JP2015008317A - Ga2O3 semiconductor substrate structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a GaOsemiconductor substrate structure which uses a GaOcompound as a semiconductor and has an electrode capable of securing ohmic characteristics suitable for the GaOcompound.SOLUTION: A light emitting element 1 including a GaOsemiconductor substrate structure comprises: an n-type β-AlGaOclad layer 4 composed of a β-AlGaO3 compound semiconductor and exhibiting n-type conductivity, an active layer 5 composed of β-GaOand a p-type β-AlGaOclad layer 6 exhibiting p-type conductivity, which are laminated on an n-type β-GaOsubstrate 2; and an n-side electrode 20 including a Ti film ohmic-connected to the n-type β-GaOsubstrate 2.

Description

The present invention relates to a Ga ₂ O ₃ compound semiconductor substrate structure provided with an electrode having ohmic characteristics.

  Conventionally, nitride semiconductors, in particular, gallium nitride (GaN) -based compound semiconductor light-emitting elements are used in light-emitting devices such as LEDs and LDs (see, for example, Patent Document 1).

  Patent Document 1 discloses a GaN-based blue light emitting device in which a sapphire substrate, a buffer layer, an n-type gallium nitride compound semiconductor layer, an n-type cladding layer, an n-type active layer, a p-type cladding layer, and a p-type contact layer are stacked. Have been described. This conventional GaN-based blue light emitting device emits light at an emission wavelength of 370 nm.

Japanese Patent No. 2778405 (FIG. 1)

However, in the conventional GaN-based blue light-emitting element, it is difficult to obtain a light-emitting element that emits light in the ultraviolet region of a shorter wavelength because of the band gap. Therefore, in recent years, Ga ₂ O ₃ is expected as a substance having a larger band gap and capable of emitting light in the ultraviolet region.

Accordingly, an object of the present invention is to provide a Ga ₂ O ₃ based semiconductor substrate structure having an electrode that can achieve ohmic characteristics.

In order to achieve the above object, the present invention provides a Ga ₂ O ₃ based semiconductor substrate structure including an n-type β-Ga ₂ O ₃ substrate and an n-side electrode including an ohmic-connected Ti film.

According to the Ga ₂ O ₃ based semiconductor substrate structure of the present invention, it is possible to have an electrode capable of obtaining ohmic characteristics with respect to the Ga ₂ O ₃ based semiconductor substrate.

It is sectional drawing which shows the light emitting element which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the light emitting element which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the light emitting element which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the light emitting element which concerns on the 4th Embodiment of this invention. 2 is a current-voltage characteristic diagram of Example 1. FIG. 6 is a current-voltage characteristic diagram at 25 ° C. in Example 2. FIG. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 300 degreeC in Example 2. FIG. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 600 degreeC in Example 2. FIG. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 700 degreeC in Example 2. FIG. 6 is a current-voltage characteristic diagram at 25 ° C. in Example 3. FIG. It is a current-voltage characteristic figure after hold | maintaining at 800 degreeC in Example 3 for 5 minutes. It is a current-voltage characteristic figure in 25 degreeC in Example 4. It is a current-voltage characteristic figure after hold | maintaining at 700 degreeC in Example 4 for 5 minutes. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 800 degreeC in Example 4. 10 is a current-voltage characteristic diagram at 25 ° C. in Example 5. FIG. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 400 degreeC in Example 5. FIG. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 800 degreeC in Example 5. FIG. 6 is a current-voltage characteristic diagram at 25 ° C. in Comparative Example 1. FIG. It is a current-voltage characteristic figure after hold | maintaining for 10 minutes at 100 degreeC in the comparative example 1. It is a current-voltage characteristic figure after hold | maintaining for 10 minutes at 200 degreeC in the comparative example 1. 6 is a current-voltage characteristic diagram at 25 ° C. in Comparative Example 2. FIG. It is a current-voltage characteristic figure after hold | maintaining for 10 minutes at 100 degreeC in the comparative example 2. 10 is a current-voltage characteristic diagram at 25 ° C. in Comparative Example 3. FIG. It is a current-voltage characteristic figure after hold | maintaining at 100 degreeC in Comparative Example 3 for 30 second. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 100 degreeC in the comparative example 3. It is a current-voltage characteristic figure after hold | maintaining for 30 second at 200 degreeC in the comparative example 3. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes at 200 degreeC in the comparative example 3.

[First Embodiment]
FIG. 1 shows a light emitting device including a substrate structure according to a first embodiment of the present invention. The light emitting element 1, _β-Ga 2 _{O 3} compound to the n-type _β-Ga 2 _{O 3} substrate 2 made of semiconductor, β-AlGaO ₃ Compound n-type an n-type conductivity comprising a semiconductor β-AlGaO ₃ cladding layer 4, active layer 5 made of β-Ga ₂ O ₃ , p-type β-AlGaO ₃ cladding layer 6 showing p-type conductivity, and p-type β showing p-type conductivity made of a β-Ga ₂ O ₃ compound semiconductor in which sequentially laminated the -ga ₂ O ₃ contact layer 7.

The light-emitting element 1 is formed of a transparent electrode 8 formed on the p-type β-Ga ₂ O ₃ contact layer 7 and a thin film made of Pt formed on a part of the transparent electrode 8, and the wire 11 is bonded to the light-emitting element 1. The pad electrode 9 connected by the part 10 and the n-side electrode 20 formed below the n-type β-Ga ₂ O ₃ substrate 2 are provided.

  The n-side electrode 20 is connected to a printed circuit board 30 on which a thin film made of Ti, for example, is formed and a print pattern (not shown) is formed via an adhesive 31.

  The light emitting element 1 is mounted on the printed circuit board 30 via an adhesive 31 or a metal paste, and is connected to the printed wiring of the printed circuit board 30.

  Each of the layers 4 to 7 constituting the light emitting element 1 is irradiated with laser light on a metal target, for example, by a PLD (Pulsed Laser Deposition) method in which a metal film released from the substrate is grown on the substrate in a dilute oxygen atmosphere. It is formed.

According to the first embodiment, the n-side electrode 20 has preferable ohmic characteristics with the n-type β-Ga ₂ O ₃ substrate 2. Therefore, since the contact resistance can be reduced, it is possible to obtain excellent light emission characteristics that can prevent current loss in the electrode portion, electrode deterioration due to generation of Joule heat, and compound semiconductor laser and LED characteristics. .

[Second Embodiment]
FIG. 2 is a view showing a light emitting device including a substrate structure according to the second embodiment of the present invention. This light emitting element 1 is different from the light emitting element 1 according to the first embodiment only in the n-side electrode 20. The n-side electrode 20 of the light-emitting element 1 is obtained by forming a Ti layer 21 on the lower surface of the n-type β-Ga ₂ O ₃ substrate 4 and forming an Au layer 22 below the Ti layer 21. A Pt layer may be used instead of the Au layer 22.

According to the second embodiment, the n-side electrode 20 has preferable ohmic characteristics with the n-type β-Ga ₂ O ₃ substrate 2. Therefore, the contact resistance between the n-side electrode 20 and the n-type β-Ga ₂ O ₃ substrate 2 can be reduced, and excellent light emission characteristics can be obtained as in the first embodiment.

[Third Embodiment]
FIG. 3 shows a main part of a light emitting device including a substrate structure according to the third embodiment of the present invention. This light emitting element 1 is different from the light emitting element 1 according to the first embodiment only in the n-side electrode 20. The n-side electrode 20 of the light emitting element 1 is obtained by sequentially laminating a Ti layer 21, an Al layer 23, and an Au layer 22 on the lower surface of the n-type β-Ga ₂ O ₃ substrate 2.

According to the third embodiment, the n-side electrode 20 has preferable ohmic characteristics with the n-type β-Ga ₂ O ₃ substrate 2. Therefore, excellent light emission characteristics can be obtained as in the first embodiment.

[Fourth Embodiment]
FIG. 4 shows a main part of a light emitting device including a substrate structure according to the fourth embodiment of the present invention. This light emitting element 1 is different from the light emitting element 1 according to the first embodiment only in the n-side electrode 20. The n-side electrode 20 of the light emitting element 1 is obtained by sequentially laminating a Ti layer 21, an Al layer 23, a Ni layer 24, and an Au layer 22 on the lower surface of the n-type β-Ga ₂ O ₃ substrate 2.

According to the fourth embodiment, the n-side electrode 20 has preferable ohmic characteristics with the n-type β-Ga ₂ O ₃ substrate 2. Therefore, excellent light emission characteristics can be obtained as in the first embodiment.

Examples of the present invention will be described below.
Example 1

  FIG. 5 is a current-voltage characteristic diagram of Example 1 of the present invention.

Example 1 corresponds to the first embodiment of the present invention, in which an n electrode is formed by a Ti layer formed on a substrate not added with a 99.99% Ga ₂ O ₃ dopant. is there. Etching was performed before the Ti layer was formed on the substrate to clean the substrate surface. The Ti layer had a thickness of 150 mm and was formed by irradiating a Ti target with a laser for 7.5 minutes at an output of 100 mW by the PLD method, and the current-voltage characteristics at 25 ° C. were measured.

According to Example 1, since it exhibits ohmic characteristics at 25 ° C., excellent light emission that can prevent current loss in the electrode part, electrode deterioration due to generation of Joule heat, and compound semiconductor laser and LED characteristics deterioration. Characteristics are obtained.
(Example 2)

6 is a current-voltage characteristic diagram at 25 ° C. in Example 2 of the present invention, FIG. 7 is a current-voltage characteristic diagram after holding at 300 ° C. for 5 minutes in Example 2, and FIG. 8 is 600 ° C. in Example 2. 5
FIG. 9 is a current-voltage characteristic diagram after holding for 5 minutes at 700 ° C. in Example 2. FIG.

Example 2 corresponds to the second embodiment, in which an n-electrode is formed by laminating a Ti layer and an Au layer on a substrate not added with a 99.99% Ga ₂ O ₃ dopant. . Etching was performed in the same manner as in Reference Example 1 to clean the substrate surface. The Ti layer has a thickness of 150 mm and A
The u layer has a thickness of 500 mm, and is formed by irradiating the Ti target with a laser for 7.5 minutes and the Au target for 25 minutes with an output of 100 mW, respectively, by the PLD method. The electrode was held while flowing N ₂ at 200 ml / min, and the current-voltage characteristics after the holding were measured.

  According to Example 2, the current-voltage characteristic after hold | maintaining at 25 to 600 degreeC shows ohmic characteristics. However, after holding at 700 ° C. for 5 minutes, Schottky characteristics were exhibited.

Further, according to Example 2, ohmic characteristics are exhibited only by forming a Ti layer and an Au layer. Moreover, since an electrode shows ohmic characteristics in the range of 25 to at least 600 ° C., it can be used under a wide range of usage conditions from room temperature to a temperature requiring heat resistance.
Example 3

  FIG. 10 is a current-voltage characteristic diagram at 25 ° C. in Example 3 of the present invention, and FIG. 11 is a current-voltage characteristic diagram after holding at 800 ° C. for 5 minutes in Example 3.

Example 3 corresponds to the second embodiment, in which an n-electrode is formed by a Ti layer and an Al layer formed on a substrate to which 99.99% Ga ₂ O ₃ dopant is not added. .
Etching was performed in the same manner as in Example 1 to clean the substrate surface. The Ti layer has a thickness of 150 mm and the Al layer has a thickness of 1000 mm, and is formed by irradiating the Ti target with a laser for 7.5 minutes and the Al target with a laser for 50 minutes, respectively, at an output of 100 mW by the PLD method. The N ₂ was held while flowing at 200 ml / min, and the current-voltage characteristics after the holding were measured.

  According to Example 3, good ohmic characteristics are exhibited at 25 to 700 ° C., and current is less likely to flow after being held at 800 ° C., but ohmic characteristics are exhibited.

Further, according to Example 3, ohmic characteristics are exhibited only by forming a Ti layer and an Al layer.
Example 4

  12 is a current-voltage characteristic diagram at 25 ° C. in Example 4 of the present invention, FIG. 13 is a current-voltage characteristic diagram after holding at 700 ° C. for 5 minutes in Example 4, and FIG. 14 is 800 ° C. in Example 4. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes.

Example 4 corresponds to the third embodiment, and an n electrode was formed by a Ti layer, an Al layer, and an Au layer formed on a substrate to which no 99.99% Ga ₂ O ₃ dopant was added. Is. Etching was performed in the same manner as in Example 1 to clean the substrate surface. The Ti layer has a thickness of 150 mm, the Al layer has a thickness of 1000 mm, and the Au layer has a thickness of 500 mm. By the PLD method, the output is 100 mW, the Ti target is 7.5 minutes, the Al target is 50 minutes, and the Au target is Each is formed by irradiating with a laser for 25 minutes. The N ₂ was held while flowing at 200 ml / min, and the current-voltage characteristics after the holding were measured.

According to Example 4, ohmic characteristics are exhibited at 25 to 700 ° C., but after holding at 800 ° C. or higher, Schottky characteristics are exhibited. Moreover, an electrode shows ohmic characteristics only by forming a Ti layer, an Al layer, and an Au layer.
(Example 5)

  15 is a current-voltage characteristic diagram at 25 ° C. in Example 5 of the present invention, FIG. 16 is a current-voltage characteristic diagram after holding at 400 ° C. for 5 minutes in Example 5, and FIG. 17 is 800 ° C. in Example 5. It is a current-voltage characteristic figure after hold | maintaining for 5 minutes.

Example 5 corresponds to the fourth embodiment. The Ti layer, the Al layer, the Ni layer, and the Au layer formed on the substrate to which the 99.99% Ga ₂ O ₃ dopant was not added were used. An electrode is formed. Etching was performed in the same manner as in Example 1 to clean the substrate surface. The Ti layer has a thickness of 150 mm, the Al layer has a thickness of 1000 mm, the Ni layer has a thickness of 400 mm, and the Au layer has a thickness of 500 mm. The target is formed by irradiating the target with a laser for 50 minutes, the Ni target for 40 minutes, and the Au target for 25 minutes. The N ₂ was held while flowing at 200 ml / min, and the current-voltage characteristics after the holding were measured.

According to Example 5, ohmic characteristics are exhibited after being held at 25 ° C. and 400 ° C., but Schottky characteristics are exhibited after being held at 800 ° C. Moreover, ohmic characteristics are exhibited only by forming a Ti layer, an Al layer, a Ni layer, and an Au layer. When heat treatment is performed, 2
Since it exhibits ohmic characteristics in the range of 5 to at least 400 ° C., it can be used under a wide range of usage conditions from room temperature to a temperature requiring heat resistance.

Hereinafter, Comparative Examples 1 to 3 of the present invention will be described.
(Comparative Example 1)

  18 is a current-voltage characteristic diagram at 25 ° C. in Comparative Example 1, FIG. 19 is a current-voltage characteristic diagram after holding at 100 ° C. for 10 minutes in Comparative Example 1, and FIG. It is a current-voltage characteristic figure after hold | maintaining.

In Comparative Example 1, an n-electrode is formed by using an Au layer instead of a Ti layer on a substrate to which 99.99% Ga ₂ O ₃ dopant is not added. Etching was performed before the Au layer was formed on the substrate to clean the substrate surface. The Au layer is formed by irradiating the Au target with laser at an output of 100 mW for 25 minutes by the PLD method. The current-voltage characteristics were measured after heat-treating and holding Ar at a flow rate of 200 ml / min in a 5% H ₂ atmosphere.

According to Comparative Example 1, when an Au layer is provided on the Ga ₂ O ₃ substrate instead of the Ti layer, Schottky characteristics are exhibited and ohmic characteristics are not exhibited.
(Comparative Example 2)

  FIG. 21 is a current-voltage characteristic diagram at 25 ° C. in Comparative Example 2, and FIG. 22 is a current-voltage characteristic diagram after holding at 100 ° C. for 10 minutes in Example 2.

In Comparative Example 2, an n-electrode is formed by a Pt layer instead of a Ti layer on a substrate to which 99.99% Ga ₂ O ₃ dopant is not added. Etching was performed in the same manner as in Comparative Example 1 to clean the substrate surface. The Pt layer is formed by irradiating a Pt target with a laser at an output of 100 mW by the PLD method. The current-voltage characteristics were measured after heat-treating and holding Ar at a flow rate of 200 ml / min in a 5% H ₂ atmosphere.

According to Comparative Example 2, when an Au layer is provided on the Ga ₂ O ₃ substrate instead of the Ti layer, Schottky characteristics are exhibited and ohmic characteristics are not exhibited.
(Comparative Example 3)

  23 shows a current-voltage characteristic diagram at 25 ° C. in Comparative Example 3, FIG. 24 shows a current-voltage characteristic diagram after holding at 100 ° C. for 30 seconds in Comparative Example 3, and FIG. FIG. 26 is a current-voltage characteristic diagram after being held at 200 ° C. for 30 seconds in Comparative Example 3, and FIG. 27 is a current-voltage characteristic diagram after being held at 200 ° C. for 5 minutes in Comparative Example 3. FIG.

In Comparative Example 3, an n-electrode was formed by laminating a Ni layer and an Au layer instead of a Ti layer and an Au layer on a substrate to which no 99.99% Ga ₂ O ₃ dopant was added. Etching was performed in the same manner as in Comparative Example 1 to clean the substrate surface. The Ni layer has a thickness of 400 mm and the Au layer has a thickness of 500 mm. The Ni layer is first formed by the PLD method, and then the Au target is irradiated with a laser for 25 minutes at an output of 100 mW. The N ₂ was held while flowing at 200 ml / min, and the current-voltage characteristics after the holding were measured.

  According to Comparative Example 3, when the Ni layer and the Au layer are provided instead of the Ti layer and the Au layer, the Schottky characteristics are shown and the ohmic characteristics are not shown.

  In addition, this invention is not limited to said each embodiment and said each Example, You may change variously within the range which does not change the summary.

1 the light emitting element 2 substrate 4 n-type β-AlGaO ₃ cladding layer 5 active layer 6 p-type β-AlGaO ₃ cladding layer 7 p-type _β-Ga 2 _{O 3} contact layer 8 transparent electrode 9 pad electrode 10, 12 junction 11, 13 Wire 20 N-side electrode 21 Ti layer 22 Au layer 23 Al layer 24 Ni layer 30 Printed circuit board 31 Adhesive 40 Emission light 41 Emission light

Claims (1)

an n-type β-Ga ₂ O ₃ substrate;
An n-side electrode including a Ti film ohmically connected to the n-type β-Ga ₂ O ₃ substrate;
A Ga ₂ O ₃ based semiconductor substrate structure including:

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