KR100490803B1 - High-power single-mode vertical-cavity surface-emitting laser - Google Patents

Abstract

Surface emitting lasers are used as light sources for optical wiring and optical communication. In particular, high power single mode surface emitting lasers are rapidly increasing in need as light sources for short / near field communication and high speed data communication. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high power single mode surface emitting laser, and is a structure and a manufacturing method of a single mode surface emitting laser having a high diameter and high power characteristic by independently adjusting current limiting and optical mode induction regions.

Description

High power single mode surface emitting laser device and manufacturing method {High-power single-mode vertical-cavity surface-emitting laser}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single mode surface emitting semiconductor laser device, and more particularly, to a large diameter single mode surface emitting laser structure and a manufacturing method through independent control of a current limiting layer and a light guide layer region.

Surface-emitting lasers are used as light sources for short- and short-range communication, and their applications are rapidly increasing. Especially for the next generation optical communication and signal processing due to the high fiber-coupling efficiency of surface emitting laser, low unit cost by wafer-based manufacturing process, low mounting cost, and two-dimensional array characteristics It is expected to settle quickly as a light source. However, the commercially available surface-emitting lasers in the 850 nm band are mainly characterized by multiple transverse modes, and thus have limited transmission distance due to chromatic dispersion in high speed optical and data communications. In order to overcome this problem, development efforts for a single transverse mode light source have been made. Furthermore, there is a need for the development of stable surface emission lasers with single mode outputs for use in high speed data communication, optical interconnection, and optical sensors using single mode optical fibers, which are in increasing market demand.

Surface-emitting lasers have a single mode characteristic in the longitudinal direction with a resonance distance of a wavelength, but exhibit a multi-mode characteristic in the transverse direction depending on the current. Therefore, the oscillation emission angle of the light is changed by the change of the current, and thus the coupling efficiency with the optical fiber is changed. Proton-implanted VCSELs and oxide-confined VCSELs, which are widely used in order to obtain single lateral mode characteristics, have to have a diameter of less than or equal to 5 µm and less than or equal to 3 µm, respectively. In addition, since the diameter of the device is small, the output characteristics are poor, and the spread of the beam is also increased, which causes difficulties in optical fiber coupling and free space optical connection.

Conventional single-mode surface-emitting laser technology has a method of reducing the diameter of the device so that high-order transverse oscillation does not occur in proton-implanted VCSEL and oxide-confined VCSEL. Therefore, it is difficult to obtain high output characteristics, and it is difficult to secure reproducibility and yield according to the fabrication of small diameter beam emission window. In addition, the divergence angle due to the small diameter has a big disadvantage. In addition, various structures such as antiguided, surface-reliefed, metal-filtered, and oxidized / implanted have been proposed. Such structures basically increase the induced loss of the higher-order transverse mode, weaken the light induction, or increase the gain and modulus between the basic transverse mode and the higher-order transverse mode. These structures are designed to increase the gain by increasing the optical coupling with the basic lateral mode distribution. However, these structures have a complicated manufacturing process and thus have difficulty in securing reproducibility. Structures such as surface-relief and oxidized / implanted surface emitting lasers have complex drawbacks, such as the need for etching, implantation and oxidation of the surface layer, respectively.In the case of antiguide structures, high refractive index materials such as amorphous GaAs materials Difficulties in selection and regrowth / deposition. In addition, other metal-filtered methods have a disadvantage of lowering the laser oscillation efficiency as a method of suppressing high-order transverse oscillation by reducing the beam emitting window.

The present invention proposes a reproducible and large-diameter single mode surface emitting laser structure and a manufacturing method through independent control of the current limiting layer and the light guide layer in a simple fabrication process.

The present invention relates to a high power single mode surface emitting semiconductor laser, which simultaneously forms a double oxide film and independently regulates current limit and optical mode induction, thereby providing a high power single mode surface emitting laser device and a method of manufacturing the same in a reproducible and simple process. The purpose is to.

A high power single mode surface emitting laser array device of the present invention for achieving the above object, the active layer formed of a lower mirror layer and a quantum well layer consisting of n-type doped semiconductor distributed Bragg reflector (DBR) sequentially stacked on a semiconductor substrate; A light induction layer for adjusting an optical mode size on the active layer; A first upper mirror layer composed of a p-type doped semiconductor DBR sequentially stacked on the light induction layer to become part of the upper mirror; A second upper mirror layer is formed of a current limiting layer for controlling the current flow region on the first upper mirror layer and a p-type doped semiconductor DBR sequentially stacked thereon to be part of the upper mirror. Here, the light induction layer and the current limiting layer are different in thickness or composition from each other to form the current limiting and light inducing regions independently of each other using a single oxide film forming process. Since the current flow region formed in the current limiting layer is smaller than the optical mode region formed by the light guide layer, the gain of the basic transverse mode is greatly increased so that only the oscillation of the basic transverse mode occurs, and the oscillation of the higher-order transverse mode with small gain is suppressed. Large diameter, high power single mode surface emitting laser oscillation is achieved.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

1A illustrates a cross-sectional view of a high power single mode surface emitting laser device structure in accordance with a preferred embodiment of the present invention. In the figure, 21 is an n-type semiconductor substrate, 22 is a lower mirror layer composed of n-layer semiconductor DBR, 23 is an active layer composed of a gain layer and a space layer of a multilayer quantum well for gain, and 24 is a light induction for light induction. Layer, 25 is a first upper mirror layer composed of a p-type semiconductor DBR to form part of the upper mirror, 26 is a current limiting layer for controlling current flow, and 27 is composed of a p-type semiconductor DBR to form part of the upper mirror. The 2nd upper mirror layer which comprises is shown, respectively. 28 is a low refractive index photo-induced oxide layer formed by oxidizing a part of the 24 light-induced layer, 29 is an insulating current-limiting oxide layer formed by oxidizing a part of the 26 current limiting layer, and 30, 32, and 33 are respectively The p-type electrode, electrode pad, and n-type electrode for injecting electric current are shown. And 31 is an insulating layer for insulating the device.

FIG. 1B is an enlarged comparison of the current flow region and the light mode of the current limiting layer 26, the current limiting oxide layer 29, the light guide layer 24, and the light guide oxide layer 28 shown in FIG. One cross section. When the current limiting oxide layer 29 and the photo-induced oxide layer 28 are respectively adjusted to form a current flow region having a diameter d ₁ smaller than the optical mode induction region having a diameter d ₀ so that the gain is large in the middle of the mode regions, In the middle, the gain of the basic transverse mode with the large intensity of the mode is greatly increased, and the gain of the higher order transverse mode with the large intensity of the mode at the edge is greatly reduced, so that only the basic transverse mode is oscillated. Therefore, it has the surface emission laser characteristic of the single mode oscillation which oscillates only basic sulfur mode.

Referring to FIG. 1, the n-type semiconductor DBR layer as the lower mirror layer 22 on the n-type GaAs semiconductor substrate 21 is Al _x Ga _1-x As / Al _y Ga _ly As (0 ≦ x, y ≦ 1) and the like, and an active layer 23 composed of an AlGaAs / GaAs quantum well layer and a space layer is formed in a lattice matched structure to GaAs for laser gain thereon. The light induction layer 24 for light induction is formed on the active layer 23, and a part of the light induction layer 28 is formed to form an oxide film 28. The first upper mirror layer 25 and the second upper mirror layer 27 are p-type semiconductors DBR Al _x Ga _1-x As / Al _y Ga _1-y As (0 ≤ x, y ≤ 1, respectively). And a current limiting layer 26 for inducing current, between which a portion is formed by an oxide film 29 or the like to insulate so that current flows only in a desired region.

The current flowing area has a smaller diameter than the light inducing area so that only the middle part of the light inducing area flows, so that only the light in the center gets a large gain.

The semiconductor DBR layers constituting the upper mirror layers 25 and 27 and the lower mirror layer 22 of the surface-emitting laser are lattice matched to GaAs and have Al _x Ga _1-x As / Al _y Ga _1-y As (0). The semiconductor thin film layers having different refractive indices, such as ≤ x, y ≤ 1), are alternately grown, and the thickness of one cycle is configured to be half of the laser oscillation wavelength at an optical length (thickness x refractive index at the oscillation wavelength). The active layer 23 is composed of a quantum well and a space layer structure, and is configured such that the total thickness is an integer multiple of half the oscillation wavelength with an optical length. The light guide layer 24 and the current limiting layer 26 are p-type Al _x Ga _1-x As (0 ≤ x ≤ 1) according to the structure of the laser, and mineral oil which is an oxidized region for the light induction. And the current limiting oxide layer 29, which is an oxidized region for limiting the current.

2 is an experimental result showing an oxide film formation depth according to Al composition of Al _x Ga _1-x As (0 ≦ x ≦ 1). Depending on the Al composition, even if the same time is oxidized, the oxide film formation depth is different. Therefore, when the Al composition of the current limiting layer 26 and the Al composition of the light inducing layer 24 are different, the current limiting oxide layer 29 and the light inducing oxide layer 28 of different depths can be formed simultaneously. In other words, for example, when the posts having a diameter of 40 μm are used and the Al compositions of the current limiting layer 26 and the light inducing layer 24 are 99.5% and 99.1%, respectively, an oxide film forming process is performed for 29 minutes. The current confined oxide film layer 29 and the photo-induced oxide film layer 28 of about 16 μm and 15 μm are formed to form a current limiting region and a light inducing region of d _I to 8 μm, d ₀ to 10 μm, respectively. In addition, even if the thickness of the current limiting layer 26 and the light induction layer 24 is different, the current limiting region and the light induction region can be independently controlled in the same manner as described above.

3A to 3E are cross-sectional views showing a method of manufacturing a high power single mode surface emitting laser having the structure of FIG.

First, referring to FIG. 3A, an n-type semiconductor substrate 41, a lower mirror layer 42 composed of n-type DBRs, an active layer 43 composed of quantum wells and a space layer, and mineral oil for mineral induction through oxide film formation A coating layer 44, a first upper mirror layer 45 composed of a p-type DBR, a current limiting layer 46 for limiting current through oxide film formation, and a second upper mirror layer 47 composed of a p-type DBR. Grow sequentially.

As shown in FIG. 3B, the laser post is formed by a dry etching method for isolation between the surface emitting laser devices. That is, after the pattern is formed using the photoresist 48, the second upper mirror layer 47, the current limiting layer 46, and the dry etching method using the Cl ₂ : Ar mixturer using the photoresist 48 as a mask. A portion of the first upper mirror layer 45 and the light guide layer 44 are etched to produce a laser post.

Subsequently, as shown in FIG. 2C, after removing the photoresist 48, a portion of the current limiting layer 46 and the light guide layer 44 are oxidized using a wet oxidation process, respectively. The light guide oxide film layer 49 is formed. When the current limiting layer 46 and the light inducing layer 44 are grown, the thickness or Al composition of the current limiting layer 46 is adjusted to be larger than that of the light inducing layer 44 so that the depth of forming the current limiting oxide layer 50 is light induced. It is larger than the oxide film layer 49. That is, the diameter d _I of the current flowing region limited by the current limiting oxide film 50 is formed to be smaller than the diameter d ₀ of the light inducing region limited by the photo-induced oxide film 49. The wet oxidation process is performed by heat treatment at about 380-450 ° C. in an atmosphere where N ₂ passing through H ₂ O flows.

Subsequently, as shown in FIG. 3D, a dielectric thin film of SiN _x , SiO _x, etc. is deposited on the insulating layer 51, and then a photoresist pattern is formed to etch away the insulating layer on the laser post, and then, on the laser post. A p-type electrode 52 in the form of a ring is deposited.

FIG. 3E deposits an electrode pad 53 and an n-type electrode 54 on a region including a portion of the p-type electrode and the back surface of the substrate 41 in the fabricated structure to fabricate a high power single mode surface emitting laser.

4 is a cross-sectional view of a structure that is another embodiment of the high power single mode surface emitting laser of the present invention. The light guide layer 64 is positioned below the active layer 63, and thus the light guide oxide layer 68 is also positioned below the active layer to determine the light guide region. Another embodiment of a high power single mode surface emitting laser structure through independent regulation of is shown.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The high power single mode surface emitting laser of the present invention is a large-diameter surface emitting laser structure in which only the basic transverse mode is oscillated by independently controlling the current flow region and the light induction region to be used as a high power single mode surface emitting laser structure and manufacturing method. Can be.

1A-1B show a cross-sectional view, current flow and light induction of a high power single mode surface emitting laser structure of the present invention.

2 is an experimental result showing a difference in the formation depth of the oxide film according to the Al composition.

3A-3E illustrate a method of manufacturing a high power single mode surface emitting laser of the present invention.

4 is a cross-sectional view showing another embodiment of the high power single mode surface emitting laser of the present invention.

* Explanation of symbols for main parts of the drawings

21: n-type substrate

22: bottom mirror consisting of n-layer semiconductor DBR

23 active layer

24: Light guide layer for optical guide

25: first mirror layer composed of p-layer semiconductor DBR

26: current limiting layer for current confinement

27: second top mirror layer composed of p-layer semiconductor DBR

28: light guide oxide layer for light induction

29: current limiting oxide layer for current limiting

30: p-type electrode

31: insulation layer

32: electrode pad

33: n-type electrode

d ₀ : diameter of the light guide region limited by the photo-induced oxide film

d ₁ : diameter of the current flowing region limited by the current-limiting oxide film

Claims (8)

In the surface emitting laser device, An active layer formed of an n-type doped lower mirror layer and a quantum well layer sequentially stacked on the semiconductor substrate; A light induction layer for inducing light through forming an oxide film on the active layer; A first upper mirror layer composed of a p-type doped semiconductor DBR sequentially stacked on the light induction layer to become part of the upper mirror; A current limiting layer for regulating a current flow region on the first upper mirror layer; It consists of a second upper mirror layer consisting of a p-type doped semiconductor DBR sequentially stacked on the current limiting layer to be part of the upper mirror, The light guide layer and the current limiting layer is a high power single mode surface emission laser device, characterized in that the light guide oxide layer and the current limiting oxide layer are formed independently of each other by using a single oxide film forming process by varying the thickness or composition of each other. The method of claim 1, The semiconductor DBR layer constituting the first upper mirror layer, the second upper mirror layer, and the lower mirror layer has a lattice matched structure to GaAs, and Al _x Ga _1-x As / Al _y Ga _1-y As (0 ≦ x, A high power single mode surface emitting laser device characterized in that the thickness of one cycle is made to be half of the laser oscillation wavelength by the optical length, when the semiconductor thin film layers having different refractive indices such as y ≤ 1) are alternately grown. The method of claim 1, The active layer is a lattice matched structure to GaAs, which is composed of a quantum well and a space layer structure such as AlGaAs / GaAs, and has a high power single mode surface emitting laser device, characterized in that the total thickness is an integer multiple of half the oscillation wavelength. . The method of claim 1, The light inducing layer and the current limiting layer are Al _x Ga _1-x As (0 ≤ x ≤ 1) having a lattice matched structure to GaAs, and the Al composition or thickness of the current limiting layer is Al composition or thickness of the light inducing layer. A high power single mode surface emitting laser device characterized in that it is made larger. An active layer formed of an n-type doped lower mirror layer and a quantum well layer sequentially stacked on the semiconductor substrate; A light induction layer for inducing light through forming an oxide film on the active layer; A first upper mirror layer composed of a p-type doped semiconductor DBR sequentially stacked on the light induction layer to become part of the upper mirror; A current limiting layer for regulating a current flow region on the first upper mirror layer; It consists of a second upper mirror layer consisting of a p-type doped semiconductor DBR sequentially stacked on the current limiting layer to be part of the upper mirror, The light guide layer and the current limiting layer have a high power single mode surface emitting laser device, characterized in that the light guide oxide layer and the current limiting oxide layer are formed independently of each other using a single oxide film forming process by varying the thickness or composition of each other. In the manufacturing method, And partially oxidizing the light guide layer to form a light guide oxide film layer for light induction. An active layer formed of an n-type doped lower mirror layer and a quantum well layer sequentially stacked on the semiconductor substrate; A light induction layer for inducing light through forming an oxide film on the active layer; A first upper mirror layer composed of a p-type doped semiconductor DBR sequentially stacked on the light induction layer to become part of the upper mirror; A current limiting layer for regulating a current flow region on the first upper mirror layer; It consists of a second upper mirror layer consisting of a p-type doped semiconductor DBR sequentially stacked on the current limiting layer to be part of the upper mirror, The light guide layer and the current limiting layer have a high power single mode surface emitting laser device, characterized in that the light guide oxide layer and the current limiting oxide layer are formed independently of each other using a single oxide film forming process by varying the thickness or composition of each other. In the manufacturing method, And partially oxidizing the current limiting layer to form a current limiting oxide film layer for current insulation. An active layer formed of an n-type doped lower mirror layer and a quantum well layer sequentially stacked on the semiconductor substrate; A light induction layer for inducing light through forming an oxide film on the active layer; A first upper mirror layer composed of a p-type doped semiconductor DBR sequentially stacked on the light induction layer to become part of the upper mirror; A current limiting layer for regulating a current flow region on the first upper mirror layer; It consists of a second upper mirror layer consisting of a p-type doped semiconductor DBR sequentially stacked on the current limiting layer to be part of the upper mirror, The light guide layer and the current limiting layer may be formed independently of each other using a single oxide film forming process by varying the thickness or composition of the light guide layer and the current limiting oxide layer. The light inducing layer and the current limiting layer are Al _x Ga _1-x As (0 ≤ x ≤ 1) having a lattice matched structure to GaAs, and the Al composition or thickness of the current limiting layer is Al composition or thickness of the light inducing layer. In the method of manufacturing a high power single mode surface emitting laser device, characterized in that to further increase, The light-induced layer and the current-limiting layer are simultaneously oxidized to form a photo-induced oxide layer and a current-limiting oxide layer, respectively, wherein the unoxidized current limiting layer area is smaller than that of the non-oxidized light inducing layer. Method of manufacturing a mode surface emitting laser device. The method of claim 7, wherein The photo-induced oxide layer and the current-limiting oxide layer are partially oxidized in the light-induced layer and the current-limiting layer, respectively, by using a wet oxidation process in which a heat treatment is performed at about 380 to 450 ° C. under an atmosphere of flowing N ₂ through H ₂ O. A method of manufacturing a high power single mode surface emitting laser device, characterized in that it is formed.