JP5582066B2 - Compound semiconductor substrate, method of manufacturing compound semiconductor substrate, and light emitting device - Google Patents

Description

  The present invention relates to a compound semiconductor substrate, a method of manufacturing a compound semiconductor substrate, and a light emitting element, and more specifically, to stably supply a light emitting element that can suppress an increase in forward voltage due to energization and can realize high luminance. The present invention relates to a compound semiconductor substrate, a method for manufacturing the compound semiconductor substrate, and a light emitting element.

A light-emitting element in which a light-emitting layer and a current diffusion layer are formed on a GaAs substrate is conventionally known.
For example, a light emitting element is known in which a light emitting layer composed of four elements of AlGaInP and a current diffusion layer composed of GaP are formed on a GaAs substrate. In this GaP current diffusion layer, a relatively thin current diffusion layer (hereinafter referred to as a thin film current diffusion layer) was formed on the light emitting layer side by metal organic vapor phase epitaxy (Metal Organic Vapor Phase Epitaxy, hereinafter simply referred to as MOVPE). Later, it can be formed by forming a relatively thick current diffusion layer (hereinafter referred to as a thick film current diffusion layer) by a hydride vapor phase epitaxy method (hereinafter referred to as HVPE method). For example, the GaP current diffusion layer may be grown to a thickness of about 200 μm as a whole.

  Further, in order to realize further increase in luminance of the light emitting element made of AlGaInP, the light-absorbing GaAs substrate is removed and a light-transmitting GaP substrate is bonded instead. By forming an InGaP intermediate layer doped at a high concentration at the junction interface, a light-emitting element that can sufficiently reduce the element series resistance at the junction interface and has good switching response has been known (Patent Literature). 1).

JP 2007-324551 A

As a result of intensive studies by the present inventors, the above-described direct-junction light-emitting element has a concentration of impurities such as oxygen and carbon at the junction interface between the quaternary light-emitting layer and the GaP substrate that is not constant for each production batch. It was found that it was not stable.
Further, such an impurity such as oxygen and carbon at the junction interface diffuses to the quaternary light emitting layer side when energized and compensates for carriers. As a result, it has been found that the forward voltage is increased, and the lifetime characteristics of the manufactured light emitting device with respect to the forward voltage are deteriorated.

  The present invention has been made in view of the above problems, and even when impurities such as oxygen and carbon are generated at the junction interface between the quaternary light emitting layer and the GaP substrate, the forward voltage increases when energized. And a method for manufacturing the same, and a light-emitting device manufactured from such a compound semiconductor substrate are provided. .

In order to achieve the above object, in the present invention, at least an (Al _x Ga _1-x ) _y In _1-y P (where 0 <x <1, 0 <y <1) is formed on an n-type GaP substrate. It has a quaternary light emitting layer in which an n-type cladding layer, an active layer, and a p-type cladding layer are sequentially laminated. The main surface of the quaternary light emitting layer on the n-type GaP substrate side (hereinafter also referred to as a second main surface). ), A compound semiconductor substrate in which a p-type GaP layer as a current diffusion layer is stacked on a main surface (hereinafter also referred to as a first main surface) opposite to the n-type GaP substrate and the quaternary element (Al _x Ga _1-x ) _y In _1-y P (where 0 <x ≦ 1, 0 <y <1), which has a higher carrier concentration than the n-type cladding layer. Provided is a compound semiconductor substrate in which a high concentration carrier layer is formed.

  Thus, if a compound semiconductor substrate in which a high concentration carrier layer is formed between an n-type GaP substrate and a quaternary light emitting layer, when a light emitting element manufactured from such a compound semiconductor substrate is energized, Even if impurities such as oxygen and carbon at the junction interface between the n-type GaP substrate and the quaternary light emitting layer diffuse into the quaternary light emitting layer and compensate the carriers, sufficient carriers are quaternized by the high concentration carrier layer. Supplied to the light emitting layer. For this reason, it can suppress that a forward voltage rises and it can suppress that the lifetime characteristic with respect to the forward voltage of the light emitting element manufactured by this deteriorates.

At this time, the high concentration carrier layer preferably has a carrier concentration of 1.0 × 10 ¹⁸ atoms / cm ³ or more.
The high-concentration carrier layer preferably has a thickness of 500 mm or more.

  If the high-concentration carrier layer is formed in this way, it is possible to more reliably suppress an increase in forward voltage after energization.

  The present invention also provides a light emitting device manufactured from the compound semiconductor substrate of the present invention.

  A light emitting device manufactured in this way has a very good lifetime characteristic with respect to a forward voltage, and can be used for a long time in a high luminance state.

Further, the present invention provides at least an n _- type cladding layer made of (Al _x Ga _1-x ) _y In _1-y P (where 0 <x <1, 0 <y <1) on an n-type GaAs substrate, active A step of epitaxially growing a quaternary light emitting layer in which a layer and a p-type cladding layer are sequentially laminated, and a current on a main surface (first main surface) opposite to the n-type GaAs substrate side of the quaternary light emitting layer A step of epitaxially growing a p-type GaP layer as a diffusion layer; a step of removing an n-type GaAs substrate from the quaternary light-emitting layer; and a main surface (first surface) of the quaternary light-emitting layer on the side where the n-type GaAs substrate is removed. And a step of bonding an n-type GaP substrate to the second principal surface) side of the quaternary light-emitting layer on the n-type GaAs substrate before the quaternary light-emitting layer is epitaxially grown. Carry High _{density, (Al x Ga 1-x} ) y In 1-y P ( However, 0 <x ≦ 1,0 <y <1) the high-concentration carrier layer laminated made of, then the high-concentration carrier layer The bonding step is performed by epitaxially growing the quaternary light emitting layer or laminating the high-concentration carrier layer on the second main surface side of the quaternary light emitting layer before bonding the n-type GaP substrate. Wherein the high concentration carrier layer and the n-type GaP substrate are bonded together to produce a compound semiconductor substrate in which the high concentration carrier layer is formed between the n-type GaP substrate and the quaternary light emitting layer. A method of manufacturing a compound semiconductor substrate is provided.

  With such a manufacturing method, the high-concentration carrier layer can be reliably formed between the n-type GaP substrate and the quaternary light emitting layer. Thereby, an increase in the forward voltage when energized is suppressed, and a compound semiconductor substrate serving as a raw material of a light-emitting element having good lifetime characteristics with respect to the forward voltage can be manufactured.

As described above, the compound semiconductor substrate of the present invention has (Al _x Ga _1-x ) _y In ₁ having a carrier concentration higher than that of the n-type cladding layer between the n-type GaP substrate and the quaternary light emitting layer. _Since a high-concentration carrier layer made of _-yP is formed, a junction interface between the n-type GaP substrate and the quaternary light-emitting layer when a light-emitting element manufactured from such a compound semiconductor substrate is energized Even if impurities such as oxygen and carbon diffuse in the quaternary light-emitting layer and compensate carriers, sufficient carriers are supplied to the quaternary light-emitting layer by the high-concentration carrier layer, so that an increase in forward voltage is suppressed. can do.
Further, the high-concentration carrier layer is laminated on the n-type GaAs substrate before epitaxially growing the quaternary light-emitting layer, and then the quaternary light-emitting layer is epitaxially grown on the high-concentration carrier layer, or If the high-concentration carrier layer is laminated on the two principal surfaces before the n-type GaP substrate is bonded, the high-concentration carrier layer is surely formed between the n-type GaP substrate and the quaternary light emitting layer. The manufactured high quality compound semiconductor substrate can be manufactured.
Furthermore, a light-emitting element manufactured from such a compound semiconductor substrate has good lifetime characteristics with respect to a forward voltage, and thus can be used for a long time in a high luminance state.

It is the figure which showed an example of the schematic sectional drawing of the compound semiconductor substrate of this invention. It is the figure which showed an example of the schematic sectional drawing of the light emitting element of this invention. 5 is a schematic cross-sectional view of a compound semiconductor substrate manufactured in Comparative Example 1. FIG. 6 is a schematic cross-sectional view of a compound semiconductor substrate manufactured in Comparative Example 2. FIG. It is the figure which showed the change rate of the forward voltage of each lamp | ramp manufactured from each compound semiconductor substrate in an Example and a comparative example. It is the figure which showed an example of the process flow of the manufacturing method of the compound semiconductor substrate of this invention.

Embodiments of the present invention will be specifically described below with reference to the drawings, but the present invention is not limited to these embodiments.
FIG. 1 is a schematic view showing an example of a compound semiconductor substrate of the present invention. A compound semiconductor substrate 1 according to the present invention shown in FIG. 1 is formed from (Al _x Ga _1-x ) _y In _1-y P (where 0 <x ≦ 1, 0 <y <1) on an n-type GaP substrate 2. The n-type high concentration carrier layer 3 is formed, and the light emitting layer 4 is formed on the high concentration carrier layer 3.
A p-type GaP thin film current diffusion layer 5 is formed on the light emitting layer 4 by the MOVPE method, and a p-type GaP thick film current diffusion layer 6 is formed thereon by the HVPE method.

As the light emitting layer 4, for example, an active layer 42 made of a non-doped (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 <y <1) mixed crystal is used as a p-type ( _{Al z Ga 1-z) y} In 1-y P ( where the p-type cladding layer 43 made of x <z ≦ 1), made of n-type _{(Al z Ga 1-z)} y In 1-y P n The quaternary light emitting layer 4 can be sandwiched between the mold cladding layers 41.
The term “non-doped” as used herein means “not to add dopants positively”, and includes a dopant component inevitably mixed in the manufacturing process of the compound semiconductor substrate (for example, 1.0 × 10 ^13). (About 1.0 × 10 ¹⁶ atoms / cm ³ ) is not excluded.

When the light emitting device 10 manufactured from such a compound semiconductor substrate 1 is energized, impurities such as oxygen and carbon at the junction interface between the n-type GaP substrate 2 and the quaternary light emitting layer 4 are quaternary light emitting layers. 4, the carrier voltage is compensated to increase the forward voltage, and the life characteristics with respect to the forward voltage may be deteriorated.
However, in the present invention, since the high-concentration carrier layer 3 is formed between the n-type GaP substrate 2 and the quaternary light-emitting layer 4, sufficient carriers are transferred to the quaternary light-emitting layer 4 by the high-concentration carrier layer 3. Supplied to. For this reason, it can suppress that a forward voltage rises and can make a lifetime characteristic favorable.

At this time, if the carrier concentration of the high-concentration carrier layer 3 is 1.0 × 10 ¹⁸ atoms / cm ³ or more and the film thickness is 500 mm or more, the increase in the forward voltage can be more reliably suppressed. This is preferable because it is possible.

Moreover, the optical element 10 as shown in FIG. 2 can be manufactured using such a compound semiconductor substrate 1.
In this optical element 10, a first electrode 11 for applying a light emission driving voltage to the quaternary light emitting layer 4 is formed at substantially the center on the thick film current diffusion layer 6 of the compound semiconductor substrate 1 shown in FIG. A region around the first electrode 11 is a light extraction region from the quaternary light emitting layer 4. The second electrode 12 is formed on the entire surface of the n-type GaP substrate 2 on the second main surface side. A bonding pad 13 made of Au or the like for bonding an electrode wire is disposed at the center of the first electrode 11.
The light-emitting element 10 manufactured in this way has a good lifetime characteristic with respect to the forward voltage, and can be used for a long time in a high-brightness state.

  Various layers may be inserted between the above layers of the compound semiconductor substrate 1 in the present invention as necessary.

Hereinafter, a method of manufacturing the compound semiconductor substrate 1 shown in FIG. 1 will be described with reference to the flowchart shown in FIG.
First, as shown in step 1, an n-type GaAs substrate is prepared as a growth substrate, cleaned, and then placed in a MOVPE reactor, and an n-type GaAs buffer layer is epitaxially grown on the n-type GaAs substrate by 0.1 to 1.0 μm. Let

Next, as shown in step 2, an n-type high concentration carrier layer 3 made of AlGaInP is formed on the n-type GaAs buffer layer so as to have a film thickness of 0.05 μm (500 mm) or more.
Next, as shown in step 3, an n-type clad layer 41 having a thickness of 0.8 to 4.0 μm and made of AlGaInP as the quaternary light emitting layer 4 is formed on the high-concentration carrier layer 3 and has a thickness of 0.4 to 4. An active layer 42 having a thickness of 2.0 μm and a p-type cladding layer 43 having a thickness of 0.8 to 4.0 μm are epitaxially grown in this order. At this time, the carrier concentration of the high concentration carrier layer 3 is set to, for example, 1.0 × 10 ¹⁸ atoms / cm ³ or more so as to be higher than the carrier concentration of the n-type cladding layer 41.

The epitaxial growth of each of the above layers is performed by a known MOVPE method. Although not limited to these as source gas used as each component source of Al, Ga, In, and P, for example, the following can be used.
Al source gas: trimethylaluminum (TMAl), triethylaluminum (TEAl), etc.
Ga source gas: trimethylgallium (TMGa), triethylgallium (TEGa), etc.
In source gas: trimethylindium (TMIn), triethylindium (TEIn), etc.
P source gas: trimethyl phosphorus (TMP), triethyl phosphorus (TEP), phosphine (PH ₃ ), etc.
Moreover, the following can be used as dopant gas.
(P-type dopant)
Mg source: biscyclopentadienyl magnesium (Cp ₂ Mg), etc.
Zn source: dimethyl zinc (DMZn), diethyl zinc (DEZn), etc.
(N-type dopant)
Si source: silicon hydride such as monosilane.

  Next, the process proceeds to Step 4, and a p-type GaP thin film current diffusion layer 5 having a thickness of 0.05 to 1.0 μm is heteroepitaxially grown on the p-type cladding layer 43 by the MOVPE method to obtain an MO epitaxial wafer. Further, a p-type GaP thick film current diffusion layer 6 having a thickness of 5 μm to 200 μm is vapor-phase grown on the MO epitaxial wafer by HVPE.

Specifically, in the HVPE method, the reaction of the following formula (1) is performed by introducing hydrogen chloride onto the metal Ga while heating and maintaining the metal Ga, which is a group III element, at a predetermined temperature in the container. Then, GaCl is generated and supplied onto the substrate together with H ₂ gas which is a carrier gas.
Ga (liquid) + HCl (gas) → GaCl (gas) + 1 / 2H ₂ (gas) (1)
The growth temperature is set to, for example, 640 ° C. or more and 860 ° C. or less. In addition, P, which is a group V element, supplies, for example, phosphine (PH ₃ ) together with H ₂ as a carrier gas onto the substrate. Furthermore, Zn which is a p-type dopant is supplied in the form of dimethylzinc (DMZn) and forms an n-type GaP epitaxial layer by a reaction such as the following formula (2).
GaCl (gas) + PH3 (gas)
→ GaP (solid) + HCl (gas) + H2 (gas) (2)

  Next, as shown in step 5, the n-type GaAs substrate and the n-type GaAs buffer layer are removed by etching or the like. Then, as shown in step 6, the n-type GaP substrate 2 is bonded to the high-concentration carrier layer 3 exposed by removing the n-type GaAs substrate, and the compound semiconductor substrate 1 is manufactured.

Further, instead of laminating the high-concentration carrier layer 3 between the n-type GaAs substrate and the quaternary light emitting layer 4 as described above, after removing the GaAs substrate, the second main surface side of the quaternary light emitting layer 4 In addition, by stacking the high concentration carrier layer 3 before the n-type GaP substrate 2 is bonded, the compound semiconductor substrate 1 can be manufactured by bonding the high concentration carrier layer 3 and the n-type GaP substrate 2 together.
An n-type GaInP layer may be sandwiched between the second main surface side of the quaternary light emitting layer and the n-type GaP substrate.

Although not limited thereto, the light emitting device 10 can be manufactured as follows after the above steps are completed.
The first electrode 11 and the second electrode 12 are formed by vacuum vapor deposition, and the bonding pad 13 is further disposed on the first electrode 11, and baking for electrode fixing is performed at an appropriate temperature. Thereafter, the chip is formed by dicing, and the second electrode 12 is fixed to a terminal electrode (not shown) that also serves as a support by using a conductive paste such as an Ag paste, while Au Au is bonded to the bonding pad 13 and another terminal electrode. A light-emitting element 10 as shown in FIG. 2 can be manufactured from the compound semiconductor substrate 1 by bonding a manufactured wire and further forming a resin mold.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to this.

(Example)
First, a compound semiconductor substrate as shown in FIG. 1 was manufactured as follows.
By MOVPE, an n-type GaAs buffer layer of 0.5 μm, a quaternary light emitting layer of 3.0 μm, and a p-type GaP thin film current diffusion layer of 2.5 μm are sequentially epitaxially grown on a 280 μm thick n-type GaAs substrate. The quaternary light-emitting layer has a carrier concentration of 0.8 × 10 ¹⁸ atoms / cm ³ and an n-type cladding layer formed of (Al _0.85 Ga _0.15 ) _0.45 In _0.55 P 0. 8 μm, active layer 0.6 μm made of (Al _0.1 Ga _0.9 ) _0.45 In _0.55 P, p-type made of (Al _0.85 Ga _0.15 ) _0.45 In _0.55 P The cladding layer is formed by sequentially epitaxially growing 1.6 μm.
At this time, the film thickness is 0.3 μm (3000 mm) between the n-type GaAs buffer layer and the quaternary light emitting layer (n-type cladding layer), and the carrier concentration is 1.0 × 10 ¹⁸ atoms / cm. ³ n-type high-concentration carrier layers made of (Al _0.85 Ga _0.15 ) _0.45 In _0.55 P are stacked. Thereafter, a p-type GaP thick film current diffusion layer having a thickness of 150 μm is epitaxially grown on the p-type GaP thin film current diffusion layer by HVPE, and the n-type GaAs substrate is removed, whereby the n-type GaAs substrate is removed. An n-type GaP substrate having a thickness of 200 μm is bonded to the second main surface side of the original light emitting layer, that is, the main surface opposite to the n-type cladding layer of the high-concentration carrier layer.
Note that trimethylgallium (TMGa), trimethylindium (TMIn), trimethylaluminum (TMAl), phosphine (PH ₃ ), and arsine (AsH ₃ ) were used as source gases for the epitaxial growth.

At this time, oxygen 6.0 × 10 ¹⁹ atoms / cm ³ and carbon 4.0 × 10 ¹⁷ atoms / cm ³ existed as impurities at the junction interface between the high-concentration carrier layer and the n-type GaP substrate.
Seven lamps were selected from each of the two lamps produced from the two compound semiconductor substrates thus manufactured, and a current of 50 mA was applied to each lamp at a temperature of 85 ° C. for 100 hours. At this time, no forward voltage increase occurred in each lamp. FIG. 5 shows the average value, maximum value, and minimum value of the forward voltage change rate of seven lamps manufactured from each of the two substrates.

(Comparative Example 1)
A compound semiconductor substrate as shown in FIG. 3 is formed in the same manner as in Example 1 except that the n-type GaAs substrate is not removed, the n-type GaP substrate is not bonded, and the high-concentration carrier layer is not laminated. Created.
Seven lamps were selected from each of the two lamps produced from the two compound semiconductor substrates thus manufactured, and a current of 50 mA was applied to each lamp at a temperature of 85 ° C. for 100 hours. The compound semiconductor substrate used at this time does not remove the n-type GaAs substrate and does not join the n-type GaP substrate and the quaternary light-emitting layer, so that impurities such as oxygen and carbon are included in these junction interfaces. No increase in forward voltage occurred in each lamp. The result at this time is shown in FIG.

(Comparative Example 2)
A compound semiconductor substrate as shown in FIG. 4 was prepared in the same manner as in Example 1 except that the high concentration carrier layer was not laminated.
Seven lamps were selected from each of the two lamps produced from the two compound semiconductor substrates thus manufactured, and a current of 50 mA was applied to each lamp at a temperature of 85 ° C. for 100 hours. At this time, the forward voltage increased about 17% at the maximum, and about 2-3% on the average. The result at this time is shown in FIG.

In Comparative Example 1, since the n-type GaP substrate and the quaternary light emitting layer are not joined, the forward voltage does not increase. However, since the n-type GaAs substrate is used, the light emitting element has low luminance. End up. In Comparative Example 2, the junction interface between the n-type GaP substrate and the quaternary light emitting layer contains impurities such as oxygen and carbon, and when a light emitting element such as a lamp manufactured from such a compound semiconductor substrate is energized In addition, these impurities diffuse to the quaternary light emitting layer side to compensate for n-type carriers, thereby increasing the forward voltage and deteriorating the forward voltage life characteristics.
However, in the example, since the high-concentration carrier layer and the quaternary light emitting layer are bonded, impurities such as oxygen and carbon are included in the bonding interface. When the light-emitting element such as the manufactured lamp is energized, these impurities diffuse to the quaternary light-emitting layer side and the n-type carrier compensates. However, since carriers are sufficiently supplied from the high-concentration carrier layer, There was no change in the forward voltage, and the light emitting device had a high luminance with stable life characteristics.

  The present invention is not limited to the embodiment described above. The above-described embodiment is merely an example, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and has the same effect can be used. Of course, it is included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Compound semiconductor substrate, 2 ... N-type GaP substrate, 3 ... High concentration carrier layer,
4 ... Light emitting layer, 5 ... Thin film current diffusion layer, 6 ... Thick film current diffusion layer, 10 ... Light emitting element,
11 ... 1st electrode, 12 ... 2nd electrode, 13 ... Bonding pad,
41 ... n-type cladding layer, 42 ... active layer, 43 ... p-type cladding layer.

Claims (9)

An n-type cladding layer, an active layer, and a p-type cladding layer made of (Al _x Ga _1-x ) _y In _1-y P (where 0 <x <1, 0 <y <1) are formed on an n-type GaP substrate. On the main surface (first main surface) opposite to the main surface (second main surface) on the n-type GaP substrate side of the quaternary light-emitting layer, which is sequentially laminated, A compound semiconductor substrate in which a p-type GaP layer as a current spreading layer is laminated,
(Al _x Ga _1-x ) _y In _1-y P (where 0 <x ≦ 1) between the n-type GaP substrate and the quaternary light emitting layer and having a higher carrier concentration than the n-type cladding layer. , 0 <y <1), and a high concentration carrier layer is formed. 2. The compound semiconductor substrate according to claim 1, wherein the high concentration carrier layer has a carrier concentration of 1.0 × 10 ¹⁸ atoms / cm ³ or more.   The compound semiconductor substrate according to claim 1, wherein the high-concentration carrier layer has a thickness of 500 mm or more.   A light emitting device manufactured from the compound semiconductor substrate according to any one of claims 1 to 3. An n-type cladding layer, an active layer, and a p-type cladding layer made of (Al _x Ga _1-x ) _y In _1-y P (where 0 <x <1, 0 <y <1) are formed on an n-type GaAs substrate. A step of epitaxially growing a quaternary light emitting layer sequentially laminated;
A step of epitaxially growing a p-type GaP layer as a current diffusion layer on a main surface (first main surface) of the quaternary light emitting layer opposite to the n-type GaAs substrate side;
Removing the n-type GaAs substrate from the quaternary light emitting layer;
Bonding the n-type GaP substrate to the main surface (second main surface) side of the quaternary light emitting layer on the side from which the n-type GaAs substrate has been removed,
Before the quaternary light emitting layer is epitaxially grown on the n-type GaAs substrate, (Al _x Ga _1-x ) _y In _1-y P (where 0 <x A high-concentration carrier layer composed of ≦ 1,0 <y <1) is laminated, and then the quaternary light-emitting layer is epitaxially grown on the high-concentration carrier layer, or on the second main surface side of the quaternary light-emitting layer In the bonding step, the high concentration carrier layer and the n-type GaP substrate are bonded together by laminating the high concentration carrier layer before bonding the n-type GaP substrate. A method for producing a compound semiconductor substrate, comprising producing a compound semiconductor substrate in which the high-concentration carrier layer is formed between an original light-emitting layer. The compound semiconductor substrate according to claim 1, wherein the high-concentration carrier layer is a single layer. The compound semiconductor substrate according to claim 1, wherein the high-concentration carrier layer is in contact with the n-type cladding layer. 6. The method of manufacturing a compound semiconductor substrate according to claim 5, wherein the high-concentration carrier layer is a single layer. 6. The method of manufacturing a compound semiconductor substrate according to claim 5, wherein the high-concentration carrier layer is in contact with the n-type cladding layer.

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