JP4586160B2 - Method for producing p-type semiconductor crystal thin film of gallium nitride by duel pulse laser deposition technique and thin film produced by the same method - Google Patents

Description

The present invention relates to a thin film manufactured by the manufacturing method and the law of p-type semiconductor crystal thin film of gallium nitride, and more particularly, p-type semiconductor of the Ga N epitaxial thin film and the like uniaxially oriented and polycrystalline crystalline thin film (whole referred to as crystal thin film), between the thin film of p-type and n-type Ga n, the p-n semiconductor junction element between the thin film and the other n-type semiconductor thin film and the substrate of p-type Ga n The present invention relates to a manufacturing method, the thin film obtained thereby, and a pn semiconductor junction element formed by stacking the thin film with a substrate and another thin film. The present invention is particularly, p-type semiconducting crystal thin film of Ga N underlying wide bandgap semiconductor electronics and optoelectronics, said p-type thin film and the n-type was Ga N or GaN and other n-type semiconductor The present invention is useful for providing a new technique relating to a laminated thin film and a pulse laser deposition film forming method for obtaining them.

  GaN is an important semiconductor in the field of optoelectronics such as light emitting diodes (LEDs) and lasers in the blue and ultraviolet range. In the future, in the fields of next-generation energy, information communication, and electronics, high-power, high-temperature, high-frequency, and radiation-resistant electronic devices, high-performance short-wavelength lasers, and inexpensive white light-emitting diodes are expected. However, in order to realize this, it is necessary to develop a simple GaN p-type semiconductor technology, in addition to a technique for producing high-quality single crystal thin films and laminated thin films. Conventionally, in the manufacture and research and development of these electronic and optical devices, GaN film formation and element formation have been performed mainly using a CVD film formation method (see Non-Patent Documents 1 and 2). Therefore, the most important and difficult technology of making GaN into a p-type semiconductor is performed using a doping method by MO-CVD or MO-VPE using an organic Mg compound or an organic Zn compound. However, in this method, Mg or Zn enters (adds to) the GaN film in a state of being bonded to hydrogen, and is not hole-doped (activated) as it is. In particular, Mg is more reactive, so it is more difficult to handle and semiconductorize than Zn.

  For these reasons, electron beam irradiation or high-temperature heat treatment is performed under vacuum after film formation, breaking the bond between metal and hydrogen, expelling hydrogen, and the added metal does not cause defects in the lattice, so that it is exactly Ga. It is activated to replace it and serve as a hole doping material. However, these require high technology, are difficult to control, and costly. Therefore, there is a demand for the development of a p-type semiconductor technology that is simpler than the conventional method so that simultaneous doping and activation can be achieved at the time of GaN film formation, and post-processing is unnecessary. In particular, in order to develop next-generation semiconductor devices such as next-generation electronic devices, inexpensive short-wavelength LEDs, lasers, and white light-emitting diodes, the same thin film as that of a simple GaN p-type semiconductor or pn device technology And elements are required.

Conventionally, sapphire (Al ₂ O ₃ ) is mainly used as the substrate (see Non-Patent Document 3). Sapphire has poor crystal lattice length consistency with GaN (about 33% mismatch in the same orientation, 18% mismatch between oxygen sublattice and GaN), but no other suitable substrate In addition, it is used because it has the same symmetry (hexagonal system) as a GaN crystal and does not react with ammonia or nitrogen radicals used for nitriding. In order to alleviate the large lattice mismatch, a single crystal thin film such as aluminum nitride (AlN) that has the same crystal structure (hexagonal system) as GaN and is easy to grow is first formed on sapphire at low temperature. In addition, a method of forming a GaN heteroepitaxial thin film at a high temperature on it as a buffer layer is used (see Non-Patent Document 4). In addition, although the deposition rate is slow, there is a report on direct deposition of GaN single crystal thin film on sapphire by gas source MBE method. Further, (111) of ferrite (Fe ₂ O ₄ ), (0001) buffer layer of AlN on sapphire or a mixture of InN and GaN (see Non-patent Document 6), α-silicon carbide (α-SiC) ( (0001) or β-SiC (111), (111) buffer layer of alumina (γ-Al ₂ O ₃ ) on Si (see Non-Patent Documents 7 and 9), sapphire (0001) or cubic crystal In addition to ZnO (111) buffer layer on (111) plane, ZrB2 substrate and YSZ substrate, there are reports of GaN film formation on many substrates and crystal planes such as fused silica (amorphous) substrates (non-patent) (Ref. 5, 8, 10).

GaN has the same hexagonal structure as other Group III metal nitrides AlN, InN, and BN, so it is possible to produce a single crystal thin film mixed with any composition. The energy band gap width depends on the composition ratio. It is also known that a pn junction light emitting device with a controlled emission wavelength can be produced. It has also been found that GaN crystalline thin films can be fabricated on various substrates as described above.
For these reasons, if we developed a simple p-type semiconductor technology that does not require post-processing different from conventional methods for adding Mg to GaN, and demonstrated that p-type GaN thin films can be fabricated on several substrates, It will be possible to produce p-type GaN and pn junction elements on each of the above-mentioned substrates that are known to be capable of producing GaN thin films. Further, if p-type conversion by doping is achieved with respect to highly reactive Mg, p-type conversion using low-reactivity Zn is also possible, and in addition to GaN, other group III metal nitrides AlN, InN, BN, and A p-type thin film of a mixture of GaN and another group III metal nitride and a pn junction element can be manufactured, and a new technology can be provided in the electronics and optonic fields.

S. Nakamura, T. Mukai and M. Senoh, Appl. Phys. Lett., 64 (1994) 1687 M. Inamori, H. Sakai, T. Tanaka, H. Amano and I. Akasaki, Jpn. J. Phys. 34, (1995) 1190 R. D. Vispute, V. Talyansky, R. P. Sharma, S. Choopun, M. Downes, K. A. Jones, A. A. Liadis, M. AsifKhan and J. W. Yang, Appl. Phys. Lett. 71 (1997) 102 R. D. Vispute, H. Wu and J. Narayan, Appl. Phys. Lett. 67, (1995) 1549 R. -F.Xiao, X.W.Sun, H. B. Liao, n. Cue and H. S. Kwok, J. Appl. Phys. 80, (1996) 4224 Mitsuo Ota, Hiroshi Fujioka, Shoji Ojima, Abstracts of the 8th Association of Applied Physics 31a-L-7, (2002), P.421 Norihiko Ochi, Yoshiyuki Matsuura, Koji Otsuka, Norihiro Kuwahara, Masatomo Kakutani, Toshiro Fukuya, The 50th Japan Federation of Applied Physics 29a-T-10, (2003), P.411 Motoaki Iwatani, Kazuki Iida, Atsushi Kawashima, Shinji Fukui, Satoshi Miyazaki, Toshi Takanami, Hitoshi Tomita, Satoshi Nitta, Satoshi Ueyama, Hiroshi Amano, Isamu Akasaki, 50th Japan Federation of Applied Physics 29a-T-4, (2003), P.409 Masafumi Harada, Takayuki Nagano, Noriyoshi Shibata, Proceedings of the 50th Federation of Applied Physics 27a-V-2 (2003), P.382 Naoshi Honke, Shingo Ito, Mio Ota, Hiroshi Fujioka, Masaharu Ojima, Abstracts of the 50th Association of Applied Physics 29a-T-7, (2003), P.410

In such a situation, the present inventors, in view of the above-mentioned prior art, use the PLAD method at a high temperature, unlike the conventional method by MO-CVD using the organometallic compound of Mg or Zn. the goal of the doping metal Mg for added holes simultaneously with the deposition of the epitaxial thin film of Ga N, to develop the p-type thin film and method capable of achieving a p-type semiconducting without aftertreatment, creative As a result of a lot of ingenuity and research, the GaN target for the film and the target containing the additive Mg are alternately or simultaneously ablated, or a dual pulse laser deposition (duel PLAD) method is used in which the mixed target of GaN and MgN is ablated. in the ammonia to nitrogen radicals atmosphere, various single crystal and non was temperature-controlled at a high temperature of 7 00 ° C. or higher It found that can achieve the object by forming a GaN thin film containing a metal for added holes on the substrate quality, and have completed the present invention.
An object of the present invention is to solve the above-mentioned conventional problems, and to perform Ga N p-type having a VI rectification characteristic peculiar to a pn junction without post-treatment such as electron beam irradiation or advanced high-temperature heat treatment. The object is to provide a method for obtaining a semiconducting epitaxial thin film and a crystalline thin film, and the same thin film and pn thin film element obtained by this method.

The present invention for solving the above-described problems comprises the following technical means.
(A) A target material is irradiated onto a target material by irradiating the target material with a pulse laser, and instantaneously and pulse-decomposing and separating (ablating) fine particles such as ions, atoms and clusters, and controlling the temperature to a high temperature of at least 700 ° C. Using a pulsed laser ablation deposition (PLAD) means for producing a thin film of GaN, a GaN target is used as a film material and an Mg target is used as an additive material for hole doping in an ammonia or nitrogen radical atmosphere. GaN that is made into a p-type semiconductor on the substrate by a duel pulse laser deposition (duel PLAD) technique in which these are alternately or simultaneously ablated, or a target in which both the film material and the additive material are mixed is ablated. Epitaxial (single crystal) thin film or crystalline thin film , And the specific voltage to p-n junction - current (V-I) characteristics method for manufacturing a thin film, which comprises preparing a (V-I rectifying characteristics) thin film having a.
(B) A method for producing a thin film as described in (a) above, wherein a thin film of a target material is produced on a substrate whose temperature is controlled to 700 ° C. or higher.
(C) The method for producing a thin film according to (a), wherein a thin film of a target material is produced on a substrate whose temperature is controlled to a high temperature of 700 ° C. or more and less than 750 ° C.
(D) As a substrate, (1) a single crystal of sapphire, Si, SiC, or GaN itself, (2) an epitaxial thin film or crystalline thin film of n-type GaN produced on a single crystal of Si, sapphire, or SiC, or (3) The method for producing a thin film according to any one of (a) to (c), wherein an epitaxial thin film of ZnO produced on a single crystal of Si or sapphire is used.
(E) As the crystal plane of the substrate, (1) an AlN buffer layer formed on the (0001) plane of sapphire, α-SiC or ZnO, (2) the sapphire (0001) plane, other group III metal nitrides Α-SiC (0001) plane, or β-, produced on the (0001) plane, (3) sapphire (0001) plane of the buffer layer, or a buffer layer of a mixture of GaN and other group III metal nitrides (111) plane of SiC, (4) ZnO (0001) plane, (5) Si (111) plane, (6) (111) ferrite, (7) Any one of (a) to (d) above, wherein the (111) surface of an alumina buffer layer on Si or (8) the surface of an amorphous (glass) substrate is used. A method for producing the thin film according to 1.
(F) A p-type GaN thin film made into a p-type semiconductor produced on a Si substrate by the method for producing a thin film according to any one of (a) to (e) , and produced on the p-type GaN thin film. An n-type GaN thin film-p-type GaN thin film-n-type Si (111) inter-substrate junction structure comprising n-type GaN thin film formed into an n-type semiconductor, and between p-type GaN thin film and substrate, and p-type GaN A pn junction element characterized by having a VI rectification characteristic peculiar to a pn junction in measurement between an n-type semiconductor and an n-type semiconductor.

Next, the present invention will be described in more detail.
In the present invention, the Duel PLAD technique, SiC, to prepare a crystal thin film with p-n junction element structure of a p-type Ga N to Si and sapphire single crystal substrate. First, p-type semiconducting GaN (abbreviated as p-GaN) epitaxial thin film on SiC single crystal substrate and analysis result of thin film by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) , And the demonstration that a p-GaN / n-SiC junction is formed between the thin film and the substrate from measurement of voltage-current (V-I) characteristics. Next, regarding the p-type GaN thin film produced on the n-type and p-type Si single crystal substrates, the n-Si / p-GaN junction and the p-Si / p-GaN junction between the thin film and the substrate are obtained due to the VI characteristics thereof. A description will be given of the fact that a junction has been produced, that is, the formation of a p-type GaN thin film and the production of a pn junction structure. Next, a p-GaN / n-GaN two-layer thin film junction fabricated on Si, SiC, and sapphire will be described. Further, a ZnO / GaN epitaxial thin film formed on a sapphire single crystal substrate and a p-GaN polycrystalline thin film formed on an n-Si substrate will be described.

for the production of p- type Ga N, as an example, the target material and a hole doping material, respectively, using a sintered body of Mg metal GaN, to produce an epitaxial thin film of p-type semiconductor of the GaN by Duel PLAD technique. This will be described with reference to the drawings. In addition, since GaN is a hexagonal crystal as a substrate, it is the same hexagonal crystal and has a (0001) plane of each single crystal of 6H—SiC and sapphire having a 6-fold rotation axis (C ₆ symmetry), and a cubic crystal. This will be illustrated using a Si (111) plane having C6 symmetry of a Si single crystal.

  FIG. 1 shows an example of the duel PLAD technique. Two targets (targets 1 and 2) for film and additive can be set in the vacuum vessel, and two separate pulse laser beams (lasers 1 and 2) from the outside are set at the laser pulse frequency f and irradiation energy E. In addition, by irradiating both targets by changing the fluence F by a condensing means such as a lens (1, 2) or the like, the additive is also ablated at the time of GaN film formation, and its concentration is controlled, A device capable of doping and activating the additive during film formation by controlling the temperature of the substrate was constructed and used. Both targets are set in two target holders (1, 2) with a target rotation mechanism (1, 2) driven by a motor, and are rotated so as to be uniformly ablated by a laser. The substrate is set in a substrate holder with a heater, and its temperature is controlled. Ammonia was used as an atmospheric gas to serve as a nitrogen source to compensate for the lack of some nitrogen due to decomposition of GaN accompanying pulse laser irradiation and to nitride an additive such as Mg to form MgN or the like. .

In the production of crystalline thin film of p-type semiconductor of Ga N with duel PLAD method in the present invention, since the substrate may be any substrate which can be made the crystalline thin film, Si, silicon carbide (SiC), sapphire, ferrite (Fe ₂ O ₃ ), ferrites doped with Mn and Zn, etc., or alumina (Al ₂ O ₃ ) produced on Si, AlN or SiC produced on sapphire, further on sapphire or amorphous substrate Although ZnO crystal film or the like prepared is illustrated in, it may be selectively used depending on the quality of the p-n elements of the crystalline thin film and the nitride of costs and Ga n and p-type was the nitride, those substrate It does not depend on the type.

Although the material substance film according to the elements of Ga N is GaN, optionally, of GaN itself outside, Ga and Al, In, etc. cognate metal or its nitride or GaN on their cognate B nitride Ga-based nitrided mixture was added, and examples of the target, Duel PLAD approach targets prepared if necessary, so may be any, not depending on their type. That is, the target film material only needs to retain the same hexagonal crystal structure as GaN regardless of which compound or element is contained. Therefore, in addition to GaN, nitrides such as AlN, InN, BN, etc. In addition, a mixture of GaN and these homologous nitrides is exemplified. Furthermore, not limited to these, any metal nitride that becomes a hexagonal material or a mixture thereof can be used. Furthermore, since it nitrided by that the chamber has a ammonia or nitrogen radical atmosphere, Ga, Al, an In, and B metals, to Ga and mixtures of these metals, as a target a mixture of Ga N and these metals to free It can also be used. As the hole doping material used in the p-type semiconductor of Ga N, a divalent metal, and so may be a element with Ga ³⁺ and close ionic radius having an ionic radius of 0.62Å, 0. it can be used M g with ionic radius of 65 Å. Furthermore, the crystal thin film of n-type semiconductor of Ga N required to produce the p-n junction, trace IV element Si, Ti, Ge, Zr, Sn, Pb or V group element V, As, Sb, and Bi, It can produce by adding.

Next, embodiments of the Duel PLAD method according to the present invention and a (0001) -oriented epitaxial thin film, a crystalline thin film, and a pn junction structure of p-type semiconducting GaN will be described in detail with reference to the drawings.
Figure 1 shows a schematic diagram of a method for making the crystal thin film of Ga N on the substrate.
A GaN target and an Mg metal target are set in the two target holders (1, 2) in the vacuum vessel shown in FIG. 1, and an α-SiC or sapphire (0001) substrate or Si (111) substrate or C ₆ symmetry. If a substrate having properties, an amorphous substrate, or the like is set in a substrate holder with a heater, a (0001) -oriented epitaxial thin film or a crystalline thin film of p-type semiconducting GaN can be produced on the same substrate.

As an embodiment of the present invention, 1) an example in which an epitaxial thin film of GaN having p-type and n-type semiconductor characteristics is formed on an n-type 6H—SiC substrate using the PLAD method, and 2) n-type and p-type An example of producing an epitaxial thin film of p-type GaN on a Si single crystal substrate, 3) p-GaN / n-GaN bilayer film produced on a Si substrate, and 4) n-GaN produced on SiC. 5) n-SiC / p-GaN bilayer film, 6) ZnO / GaN bilayer film, and 7) p-GaN produced on an n-Si substrate. An example of the polycrystalline thin film is shown. In the Duel PLAD technique, as described above, also, as shown in Figure 1, advance to set the two targets (1,2) of GaN and metal Mg on the two target holder in the vacuum vessel, must In a simple gas atmosphere, two target laser beams (1, 2) are focused and irradiated on each target through an optical window for laser beam irradiation from the outside, and the target material is pulsed at the same time or at a constant cycle ratio. A thin film of the material is produced by ablating and colliding it with a substrate set on a substrate holder with a heater at a position opposed to the substrate and controlled at a constant temperature by an electric heater or the like.

Here, fourth harmonic (wavelength 266 nm) lasers from two Nd: YAG pulse laser devices were used as two pulse laser beams for ablating the film material and the additive material. The laser beam is only able to be ablated target material additive material and Ga N, regardless laser type and wavelength. However, since the quality of the film depends on the laser wavelength and the like, the laser may be selected depending on the target film and quality. As shown in FIG. 1, by irradiating both targets with this separate pulsed laser light from the outside by changing the fluence F by condensing means such as lenses (1, 2) in addition to laser f and E, GaN The additive can be doped and activated by simultaneously ablating the additive during film formation, controlling the concentration, and optimizing the PLAD conditions such as changing the temperature of the substrate.

  In the duel PLAD method, it is only necessary to ablate the film material and the additive material simultaneously, almost simultaneously or alternately. Therefore, in addition to the method using two beams from two laser devices, the film material and additive material can be emitted from one pulse laser device. The laser beam is split into two beams with different energies using a half mirror, and further, the shutter, filter and lens synchronized with the pulse are used to irradiate with changing f, E and F, that is, by half mirror beam separation. Examples include irradiation methods and beam sweeping methods using pulse-synchronized mirrors that use a rotating mirror or prism synchronized with pulses to change the beam direction so that the laser strikes two targets alternately at a fixed pulse number ratio. However, since there are only two beams, the method is not limited.

Furthermore, in a target holder with a rotating mechanism that can set a target such as a disk, the film material and the additive material have a certain ratio, and a fan-shaped or arc-shaped narrow band shape so that it can be set in the holder. Cut and match them to make a single disk-shaped target, set a target that has a disk-shaped film material target with an additive material cut into a narrow band, or set the film material and By setting one target in which additive materials are mixed at a certain ratio, and irradiating one periodic pulse laser beam to perform ablation (dual PLAD in a broad sense), the concentration of the additive with respect to the film material is controlled. The method of forming a film is exemplified, but both the film material and the additive material only need to be ablated at a constant rate. It does not matter.
By this duel PLAD method, two targets of GaN and Mg are ablated in an ammonia atmosphere, and GaN containing Mg is formed on the 6H—SiC (0001), sapphire (0001), Si (111) substrate surface or the like. By conducting an optimization experiment for forming a film, a GaN heteroepitaxial thin film and a pn device structure made into a p-type semiconductor can be produced.

In the present invention, it is sufficient to produce the crystal thin film of Ga N, the other preceding substrate, (0001) other alpha-SiC to GaN own 4H-SiC or the like is hexagonal substrate also, If a (111) substrate having β ₆ -SiC C ₆ symmetry, or an amorphous substrate, which is a cubic system, is set in a substrate holder, a hetero-epitaxial layer of Ga N formed into a p-type semiconductor on the substrate holder Thin films, crystalline thin films, and pn device structures can be fabricated.

As described above in detail, the present invention relates to a method for producing a crystalline thin film of a gallium nitride p-type semiconductor and a thin film produced by the same method. According to the present invention, (1) a Ga N target and hole doping a target containing additive Mg of use of alternating or simultaneously ablation, by a method of using the Duel PLAD method such that a thin film of the target material to temperature-controlled substrate to a high temperature of 7 00 ° C. or higher, ammonia or nitrogen under radical atmosphere, a variety of single-crystal or amorphous substrate, p-type semiconductor of the Ga n thin film comprising a specific V-I rectifying characteristics in p-n junction, and n-type of the same Ga n It is possible to produce a thin film or a pn junction with another n-type semiconductor thin film or substrate. (2) In the present invention, Mg, which is an additive for hole doping, is formed into a GaN film. Sometimes it can be added and activated in-situ, so that it is possible to break through the problems that require processes such as electron beam irradiation after film formation and precise high-temperature heat treatment for conventional activation, (3) Since it is possible to form films on many different substrates and other epitaxial thin films, it becomes possible to make high-temperature and high-power related to GaN, electronic devices such as high-frequency devices and short-wavelength LEDs, and optoelectronics. , Etc. are produced.

  EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following Examples.

  In this example, preparation of a p-type GaN heteroepitaxial thin film on an n-type 6H—SiC substrate is described. The crystal characteristics of the film measured by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) will be described, and then the fabricated n-6HSiC substrate / p-GaN thin film junction is voltage-current (V-I). A demonstration of showing a rectifying characteristic peculiar to a pn bond from measurement of characteristics, that is, that a p-type GaN heteroepitaxial thin film is produced by the PLAD method will be described. In addition, for comparison and confirmation, an n-type GaN heteroepitaxial thin film is fabricated on an n-type 6H-SiC (0001) single crystal substrate, and the junction does not have pn characteristics.

In the preparation of a p-type GaN thin film on SiC by the duel PLAD method, a GaN sintered body is used as a film target, a metal Mg is used as an additive target, and an n-type 6H-SiC (0001) single crystal is used as a substrate. And ammonia (NH ₃ ) was used for nitriding. The PLAD film forming conditions are as follows. Heater temperature Th: 800 ° C., NH ₃ pressure: 3 × 10 ⁻³ Torr, laser frequency ν: 4 Hz, irradiating laser energy for both GaN and Mg targets E: 10 mJ / pulse, laser irradiation energy on both GaN and Mg targets The density F is 1.3 J / cm ² / pulse, the ratio of the number of laser irradiation pulses to GaN and Mg per unit time: R = n (Mg) / m (GaN) is 1/20. This condition is a value optimized to some extent in the case of ν = 4 Hz and R = 1/20, but the optimum value of each factor of the PLAD condition is related to other factors, and T _h and ν are changed. Sometimes the optimum values of E and F vary to some extent.

Even when nitrogen RF plasma was used as the atmosphere, the crystal characteristics of the film were slightly lower than in the NH ₃ atmosphere, but p-type GaN could be formed. However, a p-type GaN thin film could not be formed in a simple nitrogen gas atmosphere. NH ₃ or nitrogen plasma is necessary because Mg and laser-decomposed Ga must be recombined by reaction with NH ₃ or nitrogen radicals to become MgN and GaN. Since nitrogen radicals need only be generated, they do not depend on how they are generated, such as RF plasma, DC plasma or nitrogen radical gun.

  The present invention is not limited in any way by the examples and conditions, but many examples are given to describe the fabrication, crystallinity, VI characteristics, etc. of each thin film. Regarding the heater temperature, the film was formed by changing the temperature in the range of 600 to 800 ° C. Among them, the crystal quality was the best at 800 ° C. From this result, it was found that the crystallinity could be improved by further raising the temperature to 900-1100 ° C. However, here, the film formation was fixed at 800 ° C. due to the limitation of the heater used. However, from the GaN film formation experiment at a high temperature range of 800 ° C or higher using another heater, the evaporation of the GaN thin film during deposition is intense at high temperatures. To suppress this, the NH3 pressure is increased and irradiation is performed. It has been found that it is necessary to increase the deposition rate by increasing the laser energy E and the like. However, here, p-type conversion is the original purpose, and the film quality may be set according to the quality of the intended thin film or element, and the PLAD conditions are not limited by the conditions of the embodiment.

FIG. 2 shows an XRD pattern measured for a p-GaN thin film formed on an n-6HSiC (0001) substrate as an example (Example 1). In addition to the (0006) and (00012) diffraction lines of the substrate, only the (0002) diffraction line of GaN is observed, indicating that a (0001) thin film of GaN, that is, a c-axis oriented thin film is formed. . Next, FIG. 3 shows an RHEED image of this thin film. (B) and (d) are images in the [1-100] and [10-10] directions of the 6H—SiC substrate, and (a) and (b) are RHEED images in both directions of the GaN thin film fabricated thereon. It is. The RHEED pattern shows a reciprocal lattice image of the crystal. Each image was measured by rotating the film sample around the vertical axis of the film, and was observed at a period of 60 °. Therefore, the film showed C ₆ symmetry, that is, hexagonal GaN ( It became clear that an epitaxial thin film having a (0001) orientation was produced.

  The interval between vertical lines (streak lines) or vertical lines including dots (dot streak lines) is proportional to the reciprocal of the lattice spacing in each direction. As observed, the spacing between the streak lines of SiC and GaN is almost the same because the crystal lattice length (a = b) in the c-axis vertical plane (film surface) of both is 3.07 mm and This is because it is very close to 3.186cm. Thus, a GaN single crystal thin film, that is, an epitaxial thin film having not only the same c-axis orientation as 6H-SiC but also the same orientation in the film plane (ab plane) is completely produced. Proven in

  FIG. 4 shows VI characteristics measured between the GaN (0001) film / n-6HSiC (0001) substrate. On the reverse bias side, there is a little leakage current in the vicinity of (-) 20 V, but almost no current flows, and the characteristic that current rapidly rises in the forward (+) bias direction, that is, a characteristic characteristic of a pn junction is observed. This shows that a p-semiconductor GaN thin film was produced. Here, a terminal was taken using In or Ag metal, and VI measurement was performed. The dead voltage is present before the current rises in the forward bias direction because the ohmic contact between the n-SiC and the metal terminal is not sufficiently obtained. On the other hand, when only the GaN target is ablated without adding Mg, an n-type GaN thin film is generated.

  Thus, FIG. 5 shows the VI characteristics measured for the n-GaN / n-SiC junction after forming an n-type GaN thin film on an n-6HSiC (0001) substrate. Since no ohmic contact is made between the metal terminal and n-SiC or the like, a characteristic curve is shown in the Schottky junction that shows non-linearity up to the low voltage region near 3-4V of both forward and reverse biases. In addition, no rectification characteristic such that the current shows almost 0 until a reverse bias of −20 V like the p-GaN / n-SiC is shown. The above results clearly show that an epitaxial thin film of GaN doped with Mg and made into a p-type semiconductor can be fabricated by the duel PLAD method in which Mg is added in-situ.

  Next, as another example, the production of a (0001) -oriented epitaxial thin film of p-type GaN produced on n-type and p-type Si substrates and its VI characteristic will be described. FIG. 6 shows an XRD pattern of a p-type GaN thin film formed on an n-type Si (111) single crystal substrate by adding Mg by the duel PLAD technique. The PLAD film forming conditions are substantially the same as the film formation on the SiC substrate except that the substrate temperature is 750 ° C. In addition to Si (hhh) h = 1-3, a (0002) diffraction line of GaN is observed at 2θ = 34.6 °. In addition, although a GaN (101) diffraction line or the like is observed at 36.80 °, the intensity is weak, which indicates that a (0001) oriented film of GaN is almost formed. FIG. 7 shows RHEED images of the Si substrate of the thin film and the GaN thin film. A dot pattern is observed instead of a perfect concentric pattern of polycrystals, and the orientation deteriorates, but it can be seen that a (0001) oriented epitaxial thin film of GaN is formed. V-I characteristics measured between the GaN thin film / n-Si substrate and an n-GaN / n-Si junction formed by depositing only GaN on an n-Si (111) substrate without adding Mg The V-I characteristics are shown in FIGS. Obviously, pn junctions and nn junctions are formed as in the previous examples of p-GaN / n-SiC and n-GaN / n-SiC junctions. Therefore, Mg is used by using the duel PLAD technique. It shows that a p-type GaN thin film can be produced on a Si substrate by adding.

  Next, as another embodiment, an n-type GaN thin film is further produced on the p-type GaN produced on the n-type Si substrate, and the n-Si (111) substrate / p-GaN / n- The VI characteristics of the GaN thin film (double laminated thin film) were measured. The result is shown in FIG. Both the Si substrate / p-GaN and p-GaN / n-GaN exhibit rectifying characteristics peculiar to a pn junction. In addition, although the Si substrate and n-GaN of both ends showed Schottky behavior, the characteristic characteristic to the nn junction was shown. These results illustrate that GaN pn junction thin films can be produced by the duel PLAD technique.

  Thus, it was confirmed by XRD or RHEED measurement that the production and lamination of the GaN epitaxial thin film were achieved, and it was revealed that a pn junction was produced.

  Furthermore, an example of the duel PLAD technique is shown. The PLAD film forming conditions are substantially the same as those in the first embodiment. As Example 4, an RHEED pattern of an n-GaN / p-GaN bilayer film fabricated on an n-6HSiC (0001) substrate is shown in FIG.

Further, as Example 5, an RHEED pattern of an n-GaN / p-GaN bilayer film produced on a sapphire (0001) surface is shown in FIG.

  Furthermore, as Example 6, an RHEED pattern measured for an n-ZnO / p-GaN film formed on a sapphire (0001) surface is shown in FIG. FIG. 14 shows a VI curve measured between the n-GaN / p-GaN bilayer films on the n-6HSiC (0001) substrate produced in Example 4. Judging from RHEED, since the crystallinity is not good, the VI characteristic is not good, but a GaN thin film bond that clearly shows the pn characteristic is produced.

Furthermore, according to the Duel PLAD method, a p-type thin film of polycrystalline GaN can also be produced. Example 2 above is an example of manufacturing the p-GaN epitaxial thin film at a substrate temperature _T h = 750 ° C. in n-Si (111) substrate, the film formation is the on the same substrate at 700 ° C. lower the _{T h} A polycrystalline thin film of p-type GaN is produced. FIG. 15 shows an RHEED image of the thin film. Obviously, a concentric pattern characteristic of a crystalline thin film having no orientation is observed, and it can be seen that a polycrystalline thin film is clearly produced. FIG. 16 shows the VI characteristics between the thin film and the n-Si substrate. Although the characteristics are slightly lower than those of FIG. 8 of the example of the epitaxial thin film of p-type GaN on the Si substrate, the p- Rectification characteristics peculiar to the n junction are observed, indicating that the polycrystalline thin film also has p-type semiconductor characteristics. On the other hand, for comparison, a thin film was formed on an n-Si (111) substrate by simply adding GaN without adding Mg under the same PLAD conditions. Although a similar polycrystalline thin film is formed, the VI characteristic shows the same nn junction characteristic as that of the n-GaN epitaxial thin film / n-Si junction in Example 2 above.

The present invention according to the thin film fabricated by the manufacturing method and the law of p-type semiconductor crystal thin film of gallium nitride, the present invention, a target containing additive M g for target and hole doping Ga N the method of using the Duel PLAD technique or the like for alternating or simultaneous ablation, under ammonia or nitrogen radicals atmosphere, p-type semiconductor of the Ga n thin film on various single crystal and amorphous on the substrate, and an n-type the Ga n film, or production of p-n junction with the other n-type semiconductor thin film and the substrate is possible. Further, in the present invention, since the M g is the additive for the hole doping can be added to and activated in-situ during GaN film formation, electron beam irradiation and precision after the film formation for conventional activated Problems that require a process such as high-temperature heat treatment can also be broken through. In addition, since it can be deposited on many different substrates and other epitaxial thin films, it is possible to make electronic elements in electronics and optonics such as high temperature, high output, high frequency element and short wavelength LED related to GaN. It becomes.

It is the schematic which shows the method of the film-forming by the duel PLAD method for producing the single crystal thin film and crystalline thin film which made the p type semiconductor of Ga group III metal nitride on a single crystal substrate or a glass substrate. . The XRD pattern measured about the p-GaN thin film produced on the n-6HSiC (0001) board | substrate by the duel PLAD technique is shown. The RHEED image measured about the p-GaN epitaxial thin film produced on the n-6HSiC (0001) board | substrate is shown. The VI characteristic measured between the produced p-GaN (0001) epitaxial thin film and the n-6HSiC (0001) substrate is shown. The VI characteristic measured between the produced n-GaN (0001) epitaxial thin film and the n-6HSiC (0001) substrate is shown. The XRD pattern of the p-type GaN thin film produced on the n-type Si (111) single crystal substrate by the duel PLAD technique is shown. The RHEED image of the p-type GaN epitaxial thin film produced on the n-type Si (111) substrate is shown. The VI characteristic measured between the produced p-GaN epitaxial thin film and the n-Si substrate is shown. The VI characteristic measured between the produced p-GaN epitaxial thin film and the p-Si substrate is shown. The VI characteristic measured between each junction of produced n-Si (111) board | substrate / p-GaN thin film / n-GaN thin film (double epitaxial laminated thin film) is shown. The RHEED pattern of the n-GaN / p-GaN bilayer epitaxial thin film produced on the n-6HSiC (0001) substrate is shown. The RHEED pattern of the n-GaN / p-GaN bilayer epitaxial thin film produced on the sapphire (0001) surface is shown. The RHEED pattern measured about the n-ZnO / p-GaN bilayer epitaxial thin film produced on the sapphire (0001) surface is shown. The VI curve measured between the n-GaN / p-GaN bilayer epitaxial thin films produced on the n-6HSiC (0001) board | substrate is shown. The RHEED pattern of the p-GaN polycrystalline thin film produced on the n-Si (111) substrate is shown. The VI characteristic measured between the produced p-GaN polycrystalline thin film and an n-Si (111) board | substrate is shown.

Claims (6)

  The target material is irradiated with a pulse laser, and the target material thin film is formed on a substrate whose temperature is controlled to a high temperature of at least 700 ° C. by decomposing and peeling (ablation) fine particles such as ions, atoms and clusters instantaneously and in pulses. Using a pulsed laser ablation deposition (PLAD) means to be produced, using a GaN target as a film material and an Mg target as an additive material for hole doping in an ammonia or nitrogen radical atmosphere, A p-type semiconducting GaN epitaxial layer is formed on a substrate by a dual pulse laser deposition (duel PLAD) technique in which a target obtained by ablating alternately or simultaneously or a mixture of both the material of the film material and the additive material is ablated. Single crystal) thin film or crystalline thin film , Specific voltage to p-n junction - current (V-I) characteristics method for manufacturing a thin film, which comprises preparing a (V-I rectifying characteristics) thin film having a.   2. The method for producing a thin film according to claim 1, wherein a thin film of a target material is produced on a substrate whose temperature is controlled to 700 [deg.] C. or higher.   2. The method for producing a thin film according to claim 1, wherein a thin film of a target material is produced on a substrate whose temperature is controlled to a high temperature of 700 ° C. or more and less than 750 ° C.   (1) single crystal of sapphire, Si, SiC, or GaN itself, (2) epitaxial thin film or crystalline thin film of n-type GaN formed on a single crystal of Si, sapphire, or SiC, or (3) The method for producing a thin film according to any one of claims 1 to 3, wherein an epitaxial thin film of ZnO produced on a single crystal of Si or sapphire is used.   As the crystal plane of the substrate, (1) the (0001) plane of sapphire, α-SiC or ZnO, (2) the AlN buffer layer produced on the sapphire (0001) plane, a buffer layer of another group III metal nitride, Alternatively, a (0001) plane of a buffer layer of a mixture of GaN and another group III metal nitride, (3) a (0001) plane of α-SiC, or β-SiC ( (111) plane, (4) ZnO (0001) plane, (5) Si (111) plane, (6) Ferrite (111), (7) 5. The production of a thin film according to claim 1, wherein the (111) surface of an alumina buffer layer on Si or (8) the surface of an amorphous (glass) substrate is used. Method. The method for manufacturing a thin film according to any one of claims 1 to 5 fabricated on a Si substrate, a p-type semiconductive and the p-type GaN thin film, n-type semiconductor of which is fabricated on of the p-type GaN thin film The n-type GaN thin film has an n-type GaN thin film-p-type GaN thin film-n-type Si (111) substrate junction structure, and between the p-type GaN thin film and the substrate, and between the p-type GaN and the n-type semiconductor. A pn junction element having a VI rectification characteristic peculiar to a pn junction in measurement.