JPH0936427A - Semiconductor device and fabrication thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer structure including a heterojunction based emission layer on a substrate of amorphous material by depositing a III-V compound semiconductor heterojunction comprising at least one kind of group III element including Al, Ga and In and a group III-V element containing at least nitrogen directly on the substrate of amorphous material. SOLUTION: A substrate 101 is subjected, on the surface thereof, to nitrogen plasma processing and an n-type AlN0.05 P0.95 layer is deposited directly thereon as a lower clad layer 103. Subsequently, C5 H5 In and NH3 are fed to the reaction system in order to deposit a p-type Ga0.4 In0.6 N layer as an emission layer 4. Finally, a heterojunction of the Ga0.4 In0.6 N emission layer 104 and the lower clad layer 103 of AlN0.05 P0.95 deposited directly on the surface of amorphous AlN substrate 101 is formed. The multilayer structure including a heterojunction based emission layer may be provided on a substrate of amorphous material by plasma processing of a gas containing nitrogen atoms on the surface of amorphous substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device made of a III-V group nitride semiconductor, and more particularly, to a material structure for increasing the emission intensity of a high-luminance short-wavelength visible light emitting diode (LED).

[0002]

2. Description of the Related Art III-V group nitride semiconductors such as gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), and mixed crystals thereof are environment-resistant electric field effects that operate even at relatively high temperatures. Type transistor (M. Asif Khan et al., Appl. Phys. L)
ett. , 65 (9) (1994), 1121. ) And L
It is used as a constituent material of semiconductor devices such as EDs.
Recently, a short-wavelength visible LED that emits visible light of a short wavelength such as blue or blue-green is formed by a laminated structure of III-V group nitride semiconductors such as GaN (for example, Katsuhide Sanbe, “Toyoda Gosei”). Technical Report ", Vol. 35, No. 4, (1993),
68).

FIG. 1 shows a structural example of a conventional LED chip composed of a III-V group nitride semiconductor. Each layer of the nitride semiconductor for forming the LED chip is an aluminum oxide (Al ₂ O ₃ ) single crystal (sapphire) substrate (20).
1) provided above (eg HM Manase)
Vit et al., J. Electrochem. Soc. , 1
18 (1971), 1864). Conventionally, it has been customary to use sapphire that is a single crystal as a substrate.

One of the reasons why sapphire, which is a single crystal, is used as a substrate is that sapphire transmits light of a short wavelength such as blue, so that light emission is not absorbed by the substrate and emission of light emission to the outside can be prevented. Because there is no. For LEDs,
In order to efficiently take out emitted light to the outside, it is customary to form the substrate from a material having a band gap higher than the energy corresponding to the emission wavelength.

Further, Ga, which is a constituent element of the conventional LED,
Each layer of N- or AlN or a III-V group nitride semiconductor, which is a mixed crystal thereof, is grown at a high temperature of about 1000 ° C. (M. Illegems, J. Cryst. Growth).
h, 13/14 (1972), 360. ). The metal-organic vapor phase epitaxy method (MO
It is called a CVD, MOVPE or OMVPE method. ) Or a halide as a raw material, such a vapor phase growth method (VPE method) or the like, such a high temperature is generally required. Therefore, it is necessary to use a heat-resistant material having a high melting point as a substrate, which does not deteriorate even at a high growth temperature. This is the reason why sapphire having a melting point of about 2040 ° C. higher than the growth temperature is used as the substrate.

As a substrate, in addition to this, single crystal gallium neodymium oxide (NdGaO ₃ ) (Fifth Autumn 1994)
Proceedings of the 5th JSAP Academic Lecture Meeting No. 1, Lecture No. 19p-MG-4, page 184) and similarly single crystal zinc oxide (ZnO). ZnO has a wide bandgap of 3.2 eV and transmits a short wavelength light without absorbing it, and has a lattice mismatch with a III-V group nitride semiconductor mixed crystal material such as AlGaInN. Because it is small III
It is disclosed as a substrate suitable for growing a group-V nitride semiconductor (Japanese Patent Publication No. 6-14564).

Single crystal materials are often used as conventional substrate materials for growing III-V nitride semiconductor layers. A single crystal such as sapphire is generally synthesized by using alumina powder or a polycrystalline sapphire lump as a raw material in an environment of high temperature and high pressure. After passing through the single crystal synthesizing step, it is cut into a desired shape. After that, the surface is precisely polished mechanically or chemically and used as a substrate. That is, many steps are required to obtain a single crystal material for a substrate, and thus the single crystal material is generally expensive.

A common reason for using a single crystal material as a substrate is to obtain a single crystal growth layer. That is, the growth layer epitaxially grown on the single crystal substrate becomes a single crystal. Since the single crystal growth layer is constructed from crystal planes having the same orientation, the optical or electrical characteristics are standardized, which is convenient for obtaining elements such as LEDs with uniform characteristics. Rather, the LED is required to be composed of a single crystal film.

However, it is known that a III-V group nitride semiconductor such as AlN can be crystallized even when grown on a material that is not a single crystal to obtain a single crystal film (Akazaki Isamu). , "Optics", Vol. 22, No. 11 (1993),
670). This means that a generally expensive single crystal substrate is not intentionally required to obtain a single crystal III-V nitride semiconductor film. That is, it suggests that a single crystal synthesizing step is not required for single crystallization, and an amorphous material having no crystallinity, which is generally cheaper than a single crystal material, can be used.

In the past, there is known an example in which Pyrex glass is used as an amorphous material and an AlN single layer film, which is a kind of III-V group nitride semiconductor, is formed on it. Yoichiro Uemura et al., "Applied Physics," Vol. 40, No. 5, (1971), page 572). Further, there is an example in which an AlN film is also provided on an electrode made of a conductive glass material (G.A.
WOLFF et al., Phys. Rev. , 114 (5) (1
959), 1262. ). However, in the conventional example, Al _x Ga is used as a material that emits visible light having a short wavelength.
_y In _z N (x, y and z represent composition ratios, x + y + z
= 1 and x> 0) are shown (Japanese Patent Publication 6-1
4564) An embodiment in which a heterojunction laminated structure for an LED having a mixed crystal layer or the like as a light emitting layer is directly provided on an amorphous material is not exemplified.

Even when the substrate is made of an amorphous material, if the material transmits light of a short wavelength, the emitted light can be efficiently extracted to the outside, and the emission intensity can be increased. By providing a metal film having a function of reflecting the light emitted from the substrate material on one main surface of the translucent material, it is possible to further improve the LED performance even if the crystallinity of the epitaxial film is not improved. Brightness can be easily achieved. Further, by forming the light emitting portion with a heterojunction, higher brightness can be achieved.

Amorphous material is made of quartz glass, a metal conductive film is formed on one main surface of the quartz glass, and then Al _w Ga _{1-w is used.}
A growth method for depositing N (0 ≦ w ≦ 1) or InN epitaxial film is also known. In this case, instead of directly depositing the III-V group nitride semiconductor layer on the quartz glass, once chromium (Cr), nickel (Ni), molybdenum is once formed on the surface of the quartz glass or the like which has been optically polished. (M
o), a metal such as gold (Au) or platinum (Pt) is deposited as a conductive film so as to have conductivity on the surface of quartz glass, and then a III-V group nitride semiconductor layer is grown. (Japanese Patent Publication No. 5-86646). However, in this case, the heterojunction is not included. In addition, this growth method forms a growth layer through a metal conductive film formed on the surface of quartz glass, so that high-quality Al _{x with} few nitrogen vacancies is formed.
It is intended to grow an epitaxial film of Ga _1-x N (0 ≦ x ≦ 1) or InN, and to improve the crystallinity of the epitaxial film, which is advantageous for producing a high-luminance light emitting device. Nothing else. That is, the conductive film provided on the surface of the quartz glass has not been provided in order to serve as a reflection film for reflecting the emitted light.

Furthermore, when growing a III-V group compound semiconductor layer through a metal conductive film provided on quartz glass according to a known example, a DC voltage is applied between the metal conductive film and a target material such as metal aluminum. And a buffer layer of Al _x Ga _1-x N (0 ≦ x ≦ 1) or InN is first deposited by high frequency sputtering in an atmosphere containing nitrogen gas. After that, ammonia (NH ₃ ) and II
Al _x Ga _1-x N (0 ≦ x ≦, which has the same composition as the buffer layer, is formed by metal organic chemical vapor deposition using a group I organic metal as a raw material.
1) or InN is epitaxially grown (Japanese Patent Publication No. 5-86646). According to this growth method, a high-quality Al _x Ga _1-x N (0 ≦ x ≦ 1) or InN epitaxial film with few nitrogen vacancies can be obtained, and thus a high-luminance light-emitting device can be manufactured. Although it is said that there is an advantage that it can be obtained, a complicated process is required to obtain an epitaxial film. For example, a sputtering method, a metal organic chemical vapor deposition method, and two types of growth methods are indispensable even in the epitaxial film growth step.
Since the growth process is complicated and complicated, the manufacturing cost of the light emitting device may increase.

For a general-purpose element such as an LED,
A complicated process is not preferable because it is required to be particularly inexpensive. In the case of a substrate made of an amorphous material, a single crystal film cannot be easily obtained even if the III-V group nitride semiconductor layer is grown directly on the substrate. There is a need for a simple surface treatment that can promote single crystallization of one major surface of the amorphous material on which the III-V nitride semiconductor layer is deposited, that is, the surface of the substrate, to promote single crystallization of the growth layer deposited thereon.

In order to increase the brightness of the light emitting device, not only the quality of the epitaxially grown film is improved but also the brightness may be easily achieved by using a structure having a function of reflecting emitted light. For example, there is known a conventional method of arranging a reflecting mirror at an appropriate position to promote emission of emitted light to the outside. FIG. 2 shows a configuration example of a conventional LED provided with such a reflecting mirror. Conventionally, the reflector (111) that brings about high brightness is a stem (pedestal device) for fixing the LED chip (112).
It is provided in a part of (113). In the past,
Thus, a stem having a special and complicated structure was required to reflect the emitted light. For example, if the substrate is translucent,
The structure can be simplified by applying a member for obtaining a reflecting action to a part of the substrate by utilizing this. However, up to now, there is no known high-luminance LED which has a member for the purpose of obtaining the action of reflecting the light emission for achieving such high-luminance and has a simplified structure.

Unlike the known example shown in FIG. 2, for example, one main surface of the transparent quartz glass substrate opposite to the surface on which the III-V nitride semiconductor layer is deposited, that is, the back surface side of the substrate. If a metal reflective film is provided on the LED, the intensity of the emitted light reflected to the outside can be increased. If processing is performed to increase the surface area of the back surface of the substrate on which the reflective film is provided, the reflection intensity further increases as the surface area of the reflective film having a reflecting action increases.
One of the processing methods for increasing the surface area is a method of forming uneven grooves on the surface. In fact, a method for growing a hexagonal crystal layer similar to the substrate on a hexagonal substrate having a (0001) plane with a groove formed on the surface side has also been disclosed (JP-A-5-36602). However, conventionally, the groove is formed on the surface side of the hexagonal crystal substrate, and the groove is provided for the purpose of improving the surface state of a hexagonal crystal film having the same crystal system as the substrate. Grooves are not provided to expand the surface area of the surface.

[0017]

In order to supply an inexpensive LED, it is advantageous to use an amorphous material as the substrate. For that purpose, surface treatment is required so that a single crystal film is easily provided on the surface of the amorphous substrate. Further, a member having a function of reflecting emitted light without the need for a special stem is provided in contact with the substrate, increasing the reflection intensity of the emitted light from the LED and, as a result, increasing the emitted light intensity from the LED. It would be even more convenient if there were a simple configuration provided. However, until now, for a short-wavelength visible LED, a laminated structure including a hetero-junction light emitting layer which is a pn junction required for obtaining a high-brightness LED with low power consumption is provided on an amorphous material substrate. The examples given are not known. Alternatively, there is no known example in which a structure for increasing the reflection intensity of emitted light is provided on an amorphous substrate. In view of such a background, it is an object of the present invention to solve these conventional problems with new ideas in order to supply an inexpensive and high-brightness LED.

[0018]

That is, according to the present invention, a substrate made of an amorphous material is exposed to a plasma atmosphere of a gas containing nitrogen atoms and surface-treated, and then at least one of Group III of Al, Ga or In is added. The present invention is characterized in that a laminated structure including a heterojunction of a III-V group nitride semiconductor containing at least nitrogen as an element and a Group V element is directly deposited on the surface of the amorphous material substrate. Another feature of the present invention is to provide a semiconductor device in which a metal film is formed on the back surface of an opposite substrate opposite to the surface of an amorphous substrate on which a III-V nitride semiconductor is directly deposited. The metal coating also provides a semiconductor device provided on the back surface of an amorphous substrate having a plurality of grooves.

In the present invention, a material that is an inexpensive amorphous material and has a light-transmitting property as compared with a single crystal material is used as the substrate. Amorphous materials are crystallographically amorphous (amo
or a material having a micellar structure with partially crystallized regions. Examples of the amorphous and translucent material include amorphous glass, crystallized glass, and quartz glass. In addition, a ceramic material such as AlN having a light-transmitting property also corresponds to this. The film forming temperature of GaN, AlN, etc. is generally about 1000.
Since the temperature is as high as ° C, a substrate material that can withstand practical use without softening or melting even at such a high temperature is desirable. From this point, a transparent ceramic material such as quartz glass or AlN is more convenient than an amorphous glass material that softens at a relatively low temperature. Quartz glass material is particularly convenient because it has excellent transparency to short-wavelength light in the ultraviolet region.

In the present invention, for example, a plasma containing a gas containing a molecule having nitrogen atoms as at least one of the constituent atoms is formed on one main surface for depositing a growth layer of an amorphous substrate material such as a quartz glass substrate. Surface treatment is performed by exposing to the atmosphere. By this plasma treatment, nitrogen atoms can be made to exist on the surface of the amorphous substrate. Nitrogen atoms existing near the surface of the substrate act as nitrogen sites from the viewpoint of the crystal growth mechanism when the III-V group nitride semiconductor layer grows on the surface. This has the effect of facilitating the growth of the single crystal film.

From the results of earnest studies by the present inventors, nitrogen gas was used as a molecule having a nitrogen atom as at least one of the constituent atoms, and a microwave having a frequency of 2.45 GHz was generated in a vacuum environment of 80 Torr. When nitrogen gas is excited and the surface of the quartz glass substrate is treated for 10 minutes,
For example, the plasma surface treatment is sufficient to obtain a GaN film whose surface layer portion is single-crystallized at a growth temperature of 600 ° C. by the MOCVD method under normal pressure.

The plasma for treating the surface of the substrate is not limited to being generated from nitrogen gas, but includes, for example, ammonia (NH ₃ ), aliphatic, alicyclic or aromatic amines and nitrogen atom as at least one ring constituent element. Pyrrole
Role) and the like, a compound containing an amine group that is a substituent containing nitrogen or a substituent containing nitrogen, a compound containing an azo group (-N = N-), and the like may be used.

As a method of treating the surface of the substrate, there is a method of implanting nitrogen ions into the surface of the substrate in addition to the method of utilizing plasma. However, as a result of repeated studies by the present inventors, in order to obtain the same effect on the single crystallization as the plasma treatment, an acceleration energy exceeding about 300 KeV is required for nitrogen ions, and 10 ¹⁴ to 10
^A huge dose of ¹⁵ cm ^-2 or more
Need quantity. If the dose amount is increased, the time required to complete the implantation is increased, so that it cannot be a simple surface treatment method.

Ga is an example of a III-V nitride semiconductor containing nitrogen and at least one Group III element of Al, Ga or In grown on the amorphous substrate according to the present invention.
N, AlN, InN, AlGaN, GaInN, AlI
Examples include nN and AlGaInN.

Further, as a Group V element added to N, arsenic (element symbol: As) and phosphorus (element symbol: P) are included II
I-V group nitride semiconductors also correspond to the present invention. This includes
GaNAs, GaNP, AlNAs, AlNP, InN
As, InNP, AlGaNAs, AlGaNP, Ga
InNAs, GaInNP, AlInNAs, AlIn
NP, AlGaInNAs, AlGaInNP, GaN
PAs, AlNPAs, InNPAs, AlGaInN
There are PAs and the like.

In the present invention, the heterojunction laminated structure formed by combining these III-V nitride semiconductor layers is subjected to the above plasma treatment, and is a substrate made of an amorphous material that transmits light of a short wavelength. Laminate directly on the surface of. Unlike the conventional example, a single crystal film can be obtained by directly depositing a laminated structure on a substrate. The single crystal film can be obtained by subjecting the substrate surface to the above plasma treatment. From this, it is possible to
There is an advantage that the complicated growth process required for growing the lGaN or InN epitaxial film can be omitted.

The growth method for directly depositing the III-V group nitride semiconductor layer on the amorphous substrate is not particularly limited. The conventional MOCVD growth method or VPE growth method can be used. Further, a growth method such as a molecular beam epitaxial (MBE) method or a chemical beam epitaxial (CBE) method can also be used. MB
Depending on the form of the raw material used in the E method, a gas source (G
Although there are methods such as S) MBE and organic metal (MO) MBE, any method can be used. There is no limitation on the Ga, Al or In or N raw material for growing the III-V group nitride semiconductor layer. The present invention is not intended to increase the emission intensity by improving the film quality by reducing the nitrogen vacancy defects of the III-V group nitride semiconductor layer provided on the amorphous substrate. Unlike the conventional example, a plurality of growth methods are not required, and therefore, in obtaining a laminated structure for manufacturing a semiconductor device, simplification of steps is achieved.

The heterojunction is a layer having a different constituent element from the examples of the III-V group nitride semiconductors described above, or a layer having a different constituent element composition even if the constituent elements are the same, that is, a structure. It can be formed by joining heterogeneous semiconductors having different elements or compositions to each other. For example GaInN and G
The heterojunction with aInNP is an example of a heterojunction composed of semiconductor layers having different constituent elements. V and w that represent the composition ratio
The junction between InN _1-v As _v and InN _1-w As _w having different values of is an example of a heterojunction having different composition ratios.

If the number of layers forming the heterojunction is 2, there is one junction interface (heterojunction interface). This is called a single heterojunction. If the heterojunction is composed of three layers, the number of heterojunction interfaces is 2, which is called a double heterojunction. If the number of heterojunction interfaces is three, it may be called a triple heterojunction, but it is generally called a multiple heterojunction. By including these single, double heterojunctions and multiple heterojunctions in the laminated structure, the laminated structure having the heterojunction referred to in the present invention is formed.

In the present invention, a metal coating for reflecting emitted light is provided on one main surface of a light-transmissive amorphous substrate. The metal film is provided on the back surface of the substrate, not on the one main surface on which the III-V nitride semiconductor layer is deposited, that is, on the front surface of the substrate. This reflective coating is made of gold (elemental symbol: Au), aluminum (elemental symbol: Al), chromium (elemental symbol: Cr).
It can be formed by depositing a metal such as the above on the back surface side of the substrate by a vacuum deposition method. Considering the high reflectance for light emission in the short wavelength region and the economical efficiency for obtaining an inexpensive LED, A
l is most suitable. The metal coating to be provided may be a film made of a single substance, for example, a film made of only Al, or, for example, Al
It may be a film having a two-layer structure in which the respective layers of titanium and titanium (elemental symbol: Ti) are stacked. When a single layer or several layers of metal coating are provided, the thickness of each layer is not particularly limited, but it is from 1 to 10
If the thickness is extremely thin, such as about nm, the probability of light transmission increases, which is not preferable. A film thickness of 100 nm to 5000 nm is suitable for practical use. For example, an Al thin film having a thickness designed to enhance the reflectance of light of a certain wavelength and T
A so-called optical interference film structure in which i thin films are laminated in multiple layers may be used. By providing a metal coating on one main surface of the substrate material to provide a reflecting action, it is not necessary to separately provide a reflecting mirror inside the stem as in the conventional example, and the light emission of the LED can be reflected to the outside with a simple structure. To increase the emission intensity from. Of course, it is acceptable to mount an element having a reflection metal coating on the back surface side of the substrate according to the present invention on a stem having a reflection mirror for light emission as in the prior art, in that the emission intensity is increased.

The intensity of the reflected light increases as the area that functions as the reflecting surface increases. In the present invention, in the case of providing a metal coating for reflection on the back surface side of the substrate because it has conductivity, a groove is formed on the back surface side of the substrate to increase the surface area of the substrate and increase the reflection area.

The groove can be formed on the back surface of the substrate by an etching method or the like using a known patterning technique by photolithography. For example, the back surface of the amorphous conductive glass material is once coated with a normal photoresist material. After that, it is exposed to light to expose the photoresist material and is patterned into a desired groove shape. The photoresist material corresponding to the groove portion is removed with a resist stripping solution or the like to expose the surface of the substrate material. Only the exposed area is etched to remove a part of the substrate material. By peeling off the finally remaining photoresist material, a substrate material having grooves formed therein can be obtained. The groove can also be formed by mechanical cutting using a machine tool such as a lathe.

In order to further increase the surface area, it is advisable to form the grooves in a grid pattern. Although the shape of the cross section of the groove is not limited, the light emission can be reflected in almost all directions if the cross section is semicircular and a metal reflective coating is provided on the cross section. Also, when etching and removing the substrate material to form the grid-shaped grooves on the back surface of the substrate, selecting an etching agent or etching condition that gives a triangular cross-section results in piercing in a triangular pyramid shape and increasing the surface area. Bring There is no particular limitation on the number of grooves provided on the substrate. However, since a general LED chip has a rectangular shape with one side of 300 μm to 450 μm, it is preferable that at least several grooves are arranged in the shape of this chip.

After forming the groove as described above, a metal film serving as a reflection film having a function of reflecting emitted light may be formed.
As a method for forming the metal coating, a vacuum vapor deposition method or a coating method can be used. In the coating method, for example, a liquid substance containing a desired metal powder or compound is coated on the surface of the substrate on which the groove is formed, and then heated and solidified to form a metal coating. In addition, since the coating method uses a liquid substance, it is convenient to fill a step such as a groove, and as a result, a metal film having a flat surface can be easily obtained. It may be difficult to obtain a film having a film thickness exceeding several tens of μm by a physical deposition method such as a vacuum evaporation method or a sputtering method. In such a case, once coat the side surface of the groove or the wall surface so as to entirely cover the groove, and then apply plating (plating).
There is also a method of increasing the film thickness of the coating by a method or the like to fill the groove. However, it is not absolutely necessary to completely fill the groove with the material forming the metal film and to flatten the back surface of the substrate, and the shape of the groove may be intentionally left. If there is a groove on the back side of the substrate that is unevenly filled with the material that constitutes the metal film and that has a step on the unevenness, the contact area of the adhesive fixing agent for fixing the element to the stem material increases. This is because the stubborn fixation can be achieved.

Since the surface area of the substrate tends to increase with the depth of the groove provided in the substrate, the deeper the groove, the more the reflection intensity of light emission increases, but at the same time, the substrate has a thin layer. Therefore, the mechanical strength of the substrate is impaired. Therefore, it is preferable that the depth of the groove provided in the substrate is about 80% at the deepest with respect to the thickness of the substrate. For example, for a substrate with a thickness of 300 μm, the maximum groove depth is 2
It is better to stop at 40 μm.

[0036]

The plasma treatment using a gas containing nitrogen atoms on the surface of the amorphous substrate results in the easy formation of a single crystal III-V group nitride semiconductor layer on the surface of the amorphous substrate. The complexity of the epitaxial film growth process is avoided. The metal coating formed on the back surface of the substrate increases reflection of emitted light to the outside. The groove provided on the back surface of the substrate expands the surface area of the metal film that reflects light emission, and further increases the reflection intensity.

[0037]

【Example】

(Example 1) The present invention will be described in detail based on an example in which a laminated structure for semiconductor device use according to the present invention is obtained by MOCVD. FIG. 3 is a schematic sectional view of a laminated structure according to this example. Insulating amorphous AlN was used for the substrate (101). This AlN had translucency. Board (10
The thickness of 1) was about 300 μm.

The substrate (101) was placed in the vacuum chamber of a commercially available dry etching apparatus, and then the chamber was evacuated until the degree of vacuum reached about 2 × 10 ⁻⁵ 100 Torr. When the ultimate vacuum was almost stabilized, nitrogen gas with a purity of 5N was introduced into the chamber to adjust the pressure in the chamber to about 100 Torr. After that, a high frequency bias having a frequency of 13.56 MHz was applied to the parallel plane electrodes in the chamber to generate nitrogen plasma. The above substrate (1
01) was placed on the grounded side electrode of the parallel plane electrodes arranged in parallel. The surface of the substrate (101) was treated with nitrogen plasma by the nitrogen plasma generated between the parallel plane electrodes.

AlN whose surface is treated with nitrogen plasma
An n-type AlN _0.05 P _0.95 layer was directly deposited on the substrate (101) as a lower cladding layer (103). The film thickness was about 0.1 μm. Carrier concentration is about 1 × 10 ¹⁸ cm
^-3 . This layer (103) is trimethylgallium ((CH ₃ ) ₃ Ga) / trimethylaluminum ((C
H _{3) 3} Al) / phosphine (PH ₃₎ / hydrogen (H ₂₎
It was grown at a temperature of 750 ° C. by an atmospheric pressure MOCVD method using a reaction system. Next, the supply of the mixed gas of PH ₃ and H ₂ diluted with high-purity hydrogen so that the volume concentration of PH ₃ becomes 10% and (CH ₃ ) ₃ Ga to the MOCVD reaction system is stopped and replaced. Cyclopentadienylindium (C ₅ H
₅ In) and ammonia (NH ₃ ) are supplied to the reaction system, and p
A Ga _0.4 In _0.6 N layer of the form was deposited as the light emitting layer (104). The flow rates of C ₅ H ₅ In and NH ₃ added to the reaction system maintained at a temperature of 70 ° C. were set to 170 cc / min and 1 lcc / min, respectively. The film thickness was about 0.1 μm. The carrier concentration was about 1 × 10 ¹⁷ cm ⁻³ .

As a result, Al directly deposited on the surface of the substrate (101) made of amorphous AlN surface-treated by nitrogen plasma without a metal coating as in the conventional case.
Ga and the lower clad layer (103) consisting of N _0.05 P _0.95
A heterojunction was formed with the light emitting layer (104) made of _0.4 In _0.6 N. Substrates treated with nitrogen plasma (1
01) Growth layers ((103) and (1
In the case of (04)), it was found from the diffraction pattern by the usual X-ray diffraction method that they were all single-crystallized films.

Next, p-type GaN is formed on the light emitting layer (104).
_An upper clad layer (105) made of _0.98 As _0.02 was laminated. The film thickness is 0.3 μm and the carrier concentration is about 2 × 1.
It was set to 0 ¹⁸ cm ^-3 . As a source of hydrogen, diluted arsine (volume concentration 10%)-high purity hydrogen (volume concentration 90
%) Mixed gas was used. Ga source (CH ₃ ) ₃
Ga) was kept at a temperature of 0 ° C. by a thermostat and supplied to the reaction system at a flow rate of 30 cc / min. Arsine (AsH ₃ )
Was 35 cc / min.

With the above structure, the heterojunction between the AlN _0.05 P _0.95 layer (103) and the Ga _0.4 In _0.6 N layer (104), the Ga _0.4 In _0.6 N layer (104) and the GaN _0.98 layer.
As _{0. 02} (105) and amorphous AlN stacked structure of LED applications having a double hetero-junction comprising a heterojunction
It was constructed by depositing directly on the substrate (101). Short wavelength L using this double heterojunction laminated structure
ED was created. This LED was observed to emit blue-greenish blue light, and the central emission wavelength was about 4720 angstroms (Å). In comparison with the conventional example regarding the emission intensity, the LED according to the present example shows that the LED according to the conventional LE
It was recognized that it gave strength comparable to D. Here, a conventional LED is a Ga having an In composition ratio of about 0.2 to which impurities such as cadmium (Cd) and zinc (Zn) are added.
It refers to an LED that emits deep green light using InN as a light emitting layer. On the other hand, the full width at half maximum of the emission spectrum is about 340 angstroms (Å), which is about 1/2 of that of the conventional LED described above (the full width at half maximum of the emission spectrum of the conventional LED is about 700 angstroms). There is a remarkable improvement.
One of the reasons why the full width at half maximum is reduced is that the present invention uses a substrate whose surface is treated with nitrogen plasma, so that nitrogen vacancies in the heterojunction layer deposited thereon are used.
It was determined that the concentration was reduced.

Example 2 Amorphous quartz glass having a total content of alkali metals such as sodium, potassium and lithium of 5 ppm by weight or less was used as the substrate (101).
FIG. 4 is a schematic plan view of the structure of the LED according to this embodiment.
FIG. 5 shows a schematic sectional view taken along the broken line AA ′ in FIG. The surface of the quartz glass substrate (101) was subjected to surface treatment with nitrogen plasma according to the method described in Example 1. The conditions such as the degree of vacuum during plasma processing were almost the same as in Example 1, but the power during plasma generation was increased to 210 W.
The amorphous AlN used as the substrate in Example 1 originally contains a nitrogen atom as a constituent element, but quartz glass contains silicon dioxide (SiO ₂ ) as a main component and does not contain a nitrogen atom as a constituent element. The plasma power was increased in order to efficiently form nitrogen sites on the surface of the quartz glass substrate.

A quartz glass substrate (1
N) directly on the surface of No. 01) by the above atmospheric pressure MOCVD method.
Shaped GaN layer was deposited as the lower cladding layer (103). The film thickness was about 0.1 μm. Carrier concentration is about 1x
It was 10 ¹⁸ cm ^-3 . Next, p-type Ga _0.88 In _0.12 N
The layer was deposited as a light emitting layer (104). Light-emitting layer (10
The film thickness of 4) is 0.25 μm, and the carrier concentration is 1 × 1.
It was set to 0 ¹⁷ cm ^-3 . A p-type Ga is formed on the light emitting layer (104).
N was formed as the upper cladding layer (105). The film thickness was 0.05 μm, and the carrier concentration was 2 × 10 ¹⁸ cm ⁻³ . The crystal structure ((103) to (105)) directly deposited on these amorphous substrates constitutes a laminated structure having a double heterojunction. Reflection electron diffraction (RHEE
In the analysis on the crystal morphology in the vicinity of the surface by D), the quartz glass substrate (10
The surface layer of the GaN lower clad layer (103), which is the first layer deposited on the surface of 1), was crystallized.

An anode electrode (107) made of Al was formed on the upper clad layer (105) corresponding to the outermost layer of the laminated structure by using a known photolithography technique. The facing cathode electrode (108) was formed on the lower clad layer (103) exposed by mesa etching the peripheral portions of the upper clad layer (105) and the light emitting layer (104).

On the back side of the amorphous quartz substrate (101), Al for reflecting the light emitted from the light emitting layer (104) is formed.
A metal coating (109) consisting of was deposited by vacuum evaporation. The thickness of the metal coating (109) was about 0.5 μm.
In the present embodiment, the materials forming the metal film for reflection of light emission and the electrode are the same, but the material composition for forming the electrode and the metal film for reflection is different. But there is no problem.

With the above-mentioned structure, the amorphous structure has a laminated structure composed of a III-V group nitride semiconductor layer having a double heterojunction directly deposited on the surface of a plasma-treated amorphous substrate, and has an amorphous structure. A semiconductor device (LED) having a metal coating provided on the back surface side of the substrate for the purpose of reflecting emitted light was constructed. The luminescence was violetish blue and its center wavelength was about 3850 angstroms (Å). This light emission was observed by applying a DC voltage of several volts (V) to the positive and negative electrodes, and the forward current was 20 mA.
The emission intensity of the non-molded product chip reached about 62 millicandelas (mcd). Since the obtained emission intensity is about 2.2 times as large as that of the LED having no metal coating composed of the same double hetero laminated structure,
It was clearly shown that a metallic coating on the back side of the amorphous substrate material leads to an increase in emission intensity. This result shows that even with an inexpensive amorphous transparent material as compared with an optically transparent single crystal material, it is possible to obtain light emission with increased intensity by providing a metal film that reflects light emission. There is.

(Example 3) Amorphous fused silica glass was used as the substrate (101), and a laminated structure similar to that of Example 2 was directly provided on the surface of the substrate subjected to the nitrogen plasma treatment of Example 2. FIG. 6 shows a schematic sectional view of an LED according to this example. Each layer constituting the laminated structure was formed by a MOCVD method under normal pressure at a growth temperature of 700 ° C. The substrate (101) used had a circular shape with a diameter of 50 mm and a thickness of 15
It was 0 μm.

Before the laminated structure is obtained, 60 linear grooves (110) having an opening width of 30 μm are formed on the back surface of the substrate (101).
It was provided periodically at intervals of μm. That is, the distance between the centers of the grooves was set to 60 μm. The opening width of the groove and the distance between the centers of the grooves may be set appropriately, but in the present embodiment, the groove (110) and the cutting groove for dicing for obtaining a square chip having a side of 360 μm are shared. Therefore, this value was used. This chip size is just an example. The cross-sectional shape of the groove (110) was semicircular, and the depth of the groove (110) was 20 μm. The depth of the groove (110) was more than 13% of the thickness of the substrate (101). These grooves (110)
Was formed by cutting using a lathe.

The same laminated structure as in Example 2 was directly deposited on the amorphous quartz substrate (101) in which the grooves (110) were periodically formed on the back surface. Electrodes ((107) and (10
8)) was also made of Al as described in Example 2 above.

Laminated structure and electrodes ((107) and (10)
8)) is formed, and then A is entirely formed on the back surface of the substrate (101).
1 was vacuum-deposited to form a metal coating (109) made of Al for reflecting light emission. Vacuum deposited metal film (10
The thickness of 9) was about 7 μm. In this embodiment, the reflective metal film is provided after the process of directly forming a laminated structure on the amorphous substrate (101). This is because each layer constituting the laminated structure is grown at a temperature higher than 660 ° C., which is the melting point of Al of the metal film (109) material, as described above, and thus is formed on the back surface of the amorphous substrate (101) in advance. If such a metal having a relatively low melting point is deposited, the metal film is dissolved during growth and is separated from the wall surface of the groove (110) to reduce the surface area exhibiting the reflection action, that is, the reflection efficiency is reduced. Is.

It was observed that the LED thus obtained, which was provided with a metal coating for reflection on the substrate, had an increased emission intensity as compared with the LED of the conventional example. Furthermore, by providing a metal coating for light emission reflection on the surface having the increased surface area described in Example 3, further increase in the reflection intensity can be achieved as compared with the case where the reflection metal is simply attached to the substrate. It was If a specific example is shown, there is no difference in the center wavelengths of the light emission of the LEDs obtained in Examples 2 and 3, but the emission intensity is further 1.3% compared to the case of Example 2 described above. It doubled to about 80 millicandelas (mcd).

[0053]

The plasma surface treatment with a gas containing nitrogen has the effect of promoting single crystallization of a growth layer deposited directly on an amorphous substrate. Further, by providing a metal coating on the back surface side of the substrate, there is an effect of increasing the light emission intensity as an element of the LED. Increasing the surface area of the back surface of the substrate on which the metal coating for reflection is provided has the effect of further increasing the reflection intensity of emitted light to the outside.

Although the LED has been described as an example of the semiconductor device according to the present invention in the present embodiment, the effect of the present invention, in particular, the single crystallization is promoted by performing the plasma treatment on the surface of the amorphous material substrate. Other semiconductor devices,
For example, it is also effective for obtaining a laminated structure for so-called electronic devices such as Hall elements and field effect transistors having a heterojunction such as GaN / AlGaN.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a conventional blue LED chip.

FIG. 2 is a schematic sectional view of an LED fixed to a pedestal provided with a reflecting mirror.

FIG. 3 is a schematic sectional view of an example of a laminated structure for LED application according to Example 1 of the present invention.

FIG. 4 is a schematic plan view of an LED according to Example 2 of the present invention.

5 is a schematic cross-sectional view taken along the broken line AA ′ shown in FIG.

FIG. 6 is a schematic sectional view of an LED according to Example 3 of the present invention.

[Explanation of symbols]

 (101) Substrate (102) Buffer layer (103) Lower clad layer (104) Light emitting layer (105) Upper clad layer (106) Contact layer (107) Anode electrode (108) Cathode electrode (109) Metal coating (110) Groove (111) Reflecting mirror (112) Chip (113) Stem (114) Envelope resin (115) Connection (201) Sapphire substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyuki Awaihara 1505 Shimokagemori, Chichibu City, Saitama Prefecture Showa Denko Co., Ltd. Chichibu Laboratory

Claims (4)

[Claims] 1. A III-V nitride semiconductor heterojunction comprising at least one Group III element of Al, Ga or In and a Group V element containing at least nitrogen.
A semiconductor device for a light emitting element, which is composed of a laminated structure directly deposited on the surface of an amorphous material substrate. 2. The semiconductor device for a light emitting device according to claim 1, wherein a metal film is formed on the back surface of the substrate opposite to the front surface of the substrate on which the III-V group nitride semiconductor heterojunction is deposited. . 3. The semiconductor device for a light emitting device according to claim 2, wherein a plurality of grooves are provided on the back surface of the amorphous material substrate, and a metal film is further provided on the grooves. 4. An amorphous material substrate is exposed to a plasma atmosphere containing nitrogen atoms, and then at least one group III element of Al, Ga or In and a group V element containing at least nitrogen are formed on the surface of the substrate. A method for manufacturing a semiconductor device for a light emitting device, which comprises depositing a III-V group nitride semiconductor heterojunction composed of a group element.