JP2001135885A - Semiconductor laser device and its assembling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve the difficulty of the alignment for bonding the active layer of a GaN-based semiconductor laser element to the side of its heat sink, although a light intercepting electrode for reducing its amplified spontaneous emission light is required to be formed on its transparent insulating substrate. SOLUTION: An opening is formed at a light intercepting electrode, through which p-n electrodes in a semiconductor laser device are aligned to corresponding electrodes in the heat sink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical disk device,
The present invention relates to a semiconductor laser device used for an optical information processing device such as a laser printer, an optical communication system, and a measurement / analysis device using a laser.

[0002]

2. Description of the Related Art A conductive GaAs substrate is used for a GaAlAs-based semiconductor laser having a wavelength of 0.78 μm or an InGaAlP-based semiconductor laser having a wavelength of 0.65 μm. GaAs
Since s has an energy gap at a wavelength of 0.87 μm, light having a wavelength shorter than 0.87 μm is GaAs.
s absorbs. Therefore, GaAl of the wavelength of 0.78 μm band
As-based semiconductor laser or InGaAs with a wavelength of 0.65 μm
In an IP semiconductor laser, GaAs on the substrate absorbs laser light. The semiconductor laser generates spontaneous emission light before the current reaches the oscillation threshold and laser oscillation occurs.
Spontaneous emission light is incoherent light having a wide spectrum width unlike laser light, and it is not desirable to mix it with laser light. Normally, in a semiconductor laser, the spontaneous emission light saturates at a value almost equal to the threshold after the current reaches the oscillation threshold and laser oscillation occurs. The proportion of light increases, and the coherence of the laser light deteriorates, causing noise.

When GaAs is used for the substrate, the wavelength is 0.78 μm.
m band GaAlAs based semiconductor laser or wavelength 0.65μm
In the InGaAlP-based semiconductor laser in the band, a considerable proportion of the spontaneous emission light emitted from the active layer in various directions is absorbed by the GaAs substrate, so that the spontaneous emission light mixed with the laser light falls within an allowable range.

A semiconductor laser using GaAs for a substrate is:
A pn junction diode is formed on a substrate by crystal growth, and one of the diodes (n-side or p-side) passes a current through the substrate. That is, when an n-type GaAs substrate is used,
The n-type layer of the diode is formed closer to the substrate, and the p-type Ga
When an As substrate is used, the p-type layer of the diode is formed closer to the substrate.

In many cases, a diode having a large heat generation is mounted in contact with a heat sink. This is called junction down bonding.
In this case, the voltage applied to the semiconductor laser is applied between the ohmic electrode provided on the substrate and the electrode provided on the heat sink. When the heat sink is conductive, a method of applying a voltage to the semiconductor laser via the heat sink is available.

[0006]

In a GaN-based semiconductor laser that oscillates in a wavelength band of 0.4 μm, sapphire is often used for a substrate. Sapphire is a transparent electrical insulator, and is widely used because it is stable even at a high temperature exceeding 1000 ° C. at the time of crystal growth of GaN and has a lattice constant close to that of GaN. Since sapphire is an insulator, the p-n junction diode of GaN grown on sapphire has the p
The side and the n-side electrode must be formed on the same side of the sapphire substrate. In addition, since sapphire transmits laser light having a wavelength of 0.4 μm, spontaneous emission light generated in the active layer leaks outside through the substrate. Further, since sapphire has poor heat conduction, it is necessary to adhere the side of the active layer which is a heat source to the heat sink. Therefore, electrodes must be provided on the heat sink corresponding to the p-side electrode and the n-side electrode of the semiconductor laser. In this case, the p electrode and the n electrode must be electrically separated. The heat sink to which the semiconductor laser is attached is called a submount.

It is necessary to accurately align and bond the semiconductor laser to the electrodes on the submount by junction down. However, since the sapphire substrate is transparent, the p and n electrodes of the semiconductor laser are seen through from the substrate side. Positioning can be performed while looking at the p and n electrodes of the submount. On the other hand, to reduce spontaneous emission light leaking from the substrate, it is effective to attach a metal film or the like to the substrate. However, if a light-shielding film is attached to the substrate to prevent spontaneous emission light, the light-shielding film cannot be seen through for alignment.

[0008]

In order to solve the above-mentioned problem, in the semiconductor laser device of the present invention, an opening is provided in the light-shielding film of the sapphire substrate at a position corresponding to between the p and n electrodes of the heat sink. Through this opening p of the heat sink,
By seeing through between the n electrodes, it is possible to perform alignment during bonding.

By forming a groove between the p and n electrodes of the heat sink (submount), the position can be easily confirmed when viewed through the opening. Further, it is possible to prevent an electrical short circuit between the p and n electrodes due to the flow of solder. As the heat sink, diamond, SiC, or AlN, which is insulative and has good heat conductivity, is suitable. However, even if a conductive material such as Si is used, p, n electrically separated by forming an insulating film on the surface. Electrodes can be formed.

The light-shielding film provided on the substrate is preferably a metal film such as Au or Al. Further, the opening formed in the light-shielding film may extend over the entire cavity direction of the semiconductor laser, but it is preferable that the opening has a minimum length necessary for alignment in order to further reduce leaked spontaneous emission light. .

[0011]

FIG. 1 is a structural view of a semiconductor laser device according to the present invention. The semiconductor laser device is formed on one side of the transparent substrate 1, and the p-side electrode 2 and the n-side electrode 3 are on the same surface of the substrate 1. A light-shielding electrode 4 is formed on the side of the substrate 1 opposite to the p- and n-electrode surfaces, and prevents spontaneous emission light generated from the laser emitting portion 5 below the p-side electrode from leaking outside through the substrate. The substrate 1 is generally sapphire in a GaN-based semiconductor laser, but the present invention can be applied to other transparent substrates.

A metal film combining Ti and Au was used for the light-shielding electrode. Ti plays a role in increasing the adhesive strength with sapphire, and Au plays a role in reflecting and absorbing spontaneous emission light so as not to leak out. A combination of other metals may be used as long as the metal has a similar effect. In addition, a single film may be used, or a film other than a metal may be used as long as it serves the purpose of shielding light.

A heat sink (submount) 6 for bonding the semiconductor laser element has a p-side electrode 7 for bonding to the p-side electrode 2 of the semiconductor laser element and an n-side electrode 8 for bonding to the n-side electrode 3 of the semiconductor laser element. In addition, the solder 10 is formed on the bonding portion. A groove 9 is formed between the p and n electrodes 7 and 8 of the heat sink 6, and the position between the electrodes 7 and 8 is
Through which the solder flows and p, n
It serves to prevent the electrodes 7 and 8 from being short-circuited.

An opening is formed in the light-shielding electrode 4 of the substrate 1 at a position corresponding to between the p and n electrodes of the semiconductor laser device.
Since the substrate 1 is transparent, the space between the p and n electrodes 2 and 3 on the opposite side of the opening can be seen through the opening. Further, the space between the p and n electrodes 7 and 8 and the groove 9 on the heat sink 6 can be seen through the substrate.

The heat sink 6 is made of an electrically insulating SiC or A
1N or diamond is suitable, but it is also possible to use a material in which an oxide film is formed on Si and p and n electrodes 7 and 8 are electrically separated.

In order to assemble the present semiconductor laser device, the positioning is performed while checking the groove 9 on the heat sink 6 through the opening of the light-shielding electrode, and the p-side electrodes 2 and 7 and the n-side electrodes 3 and 8 are aligned and fixed. Then, heating is performed to a temperature at which the solder melts.

In the embodiment shown in FIG. 1, the opening formed in the light-shielding electrode is formed over the entire cavity length of the semiconductor laser. However, as shown in FIG. 2, it may be partially formed. I can do it. In this case, the spontaneous emission light leaking from the opening is desirably reduced.

In order to ensure the alignment at the time of assembling, it is preferable to emit light by energizing before melting and bonding the solder. At this time, since spontaneous emission light leaks from the opening, it can be confirmed that light is emitted.

[0019]

According to the semiconductor laser device of the present invention, it is possible to reduce the spontaneous emission of a semiconductor laser device formed on a transparent insulating substrate. Further, mounting in which the active layer is close to the heat sink becomes possible, and the influence of a substrate having poor heat conduction can be eliminated.

[Brief description of the drawings]

FIG. 1 is a structural view of a semiconductor laser device of the present invention.

FIG. 2 is a view showing an opening of a light-shielding electrode.

[Explanation of symbols]

 Reference Signs List 1 electrically insulating transparent substrate 2 p-side electrode of semiconductor laser device 3 n-side electrode of semiconductor laser device 4 light-shielding electrode 5 light-emitting portion of semiconductor laser device 6 heat sink (submount) 7 p-side electrode of heat sink 8 n-side electrode of heat sink 9 groove 10 solder

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Isao Kidoguchi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (reference) 5F036 AA01 BB08 BC06 BD11 BD14 BD16 5F073 BA01 BA06 BA07 CA02 CB05 CB23 FA15 FA23

Claims (7)

[Claims] 1. A semiconductor laser device formed on a translucent and electrically insulating substrate, having a p-side electrode and an n-side electrode on the same surface opposite to the substrate, wherein the p and n electrodes are respectively The substrate is provided with a film for blocking laser light, which is adhered to an electrode formed on a heat sink, and has an opening in a light-shielding film of the substrate at a position corresponding to between the p and n electrodes of the heat sink. A semiconductor laser device. 2. The semiconductor laser device according to claim 1, wherein a groove is formed between the p electrode and the n electrode of the heat sink. 3. The semiconductor laser device according to claim 1, wherein the heat sink is formed by attaching an insulating film to an electrically insulating material or a conductive material. 4. The semiconductor laser device according to claim 1, wherein the film formed on the substrate for blocking laser light is made of metal. 5. The semiconductor laser device according to claim 1, wherein the opening of the light-shielding film of the substrate is formed over the entire cavity direction of the semiconductor laser or is partially formed. 6. A semiconductor laser device formed on a translucent and electrically insulating substrate, having a p-side electrode and an n-side electrode on the same surface opposite to the substrate, wherein the p and n electrodes are respectively The substrate is provided with a film for blocking laser light, which is adhered to an electrode formed on a heat sink, and has an opening in a light-shielding film of the substrate at a position corresponding to between the p and n electrodes of the heat sink. And positioning the heat sink and the semiconductor laser device by confirming a position corresponding to between the p and n electrodes of the heat sink through the opening from the substrate side. 7. A semiconductor laser device formed on a translucent and electrically insulating substrate, having a p-side electrode and an n-side electrode on the same surface opposite to the substrate, wherein the p and n electrodes are respectively The substrate is provided with a film for blocking laser light, which is adhered to an electrode formed on a heat sink, and has an opening in a light-shielding film of the substrate at a position corresponding to between the p and n electrodes of the heat sink. A method of assembling a semiconductor laser device, wherein the semiconductor laser device is energized while the semiconductor laser is in contact with the heat sink to emit light, and the light is viewed through the opening to align the heat sink with the semiconductor laser device.