KR100394095B1 - Vertical cavity surface emitting laser diode and fabricating method thereof - Google Patents

Abstract

PURPOSE: A vertical cavity surface emitting laser diode and a fabricating method thereof are provided to obtain a stable operating characteristic by forming a first metal layer, a first contact layer, an active layer, a second contact layer, and a second metal layer vertically to an oscillating direction. CONSTITUTION: A vertical cavity surface emitting laser diode includes an active layer(15), a top mirror layer(17), and a bottom mirror layer(13). A first contact layer(14) is inserted between the bottom mirror layer(13) and the active layer(15). The active layer(15) is formed on one side of the first contact layer(14). A first metal layer(18) is formed on the other exposed side of the first contact layer. A second contact layer(16) is inserted between the active layer(15) and the top mirror layer(17). The top mirror layer is formed on one side of the second contact layer(16). A second metal layer(19) is formed on the other exposed side of the second contact layer(16).

Description

Vertical Resonator Surface Emitting Laser Diode and Manufacturing Method Thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical cavity surface emitting laser diode (VCSEL) and a method of manufacturing the same. In particular, it is easy to manufacture using a GaN III-V group crystal system, A vertical resonator surface emitting laser diode emitting suitable oscillating light and a method of manufacturing the same.

Conventional edge-emitting laser diodes have a resonant structure parallel to the stacked surface of the device and oscillate the laser beam in a direction parallel to the stacked surface, whereas a vertical resonator surface-emitting laser diode has a resonant structure perpendicular to the stacked surface of the device. And oscillate the laser beam in the vertical direction of the stacked surface of the device. The vertical resonator surface emitting laser diode (VCSEL) has a lower driving current and a smaller beam divergence than the edge emitting laser diode, so that optical communication, optical information recording, and holographic memory (holographic memory) memory). In addition, the vertical resonator surface-emitting laser diode (VCSEL) has a long longitudinal spacing, which basically shows a single longitudinal mode, and the oscillation start current is very low and the emission beam is symmetrical, thus combining efficiency. Due to the advantages of good coupling efficiency, the scope of application is gradually increasing.

There are many kinds of vertical resonance surface emitting lasers currently being studied, but they are classified into pure MBE type surface emitting laser diodes and composite surface emitting laser diodes depending on the manufacturing method.

Pure MBE type surface emitting laser diode is the whole structure of laser diode (upper and lower laser reflector and laser active area) is completed by MBE (or MOCVD). After MBE crystal growth, corrosion or proton injection, electrode attachment The back is very simple. In addition, the fabricated MBE type surface-emitting laser diode has the advantage of being physically quite robust.

The complex surface emitting laser diode is a case in which the laser reflector is made of a material SiO ₂ / TiO ₂ , Au, Ag, etc., instead of GaAs / AlGaAs by vacuum deposition after crystal growth is completed. In such a case, the process after crystal growth is relatively complicated, and there is a problem in the robustness, etc., but there is an advantage that the electric resistance value in the laser diode itself can be reduced.

In addition, it is roughly classified into an air post type that is formed by etching a cavity and a planar structure that restricts carriers by implanting H ⁺ .

The air post type has the advantage of low starting current because there is no leakage current, but there is a limit to maintain a proper level of refractive index difference between the resonator and the air.

1 is a vertical cross-sectional view of a vertical resonator surface emitting laser diode according to the prior art, showing an example of an H ⁺ injection planarization structure.

The conventional vertical resonator surface-emitting laser diode is a MOCVD or MBE, etc. to make a mirror surface that becomes a vertical resonator on and under the In _0.2 Ga _0.8 As active layer 4 formed on the n-GaAs substrate 2 By alternately stacking the GaAs layer and the AlGaAs layer as the lower mirror layer 3 using the epitaxy technique of the n-GaAs / AlGaAs DBR layer (distributed Bragg reflector), the upper mirror layer (5) is also the same method. The AlAs / AlGaAsDBR layer 5 is grown, and the GaAs ohmic buffer layer 6 is formed on the upper mirror layer 5, and then the lower mirror layer 3 is formed to a predetermined depth on both sides of the upper surface of the upper mirror layer 5. By selectively implanting H ⁺ up to a portion of H, the carrier passage is confined to the central portion by the injected region. In FIG. 1, reference numeral 8 denotes an H ⁺ implantation region, and 1 and 7 denote a first metal layer (n-omic metal and a second metal layer (p-omic metal).

Since the H ⁺ injection planarization structure becomes a gain waveguide structure, there is an advantage in that the basic transverse mode oscillation is performed when the size of the window in which light is emitted is small (5 μmφ or less).

However, the planarization structure also has a limit in lowering resistance because the difference in refractive index between the waveguide and the surroundings is too small to implement an appropriate wave guide, and carrier injection must pass through the upper and lower mirror layers. Therefore, there is a fundamental thermal problem that prevents stable oscillation, there is a constraint on the proper composition ratio to obtain a high reflectance, and there is a manufacturing difficulty that must go through the proton injection process.

Therefore, the present invention was devised to improve this in view of the problems of the prior art as described above, and an object of the present invention is to use a GaN-based mixed crystal compound, which is excellent in short wavelength characteristics, easy to manufacture, and excellent in thermal characteristics. A resonator surface emitting laser diode and a method of manufacturing the same are provided.

1 is a vertical cross-sectional view of a vertical resonator surface emitting laser diode according to the prior art,

2 is a vertical cross-sectional view of a vertical resonator surface emitting laser diode according to the present invention.

<Description of Symbols for Main Parts of Drawings>

1, 18: first metal layer (n-omic metal) 2, 12: substrate

3, 13: lower mirror layer 4, 15: active layer

5, 17: upper mirror layer 6: ohmic buffer layer

7, 19: second metal layer (p-omic metal) 8: H + injection region

14: first contact layer 16: second contact layer

In order to achieve the above object, the vertical resonator surface emitting laser diode according to the present invention includes an active layer interposed on an upper substrate, an upper and a lower mirror layer as a vertical resonator for resonating light emitted from the active layer, and an upper part of the active layer and In each of the vertical resonator surface-emitting laser diode formed in the lower portion, a first contact layer is interposed between the lower mirror layer and the active layer, the active layer is formed on one side of the first contact layer, the first contact layer A first metal layer, which is used as an electrode, is formed on the other exposed side of the upper surface, and a second contact layer is interposed between the active layer and the upper mirror layer, and the upper mirror layer is formed on the side of the second contact layer. The opposite side of the metal layer is formed to be exposed, and is used as an electrode on the other exposed side of the upper surface of the second contact layer. And that the second metal layer formed in its features.

In addition, in the method of manufacturing the vertical resonator surface emitting laser diode according to the present invention for achieving the above object, the lower mirror layer, the first contact layer, the active layer, the second contact layer and the upper mirror layer are sequentially arranged on the upper surface of the substrate. Crystal growth step of growing to stack; A first etching step of exposing a portion of an upper surface of the first contact layer by etching from one side of the upper mirror layer to an upper surface of the first contact layer; A second etching step of exposing a portion of the upper surface of the second contact layer by etching from the other side of the upper mirror layer after the first etching step to the upper surface of the second contact layer; A first metal layer forming step of forming a first metal layer used as an electrode on an exposed portion of the upper surface of the first contact layer in the first etching step; And a second metal layer forming step of forming a second metal layer used as an electrode on an exposed portion of the upper surface of the second contact layer in the second etching step.

Hereinafter, exemplary embodiments of a vertical resonator surface emitting laser diode and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a vertical cross-sectional view of a vertical resonator surface emitting laser diode according to the present invention.

As shown, the lower mirror layer 13, the first contact layer 14, the active layer 15, the second contact layer 16, and the upper mirror layer 17 are sequentially stacked on the substrate 12, The first metal layer 18 formed on the exposed portion of the upper surface of the first contact layer 14 and the second metal layer 19 formed on the exposed portion of the upper surface of the second contact layer 16 are provided.

In each layer composition for realizing a desired wavelength, the first and second contact layers 14 and 16 are formed of a GaN layer having excellent ohmic characteristics with the first and second metal layers 18 and 19. If the active layer 15 is an InGaN layer, the upper and lower mirror layers 17 and 13 are formed of an AlN / GaN DBR layer. If the active layer 15 is a GaN layer, the upper and lower mirror layers 17 and 13 are formed. Is preferably formed of an Al0.1Ga0.9N / AlN DBR layer.

As described above, each layer is formed, and according to the feature of the vertical resonator surface emitting laser diode of the present invention having a structure as described above, a passage through which the carrier is injected into the active layer 15 is exposed on the upper surface of the first contact layer 14. A first contact layer 14, an active layer 15, a second contact layer 16, and a second contact layer 16 disposed on an exposed portion of the upper surface of the first metal layer 11 provided at a portion of the first contact layer 14. It is formed on the line connecting the second metal layer 19 disposed opposite to the metal layer 18. Therefore, a smooth carrier is injected by the first contact layer 14 and the second contact layer 16 by GaN having low resistance characteristics, thereby lowering the threshold current, thereby lowering the lower mirror layer 13 and the upper mirror layer ( 17) can be separated from the carrier injection to form a DBR mirror layer having a high reflectance close to 99.9%. As a result, each layer can be formed so as to be suitable for emitting light corresponding to the wavelength band to be used from the desired ultraviolet region to the turquoise region. In this regard, the upper and lower mirror layers 17 and 13 are 99.9% The optical output efficiency is improved by providing a high reflectance near.

Looking at the manufacturing process of the vertical resonator surface-emitting laser diode having such characteristics, first, the lower mirror layer 13, the first contact layer 14, the active layer 15, the second on the substrate 12 in the crystal growth step The contact layer 16 and the upper mirror layer 17 are sequentially grown side by side. At this time, when the active layer 15 is formed of an InGaN layer, the lower mirror layer 13 and the upper mirror layer 17 alternately stack the GaN layer and the AlN layer at a λ / 4 thickness of the oscillation wavelength λ. Similarly, when the active layer 15 is formed of a GaN layer, the lower mirror layer 13 and the upper mirror layer 17 alternately stack an Al 0.1 Ga 0.9 N layer and an AlN layer at a lambda / 4 thickness of the oscillation wavelength. In addition, the active layer 15 is laminated to a thickness corresponding to an integer multiple of the oscillation wavelength λ, and the first and second contact layers 14 and 16 are formed of GaN layers.

Next, in the first etching step, in order to secure a space for forming the n-type ohmic metal, which is the first metal layer 18, the first contact layer is perpendicular to one side of the crystal-grown upper mirror layer 16. Etch to the top of (14).

In order to secure a space for forming the p-type ohmic metal which is the second electrode layer 19 even in the second etching step, the upper surface of the second contact layer 16 is perpendicular to the other side of the upper mirror layer 17. Etch some until.

After two etching steps, a first electrode used as an electrode on the exposed part of the upper surface of the first contact layer 14 and the exposed part of the upper surface of the second contact layer 16 in the first etching step and the second etching step. The metal layer forming step of forming the metal layer (n-type ohmic metal) 18 and the second metal layer (p-type ohmic metal) 19 is performed.

The lateral wave guide of the device manufactured as described above determines the number of modes oscillated by the outer diameter of the light exit surface.

Conventionally, p-type and n-type dopants are implanted into the upper and lower mirror layers 17 and 13, respectively, to lower the resistance in order to improve carrier injection characteristics. Since the second contact layers 14 and 16 provide a carrier injection path, the upper and lower mirror layers 17 and 13 do not need to be separately doped, and the current is limited to obtain a single transverse mode characteristic. Protons are injected into the upper and lower layers including the active layer 15 to spatially limit the energization path of the carrier. However, according to the present invention, the proton injection process is not necessary, and thus the production is easy.

As described above, the vertical resonator surface emitting laser diode according to the present invention has a carrier injection path having a carrier injection path having a first metal layer 18, a first contact layer 14, an active layer 15, and a second contact layer 16. ) And the second metal layer 19, which is formed perpendicular to the oscillation direction of the vertical resonator, so that the upper and lower mirror layers 17 and 13 are not related to carrier injection, thereby forming a mirror surface having high reflectivity. The resistance is reduced by the first contact layer 14 and the second contact layer 16 which are excellent in ohmic characteristics, and thus the threshold current is low, and the thermal characteristics are stabilized to have stable operating characteristics.

Claims (6)

In the vertical resonator surface-emitting laser diode formed on the upper and lower portions of the active layer interposed on the substrate, the upper and lower mirror layers respectively as a vertical resonator for resonating the light emitted from the active layer, A first contact layer is interposed between the lower mirror layer and the active layer, The active layer is formed on one side of the first contact layer, a first metal layer used as an electrode is formed on the exposed other side of the upper surface of the first contact layer, A second contact layer is interposed between the active layer and the upper mirror layer; The upper mirror layer is formed so that the opposite side of the first metal layer is exposed on one side of the second contact layer, and a second metal layer used as an electrode is formed on the other exposed side of the upper surface of the second contact layer. Vertical resonator surface emitting laser diode. The method of claim 1, The upper and lower mirror layers are AlN / GaN DBR layers, The active layer is an InGaN layer, And the first and second contact layers GaN layers. The method of claim 1, The upper and lower mirror layers are Al0.1Ga0.9N / AlN DBR layers, The active layer is a GaN layer, And the first and second contact layers GaN layers. A crystal growth step of sequentially growing and stacking a lower mirror layer, a first contact layer, an active layer, a second contact layer, and an upper mirror layer on an upper surface of the substrate; A first etching step of exposing a portion of an upper surface of the first contact layer by etching from one side of the upper mirror layer to an upper surface of the first contact layer; A second etching step of exposing a portion of the upper surface of the second contact layer by etching from the other side of the upper mirror layer after the first etching step to the upper surface of the second contact layer; A first metal layer forming step of forming a first metal layer used as an electrode on an exposed portion of the upper surface of the first contact layer in the first etching step; And a second metal layer forming step of forming a second metal layer used as an electrode on an exposed portion of the upper surface of the second contact layer in the second etching step. The method of claim 4, wherein The upper and lower mirror layers are AlN / GaN DBR layers, The active layer is an InGaN layer, And a first contact layer and a second contact layer GaN layer. The method of claim 1, The upper and lower mirror layers are Al0.1Ga0.9N / AlN DBR layers, The active layer is a GaN layer, And a first contact layer and a second contact layer GaN layer.