JP3267983B2 - Semiconductor light emitting device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device used for environment-resistant devices, visible light emitting diodes, etc., and more particularly to a semiconductor light emitting device using silicon carbide (SiC) having a hexagonal crystal structure and its manufacture. About the method.

[0002]

2. Description of the Related Art SiC crystals have a wide forbidden band width (2.
2 to 3, 3 eV), and a pn junction or a MOS structure can be easily formed. For this reason, studies have been made on blue and purple visible light emitting diodes using SiC crystals.

[0003] SiC having a hexagonal crystal structure can emit light in the blue and purple regions. Most stable 6H
Blue light-emitting diodes have been made to date using type crystals. However, a light emitting diode using a SiC crystal has a low luminous intensity and cannot be used along with red and green light emitting diodes to form a full color display.

[0004] The main reason for this is that the SiC crystal has an indirect transition type band structure as shown in FIG. 4 and the radiative transition is unlikely to occur. Also, the impurity level used to obtain blue light emission is about 2
As shallow as 20 eV, it cannot capture carriers sufficiently. For this reason, it is easily affected by non-radiative recombination processes such as defects in the crystal, and many defects exist in the crystal because the growth method of the SiC crystal has not been established yet, which is a factor that lowers the luminous intensity. Was.

[0005]

As described above, conventionally, Si
In an element that emits light in a shorter wavelength region than blue using a C crystal, a sufficient emission intensity cannot be obtained due to various factors.

The present invention has been made in view of such circumstances, and it is an object of the present invention to emit light having a wavelength shorter than that of blue light using an SiC crystal and to obtain a sufficient light emission intensity. It is an object of the present invention to provide a semiconductor light-emitting device capable of obtaining the same and a method for manufacturing the same.

[0007]

The gist of the present invention is SiC.
An object of the present invention is to increase the luminous efficiency by making the band structure of a light emitting layer using a crystal a direct transition type.

That is, according to the present invention, silicon carbide (S ) is deposited on a substrate crystal made of silicon carbide (SiC) having a hexagonal crystal structure.
In a semiconductor light emitting device in which a light emitting layer having a superlattice structure including iC) is formed, the main surface of the substrate crystal is set to (11-20) or (1-20).
−100), and the superlattice structure of the light emitting layer is set to an even multiple of the lattice spacing of the substrate crystal. Although the negative direction of the crystal orientation is generally indicated by inverse, it is indicated by-symbol in this specification.

The present invention also provides a method for manufacturing a semiconductor light emitting device, comprising the steps of: forming a silicon carbide (S) having a hexagonal crystal structure;
The principal surface of the substrate crystal of the first conductivity type made of iC) is (11-2)
After cutting out in the (0) or (1-100) plane orientation, a first conductivity type light emitting layer having a superlattice structure containing silicon carbide (SiC) is grown and formed on the main surface of the substrate crystal, and this light emission is obtained. The superlattice structure of the layer is set to an even multiple of the lattice spacing of the substrate crystal, and then silicon carbide (SiC) is included on the light emitting layer.
It is characterized by growing a semiconductor layer of the non-second conductivity type.

In a preferred embodiment of the present invention, when the light emitting layer is grown, layers to be doped with impurities and layers not to be doped are alternately grown, or different materials are laminated to form a strained superlattice structure. It is characterized by forming.

[0011]

As described above, a normal SiC crystal has an indirect transition type band structure as shown in FIG. The minimum of the conduction band is located at the point M (11-20) or the point K (1-100). Here, if a structure having a double period in the [11-20] direction or the [1-100] direction is achieved, the first brilliant zone is halved. As a result, the bottom of the conduction band located at the point M or the point K moves to the point Γ. For this reason, the top of the valence band and the bottom of the conduction band are at the same position, and dislocations are made in a direct transition type.

According to the present invention, the plane orientation of a substrate crystal made of silicon carbide (SiC) having a hexagonal crystal structure is set to (1).
(1-20) or (1-100), on which a superlattice structure light emitting layer having an even multiple of the lattice spacing of a normal hexagonal crystal is grown. The band structure changes directly to a transition type. As a result, the radiation recombination process is greatly increased, and the luminous efficiency can be increased.

In the (11-20) direction or (1-100)
By doping impurities at even intervals of the lattice constant in the direction, a periodicity twice as large as that of the crystal lattice appears in the light emitting layer. As a result, as described above, the light emitting layer can be easily transposed to a direct transition type.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 shows a first embodiment of the present invention.
It is sectional drawing which shows schematic structure of C: Al, N light emitting diode. 11 in the figure is 6H type S cut out to (11-20) plane.
An n-type light emitting layer 12 having a superlattice structure having a periodic structure twice as long as the lattice spacing of the substrate crystal is formed on an n-type substrate made of an iC crystal. On the light emitting layer 12, a circular p-type layer 13 is selectively formed. A p-side electrode 14 is formed on the p-type layer 13, and an n-side electrode 15 is formed below the n-type substrate 11. In order to manufacture this light emitting diode, metal organic chemical vapor deposition (MOCVD) is used as follows.

First, the 6H SiC crystal substrate 11 cut into the (11-20) plane is placed in an MOCVD apparatus and subjected to surface treatment at a high temperature. Next, the substrate temperature was increased to the growth temperature (1500).
° C), silane which is a raw material of silicon (Si) diluted with a carrier gas and propane gas which is a raw material of carbon (C) are alternately introduced. During the switching, hydrogen chloride gas is introduced to remove excess Si and C.

By doing so, it is possible to grow one atom at a time. When this growth is performed, a layer in which impurities are added alternately and a layer in which impurities are not added are alternately grown for each layer of the SiC layer, thereby forming an n-type light emitting layer 12 having a super lattice structure. As impurities, nitrogen (N) is introduced for the determination of conductivity type, and aluminum (Al) is introduced as an emission center so as not to exceed the amount of nitrogen.

Here, in the superlattice structure of the light emitting layer 12, the period is the same as the point M in the band structure shown in FIG.
It is set to twice the interval (lattice constant) between points. The addition amount of Al and N as impurities is 10 ¹³ cm ⁻² to 10 ¹⁴ cm ^−2.
Range.

According to the above method, the n-type light emitting layer 12 is
After the growth, the p-type layer 13 is grown on the light emitting layer 12 to a thickness of about 500 nm using Al as a conductivity type determining impurity. p
In growing the mold layer 13, a source gas and an impurity gas were simultaneously flowed. Thereafter, Ti and Al are formed on the p-type layer 13 as p-side electrodes.
And an Ni electrode 15 as an n-side electrode was attached to the substrate 11 to form ohmic electrodes.

In the light emitting diode manufactured as described above, the band structure of the light emitting layer 12 is directly transposed to a transition type, so that the radiation transition easily occurs and the luminous efficiency can be increased. According to the experiments performed by the present inventors, as shown in FIG. 2, the device of the present embodiment was able to achieve an emission intensity of one digit or more than the conventional device. Further, in this embodiment, a blue or purple light-emitting element having a high luminous intensity, which has been conventionally difficult, is realized. This makes it possible to manufacture a full-color display light-emitting element by combining with a red or green light-emitting diode.

FIG. 3 is a sectional view showing a schematic structure of a light emitting diode according to a second embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, a 2H-type n-type SiC buffer layer 21 is formed on a 6H-type n-type SiC crystal substrate 11, and a 6H or 4H-type n-type light-emitting layer 22 and 2H-type
The p-type layer 23 is formed by growth. Here, the buffer layer 21 is obtained by growing AlC and N by mixing SiC by MOCVD. The light emitting layer 22
Grows at a normal growth temperature of 1450 to 1600 ° C., and the p-type layer 23 grows at a lower growth temperature of 1200 to 1300 ° C.
I just need to grow.

In such an embodiment, the light-emitting layer 22 is 6H
Since the substrate 21 and the p-type layer 23 are of the mold or 4H type and the substrate 21 and the p-type layer 23 are of the 2H type, the band gap of the light emitting layer 22 is sufficiently smaller than that of the substrate 21 and the p-type layer 23, and the emission intensity can be further increased. This is because the band gap of the 2H type is larger than that of the 6H type.

The present invention is not limited to the above embodiment. In the embodiment, the plane orientation of the SiC substrate is set to (1).
(1-20), but the plane orientation of (1-100) may be selected instead. Further, in the embodiment, the superlattice structure of the light emitting layer has a period twice as long as the lattice spacing of the substrate crystal. However, the same effect can be obtained if the period is an even number times. In addition, as impurities to be added to the light emitting layer, G
Group IV elements such as e and Sn can also be used. Further, as the crystal type, other hexagonal crystal types such as 4H type, 2H type, and 15R type other than 6H can be used.

The light emitting layer having a super lattice structure is made of Si
A strained superlattice structure of C and AlN or GaN may be grown and grown on the (11-20) or (1-100) plane. Further, as a method of growing the light emitting layer, other vapor phase growth methods such as a molecular beam epitaxial method can be used other than the MOCVD method. In addition, various modifications can be made without departing from the scope of the present invention.

[0026]

As described in detail above, according to the present invention, the plane orientation of the SiC crystal substrate having a hexagonal crystal structure is changed to (11-2).
0) or (1-100), and the light emitting layer has a periodic structure that is an even multiple of the lattice spacing of the substrate crystal, so that the band structure of the light emitting layer can be made to be a direct transition type. It is possible to realize a semiconductor light emitting device that can emit light with a higher luminous intensity and a shorter wavelength than blue.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a light emitting diode according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a difference in light emission characteristics between an example and a conventional example.

FIG. 3 is a sectional view showing a schematic configuration of a light emitting diode according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a band structure of a conventional element.

[Explanation of symbols]

 11 n-type SiC substrate, 12 n-type light emitting layer, (6H-type SiC) 13 p-type layer (6H-type SiC), 14 p-side electrode, 15 n-side electrode, 21 n-type buffer layer (2H 22 ... n-type light-emitting layer (6H or 4H-type SiC); 23 ... p-type layer (2H-type SiC).

Continuation of the front page (56) References JP-A-61-78189 (JP, A) JP-A-63-207186 (JP, A) JP-A-59-197187 (JP, A) JP-A-61-145886 (JP, A) , A) JP-A-4-137777 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00

Claims (3)

(57) [Claims] A silicon carbide (Si) having a hexagonal crystal structure
C) and a substrate crystal formed on the substrate crystal.
A light emitting layer having a superlattice structure containing silicon carbide (SiC) , wherein a principal plane of the substrate crystal is set to a plane orientation of (11-20) or (1-100), and a superlattice of the light emitting layer is provided. A semiconductor light emitting device having a structure whose period is set to an even multiple of the lattice spacing of the substrate crystal. 2. A silicon carbide (Si) having a hexagonal crystal structure.
C), the main surface of the first conductivity type substrate crystal made of (11-2)
0) or (1-100) plane orientation, growing a first conductivity type light emitting layer having a superlattice structure containing silicon carbide (SiC) on the main surface of the substrate crystal, and emitting the light. Setting the superlattice structure of the layer to an even multiple of the lattice spacing of the substrate crystal; and forming silicon carbide (Si) on the light emitting layer.
Growing a second conductivity type semiconductor layer including C) . 3. The method according to claim 2, wherein the step of growing and forming the light emitting layer comprises alternately stacking layers doped with impurities and layers not doped with impurities.