JP2003069073A - GaN LIGHT EMITTING ELEMENT AND ITS MANUFACTURING METHOD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a GaN light emitting element formed on an n-type SiC substrate doped with nitrogen, which can be improved in brightness by keeping the SiC substrate conductive, restraining the light emitted from a light emitting layer from being reabsorbed, and specifying the range of electron concentration in the SiC board, and to provide a method of manufacturing the same. SOLUTION: A GaN light emitting element has a laminated structure composed of an n-type GaN buffer layer 2, an n-type GaN semiconductor layer 3, a p-type GaN semiconductor layer 4, and a p-type GaN contact layer 5 which are successively laminated on an n-type SiC substrate 1 through an epitaxial growth method, where the concentration of electrons in the n-type SiC substrate 1 is regulated so as to amount to 1×10<17> cm<-3> to 1.5×10<18> cm<-3> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaN-based light emitting device and a method for manufacturing the same.

[0002]

2. Description of the Related Art A semiconductor light emitting device capable of emitting light with a short wavelength in a blue light region has been desired for a long time and recently,
A light emitting device capable of emitting short wavelength light using a GaN-based semiconductor has been realized. The GaN-based semiconductor has a direct transition type optical transition and is capable of generating radiative recombination with high efficiency, and therefore has a short wavelength semiconductor laser or a high brightness LED.
Is being developed as a material for high efficiency light emitting devices such as

To manufacture devices such as LEDs made of the GaN-based semiconductor, epitaxial growth methods such as metal organic growth (MOCVD) method and molecular beam epitaxy (MBE) method are used. Since it is difficult to manufacture a GaN single crystal substrate as a substrate in these manufacturing methods, a sapphire (single crystal alumina) substrate, a SiC single crystal substrate, or the like is used. Since the sapphire substrate has electrical insulation, electrodes cannot be provided on the back surface of the substrate, which limits the structure of the device, whereas the SiC single crystal substrate also has good electrical conductivity. And has the advantage that the degree of freedom in device structure is high.

[0004]

[Problems to be Solved by the Invention] However, GaN
When a light emitting element such as a semiconductor LED is formed on a nitrogen (N) -doped n-type SiC substrate, the substrate reabsorbs the light emitted from the light emitting layer, thereby reducing the luminous efficiency. There is. Since the reabsorption of light is due to free electrons or impurities in the SiC substrate, the electron concentration range in the SiC substrate should be controlled so that light absorption can be sufficiently suppressed while maintaining the conductivity of the SiC substrate. It will need to be adjusted.

The present invention has been made in consideration of such problems. That is, the present invention provides a GaN-based semiconductor light-emitting device formed on a nitrogen-doped n-type SiC substrate, the SiC substrate being capable of maintaining the conductivity of the SiC substrate and suppressing light reabsorption thereof. It is an object of the present invention to provide a GaN-based light emitting device and a method for manufacturing the same that can improve the luminous efficiency by defining the electron concentration range inside.

[0006]

In order to solve the above-mentioned problems, a GaN-based light-emitting device of the present invention comprises an n-type GaN-based semiconductor layer and a p-type on a nitrogen-doped n-type SiC single crystal substrate. In a GaN-based light emitting device in which at least one GaN-based semiconductor layer is formed, the n-type SiC single crystal substrate has an electron concentration of 1 × 10 ¹⁷ cm ⁻³ or more and 1.5 or more.
Wherein the × is ^{10 1} 8 ^{cm -3} or less.

In the method for manufacturing a GaN-based light emitting device of the present invention, an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are laminated in this order on a nitrogen-doped n-type SiC single crystal substrate by an epitaxial growth method. In the GaN-based light emitting device, the electron concentration of the n-type SiC single crystal substrate is 1 × 1.
It is characterized in that it is 0 ¹⁷ cm ⁻³ or more and 1.5 × 10 ¹⁸ cm ⁻³ or less.

The n-type SiC single crystal substrate (hereinafter, simply referred to as a substrate)
(Also called a plate) electron density is 1 × 10¹⁷cm
^-3If less than, the activity of the GaN light emitting device on the substrate
The effect of suppressing re-absorption of light emitted by the layer may be increased.
However, a metal such as Ni is vapor-deposited on the back surface of the substrate
When forming the electrode, ohmic characteristics with the substrate deteriorate
However, it makes the formation of the ohmic electrode difficult. Also the substrate
The operating voltage of the device is
There is also the problem of rising. On the other hand, if the electron density of the substrate is
1.5 x 10¹⁸cm^-3The larger the
The light reabsorption by the electrons is excessively increased and
There is a problem that the amount of projection is reduced and the luminous efficiency is suppressed. This
Taking these into consideration, the electron concentration of the n-type SiC single crystal substrate is set to 1 ×.
10¹⁷cm ^-3More than 1.5 x 10¹⁸cm^-3less than
By adjusting the Ga content while maintaining the conductivity of the substrate,
It is possible to increase the brightness of the N-based light emitting element.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a laminated structure of a GaN-based semiconductor light emitting device for explaining an embodiment of the present invention. First, as shown in FIG. 1, an n-type SiC substrate 1 (hereinafter sometimes simply referred to as the substrate 1).
The n-type GaN-based buffer layer 2 is formed on one of the main surfaces, and then the n-type GaN semiconductor layer 3, the p-type GaN semiconductor layer 4, and the p-type GaN-based contact layer 5 are heteroepitaxially grown. The formation of the layers described above is a known MOCV.
It can be performed by the D (Metalorganic Chemical Vapor Deposition) method or the MBE method (Molecular Beam Epitaxy). In addition, in this specification, MBE is, in addition to MBE in a narrow sense in which both a metal element component source and a non-metal element component source are solid, a MONBE in which the metal element component source is an organic metal and the non-metal element component source is a solid. (Metal Organic Mo
lecular Beam Epitaxy), a gas source MBE that uses a solid metal element source as a gas and a non-metal element source as a gas, and a chemical beam epitaxy (CBE) that uses a metal element source as an organic metal and a non-metal element source as a gas Epitax
y)) is included as a concept.

When the laminated structure shown in FIG. 1 is formed by the MOCVD method, the following materials can be used as main raw materials. -Ga source: trimethyl gallium (TMGa), triethyl gallium (TEGa), etc. N source: Ammonia (NH ₃ ) and the like.

N-type doping is performed by adding N to the n-type SiC substrate 1 and adding Si, which is a group IV element, to the n-type GaN-based buffer layer 2 and the n-type GaN semiconductor layer 3. Further, the p-type GaN semiconductor layer 4 and the p-type GaN-based contact layer 5 are p-type doped by adding Mg that is a group II element. The dopant sources are shown below. · N source: ammonia (NH _3), such as. -Si source: Silicon hydride such as silane. Mg source: Biscyclopentadienyl magnesium (Cp
₂ Mg) etc. In this example, Si and Mg are used as the dopant elements other than the substrate 1. However, group IV elements such as C, Ge, and Sn are used as the n-type dopant, and Ca, Sr, and p-type dopants are used. Group II elements such as Zn may be used.

After laminating the laminated structure shown in FIG. 1, an Au alloy or the like is vapor-deposited on the front surface and a metal such as Ni is vapor-deposited on the rear surface and heat-treated to form an ohmic electrode. After that, the GaN-based semiconductor light emitting device is formed by separating by dicing or the like.

In the n-type SiC substrate 1 shown in FIG. 1, the electron concentration is 1 × 10 ¹⁷ cm ^{−3 in} order to increase the brightness of the GaN-based light emitting device while maintaining the conductivity of the substrate 1.
It is adjusted to 1.5 × 10 ¹⁸ cm ⁻³ or less. It is necessary to adjust the nitrogen concentration in the substrate 1 to be n-type doped so that it falls within the electron concentration range.
Doping so as to be in the range of × 10 ¹⁷ cm ⁻³ or more and 1.5 × 10 ¹⁹ cm ⁻³ or less prevents the formation of excessive nitrogen atoms and maintains a high activation rate, The electron concentration can be within the above numerical range. The N concentration in the substrate 1 was measured by secondary ion mass spectrometry (SIMS), and the electron concentration was measured by van der Pau (va
N der Pauw) method or capacity-voltage characteristic (C-V characteristic) method.

FIG. 2 shows the correlation between the electron concentration of the substrate and the luminance in the GaN-based light emitting device in which the electron concentration of the substrate is changed by the above manufacturing method. As is clear from the figure, the brightness decreases when the electron concentration exceeds 1.5 × 10 ¹⁸ cm ⁻³ . On the other hand, the electron density is 1x
Even if it is less than 10 ¹⁷ cm ⁻³ , the brightness is not reduced, but after forming a metal such as Ni on the back surface of the substrate and then performing heat treatment to form an ohmic electrode, the ohmic characteristics with the substrate deteriorate. It may be difficult to form an ohmic electrode or the resistivity of the substrate itself may increase, which may increase the operating voltage of the device.
It is necessary to make it 1 × 10 ¹⁷ cm ⁻³ or more.

[0015]

As shown by the present invention, N-doped n
In a GaN-based semiconductor light-emitting device fabricated on a SiC substrate of SiC type, the electron concentration of the SiC substrate is 1 × 10 ¹⁷ cm 2.
By adjusting the 1.5 × 10 ¹⁸ cm ^-3 or less than ^-3, maintaining its conductivity, and it is possible to suppress light resorption result, the luminous efficiency is improved, the luminance variation It becomes possible to suppress, and it becomes favorable from the viewpoint of productivity.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a laminated structure of a GaN-based semiconductor light emitting device showing an embodiment of the present invention.

FIG. 2 is a correlation diagram between the electron density and the brightness of the substrate according to the present invention.

[Explanation of symbols]

1 n-type SiC substrate 3 n-type GaN semiconductor layer 4 p-type GaN semiconductor layer

Claims (3)

[Claims] 1. A GaN-based light-emitting device having at least one n-type GaN-based semiconductor layer and at least one p-type GaN-based semiconductor layer formed on a nitrogen-doped n-type SiC single-crystal substrate. The electron density of the substrate is 1 × 10
A GaN-based light-emitting device characterized by having a size of ¹⁷ cm ⁻³ or more and 1.5 × 10 ¹⁸ cm ⁻³ or less. 2. The nitrogen concentration in the n-type SiC single crystal substrate is 1 × 10 ¹⁷ cm ⁻³ or more and 1.5 × 10 ¹⁹ cm.
^-3 or less, The GaN type light emitting element characterized by the above-mentioned. 3. A GaN-based light emitting device in which an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are stacked in this order on a nitrogen-doped n-type SiC single crystal substrate by an epitaxial growth method, wherein The electron concentration of the crystal substrate is 1 × 10 ¹⁷ cm ⁻³ or more and 1.5 × 10 ¹⁸ cm ^−3.
A method for manufacturing a GaN-based light-emitting device, characterized in that: