JP2009277931A - Manufacturing method of nitride semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor light emitting element having improved light extraction efficiency by improving planarity of an interface between a p-type nitride semiconductor layer and a p-side electrode. <P>SOLUTION: In this manufacturing method of the nitride semiconductor light emitting element, at least an n-type nitride semiconductor layer 102, an active layer 103 and the p-type nitride semiconductor layer 104 are grown in this order over a substrate 101. The manufacturing method includes a process for making a surfactant material contact to the surface of the p-type nitride semiconductor layer before the p-side electrode 105 is grown, or contact to the surface of the p-side electrode in the middle of growing the p-side electrode. It is desirable that a surface energy of the surfactant material is smaller than that of the p-type nitride semiconductor layer and/or p-type electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a nitride semiconductor light emitting device, and more specifically, manufacture of a nitride semiconductor light emitting device having improved light extraction efficiency with improved flatness of the interface between the nitride semiconductor layer and the p-side electrode. Regarding the method.

  Generally, a nitride semiconductor light emitting device has a structure in which an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are grown on a substrate, and a p-side electrode is grown on the p-type nitride semiconductor layer. Have. However, since the p-type nitride semiconductor layer and the p-side electrode are made of different materials, and therefore, the surface energy of each layer is different, the interface between the p-type nitride semiconductor layer and the p-side electrode is made steep. And difficult to flatten. When the interface is not steep or flat, light scattering and absorption occur at the interface, and the light extraction efficiency decreases.

Incidentally, Patent Document 1 and Non-Patent Document 1 disclose that a surfactant that changes the surface state of the GaN-based nitride semiconductor layer is formed by MOCVD or MBE.
Japanese Patent Laid-Open No. 10-79501 F. Widmann, B.M. Daudin, G .; Feillet, N.M. Pelekanos, and J.A. L. Rouviere, Applied Physics Letters, vol. 73, Number 18, p2642

  The present invention has been made in view of the above points, and nitride semiconductor light emission in which light extraction efficiency is improved by improving the flatness of the interface between the p-type nitride semiconductor layer and the p-side electrode. An object is to provide an element.

  The method for manufacturing a nitride semiconductor light emitting device according to the present invention is a method for manufacturing a nitride semiconductor light emitting device in which at least an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are grown in this order on a substrate. A step of bringing a surfactant substance into contact with the surface of the p-type nitride semiconductor layer before the growth of the p-side electrode or the surface of the p-side electrode during the growth of the p-side electrode is provided. Here, the surface energy of the surfactant substance is preferably smaller than the surface energy of the p-type nitride semiconductor layer and / or the p-type electrode.

  In the case where the p-side electrode is made of Ag, the surfactant materials are Y, La, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Zn, Al, Ga, In, Tl, Ge, Sn, It is preferably composed of at least one element selected from the group consisting of Pb, Cd, Hg, As, Sb and Bi. In the case where the p-side electrode is made of Pd, Ni or Pt, the surfactant substance is Sc, Mn, Cu, Y, La, Au, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg. , Zn, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Cd, Hg, As, Sb, and Bi, and preferably made of at least one element selected from the group consisting of.

  In the method for manufacturing a nitride semiconductor light emitting device of the present invention, preferably, in the growth interruption step immediately before growing the p-side electrode, the surface of the p-type nitride semiconductor layer is brought into contact with the surfactant substance, or the p-side electrode A surfactant substance is brought into contact with the surface of the p-side electrode during the growth.

  As a method for bringing the surfactant substance into contact with the p-type nitride semiconductor layer surface or the p-side electrode surface during the growth, metal organic vapor phase epitaxy, sputtering, or vacuum deposition can be preferably used.

  In the method for manufacturing a nitride semiconductor light emitting device of the present invention, the surfactant substance is preferably added in an amount of 3 ML or less on the surface of the p-type nitride semiconductor layer or on the p-side electrode surface during the growth. In addition, it is preferable to further include a step of performing an annealing treatment after the step of bringing the surfactant material into contact.

  According to the present invention, the light extraction efficiency of a nitride semiconductor light emitting device such as a blue light emitting nitride semiconductor light emitting diode device can be improved.

  The present invention provides a method for manufacturing a nitride semiconductor light emitting device in which at least an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are grown in this order on a substrate, before the p-side electrode is grown. The method includes a step of bringing a surfactant substance into contact with the surface of the p-type nitride semiconductor layer or the surface of the p-side electrode during the growth of the p-side electrode. By bringing the surfactant material into contact, the growth mode of the p-side electrode can be changed to the Frank-van der Merwe mode (hereinafter referred to as FM mode). As a result, the p-type nitride semiconductor layer and the p-side The interface between the electrodes can be flattened. In the present invention, the “surfactant substance” is defined as a substance that changes the growth form of a film grown on the surface depending on the difference in surface / interface energy between the substrate surface and the surface of the substrate. In the present invention, the substrate surface means the p-type nitride semiconductor layer surface or the p-side electrode surface during the growth of the p-side electrode, and the growth mode (growth mode) of the film grown on the substrate surface is preferably Is the FM mode.

Here, generally, there are the following three types of thin film growth modes.
(A) Volmer-Weber mode (V-W mode)
The deposited atoms form nuclei on the substrate, and these nuclei grow in a three-dimensional island shape before forming a monoatomic layer. Also called nuclear growth or island growth.
(B) Frank-van der Merwe mode (FM mode)
The deposited atoms grow into a two-dimensional monoatomic layer so as to uniformly cover the substrate surface. Also called layered growth.
(C) Transki-Krastanov mode (SK mode)
A combination of the VW mode and the FM mode. First, several atomic layers are formed, and then island growth is performed from a certain layer. Also called layered + island growth.

Microscopically, which growth mode is dominant among the above growth modes, such as the lattice constant of the substrate crystal and the deposited film, the cleanliness of the substrate surface, the substrate temperature, the deposition rate, the degree of vacuum, etc. Although it depends on the behavior of adsorbed atoms due to the influence, it depends macroscopically on the surface and interface energy of the entire system. That is, which growth mode is dominant depends on the surface energy of the substrate per unit area (in the present invention, the p-type nitride semiconductor layer or the p-side electrode during the growth of the p-side electrode), the thin film (present In the present invention, assuming that the surface energy of the p-side electrode grown on the substrate is γ _S and γ _f and the interfacial energy per unit area is γ _i , the growth mode is expressed by the following formula (1). It can be predicted based on the energy D indicated by The surface energy means the total surface energy determined by the intermolecular force and the intersurface force, and can be measured, for example, by contact angle measurement.
Energy D = γ _f + γ _i −γ _S (1)
The VW mode is likely to occur under conditions where the surface energy γ _{S of the} substrate is small and D ≧ 0. This can be interpreted as the interaction between adsorbed atoms prevailing over the influence of the substrate, and thus forming a cluster.

On the other hand, in order to be in the FM mode, the energy D needs to satisfy the following formula (2).
Energy D = γ _f + γ _i −γ _S ≦ 0 (2)
In the case of homoepitaxial, since γ _f = γ _S and γ _i = 0, it is generally understood that the condition of the above formula (2) is satisfied. In the case of heteroepitaxial, γ _i is generally positive, so that γ _s > γ _f must be satisfied in order to be in the FM mode. It tends to occur on substrates with large energy.

From the above, in order to grow the p-side electrode in the FM mode and planarize the interface between the p-type nitride semiconductor layer and the p-side electrode, the surface energy of the p-side electrode is changed to the p-type nitride semiconductor. It can be seen that the surface energy of the layer needs to be reduced. In order to achieve such a relationship, a surfactant substance is used in the present invention. By adding a material that is smaller than the surface energy of the p-type nitride semiconductor layer and / or the p-type electrode as a surfactant material, and preferably smaller than the surface energy of both, the energy of the entire system is lowered, and the p-type electrode becomes It will grow in FM mode. More specifically, the surfactant material in the present invention is smaller than the general surface energy value (about 2.0 J / m ² ) of GaN mainly used in nitride semiconductor light emitting devices, and more than the p-side electrode. It is more preferable that the material has a small surface energy.

  For example, when the p-side electrode is made of Ag, the GaN-based semiconductor layer mainly used as the p-type nitride semiconductor layer and the surfactant material having a surface energy smaller than that of the p-side electrode include Y, La, Li, Na Consisting of an element selected from the group consisting of K, Rb, Cs, Ca, Sr, Ba, Mg, Zn, Al, Ga, In, Tl, Ge, Sn, Pb, Cd, Hg, As, Sb and Bi A substance containing two or more elements selected from these may be used. Further, when the p-side electrode is made of Pd, Ni, or Pt, a GaN-based semiconductor layer mainly used as the p-type nitride semiconductor layer and a surfactant material having a surface energy smaller than that of the p-side electrode include Sc, Mn Cu, Y, La, Au, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Zn, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Cd, Hg, As , Sb and Bi may be used, and a substance containing two or more elements selected from these may be used.

  The specific means for bringing the surfactant material into contact with the surface of the p-type nitride semiconductor layer or the surface of the p-side electrode during the growth of the p-side electrode is not particularly limited, and for example, metal organic vapor phase epitaxy, sputtering, or vacuum Vapor deposition can be preferably used. The addition of the surfactant substance using these methods can be performed under appropriate conditions using a conventionally known apparatus.

In the organometallic vapor phase growth method, an organometallic compound containing an element which is a surfactant substance can be used as a raw material gas. As source gases, trimethylindium (TMI), triethylindium; trimethylaluminum (TMA), triethylaluminum (TEA); trimethylgallium (TMG), triethylgallium; cyclopentadienylmagnesium (Cp ₂ Mg), ethylcyclopentadi Enilmagnesium (EtCp ₂ Mg); dimethyl zinc (DMZn), diethyl zinc (DMZn); silane (SiH ₄ ), trimethyl silicon (TMSi), triethyl silicon (TESi); germane (GeH ₄ ), tetramethyl germane (TMGe) Etc. can be used.

  The sputtering method and the vacuum deposition method can be suitably used for all the surfactant materials listed above.

  When the step of contacting the surfactant material is performed before growing the p-side electrode, the step of contacting the surfactant material ensures that the surfactant material acts on the p-type nitride semiconductor layer surface and the p-side electrode interface. Therefore, it is preferably performed in the growth interruption step immediately before growing the p-side electrode. The growth interruption step immediately before the growth of the p-side electrode means a step of not supplying at least one of a group III source material gas and a group V source gas introduced during the growth of the p-type nitride semiconductor layer. . In addition, when a surfactant substance is brought into contact with the p-side electrode surface during the growth of the p-side electrode, the surfactant substance may be added at any stage during the growth. By introducing a surfactant substance during the growth of the p-side electrode, the speed of device formation can be increased and productivity can be improved.

  In the present invention, the addition amount of the surfactant substance is not particularly limited, but p is increased during the growth of the p-type nitride semiconductor layer surface or the p-side electrode so as to be 3 ML (mono layer, monolayer) or less. The surfactant material is preferably brought into contact with the surface of the side electrode. When the addition amount of the surfactant material exceeds 3 ML, the flatness of the interface between the p-type nitride semiconductor layer and the p-side electrode tends not to be improved. The addition amount of the surfactant substance is more preferably 1 ML or less, and further preferably 0.5 ML or less. The addition amount (in ML units) of the surfactant substance can be measured by, for example, low-energy ion scattering spectroscopy (ISS).

  In the present invention, the nitride semiconductor light emitting device is annealed (heat treatment) after the step of bringing the surfactant material into contact and before, during or after the growth of the p-side electrode. ) May be applied. Such annealing treatment can further improve the flatness of the interface between the p-type nitride semiconductor layer and the p-side electrode. The temperature of annealing treatment is 50-800 degreeC, for example, Preferably it is 100-300 degreeC.

In the present invention, conventionally known materials and structures can be employed for the substrate, the n-type nitride semiconductor layer, the active layer, and the p-type nitride semiconductor layer. Specifically, although not particularly limited, for example, sapphire, SiC, Si, ZnO or the like can be used as the substrate. The n-type nitride semiconductor layer can be composed of Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and includes a GaN buffer layer, an AlN buffer layer, and an undoped layer. Layers and the like may be included. The n-type nitride semiconductor layer can be formed by a metal organic chemical vapor deposition method (MOCVD method) or the like. The active layer may have, for example, a multiple quantum well structure in which well layers and barrier layers having different band gaps are alternately stacked. The well layer and the barrier layer are respectively In _x Ga _1-x N (0 <x ≦ 1) and Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1). These can be formed by metal organic chemical vapor deposition (MOCVD) or the like. The p-type nitride semiconductor layer can be made of Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1). A multilayer structure in which a clad layer containing Al and a GaN layer are formed in this order is preferable. The p-type nitride semiconductor layer can be formed by a metal organic chemical vapor deposition method (MOCVD method) or the like.

  The p-side electrode can be formed using a conventionally known method and material. The p-side electrode can be made of, for example, Ag, Pd, Ni, Pt, Au, ITO, IZO, ZnO, or the like. The nitride semiconductor light-emitting device obtained by the present invention can have a conventionally known structure, for example, a flip-chip type or upper / lower electrode type structure.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
A nitride semiconductor light-emitting diode element having the structure shown in FIG. 1 was produced by the following method. First, a substrate 101 made of sapphire was prepared and set in a reactor of an MOCVD apparatus. Then, while flowing hydrogen into the reaction furnace, the temperature of the substrate 101 was raised to 1050 ° C., and the surface (C surface) of the substrate 101 was cleaned. Next, the temperature of the substrate 101 is lowered to 510 ° C., hydrogen as a carrier gas, ammonia and TMG (trimethylgallium) as a source gas are flown into the reaction furnace, and GaN is formed on the surface (C surface) of the substrate 101. The buffer layer was laminated with a thickness of about 20 nm by the MOCVD method. Next, the temperature of the substrate 101 is raised to 1050 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are allowed to flow into the reaction furnace to form an n-type nitride composed of GaN doped with Si. A semiconductor underlayer (carrier concentration: 1 × 10 ¹⁸ / cm ³ ) was laminated with a thickness of 6 μm on the buffer layer by MOCVD. Subsequently, an n-type nitride semiconductor contact layer made of GaN is formed by MOCVD in the same manner as the n-type nitride semiconductor underlayer except that Si is doped so that the carrier concentration becomes 5 × 10 ¹⁸ / cm ^3. An n-type nitride semiconductor layer 102 composed of a buffer layer, an n-type nitride underlayer, and an n-type nitride semiconductor contact layer was formed on the n-type nitride semiconductor underlayer with a thickness of 0.5 μm.

Next, as a well layer growth step, the temperature of the substrate 101 is lowered to 700 ° C., nitrogen as a carrier gas, ammonia, TMG and TMI (trimethylindium) as a source gas are flown into the reactor, and an n-type nitride semiconductor An In _0.15 Ga _0.75 N well layer having a thickness of 2.5 nm was grown on the contact layer. Subsequently, as a barrier layer growth step, the temperature of the substrate 101 is maintained at 700 ° C., nitrogen as a carrier gas, ammonia and TMG as a source gas are flowed into the reactor, and a GaN barrier layer is stacked with a thickness of 18 nm. . The well layer growth step and the barrier layer growth step are defined as one cycle, and a total of six cycles are performed to form the active layer 103.

Next, the temperature of the substrate 101 is increased to 950 ° C., hydrogen as a carrier gas, ammonia, TMG and TMA (trimethylaluminum) as source gases, and CP ₂ Mg (cyclopentadienylmagnesium) as impurity gases are flowed into the reactor. Then, a p-type nitride semiconductor clad layer made of Al _0.15 Ga _0.85 N doped with Mg at a concentration of 1 × 10 ²⁰ / cm ³ was laminated on the active layer 103 to a thickness of about 30 nm by the MOCVD method. Next, the temperature of the substrate 101 is maintained at 950 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and CP ₂ Mg as impurity gases are flown into the reactor, and Mg is 1 × 10 ²⁰ / cm ³ . A p-type nitride semiconductor contact layer made of GaN doped at a concentration is stacked on the p-type nitride semiconductor clad layer by the MOCVD method to a thickness of 0.1 μm, and the p-type nitride semiconductor clad layer and the p-type nitride semiconductor are laminated. A p-type nitride semiconductor layer 104 made of a metal semiconductor contact layer was formed.

  Next, Bi 0.3 ML as a surfactant material was added on the surface of the p-type nitride semiconductor layer 104 by a sputtering method. The sputtering conditions were a gas pressure of 6.5 mTorr, a sputtering power of 45 W, and a sputtering gas of Ar. Subsequently, Ag was laminated as the p-side electrode 105 to obtain a nitride semiconductor light-emitting diode element having the structure shown in FIG. When the light output of the obtained nitride semiconductor light-emitting diode device was measured, the light output was higher than that of a nitride semiconductor light-emitting diode device manufactured without contacting a surfactant substance.

<Example 2>
Surfactant substances are respectively Y, La, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Zn, Al, Ga, In, Tl, Ge, Sn, Pb, Cd, Hg, As, and Sb. A nitride semiconductor light-emitting diode element is completed in the same manner as in Example 1 except that. As a method for adding the surfactant substance, metal organic vapor phase epitaxy, sputtering, or vacuum deposition is used.

<Example 3>
A nitride semiconductor light-emitting diode element is completed in the same manner as in Example 1 except that the p-side electrode is Pd, Ni, or Pt.

<Example 4>
The surfactant materials are Sc, Mn, Cu, Y, La, Au, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Zn, Al, Ga, In, Tl, Si, Ge, Sn, respectively. , Pb, Cd, Hg, As, and Sb, and a nitride semiconductor light emitting diode device is completed in the same manner as in Example 3. As a method for adding the surfactant substance, metal organic vapor phase epitaxy, sputtering, or vacuum deposition is used.

<Example 5>
A nitride semiconductor light-emitting diode device is completed in the same manner as in Examples 1 to 4, except that the surfactant material is added during the growth of the p-side electrode.

<Example 6>
A nitride semiconductor light-emitting diode device is completed in the same manner as in Examples 1 to 5, except that the amount of the surfactant substance added is 3 ML or less (monolayer) or less.

<Example 7>
A nitride semiconductor light-emitting diode device is completed in the same manner as in Examples 1 to 6, except that an annealing treatment at about 300 ° C. is performed after the addition of the surfactant material.

  When the light output of the nitride semiconductor light-emitting diode elements obtained in Examples 2 to 7 was measured, the light output was higher than that of the nitride semiconductor light-emitting diode element manufactured without contacting the surfactant substance.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic sectional drawing which shows an example of the nitride semiconductor light-emitting device obtained by this invention.

Explanation of symbols

  101 substrate, 102 n-type nitride semiconductor layer, 103 active layer, 104 p-type nitride semiconductor layer, 105 p-side electrode.

Claims (9)

In a method for manufacturing a nitride semiconductor light emitting device, wherein at least an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are grown in this order on a substrate.
A method for manufacturing a nitride semiconductor light emitting device, comprising a step of bringing a surfactant substance into contact with the surface of the p-type nitride semiconductor layer before the growth of the p-side electrode or the surface of the p-side electrode during the growth of the p-side electrode.   2. The method of manufacturing a nitride semiconductor light emitting device according to claim 1, wherein a surface energy of the surfactant material is smaller than a surface energy of the p-type nitride semiconductor layer and / or the p-type electrode. The p-side electrode is made of Ag,
The surfactant materials are Y, La, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Zn, Al, Ga, In, Tl, Ge, Sn, Pb, Cd, Hg, As, Sb. The method for producing a nitride semiconductor light emitting device according to claim 2, comprising at least one element selected from the group consisting of Bi and Bi. The p-side electrode is made of Pd, Ni or Pt,
The surfactant material is Sc, Mn, Cu, Y, La, Au, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Zn, Al, Ga, In, Tl, Si, Ge, Sn. The method for producing a nitride semiconductor light-emitting element according to claim 2, comprising at least one element selected from the group consisting of Pb, Cd, Hg, As, Sb, and Bi.   5. The method for manufacturing a nitride semiconductor light emitting element according to claim 1, wherein the surfactant substance is brought into contact with the surface of the p-type nitride semiconductor layer in a growth interruption step immediately before growing the p-side electrode.   The manufacturing method of the nitride semiconductor light-emitting device according to any one of claims 1 to 4, wherein a surfactant substance is brought into contact with the surface of the p-side electrode during the growth of the p-side electrode.   The surface active material is in contact with the surface of the p-type nitride semiconductor layer or the surface of the p-side electrode during the growth using metal organic vapor phase epitaxy, sputtering, or vacuum deposition. The manufacturing method of the nitride semiconductor light-emitting device of description.   The manufacture of the nitride semiconductor light emitting device according to any one of claims 1 to 7, wherein the surfactant substance is added in an amount of 3 ML or less on the surface of the p-type nitride semiconductor layer or the surface of the p-side electrode during the growth. Method.   The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, further comprising a step of performing an annealing process after the step of bringing the surfactant material into contact.

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