JPS58194B2 - GAP - Google Patents

Description

Detailed Description of the Invention Technical Field of the Invention The present invention relates to the production of a GaP two-color light emitting device in which a pn junction exhibiting red light emitting characteristics and a pn junction exhibiting green light emitting characteristics are formed on a single GaP substrate crystal. Regarding the method.

Technical background of the invention and its problems GaP is well known as a material that emits red and green light with high efficiency at room temperature.

For red emission, the closest pair of zinc and oxygen atoms form the luminescent center, and for green emission, the nitrogen atom forms the luminescent center.

Therefore, in order to produce devices with these luminescent colors, it is necessary to control the luminescent center impurity concentration within the crystal.

On the other hand, a high-pressure drawn single crystal (LEC crystal) is a large-area substrate crystal commonly used for GaP.

However, the light emitting properties of this crystal are not good, and in order to appropriately control the impurity concentration, this crystal is not directly used to form a pn junction, but usually a double liquid phase growth method or the like is used.

For example, in a red light emitting device, an n-type liquid phase epitaxy crystal (LPE crystal) is grown on an n-type LEC crystal substrate, and this layer is doped with oxygen atoms in addition to donor impurities.

Next, a p-type layer containing zinc and oxygen is grown on this crystal to form a p-n junction.

In addition, in green light emitting devices, an n-type LPE layer containing donor impurities and nitrogen atoms is formed on an n-type LEC crystal substrate, and then a p-type layer containing acceptor impurities and nitrogen atoms is formed.
Make an n-junction.

Further, in addition to the method of forming a pn junction by second liquid phase growth, the p-type layer may be formed by a diffusion method.

However, when manufacturing this type of GaP two-color light emitting device, there are the following problems.

That is, the formation of the various crystal layers described above involves heat treatment, but these heat treatments deteriorate the characteristics of the crystal layers.

In particular, the photoluminescence efficiency of an n-type LPE crystal doped with nitrogen is significantly degraded by heat treatment of the crystal.

Conventionally, heat treatment during growth of an n-type LPE crystal layer to form a red light-emitting element, or during diffusion to form each pn junction of red and green light-emitting elements, has been applied to the nitrogen-doped n-type LPE. It also added to the crystal layer, and as a result, deterioration of the characteristics of the crystal layer could not be avoided.

For this reason, it has been difficult to prevent a decrease in the luminous efficiency of the green light emitting element due to the deterioration in the photoluminescence efficiency of the n-type LPE crystal added with nitrogen.

Furthermore, when comparing the effective brightness (brightness perceived by the human eye) of a red light emitting element and a green light emitting element at the same current level, the red light emitting element is higher.

Therefore, it has been extremely difficult to equalize the brightness of red and green at the same current level in a GaP two-color light emitting device.

OBJECTS OF THE INVENTION The purpose of the present invention is to prevent deterioration of the characteristics of a pn junction nitrogen-containing n-type LPE crystal that exhibits green light emission characteristics due to heat treatment during the formation of other crystal layers or during the formation of the pn junction. A method for manufacturing a GaP dichroic light emitting device that can improve the luminous efficiency of the light emitting device and, in turn, provide a highly efficient GaP dichroic light emitting device with well-balanced red and green brightness at the same current level. It is about providing.

Summary of the Invention The gist of the present invention is to provide different n-type liquid phase growth layers on an n-type GaP substrate crystal, and to connect a first pn junction exhibiting red light emitting characteristics to one n-type liquid phase growth layer, and to connect a first pn junction exhibiting red light emitting characteristics to the other n-type liquid phase growth layer. When manufacturing a GaP two-color light emitting device in which a second pn junction exhibiting green light emitting characteristics is provided in the liquid phase growth layer, the thermal process for manufacturing the first pn junction side is replaced by the thermal process for manufacturing the second pn junction side. This is because the process was done before the heat process in manufacturing.

In order to form pn junctions with different characteristics on the same crystal substrate, it is not necessarily necessary to use both sides of the substrate.

For example, it is also possible in principle to form two pn junctions by sequentially stacking them on the same surface of the substrate.

By selecting the thermal process for forming the two pn junctions as described above, a highly efficient and well-balanced two-color light emitting device can be obtained.

Before explaining the embodiments, the basic data that forms the background of this invention will be explained first.

The external emission quantum efficiency of GaP green light emitting devices is generally 0.0.
About 2% (10 Acm-2) is often obtained.

On the other hand, the external emission quantum efficiency of a GaP red light emitting device is about 2 to 3% (10 Acm-2).

Since there is a 30-fold difference in luminous efficiency between these emission colors of GaP, a green emission efficiency of 0.02% shows brightness equivalent to a red emission efficiency of 0.6%.

In other words, the brightness of a red light emitting element and a green light emitting element is approximately 4
There is a difference of twice as much.

On the other hand, red light-emitting devices exhibit higher efficiency at low current levels, and green light-emitting devices exhibit higher efficiency at high current levels.

Considering these points, in order to equalize the brightness of the red light emitting element and the green light emitting element at the same current level, it is desirable to make the green light emitting element higher in efficiency.

As mentioned above, the green light emitting element is an n-type LEC crystal substrate.
A dual liquid phase growth method is commonly used in which an LPE-type crystal layer is grown followed by a p-type layer.

In this case, high luminous efficiency can be achieved by adding nitrogen atoms, which are the luminescent center, to the n-type LPE crystal, and by designing the impurity concentration near the p-n junction to increase the injection ratio of holes into the n-type layer. An element is obtained.

Further, even when the p-type layer is formed by a diffusion method, the addition of the luminescent center is performed during the growth of the n-type LPE crystal.

Therefore, in green light-emitting devices, the addition of the luminescent center nitrogen atom to the n-type LPE crystal is one of the most important processes, and it remains to be seen what kind of luminescent properties the crystal will have as a result of this addition. , is one element that determines the final device characteristics.

Therefore, the inventors adopted measurement of the green photoluminescence efficiency at room temperature obtained by excitation with argon ion laser light (4880 people) as a method for evaluating the luminescence characteristics of the n-type LPE crystal.

This photoluminescence efficiency is proportional to the concentration of luminescent centers and inversely proportional to the concentration of non-luminescent centers.

As a result of crystal evaluation using this measurement, the following facts were revealed.

That is, the photoluminescence efficiency of the n-type LPE crystal doped with nitrogen shows a significant deterioration phenomenon when the crystal is heat-treated.

Moreover, this deterioration is noticeable in high-temperature treatments of 900° C. or higher.

Therefore, it is desirable to avoid exposing the nitrogen-doped n-type LPE crystal to high temperatures of 900° C. or higher as much as possible.

The present invention focuses on such points, and a GaP crystal substrate is provided with a first n-type GaP layer and a first n-type GaP layer containing zinc and oxygen.
A first pn junction having red light emitting characteristics made of a P layer and a second pn junction having green light emitting characteristics made of a second n type GaP layer containing nitrogen and a second n type GaP layer are formed. When manufacturing a GaP two-color light emitting device, the first n-type GaP layer is formed before the second n-type GaP layer, and the second n-type GaP layer is formed before the second n-type GaP layer. Type G
Temperature lower than the formation temperature of the aP layer, preferably 900 [°C]
] This is a method in which formation is performed at a lower temperature.

Effects of the Invention According to the present invention, the formation of the n-type GaP layer (first n-type GaP layer) constituting the first pn junction exhibiting red light emitting characteristics is performed by forming the second pn junction exhibiting green light emitting characteristics. Since the heat treatment is performed before the formation of the constituent nitrogen-containing n-type GaP layer (second n-type GaP layer), the heat treatment when forming the first n-type GaP layer is applied to the second n-type GaP layer. This can be prevented from occurring.

Furthermore, the formation of an n-type GaP layer (second n-type GaP layer) constituting a second p-n junction exhibiting green light-emitting characteristics is performed using a second n-type GaP layer.
Since it is performed at a temperature lower than the formation temperature of the type GaP layer,
It is possible to prevent the characteristics of the second n-type GaP layer from deteriorating due to heat treatment when forming the second n-type GaP layer.

Therefore, it is possible to significantly improve the luminous efficiency of the green light emitting element.

Embodiment of the Invention FIGS. 1A to 1D are cross-sectional views showing the manufacturing process of a GaP two-color light emitting device according to an embodiment of the invention.

First, as shown in FIG. 1a, an n-type LPE crystal layer 2 doped with donors and oxygen is grown on one of the (100) planes of an n-type GaP-LEC crystal substrate 1.

The growth conditions were Ga 20 g, GaP 1.5 g,
Ga2O30.1g, Te8mg, the growth start temperature is 1050°C, and the cooling rate is 10°C/min.

As a result, the donor concentration [N
D-NA] is obtained.

Next, as shown in FIG. 1, an n-type LPE crystal layer 3 doped with nitrogen atoms is formed on the other (100) plane.

The growth conditions were 20 g of Ga, 1 g of GaP, and 5 mg of GaN, no donor impurities were intentionally added, and the growth starting temperature was 100 g.
The temperature was 0°C, and the cooling rate was 4°C/min.

As a result, an LPE crystal plane having a donor concentration of about 2 to 3×10 17 cm −3 is obtained.

Next, zinc is diffused into the different n-type LPE crystal layers 2 and 3 formed on the front and back surfaces of the substrate 1 in this way, and as shown in FIG.
P-type layers 4 and 5 are formed as shown in FIG.

The diffusion temperature was 740°C, the zinc pressure was 1 mg/15 ml, the phosphorus pressure was 0.2 mg/15 ml, and the diffusion time was 5 hours.

Finally, as shown in FIG. 1d, mesa etching is performed on the green light emitting diode side to expose the n-type LPE layer 3,
7.8 and pelleted.

Here, the reason why the green light emitting side was mesa-etched was because of the difference in current density dependence of luminous efficiency between green light emission and red light emission, as mentioned earlier. This is because it is desirable that the area be smaller than the area of the first pn junction J1 that emits red light.

As a result, the green luminous efficiency is 0.0 in the second pn junction J2.
2% (10 Acm-2), and the first pn junction J1 showed a red luminous efficiency of 0.8% (10 Acm-2).

Since the green luminous efficiency of 0.02% corresponds to the brightness of the red luminous efficiency of 0.6%, the two junctions exhibit approximately equal luminance for the same current.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof.

For example, as shown in FIG. 2, the p-type layer 5' on the green light emitting side
The same result was obtained even when the electrode was formed by selective diffusion and the electrode was taken out from the n-type LPE layer 3 without performing mesa etching.

Moreover, it goes without saying that a double liquid phase growth method may be used in which the p-type layers 4 and 5 are formed not by diffusion but by liquid phase growth.

[Brief explanation of the drawing]

1A to 1D are cross-sectional views showing the manufacturing process of a GaP two-color light emitting device according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a pellet structure in another embodiment. 1... n-type GaP-LEC crystal substrate, 2, 3...
......n-type LPE crystal layer, 4,5...p-type layer, Jl...first pn junction (red light emission), J
2...Second pn junction (green light emission).

Claims (1)

[Scope of Claims] 1. A first 'pnpn junction exhibiting red light emitting characteristics consisting of an n-type GaP layer and an n-type GaP layer containing zinc and oxygen on a GaP crystal substrate. a
When manufacturing a GaP two-color light emitting device formed by forming a second pn junction consisting of a P layer exhibiting green light emitting characteristics, the n-type GaP layer constituting the first pn junction is
The n-type GaP layer forming the second pn junction is formed before the n-type GaP layer forming the second pn junction,
A method for manufacturing a GaP two-color light emitting device, characterized in that the device is formed at a temperature lower than the formation temperature of an n-type GaP layer containing nitrogen. 2. A first pn junction exhibiting red light emitting characteristics consisting of an n-type GaP layer and an n-type GaP layer containing zinc and oxygen on a GaP crystal substrate, and a green light-emitting layer consisting of an n-type GaP layer containing nitrogen and an n-type GaP layer. When manufacturing a GaP two-color light emitting device formed by forming a second pn junction exhibiting characteristics, the first
The n-type GaP layer constituting the pn junction of the second pn
Formed before the n-type GaP layer constituting the junction,
Formation of the n-type GaP layer constituting the second pn junction
A method for manufacturing a GaP two-color light emitting device, characterized in that the manufacturing method is carried out at a temperature lower than 00°C.