JP2000124501A - Light-emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting diode of a structure, wherein the diode has an active layer and clad layers and the deterioration of the diode at the time when light is radiated by an emission recombination generated in the active layer is reduced. SOLUTION: This light-emitting diode is a light-emitting diode of a structure, wherein the diode has a first conductivity type first clad layer, an active layer and a second conductivity type second clad layer, a first electrode is connected with the first clad layer, a second electrode is connected with the second clad layer and light is radiated by an emission recombination generated in the active layer when a voltage is applied to the first and second electrodes and a current is injected in the first and second electrodes, and a current injection structure from the second electrode 24 is formed into a constitution, wherein the current injection structure is divided into a plurality of pieces by a current non-injection region 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode, and more particularly, to a light emitting diode comprising a II-VI compound semiconductor.

[0002]

2. Description of the Related Art A light emitting diode is a diode utilizing light emission by radiative recombination of minority carriers injected by applying an electric field to a pn junction, and is widely used as one of semiconductor light emitting devices.

A group II element composed of a group II element such as Zn, Cd, Mg and Be and a group VI element such as O, S, Se and Te
Group VI compound semiconductors are promising as materials for forming semiconductor light emitting devices such as semiconductor lasers and light emitting diodes. In particular, it is known that ZnMgSSe mixed crystal is capable of crystal growth on a GaAs substrate and is suitable for, for example, a guide layer or a clad layer constituting a blue semiconductor laser.

FIG. 10 is a sectional view showing a configuration example of a conventional light emitting diode. Here, a case where a light emitting diode is formed using a ZnMgSSe-based material is shown.

[0005] As shown in FIG. 10, this light emitting diode comprises an n-type GaAs:
Si first buffer layer 11, n-type ZnSe: Cl second buffer layer 12, n-type ZnSSe: Cl third buffer layer 1
3, n-type ZnMgSSe: Cl first cladding layer 14, n
Type ZnSSe: Cl first guide layer 15, ZnCdSe active layer 16, p-type ZnSSe: N second guide layer 17, p-type ZnMgSSe second main cladding layer 18, p-type ZnSS
e: N second sub-cladding layer 19, p-type ZnSe: N intermediate layer 20, p-type (ZnSe: N / ZnTe: N) superlattice semiconductor layer (SL) 21, p-type ZnTe: N contact layer 22
Are sequentially laminated. Then, in a layer above the upper layer portion of the p-type ZnSSe: N second sub-cladding layer 19,
The region partitioned by the insulating film 23 is a contact region, and is in contact with a p-type electrode 24 such as a Pd / Pt / Au electrode. On the other hand, n-type GaAs: Si substrate 10
An n-type electrode 26 such as an In electrode is formed on the back side of the substrate.

[0006] The light emitting diode shown in FIG.
A voltage is applied to the mold electrode 24 and the n-type electrode 26 to inject minority carriers, and light emitted by radiative recombination in the active layer can be extracted from, for example, the surface on which the p-type electrode 24 is formed. Here, the p-type electrode 24 is formed on the entire surface by covering the upper layer of the p-type ZnTe: N contact layer 22 and the upper layer of the insulating film 23, and the region partitioned by the insulating film 23 is entirely formed on the p-type electrode 26. The structure is such that a current is injected from the device.

[0007]

However, the light emitting diode having the above structure has a problem that the deterioration rate of the element is large. In the above-mentioned light emitting diode, ZnCdSe constituting the active layer 16 is a strain-based material. Therefore, when the amount of strain is increased, the band gap difference with the guide layer is increased, but the characteristics are deteriorated due to the influence of the strain. for that reason,
The ZnCdSe active layer 16 has a composition of about 25% Cd and a thickness of about 4 nm so that the emission wavelength is 50%.
It is desirable to set it to about 0 nm. At this time, if an attempt is made to increase the emission wavelength, the amount of distortion increases.

FIG. 11 is a graph showing a degradation rate τ _1/2 measured at an emission temperature of 60 ° C. and an injection current of 100 mA.
FIG. 6 is a diagram plotting (light emission time of a light emitting diode until the light emission amount becomes １ ／) with respect to an emission wavelength. As described above, the deterioration rate of the light emitting diode having the above-described structure increases as the emission wavelength increases.

As a cause of the deterioration of the light emitting diode, a linear dark line is generated in the surface of the active layer starting from stacking faults in the active layer and the like, and the dark line expands and widens with time. The dark line extended to the above becomes a starting point of another dark line, a new dark line is generated, and the phenomenon that the entire light emitting region becomes dark and the amount of light emission decreases is clarified. FIG. 12 is a schematic diagram for explaining this state. In FIG. 12A, the entire region of the p-type electrode 24 formed on the entire surface is a light emitting region. Here, a dark line Z is generated starting from a stacking fault Za or the like. As shown in FIG. 12B, these dark lines Z are extended and thickened with time, and the extended dark line becomes a starting point of another dark line to generate a new dark line. It is getting darker.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an active layer having an n-type and a p-type cladding layers formed on both sides of the active layer. It is an object of the present invention to provide a light emitting diode which emits light by radiative recombination occurring in the above, and which suppresses the extension of a dark line, which is a cause of deterioration, and reduces the deterioration.

[0011]

In order to achieve the above object, a light emitting diode of the present invention comprises a first cladding layer of a first conductivity type, an active layer, and a second cladding layer of a second conductivity type. A first electrode is connected to the first cladding layer, and a second electrode is connected to the second cladding layer.
A light emitting diode that emits light by radiative recombination generated in the active layer when a voltage is applied to an electrode and a second electrode to inject a current, wherein a current injection structure from the second electrode includes a current non-injection structure. It is divided into a plurality of areas.

In the light emitting diode of the present invention, the structure for injecting current from the second electrode is divided into a plurality of regions by the non-current injection region. Of the light emitting diode can be reduced, and the deterioration of the light emitting diode can be reduced.

[0013] In the light emitting diode according to the present invention, preferably, the current injection structure is formed by the current non-injection region.
It is divided by a width of 0 μm or more. The extension of the dark line generated in the active layer to the current non-injection region is about 10 μm,
By dividing the current injection structure with a width of 10 μm or more by the current non-injection region, the extension of the dark line can be effectively suppressed.

Preferably, in the light emitting diode according to the present invention, the current injection structure is divided by an insulating film. Alternatively, preferably, the current injection structure is divided by a region into which an impurity for inactivating carriers is introduced. Thereby, a current non-injection region that suppresses the extension of the dark line can be provided. The second cladding layer is composed of a laminate of two or more layers, and at least the second cladding layer on the second electrode side is divided by an insulating film, or at least the second cladding layer on the second electrode side The structure described above can be obtained by a structure in which an impurity for inactivating carriers is introduced.

Further, in the light emitting diode of the present invention, preferably, the first cladding layer, the active layer and the second cladding layer each include at least one of Be, Zn, Hg, Cd, and Mg. Elements and O, S, Se, Te
II-V containing at least one element of
It is formed of a group I compound semiconductor. For example, ZnC
According to the present invention, it is possible to suppress the extension of a dark line that causes deterioration even in a light emitting diode including a strain-based semiconductor layer such as dSe.

In the light emitting diode according to the present invention, preferably, the current injection structure is formed by the current non-injection region.
It is divided into regions having an area of 3 × 10 ⁴ μm ² or less, and more preferably, is divided into regions having an area of 1 × 10 ⁴ μm ² or less. Stacking faults in the crystal can be suppressed to about 1 × 10 ³ / cm ⁻² . This will have one defect per 1 × 10 ⁵ μm ² . Therefore, by dividing each region having an area of 3 × 10 ⁴ μm ² or less, the probability that the starting point of a dark line such as a stacking fault in the active layer in each region becomes 1
/ 3 or less, and the remaining 2/3 region does not include the starting point of the dark line and can confine the dark line in a region corresponding to 1/3 of the entire region. Therefore, it is possible to effectively suppress the extension of the dark line. Can be. By dividing each region having an area of 1 × 10 ⁴ μm ² or less, the probability that the starting point of a dark line such as a stacking fault in the active layer in each region is 1/1.
0 or less, and the extension of the dark line can be more effectively suppressed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a plan view showing a first embodiment of a light emitting diode according to the present invention, and FIG. 2 is a sectional view taken along line XX 'of FIG. The light emitting diode of the present embodiment is made of ZnMgS
It is made of Se-based material.

As shown in FIG. 2, this light emitting diode has, for example, the following structure. On a substrate 10 made of n-type GaAs: Si or the like, a first buffer layer 11 made of n-type GaAs: Si or the like, a second buffer layer 12 made of n-type ZnSe: Cl or the like having a thickness of about 10 nm, and n-type Zn
Third buffer layer 13 made of SSe: Cl or the like (this layer can be omitted), Zn _0.88 Mg _0.12 S _0.18 S
e _0.82 : first clad layer 14 of n-type ZnMgSSe: Cl or the like and having a film thickness of about 1 μm, ZnS _0.06
A first guide layer 15 made of n-type ZnSSe: Cl or the like having a thickness of about 100 nm, such as Se _0.94 : Cl, and ZnCd;
An active layer 16 made of Se or the like and having a thickness of about 3 to 4 nm, Z
a second guide layer 17 made of p-type ZnSSe: N or the like, such as nS _0.06 Se _0.94 : N;
_0.75 Mg _0.25 S _0.28 Se _0.72 : p-type ZnMgS such as N
A second main cladding layer 18 of Se: N or the like having a thickness of about 1 μm, a second sub-cladding layer 19 of p-type ZnSSe: N or the like having a thickness of about 2 μm, or a film thickness of 150 nm of p-type ZnSe: N or the like. Intermediate layer 20, p-type ZnS
A superlattice semiconductor layer (SL) 21, which is a layer in which e: N and ZnTe: N are alternately laminated, and a contact layer 22 made of p-type ZnTe: N or the like are sequentially laminated.

In the layer above the upper part of the second sub-cladding layer 19, the region divided and divided by the insulating film 23 becomes a contact region, and
A contact is made with a transparent p-type electrode 24 made of Au or the like having a thickness of about nm. Further, a pad electrode 25 is formed in an upper layer portion of the insulating film 23 which is connected to the p-type electrode 24 and is made of, for example, the same conductive material as the p-type electrode 24 with a thickness of about 200 nm. Between Au and the insulating film 23,
Ti or Pd may be formed. On the other hand, n-type GaAs
s: On the back side of the Si substrate 10, an n-type electrode 26 such as an In electrode is formed.

In the light emitting diode shown in FIGS. 1 and 2, a voltage is applied to the p-type electrode 24 and the n-type electrode 26 to inject minority carriers, and light emitted by radiative recombination in the active layer is, for example, p-type. It can be taken out from the surface on which the mold electrode 24 is formed. Here, the p-type electrode 24 is divided by the region of the insulating film 23 (and the region of the pad electrode 25 formed thereon), for example, as shown in FIG.
Thereby, the region of the insulating film 23 becomes a current non-injection region,
The structure for injecting current from the p-type electrode 24 is divided into a plurality of regions by the non-current injection region. In the drawing, the current injection structure is divided into regions each having an area of about 250 μm × 100 μm with a width of 10 μm or more (corresponding to the width of the insulating film) by a current non-injection region. The width at which the current injection structure is divided by the current non-injection region may be 10 μm or more, and preferably 20 μm or more.

The defect serving as the starting point of the dark line is 1 mm ² (1 mm × 1 mm) in terms of the area of the light emitting region other than the end of the chip.
Since the number of stacking faults per area can be reduced, the dark line expands and darkens in the area where these starting points are included, but in areas where there are no initial defects, the area from the other areas is particularly large. Since there is almost no dark line propagation, deterioration is extremely unlikely to occur. Since the current injection structure is divided into a plurality of regions by the current non-injection region, the extension of the dark line generated in the active layer, which is the cause of the deterioration of the light emitting diode, is suppressed. Can be reduced.

The manufacture of the light emitting diode having the above structure is performed by a well-known general method. The outline of the manufacturing method will be briefly described below.

FIG. 3 is a schematic diagram showing the configuration of a molecular beam epitaxial crystal growth apparatus. A substrate holder 2 is provided in a vacuum chamber 1, and an rf cell 4 and a molecular beam source (K cell) 5 are arranged so as to face the surface thereof. The GaAs: Si substrate 3 is fixed to the substrate holder 2, the inside of the vacuum chamber 1 is evacuated to a high vacuum state, and the surface of the substrate 3 is irradiated with the molecular beam MB from the molecular beam source 5. As a result, the layers from the first buffer layer 11 to the contact layer 22 are sequentially grown on the substrate 3. rf cell 4
Is used when nitrogen is used as a raw material. Next, FIG.
After forming a resist pattern on the contact layer 22 so as to obtain the electrode pattern shown in FIG. 1, the contact layer 22, the superlattice semiconductor layer 21, and the like are formed by a wet etching method or a dry etching method using this resist pattern as an etching mask. The intermediate layer 20 and the second sub-cladding layer 19 are etched to a predetermined depth in the thickness direction of the second sub-cladding layer 19.

Next, using a resist pattern used as an etching mask as a growth mask, an insulator such as silicon oxide is deposited, and a lift-off process is performed to obtain a region corresponding to the gap of the electrode pattern shown in FIG. Then, an insulating film 23 is formed. Next, an electrode material such as Au is deposited on the entire surface to a thickness of about 10 nm so as to be connected to the contact layer 22 to form a transparent p-type electrode 24. Further, a pad electrode 25 is formed by forming an electrode material in a thickness of about 200 nm on an upper layer portion of the insulating film 23. On the other hand, an electrode material such as In is also formed on the back surface of the GaAs: Si substrate 3 to form an n-type electrode 26. Thus, the light emitting diode shown in FIGS. 1 and 2 can be formed.

(Example 1) In the light emitting diode of this embodiment, when the p-type electrode 24 has a shape of a p-type electrode 24 having a width W _E , a dark line that causes deterioration is formed at the end of the p-type electrode 24. FIG. 4 shows the result of observing the state in which the film extends from the region to the insulating film 23 region. The dark line Z spreads from the end of the p-type electrode 24 to the region of the insulating film 23, but its width _WZ was about 10 μm, and did not extend to a region further than that.

Example 2 In the light emitting diode of the present embodiment, when the shape of the p-type electrode 24 is changed to the shape shown in FIG. It is shown in FIG. The dark line Z is the p-type electrode 2 on the left side of the drawing.
4a, but does not propagate to the p-type electrode region 24b on the right side of the drawing, and has a width W _I (here, 5
By providing the insulating film 23 (0 μm), the extension of the dark line Z could be suppressed.

Example 3 In a light emitting diode having a light emitting region of 1 mm × 1 mm, a light emitting diode (D1) having an electrode over the entire light emitting region and a light emitting device in which a p-type electrode is divided by an insulating film in the pattern shown in FIG. Diode (D
2) was created. FIG. 6 shows each diode (D1, D
FIG. 2 is a diagram plotting the change over time of the relative light output when ² ) was caused to emit light at a temperature of 60 ° C. and an injection current of 100 mA (20 Acm ⁻² ). Thus, it was confirmed that the deterioration can be suppressed by dividing the p-type electrode by the insulating film in the pattern shown in FIG.

Second Embodiment The light emitting diode of this embodiment is substantially the same as the light emitting diode of the first embodiment, except that the pattern of the p-type electrode 24 and the insulating film 23 corresponding to the gap between the pattern (and the The pattern of the pad electrode 25) formed in the upper layer is shown in FIG.
The only difference is that they are formed in the patterns shown in (a) and (b). The pattern shown in FIG. 7 is a pattern in which an electrode region having an area of 30 μm × 80 μm is repeatedly formed with an insulating film region having a width of 20 μm. The pattern in FIG. 7A is an enlarged view of a portion corresponding to the region A in FIG. 7B, and the pattern in FIG. 7B can be obtained by repeating this pattern.

In the above light emitting diode, there is a stacking fault in any of the regions divided by the insulating film,
Even if the region is darkened, deterioration is extremely unlikely to occur in a region where there is no initial defect, since there is almost no propagation of dark lines from other regions. Since the current injection structure is divided into a plurality of regions by the current non-injection region as described above, the extension of the dark line generated in the active layer, which causes the deterioration of the light emitting diode, is suppressed. Can be reduced. In particular, 30 μm × 80 μm smaller than the first embodiment.
m, and the probability that an initial defect exists in each region is further reduced.
Deterioration can be reduced as compared with the embodiment.

FIG. 8 shows the pattern of the p-type electrode 24 and the pattern of the insulating film 23 (and the pad electrode 25 formed thereon) corresponding to the gap therebetween.
A pattern in which an electrode region having an area of 30 μm × 30 μm as shown in (a) is repeatedly formed with an insulating film region having a width of 20 μm, and a pattern of 60 μm × 6 as shown in FIG.
FIG. 8 shows a pattern in which an electrode region having an area of 0 μm is repeatedly formed with an insulating film region having a width of 40 μm.
A pattern in which an electrode region having an area of 70 μm × 90 μm as shown in (c) is repeatedly formed with an insulating film region having a width of 10 to 30 μm or the like can be used.

Third Embodiment The light emitting diode of the present embodiment is substantially the same as the light emitting diode of the first embodiment, except that the current non-injection region dividing the current injection structure has impurities for inactivating carriers. Region 23a into which, for example, oxygen ions have been implanted.
The only difference is that

In the light emitting diode of the present embodiment, after stacking up to the contact layer 22 in the same manner as in the first embodiment, a resist film is formed by patterning in the p-type electrode formation region, and oxygen ions are implanted. A carrier passivation region 23a is formed, and then, as in the first embodiment, p
It can be manufactured by forming the mold electrode 24, the pad electrode 25, and the n-type electrode 26.

In the light emitting diode according to this embodiment, similarly to the first embodiment, the current injection structure is divided into a plurality of regions by the current non-injection region, so that the active element causing deterioration of the light emitting diode is reduced. Since the extension of the dark line generated in the layer is suppressed, deterioration of the light emitting diode can be reduced.

As the pattern of the p-type electrode of the light emitting diode according to the present embodiment, it is preferable to form the same pattern as that of the second embodiment.

The present invention is not limited to the above embodiment.
For example, in the embodiment, a light-emitting diode of a II-VI group compound semiconductor (ZnMgSSe-based) is described. However, the present invention can be applied to various semiconductor light-emitting elements, and a part in which a light-emitting region is deteriorated. When the reaction occurs in a chain, large effects can be obtained by using the present invention. The light-emitting materials include nitride, AlGaAs, AlInGaP,
The present invention can be applied to various light emitting diodes such as III-V group compound semiconductors such as lGaAsP, and organic EL devices. Further, instead of the p-type electrode, the n-type electrode can be divided by an insulating film or the like. In addition, various changes can be made without departing from the gist of the present invention.

[0036]

As described above, according to the present invention,
A light emitting diode having n-type and p-type cladding layers formed on both sides of an active layer and connected to both sides of the active layer, and emitting light by radiative recombination occurring in the active layer. It is possible to provide a light emitting diode in which the deterioration of the light emitting diode is suppressed by suppressing the stretching of the light emitting diode.

[Brief description of the drawings]

FIG. 1 is a plan view showing a pattern of a p-type electrode of a light emitting diode according to a first embodiment.

FIG. 2 is a cross-sectional view of the light emitting diode according to the first embodiment, taken along line XX ′ in FIG. 1;

FIG. 3 is a schematic diagram showing a configuration of a molecular beam epitaxial crystal growth apparatus.

FIG. 4 is a schematic diagram illustrating a result of observing a state of extending a dark line according to the first embodiment.

FIG. 5 is a schematic diagram showing a result of observing a state of extending a dark line according to Example 2.

FIG. 6 is a diagram comparing the time change of the light output of the light emitting diode of the present invention and the light emitting diode of the comparative example in Example 3;

FIG. 7 is a plan view showing a pattern of a p-type electrode of the light emitting diode according to the second embodiment.

FIG. 8 is a plan view showing a pattern of a p-type electrode of the light emitting diode according to the second embodiment.

FIG. 9 is a sectional view of the light emitting diode according to the third embodiment taken along line XX ′ in FIG. 1;

FIG. 10 is a sectional view of a light emitting diode according to a conventional example.

FIG. 11 is a diagram in which a deterioration rate (τ _1/2 ) of a light emitting diode according to a conventional example is plotted with respect to an emission wavelength.

FIG. 12 is a schematic diagram showing a result of observing a state of deterioration of a light emitting diode according to a conventional example, and changes from (a) to (b).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Substrate holder, 3 ... Substrate, 4 ...
rf cell, 5: molecular beam source, 10: substrate, 11: first buffer layer, 12: second buffer layer, 13: third buffer layer, 14: first cladding layer, 15: first guide layer, 16
... active layer, 17 ... second guide layer, 18 ... second main clad layer, 19 ... second sub clad layer, 20 ... intermediate layer, 21 ... superlattice semiconductor layer (SL), 22 ... contact layer, 23 ... insulation Film, 23a: region into which impurities for inactivating carriers are introduced, 24: p-type electrode, 25: pad electrode, 26 ...
n-type electrode, MB: molecular beam, Z: dark line, Za: starting point of dark line.

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Claims (9)

[Claims] A first conductive type first clad layer, an active layer, and a second conductive type second clad layer; a first electrode connected to the first clad layer; A light emitting diode, wherein a second electrode is connected to the cladding layer, and emits light by radiative recombination occurring in the active layer when a voltage is applied to the first electrode and the second electrode to inject a current. A light emitting diode in which a current injection structure from the second electrode is divided into a plurality by a current non-injection region; 2. The light emitting diode according to claim 1, wherein the current injection structure is divided by the current non-injection region into a width of 10 μm or more. 3. The light emitting diode according to claim 1, wherein said current injection structure is divided by an insulating film. 4. The light emitting diode according to claim 1, wherein said current injection structure is divided by a region into which impurities for inactivating carriers are introduced. 5. The light emitting diode according to claim 1, wherein said second clad layer is formed of a laminate of two or more layers, and at least the second clad layer on the second electrode side is divided by an insulating film. 6. The carrier according to claim 1, wherein the second clad layer is formed of a laminate of two or more layers, and at least an impurity for inactivating carriers is introduced into the second clad layer on the second electrode side. Light emitting diode. 7. The first clad layer, the active layer, and the second clad layer are each made of Be, Zn, Hg, C
d, at least one or more of Mg and O, S,
The light emitting diode according to claim 1, wherein the light emitting diode is formed of a II-VI compound semiconductor containing at least one element of Se and Te. 8. The light emitting diode according to claim 1, wherein said current injection structure is divided into regions having an area of 3 × 10 ⁴ μm ² or less by said current non-injection region. 9. The light emitting diode according to claim 8, wherein the current injection structure is divided by the current non-injection region into regions each having an area of 1 × 10 ⁴ μm ² or less.