KR100915056B1 - Nitrides semiconductor laser diode - Google Patents

Abstract

The present invention relates to a nitride semiconductor laser diode, comprising: an n-nitride semiconductor layer formed on an n-nitride semiconductor substrate, the portion of which is removed to have a ridge region; A stacked epitaxial layer formed by sequentially stacking an n-clad layer, an n-wave guide layer, an active layer, an anti-etching layer, and a p-wave guide layer on the ridge region of the n-nitride semiconductor layer; A dielectric film surrounding a side surface of the laminated epitaxial layer and formed on the n-nitride semiconductor layer; A p-clad layer covering an upper surface of the p-wave guide layer of the laminated epitaxial layer and formed to a part of the upper portion of the dielectric layer; A p-cap layer surrounding the p-clad layer and formed on the dielectric layer; A p-metal layer surrounding the p-cap layer and formed on the remaining dielectric layer; It consists of an n-metal layer formed below the n-nitride semiconductor substrate.

 Therefore, the present invention improves the binding force of the applied current and at the same time the effect of improving the optical characteristics and I-V characteristics occurs.

Description

Nitrides semiconductor laser diode

The present invention relates to a nitride semiconductor laser diode, and more particularly, to form a p-clad layer formed around a top surface of a p-wave guide layer and formed to a part of an upper part of a dielectric film, thereby improving the binding force of an applied current and simultaneously improving optical characteristics and IV. The present invention relates to a nitride semiconductor laser diode capable of improving characteristics.

In general, Nitrides semiconductor laser diodes have been developed and mass-produced for application to large-capacity data storage devices and color printers.

Recently, several new applications using nitride semiconductor laser diodes have been attempted.

In order to apply such a nitride semiconductor laser diode to a large capacity data storage device and a color printer, the device requires a low threshold current (I _th ) and a high external quantum efficiency (η _ex ).

In addition, although it is optimal that the horizontal / vertical aspect ratio becomes '1' in far field patterns (FFP), most nitride semiconductor laser diodes deviate from this condition.

Therefore, in the optical head optical system (optical system) employing a nitride semiconductor laser diode, a loss of light output occurs, requiring the development of a new nitride semiconductor laser diode that solves this problem.

Currently, all nitride compound semiconductor laser diodes have a ridge type structure, and a dielectric film is stacked next to the ridge as shown in FIG. 1 for passivation and transverse mode control of the device.

1 is a cross-sectional view of a general nitride semiconductor laser diode, wherein an n-clad layer 11, an n-wave guide layer 12, an active layer 13, and an anti-etching layer 14 are formed on an n-nitride semiconductor substrate 10. ), the p-wave guide layer 15 and the p-clad layer 16 are sequentially stacked.

The p-clad layer 16 has a ridge protruding from the center thereof, and a p-cap layer 18 is formed on the ridge. The ridge and the ridge of the p-clad layer 16 are formed. A dielectric film 17 is formed on the side of the p-cap layer 18.

In addition, a p-metal layer 20 is formed on the p-cap layer 18 and the dielectric layer 17.

In addition, an n-metal layer 21 is formed under the n-nitride semiconductor substrate 10.

The dielectric film formed on the side of the above-mentioned ridge is SiO ₂ (applied by NEC Corporation and Nichia Chemical Corporation) (n = 1.45-1.46), which has a large refractive index difference from that of the laminated epilayer formed of AlGaN and GaN (n = 1.45-1.46). ZrO ₂ (applied by Nichia Chemical Corporation) (refractive index (n) = 1.97) and SiON (n = 1.7) (applied by Xerox Palo Alto Research Center).

Simulation results show that the ridge wave guide laser diode has a kink in the LI (photo-current) characteristic and the horizontal / vertical aspect ratio is the width of the ridge and the remaining thickness. It has been found to be directly related to the (Residual Thickness) (distance between the active layer and the side etched to form the ridge) and the refractive index of the dielectric.

Therefore, the ridge waveguide laser diode currently in use has a small horizontal index step at the junction plane and a large current spread, so it is difficult to optimize the horizontal / vertical aspect ratio. Current confinement force is lowered, and there is a problem that kink occurs in light-current characteristics.

FIG. 2 is a cross-sectional view of a nitride semiconductor laser diode having improved characteristics than that of FIG. 1, and an n-nitride semiconductor layer having a ridge 111a formed on the n-nitride semiconductor substrate 110 by removing an upper surface thereof. 111 is formed.

In addition, an n-clad layer 112, an n-wave guide layer 113, an active layer 114, an anti-etching layer 115, a p-wave guide layer 116, and a p-clad on the ridge 111a. Layer 117 and p-cap layer 118 are stacked sequentially.

The dielectric layer 150 is formed on the n-nitride semiconductor layer 111 on the side of the ridge 111a.

The nitride semiconductor laser diode of FIG. 2 configured as described above has an advantage described later than the nitride semiconductor laser diode of FIG. 1.

That is, the refractive index of the dielectric film 150 and the n-clad layer 112, the n-wave guide layer 113, the active layer 114, the anti-etching layer 115, the p-wave guide layer 116, and the p-clad The effective refractive index of the epi-layers composed of the layer 117 and the p-cap layer 118 is large so that the horizontal radiation angle of the light is reduced, thereby reducing the horizontal / vertical radial angle ratio (Aspect). Ratio can be improved.

In addition, the current injected into the p-cap layer 118 does not flow to the dielectric layer 150, so that the applied current can be confined to the epi layer only, thereby reducing the leakage current, thereby reducing the threshold current. I _th ) can be lowered.

However, the nitride semiconductor laser diode of FIG. 2 has the following disadvantages despite the above advantages.

First, it is difficult to form an epi layer stacked on the ridge of the n-nitride semiconductor layer 111.

Second, the resistance is larger than that of the nitride semiconductor laser diode of FIG. 1, resulting in deterioration of I-V characteristics, and there is a possibility of heat generation around a portion where current is conducted.

Third, there is a possibility that the active layer is damaged by an etching process performed to form an epi layer stacked on the ridge of the n-nitride semiconductor layer 111, thereby deteriorating the light emitting characteristics of the optical device.

Accordingly, the present invention has been made to solve the problems described above, by forming a p- clad layer formed to cover the upper surface of the p-wave guide layer to a portion of the upper part of the dielectric film, thereby improving the constraint force of the applied current and at the same time optical characteristics And a nitride semiconductor laser diode capable of improving IV characteristics.

A preferred aspect for achieving the above object of the present invention comprises: an n-nitride semiconductor layer formed on top of an n-nitride semiconductor substrate, the portion of which is removed to have a ridge region;

A stacked epitaxial layer formed by sequentially stacking an n-clad layer, an n-wave guide layer, an active layer, an anti-etching layer, and a p-wave guide layer on the ridge region of the n-nitride semiconductor layer;

A dielectric film surrounding a side surface of the laminated epitaxial layer and formed on the n-nitride semiconductor layer;

A p-clad layer covering an upper surface of the p-wave guide layer of the laminated epitaxial layer and formed to a part of the upper portion of the dielectric layer;

A p-cap layer surrounding the p-clad layer and formed on the dielectric layer;

A p-metal layer surrounding the p-cap layer and formed on the dielectric layer;

There is provided a nitride semiconductor laser diode comprising an n-metal layer formed under the n-nitride semiconductor substrate.

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

3 is a cross-sectional view of a nitride semiconductor laser diode according to the present invention, which is formed on the n-nitride semiconductor substrate 210 and has a portion of the n-nitride semiconductor layer 211 having a ridge region. and; The n-clad layer 212, the n-wave guide layer 213, the active layer 214, the anti-etching layer 215, and the p-wave guide on the ridge region of the n-nitride semiconductor layer 211. A laminated epi layer formed by sequentially laminating layers 216; A dielectric film 270 surrounding a side surface of the stacked epitaxial layer and formed on the n-nitride semiconductor layer 211; A p-clad layer 217 formed to cover a top surface of the p-wave guide layer 216 of the laminated epitaxial layer and formed to a part of an upper portion of the dielectric layer 270; A p-cap layer 218 surrounding the p-clad layer 217 and formed on the dielectric layer 270; A p-metal layer 220 surrounding the p-cap layer 218 and formed on the remaining dielectric layer 270; It is composed of an n-metal layer 210 formed under the n-nitride semiconductor substrate 210.

Therefore, the present invention is characterized in that the cross-sectional area of the p-clad layer 217 is larger than that of the p-wave guide layer 216.

In order to manufacture a nitride semiconductor laser diode according to the present invention, first, an n-nitride semiconductor layer 211, an n-clad layer 212, an n-wave guide layer 213, an active layer on top of a sapphire or nitride semiconductor substrate 214, the etch stop layer 215 and the p-wave guide layer 216 are sequentially stacked.

Next, a dry etching process such as chemically assisted ion beam etching (CAIBE) is removed from the p-wave guide layer 216 to a portion of the n-nitride semiconductor layer 211.

Thereafter, in order to constrain the current, the dielectric layer 270 is formed to surround the upper portion of the n-nitride semiconductor layer 211 and the etched side surface.

The p-clad layer 217 is formed on the dielectric film 170 and the p-wave guide layer 216 formed as above, and a part of the p-clad layer 217 is removed by a conventional photolithography process. , To form a shape surrounding the top surface of the p-wave guide layer 217.

Subsequently, the p-clad layer 117 is wrapped to form a p-cap layer 118 on the upper portion of the dielectric layer 170, and the p-cap layer 118 surrounds the p-cap layer 118 on the p-metal layer. Form 120.

In the case of manufacturing the semiconductor laser diode of the present invention on the sapphire substrate, the side surface of the n-nitride semiconductor layer 211 is extended to form an n-metal layer on the upper portion of the nitride semiconductor substrate. When the device is manufactured, as shown in FIG. 3, an n-metal layer is formed under the nitride semiconductor substrate.

The n-nitride semiconductor substrate 210, the n-nitride semiconductor layer 211, the n-wave guide layer 213, the p-wave guide layer 216 and the p-cap layer 218 are formed of GaN. Preferably, the p and n-clad layers 217 and 212 are formed of AlGaN.

The present invention thus constructed has the following advantages.

First, the depth for dry etching the portion of the current flowing in contact with the p-metal layer is shallower than that of the conventional semiconductor laser diode shown in FIG. 2, thereby reducing physical and chemical damage to the active layer during etching.

This improves the optical characteristics of the optical device.

Secondly, the contact surfaces of the p-clad layer, the p-cap layer and the p-metal layer are widened to improve the I-V characteristics of the device.

Therefore, there is an advantage that can improve the binding force of the applied current and at the same time improve the optical characteristics and I-V characteristics.

As described in detail above, the present invention forms an p-clad layer formed on a portion of the dielectric film surrounding the upper surface of the p-wave guide layer, thereby improving the binding force of the applied current and simultaneously improving the optical and IV characteristics. Occurs.

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.

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

FIG. 2 is a cross-sectional view of a nitride semiconductor laser diode having improved characteristics than FIG. 1.

3 is a cross-sectional view of a nitride semiconductor laser diode according to the present invention.

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

10,110,210: n-compound semiconductor substrate 11,112,212: n-clad layer

12,113,213: n-wave guide layer 13,114,214: active layer

14,115,215: Anti-etching layer 15,116,216: p-wave guide layer

16,117,217 p-clad layer 17,150,270 oxide film

18,118,218: p-cap layer 20,120,220: p-metal layer

21,121,221 n-metal layer 111,211 n-nitride semiconductor layer

111a: Ridge

Claims (3)

an n-nitride semiconductor layer formed over the n-nitride semiconductor substrate, the portion of which is removed to have a ridge region; A stacked epitaxial layer formed by sequentially stacking an n-clad layer, an n-wave guide layer, an active layer, an anti-etching layer, and a p-wave guide layer on the ridge region of the n-nitride semiconductor layer; A dielectric film surrounding a side surface of the laminated epitaxial layer and formed on the n-nitride semiconductor layer; A p-clad layer covering an upper surface of the p-wave guide layer of the laminated epitaxial layer and formed to a part of the upper portion of the dielectric layer; A p-cap layer surrounding the p-clad layer and formed on the dielectric layer; A p-metal layer surrounding the p-cap layer and formed on the dielectric layer; A nitride semiconductor laser diode comprising an n-metal layer formed under the n-nitride semiconductor substrate. The method of claim 1, The cross-sectional area of the p-clad layer is larger than the cross-sectional area of the p-wave guide layer. The method of claim 1, The n-nitride semiconductor substrate, n-nitride semiconductor layer, n-wave guide layer, p-wave guide layer and p-cap layer is formed of GaN, And the p and n-clad layers are made of AlGaN.