KR100386243B1 - Blue semiconductor laser and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a blue semiconductor laser and a method for manufacturing the same. In the conventional blue semiconductor and the method for manufacturing the same, the width of the p-GaN layer must be limited, and thus the operating voltage of the device increases due to an increase in contact resistance with the electrode. In addition, heat dissipation is made through the narrow p-GaN layer, there is a problem that heat dissipation is not easy. In view of the above problems, the present invention includes a buffer layer 2 and an n-GaN layer 3 sequentially stacked on the upper surface of the substrate 1; An InGaN layer (4), an n-AlGaN layer (5), and an n-GaN layer (6) sequentially stacked on a portion of the n-GaN layer (3); An N-type electrode 17 positioned at an upper portion of the n-GaN layer 3; The n-GaN layer on the entire side surface of the InGaN layer 4, the n-AlGaN layer 5, and the n-GaN layer 6 and its periphery at a position spaced a predetermined distance from the N-type electrode 17 ( A p-GaN layer 8 located above 3); A p-AlGaN layer (9), a p-GaN layer (10), and an n-GaN layer (11) sequentially stacked on the upper surface of the p-GaN layer (8); The n-GaN layer 12, the multi-quantum well active layer (MQW), and the p-GaN layer sequentially stacked on the exposed n-GaN layer 6 and on the entire upper surface of the n-GaN layer 11 ( 13), electron blocking layer 14, p-AlGaN layer 15, p-GaN layer 16; An AlGaN layer having a large band gap and a small refractive index composed of a P-type electrode 18 positioned to have a predetermined area on an upper side of the n-GaN layer 6 and an upper portion of the p-GaN layer 16 at the periphery thereof. Increasing the confinement effect has the effect of having a relatively low start threshold current.

Description

Blue semiconductor laser and its manufacturing method {BLUE SEMICONDUCTOR LASER AND MANUFACTURING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue semiconductor laser and a method of manufacturing the same, and more particularly, to a blue semiconductor laser and a method of manufacturing the same, having a low heat resistance and an operating voltage of the device.

1A to 1C illustrate a process cross-sectional view of a conventional blue semiconductor laser, in which a buffer layer 2 is deposited on an upper portion of a substrate 1, and an n-GaN layer 3 and InGaN are formed on the upper surface thereof. Layer (4), n-AlGaN layer (5), GaN layer (6), active layer (7), p-GaN layer (8), p-AlGaN electron blocking layer (9), p-AlGaN layer (10), sequentially depositing the p-GaN layer 11 (FIG. 1A); P-GaN layer 11, p-AlGaN layer 10, p-AlGaN electron blocking layer 9, p-GaN layer 8, active layer 7, GaN layer deposited by dry etching process (6), a portion of the n-AlGaN layer 5 and the InGaN layer 4 are etched to expose a portion of the upper portion of the n-GaN layer 3, and then the p-GaN layer is subjected to dry etching again. Forming a pattern for remaining a portion of (11), and etching a portion of the upper portion of the p-AlGaN layer 10 below the etching region of the p-GaN layer 11 (FIG. 1B); A conductive film is deposited on the upper surface of the structure and patterned to form an N-type electrode 13 positioned on an upper portion of the exposed n-GaN layer 3, and then an insulating film 12 is formed on the upper surface of the structure. After the deposition, the insulating film is patterned to expose the upper portion of the p-GaN layer 11, and a pattern is formed to expose the entire surface of the n-GaN layer 3 and the N-type electrode 13 again. And forming a P-type electrode 14 in contact with the upper surface of the p-GaN layer 11 on the upper side of the insulating film 12 (Fig. 1C).

Hereinafter, a conventional blue semiconductor laser manufacturing method configured as described above will be described in more detail.

First, as shown in FIG. 1A, the buffer layer 2, the n-GaN layer 3, the InGaN layer 4, the n-AlGaN layer 5, the GaN layer 6, The active layer 7, the p-GaN layer 8, the p-AlGaN electron blocking layer 9, the p-AlGaN layer 10, and the p-GaN layer 11 are sequentially deposited.

In this case, the substrate 1 uses sapphire or GaN, and the InGaN layer 4 serves to prevent cracks, and the n-GaN layer 3 and the p-GaN layer 8 each act as a waveguide. Each layer deposited sequentially is deposited using MOCVD.

Then, as shown in FIG. 1B, a photoresist is applied to the upper surface of the structure, exposed and developed to form a pattern, and the deposited film is deposited by a dry etching process using the patterned photoresist as an etching mask. p-GaN layer 11, p-AlGaN layer 10, p-AlGaN electron blocking layer 9, p-GaN layer 8, active layer 7, GaN layer 6, n-AlGaN layer ( 5) A portion of the InGaN layer 4 is etched to expose a portion of the upper portion of the n-GaN layer 3 serving as the waveguide.

Then, the photoresist pattern is removed, the photoresist is applied again, and the photoresist is exposed and developed to expose the upper surface of the exposed n-GaN layer 3 and the width of the photoresist 2 to the upper portion of the p-GaN layer 11. The p-GaN layer 11 exposed by the etching process using the photoresist pattern as an etch mask is removed, and the upper portion of the lower p-AlGaN layer 10 is removed. do.

Next, as illustrated in FIG. 1C, a conductive layer containing N-type impurities is deposited on the upper surface of the structure, and patterned to form the N-type electrode 13 positioned on the center of the n-GaN layer 3. ).

Then, an insulating film 12 is deposited on the upper surface of the structure, and patterned through a photolithography process to expose the upper surface of the n-GaN layer 3 and the N-type electrode 13, and the width is 2 The upper part of the p-GaN layer 11 which is -3 micrometers is exposed.

The reason for limiting the width of the p-GaN layer 11 is because the difference in refractive index between the insulating film 12 and the p-GaN 11 is large, so that the width of the p-GaN layer 11 must be maintained to obtain a single mode of light during laser oscillation. do. However, if the width is narrowed as described above, the contact area with the P-type electrode 14 is relatively narrow, resulting in an increase in contact resistance.

As described above, when the contact resistance increases, the operating voltage of the blue semiconductor laser increases, and since the heat generated during the oscillation is only released through the p-GaN layer 11, it is difficult to emit heat. Have

Then, a P-type impurity doped conductive film is deposited on the upper surface of the structure and patterned to form a P-type electrode 14 located on the upper surface of the p-GaN layer 11 and the insulating film 12 around the periphery thereof. ).

In the conventional blue semiconductor laser manufactured as described above, since the p-type GaN layer has a low hole concentration, the contact resistance is relatively higher than that of other semiconductors.

As described above, the conventional blue semiconductor laser should limit the width of the p-GaN layer, and thus, the operating voltage of the device increases due to the increase in contact resistance with the electrode, and heat dissipation through the narrow p-GaN layer. By doing so, there was a problem that heat dissipation was not easy.

It is an object of the present invention to provide a blue semiconductor laser and a method for manufacturing the same, which reduce contact resistance between a p-GaN layer and an electrode and facilitate heat dissipation.

1A to 1C are cross-sectional views showing a manufacturing process of a conventional blue semiconductor laser.

2A to 2E are cross-sectional views of a manufacturing process of the blue semiconductor laser of the present invention.

* Description of the symbols for the main parts of the drawings *

1: Substrate 2: Buffer Layer

3,6,11,12: n-GaN layer 4: InGaN layer

5: n-AlGaN layer 7: insulating film

8,10,13,16: p-GaN layer 9,15: p-AlGaN layer

14: electron blocking layer 17: N-type electrode

18: P-type electrode

The purpose of the above is to improve the confinement characteristics of the electron and electric field so that the generated light proceeds only in the vertical direction, to increase the contact area of the electrode, and to block heat to block the structure to block the light to proceed only in the vertical direction It is achieved by not using, and when described in detail with reference to the accompanying drawings, the present invention as follows.

2A to 2E are schematic cross-sectional views of a process for manufacturing a blue semiconductor laser according to the present invention. As shown therein, a buffer layer 2 is deposited on an upper surface of a substrate 1 and an n-GaN layer 3 is formed on an upper surface thereof. Depositing sequentially an InGaN layer 4, an n-AlGaN layer 5, and an n-GaN layer 6 (FIG. 2A); An oxide film 7 is deposited on the entire upper surface of the n-GaN layer 6, and the oxide film 7 is patterned to leave an oxide film 7 pattern positioned on an upper portion of the n-GaN layer 6. Thereafter, the n-GaN layer 6 exposed by the etching process using the oxide film 7 pattern as an etching mask is etched, and the n-AlGaN layer 5 and the InGaN layer 4 under the etching region are etched. After removing, removing the upper portion of the n-GaN layer (3) (Fig. 2b); The p-GaN layer on the upper surface of the structure, the n-GaN layer (3) and the InGaN layer (4), n-AlGaN layer (5), n-GaN layer (6) side of the stacked surface (8) sequentially growing the p-AlGaN layer 9, the p-GaN layer 10, and the n-GaN layer 11 (FIG. 2C); The oxide film 7 pattern was removed, and the n-GaN layer 12, the multi-quantum well active layer (MQW), the p-GaN layer 13, the electron blocking layer 14, the p-AlGaN layer 15, and p Sequentially growing the GaN layer 16 (FIG. 2D); P-GaN layer 16 and p-AlGaN layer, which are stacked in a region spaced a predetermined distance from a region where the InGaN layer 4, n-AlGaN layer 5, and n-GaN layer 6 are stacked. 15), electron blocking layer 14, p-GaN layer 13, multi-quantum well active layer (MQW), n-GaN layer 12, n-GaN layer 11, p-GaN layer 10, After removing the p-AlGaN layer 9 and the p-GaN layer 8 to expose the upper portion of the n-GaN layer 3, the N-type electrode 17 is formed on an upper portion of the n-GaN layer 3. ) And forming a P-type electrode 18 on the p-GaN layer 16 (FIG. 2E).

Hereinafter, the blue semiconductor of the present invention configured as described above and a manufacturing method thereof will be described in more detail.

First, as shown in FIG. 2A, a sapphire or GaN substrate 1 is mounted in a growth apparatus, and a buffer layer 2, an n-GaN layer 3, and an InGaN layer 4 are formed on the upper surface of the substrate 1. , the n-AlGaN layer 5 and the n-GaN layer 6 are grown sequentially.

At this time, the n-GaN (6) layer is used as the waveguide layer.

Next, as illustrated in FIG. 2B, an oxide film 7 is deposited on the upper surface of the n-GaN layer 6, and the oxide film 7 is patterned to have a width of 3 μm through a photolithography process.

Next, the n-GaN layer 6 exposed by the etching process using the remaining oxide film 7 pattern as an etching mask is etched.

Subsequently, the n-AlGaN layer 5 exposed through the etching process and the InGaN layer 4 below are sequentially etched, and then a portion of the upper portion of the n-GaN layer 3 is removed to form a ridge ( RIDGE).

Next, as shown in FIG. 2C, the structure completed by the etching process is mounted on the growth apparatus again, and the upper surface of the n-GaN layer 3 and the stacked InGaN layer 4 and n-AlGaN are stacked. The p-GaN layer 8, the p-AlGaN layer 9, the p-GaN layer 10, and the n-GaN layer 11 are sequentially disposed on the etched side surfaces of the layer 5 and the n-GaN layer 6. To grow.

At this time, since no film is grown on the upper side of the oxide film 7, the upper surface of the pattern of the oxide film 7 is exposed.

Next, as shown in FIG. 2D, the pattern of the oxide film 7 having the upper surface exposed is selectively removed, so that the upper surface of the n-GaN layer 6 serving as the waveguide layer is replaced by the p-GaN layer. (8), the p-AlGaN layer 9, the p-GaN layer 10, and the n-GaN layer 11 are exposed.

Then, the structure is mounted on the deposition equipment again, and the n-GaN layer 12, the multi-quantum well active layer (MQW), p so that the step difference between the n-GaN (11) layer and the n-GaN layer (6) are revealed. -GaN layer 13, electron blocking layer 14, p-AlGaN layer 15, p-GaN layer 16 are sequentially grown.

Next, as shown in FIG. 2E, p-GaN stacked in a region spaced a predetermined distance from the region in which the InGaN layer 4, the n-AlGaN layer 5, and the n-GaN layer 6 are stacked. Layer 16, p-AlGaN layer 15, electron blocking layer 14, p-GaN layer 13, multi-quantum well active layer (MQW), n-GaN layer 12, n-GaN layer 11 ), the p-GaN layer 10, the p-AlGaN layer 9, and the p-GaN layer 8 are etched by dry etching to expose a portion of the upper portion of the n-GaN layer 3.

Next, a conductive layer doped with N-type impurity ions is deposited and patterned through a photolithography process to form an N-type electrode 17 on an upper portion of the n-GaN layer 3.

Next, a conductive layer doped with P-type impurity ions is deposited and patterned through a photolithography process to form a P-type electrode 18 on the p-GaN layer 16.

Since the blue semiconductor laser manufactured as described above has a pn junction only in the ridge region, and has a npnp structure in the remaining region, when a current is injected, as shown in FIG. Only current can be seen in the RIDGE) area. Accordingly, the p-AlGaN layer 9 generates light only in the ridge region and on both sides of the multi-quantum well active layer MQW on the upper side of the ridge, the refractive index of which is smaller than that of the multi-quantum well active layer MQW and the energy band gap is larger. Because of this location, the generated light is not emitted to the side but only in the vertical direction. Therefore, the confinement effect of electrons and holes is improved and has a lower oscillation start threshold current.

In addition, since the P-type electrode 18 is formed to be wider than in the related art, the contact resistance can be lowered and heat can be released in a large area without using an insulating film.

As described above, the blue semiconductor laser of the present invention and a method of manufacturing the same have a relatively low oscillation start threshold current by increasing the confinement effect to an AlGaN layer having a large band gap and a low refractive index, and reducing contact resistance by increasing the contact area of the electrode. In addition to the effect of lowering the operating voltage due to the use of an insulating film that prevents heat dissipation, there is an effect to enable efficient heat dissipation.

Claims (5)

A buffer layer 2 is deposited on the upper surface of the substrate 1, and an n-GaN layer 3, an InGaN layer 4, an n-AlGaN layer 5, and an n-GaN layer 6 are deposited on the upper surface thereof. Depositing sequentially; An oxide film 7 is deposited on the entire upper surface of the n-GaN layer 6, and the oxide film 7 is patterned to leave an oxide film 7 pattern positioned on an upper portion of the n-GaN layer 6. Thereafter, the n-GaN layer 6 exposed by the etching process using the oxide film 7 pattern as an etching mask is etched, and the n-AlGaN layer 5 and the InGaN layer 4 under the etching region are etched. Removing the upper portion of the n-GaN layer (3); The p-GaN layer on the upper surface of the structure, the n-GaN layer (3) and the InGaN layer (4), n-AlGaN layer (5), n-GaN layer (6) side of the stacked surface (8) sequentially growing the p-AlGaN layer 9, the p-GaN layer 10, and the n-GaN layer 11; The oxide film 7 pattern was removed, and the n-GaN layer 12, the multi-quantum well active layer (MQW), the p-GaN layer 13, the electron blocking layer 14, the p-AlGaN layer 15, and p Sequentially growing the GaN layer 16; P-GaN layer 16 and p-AlGaN layer, which are stacked in a region spaced a predetermined distance from a region where the InGaN layer 4, n-AlGaN layer 5, and n-GaN layer 6 are stacked. 15), electron blocking layer 14, p-GaN layer 13, multi-quantum well active layer (MQW), n-GaN layer 12, n-GaN layer 11, p-GaN layer 10, After removing the p-AlGaN layer 9 and the p-GaN layer 8 to expose the upper portion of the n-GaN layer 3, the N-type electrode 17 is formed on an upper portion of the n-GaN layer 3. ) And forming a P-type electrode (18) on top of the p-GaN layer (16). 2. The blue semiconductor as claimed in claim 1, wherein the p-GaN layer (8) is grown on the entire side surface of the n-GaN layer (6) so that the side surface of the n-GaN layer (6) is not exposed. Laser manufacturing method. A buffer layer 2 and an n-GaN layer 3 sequentially stacked on the upper surface of the substrate 1; An InGaN layer (4), an n-AlGaN layer (5), and an n-GaN layer (6) sequentially stacked on a portion of the n-GaN layer (3); An N-type electrode 17 positioned at an upper portion of the n-GaN layer 3; The n-GaN layer on the entire side surface of the InGaN layer 4, the n-AlGaN layer 5, and the n-GaN layer 6 and its periphery at a position spaced a predetermined distance from the N-type electrode 17 ( A p-GaN layer 8 located above 3); A p-AlGaN layer (9), a p-GaN layer (10), and an n-GaN layer (11) sequentially stacked on the upper surface of the p-GaN layer (8); The n-GaN layer 12, the multi-quantum well active layer (MQW), and the p-GaN layer sequentially stacked on the exposed n-GaN layer 6 and on the entire upper surface of the n-GaN layer 11 ( 13), electron blocking layer 14, p-AlGaN layer 15, p-GaN layer 16; And a P-type electrode (18) positioned so as to have a predetermined area on the upper side of the n-GaN layer (6) and on the upper part of the p-GaN layer (16) of the peripheral portion thereof. 4. The blue semiconductor laser according to claim 3, wherein the sequentially stacked InGaN layer (4), n-AlGaN layer (5), and n-GaN layer (6) are 3 mu m in width. 4. The p-AlGaN layer (9) according to claim 3, wherein the p-AlGaN layer (9) is interposed between the p-GaN layer (8) in terms of the InGaN layer (4), n-AlGaN layer (5), n-GaN layer (6). And a blue semiconductor laser, which protrudes toward the upper side of the n-GaN layer 6 to block the generated light from traveling in the vertical direction.