DE112015003919T5 - Semiconductor light emitting device - Google Patents

Abstract

According to the present invention, there is provided a semiconductor light emitting device having a quantum well active layer composed of well layers and barrier layers, wherein the semiconductor light emitting device has a light emission wavelength of 585 nm or more and 605 nm or less, the well layer is made of a compound semiconductor having a composition formula of (Alx Ga1-x) y In1-y P (0 <x≤0.06, 0 <y <1), and the barrier layer is made of a compound semiconductor having a composition formula of (AlmGa1-m) nIn1- nP (0 ≦ m ≦ 1, 0 <n <1). Thereby, it is possible to provide a semiconductor light emitting device capable of providing a higher light emitting efficiency in a region of shorter wavelengths (yellow emission) while using an active layer having a quantum well structure.

Description

TECHNICAL AREA

The present invention relates to a semiconductor light emitting device using a compound semiconductor material.

STATE OF THE ART

Of the III-V compound semiconductors except nitrides, an AlGaInP-based material has the largest direct-transition-band gap; this material is used for a light emitting device having a band of 500 to 600 nm. In particular, a light-emitting device having an AlGaInP light-emitting part whose lattice constant matches a GaAs substrate can achieve emissions with a brightness greater than the previous indirect-band-transition materials such as GaP and GaAsP.

However, in such a light-emitting device having an AlGaInP light-emitting part, the light emission efficiency is not necessarily sufficient in a region of shorter wavelengths (yellow emission).

It is considered that the reasons for the decrease of the light emission efficiency in a shorter wavelength region are to be that (1) the carrier confinement becomes insufficient because the band gap between the active layer and the clad layer becomes small, (2) not luminescent centers in the active layer increase as the Al content of the composition of the active layer increases; (3) the structure of the energy band changes from the direct transition type to the indirect transition type, etc.

To solve these problems, Patent Document 1 discloses a method in which the active layer is arranged to be a quantum well structure having 80 to 200 layers, and the Al content of the composition of the barrier layer is set to be more than 1 / 2 (that is, a compound semiconductor having a composition formula of (Al _x Ga _1-x ) _1-y In _y P (0.5 <x ≦ 1) is used), thereby suppressing carrier overflow to obtain a high light-emitting efficiency ,

Patent Document 2 discloses a method in which the active layer is arranged to be a quantum well structure in which a lattice distortion is introduced into the active layer (ie, a quantum well structure consisting of strain-strain or strain-strain well layers and barrier layers having distortion that of the well layers is opposite, such as a distortion relaxation layer), whereby the Al content of the composition of the active layer is reduced, so that a high light emission efficiency is obtained.

CITING

Patent Literature

• Patent Document 1: Publication of the Unexamined Japanese Patent Application (Kokai) No. 2008-192,790
• Patent Document 2: Publication of Unexamined Japanese Patent Application (Kokai) No. H08-088404

BRIEF SUMMARY OF THE INVENTION

BACKGROUND OF THE INVENTION TECHNICAL TASK

As described above, in order to suppress a decrease in light emission efficiency in a region of shorter wavelengths, the methods disclosed in Patent Document 1 and Patent Document 2 have been proposed.

In the method disclosed in Patent Document 1, although the carrier overflow can be suppressed, the Al content of the composition of the active layer increases, whereby the light emission efficiency decreases.

The method disclosed in Patent Document 2 results in an increase in lattice defects in the crystal due to the distortion even when the distortion relaxation layer is used, and therefore a higher light emitting efficiency can not necessarily be achieved.

The present invention has been made to solve the problems described above. It is an object of the present invention to provide a semiconductor light emitting device in which a high light emission efficiency can be achieved in a region of shorter wavelengths (yellow emission) while an active layer having a quantum well structure is used.

MTTTEL TO SOLVE THE TASK

To achieve the object, the present invention provides a semiconductor light emitting device having an active quantum well layer (quantum well layer) consisting of well layers and barrier layers, wherein
the semiconductor light emitting device has a light emission wavelength of 585 nm or more and 605 nm or less,
the well layer is made of a compound semiconductor having a composition formula of (Al _x Ga _1-x ) _y In _1-y P (0 <x ≦ 0.06, 0 <y <1), and
the barrier layer is made of a compound semiconductor having a composition formula of (Al _m Ga _1-m ) _n In _1-n P (0 ≦ m ≦ 1, 0 <n <1).

By a constitution such that a well layer of an AlGaInP-based compound semiconductor constituting the quantum well active layer has an Al content of 0.06 or less, the average Al content of the composition of the quantum well active layer can be reduced whereby the non-luminescent centers in the quantum well active layer can disappear, and thereby high light emission efficiency can be achieved in a region of shorter wavelengths (yellow emission).

The active quantum well layer preferably has a total film thickness of 200 nm or more and 300 nm or less.

When the total film thickness of the quantum well active layer is 200 nm or more, it is possible to suppress a decrease in light emission efficiency due to carrier overflow. When the total film thickness of the quantum well active layer is 300 nm or less, it is possible to avoid an increase in cost due to a longer manufacturing time and higher material cost.

EFFECTS OF THE INVENTION

According to the semiconductor light emitting device of the present invention, as described above, in a region of shorter wavelengths (yellow emission), high light emission efficiency can be achieved while using an active layer having a quantum well structure.

BRIEF DESCRIPTION OF THE DRAWING

1 Fig. 12 is a schematic sectional view showing an embodiment of the semiconductor light-emitting device of the present invention;

2 Fig. 11 is a diagram showing, on the basis of sectional views, a manufacturing process used in manufacturing the semiconductor light emitting device of the present invention;

3 Fig. 15 is a graph showing the relationship between the total film thickness of an active quantum well layer and the light emission efficiency; and

4 Fig. 12 is a graph showing the relationship between the light emission wavelength and the light emission efficiency for an example and a comparative example.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail with reference to the drawings by way of an embodiment, but the present invention is not limited thereto.

As described above, several methods have been proposed which use an active layer having a quantum well structure to suppress a decrease in the light emitting efficiency of a semiconductor light emitting device in a shorter wavelength region. However, each of these methods requires improvements in order to obtain high light emission efficiency in a region of shorter wavelengths (yellow emission).

Therefore, the inventors have been actively engaged in a semiconductor light emitting device in which a high light emission efficiency can be obtained in a region of shorter wavelengths (yellow emission) while an active layer having a quantum well structure is used.

As a result, the inventors have found that the structure in which a well layer of an AlGaInP-based compound semiconductor constituting the quantum well active layer has an Al content of 0.06 or less enables the average Al content of the .alpha To reduce the composition of the active quantum well layer, whereby the non-luminescent centers in the active quantum well layer can disappear, and thereby in a range of shorter wavelengths (yellow emission) high light emission efficiency can be obtained, whereby the present invention has been completed.

First, an embodiment of the semiconductor light emitting device of the present invention will be described with reference to FIG 1 described.

This in 1 shown semiconductor light emitting device according to the invention 10 has a light-emitting part 19 with an active quantum well layer 14 on. In the active quantum well layer 14 are pot layers 16 and barrier layers 15 alternately piled up. The pot layer 16 is made of i-AlGaInP having a compositional formula of (Al _x Ga _1-x ) _y In _1-y P (0 <x ≦ 0.06, 0 <y <1), and the barrier layer 15 is composed of i-AlGaInP having a compositional formula of (Al _m Ga _1-m ) _n In _1-n P (0 ≦ m ≦ 1, 0 <n <1). The light emission wavelength of the semiconductor light emitting device 10 is 585 nm or more and 605 nm or less. The desired wavelength in the aforementioned range can be, for example, by changing the film thickness of the well layer 16 the active quantum well layer 14 be achieved.

In the light emitting part 19 it is a semiconductor layer, for example, from a current spreading layer 12 a first conductivity type, a coating layer 13 of the first conductivity type, an active quantum well layer 14 a coating layer 17 a second conductivity type and a current spreading layer 18 of the second conductivity type. The current spreading layer 12 of the first conductivity type, the overcoat layer 13 of the first conductivity type, the overcoat layer 17 of the second conductivity type and the current spreading layer 18 of the second conductivity type are, for example, a p-type AlGaInP layer having a composition formula of (Al _x Ga _1-x ) _y In _1-y P (0≤x≤1, 0 <y <1), a p-type AlGaInP layer a compositional formula of (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 <y <1), an n-AlGaInP layer having a composition formula of (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 <y <1) or an n-GaP layer.

On the light emitting part 19 For example, on a p-type side, there are first thin ohmic electrodes 11 and terminal electrodes (not shown).

Further, the semiconductor light emitting device has 10 for example, a conductive carrier substrate 24 , one on the conductive support substrate 24 provided metallic adhesive layer 23 , one on the metallic adhesive layer 23 provided metallic reflection layer 22 , one on the metallic reflection layer 22 provided transparent oxide film layer 21 and second thin ohmic electrodes on an n-type side 20 that is in the transparent oxide film layer 21 are provided, and is provided with a conductive, ohmic electrode 25 under the conductive support substrate 24 with the above-described light-emitting part 19 on the transparent oxide film layer 21 Mistake. The first thin ohmic electrodes 11 and the second thin ohmic electrodes 20 For example, they are arranged so that they do not overlap when viewed from above.

The total film thickness of the active quantum well layer 14 is preferably 200 nm or more and 300 nm or less. The reason for this is that the light-emitting efficiency of the semiconductor light-emitting device 10 with the light emission wavelength 585 nm as in 3 has a maximum value in a range in which the total film thickness of the active quantum well layer 14 200 nm or more and 300 nm or less. In 3 For example, the light emission efficiency is represented as a ratio, the light emission efficiency of an active quantum well layer 14 was set equal to "1" with a total film thickness of 250 nm.

By the way, the results in 3 shown curve curve because the light emission efficiency due to the carrier overflow decreases as the total film thickness of the active quantum well layer 14 less than 200 nm while absorbing through the well layer 16 increases and the improvement of the light emission efficiency is lost, although the carrier overflow can be suppressed when the total film thickness of the quantum well active layer 14 is more than 300 nm.

At a total film thickness of the active quantum well layer 14 of 200 nm or more, it is possible to suppress a decrease in the light emission efficiency due to the carrier overflow. At a total film thickness of the active quantum well layer 14 of 300 nm or less, it is possible to avoid an increase in manufacturing costs due to a longer production time and higher material costs.

In the active quantum well layer 14 For example, the film thickness of the pot layer 16 be set so that the light emission wavelength of the semiconductor light emitting device 10 and the number of pairs (if there are n well layers (n is a positive integer) and n + 1 barrier layers, the pair number n) can be set so that the total film thickness becomes a desired value in the above-mentioned range accepts.

The total film thickness of the active quantum well layer 14 may be about 250 nm, for example.

In the above with reference to 1 described semiconductor light emitting device according to the invention has the well layer 16 containing the active quantum well layer 14 and is composed of a compound semiconductor based on AlGaInP, has an Al content in the composition of 0.06 or less. Accordingly, the average Al content of the composition of the active quantum well layer 14 be reduced, thereby reducing the non-luminescent centers in the active quantum well layer 14 and a high light emission efficiency can be obtained in a range of shorter wavelengths (yellow emission).

With reference to 2 Now, an example of a manufacturing method for manufacturing the semiconductor light emitting device of the present invention will be described. Next, an example of manufacturing a semiconductor light emitting device having a light emission wavelength of 585 nm will be described.

First, as in 2 (a) shown on a GaAs substrate 26 a semiconductor layer structure formed of several AlGaInP-based materials. In detail, an etching stopper layer is successively formed 27 p-Ga _0.5 In _0.5 P, a contact layer 28 p-GaAs, the p-type current spreading layer 12 from p- (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P, the p-type overcoat layer 13 from p-Al _0.5 In _0.5 P, the active quantum well layer 14 , consisting of the pot layer 16 (Layer thickness about 2.7 nm) of undoped (Al _0.06 Ga _0.94 ) _0.5 In _0.5 P and the barrier layer 15 (Layer thickness about 7.7 nm) of undoped (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P, the n-type overcoat layer 17 of n-Al _0.5 In _0.5 P and the n-type current spreading layer 18 from n-GaP, for example by means of an MOVPE method (metalorganic vapor phase epitaxy), on the n-GaAs substrate 26 deposited. Illustrative examples of the starting material used in the MOVPE method include organometallic compounds such as trimethylgallium (TMGa), triethylgallium (TEGa), trimethylaluminum (TMAI), trimethylindium (TMIn), and also hydrogen gases such as arsine (AsH ₃ ) and Hydrogen phosphide (PH ₃ ). Monosilane (SiH ₄ ) can be used as the starting material for an n-type impurity, and as a raw material for a p-type impurity, bis (cyclopentadienyl) magnesium (Cp ₂ Mg) can be used. Illustrative examples of the starting material that can be used as the n-type dopant include, in addition, hydrogen selenide (H ₂ Se), disilane (Si ₂ H ₆ ), diethyltellurium (DETe) and dimethyltellurium (DMTe). Illustrative examples of the starting material that can be used as the p-type dopant include dimethylzinc (DMZn) and diethylzinc (DEZn).

Then, as in 2 B) shown, the transparent oxide film layer 21 and second thin ohmic electrodes 20 on an n-type side on the surface of the n-type current spreading layer 18 the semiconductor layer structure formed. In particular, after using a plasma CVD ( chemical vapor deposition) a SiO ₂ film as a transparent oxide film layer 21 has been formed, formed by means of a photolithography process and an etching process, an opening. More specifically, the opening in a region where no resist pattern is formed is removed by removing the transparent oxide film layer 21 formed with an etchant based on hydrofluoric acid as an etching solution. Then, on an n-type side in the opening by means of a vacuum deposition method, an AuSi alloy is formed, which is the material from which the second thin ohmic electrodes 20 consist.

Next, as in 2 (c) shown successively an Al layer as a reflection layer, a Ti layer as a barrier layer, and an Au layer as an adhesion layer by means of a vacuum deposition method or a sputtering method on the transparent oxide film layer 21 and the second thin ohmic electrodes 20 educated. These layers form the metallic reflection layer 22 , Incidentally, the material of the metallic reflection layer 22 depending on the wavelength of the active quantum well layer 14 emitted light selected so that the material has a high reflectivity with respect to this wavelength of light.

The stratification 29 can be prepared as described above.

Then, as in 2 (d) shown a carrier substrate 30 prepared so that as a conductive, resistive, metallic adhesive layer 23 on the conductive support substrate (eg, an Si substrate) 24 are formed by a vacuum deposition method Ti as a contact electrode, Ni as a barrier layer, and Au as an adhesion layer.

This carrier substrate 30 is with the layering 29 and thereby becomes a connection structure 31 created in which the carrier substrate 30 and the stratification 29 mechanically and electrically connected. This bonding of the wafers takes place in such a way that after setting the pressure in the interior of a bonding system to a prescribed pressure of the layer stack 29 and the carrier substrate 30 be compressed by means of a device and heated to a prescribed temperature. The specific bonding conditions include a pressure of 7000 N / m ² at a temperature of 350 ° C over a period of 30 minutes.

Subsequently, as in 2 (e) shown the n-GaAs substrate 26 with an etchant for etching GaAs quite specifically from the connection structure 31 removed so that the etch stop layer 27 of p-Ga _{0.5 is} exposed in _0.5 p. As the etchant for etching GaAs, for example, a mixed solution of aqueous ammonia and aqueous hydrogen peroxide is used. Next is the connection structure 31 of which the n-GaAs substrate 26 has been removed, the etch stop layer 27 removed by etching with a specific etchant (thereby forming a contact layer 28 exposed). When the etch stop layer 27 is formed of a compound semiconductor based on AlGaInP, as the prescribed etchant, a hydrochloric acid-containing etchant may be used.

Then, as in 2 (f) 4, a thin ohmic electrode is formed at a prescribed position by a photolithography method and a vacuum deposition method on the p-type side. The thin ohmic electrode of the p-type side consists of a circular electrode (not shown) and the first thin ohmic electrodes 11 and is formed, for example, by depositing Ti, AuBe and Au in this order. The first thin ohmic electrodes 11 and the second thin ohmic electrodes 20 For example, they are arranged so that they do not overlap. Subsequently, the contact layer 28 is removed from p-GaAs by etching using the thin ohmic electrode on the p-type side as a mask. The p-type current spreading layer 12 can be done using the contact layer 28 as a mask to be subjected to a roughening. It is also possible to use the p-type current spreading layer 12 after removing the contact layer 28 to roughen using a prescribed etchant.

Next, as in 2 (g) shown, by means of a vacuum deposition method, the conductive, ohmic electrode 25 on substantially the entire back surface of the conductive support substrate 24 educated. The conductive, ohmic electrode 25 on the back surface, for example, by depositing Ti and Au in this order on the underside of the conductive support substrate 24 be formed. Then, each ohmic electrode is subjected to an alloying process, which is an alloying process for forming electrical terminals. It is possible, as an example of the alloying process, to conduct a heat treatment at 400 ° C under an inert atmosphere or a nitrogen atmosphere over a period of 5 minutes. This can be a connection structure 32 be generated.

Subsequently, the connection structure 32 using a cutting device with blade divided into individual components. This allows multiple semiconductor light emitting devices 10 , as in 1 shown to be produced.

EXAMPLES

Hereinafter, the present invention will be described in detail with reference to an example and a comparative example, but the present invention is not limited thereto.

(Example)

The semiconductor light emitting device 10 from 1 was after the in 2 produced manufacturing method produced.

Here, each layer of the semiconductor light emitting device was 10 composed as follows:
the p-type current spreading layer 12 : p- (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P,
the p-type overcoat layer 13 : p-Al _0.5 In _0.5 P,
the barrier layer 15 : i- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P,
the pot layer 16 : i- (Al _0.06 Ga _0.94 ) _0.5 In _0.5 P,
the n-type overcoat layer 17 : n-Al _0.5 In _0.5 P,
the n-type current spreading layer 18 : n-GaP,
the GaAs substrate 26 : n-GaAs,
the etch stop layer 27 : p-Ga _0.5 In _0.5 P,
the contact layer 28 : p-GaAs.

Moreover, the light emission wavelengths of the semiconductor light emitting device became 10 ranging from 585 to 605 nm varies by the film thickness of the well layer 16 was changed while the Al portion of the composition of the well layer 16 was set to 0.06 and the number of pairs of pot layers 16 and the barrier layers 15 was adjusted so that the total film thickness of the active quantum well layer 14 as shown in Table 1 was about 250 nm.

In the semiconductor light emitting devices manufactured as described above, the light emission efficiencies were measured.

Table 1 indicates the structure of the quantum well active layer and the light emission efficiency of each light emission wavelength. In addition, Table 1 gives the light emission efficiency at the light emission wavelength of 615 nm as a reference. The light emission efficiencies diminished Light emission efficiency (%) = light output (mW) / supplied electric power (mW), calculated and represented as ratios, the light emission efficiency at the light emission wavelength 615 nm being set equal to "1".

4 Fig. 15 shows the relationship between the light emission wavelength and the light emission efficiency. [Table 1] Wavelength (nm) well layer barrier layer Total film thickness of the active quantum well layer (nm) Light emission efficiency Al proportion Film thickness (nm) Al proportion Film thickness (nm) 585 0.06 2.7 0.6 7.7 252 0.14 590 0.06 3.5 250 0.33 595 0.06 4 250 0.47 600 0.06 4.5 249 0.72 605 0.06 5.3 252 0.88 615 (reference) 0 4 250 1.00

(Comparative Example)

Semiconductor light emitting devices were fabricated using the same procedure as in the example, except that the Al content and the film thickness of the well layer 16 as changed in Table 2 to vary the light emission wavelengths in the range of 585 to 605 nm.

In the semiconductor light emitting devices manufactured as described above, the light emission efficiencies were measured in the same manner as in the example.

Table 2 indicates the structure of the quantum well active layer and the light emission efficiency of each light emission wavelength. In addition, Table 2 gives as a reference the light emission efficiency at the light emission wavelength of 615 nm.

4 Fig. 15 shows the relationship between the light emission wavelength and the light emission efficiency. [Table 2] Wavelength (nm) well layer barrier layer Total film thickness of the active quantum well layer (nm) Light emission efficiency Al proportion Film thickness (nm) Al proportion Film thickness (nm) 585 0.18 5.3 0.6 7.7 252 0.06 590 0.15 0.18 595 0.12 0.34 600 0.09 0.58 605 0 2.7 0.85 615 (reference) 0 4 250 1.00

As in 4 As shown, the examples in the light emission wavelength region of 585 nm or more and 605 nm or less show higher light emission efficiencies than the comparative examples.

It should be noted that the present invention is not limited to the foregoing embodiment. The embodiment is merely an illustration and all examples having substantially the same features and the same functions and effects as in the technical concept described in the claims are included in the technical possibilities of the present invention.

Claims (2)

A semiconductor light emitting device comprising an active quantum well layer consisting of well layers and barrier layers, wherein the semiconductor light emitting device has a light emission wavelength of 585 nm or more and 605 nm or less, the well semiconductor compound layer A composition formula of (Al _x Ga _1-x ) _y In _1-y P (0 <x ≦ 0.06, 0 <y <1), and the barrier layer is made of a compound semiconductor having a composition formula of (Al _m Ga _{1). m} ) _n In _1-n P (0 ≦ m ≦ 1, 0 <n <1). The semiconductor light emitting device according to claim 1, wherein said quantum well active layer has a total film thickness of 200 nm or more and 300 nm or less.

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