JP3221635B2 - Nitrogen-3 group compound semiconductor photoexcited sapphire light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sapphire light emitting device using blue light emitted by a nitrogen-group III element compound semiconductor as excitation light.

[0002]

2. Description of the Related Art Conventionally, as a blue light emitting diode, a light emitting diode in which a GaN-based compound semiconductor is epitaxially grown on a sapphire substrate is known. Since the GaN-based compound semiconductor is a direct transition type, it has high luminous efficiency,
Attention has been paid to making blue and ultraviolet light, which is one of the three primary colors of light, the emission color.

[0003]

SUMMARY OF THE INVENTION The present inventors attempted to extract light through the sapphire substrate and emitted light of blue and ultraviolet light. if adding metal ions such as Cr ^+3, it is possible to use the light emitted from the GaN for excitation of metal ions such as chromium ions Cr ^+3, the photoexcited chromium ions Cr ⁺³ such metal ions Inspired by the fact that red emission can be obtained by transition to the ground level,
The present invention has been completed.

Conventionally, a ruby laser has been known, but there is a problem that an excitation light source becomes large and the whole apparatus is large. The present invention has been made in order to solve the above-described problems, and its object is to provide a system in which a red system, a mixed color of a red system and a blue system, and a red system and a blue system are separated and arranged in a plane. An object of the present invention is to provide a compact light emitting element capable of emitting light in a compact manner.

[0005]

According to the present invention, there is provided a sapphire substrate containing metal ions as active ions, and at least two kinds of layers epitaxially grown on the sapphire substrate directly or through a buffer layer, wherein Type of nitrogen-
Group 3 element compound semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0
And a p-type or i-type (semi-insulating)
Nitrogen-group III element compound semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y =
0, X = Y = 0), and an electrode for the first and second layers formed on the uppermost layer of the semiconductor layer laminated on the sapphire substrate. A light-excited sapphire light-emitting device is characterized in that light emitted by a layer and a second layer is incident on a sapphire substrate, the light is used to excite metal ions, and the light is emitted by transition to a ground level.

[0006]

In order to specifically explain the light emitting mechanism, the case where the metal ion added to the sapphire substrate is chromium ion Cr ⁺³ will be described below. Ground level of chromium ions Cr ⁺³ which is added to the sapphire substrate ⁴ A ₂
The transition from to the excitation level ⁴ T ₂ or ⁴ T ₁ is at a wavelength of 0.55 μ, 0.
This is possible with 42 μm light. By appropriately setting the component ratio of each element and the addition amount of the impurity element of the nitrogen-group III element compound semiconductor, light having a wavelength necessary for photoexcitation of the chromium ion Cr ⁺³ can be emitted.

This light is made incident on a sapphire substrate, and chromium ions Cr ⁺³ are excited from the ground level ⁴ A ₂ to the excited level ⁴ T ₂ or ⁴ T _1.
To be excited. Chromium ion Cr ⁺³ is excited level ⁴ T ₂ or ⁴ T
Non-radiative transition from ₁ to the metastable excited level ² E and radiative transition from the metastable excited level ² E to the ground level ⁴ A ₂ . This allows red light (0.693 μm, 0.692 μm) from the sapphire substrate
Was observed to be emitted.

When chromium ions Cr ⁺³ are not added to the sapphire substrate, the light emitted from the group III element compound semiconductor is transmitted without being absorbed by the sapphire substrate. Therefore, the light emitting device of the present invention can change the emission color in the range from red to blue by changing the concentration of chromium ion Cr ⁺³ added to the sapphire substrate. Also, chromium ion Cr on the sapphire substrate
By selectively adding ⁺³ , the portion to which chromium ion Cr ⁺³ is added is red, and the portion to which chromium ion Cr ^{+ 3} is not added is 2 like blue.
A light emitting element having a primary color point light source can also be used.

The above-described light emission mechanism is based on the fact that, in addition to chromium ion Cr ⁺³ , iron Fe, antimony Sb, manganese Mn, and molybdenum M
The same applies to metal ions such as o, cobalt Co and nickel Ni. Further, the present light emitting device can be made very small because the nitrogen-group III element compound semiconductor is epitaxially grown on the sapphire substrate and the nitrogen-group III element compound semiconductor is used as an excitation light source.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment In FIG.
⁺³ is added to the sapphire substrate 1 at a concentration of 0.05 wt% (2 × 10 ¹⁹ / cm ³ ).
1-20) A buffer layer 2 of 500 nm AlN is formed on the upper side. On the buffer layer 2, a film thickness of about 2.2 μm
m, the electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration comprising a silicon addition of GaN ³ n ⁺ layer 3, a thickness of about 1.5 [mu] m, the electron concentration 1
× 10 ¹⁶ / cm ³ Low carrier concentration n-layer 4 made of undoped GaN
Are formed. Further, on the low carrier concentration n layer 4, a low carrier concentration p layer 5 made of magnesium (Mg) doped GaN having a thickness of about 0.5 μm and a hole concentration of 1 × 10 ¹⁶ / cm ³ is sequentially formed.
1. A high carrier concentration p ⁺ layer 52 having a thickness of about 0.2 μm and a hole concentration of 2 × 10 ¹⁷ / cm ³ is formed. An electrode 7 made of nickel connected to the high carrier concentration p ⁺ layer 52 and an electrode 8 made of nickel connected to the high carrier concentration n ⁺ layer 3 are formed. The electrode 8 and the electrode 7 are electrically insulated and separated by the groove 9.

Next, a method of manufacturing the light emitting diode 10 having this structure will be described. The light emitting diode 10 includes:
It was manufactured by vapor phase growth by an organometallic compound vapor phase growth method (hereinafter referred to as “M0VPE”). The gas used was NH
₃ and the carrier gas H ₂ and trimethylgallium (Ga (CH _{3) 3)}
(Hereinafter referred to as "TMG") and trimethylaluminum (Al
(CH ₃ ) ₃ ) (hereinafter referred to as “TMA”), silane (SiH ₄ ), and biscyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).

First, the chromium ion Cr ⁺³ whose main surface is the a surface cleaned by organic cleaning and heat treatment has a concentration of 0.05 wt% (2 ×
The single crystal sapphire substrate 1 doped with 10 ¹⁹ / cm ³ )
Attach to a susceptor placed in the reaction chamber of the VPE device. Next, the sapphire substrate 1 was subjected to gas phase etching at a temperature of 1100 ° C. while flowing H ₂ at a flow rate of 2 liter / min at normal pressure into the reaction chamber.

[0013] Next, by lowering the temperature to 400 ° C., and H ₂
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 × 10 ^-5
The buffer layer 2 of AlN was formed to a thickness of about 500 ° by supplying at a rate of mol / min. Next, the temperature of the sapphire substrate 1 is set to 1150 ° C.
Held in the H ₂ 20 liter / min, the NH ₃ 10 liter / min, TM
Silane (SiH ₄ ) diluted to 1.7 × 10 ⁻⁴ mol / min with G and 0.86 ppm with H ₂ was supplied at a rate of 200 milliliter / min for 30 minutes to obtain a film thickness of about 2.2 μm and an electron concentration of 2 × 10 ¹⁸ / min. A high carrier concentration n ⁺ layer 3 made of GaN of cm ³ was formed.

Subsequently, the temperature of the sapphire substrate 1 is set to 1150 ° C.
, H ₂ at 20 liter / min, NH ₃ at 10 liter / min, TMG
At a rate of 1.7 × 10 ^-4 mol / min for 20 minutes,
A low carrier concentration n-layer 4 made of GaN having a thickness of 1.5 μm and an electron concentration of 1 × 10 ¹⁶ / cm ³ was formed.

Next, while maintaining the sapphire substrate 1 at 1150 ° C., H ₂ is 20 liter / min, NH ₃ is 10 liter / min, and TMG is
1.7 × 10 ⁻⁴ mol / min and CP ₂ Mg were supplied at a rate of 2 × 10 ⁻⁷ mol / min for 7 minutes to form a 0.5 μm-thick low carrier concentration p-layer 51 made of GaN. In this state, the low carrier concentration p layer 51 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, while maintaining the sapphire substrate 1 at 1150 ° C., H ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG
Was supplied at a rate of 1.7 × 10 ⁻⁴ mol / min and CP ₂ Mg at a rate of 3 × 10 ⁻⁶ mol / min for 3 minutes to form a 0.2 μm thick GaN high carrier concentration p ⁺ layer 52. In this state, the high carrier concentration p ⁺ layer 52 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, the above-mentioned high carrier concentration p ⁺ layer 52 and low carrier concentration p layer 5
1 was uniformly irradiated with an electron beam. The electron beam irradiation conditions were: acceleration voltage 10 KV, sample current 1 μA, beam moving speed 0.2 mm /
sec, the beam diameter is 60 μmφ, and the degree of vacuum is 2.1 × 10 ⁻⁵ Torr. By the irradiation of the electron beam, the low carrier concentration p layer 51 is formed.
Is a p-type semiconductor having a hole concentration of 1 × 10 ¹⁶ / cm ³ and a resistivity of 40 Ωcm, and the high carrier concentration p ⁺ layer 52 has a hole concentration of 2 × 10 ¹⁶ / cm ³ .
It became a p-type semiconductor having × 10 ¹⁷ / cm ³ and resistivity of 2Ωcm.
Thus, a wafer having a multilayer structure as shown in FIG. 2 was obtained.

FIGS. 3 to 7 described below are cross-sectional views showing only one device on the wafer. Actually, a wafer in which devices having the same structure are continuously formed is shown in FIG.
Processing is performed, and then the wafer is cut for each device.

As shown in FIG. 3, an SiO ₂ layer 11 is formed on the high carrier concentration p ⁺
It was formed in thickness. Next, a photoresist 12 was applied on the SiO ₂ layer 11. Then, by photolithography, on the high carrier concentration p ⁺ layer 52, the electrode formation site A corresponding to the hole 15 formed so as to reach the high carrier concentration n ⁺ layer 3 and the electrode formation portion are formed with the high carrier concentration p ⁺
The photoresist in the portion B where the groove 9 for insulating and separating from the electrode of the layer 52 was formed was removed.

Next, as shown in FIG. 4, the SiO ₂ layer 11 not covered with the photoresist 12 was removed with a hydrofluoric acid-based etchant. Next, as shown in FIG.
The upper surface of the high carrier concentration p ⁺ layer 52 at a portion not covered by the photoresist 12 and the SiO ₂ layer 11 and the lower carrier concentration p layer 51, the low carrier concentration n layer 4, and the high carrier concentration n ⁺ layer 3 The part was dry-etched by supplying a degree of vacuum of 0.04 Torr, high-frequency power of 0.44 W / cm ² , and BCl ₃ gas at a rate of 10 milliliter / min. In this step, a hole 15 for extracting an electrode from the high carrier concentration n ⁺ layer 3 and a groove 9 for insulating and separating were formed.

Next, as shown in FIG. 6, the SiO ₂ layer 11 remaining on the high carrier concentration p ⁺ layer 52 was removed with hydrofluoric acid. Next, as shown in FIG.
The nickel layer 13 was formed by vapor deposition. As a result, the nickel layer 13 electrically connected to the high carrier concentration n ⁺ layer 3 is formed in the hole 15. Then, a photoresist 14 is applied on the nickel layer 13, and a predetermined photolithography is performed so that the photoresist 14 has an electrode portion for the high carrier concentration n ⁺ layer 3 and the high carrier concentration p ⁺ layer 52. A pattern was formed into a shape.

Next, as shown in FIG. 7, the exposed portion of the lower nickel layer 13 was etched with a nitric acid-based etchant using the photoresist 14 as a mask. At this time, the nickel layer 13 deposited on the trench 9 for insulation isolation is completely removed. Next, the photoresist 14 was removed with acetone, and the electrode 8 of the high carrier concentration n ⁺ layer 3 and the electrode 7 of the high carrier concentration p ⁺ layer 52 were left. Thereafter, the wafer processed as described above was cut into individual devices to obtain a gallium nitride-based light emitting device having a pn structure shown in FIG.

When a drive current of 20 mA was applied to the light emitting diode 10 manufactured as described above, red light (0.693 μm, 0.692 μm) was observed to be emitted from the sapphire substrate 1.

When a sapphire substrate to which chromium ions were not added was used, blue light emitted from a GaN semiconductor having a center wavelength of 0.390 μm was observed.

This mechanism is considered as follows. The photoluminescence intensity of GaN doped with magnesium Mg has the distribution shown in FIG. The central wavelength is 0.390 μm. Therefore, the low carrier concentration n layer 4 and the low carrier concentration p
The spectral distribution of light emitted from the layer 51 also has characteristics as shown in FIG. As shown in FIG. 10, light of this wavelength causes the chromium ion Cr ³⁺ to move from the ground level ⁴ A ₂ to the excited level ⁴ T ₁
Can be transitioned to The chromium ion Cr ³⁺ is relaxed by a non-radiative transition from the excited level ⁴ T ₁ to the metastable excited level ² E. Then, light is emitted by the relaxation of the chromium ion Cr ^{3+ from} the metastable excited level ² E to the ground level ⁴ A ₂ . As shown in FIG. 9, the light passing through the sapphire substrate 1 to which the chromium ion Cr ³⁺ is added has two wavelengths of 0.693 μm (1.788 eV: R ₁ line) and 0.692 μm (1.792 eV: R ₂ line). The line spectrum of the book is shown.

In the above embodiment, the low carrier concentration n layer 4 and the low carrier concentration p layer 51 contributing to light emission are
Formed by a nitrogen-group III element compound semiconductor (Al _x Ga _Y In
_1-XY N; including X = 0, Y = 0, and X = Y = 0).
In addition, the above-mentioned nitrogen-3 group element compound semiconductor (Al _x Ga _Y In _1-XY
A MIS structure using an i-type (semi-insulating) layer in which Zn is added to N; X = 0, Y = 0, and X = Y = 0) and an n-type layer may be used. Addition ratio of impurity element to be added and nitrogen-group III element compound semiconductor (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0)
By appropriately selecting the component ratio, light having a wavelength including 0.55 μm and 0.42 μm necessary for exciting the chromium ion Cr ³⁺ can be emitted. As a result, red (0.693 μm, 0.692 μm) light can be obtained from the sapphire substrate.

It is desirable that the concentration of chromium ion Cr ³⁺ added to the sapphire substrate 1 is 1 wt% or less. Chromium ion
Even when the concentration of Cr ³⁺ was 5 × 10 ¹⁶ / cm ³ , the above red light emission was observed. At present, the most desirable chromium ion Cr ³⁺
The concentration is 0.05 wt% (2 × 10 ¹⁹ / cm ³ ). By changing the concentration of the chromium ion Cr ³⁺ added to the sapphire substrate 1, light of a mixed color from red to blue can be obtained. Further, by selectively adding chromium ions Cr ³⁺ to the sapphire substrate 1, a red light source and a blue light source can be made extremely close to each other in a plane, or a two-primary dot matrix flat display can be obtained. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a first specific example of the present invention.

FIG. 2 is a sectional view showing a manufacturing process of the light-emitting diode of the embodiment.

FIG. 3 is a sectional view showing a manufacturing step of the light-emitting diode of the embodiment.

FIG. 4 is a sectional view showing a manufacturing step of the light-emitting diode of the same embodiment.

FIG. 5 is a sectional view showing the manufacturing process of the light emitting diode of the same embodiment.

FIG. 6 is a sectional view showing the manufacturing process of the light-emitting diode of the example.

FIG. 7 is a sectional view showing the manufacturing process of the light emitting diode of the same embodiment.

FIG. 8 is a characteristic diagram obtained by measuring a photoluminescence spectrum of GaN to which magnesium Mg is added.

FIG. 9 is a characteristic diagram obtained by measuring a photoluminescence spectrum of light grown on a sapphire substrate to which chromium ion Cr ³⁺ is added and passed through a GaN sapphire substrate to which magnesium Mg is added.

FIG. 10 is an explanatory diagram illustrating the photoexcitation and light emission mechanisms of a sapphire substrate to which chromium ions Cr ³⁺ are added.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration n ⁺ layer 4 ... Low carrier concentration n layer 51 ... Low carrier concentration p layer 52 ... High carrier concentration p ⁺ layer 7, 8 ... Electrode 9 ... Groove

──────────────────────────────────────────────────続 き Continuing on the front page (73) Patent holder 591014949 Isamu Akasaki 1-38-805, Joshin, Nishi-ku, Nagoya-shi, Aichi Prefecture (73) Patent holder 591014950 Hiroshi Amano 2-104 Yamanote, Naito-ku, Nagoya-shi, Aichi Takara Mansion Yamanote 508 (72) Inventor Karin Meyer Germany 8000 München 19 Leonrotstraße 54 Fraunhofer-Geselshaft z Federlung der Angevannten Forschunk A. (72) Inventor Jürgen Schneider Germany 8000 München 19 Leonrottstrasse 54 Fraunhofer-Geselshaft zer Felderung der Angevann ten Forschunk A. Fao. (72) Inventor Isamu Akasaki 1-38-805, Joshin 1-chome, Nishi-ku, Nagoya, Aichi Prefecture (72) Inventor Hiroshi Amano 2--21, Jingu-cho, Meito-ku, Nagoya-shi, Aichi Prefecture Room No. 19, Building 103, Nijigaoka East Complex (72 ) Inventor Katsuhide Shinbe 1 Ogataai Ogata, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. (56) References JP-A-3-218625 (JP, A) JP-A-2-229475 (JP, A) Jpn. J. Appl. Phys. Part 2, Vol. 32, No. 6B, p. L846-L848 Appl. Phys. Lett. Vol. 64, no. 7, p. 857-859 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 33/00

Claims (4)

(57) [Claims] 1. An n-type sapphire substrate containing metal ions as active ions, and at least two types of first and second layers epitaxially grown on the sapphire substrate directly or via a buffer layer. Nitrogen-group III element compound semiconductor (Al _x Ga _Y In _1-XY N; X =
0, Y = 0, X = Y = 0) and a p-type or i-type (semi-insulating) nitrogen-group III element compound semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y = 0, and X = Y = 0), and the first layer and the second layer formed on the uppermost layer of a semiconductor layer laminated on the sapphire substrate. And light emitted by the first layer and the second layer is incident on the sapphire substrate, and the light is used to excite metal ions and emit light by transition to a ground level. Photo-excited sapphire light emitting device. 2. The light-excited sapphire light emitting device according to claim 1, wherein said metal ion is said chromium ion Cr ⁺³ , and said chromium ion Cr ⁺³ is contained in said sapphire substrate in an amount of 1 wt% or less. . 3. The photoexcited sapphire light emitting device according to claim 1, wherein said second layer is doped with magnesium Mg or zinc Zn. 4. The light-excited sapphire light-emitting device according to claim 1, wherein said second layer is a layer exhibiting p-type upon irradiation with an electron beam after magnesium Mg is added.