JP2013120847A - Red light-emitting semiconductor device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a red light-emitting semiconductor device capable of increasing light-emitting transition efficiency of Eu ions and Pr ions, and having good emission intensity, and a method for manufacturing the same.SOLUTION: In a method for manufacturing a red light-emitting semiconductor device using mixed crystal containing GaN, InN, AlN or two or more of these metals, when an active layer in which Eu or Pr is added thereto so as to substitute with Ga, In or Al, under a temperature condition of 900 to 1100°C using the organic metal vapor phase epitaxial method and using mixed crystal containing GaN, InN, AlN or two or more of these metals as a parent material, is formed between a p-type layer and an n-type layer, in the series of forming steps including forming the p-type layer and the n-type layer, Eu or Pr and Mg or Al are added.

Description

  The present invention relates to a red light emitting semiconductor element and a method for manufacturing the same, and more specifically, an active layer in which Eu or Pr is added to a specific base material (base material) such as GaN, InN, or AlN is divided into an n-type layer and a p-type layer. The present invention relates to a red light emitting semiconductor element having excellent light emission characteristics provided therebetween and a method for manufacturing the same.

  Nitride semiconductors such as gallium nitride (GaN) are attracting attention as semiconductor materials for blue light-emitting devices, and in recent years, by adding high concentrations of indium (In) to GaN, green and red light-emitting devices can be obtained. It is expected to be realized. However, as the In composition becomes higher, fluctuations in the In composition and piezo electric field effects become more prominent, so that a red light emitting device using a nitride semiconductor has not been realized.

  On the other hand, paying attention to the wide gap of nitride semiconductors, semiconductors to which europium (Eu) or praseodymium (Pr) is added with GaN as an additive base are promising as red light emitting devices.

  Under such circumstances, the present inventors succeeded in realizing a red light emitting diode (LED) having Eu or Pr-doped GaN as an active layer for the first time in the world (Patent Document 1).

  And by realizing such a red light emitting diode, it is possible to integrate light primary diodes of light using a nitride semiconductor on the same substrate together with the blue light emitting diode and the green light emitting diode that have already been developed. Therefore, application to fields such as a small and high-definition full-color display and LED lighting to which light emission in a red region not included in the current white LED is added is expected.

  However, the light output of the red light-emitting diode described above is currently limited to about 50 μW, and further improvement in light emission intensity (light output) is required for practical use.

  In order to improve the light output, it is essential to increase the light emission transition probability of Eu ions and Pr ions which are the emission centers of the active layer. However, the emission of Eu ions and Pr ions is due to the transition in the 4f shell, and the transition in the 4f shell of these rare earth elements is a forbidden transition. Therefore, in order to increase the probability of luminescence transition and obtain a high luminescence intensity, It is necessary to reduce the symmetry of the local local structure of Eu ions and Pr ions in the crystal field by incorporating Eu and Pr into the crystal.

  However, when Eu or Pr is simply added, it cannot be said that the symmetry of the peripheral local structure of Eu ions or Pr ions is sufficiently low, and the emission intensity (light output) is kept low.

  Therefore, if the peripheral local structure of Eu ions and Pr ions can be controlled by intentionally co-adding impurities other than Eu and Pr, high emission intensity (light output) by Eu ions and Pr ions can be realized. there is a possibility.

  For example, Non-Patent Document 1 reports that Eu and Si co-doped GaN with high emission intensity can be obtained by intentionally co-adding Si during the production of Eu-doped GaN. However, such high emission intensity is obtained only when the Si concentration is about 0.06 atomic%, and the emission intensity is not sufficient.

  As described above, some attempts have been made to improve the emission luminance by adding impurities (co-added impurities), but the influence of the addition of impurities on the emission luminance has not been fully elucidated.

WO2010 / 128643 A1 publication

R. Wang, A .; J. et al. Stickle, E .; E. Brown, U.D. Homerich, and J.H. M.M. Zavada, “Effect of Si Coding on Eu3 + luminescence in GaN”, J. Am. Appl. Phys. 105, 043107 (2009).

  In view of the above-described problems in the prior art, an object of the present invention is to provide a red light-emitting semiconductor element having excellent emission intensity and a method for manufacturing the same, by increasing the light emission transition efficiency of Eu ions and Pr ions. .

  As a result of intensive studies, the present inventor has found that the above problems can be solved by the invention shown in the following claims, and has completed the present invention.

The invention described in claim 1
A method of manufacturing a red light emitting semiconductor device using GaN, InN, AlN or a mixed crystal of any two or more thereof,
Using GaN, InN, AlN, or a mixed crystal of any two or more thereof as a base material, Eu or Pr is changed to Ga, In under a temperature condition of 900 to 1100 ° C. using a metal organic vapor phase epitaxial method. Alternatively, when the active layer added so as to replace Al is formed between the p-type layer and the n-type layer in the series of formation steps of the p-type layer and the n-type layer,
A method of manufacturing a red light emitting semiconductor element, characterized by adding Mg or Al together with Eu or Pr.

  The present inventor conducted various experiments and studies on the solution of the above problems. As a result, when an Eu-added GaN layer (active layer) is produced using a metal organic vapor phase epitaxial method (OMVPE method), when Mg or Al is added as an impurity, these elements are selectively present around Eu. It has been found that it dramatically changes the peripheral local structure of Eu ions and greatly reduces the symmetry of Eu ions.

  Usually, even if an impurity element is added to about 0.1 atomic% to Eu added to about 0.1 atomic% in GaN, it is selectively disposed around Eu as described above, This is a phenomenon that was very difficult to think because the probability that it is adjacent to the past was very low, and the present inventor discovered the above phenomenon by repeating experiments and examinations, and completed the present invention. It has come.

  Then, under a predetermined growth temperature, Eu in the active layer is arranged so as to substitute for Ga, and the substitution site of Eu ions is controlled so as to be close to the Ga site and its immediate vicinity. In the spectrum (Photoluminescence Spectrum: PL spectrum), a peak near 621 nm due to Eu ions becomes dominant, and sufficient light emission can be obtained to obtain a high light output.

  Note that “the peak near 621 nm is dominant” means that emission at a wavelength in the range of 618 to 623 nm centered at 621 nm is emission caused by Eu ions, so that the peak near 621 nm is made as large as possible. I mean.

  In the present invention, the temperature condition in the OMVPE method used for forming the active layer is important. That is, if the temperature is too low, Eu ions having different crystal fields increase and the peak at 621 nm decreases, whereas if the temperature is too high, Eu ions are desorbed from the surface, making it difficult to add Eu. A preferable temperature condition is 900 to 1100 ° C, and more preferably 950 to 1050 ° C.

  In addition, the p-type layer, the active layer, and the n-type layer are formed in a series of forming steps, that is, without being taken out from the reaction vessel in the middle, and sequentially in the reaction vessel, the p-type layer, the active layer, and the n-type layer (p-type layer, By forming the n-type layer, the interface state does not exist between the layers, and carriers can be injected efficiently. For these reasons, a low voltage operation of about several volts is possible.

  From the above viewpoint, the n-type layer and the p-type layer are also preferably formed by the OMVPE method, but other growth methods are not excluded.

  In the above description, the present invention has been described with reference to GaN as a base material and Eu as an additive element. The same effects as those described above can be obtained as a material. Further, the additive element is not limited to Eu, and the same effect as described above can be obtained even if Pr is used as the additive element.

  Note that the additive element is Eu or Pr because these elements are such that the outer electrons are shielded by the inner electrons and the emission associated with the inner shell transition has a wavelength of 590 nm or more. This is the NTSC color gamut, HDTV. This is because the light is not limited to the color gamut and can feel redness.

  According to the invention of this claim, it is possible to provide a large economic effect as described above. In other words, the realization of a red light-emitting diode using Eu-doped GaN with high light output device characteristics enables the integration of light-emitting diodes of the three primary colors of “red, green, and blue” at a practical level. Therefore, a full-color display using a small, high-definition, high-output light emitting diode can be realized.

  In addition, by adding high-intensity light emission in the red region that is not included in current white LEDs, the emission wavelength does not change depending on the ambient temperature as well as an alternative to AlGaInP-based LEDs currently used as red LEDs. High-intensity LED lighting that makes use of the characteristics of rare earth elements can be realized.

In carrying out the invention of this claim, examples of the Mg supply source include Cp ₂ Mg (bis (cyclopentadienyl) magnesium: Mg (C ₅ H ₅ ) ₂ ). May include TMA (trimethylaluminum: (CH ₃ ) ₃ Al).

The invention described in claim 2
2. The method for manufacturing a red light emitting semiconductor device according to claim 1, wherein the element added to the base material is Eu.

  Eu is more preferable as an additive element because it has a higher red light emission efficiency than Pr. Eu is also preferable as an additive element because it has a track record as a red phosphor for color televisions, and it is easier to obtain Eu compounds than Pr.

The invention according to claim 3
The method for manufacturing a red light-emitting semiconductor element according to claim 2, wherein Eu is supplied by Eu {N [Si (CH ₃ ) ₃ ] ₂ } ₃ or Eu (C ₁₁ H ₁₉ O ₂ ) _3. It is.

Examples of the Eu source include Eu [C ₅ (CH ₃ ) ₅ ] ₂ , Eu [C ₅ (CH ₃ ) ₄ H] ₂ , Eu {N [Si (CH ₃ ) ₃ ] ₂ } ₃ , Eu (C ₅ H ₇ O ₂ ) ₃ , Eu (C ₁₁ H ₁₉ O ₂ ) _3, etc., among which Eu {N [Si (CH ₃ ) ₃ ] ₂ } ₃ and Eu (C ₁₁ Since H ₁₉ O ₂ ) ₃ has a high vapor pressure in the reaction apparatus, it can be efficiently added.

The invention according to claim 4
A red light emitting semiconductor device using GaN, InN, AlN or a mixed crystal of any two or more thereof as a base material,
An active layer sandwiched between a p-type layer and an n-type layer on the substrate;
The active layer is made of GaN, InN, AlN, or a mixed crystal of any two or more thereof, E
The red light emitting semiconductor device is characterized by being an active layer formed by adding u or Pr to replace Ga, In or Al, and further adding Mg or Al together with Eu or Pr. .

  As described above, Mg and Al can further improve the light emission transition efficiency. Therefore, the red light-emitting semiconductor element to which these elements are co-doped changes the local structure around Eu ions, Since the symmetry is greatly reduced, it is possible to provide a red light emitting semiconductor element with high light emission intensity.

  The substrate on which the active layer is formed is usually sapphire, but is not limited to this. For example, Si, GaN, GaAs or the like can be used.

The invention described in claim 5
5. The red light emitting semiconductor device according to claim 4, wherein an additive amount of Mg is 1 × 10 ¹⁸ to 1 × 10 ²⁰ cm ⁻³ in the active layer.

When the amount of Mg added is too small, the symmetry of Eu ions cannot be sufficiently lowered, so that it becomes difficult to sufficiently improve the emission intensity and a high light output cannot be obtained. On the other hand, when the addition amount is too large, the crystallinity of GaN as a base material may be deteriorated. The preferable addition amount of Mg is 5 × 10 ^{18 to} 5 × 10 ¹⁹ cm ⁻³ .

The invention described in claim 6
5. The red light emitting semiconductor device according to claim 4, wherein the additive amount of Al in the active layer is more than 0 atomic% and not more than 40 atomic%.

  By adding Al, the emission intensity of the red light emitting semiconductor element is increased. However, if it exceeds 40 atomic%, the crystallinity of the matrix is lowered and the emission intensity may be lowered. A preferable addition amount of Al is 15 to 35 atomic%.

The invention described in claim 7
The red light-emitting semiconductor element according to claim 4, wherein the light output is 100 μW or more.

  In the red light emitting semiconductor element to which the impurity co-added element is added, the peripheral local structure of Eu ions changes dramatically, and the symmetry of Eu ions is greatly reduced. It is possible to provide a red light emitting semiconductor element having the above high light output.

The invention according to claim 8 provides:
A red light emitting semiconductor device using GaN, InN, AlN, or a mixed crystal of any two or more thereof,
An active layer sandwiched between a p-type layer and an n-type layer on the substrate;
The active layer is formed by adding Eu or Pr to GaN, InN, AlN, or a mixed crystal of any two or more thereof so as to replace Ga, In, or Al, and together with Eu or Pr. , Mg is an active layer to which 1 × 10 ¹⁸ to 1 × 10 ²⁰ cm ^{−3 is} added,
The red light-emitting semiconductor device is characterized in that the light output is 100 μW or more.

  Since the red light emitting semiconductor element as described above has an appropriate amount of Mg added as an impurity co-added element, as described above, the light emission intensity is greatly improved, and a red light emitting semiconductor element having a high light output of 100 μW or more is provided. can do.

The invention according to claim 9 is:
A red light emitting semiconductor device using GaN, InN, AlN, or a mixed crystal of any two or more thereof,
An active layer sandwiched between a p-type layer and an n-type layer on the substrate;
The active layer is formed by adding Eu or Pr to GaN, InN, AlN, or a mixed crystal of any two or more thereof so as to replace Ga, In, or Al, and together with Eu or Pr. , An active layer to which Al is added in an amount exceeding 0 atomic% and not exceeding 40 atomic%,
The red light-emitting semiconductor device is characterized in that the light output is 100 μW or more.

  In the red light emitting semiconductor device as described above, Al is added in an appropriate amount as an impurity co-added element as in the case of Mg co-addition, so that the emission intensity is greatly improved as described above, and high light of 100 μW or more. An output red light emitting semiconductor device can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the light emission transition efficiency of Eu ion and Pr ion can be increased, and the red light emitting semiconductor element of the outstanding light emission intensity, and its manufacturing method can be provided.

It is a figure which shows the basic structure of the red light emitting semiconductor element of embodiment of this invention. It is a figure which shows the photoluminescence spectrum of the red light emitting semiconductor element of Experimental example 1. FIG. It is a figure which shows the photoluminescence spectrum of the red light emitting semiconductor element of Experimental example 2.

  Hereinafter, the present invention will be described based on embodiments. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

(Structure of red light emitting semiconductor element)
FIG. 1 shows a basic structure of a red light emitting semiconductor element in the present embodiment. In FIG. 1, 10 is Eu in which Eu and an impurity co-added element are added to a GaN base material, impurity co-doped GaN layer, 20 is an undoped GaN layer, 30 is a GaN buffer layer, and 40 is a sapphire substrate.

(Experimental example 1)
In this experimental example, a red light-emitting semiconductor device in which Eu co-doped with Mg as an impurity co-added element and an Mg co-doped GaN layer was formed as an active layer was fabricated, and the light emission intensity was measured.

1. Production of Red Light-Emitting Semiconductor Element First, a GaN buffer layer (thickness 30 nm) 30 was grown on the sapphire substrate 40 by using an organic metal gas layer growth method (OMVPE method).

  Next, an undoped GaN layer (thickness: 3.4 μm) 20 was grown on the GaN buffer layer 30 in the same manner using the OMVPE method.

  Next, an Eu and Mg co-doped GaN layer (thickness 300 nm) 10 serving as an active layer was laminated on the undoped GaN layer 20.

Trimethylgallium and ammonia were used as the Ga raw material and N raw material, respectively, and Eu (DPM) ₃ , that is, Eu (C ₁₁ H ₁₉ O ₂ ) ₃ was used as the Eu organic raw material. Further, Cp ₂ Mg was used as the Mg organic raw material.

  The formation of the Eu and Mg co-doped GaN layer 10 was controlled such that the carrier gas flow rate was 40 SLM and the growth rate was 0.8 μm / h under growth conditions of a temperature of 1030 ° C. and a pressure of 100 kPa. Hydrogen was used as the carrier gas.

  In addition, by changing the piping valve etc. of the OMVPE device from the normal specification (heat resistant temperature 80-100 ° C) to the high temperature special specification, it is possible to keep the cylinder temperature at 135 ° C, a sufficient amount Of Eu can be supplied to the reaction tube.

  The formation of each layer was performed in a series of steps so as not to interrupt the growth without taking out the sample from the reaction tube on the way.

The Eu concentration and Mg concentration in the produced active layer were measured by secondary ion mass spectrometry (SIMS). The Eu concentration was 3 × 10 ¹⁹ cm ⁻³ and the Mg concentration was 5 × 10 ¹⁹ cm ⁻³ . there were.

2. Preparation of Comparative Specimen Separately, for comparison, a red light emitting semiconductor element having an Eu-added GaN layer to which only Eu was added as an active layer was manufactured under the same conditions as described above.

3. Next, for each of the obtained red light emitting semiconductor elements, a photoluminescence spectrum (PL spectrum) from each active layer was measured using a helium / cadmium laser (room temperature).

  The results are shown in FIG. In FIG. 2, the vertical axis represents the PL intensity (arbitrary unit, au), and the horizontal axis represents the wavelength (nm). A solid line is a PL spectrum from the active layer to which Mg is added, and a broken line is a PL spectrum from the active layer to which only Eu is added.

  As shown in FIG. 2, it can be seen that a new emission peak is generated around 619 nm by co-adding Mg as an impurity element to Eu. This is not a shift of the peak of the conventional Eu-added GaN layer to which only Eu is added, but is a peak newly generated by a composite of Eu and Mg. The emission intensity is 5 times stronger than the conventional peak at room temperature, and it is shown that the emission intensity increases by co-adding Mg to reduce the symmetry of the local structure of Eu ions.

(Experimental example 2)
In this experimental example, a red light-emitting semiconductor element in which Eu co-doped with Al as an impurity co-doped element and an Al co-doped GaN layer was formed as an active layer was fabricated, and the light emission intensity was measured.

1. Production of Red Light-Emitting Semiconductor Element In the same manner as in Experimental Example 1, a GaN buffer layer (thickness 30 nm) 30 and an undoped GaN layer (thickness 3.4 μm) 20 were grown on the sapphire substrate 40.

Next, an Eu and Al co-doped GaN layer (thickness 300 nm) 10 serving as an active layer was laminated on the undoped GaN layer 20. At this time, the Al concentration is controlled to be 8 atomic%, 16 atomic%, 24 atomic%, 35 atomic%, and 40 atomic%, that is, the active layers to be formed are each Al _0.08 Ga _{0. .92} N, Al _0.16 Ga _0.84 N, Al _0.24 Ga _0.76 N, Al _0.35 Ga _0.65 N, Al _0.40 Ga _0.60 N Five types of red light emitting semiconductor elements were produced.

Trimethylgallium and ammonia were used as the Ga raw material and N raw material, respectively, and Eu (DPM) ₃ was used as the Eu organic raw material. Trimethylaluminum was used as the Al organic material.

  The growth temperature was 1030 ° C. In addition, when the growth pressure is set to 100 kPa as in the case of Experimental Example 1, a gas phase reaction occurs between the Eu organic material and the Al organic material, and Eu is not taken into the AlGaN phase. 20 kPa.

  The carrier gas flow rate was controlled to be 40 SLM and the growth rate was 0.8 μm / h. Hydrogen was used as the carrier gas.

  In addition, by changing the piping valve etc. of the OMVPE device from the normal specification (heat resistant temperature 80-100 ° C) to the high temperature special specification, it is possible to keep the cylinder temperature at 135 ° C, a sufficient amount Of Eu can be supplied to the reaction tube.

  The formation of each layer was performed in a series of steps so as not to interrupt the growth without taking out the sample from the reaction tube on the way.

When the Eu concentration in the produced active layer was measured by secondary ion mass spectrometry (SIMS), all the specimens were 3 × 10 ¹⁹ cm ⁻³ .

2. Preparation of Comparative Specimen Separately, for comparison, a red light emitting semiconductor device having an Eu-doped GaN layer to which only Eu was added as an active layer was produced under the same conditions as described above except that the growth pressure was set to 100 kPa.

3. Next, the PL spectrum was measured for each of the obtained red light emitting semiconductor elements in the same manner as in Experimental Example 1 (room temperature).

  The results are shown in FIG. In FIG. 3, the vertical axis represents the PL intensity (arbitrary unit, au), and the horizontal axis represents the wavelength (nm). Note that the descriptions such as “× 2” and “× 3” in FIG. 3 indicate that the respective PL intensities are expanded to “2 times” and “3 times” in the vertical axis direction.

  As can be seen from FIG. 3, the PL intensity increases as the Al composition (concentration) increases, and after reaching the maximum at the Al composition of 24%, the PL intensity decreases as the Al composition increases. . This is related to the fact that the higher the Al composition, the lower the crystallinity of the matrix. Further, as the Al composition increases, the emission peak broadens and the wavelength increases, indicating that Al is involved in Eu emission. From the above, it has been found that the emission intensity is increased by co-adding Al during the formation of Eu-added GaN (film formation).

  As described above, in the present invention, it is possible to manufacture and provide a red light emitting semiconductor element having excellent light output by co-adding an appropriate impurity element.

  As a result, it is possible to realize a full-color display using a small, high-definition, high-output light emitting diode as described above and high-luminance LED illumination.

10 Eu-doped GaN layer 20 Undoped GaN layer 30 GaN buffer layer 40 Sapphire substrate

Claims (9)

A method of manufacturing a red light emitting semiconductor device using GaN, InN, AlN or a mixed crystal of any two or more thereof,
Using GaN, InN, AlN, or a mixed crystal of any two or more thereof as a base material, Eu or Pr is changed to Ga, In under a temperature condition of 900 to 1100 ° C. using a metal organic vapor phase epitaxial method. Alternatively, when the active layer added so as to replace Al is formed between the p-type layer and the n-type layer in the series of formation steps of the p-type layer and the n-type layer,
A method for producing a red light emitting semiconductor element, comprising adding Mg or Al together with Eu or Pr.   2. The method for manufacturing a red light emitting semiconductor element according to claim 1, wherein the element added to the base material is Eu. The method for manufacturing a red light-emitting semiconductor element according to claim 2, wherein Eu is supplied by Eu {N [Si (CH ₃ ) ₃ ] ₂ } ₃ or Eu (C ₁₁ H ₁₉ O ₂ ) _3. . A red light emitting semiconductor device using GaN, InN, AlN or a mixed crystal of any two or more thereof as a base material,
An active layer sandwiched between a p-type layer and an n-type layer on the substrate;
The active layer is made of GaN, InN, AlN, or a mixed crystal of any two or more thereof, E
A red light emitting semiconductor device, wherein an active layer is formed by adding u or Pr to replace Ga, In or Al, and further adding Mg or Al together with Eu or Pr. 5. The red light emitting semiconductor device according to claim 4, wherein an additive amount of Mg in the active layer is 1 × 10 ¹⁸ to 1 × 10 ²⁰ cm ⁻³ .   5. The red light emitting semiconductor device according to claim 4, wherein, in the active layer, an additive amount of Al exceeds 0 atomic% and does not exceed 40 atomic%.   The red light-emitting semiconductor element according to claim 4, wherein the light output is 100 μW or more. A red light emitting semiconductor device using GaN, InN, AlN, or a mixed crystal of any two or more thereof,
An active layer sandwiched between a p-type layer and an n-type layer on the substrate;
The active layer is formed by adding Eu or Pr to GaN, InN, AlN, or a mixed crystal of any two or more thereof so as to replace Ga, In, or Al, and together with Eu or Pr. , Mg is an active layer to which 1 × 10 ¹⁸ to 1 × 10 ²⁰ cm ^{−3 is} added,
A red light-emitting semiconductor element characterized by having an optical output of 100 μW or more. A red light emitting semiconductor device using GaN, InN, AlN, or a mixed crystal of any two or more thereof,
An active layer sandwiched between a p-type layer and an n-type layer on the substrate;
The active layer is formed by adding Eu or Pr to GaN, InN, AlN, or a mixed crystal of any two or more thereof so as to replace Ga, In, or Al, and together with Eu or Pr. , An active layer to which Al is added in an amount exceeding 0 atomic% and not exceeding 40 atomic%,
A red light-emitting semiconductor element characterized by having an optical output of 100 μW or more.

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