KR100278632B1 - Laser diode and manufacturing method thereof - Google Patents

Abstract

A short wavelength laser diode having excellent reliability and a method of manufacturing the same are disclosed. The present invention provides a laser diode in which a buffer layer, a lower cladding layer, an active layer, and an upper cladding layer are sequentially formed on a substrate, a ridge is formed on the upper cladding layer, and a current stop layer is provided on both sides of the ridge. The current stop layer is sequentially stacked, and the n-material layer doped with the first impurity, the p-material layer doped with the second impurity and the n-material layer doped with the first or third impurity It is provided.

According to the present invention, since the current stop layer is formed of the n-material layer / p-material layer / n-material layer, p-n-p-n junction is formed to effectively prevent leakage of the carrier.

Description

Laser diode and manufacturing method thereof

1 is a schematic cross-sectional view of a laser diode according to the prior art.

2 is a schematic cross-sectional view of a laser diode according to the present invention.

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

10, 50: n-substrate 12, 52: n-buffer layer

14, 54: n-cladding layer 16, 56: active layer

18, 58: p-cladding layer 20, 65: current stop layer

22, 66: p-contact layer 24, 68: p-cap layer

26, 70: electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode and a method of manufacturing the same, and more particularly, to a short wavelength laser diode having excellent reliability and a method of manufacturing the same. In general, lasers generated by induced emission are characterized by unidirectional light, directivity, and high intensity. Gas lasers such as helium-neon lasers, argon lasers, and YAG lasers There are various types, ranging from solid state lasers such as ruby lasers to semiconductor lasers that are small and easy to modulate by modulating bias current at high frequencies.

The semiconductor laser is a semiconductor device including a concept of quantum electrons based on a PN junction, and induces electron-hole recombination by artificially injecting current into a thin film made of a semiconductor material, that is, an active layer, resulting in recombination. It is a semiconductor laser diode that emits light corresponding to reduced energy.

In recent years, the performance of semiconductor lasers has grown epitaxially to develop materials that determine wavelengths and to realize device structures that determine characteristics and reliability such as critical current, light output, oscillation efficiency, single wavelength, and spectral line width. Significant developments are being made due to advances in technology and micromachining technology. In particular, in the epitaxial growth technology, the organic organic vapor deposition (hereinafter referred to as "MOCVD") method and the molecular beam epitaxy (Molecular Beam Epitaxy): The atomic level can be controlled by the MBE method.

The semiconductor laser diode is smaller in size, cheaper in price, and particularly capable of controlling intensity through current control than a solid state laser such as a He-Ne gas laser or an Nd: YAG laser. The semiconductor laser diode is an information processing device such as a compact disc player (CDP), an optical memory, a high-speed laser printer, and an optical communication device, and replaces a conventional gas laser such as helium-neon. Is widening.

On the other hand, GaInP / AlGaInP laser diodes, which are used as short-wavelength light sources in these fields, have attracted much attention recently due to the increased use of products such as optical disk memories, laser beam printers, and barcode readers.

In order to form the index-guide laser SBR (Selectively Buried Ridge) structure which is the most widely used to date, it has to go through three stages of MOCVD growth process. Recently, a simpler method has been developed by shortening the three-step MOCVD growth process to two-step MOCVD growth.

1 is a schematic cross-sectional view of a laser diode manufactured by a conventional two-step MOCVD growth process.

Referring to FIG. 1, on an n-GaAs substrate 10, an n-GaAs buffer layer 12, an n- (Al _0.7 Ga) _0.5 InP cladding layer 14, and a u-GaInP active layer 16. , p- (Al _0.7 Ga) InP cladding layer 18, p-GaInP contact layer 20 and p-GaAs cap layer 22 are sequentially formed by the first MOCVD growth method. Subsequently, a ridge is formed by selectively etching the p-cap layer 22, the p-contact layer 20 and the p-cladding layer 18 so that the p-cladding layer 18 remains about 0.2-0.3 μm. . Next, the n-GaAs current stop layer 20 is selectively formed only on both sides of the ridge by the secondary MOCVD growth method. Subsequently, an electrode 26 made of chromium and aluminum is formed on the resultant product.

The laser diode manufactured by the conventional two-step MOCVD growth process described above is subjected to reverse bias in the current stop layer 20 made of n-GaAs because the electron diffusion distance in GaAs is about 1 μm. The electrons will leak. Therefore, it is not suitable for obtaining a high power laser diode.

Accordingly, an object of the present invention is to provide a high output short wavelength laser diode having high efficiency and excellent reliability.

It is also an object of the present invention to provide a method of manufacturing a laser diode which is particularly suitable for manufacturing the laser diode.

In order to achieve the above object, in the laser diode according to the present invention, a buffer layer, a lower cladding layer, an active layer, and an upper cladding layer are sequentially formed on an upper portion of the substrate, and a ridge is formed on the upper cladding layer. In the laser diode in which the current stop layers are provided on both sides and the electrodes are provided above and below the stack, the current stop layers are sequentially stacked, the n-material layer doped with the first impurity and the second impurity. And a doped p-material layer and an n-material layer doped with first or third impurities.

It is preferable to use GaAs as the material of the material layer, the material of the substrate and the buffer layer is n-GaAs, the material of the lower cladding layer is n- (Al _0.7 Ga) _0.5 InP, the material of the active layer is GaInP, the upper cladding layer The material of p- (Al _0.7 Ga) InP is used.

A contact layer and a cap layer may be further provided on the top surface of the ridge.

In addition, the method of manufacturing a laser diode according to the present invention for achieving the above another object, the step of sequentially forming a buffer layer, a lower cladding layer, an active layer and an upper cladding layer on the substrate by a first organometallic vapor phase growth method; ; Etching both upper sides of the upper cladding layer to form a ridge protruding at a predetermined height at a center thereof; And a second organic layer on both sides of the ridge, the n-material layer doped with the first impurity, the p-material layer doped with the second impurity, and the n-material layer doped with the first or third impurity. It is characterized in that it comprises a step of forming a current stop layer by sequentially growing by a metal vapor deposition method.

The method may further include sequentially forming a contact layer and a cap layer on the upper cladding layer between the growth of the upper cladding layer and the etching step.

In the present invention, a current stopping is formed by growing an n-material layer / P-material layer n-material layer by a two-step MOCVD growth method. Therefore, by forming a p-n-p-n junction it is possible to effectively prevent carrier leakage in the current stop layer. Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a schematic cross-sectional view of a laser diode according to the present invention. Referring to FIG. 2, an n-GaAs buffer layer 52, an n- (Al _0.7 Ga) _0.5 InP cladding layer 54, a u-GaInP active layer 56, and p are formed on the n-GaAs substrate 50. -(Al _0.7 Ga) InP cladding layer 58, p-GaInP contact layer 66, and p-GaAs cap layer 64 are sequentially formed. The ridge including the p-contact layer 66 and the p-cap layer 68 is formed on the p-cladding layer 58. On both sides of the ridge, a current stop layer 65 made of an n-GaAs layer 60 / p-GaAs layer 62 / n-GaAs layer 64 is formed. An electrode 70 made of chromium and aluminum is formed on the p-cap layer 68 and the current stop layer 65.

Hereinafter, the manufacturing method of the laser diode of the present invention shown in FIG. 2 will be described.

Specifically, on the n-GaAs substrate 50, n-GaAs buffer layer 52, n- (Al _0.7 Ga) _0.5 InP cladding layer 54, u-GaInP active layer 56, p- (Al _0.7 Ga The InP cladding layer 58, the P-GaInP contact layer 66, and the P-GaAs cap layer 68 are sequentially formed by the first MOCVD growth method. Subsequently, silicon dioxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ) is deposited on the resultant, for example, by plasma-enhanced chemical vapor deposition (PECVD) or sputtering. This is patterned to form a mask pattern (not shown) for ridge formation. Next, using the mask pattern, the p-cap layer 68, the p-contact layer 66 and the p-cladding layer 58 are left so that the p-cladding layer 58 remains about 0.2 to 0.3 mu m. By etching, a ridge, that is, a stripe is formed. Subsequently, the n-GaAs layer 60, the p-GaAs layer 62, and the n-GaAs 64 are sequentially grown by the second MOCVD growth method in the state where the stripe portion is blocked by the mask pattern. The current stop layer 65 is formed at portions except the stripe portion. Here, another material may be used instead of GaAs as the material constituting the current stopping layer 65. Next, after removing the mask pattern, the laser diode is completed by forming an electrode 70 made of chromium and aluminum on the resultant.

As described above, the laser diode according to the present invention uses a current stopping layer made of n-GaAs / p-GaAs / n-GaAs instead of the current stopping layer made of only n-GaAs. Therefore, since the p-n-p-n junction is formed, reverse bias is not applied to the current stopping layer, and leakage of the carrier can be effectively prevented.

In addition, an index-guided laser diode can be manufactured by a two-step MOCVD growth process that is simpler than a conventional three-step MOCVD growth process.

In such a laser diode of the present invention, the material of each layer can be changed depending on the conditions whose characteristics are required, so the laser diode of the present invention is not limited by the material of each layer.

As mentioned above, although the specific Example of this invention was described and described, this invention is not limited to the said Example, The deformation | transformation and improvement are possible within the range of the common knowledge which a person skilled in the art has.

Claims (7)

A buffer layer, a lower cladding layer, an active layer, and an upper cladding layer are sequentially formed on the substrate, a ridge is formed on the upper cladding layer, and a current stop layer is provided on both sides of the ridge. In the laser diode provided with the electrode, the current stopping layer is sequentially stacked, the n-material layer doped with the first impurity, the p-material layer doped with the second impurity and the first or third And an n-material layer doped with an impurity. The laser diode of claim 1, wherein the material of the material layer is GaAs. The material of claim 1, wherein the material of the substrate and the buffer layer is n-GaAs, the material of the lower cladding layer is n- (Al _0.7 Ga) _0.5 InP, the material of the active layer is GaInP, and the material of the upper cladding layer is p-. (Al _0.7 Ga) InP is a laser diode. The laser diode according to claim 1, wherein a contact layer and a cap layer are formed on the top surface of the ridge. Sequentially forming a buffer layer, a lower cladding layer, an active layer and an upper cladding layer on the substrate by a first organometallic vapor phase growth method; Etching both upper sides of the upper cladding to form a ridge protruding at a predetermined height at a center thereof; And a second organic layer on both sides of the ridge, the n-material layer doped with the first impurity, the p-material layer doped with the second impurity, and the n-material layer doped with the first or third impurity. A method of manufacturing a laser diode comprising the step of sequentially growing by a metal vapor deposition method to form a current stop layer. The method of manufacturing a laser diode according to claim 5, wherein GaAs is used as a material of the material layer. 6. The method of claim 5, further comprising sequentially forming a contact layer and a cap layer on the upper cladding layer between the growth of the upper cladding layer and the etching step. 7.