KR20060089479A - Semiconductor laser diode and method for fabricating the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser diode and a method of manufacturing the same, wherein an electrode can be formed in a top-down manner by removing a sapphire substrate, and a ridge structure is formed in an N-semiconductor layer having a low bulk resistance. By lowering the resistance, power consumption and heat generation can be reduced, thereby improving the light-current-voltage (LIV) characteristics and reducing the degradation of the P-side ohmic electrode system, thereby increasing the life of the device.

Laser, diode, sapphire, substrate, breakaway, resistance

Description

Semiconductor laser diode and method for manufacturing the same {Semiconductor laser diode and method for fabricating the same}             

1 is a schematic cross-sectional view of a typical nitride semiconductor laser diode

2 is a schematic cross-sectional view of a nitride semiconductor laser diode according to the prior art.

3 is a schematic partial cross-sectional view of a nitride semiconductor laser diode having a general ridge structure;

4A to 4J are cross-sectional views illustrating a manufacturing process of a semiconductor laser diode according to the present invention.

5 is a cross-sectional view of a stacked structure of a semiconductor laser diode in accordance with the present invention.

<Description of the symbols for the main parts of the drawings>

100: sapphire substrate 110: buffer layer

111: N-semiconductor layer 112: N-clad layer

113: N-wave guide layer 114: multiple quantum well layer

115: electron overflow prevention layer 116: P-wave guide layer

117: P-clad layer 118: P- cap layer

120 dielectric film 130 N-electrode

150: ridge structure

200: stacked structure of the semiconductor laser diode

210: P-omic electrode 220,310: metal layer

300: fixing substrate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser diode and a method of manufacturing the same, and more particularly, to remove an sapphire substrate to form an electrode in a top-down manner, and to ridge the N-semiconductor layer with low bulk resistance. The structure can be lowered to reduce power consumption and heat generation, thereby improving the light-current-voltage (LIV) characteristics and reducing the degradation of the P-side ohmic electrode system, thereby increasing the life of the device. A semiconductor laser diode and a method of manufacturing the same.

In general, nitride semiconductor laser diodes have been developed and marketed to be applied to large-capacity data storage devices and color printers, and various new applications using them have recently been attempted.

For applications in large capacity data storage devices and color printers, nitride semiconductor laser diodes have an impact on device characteristics and reliability improvements related to device lifetime in addition to low threshold current (Ith) and high external quantum efficiency. This should facilitate heat dissipation.

Currently, all nitride semiconductor laser diodes are mostly used by Fendi using the Lateral Growth method on top of the sapphire substrate in order to reduce dislocations generated between the sapphire (Al ₂ O ₃ ) substrate and the nitride epi layer. It is manufactured using the Peneo or LEO method.

FIG. 1 is a schematic cross-sectional view of a general nitride semiconductor laser diode, in which a stacked structure 20 of a nitride semiconductor laser diode is grown on a sapphire substrate 10.

The stacked structure 20 of the nitride semiconductor laser diode is composed of an undoped GaN layer 11, an N-GaN layer 12, an N-clad layer 13, an N-wave guide layer 14, and a multi-quantum well layer. (15), the electron overflow prevention layer 16, the P-wave guide layer 17, the P-clad layer 18, and the P-cap layer 19 are laminated in this order.

Here, electrons and holes injected from the N-GaN layer 12 and the P-cap layer 19 are recombined with the active layer 15 to generate laser light, which is emitted to the outside of the device.

The nitride semiconductor laser diode manufacturing method has the following problems.

First, current device manufacturing substrates have difficulty in supplying high-quality and high-quality substrates of gallium nitride substrates, and most of them use gallium nitride substrates manufactured from sapphire substrates using Pendeo or LEO methods. Gallium nitride fabricated from a sapphire substrate is warped due to lattice mismatch between gallium nitride and sapphire, making it difficult to form a mirror surface of a good device.

Secondly, Mg is used as a dopant when growing a P-type semiconductor layer, which is attached to a chamber for fabricating a device and adversely affects the growth of an N-type semiconductor layer. (Memory Effect), a P-type semiconductor layer is usually grown after growing an N-type semiconductor layer, a wave guide layer, a multiple quantum well layer and the like.

FIG. 2 is a schematic cross-sectional view of a nitride semiconductor laser diode according to the prior art, and mesa-etch the above-described nitride semiconductor stacked structure 20, and the N-electrode 31 on the N-GaN layer 12 exposed by mesa etching. The P electrode 32 is formed on the P-cap layer 19.

As a result, in the nitride semiconductor laser diode according to the prior art, an N electrode and a P electrode are formed above the sapphire substrate 10.

FIG. 3 is a schematic partial cross-sectional view of a nitride semiconductor laser diode having a general ridge structure, wherein an electron overflow prevention layer 16, a P-wave guide layer 17, and a P-clad layer 18 are disposed on an active layer 15. And the P-cap layer 19 are sequentially formed. A portion of the P-clad layer 18 is selectively etched in the P-cap layer 19 to form a Ridg structure in the central region.

A dielectric film 25 is formed on both sides of the ridge structure.

In addition, a P electrode 32 is formed on the P-cap layer 19 and the dielectric layer 25 of the ridge structure.

Such a nitride semiconductor laser diode has a problem that resistance increases because current flows in a ridge structure with a narrow area.

As described above, in the conventional nitride semiconductor laser diode, a sapphire substrate remains to form an electrode in the upper direction of the device, that is, the top-top method, and the ridge structure is formed on the P-semiconductor layer. There is no choice but to form a resistance.

On the other hand, holes have a lower mobility than electrons.

And, the doping of the carrier to form the P-semiconductor layer is more difficult than the doping of the carrier to form the N-semiconductor layer, so that the carrier concentration doped to the P-semiconductor layer is about 1 × 10 ¹⁸ . Since the carrier concentration doped to about 5 X 10 ¹⁸ ~ 1 X 10 ¹⁹ , the carrier concentration of the P-semiconductor layer is significantly lower than the carrier concentration of the N- semiconductor layer.

Therefore, since the P-semiconductor layer has a significantly lower carrier mobility and concentration than the N-semiconductor layer, the P-semiconductor layer has a higher bulk resistance than the N-semiconductor layer.

As a result, since the sapphire substrate remains in the conventional semiconductor laser diode, a ridge structure is formed on the P-semiconductor layer having a high bulk resistance, resulting in a problem of excessive resistance and excessive power consumption.

In addition, the resistance is accompanied by heat generation, which has a detrimental effect on the lifetime, which is an important item of device reliability due to the deterioration of the L-I-V characteristics, the P-side ohmic electrode system and the deterioration of the device characteristics.

In order to solve the above problems, the present invention can remove the sapphire substrate to form an electrode in a top-down manner, and form a ridge structure in the N-semiconductor layer having a low bulk resistance to form a resistor. The semiconductor laser diode and its which can reduce the power consumption and heat generation to improve the light-current-voltage (LIV) characteristics and reduce the degradation of the P-side ohmic electrode system, thereby increasing the life of the device It is an object to provide a manufacturing method.

A preferred aspect for achieving the above object of the present invention is a metal layer, a stacked structure of a P-ohmic electrode and a semiconductor laser diode is sequentially stacked on the fixing substrate;

The laminated structure of the semiconductor laser diode,

A P-cap layer, a P-clad layer, a P-wave guide layer, an electron overflow prevention layer, a multiple quantum well layer, an N-wave guide layer, an N-clad layer and an N-semiconductor layer are sequentially stacked;

Except for the central region, a ridge structure is formed by etching from the N-semiconductor layer to a portion of the N-clad layer or from the N-semiconductor layer to a portion of the N-wave guide layer;

Dielectric films are formed on etched surfaces located on both sides of the ridge structure;

A semiconductor laser diode is provided in which an N electrode is formed on the dielectric film and the ridge structure.

Another preferred aspect for achieving the above object of the present invention is a buffer layer, an N-semiconductor layer, an N-clad layer, an N-wave guide layer, a multi-quantum well layer, an electron overflow prevention layer, Forming a stack structure of a semiconductor laser diode in which a P-wave guide layer, a P-clad layer, and a P-cap layer are sequentially stacked;

Forming a P-omic electrode and a lower metal layer for bonding on the stacked structure of the semiconductor laser diode;

Preparing a fixing substrate having an upper metal layer for bonding formed thereon, and bonding the upper metal layer for bonding of the fixing substrate by thermal compression to the lower metal layer for bonding;

Irradiating a laser light from a bottom surface of the sapphire substrate to separate the sapphire substrate from the buffer layer of the stacked structure of the semiconductor laser diode;

Removing the buffer layer of the stacked structure of the semiconductor laser diode;

Etching away from the N-semiconductor layer or the N-semiconductor layer to a portion of the N-wave guide layer of the stacked structure of the semiconductor laser diode except for a central region to form a ridge structure;

Forming a dielectric film on etched surfaces located on both sides of the ridge structure;

There is provided a method of manufacturing a semiconductor laser diode comprising forming an N electrode on the dielectric film and the ridge structure.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

4A to 4J are cross-sectional views illustrating a manufacturing process of a semiconductor laser diode according to the present invention. First, as shown in FIG. 4A, a stacked structure 200 of a semiconductor laser diode is formed on an sapphire substrate 100. do.

As shown in FIG. 5, the stacked structure 200 of the semiconductor laser diode may include a buffer layer 110, an N-semiconductor layer 111, an N-clad layer 112, an N-wave guide layer 113, and multiple layers. The quantum well layer 114, the electron overflow prevention layer 115, the P-wave guide layer 116, the P-clad layer 117, and the P-cap layer 118 are sequentially stacked.

In this case, the semiconductor layer is preferably a GaN layer, and the buffer layer is preferably a undoped GaN layer.

Thereafter, a P-omic electrode 210 is formed on the stacked structure 200 of the semiconductor laser diode, and a lower metal layer 220 for bonding is formed on the P-omic electrode 210. )

Next, a fixing substrate 300 having a bonding upper metal layer 310 formed thereon is prepared (FIG. 4C).

Subsequently, the bonding upper metal layer 310 of the fixing substrate 300 is thermocompression-bonded to the bonding lower metal layer 220 for bonding (FIG. 4D).

At this time, the upper and lower metal layers 310 and 220 for bonding may be formed of AuSn using an e-beam evaporator or a thermal evaporator, Cu or Pd using a plating method. / In laminated film and the like can be used.

Subsequently, the bottom surface of the sapphire substrate 100 is irradiated with laser light to separate the sapphire substrate 100 from the buffer layer 110 of the stacked structure 200 of the semiconductor laser diode (FIG. 4E).

At this time, the laser beam penetrates the sapphire substrate 100, reaches the interface between the sapphire substrate 100 and the buffer layer 110, and the buffer layer 110 is thermally decomposed and released, thereby causing laser lift-off. It is a process.

For reference, in order to facilitate the description, 4f to 4j described later are enlarged vertically than FIGS. 4A to 4E.

Next, when the lift-off process is completed, it is turned over, as shown in FIG. 4F, and the buffer layer 110 of the stacked structure 200 of the semiconductor laser diode is removed as shown in FIG. 4G.

Thereafter, except for the central region, a portion of the N-clad layer 112 in the N-semiconductor layer 111 of the stacked structure 200 of the semiconductor laser diode or an N-wave guide in the N-semiconductor layer 111. A portion of layer 113 is etched to form ridge structure 150 (FIG. 4H).

Subsequently, the dielectric film 120 is formed on the etched surfaces located on both sides of the ridge structure (FIG. 4I).

Finally, an N electrode 130 is formed on the dielectric film 120 and the ridge structure.

As such, the manufactured semiconductor laser diode is formed by sequentially stacking a metal layer, a P-omic electrode 210, and a stacked structure 200 of a semiconductor laser diode on the fixing substrate 300; The stacked structure of the semiconductor laser diode may include a P-cap layer 118, a P-clad layer 117, a P-wave guide layer 116, an electron overflow prevention layer 115, a multi-quantum well layer 114, and an N−. The wave guide layer 113, the N-clad layer 112 and the N-semiconductor layer 111 are sequentially stacked; Except for the central region, the ridge structure 150 may be etched from the N-semiconductor layer 111 to a portion of the N-clad layer 112 or from the N-semiconductor layer 111 to a portion of the N-wave guide layer 113. ) Is formed; Dielectric films 120 are formed on etched surfaces located on both sides of the ridge structure; The N electrode 130 is formed on the dielectric film 120 and the ridge structure.

Here, the metal layer positioned on the fixing substrate 300 refers to the upper and lower metal layers for bonding as described above.

Therefore, the present invention can form an electrode in a top-down manner by removing the sapphire substrate, and forms a ridge structure in the N-semiconductor layer having a low bulk resistance to lower the resistance to reduce power consumption and heat generation. By reducing, the LIV characteristics can be improved, and the degradation of the P-side ohmic electrode system can be reduced, thereby increasing the life of the device.

As described above, the present invention can form an electrode in a top-down manner by removing the sapphire substrate, and by forming a ridge structure in the N-semiconductor layer having a low bulk resistance to lower the power consumption And it is possible to reduce the heat generation, to improve the light-current-voltage (LIV) characteristics, and to reduce the degradation of the P-side ohmic electrode system, there is an excellent effect that can increase the life of the device.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (5)

A stacked structure of a metal layer, a P-omic electrode, and a semiconductor laser diode is sequentially stacked on the fixing substrate; The laminated structure of the semiconductor laser diode, A P-cap layer, a P-clad layer, a P-wave guide layer, an electron overflow prevention layer, a multiple quantum well layer, an N-wave guide layer, an N-clad layer and an N-semiconductor layer are sequentially stacked; Except for the central region, a ridge structure is formed by etching from the N-semiconductor layer to a portion of the N-clad layer or from the N-semiconductor layer to a portion of the N-wave guide layer; Dielectric films are formed on etched surfaces located on both sides of the ridge structure; And an N electrode formed on the dielectric film and the ridge structure. The method of claim 1, And said semiconductor layer is a GaN layer. A buffer layer, an N-semiconductor layer, an N-clad layer, an N-wave guide layer, a multi-quantum well layer, an electron overflow prevention layer, a P-wave guide layer, a P-clad layer, and a P-cap layer are sequentially stacked on the sapphire substrate. Forming a stacked structure of the semiconductor laser diode; Forming a P-omic electrode and a lower metal layer for bonding on the stacked structure of the semiconductor laser diode; Preparing a fixing substrate having an upper metal layer for bonding formed thereon, and bonding the upper metal layer for bonding of the fixing substrate by thermal compression to the lower metal layer for bonding; Irradiating a laser light from a bottom surface of the sapphire substrate to separate the sapphire substrate from the buffer layer of the stacked structure of the semiconductor laser diode; Removing the buffer layer of the stacked structure of the semiconductor laser diode; Etching away from the N-semiconductor layer or the N-semiconductor layer to a portion of the N-wave guide layer of the stacked structure of the semiconductor laser diode except for a central region to form a ridge structure; Forming a dielectric film on etched surfaces located on both sides of the ridge structure; And forming an N electrode over the dielectric film and the ridge structure. The method of claim 3, wherein The semiconductor layer is a GaN layer, The buffer layer is a method of manufacturing a semiconductor laser diode, characterized in that the undoped GaN layer. The method of claim 3, wherein The upper and lower metal layers for bonding, A method of manufacturing a semiconductor laser diode, which is any one of AuSn, Cu, and a Pd / In laminated film.

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