JPH04306885A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To enable a semiconductor light emitting element to be enhanced in outward light emission efficiency by a method wherein a barrier section is provided to a second electrode, a first electrode, and a part of a light emitting region to serve as a barrier to carriers injected into a light emitting region of a first carrier. CONSTITUTION:After a growth substrate is subjected to a surface treatment, SiN is deposited on a P-type SiC contact layer 13 and formed into a pattern. At this point, this SiN 17 is made to serve as a barrier layer. Furthermore, a P-side Al primary electrode 14 is formed in a radial manner starting from the center of the SiN layer 17 through a photoresist process. In succession, an N-side Ni electrode 15 is formed all the surface of an N-type SiC crystal substrate 11, which is thermally treated. The thermally treated body is separated into elements conforming to a forming pattern, the body concerned is mounted on a stem making the N-type SiC crystal substrate 11 confront the stem with a conductive adhesive agent as another resistive layer, and an Au bonding wire 16 is bonded to the patterned Al electrode on the SiN insulating section 17.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device whose characteristics are improved by optimizing its electrode structure.

0002

2. Description of the Related Art Conventional technology will be explained using a SiC blue light emitting diode as an example. A SiC blue light emitting diode is manufactured by growing a 6H type crystal on a 6H type or 4H type SiC single crystal substrate. Subsequently, Al was grown on the n-type SiC crystal substrate 71 by liquid phase epitaxial growth.
An n-type SiC light emitting layer 72 doped with N is grown, and subsequently a p-type SiC contact layer 73 doped with Al is grown (FIG. 7(a)).

Next, after surface-treating the growth substrate by wet etching or the like, Al is applied to the p-type SiC contact layer 73 side as described in 1985 Spring Proceedings of the Japan Society of Applied Physics, 29a-W-1, P586. A P-side electrode 74 and an n-side Ni electrode 75 are formed on the n-type SiC crystal substrate 71 side, in which a layer and a Si layer are sequentially laminated. Or, JP-A-2-
p-type SiC as described in Publication No. 196421
A P-side electrode in which a Ti layer and an Al layer are successively laminated on the contact layer 73 side, and an n-side Ni electrode 7 on the n-type SiC crystal substrate 71 side.
5 (FIG. 7(b)).

[0004] Next, the pattern is removed using a photoresist process, leaving a part on the light extraction side to be wire bonded and a part on the stem side to which a conductive adhesive is applied, and then heat treated at a high temperature. Then 200 steps along the patterning
The elements are separated into ~300 μm square elements, and the stem is mounted using a conductive adhesive and wire bonded using an Au wire 76 (FIG. 7(c)). In this case, since n-type SiC absorbs less light, light can be extracted efficiently by mounting the n-type SiC crystal substrate 71 side upward. However, if the thickness of the p-type SiC contact layer 73 is not made sufficiently thick, the conductive adhesive applied to the stem side will creep up to the p-n junction, causing a short circuit failure. Increasing the thickness of the p-type SiC layer requires increasing the crystal growth time, resulting in poor productivity. Furthermore, if the thickness of the p-type SiC contact layer 73 is increased, the absorption of light reflected from the lower electrode surface will increase, and the external light emission efficiency will deteriorate.

Instead of such a method of mounting the n-type SiC crystal substrate 71 side upward, a method of mounting it on the p-type SiC contact layer 73 that can provide a sufficient distance to the p-n junction can be considered (FIG. 7). (d)(e)). Reduce the impurity concentration to about 5 x 1018/cm3, and
By making it as thin as approximately m, absorption of light by the p-type SiC contact layer 73 can be reduced. However, a new problem arose. In the p-type SiC contact layer 73, if the impurity concentration is lowered to about 10×18/cm3 or less (resistivity is about 0.05 Ω·cm or more) or the thickness is reduced to about 1 to 6 μm, the The current spreads less, and the light is emitted mainly directly below the electrode 74 and around the electrode. Therefore, since the light emission was blocked by the electrode 74, the external light emission efficiency was not improved. Particularly, the wire bonding portion of the electrode 74 is required to have a size necessary and sufficient for wire bonding, so a decrease in external light emission efficiency due to this portion was unavoidable.

[0006]

[Problems to be Solved by the Invention] As described above, in conventional semiconductor light emitting devices, when a contact layer with a low impurity concentration and a thin layer is used as a light extraction surface, light emission is mainly performed directly under the electrode and around the electrode. Therefore, there was a problem in that light emission was inhibited from the electrodes, especially the wire bonding portion, and the external light emission efficiency was deteriorated. The present invention takes these points into consideration and aims to provide a semiconductor element with high external light emission efficiency. [Structure of the invention]

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a light-emitting region that emits light by recombination of injected carriers, and a light-emitting region that emits light directly to the surface of the light-emitting region from which the light is extracted. Alternatively, a first layer is formed through a low resistivity layer and injects first carriers into the light emitting region.
a second electrode formed directly in the light emitting region or via another low resistivity layer and injecting second carriers into the light emitting region; and between the first electrode and the light emitting region. The present invention provides a semiconductor light emitting device characterized in that it is provided with a barrier portion formed in a part of the semiconductor light emitting device and serving as a barrier to injection of the first carriers into the light emitting region.

[0008] Here, the light-emitting region is a region where holes and electrons are injected and emit light when recombined. electrons are injected from the first electrode. At this time, holes or electrons injected from the first electrode are used as first carriers, and carriers injected from the second electrode are used as second carriers.

[0009]

According to the present invention, by forming a barrier portion between the first electrode and the light emitting region, no current flows through this portion, and no light is emitted under the first electrode. Therefore, the current that conventionally flowed there can be distributed to other areas, improving external light emission efficiency. Further, the main electrode can supply power to the light emitting region without inhibiting light emission as much as possible.

0010

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

FIG. 1 is a perspective view showing the manufacturing process of a semiconductor light emitting device according to a first embodiment of the present invention. An n-type SiC light-emitting layer 12 doped with Al and N as a light-emitting region is grown to a thickness of approximately 40 μm on an n-type SiC crystal substrate 11 by liquid phase epitaxial growth, followed by a p-type contact layer 13 doped with Al as a low resistivity phase. is grown to approximately 6 μm (Fig. 1
(a)).

Next, after surface-treating the growth substrate with hydrochloric acid, nitric acid, hydrofluoric acid, or a mixture thereof, SiN is deposited on the p-type SiC contact layer 13, and a pattern of 80 μmΦ is formed at a pitch of 250 μm using a photoresist process. do. Here, this SiN17 was used as a barrier layer (Fig. 1
(b)). Furthermore, using a photoresist process, 8
A P-side Al main electrode 14 having a width of 3 μm is formed radially from the center of the SiN layer having a diameter of 0 μm (FIG. 1(c)).

Next, on the n-type SiC crystal substrate 11 side, an n-side N
An i-electrode 15 is formed on the entire surface and heat-treated at a high temperature of 1000°C. This was separated into 250 μm square elements according to the formation pattern, and the n-type SiC crystal substrate 11 side was mounted on the stem as another low resistivity layer using a conductive adhesive.
A on the SiN insulating part 17 formed in a pattern of μmΦ
Wire bonding is performed to the l electrode using an Au bonding wire 16 with a diameter of 25 μm. At that time, the tip of the Au wire is approximately 7
It becomes 5 μmΦ (Fig. 1(d)). The external light emitting efficiency of the semiconductor light emitting device thus obtained was approximately 1%.

In this embodiment, the width of the main electrode formed radially is 3 μm, but the external light emission efficiency depends on the main electrode width (main electrode width ratio) to the contact layer thickness. Figure 2 (
A) shows a characteristic diagram in this example. The area ratio (main electrode area ratio) occupied by the main electrode to the area of the light extraction surface excluding the electrode portion is 1/2. When the main electrode width ratio exceeds 1/2, the external luminous efficiency decreases, and it ranges from 1/6 to 1/2.
A good value can be obtained at a certain level. On the other hand, the external luminous efficiency also depends on the main electrode area ratio, and the characteristics when the main electrode width ratio is set to 1/2 are shown in FIG. 2(b). As shown in the figure, good external light emission efficiency can be obtained when the main electrode area ratio is 1/20 to 1/2.

[0015]Although it is desirable that the size of the barrier part is at least the same size as the wire bonding part of the electrode, good external luminous efficiency can be obtained even if the barrier part is smaller than the outer periphery by up to 1/2 of the contact layer thickness. . Although it is effective even if it is even smaller, it is desirable that the area is 2/3 or more of the area of the wire bonding part of the electrode. Furthermore, the first electrode may be formed not only directly above the barrier layer but also at a position shifted from the center of the barrier layer so as to cover a part of the barrier layer. The materials are SiO2,
Other insulating materials such as Al2O3, ZrO2 can also be used.

[0016] Here, the light emitting region has a structure capable of emitting light by recombination of carriers, and includes a PN junction structure,
It can also be formed by a Schottky junction structure of a semiconductor and a metal, or a MiS structure of a junction of a semiconductor and an insulating metal. Furthermore, the low resistivity layer is a layer made of a non-insulating material such as a semiconductor or metal having different conductivity types.

FIG. 3 shows a perspective view of a semiconductor light emitting device according to a second embodiment of the present invention. This embodiment is also manufactured in the same manner as the first embodiment, but the barrier portion 18 is made of Ni, which is a non-ohmic metal. In this example as well, the same effects as in the first example were obtained. Furthermore, unlike when forming an Al electrode on a semiconductor insulator to form an Al electrode on a non-ohmic metal, the effect that Al does not cause ball-up was also obtained. As the material of the barrier part, other non-ohmic metals such as Au, W, Mo, and Pt, which are non-ohmic to P-SiC, can also be used.

FIG. 4 shows a perspective view of a semiconductor light emitting device according to a third embodiment of the present invention. This example is also produced in the same manner as the first and second examples, but the barrier part is formed of Ni 18 on SiN 17, and the barrier part is composed of two layers. In this example as well, the same effects as in the second example were obtained.

[0019] The barrier part is also made of SiO2, Al2O
Combinations of at least one of other insulating materials, such as No. 3, ZrO2, and other non-ohmic electrodes, such as Au, W, Mo, and Pt, can be used. At this time, it may be a laminated film or not.

FIG. 5 shows a perspective view of a semiconductor light emitting device according to a fourth embodiment of the present invention. This example is also manufactured in the same manner as the first to third examples, but the shape of the main electrode is different. That is, in this embodiment, the main electrode is formed in a grid shape. Here, since the main electrode width ratio and main electrode area ratio were set as in the first to third embodiments, the same effects as in the first to third embodiments were obtained. The shape of the main electrode may be other than that of this embodiment as long as the main electrode width ratio and main electrode area ratio are within the ranges described in the first embodiment.

FIG. 6 is a perspective view of a semiconductor light emitting device according to a fifth embodiment of the present invention. This example differs from the first to fourth examples in that the light-emitting layer has In0.5 (Ga1 -xA
lx) (0≦x≦1).

[0022] On the n-type GaAs substrate 21, an n-type InGaA
An IP cladding layer 22, an InGaAlP active layer 23, a P-type InGaAlP cladding layer 24, and a P-type GaAlAs contact layer 25 are formed in this order. In the device in which the Au-Ge barrier portion 19 and electrodes were formed in the same manner as in the first to fourth examples, a high luminous efficiency of 1.5% was obtained.

[0023] In this example, In0.5 (G
Although a1-xAlx)0.5P (0≦x≦1) was used, it is also effective to use other semiconductor light-emitting materials such as Ga1-xAlxAs (0≦x≦1)GaP. Furthermore, although an n-type substrate is used, a p-type substrate may also be used.
-Au etc. may be used. Further, the barrier portion may be made of a semiconductor having a conductivity different from that of the contact layer or having a high resistance, for example, an undoped or I-type semiconductor. Alternatively, a material that forms a Schottky junction with the barrier contact layer may be used. In addition, various modifications can be made without departing from the gist of the present invention.

[0024]

As described in detail above, by reducing the amount of current that does not contribute to the light emitted externally from the semiconductor light emitting device, the external light emitting efficiency is improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the manufacturing process of a semiconductor light emitting device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining the first embodiment of the present invention.

FIG. 3 is a perspective view showing a semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a semiconductor light emitting device according to a third embodiment of the present invention.

FIG. 5 is a perspective view showing a semiconductor light emitting device according to a fourth embodiment of the present invention.

FIG. 6 is a perspective view showing a semiconductor light emitting device according to a fifth embodiment of the present invention.

FIG. 7 is a perspective view showing a conventional light emitting element.

[Explanation of symbols]

11, 71...n-type SiC crystal substrate 12,72...n-type SiC light emitting layer 13,73...P-type SiC contact layer 14, 74...P side Al main electrode 15...n-side Ni electrode 16...Bonding wire 17...SiN barrier part 18...Ni barrier part 19...Au-Ge barrier part 20, 75...n side electrode 21...n-type GaAs substrate 22...n-type InGaAlP cladding layer 23...InGaAlP active layer 24...P-type InGoAlP crat layer 25...P-type GaAlAs contact layer 76...P side electrode

Claims (3)

[Claims] 1. A light emitting region that emits light by recombination of injected carriers; and a first carrier formed on the surface of the light emitting region from which the light is extracted either directly or through a low resistivity layer; a first electrode for injecting second carriers into the light emitting region; a second electrode formed directly in the light emitting region or via another low resistivity layer and injecting second carriers into the light emitting region; A semiconductor light emitting device comprising: a barrier portion formed between the light emitting regions and serving as a barrier to injection of the first carriers into the light emitting regions. 2. The low resistivity layer has an impurity concentration of 5×10 −18 cm − at least in the vicinity of contact with the first electrode.
2. The semiconductor light emitting device according to claim 1, wherein the contact layer has a thickness of 3 μm or less and a thickness of 6 μm or less. 3. The first electrode has a width such that an area in contact with the surface of the light emitting region directly or through the low resistivity layer is 1/2 or less of an area of a region from which light can be extracted. ,
3. The semiconductor light emitting device according to claim 2, wherein the thickness is 1/2 or less of the thickness of the contact layer.