CN1306625C - Light-emitting diode structure and manufacturing method thereof - Google Patents

Abstract

The present invention provides a light emitting diode element and a manufacturing method thereof. A buffer layer is first grown on the surface of a substrate, and then a light emitting diode structure is grown on the buffer layer. The light emitting diode structure includes a p-type quantum dot epitaxial layer on a p-type gallium nitride layer. Since the p-type quantum dot epitaxial layer has a roughening and scattering effect, the light emitted from the light emitting layer formed by the InGaN multiple quantum well structure layer can change the path of travel and reduce the probability of total internal reflection. Therefore, the known roughening process can be effectively simplified and the light emitting efficiency can be improved.

Description

Light-emitting diode structure and manufacturing method thereof

technical field

The invention relates to a light-emitting diode element and a manufacturing method thereof, in particular to a light-emitting diode structure comprising a p-type quantum dot epitaxial layer on a p-type gallium nitride layer and a manufacturing method thereof.

Background technique

Due to the material of light-emitting diodes, the difference between the refractive index of III-V (III-V) gallium nitride (GaN) semiconductor (n=2.3) and air (n=1) is very large, so that the critical angle of total reflection is about Only 25 degrees, resulting in the light generated by the light-emitting layer, most of which can only be totally reflected inside and cannot escape. In order to change the shortcomings of this interface, in the known technology, someone proposes to roughen the surface of the semiconductor to make the light from After the luminous layer comes out, it passes through the interface of the roughening layer. Due to the scattering characteristics of the roughened layer interface, the path of light is changed, so that even though there is still a probability of total reflection, the probability of light divergence increases. , 2000). The roughening method of the known technology is mainly achieved by etching the epitaxial surface, such as in US Patent No. 5,040,044, which discloses the use of chemical etching to roughen the surface of the light-emitting element, so as to achieve the effect of increasing the luminous efficiency. Other relevant materials include US Patent Nos. 5,429,954 and 5,898,192, etc. However, the method of processing through the above-mentioned manufacturing process is only applied to red light-emitting diodes, which is mainly based on its material processing characteristics are relatively easy. However, it is not suitable for gallium nitride series materials, because gallium nitride series materials do not have strong acid and alkali resistance, and are not easy to control during wet etching. Although dry etching can overcome the aforementioned wet etching problem, it is easy to cause damage to the epitaxial layer. In particular, the p-type gallium nitride layer (p-GaN) is very easy to cause an increase in resistance, which affects current distribution and degrades luminous efficiency. Moreover, the p-type gallium nitride layer is usually deposited in a very thin thickness (0.1-0.3 μm). If the p-type gallium nitride layer is directly roughened, the light-emitting layer may be damaged, resulting in the disadvantage of reducing the light-emitting area. In addition, the transparent electrodes generally applied to GaN light-emitting diodes must maintain a very thin thickness (10nm) for good light transmission. During the roughing process, it will be damaged and cause the discontinuity of the transparent electrode, which will also adversely affect the current distribution and reduce the luminous efficiency. Therefore, unless the p-type gallium nitride layer can be deposited thick enough, it is possible to perform dry etching, but too thick p-type gallium nitride layer will disperse the current and reduce the luminous efficiency. The solution of p-type gallium nitride layer appears to be difficult to implement.

Contents of the invention

In view of the above problems, the present invention proposes to use epitaxy to achieve the effect of roughening, so as to improve the luminous efficiency of gallium nitride series light-emitting elements. The present invention discloses a method for roughening gallium nitride layer light-emitting elements, which is different from known Compared with other technologies, the present invention can obtain significantly improved luminous efficiency.

The main purpose of the present invention is: in the epitaxially grown light-emitting diode structure, grow a p-type quantum dot epitaxial layer on the surface of the p-type gallium nitride layer, and use the p-type quantum dot epitaxial layer of the gallium nitride series to have a coarse The characteristics of the roughened scattering effect can effectively simplify the known roughening process for making the light-emitting diode structure have a good roughened scattering effect.

Another object of the present invention is: by means of the p-type quantum dot epitaxial layer, the light emitted by the light-emitting layer formed by the indium gallium nitride (InGaN) multiple quantum well structure layer can be reduced due to the p-type quantum dot epitaxial layer. Coarse the scattering effect to change the path of light, reduce the probability of internal total reflection, and improve luminous efficiency.

Content of the present invention is as follows:

The first content of the present invention is a light emitting diode structure provided with a substrate, which is characterized in that the structure comprises:

A buffer layer on the substrate, the material of the buffer layer is gallium nitride (GaN) series compounds;

A light-emitting diode structure layer on the surface of the buffer layer, the light-emitting diode structure layer is composed of an n-type gallium nitride layer, a multiple quantum well structure layer, a p-type aluminum gallium nitride layer and a p-type gallium nitride layer,

Wherein, the n-type gallium nitride layer is on the buffer layer, and the material of the n-type gallium nitride layer is a gallium nitride series III-V compound,

The multiple quantum well structure layer is on the n-type gallium nitride layer, and the material of the multiple quantum well structure layer is an indium gallium nitride series compound,

The p-type aluminum gallium nitride layer is on the multiple quantum well structure layer, and the material of the p-type aluminum gallium nitride layer is a p-type aluminum gallium nitride series III-V compound,

The p-type gallium nitride layer is on the p-type aluminum gallium nitride layer, and the material of the p-type gallium nitride layer is a p-type gallium nitride series III-V compound;

The p-type quantum dot epitaxial layer on the p-type gallium nitride layer of the light-emitting diode structure layer, the material of the p-type quantum dot epitaxial layer is aluminum indium gallium nitride series compounds, wherein the light-emitting diode structure layer The n-type gallium nitride layer, the multiple quantum well structure layer, the p-type aluminum gallium nitride layer, the p-type gallium nitride layer and the p-type quantum dot epitaxial layer are partially removed by the etching process remove;

A p-type ohmic contact electrode electrically connected on the p-type quantum dot epitaxial layer, the material of the p-type ohmic contact electrode is nickel/gold metal; and

The n-type ohmic contact electrode on the n-type gallium nitride layer of the light-emitting diode structure layer and electrically connected, the material of the n-type ohmic contact electrode is titanium/aluminum metal; thereby a positive electrode can be arranged on the light-emitting diode structure to the bias.

The second content of the present invention is a method for manufacturing a light-emitting diode, which is characterized in that it includes the following steps:

Set up the substrate;

growing a buffer layer on the surface of the substrate;

growing a light emitting diode structure layer on the surface of the buffer layer, the light emitting diode structure layer is composed of an n-type gallium nitride layer, a multiple quantum well structure layer, a p-type aluminum gallium nitride layer and a p-type gallium nitride layer;

On the surface of the p-type gallium nitride layer of the light-emitting diode structure layer, a p-type quantum dot epitaxial layer is grown, and the p-type quantum dot epitaxial layer is electrically connected to a p-type ohmic contact electrode, and the p-type ohmic contact electrode The material is nickel/gold (Ni/Au) metal, the n-type gallium nitride layer is electrically connected to the n-type ohmic contact electrode, and the material of the n-type ohmic contact electrode is titanium/aluminum (Ti/Al) metal, thereby being able to Set a positive bias voltage.

The third content of the present invention is that, in the manufacturing method of the light-emitting diode element described in the second item, the p-type quantum dot epitaxial layer is aluminum indium gallium nitride (Al _x Ga _(1-xy) In _v N ) film, 0≤x, y<1, 0≤x+y<1.

The content of the fourth item of the present invention is that in the manufacturing method of the light-emitting diode element described in the second item, the substrate is sapphire (Sapphire), silicon carbide (SiC), silicon (Si), gallium arsenide (GaAs) , one of lithium metaaluminate (LiAlO ₂ ), lithium gallate (LiGaO ₂ ) and aluminum nitride (AlN) substrates.

According to the fifth item of the present invention, in the manufacturing method of the light-emitting diode element described in the second item, the thickness of the p-type quantum dot epitaxial layer is greater than 10 Angstroms (A).

The content of the sixth item of the present invention is that, in the manufacturing method of the light-emitting diode element described in the second item, the average roughness of the p-type quantum dot epitaxial layer is greater than 10 Angstroms (A).

Description of drawings

Fig. 1 is a schematic structural diagram of a light emitting diode according to an embodiment of the present invention.

Fig. 2 is a flowchart of a method for manufacturing a light emitting diode according to an embodiment of the present invention. in the picture

101 Substrate 102 Buffer layer

103 light-emitting diode structure layer 1030 n-type gallium nitride layer

1032 multiple quantum well structure layer 1034 p-type aluminum gallium nitride layer

1036 p-type gallium nitride layer 107 p-type quantum dot epitaxial layer

108 p-type ohmic contact electrode 109 n-type ohmic contact electrode

201 Growth buffer layer 203 Growth light-emitting diode structure layer

205 Growing quantum dot epitaxial layer 207 Forming electrodes

Detailed ways

In order to make the objects and advantages of the present invention more obvious, specific embodiments are described in detail below and illustrated in conjunction with the accompanying drawings.

Fig. 1 is a schematic structural diagram of a light emitting diode according to an embodiment of the present invention. The sapphire (sapphire) substrate 101 is placed in a metal organic chemical vapor deposition (MOCVD) system, and the substrate 101 can also be silicon carbide (SiC), silicon (Si), arsenic One of gallium (GaAs), lithium metaaluminate (LiAlO ₂ ), lithium gallate (LiGaO ₂ ), and aluminum nitride (AlN).

First, grow a gallium nitride (GaN) buffer layer (buffer layer) 102 with a thickness of 20-50 nanometers (nm) at 500-600°C, and then grow a light-emitting diode structure layer 103 on the surface of the buffer layer 102, the light-emitting diode The structural layer 103 includes an n-type gallium nitride layer 1030, a multiple quantum well structure layer 1032, a p-type aluminum gallium nitride layer 1034 and a p-type gallium nitride layer 1036, wherein the n-type gallium nitride layer 1030 is on the buffer layer 102 Above, the material of the n-type gallium nitride layer 1030 is a gallium nitride series III-V compound.

Raise the substrate temperature to 1000-200°C, grow a 1-2 micron (μm) thick layer of n-type gallium nitride (n-type GaN) 1030 doped with silicon (Si) impurities, n-type gallium nitride The material of layer 1030 is a gallium nitride series III-V group compound. Afterwards, the test piece is taken out and placed in metal-organic chemical vapor deposition (MOCVD), and the temperature of the substrate 101 is raised to 700°C-900°C to grow nitrogen The indium gallium nitride (InGaN) multiple quantum well structure layer 1032 is used as the light-emitting layer, followed by a magnesium-doped (Mg doped) p-type aluminum gallium nitride layer 1034, and then a magnesium-doped p-type aluminum gallium nitride layer is grown. Gallium layer 1036, and finally a layer of magnesium-doped p-type quantum dot epitaxial layer 107 is grown. The material of p-type quantum dot epitaxial layer 107 is aluminum indium gallium nitride series compound, and the average roughness is greater than 10 angstroms (A). , is a layer of aluminum indium gallium nitride (Al _x Ga _(1-xy) In _v N) thin film, 0≤x, y<1, 0≤x+y<1. In this way, the light-emitting diode epitaxial wafer is fabricated.

The epiwafer is dry-etched by inductively coupled plasma-reactive ion etching (ICP-RIE) procedure, and part of the p-type quantum dot epitaxial layer 107, p-type gallium nitride The layer 1036, the p-type AlGaN layer 1034, and the InGaN multiple quantum well structure layer 1032 are removed, and the surface of the n-type GaN layer 1030 is exposed. Then nickel/gold (Ni/Au) metal is fabricated on the surface of the p-type quantum dot epitaxial layer 107 and electrically connected to serve as the p-type ohmic contact electrode 108 . Titanium/aluminum (Ti/Al) metal is fabricated on the surface of the n-type GaN layer 103 and electrically connected to serve as the n-type ohmic contact electrode 109 . In this way, a forward bias voltage can be set, and the grain structure of the present invention is completed according to the above steps.

Fig. 2 is a flowchart of a method for manufacturing a light emitting diode according to an embodiment of the present invention. First grow the buffer layer in step 201: place the sapphire (sapphire) substrate 101 in a metal-organic chemical vapor deposition (MOCVD) system, and grow a layer of 20-50 nanometer (nm) thick nitride at 500-600°C. Gallium (GaN) buffer layer (buffer layer) 102 .

Next, in step 203, grow the light-emitting diode structure layer 103: raise the temperature of the substrate 101 to 1000-1200° C. to grow a 1-2 micron (μm) thick n-type gallium nitride layer doped with silicon (Si) impurities (n-type GaN) 1030, then take out the test piece, put it into metal organic chemical vapor deposition (MOCVD), and raise the substrate temperature to 700 ℃ ~ 900 ℃, grow indium gallium nitride (InGaN) multiple quantum The well structure layer 1032 is used as a light-emitting layer, followed by growing a magnesium-doped p-type AlGaN layer 1034 , and then growing a magnesium-doped p-type GaN layer 1036 .

Finally, in step 205 , a magnesium-doped p-type quantum dot epitaxial layer 107 is grown on the p-type GaN layer 1036 , thus completing the fabrication of the LED epitaxial wafer.

In step 207, the electrodes 108 and 109 are formed: the epiwafer is partially etched with p-type quantum dots using an inductively coupled plasma-reactive ionetching (ICP-RIE) program of dry etching. Crystal layer 107, p-type gallium nitride layer 1036, p-type aluminum gallium nitride layer 1034, indium gallium nitride (InGaN) multiple quantum well structure layer 1032 are removed, and the surface of n-type gallium nitride layer 1030 is exposed, and nickel Gold/gold (Ni/Au) metal is made on the surface of p-type quantum dot epitaxial layer 107 as p-type ohmic contact electrode 108, and titanium/aluminum (Ti/Al) metal is made on the surface of n-type gallium nitride layer 1030 as The n-type ohmic contact electrode 109 is fabricated according to the above steps to complete the grain structure of the present invention.

Although the present invention is disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art should be able to make various changes and improvements without departing from the spirit and scope of the present invention, but the various changes and improvements they make still do not depart from the scope of protection claimed by the application of the present invention.

Claims (6)

1. A light-emitting diode structure, which is provided with a substrate, is characterized in that the structure comprises: A buffer layer on the substrate, the material of the buffer layer is gallium nitride (GaN) series compounds; A light-emitting diode structure layer on the surface of the buffer layer, the light-emitting diode structure layer is composed of an n-type gallium nitride layer, a multiple quantum well structure layer, a p-type aluminum gallium nitride layer and a p-type gallium nitride layer, Wherein, the n-type gallium nitride layer is on the buffer layer, and the material of the n-type gallium nitride layer is a gallium nitride series III-V compound, The multiple quantum well structure layer is on the n-type gallium nitride layer, and the material of the multiple quantum well structure layer is an indium gallium nitride series compound, The p-type aluminum gallium nitride layer is on the multiple quantum well structure layer, and the material of the p-type aluminum gallium nitride layer is a p-type aluminum gallium nitride series III-V compound, The p-type gallium nitride layer is on the p-type aluminum gallium nitride layer, and the material of the p-type gallium nitride layer is a p-type gallium nitride series III-V compound; The p-type quantum dot epitaxial layer on the p-type gallium nitride layer of the light-emitting diode structure layer, the material of the p-type quantum dot epitaxial layer is aluminum indium gallium nitride series compounds, wherein the light-emitting diode structure layer The n-type gallium nitride layer, the multiple quantum well structure layer, the p-type aluminum gallium nitride layer, the p-type gallium nitride layer and the p-type quantum dot epitaxial layer are partially removed by the etching process remove; A p-type ohmic contact electrode electrically connected on the p-type quantum dot epitaxial layer, the material of the p-type ohmic contact electrode is nickel/gold metal; and The n-type ohmic contact electrode on the n-type gallium nitride layer of the light-emitting diode structure layer and electrically connected, the material of the n-type ohmic contact electrode is titanium/aluminum metal; thereby a positive electrode can be arranged on the light-emitting diode structure to the bias. 2. A method for manufacturing a light-emitting diode, comprising the following steps: Set up the substrate; growing a buffer layer on the surface of the substrate; growing a light emitting diode structure layer on the surface of the buffer layer, the light emitting diode structure layer is composed of an n-type gallium nitride layer, a multiple quantum well structure layer, a p-type aluminum gallium nitride layer and a p-type gallium nitride layer; On the surface of the p-type gallium nitride layer of the light-emitting diode structure layer, a p-type quantum dot epitaxial layer is grown, and the p-type quantum dot epitaxial layer is electrically connected to a p-type ohmic contact electrode, and the p-type ohmic contact electrode The material is nickel/gold (Ni/Au) metal, the n-type gallium nitride layer is electrically connected to the n-type ohmic contact electrode, and the material of the n-type ohmic contact electrode is titanium/aluminum (Ti/Al) metal, thereby being able to Sets a forward bias voltage. 3. The method for manufacturing a light-emitting diode element according to claim 2, wherein the p-type quantum dot epitaxial layer is an aluminum indium gallium nitride (Al _x Ga _(1-xy) In _v N) film, 0 ≤x, y<1, 0≤x+y<1. 4. The method of manufacturing a light-emitting diode element according to claim 2, wherein the substrate is sapphire (Sapphire), silicon carbide (SiC), silicon (Si), gallium arsenide (GaAs), metaaluminate One of lithium (LiAlO ₂ ), lithium gallate (LiGaO ₂ ) and aluminum nitride (AlN) substrates. 5 . The method for manufacturing a light emitting diode element according to claim 2 , wherein the thickness of the p-type quantum dot epitaxial layer is greater than 10 angstroms (A). 6 . The method for manufacturing a light emitting diode element according to claim 2 , wherein the average roughness of the p-type quantum dot epitaxial layer is greater than 10 angstroms (A).