KR20000041281A - Nitride system semiconductor device and method for growing semiconductor crystal - Google Patents

Abstract

PURPOSE: A nitride system semiconductor device and method for growing a semiconductor crystal is to prevent incoherence of lattice from being occurred at the boundary of two stacked layers. CONSTITUTION: A nitride system semiconductor device comprises a substrate, a BN system compound buffer layer formed on the substrate and containing boron and nitrogen atoms and a nitride system semiconductor crystal layer formed on the BN system compound buffer layer. A method for growing a semiconductor crystal comprises the steps of: providing a substrate; epitaxial growing a BN system compound on the substrate at a first temperature to form a buffer layer; and forming a nitride system semiconductor crystal layer on the buffer layer at a second temperature higher than the first temperature.

Description

Nitride-based Semiconductor Devices and Nitride-based Semiconductor Crystal Growth Methods

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor device. In particular, a nitride semiconductor device and a nitride semiconductor crystal growth method capable of forming a nitride crystal layer having excellent crystallinity by forming a BN compound buffer layer between a substrate and a nitride single crystal. It is about.

In recent years, light emitting devices capable of emitting light (ultraviolet to green), especially blue light in the short wavelength region have been in the spotlight, and nitride compounds such as GaN, InN, and AlN, and nitride compounds in which these nitrides are mixed at a constant ratio are used as light of these wavelengths. It has an energy gap capable of emitting light.

The growth of such nitride-based semiconductor crystals uses a metal organic chemical vapor deposition (MOCVD) method. The MOCVD method is a method of growing an epitaxial layer of crystals on a substrate by supplying an organic compound reaction gas into a reaction vessel mainly at a temperature of 900 to 1100 ° C. A sapphire substrate or a SiC substrate is used as the substrate. The reason for using the sapphire substrate or the SiC substrate is that there is no commercial substrate which has the same crystal structure as the grown nitride crystal and achieves lattice matching.

However, in the case of growing nitride-based semiconductor crystals on the sapphire substrate or SiC substrate by using the conventional MOCVD method, the morphological characteristics of the grown epitaxial layer surface are poor and stress due to lattice mismatch is generated. Therefore, it was very difficult to obtain crystals having good characteristics, and as a result, it was almost impossible to develop a light emitting device emitting blue light.

In order to solve this problem, the proposed semiconductor device is a device in which an epitaxial layer is grown after forming a buffer layer of AlN on a sapphire substrate as shown in FIG. The device forming method is to grow GaAlN into hundreds of layers at a temperature of about 400 to 900 DEG C, which is much lower than the growth temperature (about 1000 to 1100 DEG C) of a normal GaAlN crystal, and then grow a GaAlN epitaxial layer thereon. will be. The low temperature growth layer is called a buffer layer because it is formed between the sapphire substrate and the nitride semiconductor crystal to improve the crystallinity of the semiconductor. The morphological characteristics and lattice matching of the epitaxial layer were improved by the buffer layer, and light emitting devices having a short wavelength region, particularly blue light, began to be developed.

However, in the semiconductor device of the above structure, it is necessary to strictly limit the growth conditions of the buffer layer. In particular, although the buffer layer must be set to a thin thickness of 100 to 500 되고 and the thickness must be uniformly formed over the sapphire substrate, the growth of such a buffer layer was very difficult. In addition, the crystallinity was not improved until fabrication of light emitting diodes or light emitting semiconductors, and it was not possible to realize pn junctions for practical use of light emitting diodes.

Therefore, the semiconductor device proposed for manufacturing the blue light emitting device is a semiconductor device having the structure shown in FIG. In this semiconductor device, a GaN buffer layer is epitaxially grown on a sapphire substrate at a temperature in the range of about 400 to 800 ° C. in a range of about 0.02 to 0.2 μm, and the GaN nitride crystals in the temperature range of 900 to 1150 ° C. are higher on the sapphire substrate. Grows tactical. The low temperature grown buffer layer reduces the difference in lattice constant between the sapphire substrate and the nitride, thereby reducing stress, thereby obtaining high quality nitride crystals, and enabling the growth of light emitting devices such as light emitting diodes and light emitting semiconductors. The above structure is equally useful for Ga _x Al _1-x N buffer layers and Ga _x Al _1-x N nitride crystals.

However, lattice mismatch exists in the semiconductor device of the above structure. In Fig. 9, the relationship between energy gap and lattice constant for each material is shown. Looking at the graph, it can be seen that the sapphire has a lattice constant of about 2.6 Å, AlN about 3.1 Å, GaN about 3.15 Å and InN about 3.5 Å. Therefore, the difference between the gap constants of GaN and sapphire is about 0.55 GPa. When the lattice constant of this degree is applied to an actual light emitting device, lattice mismatch occurs, which in turn causes a decrease in crystallinity of the nitride-based crystal layer. In addition, since the lattice aberration between sapphire and AlN is about 0.5 dB, the crystallinity of the nitride-based crystal layer is lowered even when a Ga _x Al _1-x N buffer layer of GaN and AlN is formed.

On the other hand, the difference between the lattice constants of sapphire and InN is about 0.9 mm, which is larger than the difference between the lattice constants of the two materials. Therefore, it is not preferable to form an InN buffer layer, and it can be seen that any compound of AlN, GaN, InN fine materials is not suitable as a buffer layer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and a nitride which can prevent lattice mismatching at an interface by forming a BN compound buffer layer between a nitride semiconductor crystal layer and a material having a different lattice constant from the crystal layer. An object of the present invention is to provide a semiconductor semiconductor device and a crystal growth method.

Another object of the present invention is to form a BN compound buffer layer on a substrate during growth of a nitride semiconductor crystal layer on a sapphire substrate or a SiC substrate to prevent the lattice mismatch between the substrate and the crystal layer to prevent crystallinity of the nitride crystal layer. To provide a nitride-based semiconductor device and a crystal growth method that can be improved.

It is still another object of the present invention to provide a nitride-based semiconductor device capable of improving the light emission efficiency and increasing the light emission lifetime by forming a BN compound buffer layer on a substrate, and a method of manufacturing the same.

In order to achieve the above object, the nitride semiconductor device according to the first aspect of the present invention is a sapphire substrate or SiC substrate, a BN compound buffer layer formed on the substrate, and a nitride semiconductor crystal layer formed on the BN compound buffer layer It consists of.

The BN compound buffer layer formed on the substrate includes Ga _1-x B _x N (0 <x≤1), Al _1-x B _x N (0 <x≤1), In _1-x B _x N (0 <x ≤1), ((Al _1-y Ga _y ) _1-x B _x ) N (0 <x≤1,0≤y≤1), ((In _1-y Ga _y ) _1-x B _x ) N (0 <x≤1,0≤y≤1), ((In _1-y Al _y ) _1-x B _x ) N (0 <x≤1,0≤y≤1) or ((Al _a Ga _b In _c ) _1-x B _x ) N (0 <x≤1, a + b + c = 1, a, b, c ≠ 0), and the nitride-based semiconductor crystal layer is composed of AlN, GaN, InN materials It consists of at least one substance.

In addition, the nitride semiconductor device according to the second aspect of the present invention is a sapphire substrate or SiC substrate, a BN compound buffer layer formed on the substrate, an n-type nitride semiconductor crystal layer formed on the buffer layer, and the n-type nitride-based An active layer formed on the semiconductor crystal layer and made of intrinsic nitride-based semiconductor crystals to emit light as a voltage is applied; a p-type nitride semiconductor crystal layer formed on the active layer; and a first electrode and a voltage applied to the active layer. It consists of two electrodes.

The BN compound forming the buffer layer is made of BN and at least one material selected from the group consisting of AlN, GaN, and InN, and the n-type or p-type nitride-based semiconductor crystal layer is an n-type dopant or a p-type plate The doped AlN, GaN, InN material is made of at least one material and the intrinsic nitride-based semiconductor crystal layer is made of at least one material of AlN, GaN, InN material. The active layer includes at least one quantum well.

When the substrate is made of a sapphire substrate which is a non-conductor, the n-type electrode is formed on the n-type nitride crystal layer from which a part is removed, and when the substrate is made of SiC, which is a conductor, the n-type electrode is formed on the substrate surface.

1 is a view showing the structure of a conventional nitride based semiconductor device.

2 is a view showing the structure of another conventional nitride semiconductor device.

3 is a view showing the structure of a nitride-based semiconductor device according to the present invention.

4 is a view showing an example of a structure of a blue light emitting diode to which a nitride based semiconductor device according to the present invention is applied.

5 is a view showing another example of a structure of a blue light emitting diode to which a nitride based semiconductor device according to the present invention is applied.

6 is a view showing another example of a structure of a blue light emitting diode to which a nitride based semiconductor device according to the present invention is applied.

7 is a view showing another example of a structure of a blue light emitting diode to which a nitride based semiconductor device according to the present invention is applied.

8 (a) to 8 (c) are graphs showing the characteristics of the nitride semi-elements according to the present invention.

9 is a graph showing lattice constants of sapphire used as a substrate and a material forming a buffer layer.

The most basic object of the present invention is a method of forming a nitride semiconductor in a material having a different lattice constant. Since the difference in lattice constant between the two materials causes lattice mismatch at the interface, in order to grow nitride-based semiconductor crystals, a buffer layer must be formed to match the lattice between the two materials.

In the present invention, a BN compound is used instead of the material used as a conventional buffer layer for lattice matching. The lattice constant of BN is about 2.4 Hz as shown in FIG. Therefore, lattice phase aberration of about 0.2 Hz occurs with sapphire mainly used as a substrate. It can be seen that this value is very small compared to the gap retardation between the material and the sire used in the conventional buffer layer described above. Therefore, the compounds of BN and AlN, the compounds of BN and GaN, and the compounds of BN and InN all have only a small lattice phase difference with the sapphire substrate. In addition, even when the buffer layer is formed of two or more of AlN, GaN, and InN and the compound of BN, the lattice mismatch between the substrate and the buffer layer is greatly reduced since the lattice retardation is smaller than that of the conventional buffer layer.

Hereinafter, the present invention will be described with reference to the nitride semiconductor device shown in FIG. 3. The buffer layer formed on the sapphire substrate is composed of a compound of (Ga _1-x B _x ) N, on which a GaN single crystal is grown. A method of forming a nitride-based semiconductor device having such a structure is to first epitaxially grow a (Ga _1-x B _x ) N buffer layer on a sapphire substrate at a low temperature of a first temperature, and then, on the buffer layer, a second higher than the first temperature. The GaN crystal layer is grown at a temperature.

The (Ga _1-x B _x ) N buffer layer can be formed to a thickness of about 10 to 1000 GPa, preferably about 100 to 600 GPa, and more preferably about 200 to 300 GPa. Further, the first temperature for growing the (Ga _1-x B _x ) N buffer layer is about 200 to 1000 占 폚, more preferably about 500 to 600 占 폚.

The (Ga _1-x B _x ) N buffer layer and the nitride-based semiconductor crystal layer are formed by a general semiconductor device growth method, and the crystal growth method of the nitride-based semiconductor according to the present invention will be described as follows. . When the (Ga _1-x B _x ) N layer is grown at a low temperature of about 500 to 600 ° C., the (Ga _1-x B _x ) N layer is in an amorphous state. This amorphous (Ga _1-x B _x ) N buffer layer is partially crystallized as the growth temperature is gradually raised to about 1000 ° C. or more. That is, when the sapphire substrate is installed in the reaction vessel and the organic compound gas is supplied to epitaxially grow the crystal layer, first, a mixed gas containing boron (B) is supplied, and the temperature is maintained at 500 to 600 ° C. on the sapphire substrate. After forming a compound buffer layer made of (Ga _1-x B _x ) N, the temperature in the reaction vessel is gradually raised to supply a reaction gas containing no boron at a temperature of about 1000 ° C. or more to epitaxially grow the GaN crystal layer.

As the temperature rises, the amorphous (Ga _1-x B _x ) N buffer layer is partially crystallized. The rise in temperature dlsrk the activation energy to each atom in the (Ga _1-x B _x ) N buffer layer, which is moved to the lattice point of each valence lattice structure by this activation energy. And crystallize. In practice, this crystallization does not produce a complete single crystal state. Since crystallization proceeds locally, the actual buffer layer has a polycrystalline structure with small grain boundaries. This polycrystal acts as a seed crystal when forming a GaN crystal layer on the buffer layer. That is, when epitaxially growing GaN of about 1000 ° C. or more, a GaN single crystal layer is uniformly formed from the seed crystal.

The (Ga _1-x B _x ) N buffer layer grown at a temperature of about 200 to 1000 ° C., preferably at a temperature of about 500 to 600 ° C., may not be in an amorphous state but in a small grain polycrystalline state. Such an amorphous state or a polycrystalline state is formed differently depending on the conditions when epitaxially growing a (Ga _1-x B _x ) N layer, but there is no problem in acting as a buffer layer. As described above, even when the amorphous (Ga _1-x B _x ) N buffer layer is grown, when the temperature is increased to grow the GaN crystal layer, the GaN _-x B _x interface with the GaN crystal layer is formed. Since a polycrystalline layer is formed in the N buffer layer, a GaN crystal layer having high crystallinity can be obtained. (Ga _1-x B _x) of the in the case of direct growth of GaN crystal layer from the amorphous state of the N buffer layer, a short-range order (short range order) only the amorphous state of having (Ga _1-x B _x) N buffer layer and the crystalline state Since no lattice mismatch occurs between the GaN crystal layers, a GaN crystal layer having high crystallinity can be obtained.

In fact, in the case of forming the (Ga _1-x B _x ) N buffer layer at low temperature (about 500 to 600 ° C), an amorphous phase and a small crystal grain boundary are mixed in the buffer layer. Such an amorphous or polycrystalline buffer layer enables the growth of a uniform single crystal layer thereon. In other words, the buffer layer growing the high crystallinity single crystal layer must be lattice matched with the single crystal layer at the interface, and the buffer layer in the amorphous state or the polycrystalline state achieves excellent coherence with the single crystal layer. Therefore, the buffer layer phase of the present invention can be either an amorphous phase or a polycrystalline phase except for a single crystal phase, and in other words, it can be referred to as a non-single crystal phase. Non-single-crystal phase described in the detailed description or claims of the present invention means that the state of the buffer layer (or other layer) is an amorphous state, a polycrystalline state with a small grain boundary, or a mixed state thereof.

As the BN compound is used as a buffer layer by adding BN to a material used as a conventional buffer layer, lattice mismatch between the buffer layer and the crystal layer is further reduced. As shown in FIG. 9, since the lattice aberration between BN and sapphire is much smaller than the lattice aberration between a material mainly used as a buffer layer, for example, AlN, GaN, InN, and sapphire, the BN is As it is added, the gap retardation between the buffer layer and the crystal layer is reduced, thereby reducing lattice mismatch, and as a result, a crystal layer having good crystallinity can be formed.

In addition, the use of BN-based BN-based compounds causes an increase in the ductility of the buffer layer. BN having a hexagonal or wurtzite crystal structure is more ductile and easier to dopant than other materials forming the buffer layer. Therefore, when a certain ratio of BN is added to the conventional material forming the buffer layer to form a compound, the ductility of the compound increases and the difference in lattice constant with the crystal layer can be further reduced by the increased ductility, thereby determining It is possible to obtain a better monocrystalline layer academically.

Table 1 compares the characteristics of the GaN single-crystal layer of GaN when the conventional GaN buffer layer and the (Ga _1-x B _x ) N buffer layer of the present invention are grown.

Buffer layer GaN buffer layer Ga _1-x B _x N buffer layer (x = 0.05) Saint temperature 550 ℃ 550 ℃ Growth thickness 300 yen 300 yen Mobility 304cm ² / Vs 340cm ² / Vs DXW's FWHM 550arcsec 400arcsec Electron density 3.2 × 10 ¹⁷ / cm ³ 2.46 × 10 ¹⁷ / cm ³

The GaN buffer layer and the Ga _1-x B _x N buffer layer (x = 0.05) were both grown to a thickness of about 300 GPa at about 550 ° C., and the GaN single crystal layer on the buffer layer was grown to a thickness of about 2 μm as an n-type single crystal layer.

As shown in the table, the GaN single crystal layer grown on the GaN buffer layer has a mobility of about 304 cm ² / Vs, and the GaN single crystal layer formed on the Ga _1-x B _x N buffer layer has a mobility of about 340 cm ² / Vs. Have That is, when the GaN single crystal layer is formed on the Ga _1-x B _x N buffer layer, mobility increases. This increase in mobility is due to a decrease in defects in the single crystal layer, and is due to a decrease in scattering caused by defects when electrons move in the single crystal layer. Therefore, when light emitting devices such as semiconductor lasers and light emitting diodes are made, the mobility of electrons in the n-type single crystal layer and the p-type single crystal layer is improved, thereby improving the luminous efficiency of the light emitting device.

In addition, the Full Width a Half Maximum (FWHM) measured by DXRD decreased from about 550 arcsec to about 400 acrsec. Therefore, the variation of atoms at the lattice point of the single crystal was reduced, which means that the crystallinity of the GaN single crystal layer was improved. The electron density decreased from about 3.2 × 10 ¹⁷ / cm ³ to about 2.46 × 10 ¹⁷ / cm ³ .

Table 2 shows the electron mobility, FWHM and electron density characteristics of the GaN single crystal layer when the Ga _1-x B _x N buffer layer with different composition ratios of boron (B) was grown. In (c), a graph is shown for each of these characteristics.

M% of boron 0 5 10 100 Mobility 304 340 335 270 FWHM 550 400 410 600 Electron concentration 3.2 × 10 ¹⁷ 2.46 × 10 ¹⁷ 2.6 × 10 ¹⁷ 3.8 × 10 ¹⁷

As shown in Table 2 and Fig. 8, when boron is added to the buffer layer in a certain amount, that is, about 5 to 10 m% (corresponding to x = 0.05 to 0.1 in Ga _1-x B _x N), as compared to when boron is not added. The electrical mobility, FWHM and electron concentration characteristics of the single crystal layer were improved, and as the composition ratio of boron was increased, the characteristics were lowered again.

As the substrate on which the buffer layer is grown, a SiC substrate may be used instead of the sapphire substrate. Since the SiC substrate itself is made of a semiconductor material, current can be conducted when a voltage is applied, and thus the SiC substrate can be usefully used when the nitride-based semiconductor device of the present invention is applied to a light emitting device. However, like the sapphire substrate, the SiC substrate also requires a buffer layer because stress due to lattice mismatch occurs at the interface when a nitride-based single crystal is formed thereon.

The buffer layer of the present invention may be a compound other than Ga _1-x B _x N. As shown in FIG. 9, since BN itself has a small lattice aberration with the sapphire substrate, a material conventionally used as a buffer layer, that is, AlN, GaN and InN and the compound of BN also improves the crystallinity of the single crystal layer. Can be used as a good buffer layer.

That is, Ga _1-x B _x N (0 <x≤1), Al _1-x B _x N (0 <x≤1), In _1-x B _x N (0 <x≤1), ((Al _1-y Ga _y ) _1-x B _x ) N (0 <x <1,0≤y≤1), ((In _1-y Ga _y ) _1-x B _x ) N (0 <x <1, 0≤y≤1), ((Al _a Ga _b In _c ) _1-x B _x ) N (0 <x <1, a + b + c = 1, where a, b, c is not 0), etc. The same BN compound may be used as the buffer layer. The buffer layer comprises a reaction gas composed of the above-exemplified compounds at about 10 to 1000 Pa, preferably about 100 to 600 Pa, more preferably about 200 to 1000 C at a first temperature of about 200 to 1000 ° C., preferably about 500 to 600 ° C. It is formed by growing to a thickness of 300 GPa, on which a nitride semiconductor single crystal layer is epitaxially grown at a second temperature higher than the first temperature.

The single crystal layer can grow any material made of a nitride semiconductor. That is, any nitride compound semiconductor such as InN, GaN, AlN, In _1-x Ga _x N, Al _1-x Ga _x N, AlIn _1-x Ga _x N, or the like may be used. A semiconductor made of the above material is epitaxially grown at a second temperature of about 1100 ° C. or higher than the first temperature. The single crystal layer is formed by growing a buffer layer at a first temperature and then supplying a reaction gas to the reaction vessel while gradually raising the temperature to the second temperature.

A nitride semiconductor device in which a buffer layer made of the above-described BN compound is formed between a substrate and a nitride semiconductor single crystal layer can be used for a light emitting diode for blue light. 4 to 7 show the structure of such a light emitting diode.

First, referring to the structure of the light emitting diode shown in FIG. 4, a BN compound buffer layer is formed on a sapphire substrate, and an n-type nitride single crystal layer is formed thereon. BN compound buffer layer is a compound consisting of BN and AlN, GaN, InN Ga _1-x B _x N, Al _1-x B _x N, In _1-x B _x N, ((Al _1-y Ga _y ) _{1 -x} B _x ) N, ((In _1-y Ga _y ) _1-x B _x ) N, ((Al _a Ga _b In _c ) _1-x B _x ) N, etc., about 200 to 1100 ° C Is epitaxially grown to a thickness of about 10 to 1000 kPa, preferably about 100 to 600 kPa, more preferably about 200 to 300 kPa at a first temperature of about 500-600 ° C. The buffer layer generated at the temperature has an amorphous structure or a polycrystalline structure having a small grain boundary, or a mixture of an amorphous structure and a polycrystalline structure.

The n-type nitride-based crystal layer has a single crystal structure, and GaN, AlN, In _1-x Ga _x N, Al _1-x at a second temperature of about 1000 ° C. or more higher than the first temperature on the BN compound buffer layer. It is formed by epitaxially growing a nitride semiconductor such as Ga _x N, AlIn _1-x Ga _x N, or the like and then doping an n-type dopant. Doping of the n-type dopant is performed by performing ions of C, Si, Ge, Se, S, Sn, Te, Be, O and the like in a general doping method.

On the n-type nitride-based crystal layer, an active layer made of a nitride-based single crystal is formed. The active layer is formed by epitaxially growing nitride-based intrinsic semiconductors such as GaN, AlN, In _1-x Ga _x N, Al _1-x Ga _x N, AlIn _1-x Ga _x N and the like which are not doped with impurities. The active layer is a light emitting area that emits light due to a transition of a carrier when a voltage is applied to the light emitting diode, and may be formed of a plurality of layers having different energy gaps. The plurality of layers may be formed in quantum wells in the energy gap, and may be formed in two layers or three or more layers in order to form a multi-quantum well.

The method of forming the quantum well in the active layer is to vary the composition ratio of the nitride-based material forming the active layer. For example, when Al _1-x Ga _x N is epitaxially grown to form an active layer, quantum wells may be formed by forming a plurality of layers by varying a composition ratio of Al and Ga, that is, x values. Since the carrier is trapped at a low energy level of the quantum well, the carrier is smoothly transitioned between the energy gaps when voltage is applied, thereby greatly increasing the luminous efficiency. The active layer having a quantum well can also be carried out by forming a plurality of layers made of different compounds. For example, In _1-x Ga _x N / GaN, In _1-x Ga _x N / In _1-y Ga _y N, In _1-x Ga _x N / Al _1-z Ga _z N (where x≤ A plurality of layers made of y, 0 ≦ x, y, z ≦ 1) and the like may also be used as the active layer having a quantum well.

In this case, one layer, for example, a specific layer such as a GaN layer, may be formed, and a plurality of In _1-x Ga _x N layers may be formed while changing the x value again. In this case, the energy level of the GaN layer acts as a potential barrier and the plurality of In _1-x Ga _x N layers form multiple quantum wells so that most of the carriers are trapped in the quantum wells. In addition, by forming at least one layer of the active layer as a compound to which materials having different energy gaps are added, potentials having different energy levels may be formed according to composition ratios.

A p-type nitride single crystal layer is formed on the active layer. Like the n-type nitride-based single crystal layer, the p-type nitride-based single crystal layer is formed of an active layer of nitride semiconductor such as GaN, AlN, In _1-x Ga _x N, Al _1-x Ga _x N, AlIn _1-x Ga _x N, or the like. It is formed by epitaxial growth on top, and the p-type dopant is doped. As the p-type dopant, Mg, Zn, Cd, Be, Ca, Sr, Ba and the like are used.

The n-type nitride-based crystal layer, the active layer, and the p-type nitride-based crystal layer are p-n junction active layers that are activated when voltage is applied, and are light emitting regions that actually emit light.

As shown in the figure, a portion of the n-type nitride-based crystal layer is removed, and an n-type electrode made of a metal having good conductivity is formed in the removed region. A p-type electrode made of a metal is also formed on the p-type nitride based single crystal layer. As voltage is applied through the electrode, light begins to be emitted from the light emitting region.

Generally, sapphire substrates are insulators. Therefore, in order to apply a voltage to the active layer, in the light emitting diode of the present invention, one part of the n-type nitride-based crystal layer was removed and an electrode was formed thereon. When applied to an electrode in a light emitting diode having such a structure, current flows between the p-type electrode on the p-type nitride-based crystal layer and the n-type electrode formed on the n-type nitride-based crystal layer over the entire active layer, resulting in light emission from the active layer. do.

The electrode uses a highly conductive metal, and its type generally depends on the material of the n-type nitride-based crystal layer and the p-type nitride-based crystal in contact with the electrode. As a method of forming the electrode, a general metal lamination method, for example, evaporation or sputtering may be used.

The structure of the light emitting diodes shown in FIGS. 5 and 6 is basically the same as that of the light emitting diodes shown in FIG. 4. The only difference is that the electrodes are formed at different positions, and the light emitting diode having such a structure is made because the sapphire substrate is an insulator. Therefore, the electrodes of the light emitting diodes shown in Figs. 4 to 6 are formed on both the n-type nitride crystal layer and the p-type nitride crystal layer. In particular, in order to allow a current to flow through the whole of the active layer when a voltage is applied, a portion of the n-type nitride-based crystal layer is removed, and then an n-type electrode is formed in the removed region.

In the light emitting diode shown in Fig. 7, a SiC substrate is used. Since SiC is a semiconductor material, current flows when a voltage is applied. Therefore, as shown in the figure, the electrode can be formed on the lower surface of the substrate. The advantage of such a structure is that the light emitting area of the diode can be formed in the same width direction of the entire light emitting diode, and even when a voltage is applied to the electrode, the light emitting efficiency is greatly improved since the current flows uniformly throughout the light emitting area.

The same buffer layer as the light emitting diodes shown in FIGS. 4 to 6 is formed on the SiC substrate, and a nitride based single crystal layer is formed thereon. The nitride single crystal layer is composed of a p-type nitride single crystal layer, an intrinsic nitride single crystal layer, and an n-type nitride single crystal layer. The buffer layer is a non-single-crystal layer made of a BN-based compound, thereby improving the crystallinity of the nitride-based single crystal layer by preventing mismatch between the SiC substrate and the nitride-based single crystal layer.

The nitride semiconductor device of the present invention can be applied to a general light emitting device made of a nitride semiconductor. Not only the light emitting diode but also the light emitting device in which p-n junction of a nitride semiconductor is formed on a substrate, such as a light emitting transistor, all of the light emitting devices having high efficiency can be easily manufactured using the concept of the present invention. In addition, the crystal growth method of the nitride semiconductor of the present invention is not limited to a specific device. The present invention relates to a method of growing a nitride semiconductor on a material having a different lattice constant, and is not limited to the method of growing a crystal in a specific device.

As described above, when forming a nitride-based crystal layer by forming a BN-based compound buffer layer on a sapphire substrate or a SiC substrate, the lattice mismatch is reduced between the substrate and the nitride buffer layer to reduce the crystallinity of the crystal layer. Improve. In addition, when a light emitting device such as a light emitting diode is manufactured by improving the crystallinity, not only the light emission characteristics and the electrical characteristics are improved, but also the crystallinity is improved, so that the reliability, that is, the operation life is greatly increased.

Claims (55)

Board; A BN compound buffer layer formed on the substrate; And A nitride semiconductor device comprising a nitride semiconductor crystal layer formed on the BN compound buffer layer. The nitride-based semiconductor device according to claim 1, wherein the BN compound buffer layer is a non-single crystal layer. The nitride-based semiconductor device according to claim 2, wherein the BN compound buffer layer is an amorphous layer. The nitride-based semiconductor device according to claim 2, wherein the BN compound buffer layer is a polycrystalline layer. The nitride-based semiconductor device according to claim 2, wherein the BN compound buffer layer is a layer in which an amorphous phase and a polycrystalline phase are mixed. The nitride-based semiconductor device according to claim 1, wherein the substrate is a sapphire substrate or an SiC substrate. The nitride-based semiconductor device according to claim 1, wherein the BN compound buffer layer has a thickness of 100 to 600 GPa. The nitride-based semiconductor device according to claim 7, wherein the BN compound buffer layer has a thickness of 200 to 300 GPa. The nitride-based semiconductor device according to claim 1, wherein the BN compound comprises at least one material selected from the group consisting of AlN, GaN, and InN and BN. The nitride based semiconductor device according to claim 9, wherein the BN compound is Ga _1-x B _x N (0 <x ≦ 1). The nitride-based semiconductor device according to claim 9, wherein the BN compound is Al _1-x B _x N (0 <x ≦ 1). The nitride-based semiconductor device according to claim 9, wherein the BN compound is In _1-x B _x N (0 <x ≦ 1). The nitride-based semiconductor device according to claim 9, wherein the BN compound is ((Al _1-y Ga _y ) _1-x B _x ) N (0 < _x ≦ 1,0 ≦ _y ≦ 1). The nitride-based semiconductor device according to claim 9, wherein the BN compound is ((In _1-y Ga _y ) _1-x B _x ) N (0 < _x ≦ 1,0 ≦ _y ≦ 1). The nitride-based semiconductor device according to claim 19, wherein the BN compound is ((In _1-y Al _y ) _1-x B _x ) N (0 < _x ≦ 1,0 ≦ _y ≦ 1). The method according to claim 9, wherein the BN compound is ((Al _a Ga _b In _c ) _1-x B _x ) N (0 <x≤1, a + b + c = 1, a, b, c ≠ 0) A nitride-based semiconductor device characterized in that. The nitride-based semiconductor device according to claim 1, wherein the nitride-based semiconductor crystal layer is made of at least one of AlN, GaN, and InN materials. Providing a substrate; Epitaxially growing a BN compound at a first temperature on the substrate to form a buffer layer; And Forming a nitride semiconductor crystal layer on the buffer layer at a second temperature higher than the first temperature. 19. The crystal growth method according to claim 18, wherein the first temperature is 200 to 1000 deg. 20. The crystal growth method according to claim 19, wherein the first temperature is 500 to 600 deg. 19. The crystal growth method according to claim 18, wherein the second temperature is 1000 deg. 19. The method of claim 18, wherein the nitride semiconductor crystal layer is made of at least one of AlN, GaN, and InN materials. A first layer made of a first material; A second layer made of a second material having a nitride-based semiconductor crystal structure having a different lattice constant from the first material; And And a BN compound buffer layer formed between the first layer and the second layer to lattice match the first layer and the second layer. 24. The nitride based semiconductor device as claimed in claim 23, wherein said BN compound buffer layer is a non-single crystal layer. 25. The nitride semiconductor device according to claim 24, wherein the BN compound buffer layer is an amorphous layer. 25. The nitride semiconductor device according to claim 24, wherein said BN compound buffer layer is a polycrystalline layer. The nitride based semiconductor device according to claim 24, wherein the BN compound buffer layer is a layer in which an amorphous phase and a polycrystalline phase are mixed. Board; A BN compound buffer layer formed on the substrate; An n-type nitride semiconductor crystal layer formed on the buffer layer; An active layer formed on the n-type nitride-based semiconductor crystal layer and made of intrinsic nitride-based semiconductor crystal to emit light as a voltage is applied; A p-type nitride semiconductor crystal layer formed on the active layer; And A nitride based semiconductor device comprising a first electrode and a second electrode for applying a voltage to the active layer. 29. The nitride based semiconductor device as claimed in claim 28, wherein said BN compound buffer layer is a non-single crystal layer. 30. The nitride semiconductor device according to claim 29, wherein the BN compound buffer layer is an amorphous layer. The nitride based semiconductor device according to claim 29, wherein said BN compound buffer layer is a polycrystalline layer. The nitride based semiconductor device according to claim 29, wherein the BN compound buffer layer is a layer in which an amorphous phase and a polycrystalline phase are mixed. 29. The nitride semiconductor device according to claim 28, wherein the BN compound buffer layer has a thickness of 100 to 600 GPa. 34. The nitride semiconductor device according to claim 33, wherein the BN compound buffer layer has a thickness of 200 to 300 GPa. The nitride-based semiconductor device according to claim 28, wherein the BN compound comprises at least one material selected from the group consisting of AlN, GaN, and InN and BN. The nitride-based semiconductor device according to claim 28, wherein the nitride-based semiconductor crystal layer is made of at least one of AlN, GaN, and InN materials. 29. The nitride semiconductor device of claim 28, wherein the intrinsic nitride semiconductor crystal layer is formed of at least two materials of AlN, GaN, and InN materials. 29. The nitride based semiconductor device as claimed in claim 28, wherein said active layer comprises at least one quantum well. The nitride based semiconductor device according to claim 38, wherein the quantum well is formed by changing a composition ratio of a material forming the intrinsic nitride based semiconductor crystal layer. The method of claim 38, wherein the active layer, A first layer forming an energy barrier; And And a second layer comprising at least one layer forming quantum wells having different energy levels according to the composition ratio. The method of claim 38, wherein the active layer, A first layer forming an energy barrier; And A nitride-based semiconductor device comprising a second layer consisting of at least one layer forming potentials having different energy levels in accordance with the composition ratio. The nitride based semiconductor device according to claim 28, wherein said substrate is a sapphire substrate. 43. The nitride based semiconductor device according to claim 42, wherein the first electrode is disposed on the n-type nitride-based crystal layer and the second electrode is disposed on the p-type nitride-based crystal layer. 29. The nitride based semiconductor device as claimed in claim 28, wherein said substrate is a SiC substrate. 45. The nitride-based semiconductor device as claimed in claim 44, wherein the first electrode is formed on the opposite side of the substrate in contact with the buffer layer and the second electrode is formed on the p-type nitride-based crystal layer. Providing a substrate; Epitaxially growing a BN compound at a first temperature on the substrate to form a buffer layer; And Forming an n-type nitride-based semiconductor crystal layer on the buffer layer at a second temperature higher than the first temperature; Forming an active layer by growing an intrinsic nitride semiconductor crystal on the n-type nitride semiconductor crystal; Forming a p-type nitride based semiconductor crystal layer on the active layer; And A method of manufacturing a nitride-based semiconductor device comprising the steps of forming a first electrode and a second electrode applying a voltage to the active layer. 47. The method of claim 46, wherein said first temperature is between 200 and 1000 degrees Celsius. 48. The method of claim 47, wherein said first temperature is between 500 and 600 degrees Celsius. 47. The method of claim 46, wherein said second temperature is at least 1000 &lt; 0 &gt; C. 47. The method of claim 46, wherein the nitride based semiconductor crystal layer is formed of at least a hinge material of AlN, GaN, InN materials. The method of claim 46, wherein the n-type nitride-based semiconductor crystal layer is formed, Epitaxially growing a nitride-based semiconductor on the buffer layer; And Doping the nitride based semiconductor with at least one dopant selected from the group consisting of C, Si, Ge, Se, S, Sn, Te, Be. The method of claim 46, wherein the p-type nitride-based semiconductor crystal layer is formed, Epitaxially growing a nitride semiconductor on the active layer; And Doping at least one dopant selected from the group consisting of Mg, Zn, Cd, Be, Ca, Sr, and Ba in the nitride-based semiconductor. A BN compound buffer layer formed on the substrate; A p-n junction active layer made of a nitride semiconductor formed on the buffer layer; And A nitride based semiconductor device comprising a first electrode and a second electrode for applying a voltage to the p-n junction active layer. Epitaxially growing a BN compound at a first temperature on the substrate to form a buffer layer; Forming a p-n junction active layer on the buffer layer at a second temperature higher than the first temperature; And Forming a first electrode and a second electrode applying a voltage to the active layer. A BN compound buffer layer formed on the substrate; A nitride semiconductor crystal layer formed on the buffer layer to form a light emitting region; And A nitride based semiconductor device comprising a first electrode and a second electrode for applying a voltage to the light emitting region.