JP2004214405A - Light emitting device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance and inexpensive ultraviolet or blue emitting device capable of surely forming a p-type layer constituted of MgZnO with high quality. <P>SOLUTION: In a light emitting device 1, a light emitting layer 24 is provided with a p-type oxide layer 34 and an n-type oxide layer 32, and the p-type oxide layer 34 is constituted of a p-type Mg<SB>x</SB>Zn<SB>1-x</SB>O (written briefly also MgZnO: 0<x≤1) layer containing an auxiliary metallic element constituted of N, and at least one kind out of V, Nb and Ta of group 5A elements, or at least one kind out of Li, Na and K of group 1A elements. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a light-emitting element using a semiconductor, particularly a light-emitting element suitable for emitting blue light or ultraviolet light.
[0002]
[Prior art]
[Patent Document 1]
JP 2001-0444500 A
[Patent Document 2]
JP 2001-048698 A
[Patent Document 3]
JP-A-2002-016088
[Patent Document 4]
JP-A-2002-093821
[Patent Document 5]
JP 2002-105625 A
[Patent Document 6]
JP-A-2002-076026
[Patent Document 7]
JP-A-2002-289918
[0003]
There has long been a demand for a high-luminance light-emitting element that emits light of a short wavelength in the blue light region. Recently, such a light-emitting element has been realized by using an AlGaInN-based material. Further, application to a full-color light-emitting device, a display device, and the like by combining with a red or green high-luminance light-emitting element is also rapidly progressing. However, since the AlGaInN-based material mainly contains Ga and In, which are relatively rare metals, it is unavoidable to increase the cost. Another major problem is that the growth temperature is as high as 700 ° C. to 1000 ° C., and considerable energy is consumed during manufacturing. This is undesirable not only from the viewpoint of cost reduction, but also in the sense that it goes against the trend in recent years when discussions on energy saving and global warming control are intense. Therefore, Patent Literatures 1 to 7 propose light-emitting elements in which a light-emitting layer portion is formed on a sapphire substrate by a less expensive ZnO-based compound semiconductor layer.
[0004]
[Problems to be solved by the invention]
Incidentally, the ZnO layer is obtained by vapor phase growth in a vacuum atmosphere. However, since oxygen deficiency is very likely to occur, the conductivity type is necessarily n-type, and n-type carriers (electrons) as conductive carriers are few. There is a problem in that it is difficult to obtain crystals. On the other hand, when producing the electronic device disclosed in the above publication using ZnO, it is essential to obtain a material having a p-type conductivity. However, as described above, the conductivity type of the oxide crystal tends to be n-type due to the presence of oxygen vacancies, and it is difficult even to form a semi-insulating crystal close to an intrinsic semiconductor. With respect to the method of forming p-type ZnO, the method of simultaneously doping N and Ga disclosed in Patent Documents 2, 5, and 7, the method of doping As as disclosed in Patent Document 3, or the method of Patent Document 3, Although there is a method of doping the radical N disclosed in No. 6, there are many problems such as the ineffective entry of the dopant and the poor reproducibility.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a high-performance and inexpensive ultraviolet or blue light-emitting type light emitting element capable of reliably forming a p-type layer made of MgZnO with high quality, and a method of manufacturing the same.
[0006]
[Means for Solving the Problems and Functions / Effects]
In order to solve the above problems, the light emitting device of the present invention is
A light-emitting layer portion having a p-type oxide layer and an n-type oxide layer, wherein the p-type oxide layer is composed of N and a group 5A element composed of at least one of V, Nb and Ta at a lower concentration than N; Or p-type Mg containing a lower concentration of N than an auxiliary metal element consisting of a Group 1A element comprising at least one of Li, Na and K _x Zn _1-x O (hereinafter also referred to as MgZnO; provided that 0 <x ≦ 1).
[0007]
In order for MgZnO to be p-type, it is necessary to add an appropriate p-type dopant. It is effective to use a group V element as a p-type dopant of MgZnO, which is a group II-VI compound semiconductor. The group V element generates holes which are p-type carriers by substituting O which is a group VI element. Among them, it is considered that the use of N whose ionic radius is close to that of O is effective in obtaining good p-type characteristics. However, it is known that it is technically very difficult to dope MgZnO with N alone. For example, when MgZnO is vapor-phase grown by MOVPE, a gas serving as an N source together with an organic metal is simultaneously added. Even if supplied, N is hardly doped into MgZnO.
[0008]
However, the present inventors have examined that the p-type oxide layer is formed of N, a group 5A element composed of one or more of V, Nb, and Ta at a lower concentration than N, or a Li at a lower concentration than N, By forming a p-type MgZnO layer containing an auxiliary metal element comprising a Group 1A element of at least one of Na and K, it is newly found that N is efficiently doped into MgZnO, and the present invention is completed. Reached. As a result, a p-type layer made of MgZnO can be reliably formed with high quality, and a high-performance and inexpensive ultraviolet or blue light-emitting element can be realized.
[0009]
The auxiliary metal element functions as a doping auxiliary element for smoothly doping N, which is a p-type dopant, into MgZnO. Even in a very small amount, the auxiliary metal element sufficiently exerts an effect of introducing sufficient N into MgZnO. I do. However, excessive addition of the auxiliary metal element may rather deteriorate the semiconductor characteristics of MgZnO, or may diffuse into adjacent semiconductor layers and adversely affect the semiconductor properties. The auxiliary metal element has a lower concentration than N to be doped. The N concentration in the p-type MgZnO layer is 1 × 10 ¹⁷ / Cm ³ More than 1 × 10 ¹⁹ / Cm ³ The auxiliary metal element concentration is preferably 5 × 10 ¹⁴ / Cm ³ More than 1 × 10 ¹⁷ / Cm ³ It is better to be less than.
[0010]
The auxiliary metal element is preferably a group 5A element composed of at least one of V, Nb and Ta in order to obtain a more remarkable N-doping promoting effect in MgZnO, and it is particularly effective to use Ta. It is.
[0011]
It is desirable that the p-type oxide layer contains H together with N and the auxiliary metal element from the viewpoint of more stably obtaining a p-type layer made of MgZnO. When doping N into MgZnO, it is difficult to activate N alone as an acceptor. Therefore, when H is simultaneously mixed, N is activated and stabilized as an acceptor, and p-type carriers can be generated efficiently and stably. In this case, it is effective to make the p-type oxide layer contain H at a concentration equal to or higher than the N concentration. From this viewpoint, the H concentration in the p-type MgZnO layer is 5 × 10 ¹⁷ / Cm ³ 5 × 10 or more ²⁰ / Cm ³ It is better to do the following.
[0012]
The light emitting layer is made of Mg _x Zn _1-x An O (where 0 <x ≦ 1) p-type cladding layer as a p-type oxide layer; _y Zn _1-y An active layer made of O (where 0 <y ≦ 1); _z Zn _1-z When an n-type cladding layer made of O (where 0 <z ≦ 1) is configured to have a double hetero structure in which the n-type cladding layers are stacked in this order, it is effective in realizing an element having high emission intensity.
[0013]
Next, the method for manufacturing a light emitting device of the present invention is the method for manufacturing a light emitting device of the present invention, wherein the p-type oxide layer and the n-type oxide layer are epitaxially grown on a growth substrate, and The oxide layer is made of N and a Group 5A element composed of at least one of V, Nb and Ta at a lower concentration than N or a Group 1A element composed of at least one of Li, Na and K at a concentration lower than N. -Type Mg containing an auxiliary metal element _x Zn _1-x It is characterized by being grown as an O (0 <x ≦ 1) layer. The p-type oxide layer is formed of N and a Group 5A element composed of at least one of V, Nb and Ta at a lower concentration than N or a Group 1A composed of at least one of Li, Na and K at a concentration lower than N. By forming a p-type MgZnO layer containing an auxiliary metal element made of an element, N can be efficiently doped into MgZnO, and a p-type layer made of MgZnO can be reliably formed with high quality.
[0014]
In the light emitting device of the present invention, the p-type Mg _a Zn _1-a The O layer can be formed by a metal organic chemical vapor deposition method (MOVPE method) or a molecular beam epitaxy method (Molecular Beam Epitaxy: MBE method). The use of the MOVPE method has the following advantages. In the MOVPE method, the oxygen partial pressure during growth can be freely changed. Therefore, by increasing the atmospheric pressure to some extent, it is possible to effectively suppress the desorption of oxygen and the occurrence of oxygen deficiency. As a result, p-type Mg _a Zn _1-a O layer, particularly, oxygen deficiency concentration of 10 / cm ³ The following p-type Mg _a Zn _1-a An O layer can be realized. The lower the oxygen deficiency concentration, the better (ie, 0 / cm ³ Does not prevent that)
[0015]
The growth of the p-type cladding layer or the active layer by the MOVPE method is 10 Torr (1.3 × 10 ³ By performing the reaction in an atmosphere having a pressure of Pa) or more, generation of oxygen deficiency during film formation can be more effectively suppressed, and a p-type clad layer or an active layer having good characteristics can be obtained. In this case, more preferably, the oxygen partial pressure (O ₂ Oxygen containing molecules other than ₂ Into 10 Torr (1.3 × 10 ³ Pa) or more.
[0016]
On the other hand, when the MBE method is used, an ultra-high vacuum (-10 to ^-10 Since the growth of the p-type cladding layer or the active layer is performed in Torr), the generation of oxygen vacancies cannot be suppressed as compared with the MOVPE method, but there is an advantage that the layer can be controlled on the order of the atomic layer. As a result, it is possible to increase the crystallinity of the p-type cladding layer or the active layer.
[0017]
p-type Mg _x Zn _1-x When the O layer is grown by metal organic chemical vapor deposition or MBE, Mg _x Zn _1-x It is desirable to supply the organic metal as the raw material of O together with the gas as the N source. By doing so, H in the organometallic molecule is taken into MgZnO, and the effect of promoting N doping by the gas serving as the N source is enhanced. In this case, the gas serving as the N source is N ₂ O or NO is desirable. N ₂ O or NO is a p-type dopant source, functions as an O source for MgZnO, and is an oxidizing compound gas. ₂ Excessive reaction with an organic metal is suppressed as compared with the case of using a gas, and there is an advantage that an MgZnO layer can be formed with higher quality.
[0018]
In order to dope the p-type MgZnO layer with N at a necessary and sufficient concentration, it is essential to supply an auxiliary metal element source to the MgZnO layer. In this case, Mg _x Zn _1-x By adopting a method of supplying a gas serving as an auxiliary metal element source together with an organic metal serving as a raw material of O and a gas serving as an N source, N is uniformly and efficiently doped into a MgZnO layer grown by a gas phase reaction. It is desirable because it can be.
[0019]
In this case, the gas serving as the auxiliary metal element source can of course be supplied in the form of an organic metal. However, the amount of the auxiliary metal element added to the p-type MgZnO layer may be small as described above, so that a less expensive auxiliary metal element may be used. Sources can also be used. For example, the gas serving as the auxiliary metal element source is p-type Mg. _x Zn _1-x A method of evaporating and supplying from a solid auxiliary metal element source disposed in a reaction vessel for growing an O layer can be adopted. As a result, the auxiliary metal element can be supplied at a lower cost than in the case of using an organic metal, and even in the case of a solid auxiliary metal element source in which the vapor pressure of the auxiliary metal element cannot be secured so high, the addition amount itself is as described above. Since a small amount is sufficient, it can be fully utilized. Specifically, the solid auxiliary metal element source can use an oxide of the auxiliary metal element. The metal oxide is inexpensive, and even if it is an auxiliary metal element for which synthesis of an organic metal is difficult, it can be easily obtained as long as it is a metal oxide, which contributes to a reduction in manufacturing cost.
[0020]
Another method is to use p-type Mg. _x Zn _1-x Prior to growing the O layer on the growth substrate, a concentrated portion of the auxiliary metal element is formed on the main surface of the growth substrate, and p-type Mg is formed on the main surface. _x Zn _1-x While growing the O layer, the p-type Mg _x Zn _1-x Diffusion into the O layer is also possible, and an amount of auxiliary metal element sufficient to promote N doping can be easily introduced into the MgZnO layer.
[0021]
The concentrated portion of the auxiliary metal element can be, for example, a solid auxiliary metal element source (for example, an oxide of the above-described auxiliary metal element) applied or deposited on the main surface of the growth substrate. In the case of coating, a solution in which the solid auxiliary metal element source powder is suspended is applied to the main surface of the growth substrate, and the solvent is evaporated, so that the attached auxiliary metal element source powder is used as the above-described concentrated portion Can be used. On the other hand, the volume of the solid auxiliary metal element source on the main surface of the growth substrate can be determined by vapor deposition or sputtering, and a thin layer of the solid auxiliary metal element source may be formed on the main surface of the growth substrate. In order to keep the amount of the auxiliary metal element introduced into the MgZnO layer to a very small amount and not to hinder the epitaxial growth of the MgZnO layer on the growth substrate, the amount of the powder or thin layer attached to the main surface of the growth substrate is: It is desirable to make adjustment so that at least half of the main surface of the growth substrate is exposed.
[0022]
On the other hand, the concentrated portion of the auxiliary metal element may be a diffusion concentrated layer of the auxiliary metal element formed in advance on the surface layer portion including the main surface of the growth substrate. According to this method, even if a diffusion-enriched layer of the auxiliary metal element is formed, the crystal structure itself of the surface layer of the growth substrate is maintained, so that the epitaxial growth of the MgZnO layer on the growth substrate can be performed more smoothly.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 schematically shows a main part of a light emitting element 1 according to an embodiment of the present invention in a laminated structure. _x Zn _1-x An O (where 0 <x ≦ 1) p-type cladding layer 34 as a p-type oxide layer; _y Zn _1-y An active layer 33 of O (0 <y ≦ 1); _z Zn _1-z An n-type cladding layer 32 made of O (where 0 <z ≦ 1) has a light emitting layer portion 24 having a double hetero structure, which is stacked in this order. In the present embodiment, the light emitting layer section 24 is heteroepitaxially grown on the sapphire substrate 10 as a growth substrate from the p-type cladding layer 34 side via the ZnO buffer layer 11. However, as shown in FIG. 5, the stacking order may be reversed.
[0024]
Returning to FIG. 1, the main surface of the n-type cladding layer 32 is covered with a transparent electrode layer 35 made of a conductive oxide. In the present embodiment, the transparent electrode layer 35 is an ITO (Indium Tin Oxide) electrode 35, but a ZnO-based transparent electrode (for example, Al ²⁰ / Cm ³ An amorphous ZnO transparent electrode doped to a certain degree may be used.
[0025]
Further, a metal electrode 22 made of a metal such as Al / Ti, In, or Au is disposed substantially in the center of the transparent electrode layer 35 so as to cover a part thereof. A current-carrying electrode wire (not shown) is joined to the metal electrode 22. On the other hand, a part of the n-type cladding layer 32 and the active layer 33 is removed, and a transparent electrode layer 25 similar to the transparent electrode layer 35 is formed on the exposed surface of the p-type cladding layer 34 to cover a part thereof. A metal electrode 122 is formed in the shape.
[0026]
MgZnO has a wurtzite structure, in which an oxygen atom layer and a metal atom (Zn ion or Mg ion) layer are alternately stacked in the c-axis direction. Each of the layers 34, 33, 32 is grown in the c-axis direction. When oxygen ions are lost in the MgZnO crystal, oxygen vacancies occur and n-type carriers (electrons) are generated. Oxygen deficiency is not harmful in the n-type cladding layer 32 if it is in an appropriate amount, but rather can be actively utilized as an n-type carrier source. On the other hand, if too many oxygen vacancies are formed in the p-type cladding layer 34 and the active layer 33, the number of n-type carriers increases and the p-type cladding layer 34 and the active layer 33 do not exhibit p-type conductivity or intrinsic semiconductor characteristics. is important.
[0027]
The n-type cladding layer 32 has an n-type carrier concentration of, for example, 1 × 10 3 so that the radiative recombination in the active layer 33 is optimized. ¹⁷ / Cm ³ More than 1 × 10 ¹⁹ / Cm ³ It is adjusted within the following range. As the n-type dopant, one or two or more of B, Al, Ga and In can be added. However, the dopant can be made non-added by positively forming an oxygen vacancy serving as an n-type carrier (electron) source. .
[0028]
On the other hand, N is added to the p-type cladding layer 34 as a p-type dopant, and furthermore, the p-type cladding layer 34 is made of a Group 5A element composed of at least one of Nb and Ta or a Group 1A element composed of at least one of Li, Na and K. An auxiliary metal element (Ta in this embodiment) is added. N concentration is 1 × 10 ¹⁷ / Cm ³ More than 1 × 10 ¹⁹ / Cm ³ Below, preferably 5 × 10 ¹⁷ Pieces / cm ³ 5 × 10 or more ¹⁸ / Cm ³ It is adjusted within the following range. The auxiliary metal element is added at a concentration lower than the N concentration, and the concentration is, for example, 5 × 10 ¹⁴ / Cm ³ More than 1 × 10 ¹⁷ / Cm ³ It is adjusted within the range of less than. Further, the p-type cladding layer 34 contains H together with N and the auxiliary metal element. H has a higher concentration than any of N and the auxiliary metal element. ¹⁸ / Cm ³ 5 × 10 or more ²⁰ / Cm ³ The density is adjusted within the following range.
[0029]
The active layer 33 has an appropriate band gap according to a required emission wavelength. For example, a material used for visible light emission has a band gap energy Eg (about 3.10 eV to 2.18 eV) capable of emitting light at a wavelength of 400 nm to 570 nm. This is an emission wavelength band covering from violet to green. In particular, when used for blue emission, the band gap energy Eg (about 2.76 eV to 2.48 eV) capable of emitting light at a wavelength of 450 nm to 500 nm is used. Choose what you have. In addition, a material having a band gap energy Eg (approximately 4.43 eV to 3.10 eV) capable of emitting light at a wavelength of 280 nm to 400 nm is selected as a material used for ultraviolet light emission.
[0030]
In the active layer 33, the value of the mixed crystal ratio y also serves as a factor that determines the band gap energy Eg. For example, when ultraviolet light having a wavelength of 280 nm to 400 nm is to be emitted, the selection is made in the range of 0 ≦ y ≦ 0.5. The band edge discontinuity formed between the cladding layers 32 and 34 on both sides is about 0.1 eV to 0.3 eV for a light emitting diode and about 0.25 eV to 0.5 eV for a semiconductor laser light source. Is good. This value corresponds to the p-type cladding layer (composition: Mg _x Zn _1-x O) 34, active layer (composition: Mg) _y Zn _1-y O) 33 and n-type cladding layer (composition: Mg) _z Zn _1-z O) It can be determined by selecting numerical values of the respective mixed crystal ratios x, y, and z of the layer 32.
[0031]
Hereinafter, an example of a manufacturing process of the light emitting device will be described. First, a buffer layer 11 made of ZnO is epitaxially grown on a sapphire substrate 10. Next, the p-type cladding layer 34, the active layer 33, and the n-type cladding layer 32 are epitaxially grown in this order (Step 2 in FIG. 2). These layers can be epitaxially grown by the MOVPE method or the MBE method described above. Hereinafter, the case of the MOVPE method will be described.
[0032]
By the MOVPE method, the buffer layer 11, the p-type cladding layer 34, the active layer 33, and the n-type cladding layer 32 can be continuously grown in the same reaction vessel. The temperature in the reaction vessel is adjusted by a heating source (in the present embodiment, an infrared lamp) in order to promote a chemical reaction for forming a layer. The following can be used as the main raw material of each layer.
Oxygen source gas: Oxygen gas can be used, but it is preferable to supply it in the form of an oxidizing compound gas from the viewpoint of suppressing an excessive reaction with an organic metal described later. Specifically, N ₂ O, NO, NO ₂ , CO, etc. In the present embodiment, N ₂ O (nitrous oxide) is used. This gas also functions as an N source gas that is a p-type dopant source.
-Zn source gas: dimethyl zinc (DMZn), diethyl zinc (DEZn) and the like.
-Mg source gas: biscyclopentadienyl magnesium (Cp ₂ Mg).
[0033]
On the other hand, the n-type cladding layer 32 may be configured to obtain n-type conductivity by lowering the oxygen partial pressure during growth and positively forming oxygen vacancies, or a group III such as B, Al, Ga and In. N-type conductivity may be obtained by adding an element alone as an n-type dopant. As Al, Ga and In, the dopant gas described in the paragraph of the p-type dopant can be similarly used. As for B, for example, diborane (B ₂ H ₆ ) Can be used.
[0034]
Each of the above source gases is converted into a carrier gas (for example, N ₂ Gas) and supply it into the reaction vessel. The flow ratio of the organic metal gas MO serving as a Mg source and a Zn source is controlled for each layer by a mass flow controller MFC or the like according to the difference in the mixed crystal ratio of each layer. Further, the oxygen source gas N ₂ The flow rates of O and the dopant source gas are also controlled by the mass flow controller MFC.
[0035]
The growth of the buffer layer 11 is performed, for example, as follows. First, the substrate 10 on which a layer is grown is a sapphire (i.e., alumina single crystal) substrate having a crystal main axis of c-axis, and the main surface on the oxygen atom side is used as a layer growth surface. The growth is performed by using an organic metal gas MO and an oxygen source gas N. ₂ O is supplied into the reaction vessel, for example, at 400 ° C. by the ordinary MOVPE method. N ₂ O contains N, but at this stage, by preventing the auxiliary metal element source from being present in the atmosphere, the incorporation of N into the buffer layer 11 can be suppressed.
[0036]
When the growth of the buffer layer 11 is completed, the p-type cladding layer 34, the active layer 33, and the n-type cladding layer 32 forming the light emitting layer portion 24 are formed in this order by MOVPE. The growth temperature of the light emitting layer portion 24 is, for example, 700 ° C. or more and 1000 ° C. or less (800 ° C. in the present embodiment).
[0037]
First, as shown in Step 1 of FIG. 2, a p-type cladding layer 34 is provided in a reaction vessel with an organic metal as a raw material of MgZnO and N as a gas as an N source (and an oxygen source). ₂ It grows by supplying a gas that serves as an auxiliary metal element source together with O. In the present embodiment, the gas serving as the auxiliary metal element source is vaporized and supplied from the solid auxiliary metal element source disposed in the reaction vessel. In this embodiment, the solid auxiliary metal element source is an oxide of the auxiliary metal element (Ta). ₂ O ₅ ) Is used. Note that it is also possible to use a single metal of the auxiliary metal element (for example, Ta metal). N which is N source gas ₂ O is an oxidizing gas. When the p-type cladding layer 34 made of the MgZnO layer is grown by the MOVPE method in the above-mentioned temperature range under the oxidizing gas atmosphere, the auxiliary metal element Ta is reacted from the solid auxiliary metal element source. Evaporation into the atmosphere of the container causes Ta to be effectively diffused into the growing MgZnO layer, and the effect of Ta diffusion promotes doping of N into the MgZnO layer. The solid auxiliary metal element source may be heated together with the sapphire substrate (growth substrate) 10.
[0038]
Prior to growing the p-type cladding layer 34 on the sapphire substrate (growth substrate) 10, a concentrated portion of the auxiliary metal element is formed on the main surface of the growth substrate, and the p-type cladding layer 34 is formed on the main surface. While growing, the auxiliary metal element can be diffused into the p-type cladding layer 34 from the concentrated portion. As shown in FIG. 3, the enriched portion of the auxiliary metal element can be, for example, a solid auxiliary metal element source 60 applied or vapor-phase grown on the main surface of the sapphire substrate 10. In this embodiment, an auxiliary metal element oxide powder (Ta) as a solid auxiliary metal element source powder is used. ₂ O ₅ ) Is applied to the main surface of the sapphire substrate 10 and the solvent is evaporated to form powder particles to form a concentrated portion. On the other hand, a thin layer of the auxiliary metal element oxide powder may be formed on the main surface of the growth substrate, for example, in an island shape by vapor deposition or sputtering. The adhesion amount of the auxiliary metal element oxide powder or the thin layer to the main surface of the substrate is adjusted so that at least half of the main surface of the substrate is exposed. The buffer layer 11 made of MgZnO is epitaxially grown on the exposed region of the main surface of the substrate. However, as long as the amount of powder or thin layer adhered is very small, the buffer layer 11 becomes larger in the main surface of the substrate as the thickness increases. Since the MgZnO single crystal main surface with few crystal defects can be formed by growing in the direction (so-called lateral direction) and covering the attached powder or thin layer, there is no fear of hindering the growth of the light emitting layer portion thereafter.
[0039]
Further, as shown in FIG. 4, the concentrated portion of the auxiliary metal element may be a diffusion concentrated layer 61 of the auxiliary metal element formed in advance on the surface layer including the main surface of the growth substrate. The diffusion-concentrating layer 61 is formed by, for example, forming a thin layer of an auxiliary metal element oxide on the sapphire substrate 10 by sputtering, vapor deposition, or a sol-gel method, and then performing a heat treatment at an appropriate temperature to diffuse the auxiliary metal element to the substrate side. The auxiliary metal element oxide layer may be removed by etching or the like. Further, by encapsulating the substrate in an atmosphere heat treatment furnace together with the solid auxiliary metal element source and heating, the auxiliary metal element may be evaporated from the solid auxiliary metal element source and diffused from the main surface of the substrate to the surface layer region.
[0040]
Next, the active layer 33 is grown in such a manner that the solid auxiliary metal element source is not disposed in the reaction vessel, or even when the solid auxiliary metal element source is disposed in the reaction vessel, the evaporation of the auxiliary metal element is suppressed. In the former case, the reaction vessel is divided into a first reaction chamber in which the solid auxiliary metal element source is disposed and a second reaction chamber in which the solid auxiliary metal element source is not disposed, and the growth substrate is movable between the two chambers, and the auxiliary metal element is evaporated. It suffices that growth and growth without evaporation are performed sequentially. On the other hand, in the latter case, the temperature of the solid auxiliary metal element source can be changed by adjusting the power of the lamp heating to change the growth atmosphere temperature itself. It is also possible to separate the heating source between the solid auxiliary metal element source and the growth substrate, and to adjust the temperature of the solid auxiliary metal element source independently of the growth substrate by a unique heating source. Note that the active layer 33 is required to have intrinsic semiconductor type characteristics. However, if the active layer 33 tends to have n-type characteristics due to oxygen deficiency, dope N with a smaller doping amount than that of the p-type cladding layer. Thus, intrinsic semiconductor type characteristics may be obtained by compensating for n-type carriers.
[0041]
FIG. 6 illustrates a result of SIMS analysis in the growth depth direction of the MgZnO layer grown by MOVPE by the above method. The N concentration is highest on the surface of the layer. After the concentration once decreases in the depth direction at the surface layer portion, the concentration is substantially constant at a certain depth or higher (1 × 10 ¹⁸ / Cm ³ ) Has stabilized. Correspondingly, it can be seen that Ta also shows a concentration distribution of exactly the same tendency, and that the auxiliary doping of Ta plays an important role in the doping of N. H, which is considered to be derived from an organic metal, has a similar concentration distribution. The MgZnO layer thus obtained was found to exhibit good p-type conductivity as a result of Hall effect measurement. For comparison, Ta, which is a solid auxiliary metal element source, is used. ₂ O ₅ The same analysis was performed on the MgZnO layer grown without disposing the sintered body of No. 1 in the reaction vessel. ^Fifteen / Cm ³ It was extremely low as follows, and naturally showed no p-type conductivity.
[0042]
When growing the active layer 33 and the p-type cladding layer 34, it is effective to maintain the pressure in the reaction vessel at 10 Torr or more in order to suppress the generation of oxygen vacancies. Thereby, the desorption of oxygen is further suppressed, and a MgZnO layer with less oxygen deficiency can be grown. In particular, N ₂ When using O, N ₂ The dissociation of O is prevented from progressing rapidly, and the generation of oxygen deficiency can be more effectively suppressed. The higher the atmospheric pressure is, the higher the effect of suppressing oxygen desorption is. However, 760 Torr (1.01 × 10 ⁵ Even at a pressure up to about Pa or 1 atm), the effect is sufficiently significant. For example, if the pressure is 760 Torr or less, the inside of the reaction vessel is at normal pressure or reduced pressure, so that there is an advantage that the vessel sealing structure can be relatively simple. On the other hand, when a pressure exceeding 760 Torr is adopted, the inside of the container is pressurized, so that a somewhat strong sealing structure is used so that the gas inside does not leak out. However, the effect of suppressing oxygen desorption is more remarkable. In this case, the upper limit of the pressure should be set to an appropriate value in consideration of the cost of the apparatus and the achievable effect of suppressing oxygen desorption (for example, 7600 Torr ((1.01 × 10 ⁶ Pa or 10 atm)).
[0043]
When the growth of the light emitting layer is completed in this way, as shown in FIG. 1, a part of the active layer 33 and a part of the n-type MgZnO layer 32 are partially removed by photolithography or the like, and furthermore, the transparent electrode layers 35 and 25 and If the metal electrode layers 22 and 122 are formed and then diced with the substrate 10, the light emitting device 1 is obtained. The light extraction of the light emitting element 1 is mainly performed from the transparent sapphire substrate 10 side.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a specific example of a light emitting element of the present invention in a laminated structure.
FIG. 2 is an explanatory view of a manufacturing process of the light emitting device of FIG.
FIG. 3 is a diagram showing a first modified example of a part of the process in FIG. 2;
FIG. 4 is a diagram showing a second modified example.
FIG. 5 is a schematic view showing a modified example of the light emitting element of FIG. 1 in a laminated structure.
FIG. 6 is a view showing an experimental result for confirming the effect of the present invention.
[Explanation of symbols]
1 Light-emitting element
10 Sapphire substrate (growth substrate)
32 n-type cladding layer
33 Active Layer
34 p-type cladding layer

Claims (16)

A light-emitting layer portion having a p-type oxide layer and an n-type oxide layer, wherein the p-type oxide layer is composed of N and a group 5A element composed of at least one of V, Nb and Ta at a lower concentration than N; Or from a p-type Mg _x Zn _1-x O (0 <x ≦ 1) layer containing an auxiliary metal element consisting of a Group 1A element composed of at least one of Li, Na and K lower than N. A light-emitting element, comprising: The light emitting device according to claim 1, wherein the auxiliary metal element is a Group 5A element composed of at least one of V, Nb, and Ta. The light emitting device according to claim 2, wherein the group 5A element is Ta. The light emitting device according to claim 1, wherein the p-type oxide layer contains N and H together with the auxiliary metal element. 5. The light emitting device according to claim 4, wherein the p-type oxide layer contains H at a concentration equal to or higher than the N concentration. The light emitting layer portion includes a p-type clad layer as the p-type oxide layer composed of a layer of Mg _x Zn _1-x O (where 0 <x ≦ 1), and Mg _y Zn _1-y O (where 0 <Y ≦ 1) and an n-type clad layer made of Mg _z Zn _1-z O (0 <z ≦ 1) having a double hetero structure in this order. The light emitting device according to any one of claims 1 to 5, wherein The method for manufacturing a light emitting device according to claim 1, wherein a p-type oxide layer and an n-type oxide layer are epitaxially grown on a growth substrate, and the p-type oxide layer is formed. An auxiliary metal consisting of N and a Group 5A element composed of at least one of V, Nb and Ta at a concentration lower than N or a Group 1A element composed of at least one of Li, Na and K at a concentration lower than N A method for manufacturing a light-emitting element, comprising growing as a p-type Mg _x Zn _1-x O (where 0 <x ≦ 1) layer containing an element. Method of manufacturing a light emitting device according to claim 7, wherein the forming by the p-type Mg x _Zn 1-x _O layer metal-organic chemical vapor deposition or molecular beam epitaxy. When the p-type Mg _x Zn _1-x O layer is grown by metal organic chemical vapor deposition or molecular beam epitaxy, an organic metal serving as a raw material of Mg _x Zn _1-x O is mixed with a gas serving as an N source. 9. The method for manufacturing a light emitting device according to claim 8, wherein the supply is performed. The method according to claim 9, wherein the N source gas is N ₂ O or NO. 11. The light-emitting element according to claim 9, wherein the gas serving as the auxiliary metal element source is supplied together with the organic metal serving as the raw material of the Mg _x Zn _1-x O and the gas serving as the N source. 12. Method. Claim wherein the auxiliary metal source to become gas, which is characterized in that evaporating supplied from the p-type Mg x _Zn 1-x _O layer solid auxiliary metal source which is placed in a reaction vessel for growing 12. The method for manufacturing a light emitting device according to item 11. The method according to claim 12, wherein the solid auxiliary metal element source comprises an oxide of the auxiliary metal element. Prior to growing the p-type Mg _x Zn _1-x O layer on the growth substrate, a concentrated portion of the auxiliary metal element is formed on a main surface of the growth substrate, and the p-type Mg is formed on the main surface. 11. The light emission according to claim 9, wherein while growing an _x Zn _1-x O layer, the auxiliary metal element is diffused from the enriched portion to the p-type Mg _x Zn _1-x O layer. 12. Device manufacturing method. 15. The method according to claim 14, wherein the auxiliary metal element enriched portion is a solid auxiliary metal element source applied or deposited on a main surface of the growth substrate. 15. The light emitting device according to claim 14, wherein the concentrated portion of the auxiliary metal element is a diffusion-concentrated layer of the auxiliary metal element formed in advance on a surface portion including the main surface of the growth substrate. Method.

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