CN102185056A - Gallium-nitride-based light emitting diode capable of improving electron injection efficiency - Google Patents

Abstract

A gallium nitride-based light-emitting diode for improving electron injection efficiency, comprising: a substrate; a gallium nitride nucleation layer fabricated on the substrate; a buffer layer fabricated on the gallium nitride nucleation layer; an n-type The contact layer is made on the buffer layer, and a table is formed on the upper side of the n-type contact layer; the next multi-period n-type electronic coupling layer is made on the other side of the upper table of the n-type contact layer; the first tunnel barrier layer is made on the lower multi-period n-type electron coupling layer; an upper multi-period n-type electron coupling layer is made on the lower tunneling barrier layer; an upper tunneling barrier layer is made on the upper multi-period n-type electron coupling layer; The multi-period active luminescent layer is fabricated on the upper tunneling barrier layer; a negative electrode is fabricated on the mesa of the n-type contact layer; a p-type electron blocking layer is fabricated on the multi-period active luminescent layer; a p-type contact layer is fabricated on the On the p-type electron blocking layer; a positive electrode is made on the p-type contact layer to form the structure of gallium nitride light emitting diode.

Description

GaN-based light-emitting diodes with improved electron injection efficiency

technical field

The invention relates to a gallium nitride (GaN) light-emitting diode, in particular to a gallium nitride light-emitting diode with two or more n-type electron coupling layers of different indium components.

Background technique

At present, III-V semiconductor optoelectronic materials are known as the third generation semiconductor materials. GaN-based light-emitting diodes have become the focus of industry research because they can produce light-emitting diodes (referred to as "LEDs") of various colors (especially blue or violet light that requires a high energy gap) by controlling the composition of materials.

The epitaxial growth of GaN-based semiconductor materials or devices currently mainly adopts MOCVD technology. In the process of growing nitride semiconductors (GaN, AlN, InN and their alloy nitrides) using MOCVD technology, sapphire is usually used as the substrate for heteroepitaxy because there is no substrate material that matches the GaN lattice. However, there is a large lattice mismatch (-13.8%) and a difference in thermal expansion coefficient between sapphire and nitride semiconductors, so it is very difficult to grow high-quality nitride semiconductors with no cracks and flat surfaces. Currently the most effective epitaxial growth method usually adopts a two-step epitaxial growth method (see H.Amano, N.Sawaki and Y.Toyoda et al., "Metal Organic Vapor Phase Epitaxy Growth of High Quality GaN Thin Film Using AlN Buffer Layer", Appl.Phys . Lett.48, 1986, 353), although the crystal quality has been improved to a certain extent, there is a lot of stress in the epitaxial layer due to the lattice mismatch between sapphire and nitride. At the same time, there is also a large thermal mismatch between InGaN and GaN in the active light-emitting layer, that is, when the temperature changes, a certain strain will also be generated in the active layer. Due to the compressive strain properties of III-nitrides, these strains can generate large compressive stresses in the active regions of InGaN/GaN MQWs. Thus, a large compressive strain electric field (ie, piezoelectric field effect (piezo-electrical field effect)) is formed in the multi-quantum well active region, and the existence of the piezoelectric field effect makes the wave functions of electrons and holes in the space On the other hand, due to the existence of the piezoelectric field, the Fermi level of the n-region of the LED is raised, even higher than the Fermi level of the p-region (Appl.Phys.Lett., 94, 2009, 231123), resulting in non-radiative recombination of electrons from the n region across the active region directly to the p region. In order to reduce the overshoot of electrons, the early method is to grow a thick InGaN insertion layer with low indium composition as the electron storage layer in front of the active light-emitting layer, but because the quality of the InGaN layer increases rapidly with the thickness In subsequent studies, this layer of InGaN was replaced by a quantum well or superlattice structure of InGaN and GaN (see patent CN1552104A and patent CN101174662A). These two structures play a very good role in reducing the overshoot of electrons and increasing the injection efficiency of electrons under the condition of small current injection. However, with the increase of the injected current density, since the applied electric field is in the same direction as the compressive strain electric field in the active layer, the Fermi energy level of the n-region is further increased, and the overshoot behavior of electrons is aggravated, and a large number of electrons still cross the active layer. directly to the p zone.

In order to reduce the overshoot behavior of electrons under high current injection conditions and improve the injection efficiency of electrons, we add two or more groups of indium gallium nitrogen and aluminum indium gallium nitrogen with different indium components under the active layer of the active region. The multi-quantum well structure is used as the electron coupling layer. The indium composition in each group of quantum well structures is different, and the closer to the active light-emitting layer, the higher the indium composition in the indium gallium nitride. With the increase of the indium composition, the confinement effect of the indium gallium nitrogen quantum well on electrons is enhanced, and more electrons will be bound inside the electron coupling layer, so as to reduce the overshoot of electrons. A thin AlInGaN layer is used as a tunneling barrier layer between the electron coupling layers. Adjust the energy level in the quantum well by adjusting the width of the indium gallium nitrogen quantum well layer in each electron coupling layer, and finally achieve the energy level resonance of electrons between different coupling layers and between the coupling layer and the active light-emitting layer; by adjusting The thickness of the AlInGaN tunneling barrier layer improves the tunneling probability of electrons between resonance energy levels.

Contents of the invention

The purpose of the present invention is to provide a gallium nitride-based light-emitting diode. Through this structural design, the limitation of electrons under high current injection can be increased, the overshoot of electrons can be reduced, and the injection efficiency of electrons can be improved, thereby improving the light emission of the light-emitting diode. efficiency.

The invention provides a gallium nitride-based light-emitting diode with improved electron injection efficiency, which includes:

a substrate;

a gallium nitride nucleation layer, the gallium nitride nucleation layer is fabricated on the substrate;

a buffer layer fabricated on the gallium nitride nucleation layer;

An n-type contact layer, the n-type contact layer is fabricated on the buffer layer, and a mesa is formed on the upper side of the n-type contact layer, and the n-type contact layer is composed of n-type gallium nitride;

A multi-period n-type electronic coupling layer, the lower multi-period n-type electronic coupling layer is fabricated on the other side of the upper mesa of the n-type contact layer;

A lower tunneling barrier layer, which is fabricated on the lower multi-period n-type electron coupling layer;

An upper multi-period n-type electron coupling layer, the upper multi-period n-type electron coupling layer is fabricated on the lower tunneling barrier layer;

An upper tunneling barrier layer, the upper tunneling barrier layer is fabricated on the upper multi-period n-type electron coupling layer;

A multi-period active light-emitting layer, the active light-emitting layer is fabricated on the upper tunneling barrier layer;

a negative electrode, which is fabricated on the mesa of the n-type contact layer;

A p-type electron blocking layer, the p-type electron blocking layer is fabricated on the multi-period active light-emitting layer;

A p-type contact layer, the p-type contact layer is fabricated on the p-type electron blocking layer, and the p-type contact layer is composed of p-type gallium nitride;

A positive electrode is fabricated on the p-type contact layer to form a gallium nitride light emitting diode structure.

Description of drawings

In order to further illustrate the technical content of the present invention, the present invention will be described in more detail below in conjunction with the accompanying drawings and specific embodiments, wherein:

FIG. 1 is a GaN-based light emitting diode having an n-type electron coupling layer according to the present invention.

Fig. 2 is the PL luminous intensity curve of the existing GaN-based light-emitting diodes and according to the present invention, wherein the triangular line is the GaN-based LED with n-type electronic coupling layer structure of the present invention; the circular line is the traditional structure GaN-based LEDs.

Detailed ways

Please refer to FIG. 1, the present invention provides a gallium nitride-based light-emitting diode, which includes:

A substrate 11, with (0001) sapphire (Al ₂ O ₃ ) as the substrate 11, other materials that can be used for the substrate 11 include R-plane or A-plane alumina single crystal, 6H-SiC, 4H -SiC, or a single crystal oxide having a lattice constant close to that of a nitride semiconductor. In the preparation, high-purity _NH3 is used as N source, the mixed gas of high-purity _H2 and _N2 is used as carrier gas; trimethylgallium or triethylgallium is used as Ga source, trimethylindium is used as In source, trimethylaluminum As an Al source; the n-type dopant is silane, and the p-type dopant is magnesocene.

A gallium nitride nucleation layer 12 , the gallium nitride nucleation layer 12 is fabricated on the substrate 11 . Growth parameters include: reaction temperature 500°C to 800°C, reaction chamber pressure 200 to 500 Torr, carrier gas flow rate 10-30 L/min, trimethylgallium flow rate 20-250 micromol/min, ammonia gas flow rate 20-80 mol/min Minutes, growth time 1-10 minutes;

A buffer layer 13, the buffer layer 13 is fabricated on the nucleation layer 12. Growth parameters include: reaction temperature 950-1180°C, reaction chamber pressure 76-250 Torr, carrier gas flow 5-20 liters/min, trimethylgallium flow 80-400 micromol/min, ammonia flow 200-800 mol /min, growth time 20-60 minutes;

An n-type contact layer 14, the n-type contact layer 14 is fabricated on the buffer layer 13, and the n-type contact layer 14 is made of n-type gallium nitride. Growth parameters include: reaction temperature 950-1150°C, reaction chamber pressure 76-250 Torr, carrier gas flow 5-20 liters/min, trimethylgallium flow 80-400 micromol/min, ammonia flow 200-800 mol/min , the silane flow rate is 0.2-2.0 nmol/min, and the growth time is 10-40 minutes;

The lower multi-period n-type electron coupling layer 15 is formed on the other side of the mesa 141 on the n-type contact layer 14 . The lower multi-period electron coupling layer 15 is composed of a multi-period quantum well structure formed by alternating lamination of indium gallium nitride (InGaN) thin layers 151 and aluminum indium gallium nitride (AlInGaN) thin layers 152 . The growth parameters include: AlInGaN thin layer (ie barrier layer 152): reaction temperature 700-900°C, reaction chamber pressure 100-500Torr, carrier gas flow rate 5-20 liters/minute, ammonia gas flow rate 200-800 mol/minute, trimethyl The base indium flow rate is 10-50 micromol/min, the trimethylgallium flow rate is 0.1-1.0 micromol/min, the trimethylaluminum flow rate is 20-100 micromol/min, the silane flow rate is 0-2.0 nanomol/min, and the time is 0.1- 5 minutes; InGaN thin layer (i.e. well layer 151): reaction temperature 700-850°C, reaction chamber pressure 100-500 Torr, carrier gas flow 5-20 liters/minute, ammonia flow 200-800 mol/minute, trimethyl The gallium flow rate is 0.1-1.0 micromol/min, the trimethylindium flow rate is 10-50 micromol/min, and the time is 0.1-5 minutes; the number of structural periods is 3 to 20;

The lower tunneling barrier layer 16 is fabricated on the lower multi-period n-type electron coupling layer 15 and is composed of a thin layer of aluminum indium gallium nitride (AlInGaN). Its lower contact surface is the thin InGaN layer 151 of the lower multi-period n-type electron coupling layer 15 . Growth parameters include: reaction temperature 700-900°C, reaction chamber pressure 100-500 Torr, carrier gas flow 5-20 liters/min, ammonia flow 200-800 mol/min, trimethylindium flow 10-50 micromol/min , the flow rate of trimethylgallium is 0.1-1.0 micromol/min, the flow rate of trimethylaluminum is 20-100 micromol/min, the flow rate of silane is 0-2.0 nanomol/min, and the time is 0.1-5 minutes;

An upper multi-period n-type electron coupling layer 17, the upper multi-period n-type electron coupling layer 17 is made on the lower tunneling barrier layer 16, and the upper multi-period n-type electron coupling layer 17 is made of indium gallium nitride (InGaN) A multi-period quantum well structure is formed by stacking thin layers 171 and aluminum indium gallium nitride (AlInGaN) thin layers 172 alternately. The growth parameters include: AlInGaN thin layer (that is, barrier layer 172): reaction temperature 700-900°C, reaction chamber pressure 100-500Torr, carrier gas flow rate 5-20 liters/minute, ammonia flow rate 200-800 mol/minute, trimethyl The base indium flow rate is 10-50 micromol/min, the trimethylgallium flow rate is 0.1-1.0 micromol/min, the trimethylaluminum flow rate is 20-100 micromol/min, the silane flow rate is 0-2.0 nanomol/min, and the time is 0.1- 5 minutes; InGaN thin layer (i.e. well layer 171): reaction temperature 700-850°C, reaction chamber pressure 100-500Torr, carrier gas flow 5-20 liters/minute, ammonia flow 200-800 mol/minute, trimethyl The gallium flow rate is 0.1-1.0 micromol/min, the trimethylindium flow rate is 10-50 micromol/min, and the time is 0.1-5 minutes; the number of structural periods is 3 to 20;

An upper tunneling barrier layer 18, the upper tunneling barrier layer 18 is fabricated on the upper multi-period n-type electron coupling layer 17, and is composed of a thin layer of aluminum indium gallium nitride (AlInGaN). The lower contact surface is the thin InGaN layer 171 of the upper multi-period n-type electron coupling layer 17 . Growth parameters include: reaction temperature 700-900°C, reaction chamber pressure 100-500 Torr, carrier gas flow 5-20 liters/min, ammonia flow 200-800 mol/min, trimethylindium flow 10-50 micromol/min , the flow rate of trimethylgallium is 0.1-1.0 micromol/min, the flow rate of trimethylaluminum is 20-100 micromol/min, the flow rate of silane is 0-2.0 nanomol/min, and the time is 0.1-5 minutes;

An active luminescent layer 19, the active luminescent layer 19 is made on the upper tunneling barrier layer 18, the active luminescent layer 19 is composed of an indium gallium nitride (InGaN) thin layer 191 and an aluminum indium gallium nitride (AlInGaN) thin layer 192 A multi-period quantum well structure formed by alternate lamination. The growth parameters include: AlInGaN thin layer (ie barrier layer 192): reaction temperature 700-900°C, reaction chamber pressure 100-500Torr, carrier gas flow rate 5-20 liters/minute, ammonia gas flow rate 200-800 mol/minute, trimethyl The base indium flow rate is 10-50 micromol/min, the trimethylgallium flow rate is 0.1-1.0 micromol/min, the trimethylaluminum flow rate is 20-100 micromol/min, the silane flow rate is 0-2.0 nanomol/min, and the time is 0.1- 5 minutes; InGaN thin layer (i.e. well layer 191): reaction temperature 700-850°C, reaction chamber pressure 100-500Torr, carrier gas flow 5-20 liters/minute, ammonia flow 200-800 mol/minute, trimethyl The gallium flow rate is 0.1-1.0 micromol/min, the trimethylindium flow rate is 10-50 micromol/min, and the time is 0.1-5 minutes; the number of multiple quantum well cycles is 4 to 15;

The growth temperature of the thin InGaN layer 151 in the lower multi-period n-type electron coupling layer 15 in the present invention is preferably 600-900°C, which is lower than the growth temperature of the InGaN thin layer 171 in the upper multi-period n-type electron coupling layer 17 The growth temperature of the two InGaN thin layers 151 and 171 is lower than the growth temperature of the InGaN thin layer 191 in the active light emitting layer 19 .

The indium composition of the thin InGaN layer in the n-type electron coupling layer in the present invention should be 0<x<0.3. And from the thin InGaN layer 151 in the lower multi-period n-type electronic coupling layer 15 to the thin InGaN layer 171 in the upper multi-period n-type electronic coupling layer 17 to the thin InGaN layer 191 in the active light-emitting layer 19, its Indium composition is gradually increased.

The thickness of the AlInGaN tunneling barrier layer 16/18 in the present invention is preferably 2-20 nm.

In the present invention, a GaN-based light-emitting diode with greatly improved luminous intensity is obtained by growing multiple sets of n-type electron coupling layers 15/17 under the active light-emitting layer 19. The main reasons are as follows:

Multiple groups of electron coupling layers 15, 17 are grown under the active light-emitting layer 19, and the indium composition of the thin indium gallium nitrogen layer in the electron coupling layer is from the lower multi-period n-type electron coupling layer 15 to the upper multi-indium gallium nitrogen thin layer 15. From the thin InGaN layer 171 in the periodic n-type electron coupling layer 17 to the thin InGaN layer 191 in the active light-emitting layer 19, the indium composition gradually increases. Due to the higher indium composition in the electron coupling layer, the ability to bind electrons is enhanced, so that more electrons will be bound inside the electron coupling layer, reducing the overshoot of electrons under the condition of large current injection. By adjusting the indium composition and well width in the InGaN thin layers 151 and 171, the energy level resonance between the lower multi-period n-type electronic coupling layer 15 and the upper multi-period n-type electronic coupling layer 17 is realized, and finally the upper multi-period n-type electronic coupling layer 17 is realized. The energy level resonance between the periodic n-type electron coupling layer 17 and the thin InGaN layer 191 in the active light-emitting layer 19; by adjusting the thickness of the tunneling barrier layers AlInGaN layers 16 and 18, the lower multi-period n The energy level resonant tunneling between the n-type electron coupling layer 15 and the upper multi-period n-type electron coupling layer 17 and the active light-emitting layer 19. So as to achieve the purpose of improving the carrier injection efficiency.

A negative electrode 22, the negative electrode 22 is fabricated on the mesa 141 of the n-type contact layer 14, and is composed of chrome-platinum gold or titanium-aluminum-titanium gold.

A p-type electron blocking layer 20, the p-type electron blocking layer 20 is fabricated on the active light-emitting layer 19, and the p-type electron blocking layer 20 is made of AlInGaN. The thickness of the p-type electron blocking layer 20 is 10-50 nm, and the lower surface of the p-type electron blocking layer is in contact with the thin AlInGaN layer 192 in the active light emitting layer. Growth parameters include: reaction temperature 700-1000°C, reaction chamber pressure 50-200 Torr, carrier gas flow 5-20 liters/min, ammonia flow 100-400 mol/min, trimethylindium flow 10-50 micromol/min , the flow rate of trimethylaluminum is 20-100 micromol/min, the flow rate of trimethylgallium is 80-200 micromol/min, the flow rate of magnesiumocene is 150-400 nanomol/min, and the time is 1-10 minutes.

Wherein the p-type electron blocking layer 20 uses magnesocene as the p-type dopant, and the doping concentration of magnesocene is 10 ¹⁹ -10 ²¹ cm ^-3 .

A p-type contact layer 21, the p-type contact layer 21 is fabricated on the p-type electron blocking layer 20, the p-type contact layer 21 is composed of p-type gallium nitride. Growth parameters include: reaction temperature 950-1100°C, reaction chamber pressure 200-500 Torr, carrier gas flow 5-20 liters/min, ammonia flow 200-800 mol/min, trimethylgallium flow 80-400 micromol/min , The flow rate of magnesium dicene is 0.5-5 micromol/min, and the time is 10-50 minutes.

A positive electrode 23 is fabricated on the p-type contact layer 21 and is composed of chromium platinum. Completed the production of gallium nitride-based light-emitting diodes.

FIG. 2 shows a comparison of photoluminescence characteristics between a GaN-based light-emitting diode with an n-type electronic coupling layer according to the present invention and a GaN-based light-emitting diode without an n-type electronic coupling layer in a conventional process. The triangular lines are GaN-based LEDs with an n-type electronic coupling layer structure according to the present invention; the circular lines are GaN-based LEDs with a traditional structure. It can be seen from FIG. 2 that, compared with the LED with the traditional structure, under the same injection current condition, the luminous intensity of the LED structure of the present invention increases, indicating that the internal quantum efficiency of the light-emitting diode is effectively improved.

The above is only a specific implementation mode in the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technology can easily think of changes or replacements within the technical scope disclosed in the present invention. All should be covered within the scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (9)

1. GaN series LED that improves electron injection efficiency, it comprises:

One substrate;

One gallium nitride nucleating layer, this gallium nitride nucleating layer is produced on the substrate;

One resilient coating, this resilient coating are produced on the gallium nitride nucleating layer;

One n type contact layer, this n type contact layer is produced on the resilient coating, forms a table top in this side above n type contact layer, and this n type contact layer is made of n type gallium nitride;

Multicycle n type electronics coupled layer once, this following multicycle n type electronics coupled layer be produced on n type contact layer upper table surface opposite side above;

Tunneling barrier layer once, this time tunneling barrier layer is produced on n of the following multicycle type electronics coupled layer;

One n of last multicycle type electronics coupled layer, multicycle n type electronics coupled layer is produced on down on the tunneling barrier layer on this;

Tunneling barrier layer on one, tunneling barrier layer is produced on the multicycle n type electronics coupled layer on this;

Active luminescent layer of one multicycle, this activity luminescent layer is produced on the tunneling barrier layer;

One negative electrode, this negative electrode are produced on the table top of n type contact layer;

One p type electronic barrier layer, this p type electronic barrier layer are produced on the active luminescent layer of multicycle;

One p type contact layer, this p type contact layer is produced on the p type electronic barrier layer, and this p type contact layer is made of p type gallium nitride;

One positive electrode, this positive electrode are produced on the p type contact layer, form the structure of GaN series LED.

2. the GaN series LED of raising electron injection efficiency as claimed in claim 1, wherein each cycle of n of following multicycle type electronics coupled layer comprises:

One indium gallium nitrogen thin layer and the aluminium indium gallium nitrogen thin layer of making thereon, the top of this following multicycle n type electronics coupled layer makes one deck indium gallium nitrogen thin layer again.

3. the GaN series LED of raising electron injection efficiency as claimed in claim 1, each cycle of wherein going up multicycle n type electronics coupled layer comprises:

One indium gallium nitrogen thin layer and the aluminium indium gallium nitrogen thin layer of making thereon, the top of multicycle n type electronics coupled layer makes one deck indium gallium nitrogen thin layer again on this.

4. the GaN series LED of raising electron injection efficiency as claimed in claim 1, each cycle of wherein said active luminescent layer comprises:

One indium gallium nitrogen thin layer and the aluminium indium gallium nitrogen thin layer of making thereon, the top of this activity luminescent layer makes one deck indium gallium nitrogen thin layer again.

5. the GaN series LED of raising electron injection efficiency as claimed in claim 2, wherein the periodicity of n of following multicycle type electronics coupled layer is 3-20, the thickness of every layer of aluminum indium gallium nitrogen thin layer is 2-20nm; The thickness of each layer indium gallium nitrogen thin layer is 1-4nm.

6. the GaN series LED of raising electron injection efficiency as claimed in claim 3, the periodicity of wherein going up multicycle n type electronics coupled layer is 3-20, the thickness of every layer of aluminum indium gallium nitrogen thin layer is 2-20nm; The thickness of each layer indium gallium nitrogen thin layer is 1-4nm.

7. the GaN series LED of raising electron injection efficiency as claimed in claim 4, wherein the periodicity of active luminescent layer is 4-15, the thickness of every layer of aluminum indium gallium nitrogen thin layer is 4-20nm; The thickness of each layer indium gallium nitrogen thin layer is 1-4nm.

8. as the GaN series LED of claim 2 or 3 described raising electron injection efficiencies, wherein the indium component in n of following multicycle type electronics coupled layer and the last multicycle n type electronics coupled layer indium gallium nitrogen thin layer from bottom to up is increase gradually, but can not be above the indium component in the indium gallium nitrogen thin layer in the described active luminescent layer.

9. the GaN series LED of raising electron injection efficiency as claimed in claim 1, the thickness that wherein descends tunneling barrier layer and last tunneling barrier layer is 2-20nm.

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