JPH11145076A - Ohmic electrode, its forming method and laminate for ohmic electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ohmic electrode and its forming method which can reduce the heating temperature for ohmic contact, and a laminate for the ohmic electrode. SOLUTION: A first metal layer 11α composed of Pd and a second metal layer 11β composed of alloy of Ge and Au are laminated in order on one surface side of a substrate 20 composed of N-type GaAs, and an N-side electrode 10 is formed by heating at a temperature in the range from at least 175 deg.C to at most 250 deg.C. Excellent ohmic contact is obtained between the substrate 20 and the N-side electrode 10. When the respective layers 21-28 composed of II-VI compound semiconductor are formed on the other surface side of the substrate 20, the N-side electrode 10 can be formed without deteriorating crystallinity of those layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to GaAs and GaI.
The present invention relates to an ohmic electrode for an electrode connecting portion formed by nAs mixed crystal, a method for forming the same, and a laminate for the ohmic electrode.

[0002]

2. Description of the Related Art In recent years, in various technical fields using light, for example, demands for higher density and higher resolution of recording / reproducing for optical disks and magneto-optical disks, high-brightness display devices, low-loss optical fiber communication, and the like. There is a growing momentum for the development of devices and also optical analysis devices for DNA or specific chemical substances. Therefore, semiconductor light-emitting devices using II-VI compound semiconductors capable of emitting green or blue light are being developed as these light sources.

Conventionally, as a semiconductor light emitting device using a II-VI compound semiconductor, for example, an n-VI compound semiconductor formed on a GaAs substrate is used.
It is known that a mold clad layer, an active layer, a p-type clad layer and the like are sequentially laminated, and electrodes are formed on the p-type clad layer and on the back surface of the substrate, respectively.

Incidentally, in order to secure stable operation in such a semiconductor light emitting device, a technique relating to an ohmic electrode is extremely important. For example, n-type G
As an ohmic electrode for a substrate made of aAs,
A device using an alloy of gold (Au) and germanium (Ge) is known. In the case of this material, a heat treatment for alloying at 300 ° C. or higher is required to obtain ohmic contact. However, the growth temperature when growing a II-VI group compound semiconductor layer on a substrate is, for example, about 280 ° C. in the case of molecular beam epitaxy (MBE). Therefore, if this ohmic electrode is formed after growing a layer of the II-VI compound semiconductor on the substrate, the heating temperature of the electrode is higher than the growth temperature, and the II-VI compound semiconductor The crystallinity of the layer deteriorates, and the characteristics deteriorate.

Therefore, conventionally, for example, when a layer of a II-VI compound semiconductor is grown by MBE, the substrate is bonded to the substrate holder using indium (In). An ohmic electrode was formed. In this case, the heating performed to clean the substrate before growing the layer of the II-VI compound semiconductor may form an alloy at the interface between indium constituting the ohmic electrode and GaAs constituting the substrate. it can. Therefore, it is not necessary to perform heat treatment for alloying after growing the II-VI group compound semiconductor layer.

[0006]

However, this ohmic electrode has a problem that significant unevenness occurs at the interface with the substrate, and it is difficult to separate the semiconductor light emitting devices formed on the substrate by cleavage. Was.
In addition, since heating must be performed at a high temperature for alloying, the electrode cannot be formed by polishing the substrate after growing the II-VI compound semiconductor layer, and the manufacturing process is significantly limited. There was also a problem that would.

The present invention has been made in view of the above problems, and has as its object to provide an ohmic electrode capable of lowering the heating temperature for ohmic contact, a method for forming the same, and a laminate for the ohmic electrode. Is to do.

[0008]

SUMMARY OF THE INVENTION An ohmic electrode according to the present invention is connected to an electrode connection formed of a semiconductor containing at least gallium of a group III element gallium and indium and a group V element arsenic. And an ohmic contact layer made of a composite containing at least palladium and germanium selected from the group consisting of palladium, germanium, and gold.

In the method of forming an ohmic electrode according to the present invention, an ohmic electrode is formed on an electrode connecting portion formed of a semiconductor containing at least gallium of a group III element gallium and indium and a group V element arsenic. A laminating step of sequentially laminating a first metal layer made of palladium and a second metal layer made of at least germanium of germanium and gold from the side of the electrode connecting portion; And a heating step of heating the second metal layer and the second metal layer.

[0010] A laminate for an ohmic electrode according to the present invention is characterized in that an ohmic electrode is connected to an electrode connection formed of a semiconductor containing at least gallium of a group III element gallium and indium and a group V element arsenic. Forming a first layer of palladium
And a second metal layer made of at least germanium of germanium and gold, in that order from the electrode connection part side.

In the ohmic electrode according to the present invention, the ohmic contact layer is made of a composite containing at least palladium and germanium selected from the group consisting of palladium, germanium and gold. Therefore, even if heating for ohmic contact is performed at a low temperature, good ohmic contact can be obtained between the electrode connection portion formed of a semiconductor containing at least gallium of gallium and indium and arsenic of a Group V element. Can be

In the method of forming an ohmic electrode according to the present invention, a first metal layer made of palladium and a second metal layer made of at least germanium of germanium and gold are sequentially laminated on the electrode connection portion. After that, it is heated.

In the laminate for an ohmic electrode according to the present invention, the first electrode made of palladium is connected to the electrode connecting portion.
And a second metal layer made of at least germanium out of germanium and gold. Therefore, even if the heating for the ohmic contact is performed at a low temperature, the ohmic contact can be obtained between the electrode connection portion formed of the semiconductor containing at least gallium of gallium and indium and the arsenic of the group V element.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that, in the following embodiments, the ohmic electrode of the present invention is referred to as II-VI
A case where the present invention is applied to an n-side electrode of a semiconductor light emitting device using a group III compound semiconductor will be described. Further, in the following embodiments, a laminate for an ohmic electrode is also described in the description of the ohmic electrode.

FIG. 1 shows a first embodiment of the present invention.
N-side electrode 10 which is an ohmic electrode according to the embodiment of FIG.
It represents the configuration of FIG. The n-side electrode 10 is made of n-type GaAs doped with, for example, silicon (Si) as an n-type impurity.
s is formed on one surface of the substrate 20. That is, here, the substrate 20 constitutes an electrode connection portion.

On the other side of the substrate 20, a buffer layer 21, an n-type cladding layer 22, a first guide layer 23, an active layer 24, a second layer
Guide layer 25, p-type cladding layer 26, contact layer 2
7 and the superlattice layer 28 are sequentially laminated. Substrate 20
Has a thickness in the laminating direction (hereinafter, simply referred to as a thickness) of, for example, 100 to 350 μm.

The buffer layer 21 has a thickness of, for example, 200
nm, and is made of n-type ZnSSe to which chlorine (Cl) is added as an n-type impurity. The n-type cladding layer 22 has a thickness of, for example, 1 μm, and is made of an n-type ZnMgSSe mixed crystal to which chlorine is added as an n-type impurity. For example, the first guide layer 23 has a thickness of 10
It is made of ZnSSe mixed crystal to which chlorine is added as an n-type impurity or no impurity is added. The active layer 24 is made of, for example, a ZnCdSe mixed crystal having a single quantum well structure with a thickness of 6 nm.

The second guide layer 25 has, for example, a thickness of 1
It is made of ZnSSe mixed crystal to which nitrogen (N) is added as a p-type impurity or no impurity is added. The p-type cladding layer 26 has a thickness of, for example, 1 μm.
p-type ZnM doped with nitrogen as a p-type impurity
It is composed of gSSe mixed crystal. Contact layer 27
Has a thickness of, for example, 1 μm and is made of a p-type ZnSSe mixed crystal to which nitrogen is added as a p-type impurity. The superlattice layer 28 is formed, for example, by alternately stacking p-type ZnSe to which nitrogen is added as a p-type impurity and p-type ZnTe to which nitrogen is added as a p-type impurity.

The superlattice layer 28 and the contact layer 27
Are formed in a band shape having a width of, for example, 10 μm, and serve as a current confinement portion for performing current confinement. Note that the superlattice layer 28 and the contact layer 27 extend in the direction perpendicular to the drawing in FIG. Super lattice layer 28
An insulating layer 29 made of an insulating material such as alumina (Al ₂ O ₃ ) is formed in a region on the side of the super lattice layer 28 where the contact layer 27 is not formed.

On the insulating layer 29 and the superlattice layer 28 (ie, on the side opposite to the substrate 20), a p-side electrode 30 is provided. The p-side electrode 30 includes, for example, a palladium layer 31 made of palladium (Pd) having a thickness of 10 nm, a platinum layer 32 made of platinum (Pt) having a thickness of 100 nm, and a gold layer 33 made of gold having a thickness of 300 nm. Are sequentially laminated from the superlattice layer 28 side.

On the other hand, the n-side electrode 10 has an ohmic contact layer 11 made of a composite containing at least palladium and germanium selected from the group consisting of palladium, germanium and gold. The composite forming the ohmic contact layer 11 is a first metal layer 1 made of palladium.
Alloy of 1α, germanium and gold (eg eutectic alloy)
The second metal layer 11β is obtained by heating a stacked body sequentially stacked from the substrate 20 side. Note that the laminate before heating the composite corresponds to the laminate for the ohmic electrode according to the present embodiment.

Here, it is considered that at least a part of the first metal layer 11α of the laminated body reacts with the substrate 20 by heating to form an alloy. In addition, it is considered that the first metal layer 11α and the second metal layer 11β of the stacked body sometimes react with each other at the interface by heating and are alloyed. That is, the ohmic contact layer 11 is composed of a composite having the first metal layer 11a containing palladium and the second metal layer 11b containing germanium and gold. That is, the first metal layer 11a of the ohmic contact layer 11 may be made of palladium, or may contain an alloy of palladium and another element. The second metal layer 11b of the ohmic contact layer 11 is
It may be made of an alloy of germanium and gold, or may contain an alloy of germanium and gold with another element.

The thickness of the first metal layer 11a is, for example, 10 n
m to 500 nm, preferably 10 nm to 100 n
m. The thickness of the second metal layer 11b is, for example, 50 nm.
１０００1000 nm, preferably 50 nm〜300 n
m. Note that when a reaction occurs in the first metal layer 11a and the second metal layer 11b, the boundary between them may not be clear. However, even in that case, the first metal layer 11α and the second metal layer 11β in the stacked body before heating have the same thickness as that described for the first metal layer 11a and the second metal layer 11b. Is preferred.

Incidentally, the composite constituting the ohmic contact layer 11 is formed as described in the later-described forming method.
It is preferably heated at a temperature within the range of 175 ° C or more and 250 ° C or less.

The n-side electrode 10 having such a configuration is
It can be formed as follows. In addition, here, the manufacturing process of the semiconductor light emitting device shown in FIG. 1 to which the n-side electrode 10 is connected is also briefly described.

First, on the substrate 20 (ie, on the other side)
The buffer layer 21, the n-type cladding layer 22, the first guide layer 23, the active layer 24, the second guide layer 25, the p-type cladding layer 26, and the contact layer 27 are formed by, for example, the MBE method.
Then, the superlattice layer 28 is sequentially epitaxially grown (II-VI compound semiconductor layer forming step). The growth temperature at this time is, for example, 280 ° C.

Next, a part of the superlattice layer 28 and the contact layer 27 on the superlattice layer 28 side is selectively removed to form a band-shaped current confinement portion. Subsequently, an insulating layer 29 is selectively formed on the contact layer 27 from which the superlattice layer 28 has been selectively removed (current constriction portion forming step). After forming the insulating layer 29, a palladium layer 31, a platinum layer 32, and a gold layer 33 are sequentially deposited on the superlattice layer 28 and the insulating layer 29, and heated to form the p-side electrode 30. Electrode forming step).

Thereafter, one surface of the substrate 20 is polished, and the n-side electrode 10 is formed thereon. That is, first, the first metal layer 11 made of palladium is formed on one surface side of the substrate 20.
α and a second metal layer 11β made of an alloy of germanium and gold are sequentially laminated by vacuum deposition (n-side electrode forming step; laminating step). Note that this forms a laminate for the ohmic electrode according to the present embodiment.

Next, the laminated first metal layer 11α and second metal layer 11β are heated in a nitrogen gas atmosphere or a mixed gas atmosphere of nitrogen gas and hydrogen gas (n
Side electrode forming step; heating step). Here, the heating temperature is 17
It is preferable to be in the range of 5 ° C. or more and 250 ° C. or less.
At a temperature lower than 175 ° C., good ohmic contact with the substrate 20 cannot be obtained, and at a temperature higher than 250 ° C., each layer made of a II-VI compound semiconductor formed on the other surface of the substrate 20 ( The crystallinity of the buffer layer 21, the n-type cladding layer 22, the first guide layer 23, the active layer 24, the second guide layer 25, the p-type cladding layer 26, the contact layer 27 and the superlattice layer 28 is reduced. It is because. Thus, the n-side electrode 10 shown in FIG. 1 is formed.

The n-side electrode 10 thus formed is
It works as follows.

In the n-side electrode 10, since the ohmic contact layer 11 is composed of a composite containing palladium, germanium, and gold, even if heating for ohmic contact is performed at a low temperature, the ohmic contact layer 11 can be connected to the substrate 20. And a good ohmic contact is obtained. Therefore, the p-side electrode 30 and the n-side electrode 10
Is applied, a current is injected from the p-side electrode 30 into the active layer 24.

An experiment for examining the characteristics of the n-side electrode 10 was performed. In this experiment, as shown in FIG.
A sample was prepared in which a pair of ohmic contact layers 11 were formed on a substrate 20 made of As with a gap L1 of 0.1 mm. Here, each ohmic contact layer 11 has a long side length L2 of 1 mm and a short side length L3 of 0.
The rectangular shape was 3 mm, and the long sides were arranged to face each other. Each ohmic contact layer 11 has a thickness of 50 nm.
A first metal layer 11α of palladium and a thickness of 1
A second eutectic alloy of 50 nm germanium and gold
Of metal layers 11β were sequentially laminated from the substrate 20 side, and each was formed by heating for 5 minutes. The heating temperature at this time is 1
70 ° C, 175 ° C, 180 ° C and 250 ° C,
Four types of samples having different heating temperatures were prepared. For comparison, a sample without heating was also prepared.

With respect to these five types of samples, a voltage was applied between the pair of ohmic contact layers 11, and their current-voltage characteristics were examined. The result is shown in FIG.
And FIG. FIG. 3 shows a sample heated at 170 ° C., and FIG. 4 shows a sample heated at 180 ° C. As described above, in the sample heated at 170 ° C., almost no current flows at a voltage of less than 1 V, and when a voltage of 1 V or more is applied, the current increases accordingly, but the relationship is not linear. In addition,
A sample not heated is also not shown,
Similar results were obtained with the sample heated at 70 ° C. On the other hand, in the sample heated at 180 ° C., the increase in current with respect to the increase in voltage is linear, and it can be seen that good ohmic contact is obtained. Although not shown, 17
With respect to the sample heated at 5 ° C., ohmic contact sufficient for practical use was obtained. In addition, for the sample heated at 250 ° C., a result similar to the sample heated at 180 ° C. was obtained. That is, according to the n-side electrode (that is, ohmic electrode) 10 according to the present embodiment, it can be seen that good ohmic contact can be obtained by heating at a low temperature of about 180 ° C.

When the semiconductor light emitting device shown in FIG. 1 using the n-side electrode 10 according to the present embodiment was formed and operated, it was compared with a conventional semiconductor light-emitting device having an n-side electrode formed of indium. I was able to obtain the characteristics comparable to. That is, the semiconductor light emitting device can be operated at an operating voltage equal to or lower than that of the conventional semiconductor light emitting device, and a life equal to or longer than that of the conventional semiconductor light emitting device can be obtained.

As described above, according to the n-side electrode (that is, the ohmic electrode) 10 according to the present embodiment, since the ohmic contact layer 11 made of a composite containing palladium, germanium, and gold is provided, the ohmic contact is provided. A good ohmic contact with the substrate 20 can be obtained even if the heating is performed at a low temperature. Therefore, even if a layer of a II-VI compound semiconductor that cannot be heated at a high temperature is formed on the other surface side of the substrate 20, the n-side electrode 10 can be formed without lowering the crystallinity.
Therefore, while maintaining the characteristics of the semiconductor light emitting element,
The interface between the substrate 20 and the n-side electrode 10 can be flattened, and each semiconductor light emitting element formed on the substrate 20 can be easily cleaved and separated.

Further, according to the method for forming n-side electrode (ie, ohmic electrode) 10 according to the present embodiment, first metal layer 11α made of palladium and second metal layer made of an alloy of germanium and gold Since 11β and 11β are sequentially stacked from the substrate 20 side and then heated, the n-side electrode 10 according to the present embodiment can be realized.

Further, according to the laminate for the ohmic electrode according to the present embodiment, the first metal layer 11α made of palladium and the second metal layer 11β made of an alloy of germanium and gold are formed on the substrate 20. Since the electrodes are provided sequentially from the side, a good ohmic electrode can be obtained even if heating for ohmic contact is performed at a low temperature.

The n-side electrode 10 is connected to a second
This is preferable because a better ohmic contact can be obtained as compared with the case where the second metal layer 11b of the stacked body is made of germanium as in the n-side electrode 10 of the embodiment. This is because the alloy of germanium and gold has a lower melting point, and it is more likely that a reaction has occurred at the interface between the first metal layer 11a and the second metal layer 11b.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
N-side electrode 10 which is an ohmic electrode according to the embodiment of FIG.
It represents the configuration of FIG. The n-side electrode 10 has the same configuration as the n-side electrode 10 according to the first embodiment, except that the ohmic contact layer 11 is made of a composite containing palladium and germanium. Therefore,
Here, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

The ohmic contact layer 11 includes a first metal layer 11α made of palladium and a second metal layer 11a made of germanium.
And a metal layer 11β is formed of a composite obtained by heating a laminated body sequentially laminated from the substrate 20 side. That is, the stacked body for the ohmic electrode according to the present embodiment is the same as the second metal layer 11β in the first embodiment.
Is made of germanium.

The ohmic contact layer 11 has the first metal layer 11a containing palladium and the second metal layer 11b containing germanium as described in the first embodiment. It is composed of a complex. However, since the melting point of germanium is higher than the melting point of the alloy of germanium and gold, the first metal layer 11a is different from the ohmic contact layer 11 according to the first embodiment.
It is unlikely that a reaction has occurred at the interface between the first metal layer 11b and the second metal layer 11b.

The n-side electrode 10 having such a configuration is
It can be manufactured in the same manner as in the first embodiment, operates in the same manner as in the first embodiment, and can obtain the same effect. The same applies to a laminate for an ohmic electrode.

An experiment was conducted to examine the characteristics of the n-side electrode 10 according to the present embodiment. In this experiment, the same samples as those in the experiment described in the first embodiment were prepared except that the second metal layer 11β was made of germanium, and their current-voltage characteristics were examined. The results are shown in FIGS. FIG. 6 shows 170 ° C.
FIG. 7 shows a sample heated at 180 ° C. Thus, the sample heated at 170 ° C.
At a voltage lower than this, almost no current flows, and when a voltage of 1 V or more is applied, the current increases accordingly, but the relationship is not linear. Although not shown, the same result as that of the sample heated at 170 ° C. was obtained for the sample that was not heated. On the other hand, in the sample heated at 180 ° C., the increase in current with respect to the increase in voltage is linear, and it can be seen that good ohmic contact is obtained. Although not shown,
With respect to the sample heated at 175 ° C., ohmic contact sufficient for practical use was obtained. For the sample heated at 250 ° C., similar results were obtained as for the sample heated at 180 ° C. That is, according to the n-side electrode (that is, ohmic electrode) 10 according to the present embodiment, it can be seen that good ohmic contact can be obtained by heating at a low temperature of about 180 ° C.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
N-side electrode 10 which is an ohmic electrode according to the embodiment of FIG.
It represents the configuration of FIG. The n-side electrode 10 has the first structure except that the diffusion prevention layer 12 and the contact electrode layer 13 are sequentially provided on the opposite side of the ohmic contact layer 11 from the substrate 20.
It has the same configuration as the n-side electrode 10 according to the embodiment. Therefore, here, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The same applies to a laminate for an ohmic electrode.

The contact electrode layer 13 is for improving the adhesion between the wiring connected to the n-side electrode 10 and the n-side electrode 10. The thickness of the contact electrode layer 13 is, for example, 30
0 nm or more. Since the wiring connected to the n-side electrode 10 is often formed of gold, the contact electrode layer 13 is preferably formed of gold.

The anti-diffusion layer 12 comprises the ohmic contact layer 11
This is for preventing the diffusion of the second metal layer 11b (for example, the second metal layer 11b) and increasing the adhesion between the ohmic contact layer 11 and the contact electrode layer 13. This diffusion preventing layer 12
Has a thickness of, for example, 10 nm to 50 nm and is made of titanium. In addition, this diffusion prevention layer 12
As shown in FIG. 9, for example, the thickness is 10 nm to 50 n.
m and a thickness of 100 n
and a platinum layer 12b made of platinum of about m in order from the ohmic contact layer 11 side. In this case, the diffusion of the ohmic contact layer 11 can be further prevented as compared with the case where only the titanium layer is used.

The n-side electrode 10 having such a configuration is
After laminating the first electrode layer 11α and the second electrode layer 11β in the same manner as in the first embodiment (lamination step), the first electrode layer 11α and the second electrode layer 11β are laminated on the second electrode layer 11β (that is, the second electrode layer 11β The diffusion preventing layer 12 is laminated on the side opposite to the first electrode layer 11α (diffusion preventing layer forming step). Next, the diffusion preventing layer 12
(That is, on the side of the diffusion prevention layer 12 opposite to the second electrode layer 11β) (the step of forming a contact electrode layer). Thereby, a laminate for the ohmic electrode according to the present embodiment is formed. continue,
These are heated in the same manner as in the first embodiment (heating step). As a result, the n-side electrode 10 shown in FIG. 8 is formed.

As described above, according to the n-side electrode (that is, ohmic electrode) 10 according to the present embodiment, since the contact electrode layer 13 is provided, the adhesion to the wiring can be improved. Further, since the diffusion preventing layer 12 is provided, the diffusion of the ohmic contact layer 11 can be prevented, and the adhesion between the contact layer 13 and the ohmic contact layer 11 can be improved. The same applies to the laminate for the ohmic electrode according to the present embodiment.

Further, also in the n-side electrode 10 according to the present embodiment, the second metal layer 12β of the laminate may be made of germanium, as in the second embodiment.

The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in each of the above-described embodiments, the n-side electrode 10 is formed on the substrate 20 made of n-type GaAs, but the substrate 20 is made of an n-type InGaAs mixed crystal doped with, for example, silicon as an n-type impurity. On the other hand, an n-side electrode may be formed.
That is, the ohmic electrode of the present invention can obtain good ohmic contact with an electrode connecting portion made of a semiconductor containing at least gallium of the group III element gallium and indium and the group V element arsenic.

Incidentally, the ohmic electrode of the present invention has a G
A better ohmic contact can be obtained with an electrode connection made of InGaAs mixed crystal than with an electrode connection made of aAs. This is because the InGaAs mixed crystal has a smaller forbidden band width than GaAs and can add an n-type impurity at a higher concentration. Such a feature is called In
InGaAs having a large indium composition becomes more remarkable as the indium composition in the GaAs mixed crystal increases.
When the electrode connection is formed by a mixed crystal, a better ohmic contact can be obtained.

In each of the above embodiments, the substrate 20
Is composed of an n-type InGaAs mixed crystal, Ga
A layer made of a group II-VI compound semiconductor having a larger lattice constant than As can be stacked on the substrate 20. For example, when the n-type cladding layer 22, the active layer 14, the p-type cladding layer 26, and the like are configured as described in each of the above embodiments, a semiconductor light emitting device capable of emitting green or blue light can be obtained. When the n-type cladding layer and the p-type cladding layer are composed of a CdZnMgSe mixed crystal having a large lattice constant and the active layer is composed of a ZnCdSe mixed crystal, a semiconductor light emitting device capable of emitting red or green light can be obtained.

In each of the above embodiments, the case where the substrate 20 is used as the electrode connection portion has been described. However, for example, the n-type InG
A semiconductor layer made of aAs mixed crystal may be stacked, and the n-side electrode 10 which is the ohmic electrode of the present invention may be connected using the semiconductor layer as an electrode connecting portion.

Furthermore, in each of the above embodiments, the case where the present invention is applied to the n-side electrode 10 of the semiconductor light emitting device using the II-VI compound semiconductor has been described. The present invention can be widely applied to an electrode connected to an electrode connecting portion made of a semiconductor containing at least gallium of gallium and indium and arsenic of a group V element. The electrode connection part may be a substrate,
It may be a semiconductor layer. Note that, as described in each of the above-described embodiments, in the case where a II-VI group compound semiconductor layer is formed on the substrate 20 serving as an electrode connection portion, heating for ohmic contact is performed at a high temperature, as described in each of the above embodiments. This is particularly effective in cases where it is not preferable to do so.

[0055]

As described above, according to the ohmic electrode of the present invention, since the ohmic contact layer made of the composite containing palladium, germanium and gold is provided, the heating for the ohmic contact is performed at a low temperature. Good ohmic contact with the electrode connection portion can be obtained even if it is performed. That is, even when heating cannot be performed at a high temperature, there is an effect that a good ohmic contact can be easily obtained. The provision of the contact electrode layer can improve the adhesion to the wiring, and the provision of the diffusion prevention layer can prevent the diffusion of the ohmic contact layer.

According to the method for forming an ohmic electrode of the present invention, the first metal layer made of palladium and the second metal layer made of at least germanium of germanium and gold are sequentially laminated and then heated. Therefore, the effect that the ohmic electrode of the present invention can be realized can be obtained.

Further, according to the laminate for an ohmic electrode of the present invention, a first metal layer made of palladium and a second metal layer made of at least germanium of germanium and gold are provided in order. Therefore, a good ohmic electrode can be obtained even when heated at a low temperature. That is, even when heating cannot be performed at a high temperature, there is an effect that a good ohmic contact can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an n-side electrode that is an ohmic electrode according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a sample used in an experiment for examining characteristics of the ohmic electrode shown in FIG.

FIG. 3 is a characteristic diagram showing a relationship between current and voltage when heated at 170 ° C.

FIG. 4 is a characteristic diagram showing a relationship between current and voltage when heated at 180 ° C.

FIG. 5 is a cross-sectional view illustrating a configuration of an n-side electrode that is an ohmic electrode according to a second embodiment of the present invention.

FIG. 6 is a characteristic diagram showing a relationship between current and voltage when heated at 170 ° C.

FIG. 7 is a characteristic diagram showing a relationship between current and voltage when heated at 180 ° C.

FIG. 8 is a cross-sectional view illustrating a configuration of an n-side electrode that is an ohmic electrode according to a third embodiment of the present invention.

FIG. 9 is a sectional view illustrating a modification of the ohmic electrode shown in FIG.

[Explanation of symbols]

10 n-side electrode (ohmic electrode), 11 ohmic contact layer, 11a, 11α first metal layer, 11b, 11
β: second metal layer, 12: diffusion preventing layer, 12a: titanium layer, 12b: platinum layer, 13: contact electrode layer, 20:
Substrate, 21 ... buffer layer, 22 ... n-type clad layer, 23
... first guide layer, 24 ... active layer, 25 ... second guide layer, 26 ... p-type clad layer, 27 ... contact layer, 28
... superlattice layer, 29 ... insulating layer, 30 ... p-side electrode

Claims (30)

[Claims] An ohmic connected to an electrode connecting portion formed of a semiconductor containing at least gallium of a group III element gallium (Ga) and indium (In) and a group V element arsenic (As). An ohmic electrode, comprising: an ohmic contact layer comprising a composite containing at least palladium and germanium selected from the group consisting of palladium (Pd), germanium (Ge), and gold (Au). 2. The composite in which the ohmic contact layer has at least a first metal layer containing palladium and a second metal layer containing at least germanium of germanium and gold in order from the side of the electrode connection part. 2. The ohmic electrode according to claim 1, wherein the ohmic electrode is formed of a body. 3. The ohmic contact layer is formed by sequentially laminating a first metal layer made of palladium and a second metal layer made of at least germanium of germanium and gold from the side of the electrode connection part. The ohmic electrode according to claim 1, wherein the ohmic electrode is constituted by a composite obtained by heating. 4. The method according to claim 1, wherein the ohmic contact layer comprises a composite obtained by heating the first metal layer and the second metal layer at a temperature of 175 ° C. or higher. The ohmic electrode according to claim 3. 5. The method according to claim 1, wherein the ohmic contact layer is formed of a composite obtained by heating the first metal layer and the second metal layer at a temperature within a range of 250 ° C. or less. The ohmic electrode according to claim 3, wherein: 6. The ohmic electrode according to claim 1, further comprising a contact electrode layer for connecting a wiring on a side of said ohmic contact layer opposite to said electrode connection layer. 7. The ohmic electrode according to claim 6, wherein said contact electrode layer is made of gold (Au). 8. The ohmic electrode according to claim 6, further comprising a diffusion preventing layer for preventing diffusion of the ohmic contact layer between the ohmic contact layer and the contact electrode layer. 9. The ohmic electrode according to claim 8, wherein the diffusion preventing layer has a titanium layer made of titanium (Ti). 10. The anti-diffusion layer further comprises platinum (P
10. The method according to claim 9, further comprising a platinum layer comprising t).
The ohmic electrode as described. 11. The ohmic electrode according to claim 1, wherein the ohmic electrode is connected to an electrode connecting portion formed of an n-type semiconductor. 12. The ohmic electrode according to claim 1, wherein the ohmic electrode is connected to an electrode connecting portion composed of a substrate on which a group II-VI compound semiconductor layer is laminated. 13. At least gallium of group III elements gallium (Ga) and indium (In) and V
A method for forming an ohmic electrode on an electrode connecting portion formed of a semiconductor containing arsenic (As) of a group III element, comprising: a first metal layer made of palladium (Pd); germanium (Ge) and gold A laminating step of sequentially laminating at least a second metal layer of (Au) made of germanium from the side of the electrode connecting portion, and a heating step of heating the laminated first metal layer and the second metal layer And a method for forming an ohmic electrode. 14. The method according to claim 13, wherein the heating is performed at a temperature of 175 ° C. or higher. 15. The method for forming an ohmic electrode according to claim 13, wherein in the heating step, heating is performed at a temperature of 250 ° C. or less. 16. After laminating the first metal layer and the second metal layer, a contact electrode layer for connecting a wiring is laminated on a side of the second metal layer opposite to the first metal layer. 14. The method for forming an ohmic electrode according to claim 13, comprising a step of forming a contact electrode layer. 17. The method according to claim 17, wherein:
17. The method for forming an ohmic electrode according to claim 16, wherein a contact electrode layer made of gold (Au) is laminated. 18. The method according to claim 1, further comprising: stacking the first metal layer and the second metal layer and forming a second metal layer before forming a contact electrode layer.
17. The method for forming an ohmic electrode according to claim 16, further comprising a step of forming a diffusion prevention layer for laminating a diffusion prevention layer for preventing diffusion of the metal layer between the second metal layer and the contact electrode layer. 19. The method for forming an ohmic electrode according to claim 18, wherein in the step of forming a diffusion prevention layer, a titanium layer made of titanium (Ti) is laminated as the diffusion prevention layer. 20. In the diffusion preventing layer forming step, a titanium layer made of titanium (Ti) and platinum (P) are used as the diffusion preventing layer.
19. The method for forming an ohmic electrode according to claim 18, wherein a platinum layer made of t) is laminated. 21. The method for forming an ohmic electrode according to claim 13, wherein an ohmic electrode is formed on an electrode connecting portion made of an n-type semiconductor. 22. The method for forming an ohmic electrode according to claim 13, wherein an ohmic electrode is formed on an electrode connecting portion composed of a substrate on which a group II-VI compound semiconductor layer is laminated. 23. At least gallium and gallium of group III elements gallium (Ga) and indium (In)
A stacked body for forming an ohmic electrode with respect to an electrode connecting portion made of a semiconductor containing arsenic (As) of a group III element, comprising a first metal layer made of palladium (Pd), germanium (Ge) A laminate for an ohmic electrode, comprising: a second metal layer of at least germanium of gold (Au), which is provided in order from the side of the electrode connection portion. 24. The ohmic electrode according to claim 23, further comprising a contact electrode layer for connecting a wiring on a side of the second metal layer opposite to the first metal layer. Laminate. 25. The contact electrode layer is made of gold (Au).
The laminate for an ohmic electrode according to claim 24, wherein the laminate comprises: 26. The ohmic according to claim 24, further comprising a diffusion preventing layer for preventing diffusion of the second metal layer, between the second metal layer and the contact electrode layer. Laminate for electrodes. 27. The laminate for an ohmic electrode according to claim 26, wherein the diffusion preventing layer has a titanium layer made of titanium (Ti). 28. The diffusion prevention layer further comprises platinum (P
3. The method according to claim 2, further comprising a platinum layer comprising t).
8. The laminate for an ohmic electrode according to 7. 29. A semiconductor forming the electrode connection portion,
The laminate for an ohmic electrode according to claim 23, wherein the laminate is an n-type semiconductor. 30. The laminate for an ohmic electrode according to claim 23, wherein the laminate is formed for an electrode connection portion composed of a substrate on which a group II-VI compound semiconductor layer is laminated.