KR100223834B1 - Blue laser diode - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide a blue laser diode in which crystal bonds due to lattice matching and temperature expansion coefficient are excluded by using an n-GaN substrate grown by halogen vapor deposition (HVPE) method and a method of manufacturing the same.

In order to achieve the above object, the blue laser diode of the present invention comprises the steps of preparing an n ⁺ type GaN substrate grown by homogeneous thin film growth using a halogen vapor thin film growth method, and n doped with silicon on the n ⁺ type substrate, respectively. Forming by sequentially growing an n-type GaN layer, an n-type 1n _x Ga _1-x N layer (0≤x≤1), an n-type Al _x Ga _1-x N layer, and an n-type GaN layer; Alternately growing a plurality of well layers of ln _0.2 Ga _0.8 and a barrier layer of ln _0.05 Ga _0.95 N on the layer to form an active layer having a multi-quantum well layer structure, and P-type AlxGa ₁ doped with Mg on the active layer, respectively; forming a _-x N layer, a P-type GaN layer, a P-type Al _x Ga _lx N layer, and a P-type GaN layer, and an n-type ohmic contact electrode and a P-type ohmic on the bottom of the substrate and on the P-type GaN layer, respectively And forming a contact electrode.

Description

Blue laser diode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device and a method for manufacturing the same, and more particularly, to a high brightness, high efficiency blue laser diode manufactured using a gallium nitride based thin film obtained by homogeneous thin film growth (Homoepitaxy), and a method for manufacturing the same.

Conventional blue laser diodes are Al _x Ga _lx N and ln _x Ga _1-x N (0≤) which are gallium nitride (GaN) based compound semiconductors on a surface sapphire substrate by using organometallic chemical vapor deposition as shown in FIG. x≤1) was prepared by growing a thin film.

GaN compound semiconductors grown in this way have poor crystallinity due to lattice mismatch (13.8%) and thermal expansion coefficient difference (25%) between GaN and sapphire substrate, resulting in crystal defects of about 10 ¹⁰ cm ^-2. Due to the bonding, it was difficult to obtain a good P-type GaN compound semiconductor.

In addition, in order to form a cavity in the laser diode, a mirror surface must exist. Reactive ion etching (RIE) using Cl ₂ gas plasma is mainly used to obtain a perfect mirror surface and fine irregularities are generated. Due to the poor efficiency and high threshold current, the room temperature continuous oscillation of the blue laser diode could not be achieved.

In addition, as shown in FIG. 2, the spinel substrate ((III) MgAl ₂ 0 ₄ ) is used to kill the lattice mismatch (9.5%) to increase the thin film crystal of the GaN compound semiconductor and to improve the flatness of the mirror surface. However, there was a limit to improving the characteristics of the laser diode.

In order to obtain a cleaving surface for generating the mirror surface of the resonator, the laser diode grows a GaN compound semiconductor by MOCVD using an a surface 1120 sapphire substrate as shown in FIG. It was very difficult to have a cleaved surface in a GaN compound semiconductor on a sapphire substrate which had a cleaved blue laser diode but virtually did not have a cleaved surface.

Therefore, the sapphire or spinel substrate, in which the laser diode structure is grown, is wrapped as thin as possible (less than 50 μm) to have a GaN-based wall interface. As described above, the thin film of the laser diode structure has lattice mismatch with the substrate and thermal expansion. Due to the large difference in coefficient, the crystallinity is poor, and thus a thin strain film is formed, and when lapping, such crystal defects generate a lot of cracks in the laser diode structure, resulting in a very poor chip generation yield and a thin film crystal. Due to the characteristics, the characteristics of the laser diode are not significantly improved than those of the mirror surface formation by etching, and there are still many problems in continuous room temperature oscillation for a long time.

Therefore, the present invention was invented in view of the above-described problems of the prior art, and by using the n ⁺ -GaN substrate grown by the halogen vapor phase film growth (HVPE) method, the blue color which eliminated crystal bonds due to lattice mismatch and temperature expansion coefficient was excluded. It is to provide a laser diode and a method of manufacturing the same.

1 shows a cross-sectional view of a conventional blue laser diode.

Figure 2 shows a cross-sectional view of the blue laser diode of the present invention.

* Explanation of symbols for main parts of the drawings

10: n ⁺ type GaN layer 11: n type GaN layer

12: n-type ln _0.05 Ga _0.95 N layer 13: n-type Al _0.05 Ga _0.95 N layer

14: n-type GaN layer 15: active layer

16: P-type Al _0.2 Ga _0.8 N layer 17: P-type GaN layer

18: P type Al _0.05 Ga _0.95 N layer 19: P type GaN layer

20: n-type ohmic contact electrode 21: p-type ohmic contact electrode

In order to achieve the above object, the blue laser diode of the present invention comprises the steps of preparing an n ⁺ type GaN substrate grown by homogeneous thin film growth using a halogen vapor thin film growth method, and an n type doped with silicon on the n ⁺ type substrate, respectively. Sequentially growing a GaN layer, an n-type ln _x Ga _lx N layer (0≤x≤1), an n-type Al _x Ga _1-x N layer, and an n-type GaN layer, and ln on the n-type GaN layer Growing a plurality of well layers of _0.2 Ga _0.8 and a layer of ln _0.05 Ga _0.95 N alternately to form an active layer having a multi-quantum well layer structure, and P-type Al _x Ga _1- doped with Mg on the active layer, respectively; forming an _x N layer, a P type GaN layer, a P type Al _x Ga _1-x N layer, and a P type GaN layer, and an n type ohmic contact electrode and a P type on the bottom of the substrate and the top of the P type GaN layer, respectively. And forming an ohmic contact electrode.

In addition, the method for manufacturing a blue laser diode of the present invention for achieving the above object, n-type GaN layer formed by doping the silicon on the n ⁺ type GaN substrate, respectively, grown by the growth of the symmetric thin film using a halogen vapor film growth method, n Ln _0.2 Ga _0.8 well layer and ln on the type ln _x Ga _1-x N layer (0≤x≤1), n-type Al _x Ga _1-x N layer and n-type GaN layer, and the final n-type GaN layer A multi-quantum well-type active layer in which a barrier layer of _0.05 Ga _0.95 N is alternately stacked a plurality of times, and a P-type Al _x Ga _1-x N layer and a P-type GaN layer each of Mg-doped layers sequentially grown and stacked on the active layer And an n-type ohmic contact electrode and a p-type ohmic contact electrode formed on a lower portion of the substrate and an upper portion of the final P-type GaN layer, respectively, on a P-type Al _x Ga _1-x N layer and a P-type GaN layer. It is characterized.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings of the present invention.

The blue laser diode of the present invention is a 300-350 μm-thick n ⁺ gallium nitride substrate 10 and gallium nitride substrate 10 obtained by silicon doping of a predetermined concentration after being grown by homogeneous thin film growth using a halo vapor phase thin film growth method. N-type GaN layer of about 3μm thick silicon doping formed on the N-type GaN layer, ln _0.05 Ga _0.95 N layer 12 of 1000 Å-thickness silicon-doped formed as a buffer layer on the n-type GaN layer 11, and the n-type ln _0.05 Ga _0.95 N layer 12 on silicon doped with n-type cladding layer 4000 Å on conventional n-type Al _0.05 Ga _0.95 N layer 13 and on n-type Al _0.05 Ga _0.95 N layer 13 Laminated structure of silicon doping formed of the light guide layer, n-layer GaN layer 14 having a thickness of 70 Å, ln _0.05 Ga _0.95 N, which is a barrier layer of 50 Å acting as an active layer, and ln _0.2 Ga _0.8 N, which is a well layer having a thickness of 30 Å P-type Mg doping with a thickness of 200 μs formed on the multiple quantum well layer 15 Al _0.2 Ga _0.8 N layer 16 and the P-type Al _0.2 Ga _0.8 N thickness formed on the layer 16, 70Å Mg-doped P-type GaN layer 17 and a P clad formed on the GaN layer 17, the P-type 4000Å thick layer of Mg-doped P-type Al _0.05 Ga _0.95 N layer 18 and the P-type Al _0.05 Ga _0.95 N layer 18, the ball guide layer of Mg-doped P-type having a thickness of 4000Å is formed on the GaN layer 19 And an n-type electrode 20 and a P-type electrode 21 formed on the lower portion of the substrate N ⁺ type GaN 10 and on the P-type GaN layer 19, which is the light guide layer, respectively.

The N-type GaN (11) layers and the P-type GaN (19) layers respectively formed on the substrate N ⁺ -type GaN (10) layers are all formed by the same kind of organometallic chemical vapor deposition as described later.

The multilayer quantum well layer 15 has a lamination structure of ln _0.05 Ga _0.95 having a thickness of 50 kHz as a barrier layer and ln _0.2 Ga _0.8 N having a thickness of 30 _인 as a well layer.

According to the blue laser diode of the present invention having the above structure, the n ⁺ GaN layer 11 laminated on the n ⁺ GaN substrate (10) is much better than that formed by heterogeneous thin film growth using a buffer layer on a conventional sapphire substrate. Thin film growth can be achieved to solve the fundamental problem caused by the lattice negative pressure and the temperature expansion coefficient.

Meanwhile, a method of manufacturing the blue laser diode of the present invention having the above structure will be described with reference to FIG. 2.

First, a 300-350 μm-thick n ⁺ GaN substrate 10 obtained by growing a homogeneous thin film by using a halogen vapor thin film growth method and doping with a predetermined concentration of silicon is prepared.

An organometallic chemical vapor deposition method is formed on the n ⁺ GaN type substrate 11 to form an n type GaN layer 11 of silicon exposure having a thickness of about 3 μm at a temperature of 1010 ° C.

At this time, SiH ₄ or Si ₂ H ₆ is used as the silicon source.

Subsequently, in order to form a buffer layer on the n-type GaN 11, an n-type ln _0.05 Ga _0.95 N layer 12 having a thickness of 1000 Å and silicon doped is grown at a temperature of 800 ° C. in the same manner as in the previous step. Then, on the n-type ln _0.05 Ga _0.95 N layer 12 to form an n-type cladding layer, a silicon-doped n-type Al _0.05 Ga _0.95 N layer 13 was formed at a temperature of 4000Å at a temperature of 1010 ° C. in the same manner as in the previous step. To grow. Subsequently, a silicon doped nGaN layer 14 having a thickness of 70 층 was grown on the n-type Al _0.05 Ga _0.95 N layer 13 at a temperature of 1010 ° C. in the same manner as in the previous step to form a positive guide layer, and then an active layer was formed. InGaN-based multi-quantum well layer 15 was formed by alternately growing a barrier layer of 50 μm In _0.05 Ga _0.95 N layer and a well layer of 30 μm In _0.05 Ga _0.95 N layer three to five times at a temperature of 780 ° C. Form. Then, using an organometallic chemical vapor deposition method, the Mg-doped P-type Al _0.2 Ga _0.8 N layer 16 having a thickness of 200 μs and the Mg-doped P-type GaN layer having a thickness of 70 μs were formed on the quantum well layer 15 at a temperature of 1010 ° C., respectively. ) Grow sequentially.

Subsequently, Mg-doped P-type Al _0.05 Ga _0.95 N layer 18 having a thickness of 4000Å and Mg doped P having a thickness of 4000Å were respectively formed at a temperature of 1010 ° C. using the same method as in the previous step to form a clad layer and an optical guide layer. The GaN layer 19 is formed by growing sequentially.

At this time, the P-type GaN layer 19 is grown to have a doping concentration of 3 × 10 ¹⁸ cm ⁻³ or more in order to form a good P-type ohmic contact electrode formed thereafter.

Then, the substrate 10 was wrapped to have a thickness of about 100 μm, and then the Ti / Al / Ni / Au layer 20, which is an n-type ohmic contact electrode, was deposited by e-beam under a heat treatment temperature of 700 ° C. for 30 seconds. It is formed to have a thickness of 100 to 300 mW / 2000 mW / 500 mW / 1000 mW, and Cr / Ni / Au layer 21, which is a P-type ohmic contact electrode, is formed on the P-type GaN layer 19 at 30 ° C. under a heat treatment temperature at 500 ° C. for 30 seconds. Deposition by beam to form a thickness of 300Å / 500Å / 2000Å respectively.

As described above, after the formation of the n and P electrodes is cleaved toward the a surface 1120 to produce a chip.

The n-type In _0.05 Ga _0.95 N layer 12 of silicon doping formed in the above process is for preventing the crack of the n-type Al _0.05 Ga _0.95 N layer 13, which is an n-type clad layer, and n-type Al _0.05 Ga _0.95 N The layer 13 and the P-type Al _0.05 Ga _0.95 N layer 18 are for confining light emitted from the active layer formed of the quantum well layer 15 and the n-type GaN layer 14 and the P-type GaN layer 19 ) Is to guide light, and the P-type Al _0.2 Ga _0.8 N layer 16 is to increase the binding force of the injected electrons and to protect the interface of the InGaN quantum well layer 15 during growth.

As described above, the present invention can eliminate the crystal overlap coming between the lattice mismatch and the coefficient of thermal expansion by using an n ⁺ GaN substrate formed by growing by the vapor phase thin film growth method without using a conventional sapphire or spinal substrate. A thin film of a high quality GaN based compound semiconductor having a laser diode structure may be grown on the n ⁺ GaN substrate by organometallic chemical vapor deposition.

And since GaN substrate is not used, it is possible to directly grow n-type GaN without using GaxAll-xN (0≤x≤1) buffer layer that grows at low temperature, thus simplifying the process by eliminating buffer layer. Since the slope of the LD resonator can be easily cleaved. In other words, the cleavage is easily performed in the direction of the Q plane 1120 to achieve much higher quality and simplification of the process than the cleavage surface formed by the etching process used when the sapphire is used as the substrate, and the laser diode resonator cleaved surface formed using the a surface sapphire substrate. Much higher chip formation yields. In addition, since the conventional laser diode structure is a sapphire (or spinal) substrate which is an insulating substrate and is a planar structure, a separate photo and etching process is required when forming an n-type electrode, but the structure of the present invention is n-type on the back of the substrate. Since a vertical structure capable of directly forming an electrode is possible, there is no need for etching and a photo process therefor, thereby simplifying the process.

Claims (4)

Preparing an n ⁺ type GaN substrate grown by homogeneous thin film growth using a halogen vapor thin film growth method, and an n type In _x Ga _x N layer of n-type GaN etched doped with silicon on the n ⁺ type substrate (0 ≦ x≤1), and forming by sequentially growing an n-type Al _x Ga _x N layer and an n-type GaN layer, a plurality of barrier layers of ln _0.2 Ga _0.8 and ln _0.05 Ga _0.95 N layer on the n-type GaN layer Alternately growing to form an active layer having a multi-quantum well layer structure, and a P-type Al _x Ga _1-x N layer, a P-type GaN layer, and a P-type A1 _x Ga _lx N doped with Mg on the active layer, respectively; Forming a (0 ≦ x ≦ 1) layer and a P-type GaN layer, and forming an n-type ohmic contact electrode and a P-type ohmic contact electrode under the substrate and on the P-type GaN layer, respectively. Method for manufacturing laser diode. The method of claim 1, wherein the number of repetitions of the well layer and the barrier layer of the quantum well layer is alternately 3 to 5 times. N-type GaN layer, n-type In _x Ga _lx N layer (0≤x≤1), n-type Al formed by exposing silicon on n ⁺ type GaN substrate grown by homogeneous thin film growth using halogen vapor thin film growth method a multi-quantum well-type active layer in which a plurality of _x Ga _0.8 N layers and an n-type GaN layer and an ln _0.2 Ga _{0.8 well} and a barrier layer of ln _0.05 Ga _0.95 N are alternately stacked on the final n-type GaN layer; A P-type Al _x Al _1-x N layer, a P-type GaN layer, a P-type Al _x Ga _1-x N layer, and a P-type GaN layer each of which is sequentially grown and stacked on the active layer, and a lower portion of the substrate; And an n-type ohmic contact electrode and a P-type ohmic contact electrode respectively formed on the final P-type GaN layer. The blue laser diode of claim 3, wherein the active layer of the multi-quantum well structure is alternately stacked three to five times of the well layer and the barrier layer.