KR100657905B1 - Semiconductor laser diode with photoresonant layers on both sides of active layer - Google Patents

Abstract

The present invention relates to a semiconductor laser diode. A semiconductor laser diode, comprising: a semiconductor substrate; A lower clad layer formed on the semiconductor substrate an n-type Al _x Ga _1-x As (o <x <1) lower optical resonant layer formed on the lower clad layer; An active layer formed on the lower optical resonance layer; An upper p-type Al _y Ga _1-y As (0 <y <) formed on the active layer and formed on the active layer of Al than the lower photoresonant layer, and having a larger molar fraction of Al than the lower photoresonant layer. 1) It provides a semiconductor laser diode having a light resonant layer formed on both sides of the active layer including;

Description

Semiconductor laser diode with optical resonance layer formed on both sides of active layer {Semiconductor Laser Diode with Optical Cavities}

1 is a cross-sectional view of a semiconductor laser diode having an optical resonant layer according to the prior art.

2 is a cross-sectional view of a semiconductor laser diode having optical resonant layers on both sides of an active layer according to an embodiment of the present invention.

3 is an enlarged view of the active layer and the optical resonant layer of FIG. 2.

4A illustrates an optical mode of a semiconductor laser diode having optical resonant layers on both sides of an active layer according to an exemplary embodiment of the present invention.

FIG. 4B is a view illustrating an optical mode of a semiconductor laser diode having the optical resonant layer of FIG. 1.

<Description of Symbols for Main Parts of Drawings>

100, 200 ... semiconductor substrate 101, 201 ... buffer layer

102, 202 ... lower cladding layer 103, 203 ... active layer

104 ... top light resonant layer 105 ... etch stop layer

106, 204 ... Upper cladding layer 107, 207 ... Electricity double layer

108, 208 ... Current blocking layer 109, 209 ... Cap layer

110, 210 ... upper electrode 111, 211 ... lower electrode

221 ... lower optical resonant layer 222 ... upper optical resonant layer

The present invention relates to a semiconductor laser diode, and more particularly, to a semiconductor laser diode in which optical resonant layers having different refractive indices are formed on both sides of an active layer.

Lasers used in various fields, such as light sources of information processing devices, require high output to increase information density. The high power operation of a laser diode is limited by the device's power saturation and catastrophic optical damage (COD).

The output saturation phenomenon is caused by the deformation of the gain distribution at high current injection density, and can be overcome by optimizing the structure of the device to reduce the drive current density. On the other hand, COD is a phenomenon in which the light emitting surface is damaged by the local temperature rise occurring at the light emitting surface of the laser diode. A non-absorbing mirror (NAM) structure and a thin active layer (TAL) are used. It can be overcome by employing a structure or an optical cavity to widen the optical mode to lower the optical power density at the light emitting surface.

Here, the optical resonant layer is a material layer having an energy band gap between the active layer and the cladding layer having an energy band gap between the active band and the energy bandgap of the cladding layer. Through the layers. The optical mode can be widened by introducing such an optical resonant layer.

1 is a view showing a structure of a semiconductor laser diode having a light resonance layer according to the prior art.

Referring to FIG. 1, the semiconductor substrate 100 has a structure including a buffer layer 101, a lower clad layer 102, an active layer 103, and an optical resonant layer 104. Here, the material of each layer will be described with an InGaP / InGaAlP-based short wavelength laser diode as an example. The semiconductor substrate 100 may be formed of n-type GaAs, and the buffer layer 101 may be formed of n-type GaAs. The lower clad layer 102 may be formed of n-type InGaAlP, the active layer 103 may be formed of InGaP, and the optical resonant layer 104 may be formed of an InGaAlP layer.

An etch stop layer 105 is formed on the photoresonant layer 104, an upper cladding layer 106 is formed in an upper central region thereof, and a current blocking layer 108 is formed around the upper cladding layer 106. It is. An easy conducting layer 107 is formed on the upper cladding layer 106, and a cap layer 109 is formed on the current interrupting layer 108 and the easily conducting layer 107. The upper electrode 110 is formed on the cap layer 109, and the lower electrode 111 is provided below the semiconductor substrate 100. The etch stop layer 105 is formed of p-type InGaP and the upper clad layer 106 is formed of p-type InGaAlP. The easy conduction layer 107 is formed of p-type GaAs, the current blocking layer 108 is formed of n-type GaAs, and the cap layer 109 is formed of p-type GaAs. The upper electrode 110 and the lower electrode 111 are each formed of a conductive material.

The aforementioned structure as shown in FIG. 1 has the following disadvantages.

First, when the upper cladding layer 106 is formed, the light mode is biased toward the upper cladding layer 106, because the material doped with the p-type impurity may cause lattice defects of the upper cladding layer 106. Terminate

Second, when the lower clad layer 102 is formed of an In _0.5 (Ga _0.6 Al _0.4 ) _0.5 P material, a large amount of lattice defects such as hillock may be generated due to the material properties, and thus, the lower clad layer 102 may be formed on the lower clad layer 102. Crystal quality growth of the InGaP active layer 103 becomes difficult. When the crystalline growth of the active layer 103 becomes difficult, an internal loss such as scattering loss occurs and a driving current density increases, which makes it difficult to operate the laser diode at high power.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art, and to provide a semiconductor laser diode capable of wider optical mode and operating at higher power.

In the present invention to achieve the above object

In the semiconductor laser diode,

Semiconductor substrates;

A lower clad layer formed on the semiconductor substrate;

An n-type Al _x Ga _1-x As lower optical resonant layer formed on the lower clad layer;

An active layer formed on the lower optical resonance layer;

A p-type Al _y Ga _1-y As (0 <y <1) upper optical resonant layer formed on the active layer and having a larger Al mole fraction than the lower optical resonant layer;

It provides a semiconductor laser diode having a light resonant layer formed on both sides of the active layer including; an upper clad layer formed on the upper optical resonance layer.

In the present invention, the refractive index of the upper optical resonant layer is larger than the refractive index of the lower optical resonant layer.

In the present invention, the Al mole fraction of the upper optical resonant layer is larger than the Al mole fraction of the lower optical resonant layer.

In the present invention, the upper clad layer has a mesa structure protruding from the center portion, the current blocking layer formed in the region except the protruding center portion of the upper clad layer on the upper clad layer;

An easy conduction layer formed on a protruding center portion of the upper clad layer; And

And a cap layer formed on the current blocking layer and the energization easy layer.

In the present invention, a lower electrode formed under the semiconductor substrate; And

And an upper electrode formed on the cap layer.

In the present invention, the active layer is formed of InGaP, the lower clad layer is formed of n-type InGaAlP,

The upper clad layer is formed of p-type InGaAlP.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the semiconductor laser diode formed with the light resonant layer on both sides of the active layer according to an embodiment of the present invention.

2 is a cross-sectional view of a semiconductor laser diode in which a light resonance layer is formed on both sides of an active layer according to an embodiment of the present invention.

Referring to FIG. 2, the semiconductor substrate 200 includes a buffer layer 201, a lower clad layer 202, a multilayer lower optical resonant layer 221, an active layer 203, and a multilayer upper optical resonant layer 222. It has a structure to

An upper cladding layer 204 having a mesa structure is formed on the upper optical resonant layer 222, and a current blocking layer 208 is formed in an area except for a central flat portion of the upper cladding layer 204. An easy conducting layer 207 is formed on the central flat portion of the upper cladding layer 204 where the current interrupting layer 208 is not formed, and a cap layer 209 is formed on the current interrupting layer 208 and the easy conducting layer 207. Is formed.

Here, the material of each layer will be described. The semiconductor substrate 200 is formed of n-type GaAs and the buffer layer 201 is formed of n-type GaAs. The lower clad layer 202 is formed of n-type InGaAlP, and the active layer 203 is formed of InGaP. In addition, the energization easy layer 207 is made of p-type GaAs, and the current blocking layer 208 is made of n-type GaAs. The cap layer 209 is made of p-type GaAs. The upper electrode 210 and the lower electrode 211 are formed of a conductive material, for example, a p-type metal and an n-type metal, respectively.

Hereinafter, referring to FIG. 3, the lower optical resonant layer 221 and the upper optical resonant layer 222, which are characteristics of a semiconductor laser diode having optical resonant layers formed on both sides of an active layer according to an exemplary embodiment of the present invention, are as follows. . The lower photoresonant layer 221 and the upper photoresonant layer 222 are formed on both sides of the InGaP active layer 203, respectively. The lower photoresonant layer 221 is formed of n-type Al _x Ga _{1- x} As, and the upper photoresonant layer 222 is formed of p-type Al _y Ga _{1- y} As.

Here, the Al mole fraction of the n-type Al _x Ga _1-x As lower optical resonant layer 221 is formed to be smaller than the Al mole fraction of the p-type Al _y Ga _1-y As upper optical resonant layer 222. That is, it grows by adjusting so that x <y (0 <X <Y <1). AlGaAs may be formed so that the active layer 203 has excellent crystallinity due to excellent crystallinity, and the optical mode may be defined by controlling the mole fraction of Al to control energy band gap and refractive index inside the optical resonant layer. That is, when the Al mole fraction in the n-type Al _x Ga _1-x As upper optical resonant layer 222 is larger than the lower optical resonant layer 221, the energy band gap is relatively increased and the refractive index is lowered. This has the effect of further limiting the light mode.

Referring to FIGS. 4A and 4B, the operation principle of a semiconductor laser diode having light resonant layers formed on both sides of an active layer according to an embodiment of the present invention will be described below.

Referring to FIG. 4A, the laser oscillated in the active layer 203 introduces a lower optical resonant layer 221 and an upper optical resonant layer 222, thereby expanding the optical mode during optical waveguide. In the case of the laser diode of FIG. 1 according to the prior art of FIG. 4B, the optical mode has been widened to the regions of the active layer 103 and the upper optical resonant layer 104, but the optical mode has been lost due to lattice defects of the upper cladding layer 16. It can be seen that it is shifted upward.

When the optical resonant layers on both sides of the active layer according to the embodiment of the present invention of FIG. 4A are introduced to show a difference in refractive index, the optical mode L1 of the oscillation laser is slightly biased toward the lower optical resonant layer 221. . If the same problem as in the prior art of FIG. 1 occurs, that is, the lattice defect caused by p-type impurities is formed when the upper clad layer 204 is formed, the optical mode L2 compensates for this.

The n-Al _x Ga _{1- x} As lower optical resonant layer 221 has a smaller amount of lattice defects due to dopants, compared to conventional optical resonant layers formed of InGaAlP or the like. Accordingly, when operating at high power, optical degradation due to lattice defects is prevented, and unlike the conventional InGaAlP optical resonant layer, hillock is unlikely to occur, and the active layer is promoted to crystal growth thereon.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments, rather than to limit the scope of the invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the technical spirit described in the claims.

According to the present invention has the following advantages.

First, by introducing an optical waveguide layer having different refractive indices above and below the active layer, it is possible to correct distortion of the optical mode caused by crystal defects caused by impurities in the upper clad layer. There is an advantage that can prevent deterioration.

Second, the internal current such as scattering loss is reduced, the driving current is lowered, and the thermal saturation level of the device is increased.

Claims (6)

In the semiconductor laser diode, Semiconductor substrates; A lower clad layer formed on the semiconductor substrate; A lower optical resonant layer including n-type Al _x Ga _1-x As (0 <x <1) formed on the lower clad layer; An active layer formed on the lower optical resonance layer; A p-type Al _y Ga _1-y As (0 <y <1) upper optical resonant layer formed on the active layer and having a larger Al mole fraction than the lower optical resonant layer; And an upper clad layer formed on the upper optical resonant layer. The semiconductor laser diode having the optical resonant layer formed on both sides of the active layer. delete delete The method of claim 1, The upper clad layer has a mesa structure protruding from the center, A current blocking layer formed on an area of the upper clad layer except for a protruding center portion of the upper clad layer; An easy conduction layer formed on a protruding center portion of the upper clad layer; And And a cap layer formed on the current blocking layer and the energizing easy layer. The semiconductor laser diode having a light resonance layer formed on both sides of the active layer. The method of claim 4, wherein A lower electrode formed under the semiconductor substrate; And And an upper electrode formed on the cap layer. The semiconductor laser diode having a light resonance layer formed on both sides of the active layer. The method of claim 1, The active layer is formed of InGaP, The lower clad layer is formed of n-type InGaAlP, The upper clad layer is a semiconductor laser diode having a light resonance layer formed on both sides of the active layer, characterized in that formed of p-type InGaAlP.

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