG. 7). Even in such a case, if there is a period when a large amount of the p-type impurity material is supplied in a period in which the supply ratio of the group III material is relatively small, it can be regarded as a variation of the present embodiment.

<Fourth embodiment>
The fourth embodiment uses ethylene oxide (C ₂ H ₄ O) as a doping material for realizing a p-type semiconductor crystal in any one of the first to third embodiments. In this case as well, good p-type controllability was obtained. Ethylene oxide has a C—O—C bond and is a cyclic bond. This cyclic bond consists of three atoms, C, O, and C. Therefore, the possibility that O atoms are isolated and taken in during crystal growth becomes very low, and the effect of molecular doping is more effectively exhibited.

  Ethylene oxide is a compound containing 2 C atoms and 1 O atom, and no extra C atoms or O atoms exist due to molecular doping. Therefore, the molecular doping effect is more effectively exhibited. In this embodiment, ethylene oxide is used as an organic compound having a C—O—C bond that realizes a p-type semiconductor crystal. However, oxylene and other C—O—C partial structures illustrated in FIG. You may use the organic compound which has.

<Fifth Embodiment>
The fifth embodiment uses diepoxybutane (C ₄ H ₆ O ₂ ) as a doping material for realizing a p-type semiconductor crystal in any one of the first to third embodiments. In this case as well, good p-type controllability was obtained. The diepoxybutane has a C—O—C bond, and further has two cyclic bonds composed of three atoms of C, O, and C. Further, diepoxybutane is a compound containing 4 C atoms and 2 O atoms, and no extra C atoms or O atoms exist for molecular doping. Therefore, the molecular doping effect is more effectively exhibited. In this embodiment, diepoxybutane is used as an organic compound having a C—O—C bond that realizes a p-type semiconductor crystal. However, 2-acetyloxirane and other C—O—C partial structures are used. You may use the organic compound which has.

<Sixth Embodiment>
In the sixth embodiment, 1,4-dioxane (C ₄ H ₈ O ₂ ) is used as a doping material for realizing a p-type semiconductor crystal in any of the first to third embodiments. In this case as well, good p-type controllability was obtained. In this embodiment, and in this embodiment, 1,4-dioxane is used as an organic compound having a C—O—C bond that realizes a p-type semiconductor crystal, but 2,3-dihydro-1 , 4-dioxin and other organic compounds having the C—O—C partial structure exemplified in FIGS. 9 and 10 may be used.

<Seventh embodiment>
The seventh embodiment uses methyl ethyl ether (CH ₃ —O—CH ₂ —CH ₃ ) as a doping material for realizing a p-type semiconductor crystal in any of the first to third embodiments. is there. In this case as well, good p-type controllability was obtained. In this embodiment, and in this embodiment, methyl ethyl ether is used as an organic compound having a C—O—C bond that realizes a p-type semiconductor crystal, but diethyl ether, methyl propyl ether, methyl isopropyl is used. Ether and other organic compounds having other C—O—C partial structures may be used.

<Eighth Embodiment>
In an eighth embodiment, 3-methoxypropanal (C ₄ H ₈ O ₂ ) is used as a doping material for realizing a p-type semiconductor crystal in any of the first to third embodiments. In this case as well, good p-type controllability was obtained. In this embodiment, 3-methoxypropanal is used as an organic compound having a C—O—C bond that realizes a p-type semiconductor crystal. However, methoxyacetone, 1,2-dimethoxyethane, and other C compounds are used. An organic compound having a partial structure of —O—C may be used.

  In the above embodiment, the case where a specific organic compound is used as a doping raw material for realizing the p-type semiconductor crystal has been described. However, other organic compounds may be used within the scope of the present invention.

  Among organic compounds having a C—O—C partial structure, which is a doping raw material for realizing a p-type semiconductor crystal, those having a cyclic bond including this partial structure are preferable. This is because if the O atoms are isolated and taken in, they act as donors, so that the p-type conductivity is canceled, but the O atoms are particularly rarely taken in.

As such compounds, represented by C _n H _2n O (n> 1), [n = 2] Ethylene oxide, [n = 3] Oxetane, Propylene oxide [n = 4] 2,2-Dimethyloxirane, 2 , 3-Dimethyloxirane, 2-Ethyloxirane, 2-Methyloxetane, 3-Methyloxetane, Tetrahydrofuran and compounds having higher carbon number, C _n H _2n-2 O (n> 1), [n = 2] Oxirene [ n = 3] 2H-Oxete, 2-Oxabicyclo [1.1.0] butane, 2-Methyloxirene, 2-Methyleneoxirane [n = 4] 2,3-Ethanooxirane, 2,3-Dihydrofuran, 2,5-Dihydrofuran, 2- Oxabicyclo [1.1.1] pentane, 2-Vinyloxirane, 2-Methyleneoxetane, Dimethyloxirene and a compound having a larger number of carbon atoms, C _n H _2n-4 O (n> 3), [n = 4] 1− Oxaspiro [2.2] penta-4-ene, 2-Ethynyloxirane, 2-Oxatricyclo [1.1.1.0 ^1,3 ] pentane, 2-Vinyloxirene, 5-Oxabicyclo [2.1.0] penta-2-ene, Furan and more carbons n-rich compound, represented by C _n H _2n-6 O (n> 3), [n = 4] Examples include 2-Ethynyloxirene and compounds having a higher carbon number n.

Furthermore, at least one molecule having such a cyclic bond may have a plurality of O atoms in one molecule, and as such a compound, C _n H _2n O ₂ (n> 1) [N = 4] 1,3-Dioxane, 1,4-Dioxane, 2- (Methoxymethyl) oxirane, 2-Ethoxyoxirane, 2-Methyl-1,3-dioxolane, 2-Methyloxirane-2-methanol, 3-Oxetanemethanol, 3-Methyloxirane-2-methanol, 4-Methyl-1,3-dioxolane, α-Methyloxirane-2-methanol, α-Methyloxirane-2-methanol, Oxirane-2-ethanol, Oxetane-2-methanol, Tetrahydrofuran-2-ol, Tetrahydrofuran-3-ol, or a compound having 2 or 3 or more than 4 carbon atoms, represented by C _n H _2n-2 O ₂ (n> 1), [n = 4 ] 1,4-Dioxaspiro [2.3] hexane, 2,3-Dihydro-1,4-dioxin, 2,3-Dihydrofuran-3-ol, 2-Acetyloxirane, 2-Hydroxy-4,5-dihydrofuran, 2-Methyl -2-oxiranecarbaldehyde, 2-Methylene-1,3-dioxolane, 2-Methylene-3-methoxyoxirane, 2-Methoxy-1-oxa-2-cyclob utene, 3,3-Dimethyloxirane-2-one, 3,6-Dioxabicyclo [3.1.0] hexane, 3-Methyloxirane-2-carbaldehyde, 3-Methyloxetan-2-one, 4H-1,3-Dioxin, 4- Methylene-1,3-dioxolane, α-Butyrolactone, β-Butyrolactone, γ-Butyrolactone, Diepoxybutane, Tetrahydrofuran-3-one, compounds having 3 or more carbon atoms, C _n H _2n-4 O ₂ Represented by (n> 2), [n = 4] 1,4-Dioxin, 2 (5H) -Furanone, 2,4-Dimethylene-1,3-dioxetane, 2-Methyleneoxetane-3-one, 3 ( 2H) -Furanone, 3-Hydroxy-2-butenoic acid 1,3-lactone, 3-Vinyloxiran-2-one, 3-Methyleneoxetan-2-one, Diketene, Furan-2 (3H) -one, Furan-2- ol, or a compound having 3 or more carbon atoms, represented by C _n H _2n-6 O ₂ (n> 2), [n = 4] 1,3-Butadiene-1, Examples include 4-dione and compounds with more than 4 carbon atoms, but when there are multiple O atoms in one molecule, O atoms are isolated and incorporated. In order to prevent this, the plurality of molecules include a combination of a C—O—C atomic group and a C * C * O (* is a single bond or a multiple bond) or C—O—C atomic group. It is desirable to be configured. Therefore, it is particularly preferable to select such a molecule from the molecules listed above. From another point of view, a compound having no OH bond is preferable in order to prevent an O atom from being isolated and incorporated.

  The above is an example, and an organic compound having a cyclic bond including a C—O—C partial structure may be used other than the molecular formulas listed here. Furthermore, in an organic compound having a cyclic bond including a C—O—C partial structure, the cyclic bond is preferably composed of three atoms of C, O, and C. This is because two C atoms and one O atom are linked in a ring shape, which is effective in developing a mechanism of incorporating two C atoms and one O atom into a neighboring site. Therefore, it is particularly preferable to select such a molecule from the molecules listed above.

  In addition, among organic compounds having a C—O—C bond, which is a raw material for realizing a p-type semiconductor crystal, the ratio of C atom to O atom is preferably 2 to 1 from another viewpoint. Is. This is because the atomic ratio necessary for the mechanism of the present invention to develop in the crystal is obtained.

As such an organic compound, [m = 1] Dimethyl ether, [m = 2] 1-Methoxy-1-propanol, 1-Methoxy- represented by C _2m H _{4m + 2} O _m (m> 0) 2-propanol, 2-Methoxy-1-propanol, 2-Methoxy-2-propanol, 3-Methoxy-1-propanol, 1,1-Dimethoxyethane, 1,2-Dimethoxyethane, 1-Ethoxyethanol, 2-Ethoxyethanol, Isopropyloxymethanol, [M = 1] Ethylene oxide, [m = 2] 1,1-Dimethoxyethene, 1,2 represented by Ethoxymethoxymethane, Propoxymethanol, and a compound having a higher carbon number, C _2m H _4m O _m (m> 0) -Dimethoxyethene, 1,3-Dioxane, 1,4-Dioxane, 2- (Vinyloxy) ethanol, 2- (Methoxymethyl) oxirane, 2-Ethoxyoxirane, 2-Methyl-1,3-dioxolane, 4-Methyl-1,3 -dioxolane, 2-Methyloxirane-2-methanol, 3-Methyloxirane-2-methanol, 2-Methoxypropanal, 3-Methoxypropanal, 3-Oxetanemethanol, 3-Methoxy-2-propen-1-ol, α-Methyloxirane-2-methanol , Formic acid propyl, Formic acid isopropyl ester, Ethoxyacetaldehyde, Oxirane-2-ethanol, Oxetane-2-methanol, Tetrahydrofuran-2-ol, Tetrahydrofuran-3-ol, Propionic acid methyl, Methoxyacetone, Ethyl acetate, and compounds with higher carbon number, C _2m H _4m-2 O _m (m> 0) [M = 1] Oxirene, [m = 2] 3-Methyloxirane-2-carbaldehyde, 3-Methyloxetane-2-one, β-Butyrolactone, α-Butyrolactone, γ-Butyrolactone, 1,4-Dioxaspiro [ 2.3] hexane, 1- (Oxiranyl) ethanone, 2,3-Dihydro-1,4-dioxin, 2,3-Dihydro-3-hydroxyfuran, 2-Acetyloxirane, 2-Hydroxy-4,5-dihydrofuran, 2-Methyl -2-oxiranecarbaldehyde, 2-Methylene-1,3-dioxolane, 2-Methylene-3-methoxyoxirane, 2-Methoxy-1-oxa-2-cyclobutene, 2-Methoxyacrylaldehyde, 3,3-Dimethyloxirane-2-one, 3 , 6-Dioxabicyclo [3.1.0] hexane, 3-Methoxypropenal, 4H-1,3-Dioxin, 4-Methylene-1,3-dioxolane, Formic acid 1-propen-2-yl ester, Formic acid allyl, Acrylic acid methyl, Ethoxyketene, Diepoxybutane, Dimethoxyethyne, Tetrahydrofuran-3-one, Vinyl acetate and more carbon Compound, represented by _{C 2m H 4m-4 O m} (m> 1), [m = 2] 1,4-Dioxin, 2 (5H) -Furanone, 3 (2H) -Furanone, 2,4- Dimethylene-1,3-dioxetane, 2-Methyleneoxetane-3-one, 3-Hydroxy-2-butenoic acid 1,3-lactone, Formic acid 2-propynyl ester, Diketene, Furan-2 (3H) -one, Furan- [M = 2] 1,2: 3,4-Diepoxy represented by 2-ol, Propiolic acid methyl ester, or a compound having a higher carbon number, C _2m H _4m-6 O _m (m> 1) -1,3-butadiene, 3-Oxa-1-pentene-4-yne-1-one, and a compound having a higher carbon number, C _2m O _m (m> 2), [m = 3 ] 1,4,7-Trioxacyclonona-2,5,8-triyne, 3,6,9-Trioxatetracyclo [6.1.0.0 ^2,4 .0 ^5,7 ] nona-1 (8), 2 (4), 5 (7) -triene and other compounds having carbon number.

  In the case where the ratio of C atom to O atom is 2 to 1, in the case where a plurality of O atoms are contained in one molecule, at least C It is desirable that a plurality of —O—C atomic groups and other C * C * O or C—O—C atomic groups are combined. Therefore, it is particularly preferable to select such a molecule from the molecules listed above.

  In the above embodiment, the method of pouring the organic compound raw material into the furnace for realizing the p-type semiconductor crystal has been described by the method of pouring into the group V line. However, the method is not limited to this. It is also possible to pour into This point is not particularly related to the basis of the present invention. Depending on the form of the MOCVD apparatus, there is a type in which the group V raw material and the group III raw material are poured into the same line without dividing the line. In this case, an organic compound raw material for realizing a p-type semiconductor crystal may be poured into this common line. Alternatively, depending on the form of the MOCVD apparatus, there may be a dedicated line for pouring the impurity material into the furnace. In this case, the present invention is also effective.

  Embodiments of the present invention are summarized below. A group III element organometallic compound, a hydride of nitrogen, and an organic compound having a C—O—C partial structure are used as raw materials, and C atoms and O atoms are simultaneously crystallized by metal organic vapor phase epitaxy. A method of manufacturing a nitride semiconductor crystal which has a p-type conductivity by being incorporated into the semiconductor.

  According to this configuration, both the C atom and the O atom in the organic compound raw material for realizing the p-type semiconductor crystal are taken into the N atom site that should act as an acceptor and a donor, respectively. Therefore, a manufacturing method excellent in controllability of the p-type nitride semiconductor crystal can be provided by using a metal organic chemical vapor deposition method.

  In the above manufacturing method, the supply ratio of the organic metal compound and the hydride of nitrogen may be periodically changed, and the supply amount of the organic compound may be changed in synchronization with the change.

  As a result, both the C atom and the O atom in the organic compound raw material for realizing the p-type semiconductor crystal are surely taken in by the N atom site that should act as an acceptor and a donor. The mechanism that expresses the controllability of the mold works effectively.

  Specifically, by periodically changing the supply ratio, a first period in which Group III elements are preferentially arranged on the growing crystal surface, and nitrogen atoms are preferentially arranged on the growing crystal surface. The second period is alternately provided, and the organic compound is supplied or the supply amount of the organic compound is increased in accordance with the second period.

  Thereby, the organic compound raw material for realizing the p-type semiconductor crystal is substantially supplied in the second period, and C atoms and O atoms contained therein are taken into the N atom site.

  In addition, by periodically changing the supply ratio, a first period in which a group III element is preferentially arranged on the growing crystal surface, and a nitrogen atom is preferentially arranged on the growing crystal surface. Alternating between the first period and the subsequent second period until before the second period, or between the first period and the subsequent second period and the second period and the second period. The organic compound may be supplied or the supply amount of the organic compound may be increased until the subsequent first period.

  This realizes a p-type semiconductor crystal prior to the period in which nitrogen atoms are preferentially arranged on the growth surface with respect to the growth surface sufficiently supplied with group III atoms during the first and second periods. The organic compound raw material to be supplied is supplied, and the C atom and O atom contained therein are taken into the N atom site.

  In the above manufacturing method, the organic compound is preferably supplied to the crystal growth apparatus in a state diluted with hydrogen or an inert gas. This is because, when supplied at a high concentration, they react with each other before reaching the substrate 11 and proper doping cannot be performed.

  In the above production method, the dilution ratio is preferably 0.01 to 10,000 ppm.

In the above production method, the organic compound is composed of a composition formula C _n H _2n O (n> 1), C _n H _2n-2 O (n> 1), C _n H _2n-4 O (n> 3). _{, C n H 2n O 2 (} n> 1), C n H 2n-2 O 2 (n> 1), C n H 2n-4 O 2 (n> 2), C n H 2n-6 O 2 ( It is desirable that any one of n> 3). This is because if the O atoms are isolated and taken in, they act as donors, so that the p-type conductivity is canceled, but the O atoms are particularly rarely taken in.

  In the above production method, the organic compound preferably has a ratio of C atoms to O atoms of 2: 1. This is because the atomic ratio required for the mechanism of the present invention to develop in the crystal is obtained.

Specifically, assuming that the ratio of C atom to O atom is 2: 1, specifically, the composition formulas C _2m H _{4m + 2} O _m (m> 0), C _2m H _4m O _m (m> 0) C _2m H _4m-2 O _m (m> 0), C _2m H _4m-4 O _m (m> 1), C _2m H _4m-6 O _m (m> 1), C _2m O _m (m> 1) It is desirable that either one of 2). In particular, in the case where a plurality of O atoms are contained in one molecule, at least a C—O—C atomic group and other C * C * O in order to prevent the O atoms from being isolated and incorporated. Alternatively, a plurality of C—O—C atomic groups are preferably combined.

  In the above production method, the organic compound preferably has a cyclic partial structure containing C—O—C. As a result, the possibility that O atoms are isolated and incorporated during crystal growth becomes very low, and the effect of molecular doping is more effectively exhibited.

  In the above production method, the cyclic partial structure containing C—O—C is preferably composed of three atoms of C, O, and C. This is because two C atoms and one O atom are linked in a ring shape, which is effective in developing a mechanism of incorporating two C atoms and one O atom into a neighboring site.

  In the above production method, the organic compound is preferably a compound having 2 C atoms and 1 O atom. This is particularly advantageous in that two C atoms and one O atom are taken into a neighboring site as a set.

  The nitride semiconductor crystal of the embodiment of the present invention is a nitride semiconductor crystal manufactured by the above manufacturing method.

  In the above-described nitride semiconductor crystal, it is desirable that C, C, and O atoms are introduced so as to be arranged at three N atom sites adjacent to each other.

  A semiconductor device according to an embodiment of the present invention is a semiconductor device provided with the nitride semiconductor crystal described above.

  The present invention relates to light emitting / receiving devices (LEDs, semiconductor lasers, photodiodes, superluminescent diodes, phototransistors, solar cells, etc.) and electronic devices other than light emitting / receiving devices (diodes, transistors, bipolar electronic devices, unipolar electronic devices). Devices, integrated devices, etc.), spintronic devices, photocatalytic devices, electron tubes and other electronic devices, semiconductor substrates, laser media, magnetic semiconductors, phosphors and the like.

DESCRIPTION OF SYMBOLS 11 Substrate 12 Nitride semiconductor layer 13 P-type nitride semiconductor layer 20 MOCVD apparatus 21 Furnace 22 Stage

Claims (5)

A group III element organometallic compound, a hydride of nitrogen, and an organic compound having a C—O—C partial structure are used as raw materials and 0.05 to 0 in any direction by metal organic vapor phase epitaxy. A nitride semiconductor having p-type conductivity obtained by supplying the raw material to the surface of a (0001) plane nitride semiconductor crystal having an off angle in the range of .8 ° and simultaneously incorporating C atoms and O atoms into the crystal. Crystal production method.   2. The nitride semiconductor crystal according to claim 1, wherein the supply ratio of the organic metal compound and the hydride of nitrogen is periodically changed, and the supply amount of the organic compound is changed in synchronization with the change. Production method. By periodically changing the supply ratio, a first period in which group III elements are preferentially arranged on the growing crystal surface, and a second period in which nitrogen atoms are preferentially arranged on the growing crystal surface; Alternately
The method for producing a nitride semiconductor crystal according to claim 2, wherein the organic compound is supplied or the supply amount of the organic compound is increased in accordance with the second period. By periodically changing the supply ratio, a first period in which group III elements are preferentially arranged on the growing crystal surface, and a second period in which nitrogen atoms are preferentially arranged on the growing crystal surface; Alternately
The organic compound from between the first period and the subsequent second period until before the second period, or between the first period and the subsequent second period until between the second period and the subsequent first period The method for producing a nitride semiconductor crystal according to claim 2, wherein the supply amount of the organic compound is increased. 5. The nitride semiconductor according to claim 1, wherein the organic compound is supplied to the crystal growth apparatus in a diluted state from a cylinder filled with hydrogen or an inert gas. Crystal production method.

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