JP2008021745A - Group iii nitride compound semiconductor laminated structure, and method for growth thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively doping a dopant by controlling reaction of a dopant element in a method for forming a group III nitride semiconductor layer using a nitrogen source in a state of radicals, plasmas, or atoms such as MBE and sputtering process. <P>SOLUTION: The method for growth of the group III nitride compound semiconductor layer using a nitrogen source in the state of radicals, plasmas, or atoms includes a first step for alternately repeating a process to supply only the dopant element, and a process to simultaneously supply a compound including the group III element and a nitrogen raw material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a group III nitride compound semiconductor (hereinafter referred to as a group III nitride compound semiconductor) excellent in both mass productivity and characteristics, which is used in the production of light emitting diodes (LEDs), laser diodes (LDs), and electronic devices. The present invention relates to a stacked structure and a manufacturing method thereof. In particular, the present invention relates to a group III nitride compound semiconductor multilayer structure that can be efficiently doped during film formation using MBE or sputtering, and a film formation method thereof.

  The group III nitride compound semiconductor has a direct transition type band gap of energy corresponding to the visible light to ultraviolet light region, and can emit light with high efficiency, and thus has been commercialized as an LED or LD. In addition, the electronic device has a potential to obtain characteristics that cannot be obtained by a conventional III-V group compound semiconductor.

  For crystal growth of a group III-V compound semiconductor, an MOCVD method is generally used in which ammonia and an organic metal such as organic gallium or an organic indium compound are reacted at a high temperature. In addition, there are reports of crystal growth by MBE or sputtering (see, for example, Patent Document 1, Non-Patent Documents 1 and 2), but they are not used industrially.

  In the case of using MOCVD, when doping is performed, a technique is used in which a compound containing a dopant element is mixed and distributed in a gas phase atmosphere for crystal growth and taken into the crystal. However, in the vapor phase growth method such as sputtering or MBE in which nitrogen is converted into plasma or radical and supplied and reacted, in addition to the method of circulating a compound gas containing the above elements, the dopant element is used. It may be supplied in the state of plasma or radical by supplying with vapor or the same method as the method for supplying the group III element (evaporation for MBE, sputtering for sputtering, etc.).

However, unlike film formation using chemical reaction, in such a film formation method using plasma, radicals or atoms as reactive species, the dopant element is also converted into plasma, radicalized or atomized, so it reacts with nitrogen radicals. there's a possibility that. For example, if Si radicals are supplied into an atmosphere in which nitrogen that has been converted to plasma and Ga sputtered from the target are reacted in order to dope Si, a bond of Si—N is generated and the crystal is A silicon nitride lump is produced.
The occurrence of such a reaction is undesirable because it inhibits the dopant from functioning as a dopant and also reduces the crystallinity of the matrix.

JP 60-39819 A Yukiko Ushibuchi et al., GaN thin film deposition by high frequency magnetron sputtering (I), 2nd 21st Century Union Symposium-Science and Technology and Humans (2003, Tokyo) Ryonan Asami et al., Growth of Si and Mg-doped GaN single crystals by UHV sputtering, 66th JSAP Scientific Lecture Proceedings (Autumn 2005, Tokushima University)

  The object of the present invention is to solve the above-mentioned problems and suppress the reaction of the dopant element even when a film forming method using a radicalized, plasmaized or atomized nitrogen source such as MBE or sputtering is used. It is to provide a method for efficiently doping a dopant.

The present invention provides the following inventions.
(1) In a method for growing a group III nitride compound semiconductor layer using a method of forming a film by supplying nitrogen in a plasma, radical, or atom state and reacting with a group III element, A method of growing a group III nitride compound semiconductor layer comprising a first step comprising alternately repeating a process of supplying only an element and a process of simultaneously supplying a compound containing a group III element and a nitrogen source.

  (2) The group III nitride according to the above item 1, wherein the method of forming a film by supplying nitrogen in any state of plasma, radicals, and atoms and reacting with the group III element is MBE or sputtering. A method for growing a compound semiconductor layer.

  (3) The method for growing a group III nitride compound semiconductor layer according to item 1 or 2, further comprising a second step of performing a heat treatment after the growth in the first step.

  (4) The method for growing a group III nitride compound semiconductor layer according to the above item 3, wherein the heat treatment temperature is in the range of 300 ° C. to 1200 ° C.

  (5) The method for growing a group III nitride compound semiconductor layer according to the above item (3) or (4), wherein the heat treatment is performed in an atmosphere not containing hydrogen gas or a compound gas containing hydrogen atoms.

  (6) The method for growing a group III nitride compound semiconductor layer according to any one of the above items 1 to 5, wherein the dopant element is at least one selected from the group consisting of Si, Ge, and Sn.

  (7) The method for growing a group III nitride compound semiconductor layer according to the above item 6, wherein the dopant element is Si.

  (8) The method for growing a group III nitride compound semiconductor layer according to any one of the above items 1 to 5, wherein the dopant element is at least one selected from the group consisting of Mg and Zn.

  (9) The method for growing a group III nitride compound semiconductor layer according to the above item 8, wherein the dopant element is Mg.

  (10) A laminated structure of a group III nitride compound semiconductor, wherein a layer made of a dopant element and a layer made of a group III nitride compound semiconductor are alternately formed.

  (11) The laminated structure according to the above item 10, wherein the thickness of the layer made of the dopant element is in the range of 0.5 nm to 10 nm.

  (12) The laminated structure according to the above item 10 or 11, wherein the thickness of the layer made of a group III nitride compound semiconductor is in the range of 1 nm to 500 nm.

  (13) The above 10 to 12, wherein the thickness ratio of the layer made of a group III nitride compound semiconductor to the layer made of a dopant element (layer made of a group III nitride compound semiconductor / layer made of a dopant element) is 10 to 1000 The laminated structure according to any one of Items.

  (14) The laminated structure according to any one of the above items 10 to 13, wherein the number of repetitions of the layer made of the dopant element and the layer made of the group III nitride compound semiconductor is between 1 and 200 times.

  (15) The layered structure according to any one of (10) to (14), wherein the layer made of the dopant has an island shape and does not completely cover the layer made of the group III nitride compound semiconductor.

  (16) The laminated structure according to claim 15, wherein the diameter (equivalent circle diameter) of each island-shaped lump constituting the dopant layer is in the range of 0.5 nm to 100 nm.

  (17) The laminated structure as described in 15 or 16 above, wherein the distance between the island-shaped lumps constituting the dopant layer is in the range of 2 nm to 100 nm.

  (18) The laminated structure according to any one of the above items 15 to 17, wherein the ratio of the total area of each island-shaped lump constituting the dopant layer is in the range of 0.001 to 0.9 with respect to the entire region. body.

  (19) The laminated structure according to any one of the above items 10 to 18, wherein the group III nitride compound semiconductor is GaN or AlGaN.

  (20) A region doped with a dopant element in a high concentration and a region doped with a low concentration are obtained by heat-treating the laminated structure according to any one of items 10 to 19 above. Group III nitride compound semiconductor layer.

  (21) A group III nitride compound semiconductor layer obtained by heat-treating the laminated structure according to any one of items 10 to 19, wherein the dopant element is uniformly doped over the entire region.

  (22) The group III nitride compound semiconductor layer according to the above item 20 or 21, wherein the dopant element is at least one selected from the group consisting of Si, Ge and Sn.

  (23) The group III nitride compound semiconductor layer according to item 20 or 21, wherein the dopant element is at least one selected from the group consisting of Mg and Zn.

  (24) An n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer made of a group III nitride compound semiconductor are stacked on a substrate, and a negative electrode is provided on the n-type semiconductor layer, and a positive electrode is provided on the p-type semiconductor layer. 24. The light emitting device according to claim 22, wherein the n-type semiconductor layer is the group III nitride compound semiconductor layer described in the above item 22.

  (25) An n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer made of a group III nitride compound semiconductor are stacked on a substrate, and a negative electrode is provided on the n-type semiconductor layer, and a positive electrode is provided on the p-type semiconductor layer. 24. The light emitting device according to 24, wherein the p-type semiconductor layer is a group III nitride compound semiconductor layer according to item 23.

(26) A lamp comprising the light emitting device as described in 24 or 25 above.
(27) An electronic device in which the lamp according to item 26 is incorporated.
(28) A mechanical device in which the electronic device as described in (27) above is incorporated.

  In the method for growing a group III nitride compound semiconductor layer of the present invention, a dopant can be efficiently doped when film formation is performed using a physical film formation method which is a crystal growth method excellent in mass productivity and characteristics. it can. For this reason, the light-emitting elements manufactured using the group III nitride compound semiconductor multilayer structure obtained by this method can be operated at a low driving voltage, and are effective in saving power and energy.

The essence of the present invention is to alternately stack layers of dopant atoms and undoped group III nitride semiconductor layers and perform doping.
In the case of a chemical vapor deposition method such as MOCVD, doping is possible by mixing gases, and it is not necessary to adopt such a method. However, methods such as MOCVD inevitably have problems with productivity and reproducibility, and it is desirable to establish a film formation method using a physical crystal film formation method such as sputtering or MBE.

  In such a physical crystal film forming method, nitrogen is supplied in the form of plasma, radical or atomization. In order to prevent reaction between dopant atoms and nitrogen, it is desirable not to supply nitrogen into the chamber in the process of supplying dopant atoms.

  Therefore, as a result of repeated thoughts and experiments, we have developed a deposition method in which the process of supplying only the dopant and the process of depositing the group III nitride compound semiconductor using nitrogen are alternately repeated. The laminated structure formed by this method has a structure in which layers made only of dopants and layers made of undoped group III nitride compound semiconductors are alternately laminated. In the process of alternately laminating, some of the dopant atoms constituting the dopant layer may diffuse into the group III nitride compound semiconductor layer, but at this stage, there is always a layer consisting only of the dopant atoms.

  The dopant forming the layer may be a p-type dopant or an n-type dopant. Known dopants for Group III nitride compound semiconductors include Mg and Zn for p-type dopants, and Si, Ge, and Sn for n-type dopants. Among them, Si as the n-type dopant and Mg as the p-type dopant are most preferable because both the doping efficiency and the activation rate are high and the crystallinity is hardly lowered.

  As the group III nitride compound semiconductor crystal forming the layer, GaN and AlGaN usually used as a contact layer are suitable.

  If the dopant layer completely covers the group III nitride compound semiconductor layer, the crystal lattice constants are different, so that the epitaxial relationship is not established, and the crystallinity is lowered. Therefore, it is desirable to form the dopant layer so as to be scattered on the surface in an island shape without forming a complete layer. By taking such a form, the group III nitride compound semiconductor crystal can be epitaxially grown from the exposed surface as a starting point, and the surface can be completely filled by lateral growth.

  The interval between the island-shaped lumps of the island-shaped dopant layer is preferably in the range of 2 nm to 100 nm in width. If the interval is smaller than this, it becomes difficult for the group III compound semiconductor crystal to be epitaxially grown with the gap as a starting point, and if it is larger than this, the dopant does not spread sufficiently, leading to an increase in driving voltage in the case of an element. More desirably, the width is in the range of 10 nm to 50 nm.

  The ratio of the total area of each island-shaped lump of the island-shaped dopant layer to the entire region is desirably 0.001 or more and 0.9 or less. If it is larger than this, it becomes difficult for the group III compound semiconductor crystal to epitaxially grow with the gap between the island-like lumps as the starting point, and if it is smaller than this, the dopant does not spread sufficiently, and the drive voltage rises in the case of an element. Invite. More desirably, it is 0.005 to 0.5.

  The diameter (equivalent circle diameter) of each island-shaped lump of the island-shaped dopant layer is preferably a value between 0.5 nm and 100 nm. If it is smaller than this, the dopant does not spread sufficiently, leading to an increase in driving voltage in the case of an element, and if it is larger than this, the crystallinity of the group III compound semiconductor crystal is lowered. More desirably, the thickness is 1 nm to 10 nm.

  The diameter and interval of each island-shaped lump in the island-shaped dopant layer as described above can be measured by observation with a transmission electron microscope using a sample with an exposed cross section. Further, the ratio of the total area of each island-shaped lump to the entire region can be calculated from the average value of the above-mentioned diameter and interval measured at 10 points at random.

In order to form the dopant layer as an island-shaped lump as described above, it is preferable to devise conditions for film formation. Since the dopant layer is not lattice-matched with the group III nitride compound semiconductor layer, an island-like crystal lump can be formed under conditions that cause migration actively.
For example, the substrate temperature is 600 ° C. or more, the chamber pressure during film formation is 0.3 Pa or less, the film formation rate is 0.5 nm / sec or less, and the like.

  The thickness of the dopant layer is preferably 0.5 nm to 10 nm. If it is thinner than this, there is a possibility that the dopant does not spread sufficiently, and if it is thicker than this, it becomes difficult to embed even if the group III nitride compound semiconductor crystal grows in the lateral direction. More desirably, it is about 1 nm to 5 nm.

  The film thickness of the group III nitride compound semiconductor layer is desirably 1 nm to 500 nm. If it is thicker than this, there is a possibility that the dopant does not spread sufficiently. If it is thinner than this, it becomes difficult to bury the group III nitride compound semiconductor crystal even by lateral growth. More desirably, it is about 10 nm to 100 nm.

  The ratio of the thicknesses of both layers (group III nitride compound semiconductor layer / dopant layer) is preferably 10 to 1000. If it is less than this, the dopant is excessively doped, and the crystallinity of the group III nitride compound semi-responding crystal is lowered. If it is more than this, the dopant will not reach sufficiently, leading to an increase in resistivity of the laminated structure and an increase in driving voltage.

  The number of repetitions of the group III nitride compound semiconductor layer and the dopant layer formed in the first step is preferably between 1 and 200 times. Even if it is repeated 200 times or more, there is no great difference in the function of the element, but only a decrease in crystallinity is caused.

  Sputtering, PLD, PED, CVD, and the like are known as methods for supplying nitrogen material as plasma or radicals. Of these, the sputtering method is the most convenient and suitable for mass production, and is therefore a suitable method. In DC sputtering, the target surface is charged up and there is a high possibility that the deposition rate is not stable. Therefore, it is desirable to use pulse DC or RF sputtering.

  As the raw material for generating plasmatized or radicalized nitrogen used in this technology, generally known compounds can be used without any problem, but especially ammonia and nitrogen are easy to handle and relatively inexpensive. Available and desirable. Ammonia has good decomposition efficiency and can be deposited at a high growth rate. However, ammonia is highly reactive and toxic, requires abatement equipment and a gas detector, and uses materials for the components used in the reactor. It needs to be devised, such as having to be highly stable. Conversely, when nitrogen is used as a raw material, the apparatus is simple, but a high reaction rate cannot be obtained. The method in which nitrogen is decomposed by an electric field or heat and then introduced into the apparatus is inferior to ammonia, but can provide a film forming rate that can be used. Considering the balance with the apparatus cost, the most suitable nitrogen source It is.

  When the film is formed by sputtering, important parameters are the substrate temperature, the pressure in the furnace, and the nitrogen partial pressure. The substrate temperature is generally room temperature to 1200 ° C. Crystal decomposition occurs at 1200 ° C. or higher. Preferably it is 200 to 900 degreeC.

  The pressure in the furnace is preferably 0.3 Pa or more. At pressures below this, the amount of nitrogen present is small and the sputtered metal adheres without becoming nitrides. The upper limit of the pressure is not particularly defined, but it is needless to say that a low pressure that can generate plasma is required. The ratio of the nitrogen flow rate to the nitrogen flow rate is preferably 20% or more and 100% or less. At a flow rate ratio of 20% or less, sputtered metal adheres as it is. Particularly preferably, it is 50% or more and 90% or less. At a flow rate ratio of 90% or more, the amount of argon is small and the sputtering rate tends to decrease.

  The film formation rate is desirably 0.01 nm / second to 10 nm / second. At higher speeds, the film becomes amorphous rather than crystalline. If the film formation speed is lower than this, the film does not become a layer but grows in an island shape and cannot cover the surface of the substrate.

  On the other hand, since the dopant layer is a single component layer, it is not reactive sputtering. For this reason, both RF sputtering and DC sputtering can be used as the sputtering apparatus. In the case of using DC sputtering, it is preferable to provide conductivity so that the target is not charged. For example, in the case of Si, when a high purity Si target is used, it is insulative and charge-up can be considered. Therefore, it is preferable to use a material doped with B or P. However, since it takes a lot of time to move wafers between chambers when alternately laminating, it is desirable to laminate in the same chamber as the group III nitride compound semiconductor, and eventually RF sputtering is used. Would be desirable.

  For the same reason, it is desirable that the furnace pressure and the substrate temperature be performed under the same conditions as those for the group III nitride compound semiconductor. The film formation rate is slower than that of the group III nitride compound semiconductor, and it is easy to control the thin film thickness appropriately, so 0.001 nm / second to 1 nm / second is desirable.

As a film formation technique for supplying atomic material to a substrate, there is a molecular beam epitaxy (MBE) method.
In the case of using MBE, a metal is melted in a cell installed in a high vacuum chamber, and the substrate is irradiated with the vapor by vapor pressure. At that time, a group III nitride compound semiconductor is grown by reacting on the substrate by simultaneously supplying nitrogen raw materials. As a nitrogen raw material, a method of supplying gaseous NH ₃ and a method of decomposing N ₂ with plasma or the like and irradiating the cell with a gas pressure are generally used. In this method, plasma irradiation is preferable because nitrogen is not preferably present in the chamber when forming the dopant layer.

The pressure in the chamber is desirably 1 × 10 ⁻⁴ Pa to 1 × 10 ⁻⁶ Pa, which is a general degree of vacuum of MBE. At higher pressures, the reactive elements do not form a beam, and even lower pressures only take a long time.

  The substrate temperature is desirably room temperature or higher and 1200 ° C. or lower as in the case of using sputtering. As with the sputtering method, the film formation rate is preferably about 0.01 nm / second to 10 nm / second for the group III nitride compound semiconductor layer and about 0.001 nm / second to 1 nm / second for the dopant layer.

  After forming a structure in which the dopant layers and the group III nitride compound semiconductor layers are alternately stacked, it is desirable to perform heat treatment as the second step. By this heat treatment, the dopant can be diffused into the group III nitride semiconductor crystal, and a more uniform doping state can be obtained.

  The heat treatment temperature is preferably 300 ° C. or higher. Although there is no particular upper limit, it goes without saying that the temperature must not exceed the temperature at which the matrix crystal decomposes. Many Group III nitride compound semiconductor crystals decompose at a temperature of about 1200 ° C.

  The heat treatment time is not particularly limited, but is generally preferably 30 seconds to 1 hour. The effect is not sufficient when it is 30 seconds or less, and the effect is not changed after 1 hour or more.

In addition, regarding the atmosphere during the heat treatment, in particular, when it is desired to form a p-type dopant layer by forming a p-type dopant layer, it is desirable not to use a hydrogen gas and a compound gas containing hydrogen atoms in the molecule. In particular, it is desirable not to use H ₂ gas or NH ₃ gas which is known to decompose at high temperature to generate H ₂ gas.

  Depending on the heat treatment time and temperature, the laminated structure after the heat treatment may include a dopant mass as a trace of the dopant layer. The dopant mass diffuses and disappears, but the dopant concentration is lower than that of the high-concentration layer. In some cases, the layer may remain as a repetition of the concentration layer, and in some cases, the dopant diffuses to form a completely uniform doping layer.

  Therefore, the laminated structure after the heat treatment functions as a contact layer in the element. Of course, when a p-type dopant layer is used, it can be used as a p-contact layer, and when an n-type dopant layer is used, it can be used as an n-contact layer.

  In the contact layer, an electrode for passing a current is formed. As the electrode material, generally known materials can be used without any problem. For example, the n-electrode material is Al, Ti, Cr, etc., and the p-electrode material is Ni, Au, Pt, or the like. In addition, conductive oxides such as ITO, ZnO, AZO, and IZO can be used.

  As a substrate that can be used for manufacturing the laminated structure of the present invention, any material can be used as long as it can generally form a group III nitride compound semiconductor crystal. For example, sapphire, SiC, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide Lanthanum strontium oxide aluminum tantalum, strontium titanium oxide, titanium oxide, hafnium, tungsten and molybdenum.

  Examples of devices using the laminated structure of the present invention include light-emitting elements, photoelectric conversion elements such as laser elements and light-receiving elements, and electronic devices such as HBT and HEMT. Many of these semiconductor elements have various structures, and the element structure using the group III nitride compound semiconductor multilayer structure of the present invention is not limited at all including these well-known element structures.

  In particular, in the case of a light emitting element, it is possible to package an element manufactured by the present technology and use it as a lamp. Further, a technique for changing the emission color by combining with a phosphor is known, and this can be used without any problem. For example, by appropriately selecting a phosphor, light having a longer wavelength than that of the light emitting element can be obtained, and a white package can be obtained by mixing the light emitting wavelength of the light emitting element itself with the wavelength converted by the phosphor. You can also.

  In addition, a lamp packaged with a light-emitting element manufactured with this technology has a low driving voltage. Therefore, an electronic device such as a mobile phone, a display, or a panel incorporating the lamp manufactured by this technology, an automobile incorporating the electronic device, Mechanical devices such as computers and game machines can be driven with low power and can achieve high characteristics. In particular, the battery-powered devices such as mobile phones, game machines, toys, and automobile parts exhibit power saving effects.

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited only to these examples.
(Example 1)
In this example, a method for producing a group III nitride compound semiconductor light emitting device using the group III nitride compound semiconductor multilayer structure of the present invention will be described.

A cross-sectional view of the laminated structure manufactured in this example is shown in FIG. In the epitaxial wafer, an AlN layer (2) is formed as a buffer layer on a sapphire substrate (1) having a c-plane, and then an undoped GaN layer (3) having a thickness of 6 μm and an undoped layer having a thickness of 100 nm are sequentially formed from the substrate side. N-type GaN layer (4), in which an GaN layer (4a) of 0.1 nm and an Si layer (4b) made of island-shaped crystal lumps having a thickness of 0.1 nm are alternately stacked 20 times, 1 × 10 ¹⁸ cm ⁻³ electrons A 200-inch-thick In _0.1 Ga _0.9 N clad layer (5) having a concentration, a GaN barrier layer (6a) having a layer thickness of 160 、 starting from the GaN barrier layer and ending with the GaN barrier layer, and a layer thickness of 30 Å A multi-quantum well structure light-emitting layer (6) consisting of five layers of non-doped In _0.2 Ga _0.8 N well layer (6b), and an Mg _0.1- doped Al _0.1 Ga _0.9 N diffusion prevention layer (7) And a thickness of 0.2 μm It has a structure in which an Mg-doped Al _0.02 Ga _0.98 N layer (8) is laminated.

  Further, FIG. 2 shows a plan view of the electrode structure of the semiconductor light emitting device manufactured in this example. In the figure, 10 is an n-side electrode, 11 is an exposed surface of the Si-doped GaN layer (4) for forming the n-electrode, 12 is a p-electrode bonding pad, and 13 is a translucent p-electrode.

  The AlN buffer layer (2) on the sapphire to the n-type GaN layer (4) were formed using RF magnetron sputtering. The sputtering machine used had a target-cathode distance of 50 mm. The substrate temperature during film formation was 750 ° C., and the pressure during film formation was 0.6 Pa.

A 4-inch diameter sapphire substrate was used.
In the process of forming the AlN buffer layer (2), a mixed gas of argon and nitrogen was introduced into the chamber, and nitrogen converted into plasma by applying an electric field was used as a nitrogen source. On the other hand, an Al target was struck by plasma-generated argon to struck metal atoms and reacted with nitrogen to form a film on the substrate.

  In the process of laminating the undoped GaN layer (3), similarly to the AlN film formation, a mixed gas of argon and nitrogen is introduced into the chamber, and plasma nitrogen is used as a nitrogen source. Ga was sputtered from the target and reacted with nitrogen to form a film on the substrate.

  In the process of alternately laminating the undoped GaN layer (4a) and the Si layer (4b), the undoped GaN is deposited in the same procedure as the undoped GaN layer (3), and the Si layer is deposited in the chamber. The only gas introduced was argon, and the atoms knocked out of the Si target were laminated on the substrate as they were.

  The substrate manufactured through the above steps was taken out of the sputtering machine and heat-treated using an annealing furnace. The heat treatment temperature was 1100 ° C. and held for 10 minutes. The gas phase atmosphere during the heat treatment was composed of only nitrogen.

  The n-type GaN layer (4) was observed with a transmission electron microscope from the cross-sectional direction before and after annealing. In the laminated structure before annealing, a structure in which 2 nm Si layers and 100 nm undoped GaN layers were alternately laminated 20 times was observed. The Si layer was interrupted in some places and did not form a complete layer, but was an island shape. The circle-equivalent diameter of each island-shaped lump was about 1 nm, and the interval between each island-shaped lump was about 50 nm. Therefore, the ratio of the total area of the dopant layer was about 0.02 with respect to the entire region. However, in the n-type GaN layer (4) after annealing, no clear layer structure was observed, and it was considered that Si atoms constituting the dopant layer diffused and the GaN layer was uniformly doped.

Subsequently, the substrate was introduced into an MOCVD furnace, and the layers after the cladding layer (5) were formed by MOCVD. General temperatures, pressures, gases used, and the like were used.
By the procedure as described above, an epitaxial wafer having an epitaxial layer structure for a semiconductor light emitting device was produced.

Next, a light-emitting diode, which is a kind of semiconductor light-emitting element, was manufactured using an epitaxial wafer in which an epitaxial layer structure was stacked on the sapphire substrate. About the produced wafer, a transparent p-electrode 13 made of ITO is laminated on the surface of the Mg-doped Al _0.02 Ga _0.98 N layer (8) by a well-known photolithography technique, and titanium, aluminum, and gold are laminated in that order from the surface side. A p-electrode bonding pad 12 having the structure as described above was formed as a p-side electrode. Further, dry etching is performed on the wafer to expose the portion 11 where the n-side electrode of the Si-doped GaN layer (4) is formed, and the n-side electrode 10 composed of four layers of Ni, Al, Ti and Au is exposed to the exposed portion. Produced. By these operations, an electrode having a planar shape as shown in FIG. 2 was produced on the wafer.

  For the wafer on which the p-side and n-side electrodes were formed in this way, the back surface of the sapphire substrate was ground and polished to form a mirror-like surface. Thereafter, the wafer was cut into 350 μm square chips, placed on the lead frame so that the electrodes were on top, and connected to the lead frame with gold wires to obtain a light emitting device. When a forward current was passed between the p-side and n-side electrodes of the light-emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.0V. When light emission was observed through the p-side translucent electrode, the light emission wavelength was 470 nm, and the light emission output was 15 mW at a current of 20 mA. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

(Example 2)
In this example, the same structure as that of Example 1 was fabricated using MBE from the AlN buffer layer (2) on sapphire to the n-type GaN layer (4). The MBE apparatus used was one having a target-cathode distance of 300 mm. The substrate temperature during film formation was set to 750 ° C. A 4-inch diameter sapphire substrate was used.

  In the process of forming the AlN buffer layer (2), nitrogen converted into plasma using a plasma cracker is introduced into the chamber, while Al evaporated from the Knudsen cell is introduced and reacted with nitrogen. A film was formed on the substrate.

  In the process of laminating the undoped GaN layer (3), nitrogen cracked using a plasma cracker is introduced into the chamber and Ga evaporated from the Knudsen cell is introduced, as in the AlN film formation. To form a film on the substrate.

  In the process of alternately laminating the undoped GaN layer (4a) and the Si layer (4b), the undoped GaN is deposited in the same procedure as the undoped GaN layer (3), and the Si layer is deposited in the chamber. Nitrogen to be introduced was stopped, and Si vapor introduced from the Knudsen cell was laminated on the substrate as it was.

  The wafer produced as described above was used as a light emitting diode chip in the same manner as in Example 1. When a forward current was passed between the p-side and n-side electrodes, the forward voltage at a current of 20 mA was 3.0V. Further, when luminescence was observed through the p-side translucent electrode, the emission wavelength was 530 nm, and the emission output was 9 mW at a current of 20 mA. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

(Example 3)
The cross-sectional view of the laminated structure produced in this example is basically the same as that shown in FIG. 1 except for the AlGaN layer doped with Mg.

On the sapphire substrate having c-plane, in order from the substrate side, an AlN buffer layer, an undoped GaN layer having a thickness of 6 μm, an n-type GaN layer doped with Si of 1 × 10 ¹⁹ cm ⁻³ , 1 × 10 ¹⁸ cm ⁻³ An In _0.1 Ga _0.9 N cladding layer having a thickness of 200 mm, a six-layer GaN barrier layer having a thickness of 160 mm starting from the GaN barrier layer and ending with the GaN barrier layer, and a thickness of 30 mm. A light emitting layer having a multi-quantum well structure composed of a non-doped In _0.2 Ga _0.8 N well layer is produced by MOCVD, taken out of the MOCVD furnace, introduced into an RF sputtering machine, and 100 nm thick Al _0.1 Ga _{A structure in which 0.9} N layers and 2 nm thick Mg layers were alternately stacked twice was formed. Thereafter, this wafer was taken out from the RF sputtering machine and heat-treated at 900 ° C. for 1 minute using an annealing furnace.

  The wafer produced as described above was used as a light emitting diode chip in the same manner as in Example 1. When a forward current was passed between the p-side and n-side electrodes, the forward voltage at a current of 20 mA was 3.1V. When light emission was observed through the p-side translucent electrode, the light emission wavelength was 470 nm, and the light emission output was 15 mW at a current of 20 mA. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

  An element manufactured using the present technology can be driven at a low voltage. Further, by using this technology, it is possible to manufacture a large number of elements having stable characteristics at a low cost.

It is a schematic diagram which shows the cross section of the group III nitride compound semiconductor laminated structure for semiconductor light-emitting devices produced in Example 1 of this invention. It is a top view which shows the electrode structure of the semiconductor light-emitting device produced in Example 1 of this invention.

Explanation of symbols

1 substrate 2 AlN buffer layer 3 undoped GaN layer 4 n-type GaN layer 4a undoped GaN layer 4b Si layer 5 In _0.1 Ga _0.9 N cladding layer 6 light emitting layer 6a GaN barrier layer 6b In _0.2 Ga _0.8 N well layer 7 Mg-doped Al _0.1 Ga _0.9 N diffusion preventing layer 8 Mg-doped Al _0.02 Ga _0.98 N layer 10 n-side electrode 11 portion forming n-side electrode of n-type GaN layer 12 p-electrode bonding pad 13 translucent p-electrode

Claims (28)

  In the growth method of a group III nitride compound semiconductor layer using a method of forming a film by supplying nitrogen in any state of plasma, radical, or atom and reacting with the group III element, only the dopant element is obtained. A method for growing a group III nitride compound semiconductor layer comprising a first step comprising alternately repeating a process of supplying and a process of simultaneously supplying a compound containing a group III element and a nitrogen source.   2. The group III nitride compound semiconductor layer according to claim 1, wherein the method of forming the film by supplying nitrogen in a plasma, radical, or atom state and reacting with the group III element is MBE or sputtering. 3. Growth method.   The method for growing a group III nitride compound semiconductor layer according to claim 1, further comprising a second step of performing a heat treatment after the growth in the first step.   The method for growing a group III nitride compound semiconductor layer according to claim 3, wherein the heat treatment temperature is in the range of 300 ° C to 1200 ° C.   The method for growing a group III nitride compound semiconductor layer according to claim 3 or 4, wherein the heat treatment is performed in an atmosphere containing no hydrogen gas or a compound gas containing hydrogen atoms.   The method for growing a group III nitride compound semiconductor layer according to any one of claims 1 to 5, wherein the dopant element is at least one selected from the group consisting of Si, Ge, and Sn.   The method for growing a group III nitride compound semiconductor layer according to claim 6, wherein the dopant element is Si.   The method for growing a group III nitride compound semiconductor layer according to any one of claims 1 to 5, wherein the dopant element is at least one selected from the group consisting of Mg and Zn.   The method for growing a group III nitride compound semiconductor layer according to claim 8, wherein the dopant element is Mg.   A laminated structure of a group III nitride compound semiconductor, wherein a layer made of a dopant element and a layer made of a group III nitride compound semiconductor are alternately formed.   The laminated structure according to claim 10, wherein the thickness of the layer made of the dopant element is in the range of 0.5 nm to 10 nm.   The layered structure according to claim 10 or 11, wherein the thickness of the layer made of the group III nitride compound semiconductor is in the range of 1 nm to 500 nm.   The thickness ratio between the layer made of a group III nitride compound semiconductor and the layer made of a dopant element (layer made of a group III nitride compound semiconductor / layer made of a dopant element) is 10 to 1000. The laminated structure according to claim 1.   The multilayer structure according to any one of claims 10 to 13, wherein the number of repetitions of the layer made of the dopant element and the layer made of the group III nitride compound semiconductor is between 1 and 200 times.   The layered structure according to any one of claims 10 to 14, wherein the layer made of the dopant has an island shape and does not completely cover the layer made of the group III nitride compound semiconductor.   The laminated structure according to claim 15, wherein a diameter (equivalent circle diameter) of each island-shaped lump constituting the dopant layer is in a range of 0.5 nm or more and 100 nm or less.   The laminated structure according to claim 15 or 16, wherein an interval between the island-like lumps constituting the dopant layer is in the range of 2 nm to 100 nm.   The laminated structure according to any one of claims 15 to 17, wherein a ratio of a total area of each island-shaped lump constituting the dopant layer is in a range of 0.001 to 0.9 with respect to the entire region.   The laminated structure according to any one of claims 10 to 18, wherein the group III nitride compound semiconductor is GaN or AlGaN.   A group III nitride obtained by heat-treating the multilayer structure according to any one of claims 10 to 19, wherein a region doped with a high concentration of a dopant element and a region doped with a low concentration are mixed. Compound semiconductor layer.   A group III nitride compound semiconductor layer obtained by heat-treating the multilayer structure according to any one of claims 10 to 19, wherein the dopant element is uniformly doped over the entire region.   The group III nitride compound semiconductor layer according to claim 20 or 21, wherein the dopant element is at least one selected from the group consisting of Si, Ge, and Sn.   The group III nitride compound semiconductor layer according to claim 20 or 21, wherein the dopant element is at least one selected from the group consisting of Mg and Zn.   A light emitting device comprising an n-type semiconductor layer, a light emitting layer, and a p type semiconductor layer made of a group III nitride compound semiconductor on a substrate, each having a negative electrode on the n type semiconductor layer and a positive electrode on the p type semiconductor layer A light emitting device wherein the n-type semiconductor layer is a group III nitride compound semiconductor layer according to claim 22.   A light emitting device comprising an n-type semiconductor layer, a light emitting layer, and a p type semiconductor layer made of a group III nitride compound semiconductor on a substrate, each having a negative electrode on the n type semiconductor layer and a positive electrode on the p type semiconductor layer The light-emitting element according to claim 23, wherein the p-type semiconductor layer is a group III nitride compound semiconductor layer according to claim 23.   A lamp comprising the light emitting device according to claim 24 or 25.   An electronic device in which the lamp according to claim 26 is incorporated.   A mechanical device in which the electronic device according to claim 27 is incorporated.

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