KR19980059917A - Blue laser diode - Google Patents

Abstract

And a method of manufacturing the blue laser diode, wherein crystal bonds due to lattice matching and temperature expansion coefficient are eliminated by using an n-GaN substrate grown by a halogen vapor phase epitaxial growth (HVPE) method.

In order to accomplish the above object, the blue laser diode of the present invention includes: preparing an n ⁺ type GaN substrate grown by homogeneous thin film growth using a halogen vapor phase thin film growth method ^; GaN layer, an n-type In _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, Growing a well layer of In _0.2 Ga _0.8 and a barrier layer of In _0.05 Ga _0.95 N on the active layer to form an active layer of a multiple quantum well layer structure on the active layer, _x Ga _1-x n layer, P-type, GaN type, P-type Al _x Ga _1-x n layer, and forming a P-type GaN layer, the substrate bottom and type, each n in the upper part of the P-type GaN layer ohms And forming a contact electrode and a P-type ohmic contact electrode.

Description

Blue laser diode

The present invention relates to a light emitting device and a method of manufacturing the same, and more particularly, to a high-brightness, high-efficiency blue laser diode manufactured using a gallium nitride thin film obtained by homoepitaxy and a method of manufacturing the same.

As shown in FIG. 1, a conventional blue laser diode is formed by using an organometallic chemical vapor deposition method, and a gallium nitride (GaN) compound semiconductor such as Al _x Ga _1-x N and In _x Ga _1-x N layers (0 ≤ x ≤ 1).

GaN compound semiconductors grown in this manner have poor crystal quality due to lattice mismatch (13.8%) and thermal expansion coefficient difference (25%) between GaN and sapphire substrate, and crystal defects exist at about 10 ¹⁰ cm ^-2. It has been difficult to obtain a good P-type GaN compound semiconductor due to the bonding.

In order to form a resonator in a laser diode, the mirror surface must be present. However, a full roughness surface can not be obtained by using reactive ion etching (RIE) using a Cl ₂ gas plasma, and fine irregularities are generated The room temperature continuous oscillation of the blue laser diode can not be achieved because of the poor efficiency and the high threshold current.

In addition, as shown in FIG. 2, attempts have been made to increase lattice mismatch (9.5%) by using a spinel substrate ((III) MgAl ₂ O ₄ ) to increase the thin film crystal of the GaN compound semiconductor, However, there was a limit to improve the characteristics of the laser diode,

In order to obtain a cleaving surface for generating a mirror surface of a resonator, a GaN compound semiconductor is grown by a MOCVD method using an a-plane (1120) sapphire substrate as shown in FIG. 3, , It was very difficult to have a cleavage plane of a GaN compound semiconductor on a sapphire substrate having no cleavage plane.

Therefore, a sapphire or spinel substrate having a laser diode structure is lapped by as thin as possible (50 μm or less) to have a GaN-based wall interface. As described above, the thin film of the laser diode structure has a lattice mismatch with the substrate, The crystallinity is deteriorated due to a large difference in the expansion coefficient, so that a thin film having a large strain is formed. In the lapping, such crystal defects cause many cracks in the laser diode structure, resulting in a very poor chip production yield, Because of the crystallinity, the characteristics of the laser diode are not improved much more than those of the mirror surface formation by etching, and there are still many problems in continuous oscillation at room temperature for a long time.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the problems of the prior art described above, and it is an object of the present invention to provide an n ⁺ -GaN substrate grown by halogen vapor phase epitaxy (HVPE) A laser diode and a manufacturing method thereof.

1 is a view schematically showing a cross section of a conventional blue laser diode;

2 is a view schematically showing a cross section of a blue laser diode according to the present invention;

DESCRIPTION OF THE REFERENCE NUMERALS

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

12: n-type In _0.05 Ga _0.9 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 accomplish the above object, the blue laser diode of the present invention includes: preparing an n ⁺ type GaN substrate grown by homogeneous thin film growth using a halogen vapor phase thin film growth method ^; GaN layer, an In _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 in this order; _0.2 Ga _0.8 of well layers and in _0.05 Ga _0.95 N steps of a plurality of the barrier layer of the alternating layer was grown to form the active layer of multiple quantum well layer structure, in the active layer is Mg type respectively doped P Al _x Ga _{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; and the substrate bottom and type, each n in the upper part of the P-type GaN layer, ohmic contact electrode and the P-type to form a And forming a ohmic contact electrode.

According to another aspect of the present invention, there is provided a method of fabricating a blue laser diode, comprising: forming an n-type GaN substrate doped with silicon on an n ⁺ -type GaN substrate grown by a thin film growth method using halogen vapor phase epitaxy ^; type in _x Ga _1-x n layer (0≤x≤1), the n-type Al _x Ga _1-x n layer and the n-type GaN layer, and the end of the n-type in _0.2 Ga _0.8 in the GaN layer well layers and in A multi-quantum well active layer in which barrier layers of _0.05 Ga _0.95 N layers are alternately stacked a plurality of times, a p-type Al _x Ga _1-x N layer doped with Mg doped sequentially and grown on the active layer, a p-type GaN Layer, a P-type Al _x Ga ₁ -xN layer and a P-type GaN layer, and an n-type ohmic contact electrode and a P-type ohmic contact electrode respectively formed on the bottom of the substrate and on the final P-type GaN layer .

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

The blue laser diode of the present invention is a 300-350 탆 thick n ⁺ gallium nitride substrate 10 grown by homogeneous thin film growth using a halo growth method and then doped with a predetermined concentration of silicon, Doped n-type GaN layer formed on the n-type GaN layer 11, a 1000 Å thick In _0.05 Ga _0.95 N layer 12 doped with silicon and formed of a buffer layer on the n-type GaN layer 11, n-type in _0.05 Ga _0.95 n layer of silicon doped to be formed as n-type cladding layer on the (12) 4000Å conventional n-type Al _0.05 Ga _0.95 n layer 13, the n-type Al _0.05 Ga _0.95 n layer 13 Doped n-layer GaN layer 14 formed of a silicon-doped optical guide layer, a 50 Å thick barrier layer of In _0.05 Ga _0.95 N serving as an active layer, and a well layer of In _0.2 Ga _0.8 N of 30 Å thick A multi quantum well layer 15 having a stacked structure and a P-type Mg doping layer 20A formed on the multi-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 Doped P type Al _0.05 Ga _0.95 N layer 18 having a thickness of 4000 angstroms and a Mg doped P type GaN layer 19 having a thickness of 4000 angstroms formed as a co-guiding layer formed on the P type Al _0.05 Ga _0.95 N layer 18, And an n-type electrode 20 and a p-type electrode 21 respectively formed on the lower portion of the substrate N ⁺ -type GaN 10 and the upper portion of the P-type GaN layer 19 as the optical guide layer.

The N-type GaN (11) layer P-type GaN (19) layer formed on the substrate N ⁺ -type GaN (10) layer is formed by the same kind of metal organic chemical vapor deposition method as described later.

The multi-quantum well layer 15 has a structure in which a layer structure of In _0.05 Ga _0.95 having a thickness of 50 Å, which is a barrier layer, and In _0.2 Ga _0.8 N, a thickness of 30 Å, which is a well layer, is repeated 3 to 5 times.

According to the blue laser diode of the present invention having the above structure, the n ⁺ -type GaN layer 11 stacked on the n ⁺ GaN substrate 10 is much better than a conventional buffer layer formed on the sapphire substrate by the heteroepitaxial growth It is possible to solve the fundamental problem between the lattice uniaxial pressure and the temperature expansion coefficient.

A method of fabricating the blue laser diode of the present invention having the above-described structure will be described with reference to FIG.

First, an n ⁺ GaN substrate 10 having a thickness of 300 to 350 mu m is prepared, which is grown by homogeneous thin film growth using a halogen vapor phase thin film growth method and doped with silicon at a predetermined concentration.

On the n ⁺ GaN substrate 11, an n-type GaN layer 11 having a thickness of about 3 탆 and a thickness of about 3 탆 is formed on the n-type GaN layer 11 at a temperature of 1010 캜 using an MOCVD method.

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

Then, a silicon doped n-type In _0.05 Ga _0.95 N (12) is grown to a thickness of 1000 Å at a temperature of 800 ° C. in the same manner as the previous step so as to form a buffer layer on the n-type GaN layer 11. Then, in order to form an n-type cladding layer, an n-type Al _0.05 Ga _0.95 N layer 13 having a thickness of 4000 Å and a thickness of 4000 Å was formed on the n-type In _0.05 Ga _0.95 N layer 12 at the temperature of 1010 ° C. in the same manner as the previous step Grow. Next, in order to form both guide layers, a silicon-doped nGaN layer 14 is grown on the n-type Al _0.05 Ga _0.95 N layer 13 at a temperature of 1010 ° C and a thickness of 70 Å in the same manner as the previous step, to by the in _0.05 Ga _0.95 N layer and a well layer of in _0.05 Ga _0.95 N layer having a thickness of 30Å of the barrier layer having a thickness of 50Å at a temperature of 780 ℃ grown to 3 to 5 times alternately with a multiple quantum well layer 15 of the InGaN-based . A Mg-doped Al _0.05 Ga _0.8 N layer 16 having a thickness of 200 Å and a Mg-doped P-type GaN layer 17 having a thickness of 70 Å are formed on the quantum well layer 15 at a temperature of 1010 ° C., respectively, ) Are successively grown. In order to form the subsequent layer and the light guide layer, a Mg-doped Al _0.05 Ga _0.95 N layer 18 having a thickness of 4000 Å and a Mg-doped P layer having a thickness of 4000 Å were formed at a temperature of 1010 ° C., Type GaN layer 19 are successively grown.

At this time, the P-type GaN layer 19 is grown so as to have a doping concentration of 3 x 10 ¹⁸ cm ^-3 or more so as to form a P-type ohmic contact electrode to be formed thereafter.

Next, the substrate 10 was lapped to have a thickness of about 100 탆. The n-type ohmic contact electrode was formed by depositing the Ti / Al / Ni / Au layer 20 by e-beam under a heat treatment temperature of 700 캜 for 30 seconds Ni / Au layer 21, which is a P-type ohmic contact electrode, is formed on the P-type GaN layer 19 at a temperature of 500 ° C. for 30 seconds under a heat treatment temperature of about 100 to 300 Å / -beam to a thickness of 300 ANGSTROM / 500 ANGSTROM / 2000 ANGSTROM.

After the n and P electrodes are formed as described above, they are cleaved in the a-plane direction 1120 to fabricate chips.

The n-type In _0.05 Ga _0.95 N layer 12 formed in the above process is for preventing the n-type Al _0.05 Ga _0.95 N layer 13 which is the n-type cladding layer from cracking, and the 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 restricting the 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 for guiding light, and the P-type Al _0.2 Ga _0.8 N layer 16 enhances the confining force of injected electrons and protects the interface of the InGaN quantum well layer 15 during growth.

As described above, the present invention can eliminate the crystal intermixing between the lattice mismatching and the temperature expansion coefficient by using the n ⁺ GaN substrate formed by growing by the halogen vapor film growth method without using the conventional sapphire or sputtering substrate, A thin film of a high-quality GaN compound semiconductor having a laser diode structure can be grown on the n ⁺ GaN substrate by an organic metal chemical vapor deposition method.

Since the GaN substrate is not used, the n-type GaN layer can be grown immediately without using the buffer layer of GaxAll-XN (0? X? 1) which grows at a low temperature, so that the process can be simplified by eliminating the buffer layer. Since the substrate is used, the slope of the LD resonator can be easily cleaved. That is, the cleavage is easily performed in the direction of the Q-plane 1120, so that the quality and process can be simplified much more than the cleavage plane formed by the etching process used for the sapphire substrate, and the laser diode resonator cleavage plane formation using the a- The chip formation yield can be increased. In addition, since the conventional laser diode structure is a sapphire (or spinner) substrate, which is an insulating substrate, a separate photo and etching process is required for forming an n-type electrode because of a planar structure. However, Since the vertical structure capable of directly forming the electrodes is possible, there is an excellent effect such that the etching process and the photolithography process therefor are unnecessary, and the process is simplified.

Claims (4)

Of the halogen vapor phase thin film growth method using a homogeneous thin films grown n ⁺ type comprising: preparing a GaN substrate and the n ⁺ type substrate over the etched silicon-doped n-type GaN with, n-type In _x Ga _x N layer (0≤ x≤1), n-type Al _x Ga _x n layer and the n-type GaN layer grown by the sequential plurality of the barrier and the stage, in _0.2 Ga _0.8 of well layers and in _0.05 Ga _0.95 n layer on the n-type GaN layer to form And forming an active layer of a multiple quantum well layer structure by growing a p-type Al _x Ga _1-x N layer, a p-type GaN p-type Al _x Ga _{1- x} N (0? _x ? 0) layer and a P-type GaN layer, and forming an n-type ohmic contact electrode and a P-type ohmic contact electrode on the bottom of the substrate and the P-type GaN layer, respectively Method of manufacturing a blue laser diode. The method of manufacturing a blue laser diode according to claim 1, wherein the well layer and the barrier layer of the quantum well layer are alternately repeated three to five times. An n-type In _x Ga _{1 -x} N layer (0 _{? X?} 1), an n _- type GaN layer formed by exposing silicon on an n ⁺ -type GaN substrate grown by homogeneous thin film growth using a halogen vapor- Type Al _x Ga _0.8 N layer and an n-type GaN layer, a well layer of In _0.2 Ga _0.8 on the final n-type GaN layer, and a barrier layer of In _0.05 Ga _0.95 N are alternately stacked a plurality of times, A P-type Al _x Al ₁ -xN layer, a P-type, a GaN-type, a P-type Al _x Ga ₁ -xN layer and a P-type GaN layer, which are successively grown on the active layer and stacked and laminated, And an n-type ohmic contact electrode and a p-type ohmic contact electrode respectively formed on the bottom and the top of the P-type GaN layer. The blue laser diode according to claim 3, wherein the active layer of the multiple quantum well structure is alternately laminated three to five times of a well layer and a barrier layer.