JPH04299876A - Semiconductor light emitting element material - Google Patents

Abstract

PURPOSE:To obtain semiconductor light emitting element material which has high efficiency for light output and is suitable to devices for display and optical communication. CONSTITUTION:The title material has a structure wherein gallium nitride based compounds are laminated on a sapphire R face (>>1, -1, 0, 2] face) whose off-angle is smaller than or equal to 0.8, and is formed by a CBE method or the like, without using an AlN buffer layer. This semiconductor light emitting element is thin, flat, and excellent in single-crystallinity, so that high efficiency for light output is obtained. Hence this material is suitable to devices for display and optical communication use.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is particularly applicable to displays,
The present invention relates to semiconductor light emitting device materials that are optimal for optical communications.

0002

[Prior Art] Semiconductor light-emitting devices, particularly visible light-emitting diodes (LEDs), are used as functional display devices in all fields, but ultraviolet to blue semiconductor light-emitting devices have not yet been put to practical use and development is still slow. It's urgent. As ultraviolet to blue semiconductor light emitting devices, ZnSe, GaN,
Research is focused on materials such as SiC.

[0003] Gallium nitride (GaN) is often deposited on the C-plane of sapphire by the MOCVD method or the VPE method [Journal of Applied Ph.D.
ysics, 56 P. 2367-2368 (198
4)]. However, to obtain a flat surface, generally 20 to
A film thickness of 30 μm or more is required, and even if an AlN buffer layer is used, a film thickness of at least about 4 μm or more is required [
Applied Physics Letter,
48 P. 353-355 (1986)].

[0004] GaN semiconductor light emitting devices generally receive light from the substrate side.
ical Report, 28 P. 83-92(
1982)], in semiconductor light emitting devices that require a thick film, a decrease in light extraction efficiency is inevitable. As described above, conventional GaN-based thin films for semiconductor light emitting devices require a film thickness of 4 μm or more, and it is also necessary to planarize the GaN thin film by operations such as providing an AlN buffer layer [Journal of the Japanese Society of Crystallography, 15 P. 334-342 (1988
)], a decrease in light extraction efficiency was unavoidable.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a thin and flat GaN-based single crystal thin film in order to increase light extraction efficiency.

[0006]

[Means for Solving the Problems] As a result of extensive research to solve the above problems, the present inventors have discovered that GaN can be used with a thin film thickness without the need for operations such as providing an AlN buffer layer.
The present invention was completed based on the discovery that planarization of thin films based on the system can be realized. That is, the present invention has a structure in which at least one n-type gallium nitride compound layer and at least one gallium nitride compound light-emitting layer are laminated on a sapphire R surface with an off angle of 0.8° or less. The present invention provides a semiconductor light emitting device material characterized by the following.

The present invention will be explained in more detail below. In the present invention, a sapphire R-plane with an off angle of 0.8° or less means that the [1-102] plane (R-plane) of single crystal sapphire (α-Al2O3) has an off angle of plus or minus 0.
A polished surface that is the substrate surface with an accuracy of 8 degrees or less. Moreover, this off-angle can be confirmed by X-ray diffraction method. When a sapphire R-plane with an off-angle exceeding 0.8° is used as a substrate, a flat GaN surface cannot be obtained with a film thickness of 1 μm or less, and the single crystallinity of GaN also deteriorates. Therefore, in order to obtain a flat GaN surface with a film thickness of 1 μm or less, it is necessary to use a sapphire R surface with an off angle of 0.8° or less as a substrate. It is preferable to use a sapphire R surface with an angle of preferably 0.5° or less, more preferably 0.3° or less. Furthermore, it is more preferable that the substrate surface has a streak pattern that can be observed in RHEED (reflection high-speed electron diffraction).

[0008] Furthermore, at least one type of n in the present invention
The type gallium nitride compound layer is, for example, GaN or G
a1-x Alx N, Ga1-x Inx N, Ga
1-x Mixed crystal compounds mainly composed of GaN such as BxN, or these compounds containing Zn, Mg, Be, Cd, Si,
It is a substance to which a very small amount of Ge, C, Sn, Hg, etc. is added as an impurity, and exhibits n-type conductivity characteristics with a controlled number of n-type carriers. It is also possible to stack compounds, to change the liquid crystal ratio depending on the film thickness, or to use different n-type gallium nitride compounds depending on the position on the film surface.

In the present invention, the at least one gallium nitride compound light-emitting layer includes, for example, Ga1-x Alx N, Ga1-x Inx N, G
a1-x Zn, Mg, Be, Cd, etc. are added as impurities to a mixed crystal compound mainly composed of GaN such as BxN, and p
It exhibits type or i-type conductivity, and forms a pn junction (p-type, n-type semiconductor junction), mis structure (insulator, semiconductor junction structure), etc. with the n-type gallium nitride-based compound. However, it operates as a light emitting layer.

[0010] Using these junctions, it is also possible to fabricate elements with complex structures such as double heterostructures, quantum well structures, and superlattice structures. Furthermore, the thickness of these laminated films can be kept to 2 μm or less, more preferably 1 μm or less, which is extremely effective in improving light extraction efficiency. As an example, FIG. 1 shows the structure of a mis-type light emitting device. An n-type GaN single crystal film (2) is laminated to a thickness of 0.8 μm on the sapphire R plane (1) with an off angle of 0.8° or less, and an Mg-doped GaN single crystal high resistance film (3) is further layered to a thickness of 0.8 μm. It is a 0.05 μm laminated layer. Also, the electrode (4),
Al was used for (5).

[0011] The film forming method is generally known as
For example, CBE method, CVD method, MOCVD method, vacuum evaporation method, sputtering method, etc. can be used, and among them, CBE method is most preferable. As an example, an example in which a gallium nitride mis-type stacked film is formed by the CBE method will be described below.

The apparatus includes a vacuum container (6
), the evaporation crucible (Knudsen cell) (7), (8
), (9), a CBE apparatus equipped with a gas cell for introducing gas (10), and a substrate heating holder (11) was used. Put Ga metal into the evaporation crucible (7), put Mg metal into the evaporation crucible (8),
They were heated to 1020°C and 270°C, respectively. A gas cell (10) is used to introduce the gas, and the gas is directly introduced into the substrate (12).
It was set up so that it would spray on the air. NH3 was used as the introduced gas, and the amount introduced was 5 cc/min.

The degree of vacuum in the vacuum container is 1 to 5× during film formation.
The pressure was about 10-6 Torr. Off angle 0.5 for the board
A sapphire R plane ([1-102] plane) with a radius of 10°C or less was used and heated to 800°C. The off angle can be measured from an X-ray rocking curve by X-ray diffraction method, and in this case,
It was measured using Cu-Kα radiation. First, film formation was performed by opening the shutter of the Ga crucible while supplying NH3 gas to form a GaN thin film with a film thickness of 0.8 μm.
The shutter of the crucible (g) was opened and while doping was being carried out, a further film thickness of 0.2 μm was laminated.

[0014] This laminated film is irradiated with a He-Cd laser as excitation light, and photoluminescence (P
When observing L), the wavelength was approximately 0.4 as shown in Figure 3.
Blue light emission with a peak around 7 μm was obtained. Also,
When a light emitting element as shown in FIG. 1 was prototyped and its current-voltage characteristics were measured, it exhibited diode characteristics as shown in FIG. 4.

Note that the film forming method is not limited to this.

[0016]

【Example】

[0017]

[Example 1] Hereinafter, gallium nitride mis
A specific example of forming a mold laminated film will be described. The apparatus includes an evaporation crucible (
A CBE apparatus equipped with a gas cell (10) for introducing gas, and a substrate heating holder (11) was used.

Ga metal was placed in the evaporation crucible (7), and Mg metal was placed in the evaporation crucible (8), which were heated to 1020°C and 270°C, respectively. A gas cell (10) was used to introduce the gas, and was installed so as to spray the gas directly onto the substrate (12). NH3 was used as the introduced gas, and the amount introduced was 5 cc/min. The degree of vacuum in the vacuum container is 1 to 5 x 10- during film formation.
The pressure was about 6 Torr.

A sapphire R plane ([1-102] plane) with an off angle of 0.5° was used as the substrate and heated to 800°C. The off-angle can be measured from an X-ray rocking curve by X-ray diffraction, and in this case, it was measured using Cu-Kα radiation. First, while supplying NH3 gas, the shutter of the Ga crucible was opened to form a film, and a Ga crucible with a thickness of about 0.8 μm was formed.
A thin N film was formed, and then the shutter of the Mg crucible was opened to perform doping while further layering the film to a thickness of 0.05 μm.

When this laminated film was irradiated with a He-Cd laser as excitation light and photoluminescence (PL) was observed, blue light emission with a peak around a wavelength of about 0.47 μm was obtained as shown in FIG. Ta. Furthermore, when a light emitting element as shown in FIG. 1 was prototyped and its current-voltage characteristics were measured, it showed diode characteristics as shown in FIG. 4.

[0021]

[Comparative Example 1] The substrate has a sapphire R surface with an off angle of 1° ([1
, -102] plane) to create a laminated film similar to that in Example 1 will be described. First, the shutter of the Ga crucible was opened and film formation was performed to form a GaN thin film with a thickness of about 0.8 μm, and then the shutter of the Mg crucible was opened and doping was performed while further layering with a thickness of 0.05 μm was performed.

When this laminated film was irradiated with a He--Cd laser as excitation light and photoluminescence (PL) was observed, almost no light was emitted.

[0023]

[Example 2] Hereinafter, Ga1-x Inx was prepared by CBE method.
An example in which an N mixed crystal mis-type stacked film is formed will be described. The apparatus includes evaporation crucibles (Knudsen cell) (7), (8), (9),
Gas cell for gas introduction (10), substrate heating holder (11)
) was used.

Ga metal was placed in the evaporation crucible (7), Mg metal was placed in (8), and In metal was placed in (9).
It was heated to 20°C, 270°C, and 680°C. A gas cell (10) was used to introduce the gas, and was installed so as to spray the gas directly onto the substrate (12). NH3 was used as the introduced gas, and the amount introduced was 5 cc/min. The degree of vacuum in the vacuum container was approximately 1 to 5×10 −6 Torr during film formation.

A sapphire R plane ([1-102] plane) with an off angle of 0.5° was used as the substrate and heated to 800°C. The off-angle can be measured from an X-ray rocking curve by X-ray diffraction, and in this case, it was measured using Cu-Kα radiation. First, while supplying NH3 gas, Ga, In
The shutter of the crucible was opened to form a film, and the film thickness was approximately 0.8 μm.
A Ga1-x Inx N thin film (x=0.2) was formed, and then the shutter of the Mg crucible was opened and doping was performed while further layering was performed to a thickness of 0.05 μm.

When this laminated film was irradiated with a He--Cd laser as excitation light and photoluminescence (PL) was observed, light emission having a peak around a wavelength of about 0.51 μm was obtained.

[0027]

[Example 3] Hereinafter, gallium nitride mis
An example in which a type multilayer laminated film is formed will be described. The apparatus includes an evaporation crucible (
A CBE apparatus equipped with a gas cell (10) for introducing gas, and a substrate heating holder (11) was used.

Ga metal was placed in the evaporation crucible (7), and Mg metal was placed in the evaporation crucible (8), and the crucibles were heated to 1020°C and 270°C, respectively. A gas cell (10) was used to introduce the gas, and was installed so as to spray the gas directly onto the substrate (12). NH3 was used as the introduced gas, and the amount introduced was 5 cc/min. The degree of vacuum in the vacuum container is 1 to 5 x 10- during film formation.
The pressure was about 6 Torr.

A sapphire R plane ([1-102] plane) with an off angle of 0.5° was used as the substrate and heated to 800°C. The off-angle can be measured from an X-ray rocking curve by X-ray diffraction, and in this case, it was measured using Cu-Kα radiation. First, while supplying NH3 gas, the shutter of the Ga crucible was opened and a film was formed to form a Ga crucible with a thickness of approximately 0.8 μm.
A thin N film was formed, and then the shutter of the Mg crucible was opened to perform doping while further layering the film to a thickness of 0.05 μm. Next, close the shutter of the Mg crucible again, and
N was deposited to a thickness of 0.5 μm, and then the shutter of the Mg crucible was opened to perform doping while further increasing the film thickness to 0.05 μm.
Then, the shutter of the Mg crucible was similarly closed, GaN was deposited to a thickness of 0.5 μm, and then the shutter of the Mg crucible was opened and doping was carried out while the film thickness was further increased to 0.
．． The layers were laminated to a thickness of 0.05 μm. In this way, a three-layer gallium nitride mis-type multilayer laminate film was formed.

When this laminated film was irradiated with a He-Cd laser as excitation light and photoluminescence (PL) was observed, blue light emission with a peak around a wavelength of about 0.47 μm was obtained.

[0031]

[Example 4] Hereinafter, Ga1-x Inx was prepared by CBE method.
An example in which an N mixed crystal mis-type stacked film is formed will be described. The device includes evaporation crucibles (Knudsen cells) (7), (8), (9) in a vacuum container (6) as shown in Figure 2.
, gas cell for gas introduction (10), substrate heating holder (1
A CBE apparatus equipped with 1) was used.

Ga metal was placed in the evaporation crucible (7), Mg metal was placed in (8), and In metal was placed in (9).
It was heated to 20°C, 270°C, and 680°C. A gas cell (10) was used to introduce the gas, and was installed so as to spray the gas directly onto the substrate (12). NH3 was used as the introduced gas, and the amount introduced was 5 cc/min. The degree of vacuum in the vacuum container was approximately 1 to 5×10 −6 Torr during film formation.

A sapphire R plane ([1, -102] plane) with an off angle of 0.5° was used as the substrate and heated to 800°C. The off-angle can be measured from an X-ray rocking curve by X-ray diffraction, and in this case, it was measured using Cu-Kα radiation. First, while supplying NH3 gas, the shutter of the Ga crucible was opened and a film was formed to form a G film with a thickness of approximately 0.8 μm.
After forming an aN thin film, the shutter of the In crucible was opened to form a film, and Ga1-x In with a film thickness of about 0.5 μm was formed.
A xN thin film (x=0.2) was formed, and then the shutter of the Mg crucible was opened to perform doping while further stacking the film to a thickness of 0.05 μm.

When this laminated film was irradiated with a He--Cd laser as excitation light and photoluminescence (PL) was observed, light emission having a peak around a wavelength of about 0.5 μm was obtained.

[0035]

Effects of the Invention Since the semiconductor light emitting device material according to the present invention is a thin laminated thin film that cannot be achieved using conventional techniques, it can improve the light extraction efficiency in the production of semiconductor light emitting devices.
This can greatly contribute to facilitating the patterning process.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the structure of an example of a prototype semiconductor light emitting device.

FIG. 2 is a schematic diagram of an experimental apparatus used in carrying out Examples.

FIG. 3 is a spectrum diagram showing the photoluminescence measurement results of the laminated film obtained in Example 1.

4 is a graph showing the voltage and current measurement results of the semiconductor light emitting device obtained in Example 1. FIG.

[Explanation of symbols]

1 Sapphire R-plane substrate with an off angle of 0.8° or less 2
N-type GaN single crystal film 3 Mg-doped GaN single crystal film 4 Al electrode 5 Al electrode 6 Vacuum vessel 7 Evaporation crucible 8 Evaporation crucible 9 Evaporation crucible 10 Gas introduction gas cell 11 Substrate heating holder 12 Substrate 13 Cryopanel 14 Valve 15 Liquid nitrogen trap 16 Oil diffusion pump 17 Oil rotary pump 18 Shutter 19 Shutter 20 Shutter

Claims (1)

[Claims] 1. At least one n-type gallium nitride compound layer on the sapphire R-face with an off angle of 0.8° or less,
and a semiconductor light emitting device material characterized by having a structure in which at least one type of gallium nitride compound light emitting layer is laminated.