JPH10256601A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the luminous efficiency and luminous characteristic by implanting impurities into a quantum well LED active region intentionally, and moreover adding intentionally similar impurities to be found in adjoining layers. SOLUTION: A thin GaN nucleus creating layer 14 is caused to grow on a sapphire substrate 12. A thick GaN layer 16 into which Si has been doped is caused to grow on the thin GaN nucleus creating layer 14. A first confinement layer 18 to be composed of GaN and Mg is caused to grow on the n-type GaN layer 16. A thin Inx Ga1-x NQW active region 20 is caused to grow on the first confinement layer 18. The thin QW active region is doped by arbitrary selection. A second confinement layer 22 composed of a GaN-based compound is arranged on the thin QW active region 20. The first and second confinement layers are doped independently or in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of a semiconductor light emitting device. In particular, the invention relates to GaN
The purpose is to improve the light emission characteristics of the system light emitting element.

[0002]

2. _{Description of the Related} Art Al _x Ga _{1 -x} As and _In.5 (Al _x G
a _1-X ) The red, orange, and yellow spectral regions by using a P material system and a double heterostructure with a “bulk” active region in the thickness range of 0.1-5.0 μm. , A highly efficient visible light emitting device (LED) has been produced. These extremely efficient LEDs
Generates light of the appropriate wavelength using direct interband transitions.

[0003] The latest extremely efficient blue LE commercialized by Nichia Corporation and Toyoda Gosei Co., Ltd.
D uses the AlInGaN material system in conjunction with a 0.05-0.10 μm thick “bulk” active region that is both “co-doped” with silicon and zinc. Co-doping has two distinct effects. First, the extremely high defect density associated with epitaxial GaN results in inefficient band-to-band transitions in undoped (undoped) materials, but the Zn-Si pair provides a very efficient emission mechanism. Second, Z
When the n-Si pair is selected, the inter-band and
With respect to light emission from the center of the Zn-Si impurity, the wavelength is 3
There is a significant shift from 80 nm to 450 nm. Only by this wavelength shift, the detection efficiency of the human eye increases almost 1000 times. Such an LED structure is acceptable for the blue spectral region, but by increasing the mole fraction of indium in the active region (x in the formula In _x Ga ₁ -xN) to shift the wavelength to the green spectral region. When trying to shift, the result is that the color purity of the LED is degraded,
It becomes a "white" color. There is a great commercial need for highly efficient, spectrally pure green and blue LEDs.

[0004] An extremely thin quantum well (Q
Extremely efficient blue and green LEDs using the same AlInGaN material system in connection with W) have been commercialized.
These devices use undoped QW regions and direct interband transitions to achieve more efficient and purer colors.
Utilizing special processes and techniques, incorporation and diffusion of dopants has been eliminated.

[0005]

SUMMARY OF THE INVENTION The present invention realizes an LED having a higher luminous efficiency and a longer luminous wavelength than conventional LEDs due to intentional doping and improved luminous characteristics.

[0006]

SUMMARY OF THE INVENTION In order to increase the efficiency of an LED, increase the emission wavelength and obtain an LED with improved characteristics over the emission characteristics of an LED with undoped QW, a quantum well (QW) LED active region is intentionally provided. Is introduced into the substrate.
In addition, the deliberate addition of impurities similar to those found in adjacent layers can reduce uncontrollable or undesirable effects of impurity diffusion.

[0007] A thin GaN nucleation layer is grown on a sapphire substrate. The GaN layer doped with thick Si
It is grown on a thin GaN nucleation layer. GaN: M
The first confinement layer made of n-type Ga
Grow on the N layer. A thin In _x Ga ₁ -x NQW active region is grown on the first confinement layer. The thin QW active region is optionally doped. A second confinement layer composed of a GaN-based compound is disposed over the thin QW active region. The first and second confinement layers are doped alone or in combination.

[0008]

FIG. 1 shows a preferred embodiment of a light emitting device 10. A GaN nucleation layer 14 is disposed on a substrate 12, such as a sapphire substrate. S
A thick n-type GaN layer 16 doped with i-impurity
It is formed on the GaN nucleation layer 14. A first confinement layer 18 composed of a GaN-based compound doped with Mg impurities is disposed on the thick Si-doped GaN layer 16. Thin In _X Ga _1-X N quantum wells (QW)
An active region 20 is disposed over the first confinement layer 18. The thin QW active region 20 is intentionally doped with magnesium (Mg). A second confinement layer 22 composed of AlGaN, optionally doped with Mg, is disposed over the thin QW active region 20. The first and second confinement layers, alone or in combination, are doped with Mg. A contact layer 24 composed of a GaN-based compound doped with Mg is disposed on the second confinement layer 22.

[0009] The impurities intentionally introduced into the quantum well active region increase the efficiency of the LED, increase the emission wavelength and exceed the emission wavelength of the undoped QWLED.
Furthermore, it is possible to reduce the uncontrollable or undesired effects of impurity diffusion by also intentionally adding impurities to one of the confinement layers. Alternatively, the layer that “confines” the QW active region may include Al _X G
a _1-X N can be included. If it is desired to improve the internal efficiency of the QW active region, these impurities
It can be a donor or an acceptor. QW
If it is desired to improve the injection efficiency of the active region, the impurity is an acceptor. Donors are oxygen, sulfur, selenium,
Alternatively, it can be selected from a group VI such as tellurium, or a group IV such as silicon, germanium, or tin. The acceptor is, for example, magnesium,
It can be selected from Group IIA, such as beryllium or calcium, or Group IIB, such as, for example, zinc, cadmium, or Group IV, such as, for example, carbon. Further, it has been found that a rare earth element selected from lanthanoids becomes the center of efficient light emission in other materials, and it can be expected that the efficiency can be extremely improved even in an AlInGaN material system.

The present invention affects the overall efficiency of a light emitting diode in four different ways. The total efficiency η _exte of a visible LED can be defined as the product of several individual independent efficiencies: η _exte = η _inte × η _inje × η _extr × η _dete . Here, the internal efficiency η _inte is the ratio of the minority carriers into which the minority carriers that emit photons are injected. The injection efficiency η _inje is the ratio of the current _delivered to the active region to the total current. The extraction efficiency η _extr is the ratio of photons _exiting the crystal to generated photons. Visible L
In the case of ED, the detection efficiency η _dete is a measure of the sensitivity of the eye per unit radiation power.

The internal efficiency is increased by the emission associated with impurities that is more efficient than emission near the band edge due to the high density of crystal defects.

The injection efficiency increases because the injection of minority carriers changes from holes to electrons. This is important for two reasons. First, the ratio of the electron concentration in the n-layer to the hole concentration in the p-layer significantly exceeds 1, which is convenient for electron injection. Second, electrons in GaN-based materials have much lower effective masses than holes, and are therefore much more mobile.

[0013] Extraction efficiency may be higher because the emission associated with impurities is not as strongly absorbed in the active region as light near the band edge.

The detection efficiency of the blue and green LEDs is strongly affected by the emission wavelength, and the increase in the wavelength increases the sensitivity of the human eye. The emission associated with the impurities of the present invention shifts the emission wavelength to longer and increases detection efficiency.

FIG. 2 shows a process chart of a manufacturing process for the device shown in FIG. In step 40, the first
A GaN nucleation layer having a small thickness is formed directly on a sapphire substrate at a low growth temperature such as 520 ° C. In step 50, a GaN: Si layer is formed directly on the nucleation layer at a growth temperature of about 1050 ° C., but with a thickness of 2 μm to 5 μm.
May fluctuate between In step 60,
A first confinement layer is formed over the GaN: Si layer. In step 70, Mg-doped InGa
An NQW active region is formed over the first confinement layer at a growth temperature ranging from 650 ° C. to 850 ° C., but the thickness of the QW active region is typically 3 nm. In step 80, the Mg-doped GaN layer is
Formed over the QW active region at growth temperatures in the range of 100 ° C., the thickness can vary between 0.1 and 1.0 μm.

These layers are formed by metal organic chemical vapor deposition (OMV).
Growing using one of many available techniques such as PE), metal organic chemical vapor deposition (MOCVD), molecular beam deposition (MBD), vapor phase MBE (GPMBE), or hybrid vapor phase epitaxy (HVPE) Is possible. Hereinafter, embodiments of the present invention will be exemplified.

(Embodiment 1): A substrate (12), a GaN nucleation layer (14) disposed on the substrate (12),
a Si-doped GaN current spreading layer (16) disposed on the aN nucleation layer (14), and a Si-doped GaN
First and second confinement layers (18, 22), each containing first and second impurities, respectively, and first and second confinement layers disposed on the current spreading layer (16). (1
8 and 22) and a thin quantum well active region (20) with quantum well impurities selected to enhance the light emitting properties of the light emitting device.
0). (Embodiment 2): The light emitting device according to embodiment 1, wherein the first impurity is selected so as to improve the light emission characteristics of the light emitting device by improving the injection efficiency.

(Embodiment 3): The quantum well impurity and the first impurity are the same element, and the element is selected so as to have an impurity diffusion effect in an active region. The light-emitting element according to aspect 1. (Embodiment 4): The light emitting device according to any one of Embodiments 1 to 3, wherein the quantum well impurity is a donor element. (Embodiment 5): The light-emitting device according to any one of Embodiments 1 to 3, wherein the quantum well impurity is an acceptor element. (Embodiment 6) The light-emitting device according to embodiment 5, wherein the acceptor element is selected from the group consisting of Group IIA and Group IIB elements. (Embodiment 7): The light emitting device according to embodiment 6, wherein the acceptor element is magnesium.

[Brief description of the drawings]

FIG. 1 is a diagram showing a light emitting device of the present invention.

FIG. 2 is a process chart of a manufacturing process of the device shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 light emitting element 12 substrate 14 GaN nucleation layer 16 GaN layer 18 first confinement layer 20 quantum well active region 22 second confinement layer 24 contact layer

Claims (7)

[Claims] A substrate, a GaN nucleation layer disposed on the substrate, and a Si-doped GaN disposed on the GaN nucleation layer.
A current spreading layer, a first and a second confinement layer disposed on the Si-doped GaN current spreading layer, respectively containing first and second impurities, and a first and a second A thin quantum well active region interposed between the confinement layers and comprising quantum well impurities selected to enhance the light emitting properties of the light emitting device. 2. The light emitting device according to claim 1, wherein the first impurity is selected so as to improve the light emitting characteristics of the light emitting device by improving the injection efficiency. 3. The method according to claim 1, wherein the quantum well impurity and the first impurity are the same element, and the element is selected to have an impurity diffusion effect in an active region. Light emitting element. 4. The light emitting device according to claim 1, wherein said quantum well impurity is a donor element. 5. The light emitting device according to claim 1, wherein said quantum well impurity is an acceptor element. 6. The method according to claim 6, wherein the acceptor element is a group IIA or II
Being selected from the group consisting of Group B elements,
A light emitting device according to claim 5. 7. The light emitting device according to claim 6, wherein said acceptor element is magnesium.