KR100710048B1 - Semiconductor laser diode and a method for manufacturing the same - Google Patents

Abstract

The present invention relates to a semiconductor laser diode and a method of manufacturing the same, comprising: sequentially depositing a lower cladding layer, an optical waveguide layer, an active layer, an upper cladding layer, and an ohmic contact layer on a substrate, and then forming a ridge formed through an etching process; An oxide layer formed on surface portions of the upper and lower cladding layers to adjust the width of the ridge; A dielectric layer formed on each of both sides of the ridge on which the oxide layer is formed; An upper electrode layer formed to surround the ohmic contact layer and the dielectric layer; And by including a lower electrode layer formed on the bottom of the substrate, it is simpler than the conventional manufacturing process of a semiconductor laser diode, it is possible to freely adjust the width of the ridge by the adjustment of the wet oxidation time as well as to automatically form ohmic contact surface It can be effective.

Semiconductor laser diode, RWG, oxide layer, ohmic contact layer, quantum dot, ridge

Description

Semiconductor laser diode and a method for manufacturing the same

1A to 1D are cross-sectional views illustrating a method of manufacturing a semiconductor laser diode according to an embodiment of the present invention.

*** Explanation of symbols on main parts of drawing ***

100: InP substrate, 110: lower cladding layer,

120a and 120b: optical waveguide layer, 130: active layer,

140: upper cladding layer, 150: ohmic contact layer,

160: first dielectric layer, 170: photoresist stripe,

180a and 180b: oxide layer, 190a and 190b: second dielectric layer,

200: upper electrode layer, 210: lower electrode layer

The present invention relates to a deep RWG (ridge waveguide) laser diode and a method for manufacturing the same using a quantum dot as an active layer for long distance optical communication, and more particularly, a part of the upper and lower cladding layers by a wet oxidation process. The present invention relates to a semiconductor laser diode and a method for manufacturing the same, which are simpler than conventional semiconductor laser diode manufacturing processes and can improve device characteristics by freely adjusting the width of the ridge and automatically forming an ohmic contact surface. .

In general, an RWG laser diode using an active layer as a quantum well has a width of an ohmic contact surface for an ohmic contact formed on an upper portion of a ridge, so that the width of the ohmic contact surface is larger than that of the ridge. Since it is small, there is a problem of lowering the characteristics of the RWG laser diode.

In order to solve these problems, there is a demand for a technique of manufacturing a RWG laser diode in such a form that the width of the ridge can be as small as possible and the ohmic contact surface can be as relatively large as possible.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to freely adjust the width of a ridge by a wet oxidation process of a portion of the upper and lower cladding layers, and automatically form an ohmic contact surface. The present invention provides a semiconductor laser diode and a method of manufacturing the same, which are simpler than the conventional semiconductor laser diode manufacturing process and can improve device characteristics.

In order to achieve the above object, the first aspect of the present invention, the lower cladding layer formed on the substrate; A ridge formed by sequentially stacking an optical waveguide layer, an active layer, an upper cladding layer, and an ohmic contact layer on the lower cladding layer, and having a predetermined width formed by left and right channel etching; An oxide layer formed on surface portions of the upper and lower cladding layers to adjust the width of the ridge; Dielectric layers formed in the left and right channels of the ridge, respectively; An upper electrode layer formed on the entire structure to surround the ridge and the dielectric layer; And to provide a semiconductor laser diode comprising a lower electrode layer formed on the bottom of the substrate.

A second aspect of the present invention provides a method for manufacturing a semiconductor device comprising: (a) sequentially forming a lower cladding layer, an optical waveguide layer, an active layer, an upper cladding layer, and an ohmic contact layer on a substrate; (b) sequentially removing the ohmic contact layer, the upper cladding layer, the active layer, and the optical waveguide layer to expose a portion of the lower cladding layer by using a predetermined photoresist as an etching mask to form a ridge having a predetermined width. Doing; (c) forming an oxide layer on exposed surface portions of the upper and lower cladding layers; (d) forming a dielectric layer to surround the ridge on the entire structure; (e) removing the dielectric layer to expose the ohmic contact layer; (f) forming an upper electrode layer on the entire structure to surround the ridge and the dielectric layer; And (g) to provide a method for manufacturing a semiconductor laser diode comprising the step of forming a lower electrode layer on the bottom of the substrate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to fully understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the embodiments described below. It doesn't happen. Like numbers refer to like elements in the figures.

1A to 1D are cross-sectional views illustrating a method of manufacturing a semiconductor laser diode according to an embodiment of the present invention.

Referring to FIG. 1A, for example, a lower cladding layer 110, an optical waveguide layer 120a, an active layer 130, an optical waveguide layer 120b, an upper cladding layer 140, and an ohmic contact layer may be formed on an InP substrate 100. 150) are formed sequentially.

In this case, the lower cladding layer 110 is an n-type In _0.52 Al _0.48 As layer lattice matched with the InP substrate 100, and has a thickness range of about 1 μm to 2 μm (preferably, about 1.5 μm). It is preferable to form so that it has.

The optical waveguide layers 120a and 120b are undoped-In _0.52 Al _0.25 Ga _0.23 As layers of a SCH (Seperate Confinement Heterostructure) structure that is lattice matched with the InP substrate 100 and are about 130 nm to 170 nm ( Preferably, it is preferably formed to have a thickness range of about 150nm).

The active layer 130 is a spontaneous InAs quantum dot formed from InAs having about 3.2% lattice mismatch with the InP substrate 100, and an undoped-In _0.52 Al _0.25 Ga _0.23 lattice matched with the InP substrate 100. Preferably, the As barrier layer is repeatedly formed at about 3 to 7 cycles. Here, the thickness of the barrier layer may vary from about 15 nm to 30 nm.

The upper cladding layer 140 is a p-type In _0.52 Al _0.48 As layer lattice matched with the InP substrate 100 and is formed to have a thickness range of about 1 μm to 2 μm (preferably, about 1.5 μm). It is preferable to.

The ohmic contact layer 150 is a p-type In _0.53 Ga _0.47 As layer lattice matched with the InP substrate 100 and is formed to have a thickness range of about 130 nm to 170 nm (preferably about 150 nm). It is preferable to.

Meanwhile, the lower cladding layer 110, the optical waveguide layers 120a and 120b, the active layer 130, the upper cladding layer 140, and the ohmic contact layer 150 may be, for example, molecular beam epitaxy. , MBE or metal organic vapor deposition (Metalorganic Chemical Vapor Deposition, MOCVD) is preferably formed using.

Referring to FIG. 1B, after depositing the first dielectric layer (SiNx) 160 in a thickness range of about 180 nm to 220 nm (preferably about 200 nm) on the ohmic contact layer 150, A predetermined photoresist is applied.

Next, a photoresist stripe 170 is formed to form a ridge having a predetermined width r through, for example, a photo-lithography process.

Referring to FIG. 1C, by using the photoresist strip 170 as an etch mask, the first dielectric layer 160 is etched to the same width through a dry or wet etching process, for example, and then the photoresist strip 170 ).

Next, using the first dielectric layer 160 remaining after the etching as an etching mask, for example, the ohmic contact layer 150 and the upper portion to expose the lower cladding layer 110 through a dry or wet etching process. The cladding layer 140, the optical waveguide layer 120b, the active layer 130, and the optical waveguide layer 120a are sequentially removed.

At this time, to form a deep ridge structure, it is preferable to remove to the predetermined thickness of the lower cladding layer 110.

Here, the ridge is a portion of the lower cladding layer 110, the optical waveguide layer 120a, the active layer 130, the optical waveguide layer 120b, the upper cladding layer 140, and the ohmic. The convex protruding center portion formed of the contact layer 150 is referred to.

Referring to FIG. 1D, for example, a wet oxidation process is performed at a temperature range of about 480 to 520 ° C. (preferably, about 500 ° C.) for about 1 to 7 hours in a water vapor (H ₂ O) atmosphere. Oxide layers (Al-oxides) 180a and 180b are formed on the surface portions of the upper and lower cladding layers 140 and 110, respectively.

In this case, the oxidation rate of the In _0.52 Al _0.48 As layer is about 162.5 nm / hr in a direction parallel to the InP substrate 100, and about 185.5 nm / hr in a direction perpendicular to the InP substrate 100. The oxidation rate of the In _0.52 Al _0.25 Ga _0.23 As layer is about 1/100 of the In _0.52 Al _0.48 As layer. The reason why the oxidation rates of the two layers (In _0.52 Al _0.48 As layer and In _0.52 Al _0.25 Ga _0.23 As layer) are different is that the Al concentrations of the two layers are different from each other.

Accordingly, the width (r) of the ridge can be freely adjusted in a state where the oxidation degree of the active layer 130 is very small compared to the upper and lower cladding layers 140 and 110 by adjusting the wet oxidation time.

After the oxidation process, second dielectric layers (SiNx) 190a and 190b are deposited in a thickness range of about 180 nm to 220 nm (preferably about 200 nm) to cover the ridge on the entire structure. Thereafter, the ohmic contact surface may be automatically formed by removing the ohmic contact layer 150 until it is exposed using, for example, a dry etching method.

In this case, the dry etching may be performed by, for example, magnetically enhanced reactive ion etching (MERIE).

Next, a p-type metal upper electrode layer 200 is formed on the entire structure to surround the ridges and the second dielectric layers 190a and 190b, and wraps a lower end of the InP substrate 100. After forming the lower electrode layer 210 of the n-type metal on the bottom of the InP substrate 100 to complete a quantum dot deep RWG semiconductor laser diode according to an embodiment of the present invention.

Although a preferred embodiment of the above-described semiconductor laser diode and its manufacturing method according to the present invention has been described, the present invention is not limited thereto, and various modifications are made within the scope of the claims and the detailed description of the invention and the accompanying drawings. It is possible to carry out by this and this also belongs to the present invention.

According to the semiconductor laser diode of the present invention and a method of manufacturing the same as described above, the width of the ridge is freely controlled by a part of the upper and lower cladding layers of the deep ridge structure by a wet oxidation process. By forming an ohmic contact surface, the width of the ridge can be sufficiently reduced to improve the device characteristics due to the reduction of the oscillation threshold current density and the contact resistance of the device, and there is a simple advantage compared to the manufacturing process of the conventional semiconductor laser diode. .

Claims (14)

A ridge formed through an etching process after sequentially laminating a lower cladding layer, an optical waveguide layer, an active layer, an upper cladding layer, and an ohmic contact layer on a substrate; An oxide layer formed on surface portions of the upper and lower cladding layers to adjust the width of the ridge; A dielectric layer formed on each of both sides of the ridge on which the oxide layer is formed; An upper electrode layer formed to surround the ohmic contact layer and the dielectric layer; And And a lower electrode layer formed on the bottom of the substrate. The semiconductor laser diode of claim 1, wherein the optical waveguide layer is further formed between the active layer and the upper cladding layer. The semiconductor laser diode of claim 1, wherein the upper and lower cladding layers are p-type and n-type InAlAs layers lattice matched with the substrate, respectively. The semiconductor laser diode of claim 3, wherein the upper and lower cladding layers are formed in a thickness range of 1 μm to 2 μm. The semiconductor laser diode according to claim 1, wherein the optical waveguide layer is an undoped InAlGaAs layer having a SCH structure lattice matched with the substrate. The semiconductor laser diode according to claim 5, wherein the optical waveguide layer is formed in a thickness range of 130 nm to 170 nm.  The method of claim 1, wherein the active layer is formed by repeating 3 to 7 cycles by spontaneously forming an InAs quantum dot spontaneously formed from InAs having a lattice mismatch with the substrate and an undoped InAlGaAs barrier layer lattice matched with the substrate. A semiconductor laser diode. The semiconductor laser diode of claim 1, wherein the ohmic contact layer is a p-type InGaAs layer lattice matched with the substrate. The semiconductor laser diode of claim 8, wherein the ohmic contact layer is formed in a thickness range of 130 nm to 170 nm. (a) sequentially depositing a lower cladding layer, an optical waveguide layer, an active layer, an upper cladding layer and an ohmic contact layer on the substrate; (b) forming a ridge by sequentially removing the ohmic contact layer, the upper cladding layer, the active layer, and the optical waveguide layer so that a portion of the lower cladding layer is exposed using a photoresist as an etching mask; (c) forming oxide layers on the surface portions of the upper and lower cladding layers; (d) forming a dielectric layer to surround the ridge on which the oxide layer is formed; (e) etching the dielectric layer to expose the ohmic contact layer; (f) forming an upper electrode layer to surround the exposed ohmic contact layer and the dielectric layer; And (g) forming a lower electrode layer on the bottom of the substrate. The method of claim 10, wherein in the step (b), the ridge is formed using dry or wet etching. The method of claim 10, wherein in the step (c), the oxide layer is formed by performing a wet oxidation process in the temperature range of 480 to 520 ℃ for 1 to 7 hours in a water vapor (H ₂ O) atmosphere. Method of manufacturing a semiconductor laser diode. The method of claim 10, wherein in the step (e), the dielectric layer is removed using a dry etching method. The method of claim 13, wherein the dry etching method is a magnetic field enhanced reactive ion etching method (MERIE).

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