JP4848530B2 - Light emitting diode and manufacturing method thereof - Google Patents

Description

  The present invention relates to a light emitting diode used for various optical sensors, various optical information processing apparatuses, various optical pointers, and the like, and a method for manufacturing the same.

In a light emitting diode (LED), a current blocking type light emitting diode that concentrates current in a specific light emitting region to obtain a point light source or enhances light emission efficiency, and a point light source array in which these are arranged side by side A type of light emitting diode is known (see, for example, Patent Document 1, Non-Patent Documents 1 and 2). Since the current blocking type light emitting diode has a high current density applied to the light emitting region, for example, when it is energized for about 1000 hours, the element deteriorates and the light output intensity decreases. That is, there is a problem that reliability is poor.
In addition, as an element structure, for example, in the case of AlGaAs, a first cladding layer composed of a p-type Al _x Ga _1-x As layer (where 0 ≦ x ≦ 1), and p-type Al _y Ga. _An active layer composed of a _1-y As layer (where 0 ≦ y ≦ 1) and an n-type Al _z Ga _1-z As layer (where 0 ≦ z ≦ 1) are formed. A double heterostructure composed of at least three layers of two cladding layers is common.
In addition, by using germanium (Ge) instead of zinc (Zn) as the dopant added to the p-type active layer, the relative output with respect to the initial output after 1000 hours can be maintained at 80% or more, and reliability It is known that can improve (for example, refer patent document 2).

JP-A-6-69540 (paragraph [0044], FIG. 6 and FIG. 8) Japanese Patent No. 3187279 (paragraphs [0013] and [0022]) Hirofumi Imamoto, Masashi Yanagase, Motoaki Takaoka, “Reliability evaluation of AlGaInP point light source LED”, IEICE Technical Report, R96-21 (1996-11) p. 11-16 Toshihiro Kato, Takashi Saka, Masumi Sugaya, Takenori Sone, “Development of Infrared Point Light Source LED Using Black Reflector”, Daido Institute of Technology Bulletin 34 (1998) p. 109-111

However, in the current blocking type light emitting diode, when a group 4 element such as Ge is used as the dopant of the p-type active layer, there is a problem that the light output intensity and the reverse voltage characteristic are insufficient. In response to this problem, the light output intensity can be increased by controlling the amount of a group 4 element such as Ge added to the p-type active layer, but the light output is greatly reduced due to deterioration of the element during energization. That is, reliability is lowered. In addition, the reverse voltage characteristics are insufficient to adjust to any of them.
On the other hand, when a 2A group element such as magnesium (Mg) or a 2B group element such as Zn is used as a dopant of the p-type active layer, there is a problem that the light output during energization is greatly reduced, that is, the reliability is poor. In order to solve this problem, the reliability can be improved to some extent by controlling the amount of 2A group elements such as Mg and 2B group elements such as Zn added to the p-type active layer, but the light output intensity decreases. .

  Therefore, in view of the above points, the present invention controls the dopant material of the p-type active layer and the amount thereof, so that the fluctuation of the light output intensity during energization is small, and the light output intensity and the reverse voltage characteristic are excellent. Another object of the present invention is to provide a light emitting diode and a method for manufacturing the same.

In order to achieve the above object, a light-emitting diode according to the present invention includes a first cladding layer composed of an Al _x Ga _1-x As layer (0 ≦ x ≦ 1), an Al _y Ga _1-y As layer (0 ≦ In a light emitting diode in which a p-type active layer composed of y ≦ 1, y <x) and a second cladding layer composed of an Al _z Ga _1-z As layer (0 ≦ z ≦ 1, y <z) are joined When the element of Ge is added alone, in such an amount that the effective acceptor density becomes 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ when Zn is added alone as a dopant to the p-type active layer. An amount of effective acceptor density of 2 × 10 ¹⁸ cm ⁻³ is added, and both Zn and Ge are added.
The light emitting diode preferably includes a current blocking layer having a function of blocking current, which is of a conductive type and a reverse conductive type.
A plurality of light emitting diode elements having any of the above structures may be provided on one chip.
The x, y, and z are 0.3, 0.03, and 0.3, respectively .
The reverse voltage when electrified 5.66 × 10 ⁻² A / cm ^{2 in the} reverse direction is 8 V or more.

On the other hand, a method of fabricating a light emitting diode according to the present invention is the manufacturing method of the first cladding layer and the p-type active layer and the light emitting diode bonded to the second cladding layer, Al _x Ga as the first cladding layer After the growth of the _1-x As layer (0 ≦ x ≦ 1), an amount is added such that the effective acceptor density is 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ when the Zn element is added alone. In addition, an Ge _{y element} is added in an amount such that the effective acceptor density when it is added alone is 2 × 10 ¹⁸ cm ^−3, and an Al _y Ga _1-y As layer (0 ≦ y) as the p-type active layer. ≦ 1, y <x), and an Al _z Ga _1-z As layer (0 ≦ z ≦ 1, y <z) is grown as the second cladding layer on the active layer. .
Preferably, before the first cladding layer is grown, a current blocking layer is grown on the substrate to remove the current blocking layer at a predetermined location. The current blocking layer is grown by the MOCVD method, and the first cladding layer, the p-type active layer, and the second cladding layer are grown by the LPE method.

  According to the present invention, a group 4 element and a group 2A or group 2B element are added in predetermined amounts as dopants for the p-type active layer, the fluctuation of the light output intensity during energization is suppressed, and the reverse voltage characteristics In addition, a light emitting diode having high light output intensity and exhibiting preferable characteristics as LED characteristics can be provided. The reason why the characteristics are improved is that the effects of both elements, that is, the effect of suppressing the fluctuation of the light output intensity during energization by the dopant of the group 4 element, the light output intensity by the dopant of the group 2A or 2B element and the reverse It is presumed that the effect of improving the voltage characteristics complements each other. In addition, when both are added alone, there is less fluctuation in the light output intensity during energization, that is, reliability is improved, so there is some synergistic effect on reliability. Inferred. Furthermore, a point light source can be obtained by providing the LED structure on the current blocking layer to obtain a current blocking LED.

  In the method of manufacturing a light emitting diode according to the present invention, when a p-type active layer is grown, a predetermined amount of each of a group 4 element and a group 2A or 2B element is added as a dopant. Thereby, the light emitting diode which has a synergistic effect by each dopant can be manufactured. In addition, before sequentially growing the first cladding layer, the active layer, and the second cladding layer, a current blocking layer is grown on the substrate by MOCVD or the like, and after removing the current blocking layer at a predetermined location, Therefore, the manufactured light emitting diode can be used as a point light source.

Now, embodiments of the present invention will be described in detail.
Hereinafter, a current blocking type point light source array type light emitting diode will be described as an example of the light emitting diode according to the present invention.
FIG. 1A is a diagram showing a cross-sectional structure of the point light source array type light emitting diode, and FIG. 1B is a plan view thereof. That is, FIG. 1A is a cross-sectional view taken along line XX in FIG. As shown in FIG. 1, each element 20a, 20b, 20c of the point light source array type light-emitting diode 20 blocks a substrate 1 having a recess 4 serving as a current path and a conduction type opposite to the conduction type of the substrate 1 to block current. And a double heterojunction LED structure comprising a clad layer 5 having the same conductivity type as that of the substrate 1, an active layer 6, and a clad layer 7 having a reverse conductivity type of the substrate 1. In each of the elements 20a, 20b, and 20c, light emitted from a predetermined LED structure region without the current blocking layer 2 on the substrate 1 is emitted to the outside from the light emitting unit 17 having a predetermined size (L) (FIG. 1). See the up arrow ↑).

  Here, each element 20a, 20b, 20c of the point light source array type light emitting diode 20 is separated by the separation groove 8 to a depth reaching the substrate 1, and a structure for reducing the leakage current of each element 20a, 20b, 20c and It has become. The separation groove 8 also serves as a separation between the electrodes 15 and 16, whereby both the N electrode 15 and the P electrode 16 can be formed in the same plane, so that the point light source array type light emitting diode 20 is formed. It becomes possible to perform flip chip mounting on a circuit board. Reference numeral 9 denotes an oxide film layer, and reference numeral 11 denotes a P contact portion of a diffusion region penetrating to the substrate 1, which has a function of passing a current from the P electrode 16 to the substrate 1.

For example, when a p-type GaAs substrate of the Group 3-5 substrate is used as the substrate 1, the current of the n-type Al _a Ga _1-a As layer (0 ≦ a ≦ 1) is formed on the upper surface of the substrate 1. The current blocking layer 2 has a role of blocking the current. Then, the current blocking layer 2 is etched until it reaches the substrate 1, and the cladding layer 5 of the p _- type Al _x Ga _1-x As layer (0 ≦ x ≦ 1) is formed in the concave portion 4 formed in a partially cylindrical shape. The double heterojunction LED structure of the active layer 6 of the n _- type Al _y Ga _1-y As layer (0 ≦ y ≦ 1) and the clad layer 7 of the n-type Al _z Ga _1-z As layer (0 ≦ z ≦ 1) Crystals are grown to form an N electrode 15 to form a light emitting portion 17. An array type light emitting diode is one in which such elements are arranged one-dimensionally or two-dimensionally.

In the present invention, the active layer 6 of the p-type Al _y Ga _1-y As layer (0 ≦ y ≦ 1) has both a group 2A or group 2B element and a group 4 element as dopants, that is, 2A. Both Group element and Group 4 element, or both Group 2B element and Group 4 element are added. Here, examples of the group 2A element include magnesium (Mg) and beryllium (Be), and examples of the group 2B element include zinc (Zn) and cadmium (Cd). Examples of the group 4 element include germanium (Ge), silicon (Si), tin (Sn), and the like. Further, each element can be added to the active layer 6 by adding each element to the gallium (Ga) melt when the active layer 6 is grown by, for example, an LPE (Liquid Phase Epitaxy) method. It is.
The amount added to the active layer 6 is a predetermined amount determined for each element. For example, when the LPE method is used, since the proportion taken into the active layer 6 from the solution varies depending on the growth temperature, the composition of the growth layer, etc., the predetermined amount is p-type when each is added as a single dopant. The effective acceptor density in the active layer is as follows.
In the case of a Group 4 element, the effective acceptor density of the p-type active layer 6 is set to 1 × 10 ¹⁸ to 2 × 10 ¹⁹ cm ⁻³ when the Group 4 element is added alone. A preferable value of the effective acceptor density is 2 × 10 ¹⁸ to 8 × 10 ¹⁸ cm ⁻³ , and an optimal value is 2 × 10 ¹⁸ cm ⁻³ .
In the case of an element of group 2A or 2B, the effective acceptor density of the p-type active layer 6 is set to 1 × 10 ¹⁷ to 2 × 10 ¹⁸ cm ⁻³ when the element alone is added. The optimum value of the effective acceptor density is 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ .
In this range, it is possible to obtain a light-emitting diode with little light output intensity fluctuation during energization, good reverse voltage characteristics, and high light output intensity.

  Next, a method of manufacturing the light emitting diode of the present invention will be described with reference to FIGS. 2 to 6 showing steps of manufacturing the current blocking type point light source array type light emitting diode 20 of FIG. 1 as an example. 5 (A) to 5 (C), 6 (A), and 6 (B) are respectively planes of FIGS. 2 (B), (D), 3 (B), (C), and 4 (C). FIG. For example, FIG. 2B is a cross-sectional view taken along line Y1-Y1 in FIG. In the following description, a manufacturing method using a P-type substrate will be described as an example.

As a first step, as shown in FIG. 2A, an n-type Al _a Ga _1-a As layer (here, 0 ≦ 0) is formed on a p-type GaAs substrate 1 by, eg, MOCVD (Metal Organic Chemical Vapor Deposition). A current blocking layer 2 made of a ≦ 1) is grown to a thickness of about several μm (for example, 1 to 5 μm).

  As a second step, as shown in FIG. 2B and FIG. 5A, the pattern of the concave portion 4 serving as the light emitting portion and the portion 4 ′ serving as the P contact portion is formed on the epitaxial growth surface by photolithography. Form. That is, after the resist 3 is formed on the current blocking layer 2 by the photolithography method, a portion where the resist 3 is not present is etched on the surface, and the concave portion 4 which is a light emitting portion and the portion 4 ′ which is a P contact portion Form. As a result, a portion without the current blocking layer 2, that is, a region exists. Here, the concave portion 4 serving as a light emitting portion can be formed in a circular shape having a diameter L1, and the portion 4 'serving as a P contact portion can be formed in a stripe shape having a width L2. The resist 3 is removed later.

As a third step, as shown in FIG. 2C, an LED structure, for example, a p-clad layer 5 (p-type Al _x Ga _1-x As layer) and an active layer 6 are formed on the epitaxial growth surface on which this pattern is formed. Sandwich structures of (p-type Al _y Ga _1-y As layer) and n-clad layer 7 (n-type Al _z Ga _1-z As layer) are grown by, for example, the LPE method. However, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, y <x, z. When each layer of the LED structure is grown by, for example, the LPE method, a composition and a dopant necessary for epitaxial growth are placed in each growth solution reservoir, and these solutions are brought into contact with the substrate, and epitaxial growth is performed on the substrate by a temperature drop. This operation is sequentially repeated for each layer.

As a fourth step, as shown in FIGS. 2D and 5B, an electrode having a depth reaching the substrate 1 and an etching groove 8 for element isolation are formed in the epitaxial layer.
As a fifth step, an oxide film (SiO ₂ ) layer 9 is formed on the epitaxial layer by sputtering or CVD, and then oxidation of the portion 10 that becomes the P contact portion is performed as shown in FIG. The layer of the film (SiO ₂ ) is removed by etching.
Then, as a sixth step, the substrate 1 that has undergone the fifth step is heat-treated in a zinc (Zn) atmosphere, and is removed by etching in the fifth step, as shown in FIGS. 3B and 5C. By diffusing Zn from the portion 10 thus formed, a P-type diffusion region is formed, and the P contact portion 11 is formed. In this case, the oxide film (SiO ₂ ) layer 9 serves as a mask for limiting the Zn diffusion region.
As a seventh step, as shown in FIGS. 3C and 6A, a portion 12 to be an N contact portion is formed by etching.
As an eighth step, a pattern of a resist 13 as shown in FIG. 4A is formed by photolithography and an electrode material 14 is deposited (FIG. 4B). Then, the resist is peeled off by lift-off, and FIG. ), An electrode pattern as shown in FIG. 6B is formed, which is referred to as an N electrode 15 and a P electrode 16, respectively.
Finally, as a ninth step, for example, wiring 18 as shown in FIG. 4D is formed of, for example, aluminum (Al) or the like to manufacture an array type LED chip 21 of a flip chip type one-dimensional point light source. FIG. 4D shows a one-dimensional point light source array type LED chip 21 having three light emitting portions 17. Here, in the present invention, the chip is a chip in which a plurality of elements are arranged one-dimensionally or two-dimensionally.

(Example)
Examples will be described below.
FIG. 7 is a table showing each composition of the point light source array type light emitting diode and the kind of dopant in this example.
As a first manufacturing step, a current blocking layer 2 made of an n-type GaAs layer was grown on a p-type GaAs substrate 1 having a carrier density of 2 × 10 ¹⁹ cm ⁻³ by MOCVD. Hydrogen was used as the carrier gas for the MOCVD method. At this time, the growth temperature was 700 ° C., and the growth pressure was 75 Torr (about 1 × 10 ⁴ Pa). Trimethylgallium (TMG) and arsine (AsH ₃ ) were used as GaAs raw materials, and the respective flow rates were set to 0.13 mmol (mmol) / min and 1.3 mmol / min. Sulfur (S) was used as the n-type dopant, and its supply source was hydrogen sulfide (H ₂ S), and this H ₂ S gas was flowed at a concentration of 10,000 ppm during growth. In this way, a current blocking layer 2 made of an n-type GaAs layer having a carrier density of 1 × 10 ¹⁹ cm ⁻³ and a thickness of 2 μm was grown (see FIG. 2A). In addition, selenium is used for the n-type dopant, hydrogen selenide (H ₂ Se) is used as the supply source, or tellurium (Te) is used as the n-type dopant, and diethyl tellurium (DETe) is used as the supply source. , Silicon (Si) is used as the n-type dopant, silane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used as the supply source, and tin (Sn) is used as the n-type dopant. It is also possible to use triethyltin (TESn) or trimethyltin (TMSn) as the supply source.

As a second step of manufacturing, a circular pattern having a diameter L1 = 15 μm and a stripe pattern having a width L2 = 100 μm are formed on the current blocking layer 2 obtained in the first step by a photolithography method. By etching, a hole is formed in a part of the current blocking layer 2 to form a recess, and a portion serving as a current path when the LED structure is grown in the third step of the subsequent manufacturing is provided (FIG. 2 ( B), FIG. 5 (A)). Here, etching was performed using phosphoric acid (H ₃ PO ₄ ) —H ₂ O ₂ —H ₂ O-based etching solution.
As a third step of manufacturing, a p-type Al _0.3 Ga _0.7 As layer 802 as a p-clad layer 5 is sequentially formed on the substrate 1 with the current blocking layer 2 obtained in the second step by a slow cooling method of the LPE method. The p-type Al _0.03 Ga _0.97 As layer as the active layer 6 is grown at about 1 μm at 800 ° C., and the n-type Al _0.3 Ga _0.7 As layer as the n-clad layer 7 is grown at 800-800 ° C. A double hetero type LED structure was formed by growing it at about 7 μm at 795 ° C. (see FIG. 2C). Doping in the LED structure was performed by adding an element serving as a dopant to the Ga melt. Magnesium (Mg) or zinc (Zn) was used as a dopant for the p-clad layer 5, and tellurium (Te) was used as a dopant for the n-clad layer 7. In this embodiment, both germanium (Ge) and zinc (Zn) are used as dopants for the active layer 6 and are taken into the active layer 6 by a predetermined amount in consideration of growth temperature, layer composition, and the like. It was made to be. That is, when Ge is added alone, Zn is added alone in such an amount that the effective acceptor density becomes 2.0 × 10 ¹⁸ , 8.0 × 10 ¹⁸ , or 1.5 × 10 ¹⁹ cm ⁻³ . Occasionally an effective acceptor density of 1.0 × 10 ¹⁷ , 2.5 × 10 ¹⁷ , 5.0 × 10 ¹⁷ , 1.0 × 10 ¹⁸ , 2.0 × 10 ¹⁸ cm ⁻³ is added Then, the active layer 6 was grown.

As the fourth manufacturing step, an etching groove 8 for separating electrodes and elements was formed in a width of 50 μm in the epitaxial layer grown in the third manufacturing step (see FIGS. 2D and 5B). As a fifth step of manufacturing, RF plasma CVD is used, and silane (SiH ₄ ) gas and dinitrogen monoxide (N ₂ O) gas are flowed as source gases, the substrate temperature is 350 ° C., the pressure is 0.5 Torr (about An oxide film (SiO ₂ ) having a thickness of 0.3 μm was deposited on the epitaxial layer at a high frequency power of 500 W at 6.7 × 10 Pa). Thereafter, the oxide film (SiO ₂ ) layer of the portion 10 which becomes the P contact portion was removed by etching with a fluorine-based etchant (see FIG. 3A).
As a sixth step of manufacturing, a wafer and ZnAs ₂ (zinc diarsenide) are set in a quartz container, heat-treated in a hydrogen atmosphere at a temperature of 600 ° C. for 2 hours, and removed by etching in the fifth step of manufacturing. Zinc (Zn) was diffused from 10 to form a P-type region as the P contact portion 11 (see FIGS. 3B and 5C).
As a seventh manufacturing step, a portion 12 to be an N contact portion was formed by etching (see FIGS. 3C and 6A).
As an eighth step of manufacturing, a resist 13 pattern is formed by a photolithography method (see FIG. 4A), the electrode material 14 is deposited (see FIG. 4B), and then boiled in acetone. The N electrode 15 and the P electrode 16 were formed by a so-called lift-off method (see FIGS. 4C and 6B).
As a ninth manufacturing process, a flip chip type one-dimensional array type LED chip was manufactured by forming wiring 18 with Al (see FIG. 4D).

FIG. 8 is a table showing the characteristic results of the light-emitting diode at each doping amount of Ge and Zn into the p-type active layer 6, where (a) is reliability, (b) is reverse voltage characteristics, and (c) is light. It is the table | surface which showed each average value of output intensity. Here, the reliability is a relative value of the output with respect to the initial output when 1000 hours have elapsed with 283 A / cm ² energization at 25 ° C. The reverse voltage is an applied voltage when 5.66 × 10 ⁻² A / cm ² is applied in the reverse direction of the pn junction at 25 ° C. The light output intensity is the light output intensity when energized at 90.6 A / cm ² at 25 ° C., and is expressed as a relative value with respect to the reference intensity. The higher the value, the better the characteristics as a light emitting diode. FIG. 8 also shows the result of a comparative example to be described later, that is, the result when only Ge is doped and when only Zn is doped.

When both Ge and Zn are used as dopants, as is apparent from FIG. 8 (a), the reliability is an average of about 95.5% under all of the doping conditions performed as examples, and at least about A sufficiently high value of 90% was obtained. This value can be said to be higher than that in Comparative Example 2 described later, that is, when only Zn is used as the dopant added to the active layer 6.
Further, as is clear from FIG. 8B, the reverse voltage is an effective acceptor density when the effective acceptor density when adding Ge alone is 2.0 × 10 ¹⁸ cm ⁻³ and Zn is added alone. When the density is 1.0 × 10 ^{17 to} 1.0 × 10 ¹⁸ cm ⁻³ , it is about 9 to 10 V, which is sufficient as LED characteristics. If the dopant added to the active layer 6 is both Ge and Zn, and the effective acceptor density when these are added alone is within such a range, the dopant of the active layer 6 compared to Comparative Example 1 described later. Thus, it is possible to obtain reverse voltage characteristics that could not be obtained when only Ge was used.
Further, as is apparent from FIG. 8C, the light output intensity is effective when the effective acceptor density when adding Ge alone is 2.0 × 10 ¹⁸ cm ⁻³ and when Zn is added alone. When the acceptor density is 1.0 × 10 ^{17 to} 1.0 × 10 ¹⁸ cm ⁻³ , it is about 0.5, which is sufficient as LED characteristics. When the dopant added to the active layer 6 is Ge and Zn, and the effective acceptor density when these are added alone is within such a range, the dopant of the active layer 6 is Ge as compared with Comparative Example 1 described later. It is possible to obtain a light output intensity that cannot be obtained when only the light source is used.
Considering each of the above characteristics comprehensively, sufficient reliability, reverse voltage characteristics, and light output intensity can be obtained by adjusting each addition amount using both Ge and Zn as dopants to the active layer 6. Can do. That is, the effective acceptor density when Ge is added alone is about 2 × 10 ¹⁸ to 8 × 10 ¹⁸ cm ⁻³ , and the effective acceptor density when Zn is added alone is 1 × 10 ¹⁷ to 2 × 10 ^18. By setting it to around cm ⁻³ , good values were obtained for each characteristic of reliability, reverse voltage characteristics, and light output intensity. In particular, the effective acceptor density when adding Ge alone is about 2.0 × 10 ¹⁸ cm ⁻³ , and the effective acceptor density when adding Zn alone is 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ . In the range, reliability is 90% or more, reverse voltage is 8V or more, and light output intensity is all 0.45 or more.

(Comparative Example 1)
In Comparative Example 1, only Ge was used as a dopant to the p-type active layer 6 in the third step of manufacturing. Other processes and characteristic evaluation are the same as in the example.
As is clear from FIG. 8A, the reliability is 96.8% and 95.5% when the effective acceptor density is about 8 × 10 ¹⁸ cm ⁻³ or more. However, when the effective acceptor density is 2.0 × 10 ¹⁸ cm ⁻³ , it is about 75%, which is insufficient as LED characteristics. Further, as is clear from FIG. 8B, the reverse voltage is as low as about 6 to 8 V regardless of the amount of effective acceptor density, and is insufficient as LED characteristics.
Further, as is clear from FIG. 8C, the light output intensity is 0.49 when the effective acceptor density is 2.0 × 10 ¹⁸ cm ⁻³ , but greatly increases to 0.31 when the effective acceptor density is increased. To decrease.
As described above, when each characteristic is comprehensively determined, when the amount of Ge added is increased and the effective acceptor density of the p-type active layer 6 is 8.0 × 10 ¹⁸ cm ⁻³ , the reliability is improved to 96.8%. Although the value is satisfactory as a characteristic, on the other hand, the light output intensity decreases from 0.49 to 0.39. Further, even if the amount of Ge added is increased, the reliability is 95.5%, which is substantially the same, but the light output intensity is further reduced. That is, when only Ge is used as the dopant for the p-type active layer 6, a light-emitting diode with sufficient reliability that the light output intensity does not decrease during energization can be obtained by appropriately selecting the addition amount. The reverse voltage characteristics and the light output intensity are not sufficient.

(Comparative Example 2)
In Comparative Example 2, only Zn was used as a dopant for the p-type active layer 6 in the third step of production. Other processes and characteristic evaluation are the same as in the example.
As is clear from FIG. 8A, the reliability is 92.9% when the effective acceptor density is about 2 × 10 ¹⁸ cm ⁻³ , which is the lowest value in this embodiment. If it is 1.0 × 10 ¹⁸ cm ⁻³ or less, they are 81.6% and 42.4%, which are insufficient as LED characteristics.
Further, as is clear from FIG. 8B, the reverse voltage is about 9 to 11 V regardless of the amount of effective acceptor density, and the LED characteristics are sufficient.
Further, as is clear from FIG. 8C, the light output intensity is 0.56 which is sufficient when the effective acceptor density is 5.0 × 10 ¹⁷ cm ⁻³ , but is 0 when the effective acceptor density is increased. To 42.
As described above, when comprehensively judging each characteristic, when the effective acceptor density in the p-type active layer 6 is 5.0 × 10 ¹⁷ cm ⁻³ , the reverse voltage is 10.5 V and the light output intensity is 0.56. Both values are higher than when only Ge is used (Comparative Example 1), but the reliability is about 40%, which is very low.
Further, when the added amount of Zn is increased and the effective acceptor density in the p-type active layer 6 is 1.0 × 10 ¹⁸ cm ⁻³ , the reliability is improved to 81.6%, while the light output intensity is increased. Will decrease by about 10%. Furthermore, when the addition amount of Zn is increased, the reliability is further improved to 92.9%, but the light output intensity is further reduced.
That is, when only Zn is used as the dopant for the p-type active layer 6, the reverse voltage characteristic is generally good, but the light output intensity and the reliability cannot be improved at the same time.

Here, comparing the example with Comparative Examples 1 and 2, when either Zn or Ge is used as the dopant of the p-type active layer 6, all of reliability, reverse voltage characteristics, and light output intensity are obtained. Although satisfactory LED characteristics cannot be obtained, when both Zn and Ge are used, LED characteristics satisfying all of reliability, reverse voltage characteristics, and light output intensity can be obtained.
As for reliability, it is possible to suppress fluctuations in the light output intensity during energization by adding both of them in comparison with the case where Ge and Zn are added alone.

As described above, according to the present invention, both the elements of Group 2A or Group 2B and the element of Group 4 are added to the p-type active layer. A good light emitting diode can be obtained with respect to all the characteristics of the light output intensity.
In addition, according to the present invention, the p-type active layer is grown by adding both elements of Group 2A or Group 2B and Group 4 element, thereby improving reliability, reverse voltage, and light output intensity. Good light-emitting diodes can be manufactured for all of these characteristics.
Further, the present invention is not limited to the one-dimensional point light source array type LED chip in FIG. 1, but is not limited to the two-dimensional point light source array type LED chip, the single element LED chip, or the flip chip type. Various modifications are possible within the scope of the invention described in the claims, such as a die bond type, and it goes without saying that these are also included in the scope of the present invention. In addition, although the case where the current blocking layer is provided has been described in FIG. 1 and the embodiment, it has been described only in a preferable form.

It is a figure which shows the structure of the current blocking type point light source array type light emitting diode which has the structure of the light emitting diode which concerns on this invention. It is a figure which shows a 1st-4th process sequentially among the manufacturing processes of the point light source array type light emitting diode of FIG. It is a figure which shows the 5th-7th process sequentially among the manufacturing processes of the point light source array type light emitting diode of FIG. It is a figure which shows 8th-9th processes sequentially among the manufacturing processes of the point light source array type light emitting diode of FIG. (A)-(C) is each top view of Drawing 2 (B), (D), and Drawing 3 (B). (A), (B) is each top view of FIG.3 (C) and FIG.4 (C). It is the table | surface which showed each composition of the point light source array type light emitting diode in an Example and a comparative example, and the kind of dopant. It is a table | surface which shows the characteristic result (reverse voltage, optical output intensity, reliability) of the light emitting diode in each doping condition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Current blocking layer 3 Resist 5, 7 Clad layer 6 Active layer 15, 16 Electrode 17 Light emitting part 8 Separation groove 20 Point light source array type light emitting diode 20a to 20c Point light source array type light emitting diode element 21 One-dimensional point light source array LED chip

Claims (8)

A first cladding layer made of an Al _x Ga _1-x As layer (0 ≦ x ≦ 1) and a p-type active layer made of an Al _y Ga _1-y As layer (0 ≦ y ≦ 1, y <x) And a second clad layer made of an Al _z Ga _1-z As layer (0 ≦ z ≦ 1, y <z),
An amount of effective acceptor density of 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ when a Zn element alone is added as a dopant to the p-type active layer, when a Ge element is added alone An amount of effective acceptor density of 2 × 10 ¹⁸ cm ^{−3 in} which both Zn and Ge are added.   The light emitting diode according to claim 1, wherein the light emitting diode is of a conductive type and a reverse conductive type, and includes a current blocking layer having a function of blocking current.   A light-emitting diode comprising a plurality of light-emitting diode elements according to claim 1 or 2 on a single chip.   4. The light emitting diode according to claim 1, wherein the x, y, and z are 0.3, 0.03, and 0.3, respectively. ^2. The light emitting diode according to claim 1 , wherein the reverse voltage is 8 V or more when 5.66 × 10 ⁻² A / cm ^{2 is} energized in the reverse direction. In the method of manufacturing a light emitting diode in which the first cladding layer, the p-type active layer, and the second cladding layer are joined,
After growing an Al _x Ga _1-x As layer (0 ≦ x ≦ 1) as the first cladding layer,
When an element of Zn is added in an amount such that an effective acceptor density when it is added alone is 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ , an effective acceptor density when an element of Ge is added alone is 2 × 10 ¹⁸ cm ⁻³ is added to grow an Al _y Ga _1-y As layer (0 ≦ y ≦ 1, y <x) as the p-type active layer,
A method of manufacturing a light emitting diode, comprising growing an Al _z Ga _1-z As layer (0 ≦ z ≦ 1, y <z) as the second cladding layer on the active layer. 7. The method of manufacturing a light emitting diode according to claim 6 , wherein a current blocking layer is grown on the substrate and the current blocking layer at a predetermined location is removed before the first cladding layer is grown. . The light emitting diode according to claim 7 , wherein the current blocking layer is grown by MOCVD, and the first cladding layer, the p-type active layer, and the second cladding layer are grown by LPE. Manufacturing method.

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