JPH0430583A - Manufacture of silicon carbide light emitting diode - Google Patents

Abstract

PURPOSE:To increase carrier concentration of a p-type SiC layer while holding crystallinity of each grown layer by inclining the crystal growing surface of a board when the SiC layer to become a light emitting layer is grown from a predetermined surface, and forming the crystal growing surface of the SiC layer when the SiC layer is grown at a predetermined surface. CONSTITUTION:An n-type SiC board 1 having a main surface in a {0001} plane is prepared, one main surface 1a such as a surface in a plane (0001) is mechanically polished along one direction, an inclined surface 1a inclined at a predetermined angle is formed as a crystal grown surface. An n-type SiC layer 2 is epitaxially grown on the inclined surface 1a' of the board 1. The grown layer 2 is mechanically polished, and the surface in plane (0001) is exposed on the surface 2'. The surface 2' of the polished layer 2 is clarified by etching, and a p-type SiC layer 3 is epitaxially grown on the surface 2' of the layer 2 by using a liquid epitaxial method similarly to the layer 2 at 1700 deg.C of a growing temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a method for manufacturing a silicon carbide light emitting diode.

(B) Prior Art Generally, silicon carbide (SiC) is attracting attention as an environmentally resistant semiconductor material due to its physical and chemical properties such as excellent heat resistance and mechanical strength, and resistance to radiation.

Furthermore, although SiC crystal is an indirect transition type IV-■ compound, SiC crystal has various crystal structures such as cubic and macrogonal for the same chemical composition, and the forbidden band width thereof is 2. It has a wide range of 39 to 3.33 eV, and
Since it is possible to form a pn junction, it is seen as a promising material for light emitting diodes that emit visible light in the entire wavelength range from red to blue. Among them, about 3 at room temperature
6H type SiC crystal, which is a type of macrogonal crystal with a forbidden band width of eV, is used as a material for blue light emitting diodes.

The growth of such SiC crystals is usually carried out by liquid phase epitaxial growth (LPE) or chemical vapor deposition (CV).
As a specific example of the former LPE method, the Journal of Applied Phys.
sics, 50(12), December 1979
, 8215-8225, and as a specific example of the latter CVD method, Journal of Applied Phys.
sics, 19(7), July 1980. L353
-Reported in Ryowabun of L356. In any case of such prior art, 6 used for epitaxial growth.
As the crystal growth surface of the H type SiC single crystal substrate, (0
001) plane is used.

Here, in the 6H type SiC single crystal, (00
There is a (000 plane) which is crystallographically equivalent to the (01) plane, but these planes are (0001) plane and (0001 plane) depending on whether the atoms on the surface are silicon (Si) or carbon (C). OO
OT) surface. In addition, these two planes together will be hereinafter referred to as a (0001) plane.

Further, conventional blue light emitting diodes using such SiC are described in, for example, the magazine "Electronic Technology" Vol. 26, No. 14, 128.
- It is described on page 129.

As shown in FIG. 3, such a conventional SiC light emitting diode has an n-type SiC layer (12) serving as a light emitting layer and a p-type SiC layer (13) on the main surface of a substrate (11) made of n-type SiC. are sequentially epitaxially grown, and the p-type SiC layer (13
), and an n-side electrode (15) is formed on the other main surface of the substrate (11).

(c) Problems to be Solved by the Invention The present applicant has proposed a technique for superimposing a hexagonal SiC substrate on a hexagonal SiC substrate.
When epitaxially growing a single crystal, by using a crystal growth plane of the substrate that is inclined from the (00014 plane), the dependence of the epitaxial growth on the substrate is strengthened, a SiC single crystal with good crystallinity is obtained, and the produced SiC It was discovered that the long wavelength shift in the early stage of operation of a light emitting diode can be suppressed, and the invention was proposed in Japanese Patent Application Laid-Open No. 179516/1982 and Japanese Patent Application No. 52302/1999.

However, with this method, the carrier concentration of the p-type SiC layer epitaxially grown on the n-type SiC layer was not sufficiently increased, and a low-resistance p-type SiC layer could not be obtained. Therefore, there was a problem in that the contact resistance between the p-type SiC layer and the p-side electrode was large, and the forward voltage (device voltage when 20 mA was applied) and driving power of the light emitting diode were increased. Furthermore, since the carrier concentration of the p-type SiC layer is low, the efficiency of hole injection into the n-type SiC layer, which is a light emitting layer, is low, which is a cause of not being able to obtain a high-brightness SiC light emitting diode.

Therefore, the present invention maintains the crystallinity of each growth layer while p.
The technical challenge is to increase the carrier concentration of the type SiC layer.

(d) Means for Solving the Problems The present invention is a method for manufacturing a silicon carbide light emitting diode, in which an n-type silicon carbide layer and a p-type silicon carbide layer are sequentially epitaxially grown on a hexagonal silicon carbide single crystal substrate, comprising: In order to solve the above problem, the crystal growth plane of the substrate on which the n-type silicon carbide layer is epitaxially grown is (0001
) plane, and the crystal growth plane of the n-type silicon carbide layer on which the p-type silicon carbide layer is epitaxially grown is a (00011 plane).

(e) Effect The present invention provides for the crystal growth plane of the substrate when growing the n-type SiC layer which becomes the light emitting layer to be a plane inclined from the (0001) plane,
By making the crystal growth plane of the n-type SiC layer the (0001) plane when growing the p-type SiC layer, the carrier concentration of the p-type SiC layer can be increased while maintaining high crystallinity of the light-emitting layer.

(f) Example First, the principle of the present invention will be explained with reference to FIG.

Figure 2 shows a SiC substrate (
A p-type Si substrate doped with At as a p-type impurity was formed on a SiC substrate (hereinafter referred to as an inclined substrate) having a main surface having a plane inclined by 5 degrees from the 00011 plane.
When the C layer is epitaxially grown, the carrier concentration of the p-type SiC layer obtained with respect to the amount of A1 added is shown by a broken line (positive substrate) and a solid line (tilted substrate), respectively.

As is clear from the figure, it is possible to obtain a relatively higher carrier concentration for the same amount of A1 when the p-type SiC layer is grown on a positive substrate than on an inclined substrate. can. Although this is not clear, it is thought that there are many atomic steps on the surface of the inclined substrate, which suppresses the incorporation of At atoms into the growing crystal.

Therefore, it is effective to make the crystal growth plane of the substrate inclined from the (00011 plane) to improve the crystallinity of the growing layer.
However, on the other hand, it also suppresses the incorporation of A1 into the growth layer.

In consideration of the above, the present invention sets the crystal growth plane of the substrate to (00011 plane) when growing a light-emitting layer that is required to have high crystallinity, that is, an n-type SiC layer, and also sets the grown n-type By polishing the surface of the SiC layer, the crystal growth plane of the n-type SiC layer when growing the p-type SiC layer, which requires a large carrier concentration, is set to the (0001) plane.

Next, an embodiment of the method of the present invention will be described with reference to FIG.

FIG. 1(a) shows the first step, in which a 6H type n-type SiC substrate (1) having a 10001) plane as a main surface is prepared, and one main surface (1a), for example, a (0001) plane, is prepared. It is mechanically polished along one direction to form an inclined surface (la') inclined at a certain angle (θ in the figure), for example, 5 degrees, and this is used as the crystal growth surface.

FIG. 1(b) shows the second step, in which the inclined surface (la') of the substrate (1) is cleaned by etching, and then the well-known liquid phase epitaxial method is used (1) at a growth temperature of 1700.
℃, the slope (la') of the n-type SiC substrate (1)
) on which an n-type SiC layer (2) is epitaxially grown.

At this time, the n-type SiC layer (2) is doped with 1.3X10-''wt% of Si, N4, which is the raw material for n-type impurities, and 1.1 at.% of A1, which is the raw material for p-type impurities.
1% added.

FIG. 1(C) shows the third step, in which the grown n-type Si
The C layer (2) is mechanically polished to change the (0001) plane to the surface (
2′) (i.e. surface (2″) is (0001)
).

FIG. 1(d) shows the fourth step, in which polished n-type Si
After cleaning the surface (2゛) of the C layer (2) by etching, the above n-type Si
A p-type SiC layer (3) is epitaxially grown on the surface (2') of the C layer (2). At this time, the p-type SiC layer (3) is doped with 1°56 at% of A1, which is a raw material for p-type impurities.

FIG. 1(e) shows the fifth step, in which the p-type SiC layer (3)
A p-side electrode (4) and an n-side electrode (5) are formed on the other main surface (1b) of the upper and n-type SiC substrates (1), respectively.

This example device was manufactured according to the above method, and the comparative device was manufactured in the same manner as this example except that the third step in this example was omitted (i.e., n
When compared with the SiC layer with the crystal growth plane tilted from the (000T) plane, the device of this example had a forward voltage about 15% lower and a luminous intensity of about 15% lower than the comparative device. It increased by 20%. This is the p-type SiC of this embodiment device.
This is because the carrier concentration of layer (3) was higher than that of the comparative device.

Further, when the reliability of the device was tested by aging tests and the like, no difference in deterioration characteristics appeared between the device of this example and the comparative device. This is because the n-type SiC layer (2), which is the light emitting layer of the device of this example, was grown with good crystallinity.

As described above, in the apparatus of this embodiment, the crystal growth surface of the substrate (1) is
Although the crystal growth plane is inclined by 5 degrees from the (00011) plane, the same effect as in the apparatus of this embodiment can be obtained if the crystal growth plane is inclined by 3 degrees or more from the (00011) plane.

However, when the tilt angle becomes large, the substrate (1) and the n-type S
Since the polishing time for the iC layer (2) increases and the manufacturing cost increases, the inclination angle is preferably 20 degrees or less.

(G) Effects of the Invention According to the method of the present invention, the crystal growth plane of the substrate when growing the n-type SiC layer that becomes the light-emitting layer is a plane inclined from the (00011 plane), and the crystal growth plane when growing the p-type SiC layer is By setting the crystal growth plane of the n-type SiC layer to the (00011 plane), it is possible to increase the carrier concentration of the p-type SiC layer while maintaining high crystallinity of the light emitting layer, resulting in high reliability. In addition, a SiC light emitting diode with low forward voltage and high brightness can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of each process for explaining an embodiment of the present invention, FIG. 2 is a characteristic diagram for explaining the present invention in detail, and FIG. 3 is a cross-sectional view of a conventional device.

Claims (1)

[Claims] (1) In the method for manufacturing a silicon carbide light emitting diode, in which an n-type silicon carbide layer and a p-type silicon carbide layer are sequentially epitaxially grown on a hexagonal silicon carbide single crystal substrate, the n
The crystal growth plane of the substrate on which the type silicon carbide layer is epitaxially grown is a plane inclined from the {0001} plane, and the crystal growth plane of the n-type silicon carbide layer on which the p-type silicon carbide layer is epitaxially grown is the {0001} plane. } surface.