JP4160000B2 - Light emitting diode and manufacturing method thereof - Google Patents

Description

The present invention relates to a light emitting diode (hereinafter referred to as an LED), and more particularly, to a light emitting diode having a nanorod structure and a method for manufacturing the same.

In the early stages of development, LEDs were widely used as simple display elements for instrument panels. Recently, however, LEDs are used for large-scale electric boards, etc. It is attracting attention as. Such applications have become possible with the recent development of blue and green high brightness LEDs. On the other hand, a group III-nitrogen compound semiconductor such as GaN has been extensively studied as a material for such an LED. This is because the group III-V nitride semiconductor has a wide bandgap, so that light in almost all wavelength ranges from visible light to ultraviolet light can be obtained depending on the composition of the nitride. However, since GaN currently has no substrate lattice-matched with GaN, a sapphire substrate is mainly used, but there are still many mismatches and the difference in thermal expansion coefficient is also large.

Therefore, an n-GaN layer doped with an n-type impurity, an InGaN active layer, and a p-GaN layer doped with a p-type impurity are sequentially stacked on a normal GaN LED, that is, a sapphire substrate. The laminated film-like LED thus formed has a limit in device performance (luminance) because of the above-mentioned limitations on the physical properties of GaN or the growth method, because there are many threading dislocations due to lattice mismatch. In addition, the ordinary laminated film-like GaN LED has advantages such as relatively simple design and manufacture and low temperature dependence, but besides the above-mentioned thread-like dislocations, low luminous efficiency, wide spectral width, It has disadvantages such as large output deviation.

On the other hand, in order to overcome the shortcomings of the laminated film-like LED, a nanoscale LED that forms an LED by forming a pn junction with a one-dimensional rod or a linear nanorod (nanorod, nanowire). Alternatively, micro-scale LEDs such as micro-rings and micro-discs have been studied. However, unfortunately, even with such nanoscale or microscale LEDs, as many thread-like dislocations are generated as in the case of laminated film-like LEDs, no satisfactory high-brightness LEDs have yet appeared. It is a fact. Moreover, since the LED of the nanorod structure is a simple pn junction diode, it is difficult to obtain high luminance. Microring and microdisk LEDs are currently manufactured by photolithography or electron beam evaporation, but the GaN lattice structure is damaged during the etching process, so that the brightness and luminous efficiency are satisfactory. The product has not appeared.

  In view of the above problems, an object of the present invention is to provide a GaN LED structure having high luminance and high luminous efficiency. Another object of the present invention is to provide a method for manufacturing a GaN LED having high luminance and high luminous efficiency with good reproducibility.

In order to achieve the above technical problem, a GaN LED according to the present invention has a pn junction Ga.
Inserting an InGaN quantum well into the pn junction surface of the N nanorod to form an n-type G
A GaN nanorod in which an aN nanorod, an InGaN quantum well, and a p-type GaN nanorod are successively arranged in this order is used. Further, by arranging a large number of such GaN nanorods in an array, an LED having higher luminance and higher luminous efficiency than that of a conventional laminated film-like GaN LED is provided.

That is, the LED according to the present invention is
A substrate,
A first conductivity type GaN nanorod formed in a direction perpendicular to the substrate, an InGaN quantum well formed on the first conductivity type GaN nanorod, and an InGaN quantum well on the InGaN quantum well. A nanorod array comprising a plurality of nanorods each having a GaN nanorod of the second conductivity type formed;
An electrode pad commonly connected to the first conductivity type GaN nanorods of the nanorod array to apply a voltage;
A transparent electrode that is commonly connected to the second conductivity type GaN nanorods of the nanorod array and applies a voltage. Here, the first conductivity type and the second conductivity type mean n-type and p-type, respectively, or p-type and n-type, respectively.

A transparent insulating material having excellent gap fill characteristics, such as SOG (Spin-On-Glass), SiO ₂ or epoxy resin, is embedded between the plurality of nanorods.

The quantum well may be manufactured from a multi quantum well formed by alternately laminating a plurality of InGaN layers and a plurality of GaN barrier layers.

On the other hand, a method of manufacturing a GaN LED according to the present invention includes:
Forming a number of first conductivity type GaN nanorods in an array in the vertical direction of the substrate;
Forming an InGaN quantum well on each of the plurality of first conductivity type GaN nanorods;
Forming a second conductivity type GaN nanorod on each of the InGaN quantum wells;
Forming an electrode pad for applying a voltage to the first conductivity type GaN nanorod;
Forming a transparent electrode connected to the second conductivity type GaN nanorods in common and applying a voltage. Here, the GaN nanorods of the first conductivity type, the InGaN quantum wells, and the GaN nanorods of the second conductivity type are MO-HVPE (metalorganic-hydride).
It is desirable to form in-situ by vapor phase epitaxy method.

  According to the GaN LED and the manufacturing method thereof according to the present invention, a high-luminance, high-luminance LED can be obtained in a high yield without using a catalyst or a template.

  According to the present invention, since a GaN nanorod having InGaN quantum wells is formed by a single epitaxial growth, a high-luminance and high-quality diode can be obtained while using a conventional growth method as it is.

  In particular, according to the present invention, by forming a large number of nanorods having InGaN quantum wells in an array and manufacturing an LED, the light emitted from the side wall can be used as it is, so that the light emission efficiency is greatly increased and the same area is obtained. An LED having significantly higher luminance than that of a conventional light emitting diode can be obtained.

  Further, according to the present invention, an LED that outputs visible light or white light having various wavelengths can be easily obtained by using the thickness of the InGaN quantum well, the content of In, and the use of a fluorescent material.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 (a) is a schematic view showing a cross-sectional structure of an LED according to a preferred embodiment of the present invention, and FIG. 1 (b) is a plan view showing a planar structure of the LED shown in FIG. 1 (a). FIG.

  The LED structure of this embodiment will be described with reference to FIGS. 1A and 1B. The LED of this embodiment has an n-type GaN buffer layer 20 and an array on a sapphire substrate 10. A plurality of GaN nanorods 31, 33, 35 arranged in a shape, a transparent insulating layer 41, a transparent electrode 60, and electrode pads 50, 70 embedded between GaN nanorods are formed.

  The n-type GaN buffer layer 20 formed on the substrate 10 buffers the lattice constant mismatch between the substrate 10 and the n-type GaN nanorods 31, and is shared by the n-type GaN nanorods 31 via the electrode pads 50. It plays a role of applying voltage.

  A large number of GaN nanorods 31, 33, 35 arranged in an array on the n-type GaN buffer layer 20 are each composed of an n-type GaN nanorod 31, an InGaN quantum well 33, and a p-type GaN nanorod 35. The multiple GaN nanorods have a substantially uniform height and diameter, and are formed perpendicular to the n-type GaN buffer layer 20.

Here, the InGaN quantum well 33 is an active layer that makes it possible to obtain visible light with higher luminance than a simple pn junction diode that does not have this, and in the present embodiment, it is shown in FIG. As described above, it has a multi quantum well structure in which a plurality of InGaN layers 33a and a plurality of GaN barrier layers 33b are alternately stacked. As will be described later, in particular, the interface between the InGaN layer 33a and the GaN barrier layer 33b of the multiple quantum well 33 of the present embodiment is very clean and has almost no dislocation.

A large number of GaN nanorods 31, 33, and 35 are embedded with a transparent insulator layer 41, so that each nanorod is insulated and the nanorods are protected from an impact applied to the nanorods. In addition, the transparent insulator layer 41 serves as a base layer that allows the transparent electrode 60 to be commonly connected to each nanorod. The material of the transparent insulating layer 41 is not particularly limited. However, the gap between the nanorods is sufficiently filled, and it can withstand heat such as a subsequent annealing process, so that the side wall light emission of the nanorod (see FIG. 1A). Transparent SOG, SiO ₂ or epoxy resin is used so as not to interfere with the left and right arrows). Also,
The transparent insulator layer 41 is formed slightly lower than the height of the p-type GaN nanorod 35 so that the tip of the p-type GaN nanorod 35 is connected to the transparent electrode 60 in common.

The transparent electrode 60 can be applied with an ohmic junction in common with the p-type GaN nanorod 35 to apply a voltage, and is a transparent conductive material so as not to interfere with light emission in the longitudinal direction of the nanorod (upward in the drawing). Consists of. The transparent electrode 60 is not particularly limited, but a thin Ni / Au thin film is used.

In a predetermined region on the transparent electrode 60, an electrode pad 70 is formed as a terminal for applying a voltage to the transparent electrode (that is, the p-type GaN nanorod). The electrode pad 70 is not particularly limited, but is made of a Ni / Au layer, and a wire (not shown) is bonded thereto. Further, an electrode pad 50 for applying a voltage to the n-type GaN nanorods via the n-type GaN buffer layer 20 is formed on the n-type GaN buffer layer 20 and is in ohmic contact with the n-type GaN buffer layer. The electrode pad 50 is not particularly limited, but is made of a Ti / Al layer, and a wire (not shown) is also bonded thereto.

When a DC voltage is applied to the two electrode pads 50 and 70 of the LED of this embodiment configured as described above (a (+) voltage is applied to the electrode pad 70 and a (−) voltage or a ground dislocation is applied to the electrode pad 50). Application), as shown in FIG. 1 (a), high-luminance light is emitted in the side wall direction and the longitudinal direction of the nanorod, each of which can be said to be a nano LED.

In particular, in this embodiment, since the InGaN quantum well is formed from each nanorod, visible light with higher luminance is emitted than a simple pn junction diode. In addition, the area of light emission (side wall light emission) is dramatically increased by a large number of nano LEDs, and the light emission efficiency is higher than that of conventional laminated film LEDs.

  On the other hand, the wavelength of the emitted light of the LED of the present embodiment can be variously adjusted by adjusting the amount of In in the InGaN quantum well or by adjusting the thickness of the quantum well 33, and white light can also be obtained. The details are as follows.

  First, when the In content in InGaN is increased, emission light from the ultraviolet region to all visible light regions such as blue, green, and red can be obtained using the phenomenon that the bandgap becomes smaller and the emission wavelength becomes longer. . Further, the emission wavelength can be changed by adjusting the thickness of the quantum well, that is, the InGaN layer 33a. That is, when the thickness of the InGaN layer is increased, the band gap is reduced, and the emitted light on the red side can be obtained.

  Furthermore, since the LED of this embodiment has a multiple quantum well structure as described above, white light can be obtained by using this. That is, by dividing the plurality of InGaN layers 33a of the multiple quantum well into several groups and adjusting the content of In in the InGaN layer for each group, for example, a blue light emitting group, a green light emitting group, etc. If a red light emitting group is formed, white light can be obtained as a whole. White light can also be obtained by using a fluorescent material. In particular, in the present embodiment, a white light-emitting LED is easily manufactured by adding a fluorescent material for obtaining white light to the transparent insulating layer 41. it can. For example, when the quantum well is configured so that the nanorods 30 emit blue light, and a yellow fluorescent material is added to the transparent insulator layer 41, white light can be emitted as a whole.

  Although the structure of the LED of the present embodiment has been described above, the specific structure and material can be variously modified. For example, in the above description, an n-type GaN layer is formed and a p-type GaN nanorod is formed thereon, but the n-type and p-type may be reversed. Further, the positions and shapes of the electrode pads 50 and 70 are not limited to the positions and shapes shown in FIGS. 1A and 1B, and are common to the n-type GaN nanorod 31 and the p-type GaN nanorod 35, respectively. Any other position and shape may be used as long as a voltage can be applied to.

In the above description, sapphire is used as the substrate 10, but a silicon substrate can also be used. In this case, unlike sapphire which is an insulator, silicon can be made into a conductor by adding an appropriate impurity (an n-type impurity if applied to the above embodiment mode). Therefore,
The n-type GaN buffer layer 20 is not required, and the electrode pad 50 does not need to be formed in a partial region on the n-type GaN buffer layer 20, and the lower surface of the silicon substrate (on the side opposite to the surface on which the nanorod 30 is formed). Surface).

  Next, a method for manufacturing the GaN LED of the present embodiment as described above will be described.

First, a method for growing GaN by an epitaxial growth method will be described. The epitaxial layer growth methods are roughly classified into VPE (Vapor Phase Epitaxial) growth method, LPE (Liquid Phase Epitaxial) growth method, and SPE (Solid Phase Epitaxial) growth method. is there. Here, the VPE growth method is a method in which a crystal is grown on a substrate through thermal decomposition and reaction while flowing a reaction gas over the substrate, and a hydride VPE (hydride VPE; HVPE) growth method depending on the form of the raw material of the reaction gas. , Halide V
It can be divided into PE (halide VPE) growth method and metalorganic VPE (MOVPE) growth method.

  In the present embodiment, it will be described that a GaN layer and an InGaN / GaN quantum well are formed by metal organic hydride vapor phase epitaxy (MO-HVPE), but the present invention is not limited to this method. The GaN layer and the InGaN / GaN quantum well can be preferably formed by other growth methods without being limited thereto.

GaCl, trimethylindium and NH ₃ are used as precursors for Ga, In and N, respectively. GaCl is obtained by reacting metal gallium and HCl at a temperature of 600 to 950 ° C. Impurity elements doped to grow n-type GaN and p-type GaN are Si and Mg, respectively, which are supplied in the form of SiH ₄ and Cp ₂ Mg (Bis (cyclopentadienyl) magnesium), respectively.

  Hereinafter, a method of manufacturing the GaN LED of this embodiment will be described in detail with reference to FIGS. 3 (a) to 3 (d).

First, as shown in FIG. 3A, a substrate 10 made of a sapphire wafer is placed in a reactor (not shown), and an n-type GaN buffer layer 20 is formed on the substrate 10. At this time, n-type GaN
The buffer layer 20 can be formed by doping Si as described above. However, GaN grown without artificial doping is basically n-type due to nitrogen vacancy, oxygen impurities, and the like. Has characteristics. Using this property, a precursor of Ga and N is supplied at a flow rate of 30 to 70 sccm and 1000 to 2000 sccm, respectively, at a temperature of 400 to 500 ° C., atmospheric pressure or slightly positive pressure without artificial doping, for 50 to 60 minutes. Thus, the n-type GaN buffer layer 20 having a thickness of about 1.5 μm can be grown.

Next, as shown in FIG. 3B, a nanorod array composed of a large number of nanorods 30 is formed. This process is continuously performed in the reactor in which the n-type GaN buffer layer 20 is grown. It is desirable to do it in-situ. Specifically, first, n-type GaN nanorods 31 are grown. The temperature is set to 400 to 600 ° C., atmospheric pressure or slightly positive pressure, and Ga and N precursors are flow rates of 30 to 70 sccm and 1000 to 2000 sccm, respectively, for 20 to 40 minutes. The n-type GaN nanorods 31 having a height of about 0.5 μm can be grown on the n-type GaN buffer layer 20 in the vertical direction by simultaneously supplying SiH ₄ at a flow rate of ₅ to 20 sccm. it can.

  On the other hand, normally, when GaN is grown at a high temperature (for example, 1000 ° C. or higher), the initially formed GaN seed rapidly grows not only in the upward direction but also in the lateral direction. It grows in the form of a thin film rather than a film. At this time, dislocations inevitably occur at the boundary where the seeds and the seeds grow sideways, and the dislocations propagate in the thickness direction along with the growth in the thickness direction of the thin film to generate thread dislocations. However, if the process conditions as in the above-described embodiment are maintained, seeds grow mainly upwards without a separate catalyst or template, and a large number of substantially uniform heights and diameters are obtained. N-type GaN nanorods 31 can be grown.

Next, an InGaN quantum well 33 is grown on the n-type GaN nanorod 31, and this process is also preferably performed continuously in situ in the reactor in which the n-type GaN nanorod 31 is grown. Specifically, the temperature is set to 400 to 500 ° C., atmospheric pressure or slightly positive pressure, and Ga, In and N precursors are supplied to the reactor at flow rates of 30 to 70 sccm, 10 to 40 sccm, and 1000 to 2000 sccm, respectively. As a result, InGaN quantum wells 33 are formed on the large number of n-type GaN nanorods 31. At this time, the time for growing the InGaN quantum well 33 is appropriately selected until the InGaN quantum well 33 is grown to a desired thickness. The thickness of the quantum well 33 determines the emission wavelength of the completed LED as described above. Since it becomes an element, the thickness may be set so as to be suitable for light having a desired wavelength, and the growth time may be determined thereby. Further, since the emission wavelength varies depending on the amount of In, the supply ratio of each precursor is adjusted according to the desired wavelength.

  Further, as shown in FIG. 2, the InGaN quantum well 33 may have a multiple quantum well structure formed by alternately laminating a plurality of InGaN layers 33a and a plurality of GaN barrier layers 33b. This is obtained by repeating the supply and blocking of the In precursor periodically for a predetermined time.

Next, p-type GaN nanorods 35 are grown on the InGaN quantum well 33. This process is also preferably performed in situ continuously in the reactor in which the InGaN quantum well 33 is grown. Specifically, a temperature 400 to 600 ° C., and atmospheric pressure or slightly positive pressure, fed to the reactor at a flow rate of each 30~70sccm and 1000~2000sccm precursors of 20-40 minutes Ga and N, at the same time Cp ₂ By supplying 5 to 20 sccm of Mg, a p-type GaN nanorod 35 having a height of about 0.4 mm can be grown in a direction perpendicular to the substrate 10.

  FIG. 4 is a scanning electron microscope photograph of the nanorod 30 array thus grown. As can be seen from FIG. 4, the nanorod 30 including the InGaN quantum well grown by the method of the present embodiment has a substantially uniform height and diameter and is formed (grown) at a fairly high density. On the other hand, the average diameter of the nanorods 30 grown under the above-described process conditions is about 70 to 90 nm at the site where the quantum wells 33 are formed, and the average gap between the nanorods 30 is about 100 nm.

After forming the nanorod 30 array in this way, the gap between the nanorods 30 is filled with the transparent insulator layer 40 as shown in FIG. As the transparent insulator used at this time, SOG, SiO ₂ or epoxy resin is suitable as described above. When embedding using SOG or epoxy resin, a spin coating and curing process is performed, so that FIG. The structure shown in c) is obtained. At this time, when the gap is filled using a transparent insulator, the gap between the nanorods 30 is preferably 80 nm or more so that the gap is completely filled. On the other hand, the thickness of the transparent insulator layer 40 is slightly lower than the height of the nanorods 30.

Next, as shown in FIG. 3D, electrode pads 50 and 70 for applying a voltage and a transparent electrode 60 are formed to complete a GaN LED having a nanorod array structure with InGaN quantum wells. To do. Specifically, in order to form the electrode pad 50 for applying a voltage to the n-type GaN nanorod 31 in the state of FIG. 3C, the transparent insulator layer 40 is exposed so that the n-type GaN buffer layer 20 is partially exposed. And a part of nanorod 30 is removed. Next, an electrode pad 50 is formed in a region where the n-type GaN buffer layer 20 is partially exposed using a lift-off process. The electrode pad 50 can be formed, for example, by using a Ti / Al layer by electron-beam evaporation. Next, in the same way, for example, Ni / Au
A transparent electrode 60 and an electrode pad 70 made of layers are formed.

  On the other hand, the transparent electrode 60 naturally comes into contact with the nanorods 30 protruding slightly from the transparent insulator layer 41, and as a result, is electrically connected to the n-type GaN nanorods 35. The transparent electrode 60 is preferably thin enough not to block the light emitted from the individual nano-LED below it, while external connection terminals such as wires are bonded to the two electrode pads 50 and 70, etc. It is preferable to have a sufficient thickness so as to be connected by the above method.

  As described above, according to the method of manufacturing a GaN LED according to the present embodiment, a nanorod composed of an n-type GaN nanorod 31, an InGaN quantum well 33, and a p-type GaN nanorod 35 continuously without a special catalyst or template. Can be uniformly grown in an array.

On the other hand, features that are not essential in the present embodiment can be modified in any number. For example, the formation procedure and method of the electrode pads 50 and 70 and the transparent electrode 60 can be variously modified into various known methods (evaporation, photolithography, etc.). In particular, each constituent substance in the above-described embodiment can be replaced with other known equivalent materials, and each process condition may deviate from the above-described exemplary range depending on the reactor and the material used.

In the above description, a sapphire wafer is used as the substrate 10, but a silicon wafer (preferably a silicon wafer doped with an n-type impurity such as phosphorus (P)) is used. In this case, as described above, the n-type GaN buffer layer 20 is unnecessary, and the electrode pad 50 can be formed not on a partial region on the GaN buffer layer 20 but on the lower surface of the silicon substrate. That is, an electrode pad is first formed on one surface of a silicon wafer, and the nanorods 30 may be formed directly on the opposite surface. Next, the light emission characteristics were examined for an example in which the above-described GaN LED of the present invention was manufactured as follows. This will be briefly described. However, the specific numerical values and methods presented in the following description are merely examples, and the present invention is not limited to the following description.

First, a sapphire (0001) wafer is prepared as the substrate 10 and the MO-HVP described above is prepared.
The n-type GaN buffer layer 20 and the GaN nanorods 30 were grown in situ using the E method and the precursor described above. Here, in the InGaN quantum well 33 in the nanorod 30, the composition ratio of In _x Ga _1-x N was set to In _0.25 Ga _0.75 N so that the emission wavelength of the completed LED was 470 nm or less. Further, a multiquantum well in which InGaN / GaN is repeated for six periods is used, and specific process conditions and results thereof are as shown in the following table.

In this way, a 33 mm ² area multiple quantum well nanorod array was obtained. The density of the nanorod array was about 8 × 10 ⁷ nanorods 30 in an area of 1 mm ² , the average diameter of the nanorods 30 was about 70 nm at the quantum well layer portion, and the height was about 1 μm. The carrier concentrations of the n-type and p-type GaN nanorods 31 and 35 were about 1 × 10 ¹⁸ cm ⁻³ and 5 × 10 ¹⁷ cm ⁻³ , respectively, and the composition ratio of the InGaN quantum well was In _0.25 Ga _0.75 N.

Next, SOG (trade name ACCUGLASS T-12B of Honeywell Electronic Materials Co., Ltd.) 30 so that the gaps between the high aspect ratio nanorods 30 are uniformly filled without voids.
Spin coating was performed for 30 seconds at a rotation speed of 00 rpm, and the film was cured by annealing at 260 ° C. for 90 seconds in the atmosphere. On the other hand, in this example, the spin coating and the curing process were performed in two steps so that the SOG sufficiently filled the gap. Then, the transparent insulator layer 40 having a thickness of about 0.8 to 0.9 mm was formed by annealing at 440 ° C. for 20 minutes in a furnace in a nitrogen atmosphere.

Next, a Ti / Al electrode pad 50 having a thickness of 20/200 nm is formed on the n-type GaN buffer layer 20 with a partial region exposed by a lift-off method using photolithography and dry etching and an electron beam evaporation method. Then, a 20/40 nm thick Ni / Au transparent electrode 60 was deposited so as to be in ohmic contact with each nanoscale LED 30. Finally, a 20/200 nm thick Ni / Au electrode pad 70 was formed in the same manner as the electrode pad 50.

  On the other hand, as a comparative example, a GaN LED having the same size and a laminated film shape was manufactured. The thickness and the configuration of each layer in the LED of the comparative example are the same as those of the embodiment of the present invention, except that they are not nanorods.

FIG. 5A is a graph showing an EL (electroluminescence) spectrum when a direct current of 20 to 100 mA is supplied to the LED of this example manufactured as described above. As shown in FIG. 5A, it can be seen that the LED of this example is a blue light emitting LED having a wavelength of about 465 nm. In addition, as shown in FIG. 5B, the LED of this example shows a blue-shift phenomenon in which the peak wavelength decreases as the supply current increases. This may be due to the screen effect of the built-in internal polarization field in the quantum well due to the injected carriers.

FIG. 6 is a graph showing IV characteristics at room temperature for the LED of this example and the LED of the comparative example. As shown in FIG. 6, the turn-on voltage of the LED of this example is slightly higher than that of the comparative example. This is because the effective contact area of the present example is much smaller than that of the comparative example (the LED of this example can be regarded as a collection of a large number of nano LEDs. Therefore, the contact area of each nano LED with the electrode 60 is small. This is considered to be because the resistance is so large compared to the comparative example.

FIG. 7 is a graph showing the light output with respect to the forward current, and it can be seen that the light output of the LED of this example is remarkably higher than that of the LED of the comparative example (4.3 times at 20 mA current). Yes, even if the detection area of the light detector is 1 mm ² , the light output actually felt will be larger than this). This is because, as described above, by forming the nanorod array, the side wall light emission is effectively used as compared with the laminated thin film LED having the same area. Moreover, it was confirmed from the temperature-dependent PL (Photoluminescence) experiment that the LED of this example has a significantly higher quantum efficiency.

On the other hand, FIG. 8 shows a case where an electrode is formed on one InGaN quantum well nanorod, and FIG. 9 is a graph showing IV characteristics in this case. In the nano LED having the structure shown in FIG. 8, after the nanorod array manufactured as described above is dispersed in methanol, the nanorod array is attached to a substrate such as an oxidized silicon substrate, on the n-type GaN nanorod 131 side. Is obtained by forming the Ti / Al electrode pad 150 and the Ni / Au electrode pad 170 on the p-type GaN nanorod 135 side. The IV characteristics of the nano LED composed of one nanorod thus obtained were examined. As can be seen from FIG. 9, this nano LED exhibits a very clean and accurate rectification characteristic. This is presumably because p and n-type nanorods and quantum wells were formed by single epitaxial growth.

  Although the present invention has been described with reference to the preferred embodiments, the embodiments described in this specification and the drawings are only the most desirable embodiments of the present invention, and limit the technical idea of the present invention. It should be understood that there are a variety of equivalents and variations that can be substituted at the time of this application.

FIG. 1A is a schematic diagram showing a cross-sectional structure of a light emitting diode according to a preferred embodiment of the present invention. FIG. 1B is a plan view showing a planar structure of the light emitting diode shown in FIG. FIG. 2 is a cross-sectional view showing a multiple quantum well structure of the light emitting diode shown in FIG. FIG. 3A is a cross-sectional view illustrating a process of manufacturing a light emitting diode according to an embodiment of the present invention. FIG. 3B is a cross-sectional view illustrating a process of manufacturing a light emitting diode according to an embodiment of the present invention. FIG. 3C is a cross-sectional view illustrating a process of manufacturing a light emitting diode according to an embodiment of the present invention. FIG. 3D is a cross-sectional view illustrating a process of manufacturing a light emitting diode according to an embodiment of the present invention. 1 is a scanning electron microscope (SEM) photograph of a nanorod array manufactured according to an embodiment of the present invention. FIG. 5A is a graph showing the EL intensity of the emission wavelength with respect to each current in the light-emitting diode manufactured according to the embodiment of the present invention. FIG. 5 (b) is a graph showing the peak wavelength for each current in the graph of FIG. 5 (a). FIG. 6 is a graph showing IV characteristics of a light emitting diode manufactured according to an embodiment of the present invention and a conventional light emitting diode. FIG. 7 is a graph showing light output-forward current characteristics of a light emitting diode manufactured according to an embodiment of the present invention and a conventional light emitting diode. FIG. 8 is a schematic view showing a light emitting diode composed of one GanN nanorod according to the present invention. FIG. 9 is a graph showing IV characteristics of the light emitting diode shown in FIG.

Explanation of symbols

10. . Substrate 20. . Buffer layer 31. . n-type GaN nanorods 33. . InGaN quantum well 33a. . InGaN layer 33b. . GaN barrier layer 35. . p-type GaN nanorods 41. . Transparent insulator layer 50. . Electrode pad 60. . Transparent electrode 70. . Electrode pad

Claims (8)

Forming a large number of first conductivity type GaN nanorods in a vertical direction of the substrate in an array at a temperature of 400 to 600 ° C. under atmospheric pressure or slightly positive pressure;
Forming an InGaN quantum well on each of the first conductivity type GaN nanorods at a temperature of 400 to 500 ° C. under atmospheric pressure or slightly positive pressure;
Forming GaN nanorods of the second conductivity type on the InGaN quantum well, respectively, at a temperature of 400 to 600 ° C. under atmospheric pressure or slightly positive pressure;
Forming an electrode pad for applying a voltage to the first conductivity type GaN nanorod;
Forming a transparent electrode connected to the second conductivity type GaN nanorods in common and applying a voltage.   Subsequent to the step of forming the second conductivity type GaN nanorod, a step of embedding a transparent insulator between nanorods composed of the first conductivity type GaN nanorod, the InGaN quantum well, and the second conductivity type GaN nanorod. The method of manufacturing a light emitting diode according to claim 1, further comprising: The transparent insulating material, SOG (Spin-On-Glass ), The method as claimed in claim 2, characterized in that a SiO ₂ or an epoxy resin.   3. The method of manufacturing a light emitting diode according to claim 2, wherein a fluorescent material is added to the transparent insulator so that light emitted from the light emitting diode becomes white light as a whole. The step of forming the quantum well is a step of forming a multiple quantum well by alternately repeating a step of forming an InGaN layer and a step of forming a GaN barrier layer. 2. A method for producing a light-emitting diode according to 1. The first conductivity type GaN nanorod, the InGaN quantum well, and the second conductivity type GaN nanorod are formed in-situ by an MO-HVPE (metalorganic-hydride vapor phase epitaxy) method. The method of manufacturing a light emitting diode according to claim 1, wherein   The substrate is a sapphire substrate, and before the step of forming the first conductivity type GaN nanorods, the first conductivity type GaN buffer layer is placed on the sapphire substrate at a temperature of 400 to 500 ° C. at atmospheric pressure or slightly. The method of claim 1, further comprising forming under a positive pressure, wherein the electrode pad is formed in a partial region on the GaN buffer layer. The method of claim 1, wherein the substrate is a silicon substrate, and the electrode pad is formed on a surface of the silicon substrate opposite to a surface on which nanorods are formed.

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