JPH0951139A - Semiconductor laser device - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to realize a laser device in a blue-violet wavelength region that operates at a low threshold value. [Structure] Ti nitride TiN _x (0 <x ≦, on a sapphire substrate 1 having a (0001) C plane, with a stripe-shaped window in the center
The pattern 2 of 1) is formed, and the insulating film mask pattern 3 is used to fabricate a waveguide resonance structure made of an AlGaInN material by a selective growth technique. As for the waveguide structure,
A BH structure in which the light emitting active layer 6 is embedded in the optical waveguide layer can be formed. Next, after vapor-depositing the n-side electrode Ti / Au in contact with TiN _x (0 <x ≦ 1) and Ni / Au on the p-side electrode,
An element is obtained by cleaving. [Effect] In the present embodiment, a high melting point Ti is used for the n-type electrode material.
By forming the TiN _x (0 <x ≦ 1) nitride material in advance, the selective lateral growth is performed only once, and the basic lateral mode is controlled by the difference in the actual refractive index so that the laser light can be emitted. Embedded with stable propagation
A (BH) waveguide structure could be produced. This device caused laser oscillation in the wavelength range of 410 to 430 nm by current injection.
Further, by devising the insulating film mask pattern, a lower threshold operation was possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device suitable for optical information terminals or optical measurement light sources.

[0002]

2. Description of the Related Art Conventionally, a light emitting device using a GaInN / AlGaN material has been described, for example, Applied Physics Letters, 1994, 64, 1687-1689 (Appl. Phys. Lett., 64, 1
687-1689 (1994).) Describes an element structure constituting a blue light emitting diode.

[0003]

Although the above-mentioned prior art refers to the light emitting active layer and the optical waveguide layer constituting the blue light emitting diode, the waveguide resonance structure required for the laser diode is manufactured. It does not describe the process of doing. Also,
The element structure for controlling the lateral mode of the semiconductor laser and the method of manufacturing the same have not been described.

An object of the present invention is to form a waveguide resonance structure suitable for a semiconductor laser by one-time crystal growth in a Nitride material, which has been difficult to form a waveguide or a resonator, and to use an electrode material. Another object is to easily achieve an element structure having a basic lateral mode control structure by defining the configurations of electrodes and crystal layers. Another object is to realize a laser device in the blue-violet wavelength range that operates at a lower threshold.

[0005]

Means for achieving the above object will be described below.

In the present invention, a method for easily forming a waveguide resonance structure by one-time crystal growth is used for a Nitride material, which has conventionally been difficult to form a waveguide or a resonator. Has a high melting point on the single crystal substrate and
Ti, which is a material with high ohmic properties to Nitride materials
By forming the nitride TiN _x (0 <x ≦ 1) in advance, and then using the selective growth technique, the waveguide resonant structure can be manufactured on the substrate by single crystal growth. In this waveguide resonance structure, a basic lateral mode control embedded BH structure based on the difference in real refractive index in which the light emitting active layer is embedded in the optical waveguide layer can be easily achieved. Furthermore, with the BH structure produced by devising an insulating film mask pattern for selective growth containing a dummy pattern, an element operating at a lower threshold can be realized.

[0007]

The operation of the above means for achieving the object will be described.

According to the present invention, it is possible to easily form Ni by a single crystal growth.
It is the content of devising a waveguide resonance structure using a tride material, and uses Ti nitride TiN _x (0 <x ≦ 1) as a constituent element for the n-side electrode with respect to the n-type crystal layer. Is characterized by. The main object of the present invention is to find a feature in the structure of the metal Ti nitride and the electrode crystal layer.

To form Ti nitride TiN _x (0 <x ≦ 1), which is a material having a high melting point and a high ohmic property on a Nitride material, on a single crystal substrate in advance. Due to
You can take advantage of the following two advantages. One is nitride TiN _x is Nitr
Since the Schottky barrier for the ide material is extremely low compared to other materials, it is utilized that it has excellent ohmic characteristics as an electrode material. Even for narrow waveguide stripes, if TiN _x is provided on the substrate in advance and arranged so as to contact the Nitride crystal layer, the n-side electrode can be easily manufactured and a current can be injected into the device. Can be taken. n type Ni
contact resistance between the tride crystal layer and the n-side electrode, 1 to 5 × 10- ⁶
It was possible to set in the range of Ωcm ² . The other is that by utilizing the fact that Ti nitride is a high melting point material having the above advantages, an optical waveguide structure can be formed on a substrate by a single crystal growth. The melting point of Ti nitride is about 29.
Since the temperature is 50 ° C, it has sufficient durability against the high temperature growth of Nitride material performed at 1000 ° C or higher. Therefore, _if a pattern of TiN _x , which is arranged in consideration of later formation of the n-side electrode and contact with the n-type Nitride crystal layer, is formed on the substrate in advance, the selective growth technique is then performed. By utilizing, it is possible to fabricate a waveguide resonance structure by performing crystal growth once. The waveguide resonance structure of the present invention has a form in which a light emitting active layer is embedded in an optical waveguide layer, and can be a basic lateral mode control BH structure based on a difference in actual refractive index. With this BH structure, low threshold operation of the device can be easily achieved.

The Ti nitride TiN _x (0 <x ≦ 1) can be produced by reacting metallic Ti with a nitrogen raw material or a Nitride material, or
Either by reacting the compound with a nitrogen source as a plasma source by ECR, or by a thermal decomposition gas phase reaction of an organic nitrogen Ti metal compound. After forming Ti nitride on the single crystal substrate by these methods, patterning is performed by lithography and etching. After this, a waveguide structure made of Nitiride material is provided by selective growth so as to be in contact with the patterned Ti nitride.

As described above, by producing an optical waveguide structure by selective growth using Ti nitride, a BH structure which can be controlled in the basic lateral mode can be produced, and an AlGaInN semiconductor laser which can be expected to have a low threshold operation. It can be realized.

[0012]

【Example】

Embodiment 1 An embodiment of the present invention will be described with reference to FIGS. 1 (a) and 1 (b). FIG.
In (a), with respect to the α-Al ₂ O ₃ substrate 1 having a (0001) C plane, Ti metal is reacted with a nitrogen raw material to be nitrided, or organic nitrogen Ti metal is thermally reacted, or Ti metal is used. Reacting the compound with nitrogen by electron cyclotron resonance (ECR),
First, a Ti nitride TiN _x (0 <x ≦ 1) layer 2 is formed. afterwards,
It is processed into a pattern having a striped window portion by using lithography. Next, an insulating film SiO ₂ mask 3 for selective growth is provided as shown in FIG. At this time, a stripe-shaped insulating film mask window region having a mask interval of 1 to 5 μm is formed by forming an insulating film and lithography, and the stripe direction is parallel to the (11-20) A plane of the α-Al ₂ O ₃ substrate 1. Set in the direction. Furthermore, as shown in FIG. 1 (a), nitride TiN
_The width of the stripe-shaped insulating film mask window region is set to be wider than the stripe width of the _x (0 <x ≦ 1) layer 2.
A nitride crystal layer is provided on the N _x (0 <x ≦ 1) layer 2 so as to be in contact therewith. Prior to crystal growth, the surface of the substrate 1 was subjected to a nitriding treatment with ammonia, and subsequently, the GaN buffer layer 4 was formed by metalorganic vapor phase epitaxy.
A compressive strain multiple quantum well active layer 6 composed of an n-type GaN optical waveguide layer 5, an AlGaN optical separation / confinement layer, a GaN quantum barrier layer, and a GaInN quantum well layer 6, and a p-type GaN optical waveguide layer 7 are selectively grown in order.
Next, the insulating film 8 is formed, and Ni is formed by lithography.
A p-side electrode 9 made of / Au and an n-side electrode 10 made of Ti / Au in contact with the nitride TiN _x (0 <x ≦ 1) layer 2 are vapor-deposited. Further, by cleaving the substrate in a direction perpendicular to the waveguide, the device vertical section shown in FIG. 1A is obtained.

According to the present embodiment, the BH stripe structure for guiding the laser light with the difference in the actual refractive index could be produced by one selective growth. By providing the TiN _x (0 <x ≦ 1) layer 2, it is possible to reduce the contact resistance of the n-side electrode.
Contact resistance between -type GaN crystal layer to obtain a value in the range of 3~5 × 10- ⁶ Ωcm ^2. This device lased at room temperature and had an oscillation wavelength in the range of 410 to 430 nm.

Embodiment 2 Another embodiment of the present invention will be described with reference to FIGS. 2 (a) and 2 (b). An element is manufactured in the same manner as in Example 1, but the dummy shown in FIG.
An insulating film mask 3 including a pattern is formed. The crystal layer on the dummy pattern is covered with an insulating film 8 as shown in FIG. 2 (a). Then, in the same manner as in Example 1, the element vertical section shown in FIG.

According to the present embodiment, the crystallinity and shape controllability of the striped waveguide can be significantly improved as compared with the first embodiment due to the effect of the dummy pattern, and the low threshold operation is achieved. The threshold current of this device is 2/3 to 1 as compared with the first embodiment.
It was reduced to / 2.

Embodiment 3 Another embodiment of the present invention will be described with reference to FIGS. 3 (a), 3 (b) and 4. The optical waveguide layer 7 is prepared in the same manner as in Example 1, but the direction in which the waveguide is formed is different from that in Examples 1 and 2 in the direction perpendicular to the (11-20) A plane of the substrate 1. Form waveguide stripes. Further, similarly to the second embodiment, after the crystal growth up to the layer 7, the Andorp strain compensation GaInN / AlGaNDBR structure high reflection film 11 is selectively grown. Further, using the lithography and the insulating film mask 8, the layer 11 is etched to reach the layer 7 in the waveguide stripe in the central portion. Then, in the same manner as in Example 1, the element vertical section of FIG. 3A and the element horizontal section of FIG. 4 are obtained.

According to the present embodiment, it is possible to form a resonator surface perpendicular to the substrate surface having the DBR structure high reflection film made of a crystalline layer, without the need to form the resonator end surface by cleavage.
With a high reflectance of 0% or more, a significantly low threshold operation was achieved, and the threshold current could be reduced from 1/10 to 1/20 as compared with Example 1.

Embodiment 4 Another embodiment of the present invention will be described. Elements were prepared in the same manner as in Examples 1 to 3, but instead of the sapphire substrate, n-type silicon carbide (α-S
iC) A device is provided using a substrate.

According to this embodiment, since the nitride TiN _x (0 <x ≦ 1) layer 2 is in contact with the large-area n-type SiC substrate, the n-type Ga
Contact resistance between N crystal layer and the n-side electrode was reduced to 1~3 × 10- ⁶ Ωcm ² range. Therefore, it was possible to suppress the element resistance and the operating voltage during laser oscillation to be smaller than those of the elements of Examples 1 to 3.

Embodiment 5 Another embodiment of the present invention will be described with reference to FIGS. 5 (a) and 5 (b). In this device, in order to fabricate a vertical cavity surface emitting structure, first, an AND GaN buffer layer 4, an AND GaN optical waveguide layer 12, an AND strain compensation GaInN / AlGaN DBR structure high reflection film 11, n. The GaN optical waveguide layer 13 is crystal-grown in advance. Next, after forming a regular hexagonal insulating film mask 3 as shown in FIG. 5 (b), a nitride TiN _x (0 <x ≦ 1) layer 2 is provided, and selective growth is performed in the same manner as in Example 3. To fabricate the device, and then
The device vertical section is obtained.

According to this embodiment, a surface-emitting type device structure having vertical resonator surfaces of DBR structure and a regular hexagonal columnar waveguide structure on the upper and lower surfaces can be manufactured. In this device structure, a nitride TiN _x (0 <x ≦ 1) layer 2 is formed on a large-area n-type GaN crystal layer.
Are in contact with each other, and the contact resistance with the n-type GaN crystal layer is 1 to 3 × 1
It could be reduced to 0- ⁶ Ωcm ² range. Therefore, it was possible to suppress the element resistance and the operating voltage during laser oscillation to be smaller than in the case where the nitride TiN _x was not provided.

Embodiment 6 Another embodiment of the present invention will be described with reference to FIGS. 6 (a) and 6 (b). An element is manufactured in the same manner as in Example 5, but an insulating film mask 3 containing a dummy pattern as shown in FIG. 6B is formed. After that, an element was manufactured in the same manner as in Example 5, and FIG.
A device vertical section shown in (a) is obtained.

According to the present embodiment, the crystallinity and shape controllability in the waveguide of the vertical resonator structure can be significantly improved as compared with the fifth embodiment by the effect of the dummy pattern, and the low threshold operation is achieved. did. The threshold current of this element could be reduced from 1/2 to 1/3 of that in Example 5.

[0024]

According to the present invention, by using the nitride TiN _x (0 <x ≦ 1) layer of Ti, which is a high melting point material, in the Nitride material which has been difficult to form a waveguide or a resonator until now. ,
A waveguide resonance structure suitable for a semiconductor laser could be produced by a single crystal growth. The nitride TiN _x (0 <x ≦ 1) layer is
Not only is it sufficiently durable for high-temperature crystal growth at 1000 ° C. or higher, but it also has the effect of improving the ohmic properties of the electrode and reducing the contact resistance with the crystal layer. The contact resistance at the n-side electrode is
It was possible to reduce to a 1~5 × 10- ⁶ Ωcm ^2. As a result, it was possible to reduce the resistance of the device and reduce the operating voltage during laser oscillation. Further, in this element structure, it is possible to manufacture a BH waveguide structure in which the basic lateral mode is stably guided and propagated due to the difference in the actual refractive index and a low threshold operation is possible. The threshold current could be reduced from 2/3 to 1/2 by introducing a dummy pattern on both outer sides of the stripe structure. In addition, the DBR on the resonator surface
By providing the structure, a threshold value much lower than before was achieved, and the threshold current could be reduced from 1/10 to 1/20. The present invention was also applied to a vertical cavity surface emitting structure to obtain a laser oscillation operating at a low resistance and a low operating voltage. In the embodiment of the present invention, the laser operation made of the AlGaInN material can be confirmed at room temperature, and the oscillation wavelength at room temperature is 410 to 430n.
The range was m and the wavelength range was blue-violet.

In the present invention, Wurtzite having a (0001) C plane is used.
Made on a sapphire or silicon carbide single crystal substrate with a structure
The GaInN semiconductor laser device was explained, but it is a GaAs, InP, InAs, GaP, GaSb of Zinc Blende structure having a (111) plane, or applied to an AlGaInN semiconductor laser device manufactured on a Si substrate. It goes without saying that you can do it.

[0026]

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an element structure showing one embodiment of the present invention (a)
And top view of insulating film mask shape (b).

FIG. 2 is a vertical sectional view of an element structure showing another embodiment of the present invention (a)
And top view of insulating film mask shape (b).

FIG. 3 is a vertical sectional view of an element structure showing another embodiment of the present invention (a)
And top view of insulating film mask shape (b).

FIG. 4 is a cross-sectional view of a device structure according to another embodiment of the present invention.

FIG. 5 is a vertical sectional view of an element structure showing another embodiment of the present invention (a)
And top view of insulating film mask shape (b).

FIG. 6 is a vertical sectional view of an element structure showing another embodiment of the present invention (a)
And top view of insulating film mask shape (b).

[Explanation of symbols]

1. (0001) C-plane α-Al ₂ O ₃ single crystal substrate, 2. TiN _x (0 <x ≦ 1)
Layers, 3. Insulating film SiO ₂ mask, 4. GaN buffer layer, 5.
n-type GaN optical waveguide layer, 6. GaInN / GaN / AlGaN multiple quantum well structure active layer, 7. p-type GaN optical waveguide layer, 8. Insulating film, 9. p
Side electrode Ni / Au, 10. n-side electrode Ti / Au, 11. High-reflectivity film with undoped strain-compensated GaInN / AlGaN DBR structure, 12. AND-GaN optical waveguide layer, 13. n-type GaN optical waveguide layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Akamatsu 1-280, Higashi Koikekubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (26)

[Claims] 1. A light emitting device provided on a single crystal substrate,
When manufacturing an optical waveguide structure, Ti or Ti nitride is provided in advance, and a crystal layer is provided so as to partially contact it, and an optical waveguide layer with a large forbidden band and a light emission activity with a small forbidden band A semiconductor laser device comprising an optical waveguide structure composed of layers. 2. The semiconductor laser device according to claim 1, wherein Ti or a nitride of Ti is previously provided on the single crystal substrate, and a crystal layer is provided so as to partially contact with the Ti or Ti nitride. A semiconductor laser device characterized in that the optical waveguide structure is formed by a single crystal growth. 3. The semiconductor laser device according to claim 1, wherein Ti or a Ti nitride is provided in advance so as to be in contact with the crystal layer, and finally Ti nitride TiN _x (0 <x ≦ 1) A semiconductor laser device characterized by being formed on the interface. 4. The semiconductor laser device according to claim 1, wherein the Ti nitride TiN _x (0 <x ≦ 1) is formed by reacting Ti with nitrogen. A semiconductor laser device characterized by: 5. The semiconductor laser device according to claim 4, wherein a Ti nitride TiN _x (0 <x ≦ 1) is formed by reacting Ti with nitrogen by heat treatment. A semiconductor laser device characterized by: 6. The semiconductor laser device according to claim 4, wherein electron cyclotron resonance (ECR) is used.
The semiconductor laser device is characterized in that it is provided in the form of a Ti nitride TiN _x (0 <x ≦ 1) in advance by reacting a metal Ti compound with nitrogen by means of resonance. 7. The semiconductor laser device according to claim 4, wherein Ti is reacted with nitrogen by a thermal reaction using an organic nitrogen metal Ti compound, and a Ti nitride TiN _x (0 <x ≦ 1) is previously obtained. A semiconductor laser device characterized by being provided in the form of. 8. The semiconductor laser device according to claim 1, wherein the optical waveguide layer and the light emitting active layer are III-
A V nitride semiconductor material _{Al x Ga y In 1-xy} N (0 ≦ x <1, 0
≤y <1) A semiconductor laser device characterized by being composed of a crystal layer. 9. A semiconductor laser device according to claim 8, wherein a III-V group nitride semiconductor material is provided on the single crystal substrate.
_{Al x Ga y In 1-xy} N (0 ≦ x <1, 0 ≦ y <1) may be provided a crystalline layer,
A semiconductor characterized in that a TiN _x (0 <x ≦ 1) nitride is obtained by first vapor-depositing metal Ti on it, and then reacting the underlying nitride semiconductor crystal layer with the metal Ti. Laser element. 10. The semiconductor laser device according to claim 1, wherein the surface of the single crystal substrate is subjected to a nitriding treatment in advance, and then a III-V group nitride semiconductor material is used. wherein there _{Al x Ga y in 1-xy} N or provided (0 ≦ x <1, 0 ≦ y <1) crystal layer, or is provided with a nitride _{TiN x (0 <x ≦ 1} ) Semiconductor laser device. 11. The semiconductor laser device according to claim 1, wherein metal Ti is provided in contact with Ti nitride TiN _x (0 <x ≦ 1). 2. A semiconductor laser device, wherein a laminated structure of Au and Au or a laminated structure of Ti and Al is formed as an electrode of an n-type crystal layer. 12. The semiconductor laser device according to claim 11, wherein a Ti nitride TiN _x (0 <x ≦ 1) and metallic Ti and a laminated structure of Ti and Au, or a laminated structure of Ti and Al is used. And a p-side electrode having a laminated structure of Cr and Au or a laminated structure of Ni and Au is provided so as to be in contact with the p-type crystal layer. -The device. 13. A semiconductor laser device according to claim 1, wherein the crystal layer constituting the optical waveguide structure is provided by using an insulating film mask and a selective growth technique. Laser element. 14. The semiconductor laser device according to claim 1 or 2, wherein the single crystal substrate is a semiconductor or ceramic substrate, and the conductivity type is semi-insulating, or p-type or n-type. And preferably a substrate exhibiting n-type conductivity. 15. The semiconductor laser device according to claim 14, wherein when the single crystal substrate is a semiconductor substrate, it has a hexagonal Wurtzite structure and a substrate plane orientation having a (0001) C plane. Alternatively, it is a substrate having a Zinc Blende structure and a substrate surface orientation of (111) plane, and when it is a ceramic single crystal substrate, it is a hexagonal Wurtzite structure and the substrate surface orientation is (0001) C. A semiconductor laser device having a surface and the optical waveguide structure provided on the single crystal substrate. 16. The semiconductor laser device according to claim 15, wherein when the optical waveguide structure is provided on a substrate having a hexagonal Wurtzite structure having a (0001) C plane, the direction of forming the waveguide is changed. A semiconductor laser device characterized by being set in a direction parallel to or perpendicular to the (11-20) A plane of the substrate. 17. The semiconductor laser device according to claim 15, wherein the single crystal substrate is α-Al ₂ O ₃ or α-SiC.
A semiconductor laser device characterized by being a substrate. 18. The semiconductor laser device according to claim 1, wherein the optical waveguide has a stripe structure having a rectangular cross-sectional shape, and the upper surface of the waveguide parallel to the substrate surface is It is a flat surface, the side surface of the waveguide is perpendicular to the substrate surface and is a smooth surface, and the light emitting layer having a small forbidden band width is embedded in the optical waveguide layer having a large forbidden band width inside the optical waveguide structure. And has a buried shape (BH; Buried Heterostructure) stripe structure that stably guides the basic lateral mode by providing a real refractive index difference in the lateral direction of the active layer. A characteristic semiconductor laser device. 19. A semiconductor laser device according to claim 18, wherein a rectangular BH stripe structure and a resonator end face perpendicular to the substrate surface are formed by using an insulating film mask and a selective growth technique. Bragg distributed reflection (DBR) on the end face
A semiconductor laser device characterized by being provided with a highly reflective film having a d Bragg Reflector structure. 20. The semiconductor laser device according to claim 19, wherein the BH stripe structure, the cavity end face, and the DBR.
A semiconductor laser device characterized in that a structurally highly reflective film is provided by one continuous crystal growth. 21. The semiconductor laser device according to claim 19 or 20, wherein at least two kinds of crystal layers having different refractive indexes are periodically repeated to use a crystal layer having a refractive index of n ₁ and n ₂ . At this time, the DBR structure high reflection film is formed by setting the oscillation wavelength of the laser to λ and setting the film thicknesses of the crystal layers to λ / 4n ₁ and λ / 4n ₂ , respectively. Laser element. 22. The semiconductor laser device according to claim 21, wherein at least two types of crystal layers having different refractive indexes and different lattice constants are periodically repeated, and the lattice strains are opposite in at least two types of crystal layers. A semiconductor laser device having the DBR structure high reflection film having a sign of 1 and a strain amount compensated in the entire film thickness. 23. The semiconductor laser device according to claim 18, wherein a dummy pattern is provided in regions corresponding to both outer sides of the waveguide, and an insulating film for selective growth of an optical waveguide structure including the dummy pattern is provided. A semiconductor laser device, wherein the optical waveguide structure is provided by forming a mask. 24. The semiconductor laser device according to claim 19, wherein the stripe structure formed on the dummy pattern provided on both outer sides of the waveguide is covered with a mask.
By so doing, no current is injected, and it is set so that current can be injected only into the inner waveguide structure. 25. The semiconductor laser device according to claim 1, wherein the light emitting active layer has a single or multiple quantum well structure composed of quantum well layers. Laser element. 26. The semiconductor laser device according to claim 25, wherein the light emitting active layer has a single or multiple strained quantum well structure constituted by a strained quantum well layer having lattice strain introduced therein. Semiconductor laser device.