JPS628959B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a zinc selenide light emitting diode that emits blue light.

Conventionally, a zinc selenide oxide film or a silicon oxide film is formed on the surface of a zinc selenide crystal, and this is used as an insulating layer.
Constructing a diode with an S (semiconductor layer) structure,
Alternatively, it has been proposed that a zinc selenide light emitting diode that emits blue light can be obtained by constructing a pn junction diode formed by implanting nitrogen ions into a zinc selenide crystal. (JP-A-52-18188; Method for manufacturing zinc selenide light-emitting diode; JP-A-52-18189; Method for manufacturing zinc-selenide light-emitting diode; JP-A-52-79788; Method for manufacturing zinc selenide light-emitting diode) However, However, with these conventional methods, the emission mechanism of blue light emission has not been fully elucidated, so it is necessary to find an effective method of adding effective impurities that increase blue light emission or a method of removing harmful impurities that reduce and eliminate blue light emission. Since it is unknown, the luminous efficiency of blue light emission is low, and there are problems in that pure blue light emission cannot be obtained due to the contamination of yellow.

The present invention solves the difficulties of these conventional methods and uses impurity elements that are effective in increasing the blue light emission intensity.
The present invention provides a method for manufacturing a zinc selenide light emitting diode in which the blue light emitting efficiency is improved by effectively adding zinc selenide crystals.

The blue light emitted by the zinc selenide light emitting diode exhibits a wavelength distribution with maximum intensity at a wavelength of about 4600 Å at room temperature.

The inventors investigated the effects of adding impurity elements and the effects of room temperature on the blue light emitted by photoluminescence.
By investigating the spectral changes down to temperatures as low as 200°C, it was revealed that the emission center is an exciton bound by a donor impurity.

Based on this, in order to increase the luminous efficiency of blue light emission, it is effective to add donor impurities such as group B elements such as gallium, indium, and aluminum, or group B elements such as chlorine, bromine, and iodine to the zinc selenide crystal. In addition to clarifying this fact, we also established an effective method for adding donor impurities.

In this case, it may also be necessary to reduce the zinc vacancies that form yellow luminescent centers or non-luminescent deep centers in zinc selenide, and the copper that forms red luminescent centers. revealed.

Incidentally, conventional electroluminescent devices have been doped with group elements, which are activators, and group elements, which are coactivators, in order to improve their luminous efficiency. This invention uses self-activated light emission and is different from the present invention, which uses exciton light emission.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail based on examples thereof with reference to FIG. 1, which shows the structure of a zinc selenide light emitting diode according to the present invention.

First, in the first manufacturing method of the zinc selenide light emitting diode according to the present invention, a zinc selenide crystal plate produced by high-pressure melting is cut into approximately 5 mm x 5 mm x 1 mm, polished, and then coated with 1 to 80 at% 2 to 16 at an ambient temperature of 700℃ to 1300℃ in zinc containing group B elements such as gallium, indium, and aluminum.
A heat treatment is performed for a period of time to cause the zinc selenide crystal plate to undergo the first means of adding these group B elements.

The surface of the zinc selenide crystal plate treated with the addition of group B elements in this manner has significantly deteriorated crystallinity due to the adhesion of zinc and the formation of an excessive zinc layer. Even if a light emitting diode is manufactured using a zinc selenide crystal plate in such a state, the luminous efficiency will be extremely low. Therefore, in order to remove such a layer of degraded crystallinity, the surface of the zinc selenide crystal plate to which group B elements have been added is etched using a chemical etching solution such as a sodium hydroxide solution as a second means.

Next, as a third means, the surface of the zinc selenide crystal plate 1 that has been etched is heated at an ambient temperature of 20°C.
A zinc selenide oxide film layer or a silicon oxide film layer 2 with a thickness of 50 Å to 5000 Å at a temperature of ℃ to 300 ℃,
It is formed by a method such as sputtering deposition.

Here, the reason why the ambient temperature was limited to 20°C to 300°C is as follows. There is a chemical oxidation method as a method of forming an oxide film at low temperature, and this method is usually performed at room temperature. 20
When the temperature is below 0.degree. C., the oxidation rate decreases, and it takes a long time to obtain a certain thickness, making it impractical. Therefore, the lower limit was set at 20°C.

On the other hand, zinc selenide is a relatively unstable substance;
When heated to high temperatures, zinc vacancies are formed on the surface, which increases resistance and poses problems in manufacturing light-emitting diodes. Therefore, the lower the formation temperature, the better. FIG. 2 shows the relationship between the silicon oxide layer formation temperature by the high frequency sputtering method and the luminous efficiency (external quantum efficiency) of the light emitting diode. Luminous efficiency decreases rapidly at temperatures above 300℃. This is due to thermal deterioration of zinc selenide crystals. Therefore, the upper limit was set to 300°C.

Next, the reason why the thickness of the oxide film layer is set to 50 to 5000 Å is as follows. If the oxide film layer 2 is too thin, it will be destroyed when a voltage is applied, and if it is too thick, its electrical resistance will increase and the luminous efficiency will decrease.

The movement of electrons (electrical conduction) between the zinc selenide crystal and all electrodes across the oxide layer is considered to be a tunnel effect. Therefore, ideally, the thickness of the oxide layer is desirably 100 to 200 Å or less.

However, if the thickness is less than 50 Å, the production yield will decrease, although the light emitting diode will be good. This is due to the non-uniformity of the film thickness and the presence of defects in the film.

On the other hand, even with a film thickness of about 5000 Å, current flows and good light emission characteristics are exhibited. FIG. 3 shows the relationship between the thickness of the zinc selenide oxide film and the luminous efficiency (external quantum efficiency). In addition, literature data is also shown. From this, it can be seen that even with a film thickness of about 5000 Å, the luminous efficiency does not decrease much and good luminescent characteristics are exhibited.

This seems to be because even though the film thickness is large, there are defects in the film, and conduction occurs through these defects, resulting in a substantial reduction in the film thickness. From the above, good light emitting characteristics can be obtained with a film thickness of 50 to 5000 Å.

As a fourth means, an alloy of indium-gallium is applied to the back surface of the zinc selenide crystal plate on which the zinc selenide oxide film layer or silicon oxide silicon oxide film layer 2 is formed on the surface, and then the alloy is placed in a nitrogen gas stream. The ohmic electrode 4 is formed by heat treatment at an ambient temperature of 300° C. for 5 minutes.

Finally, as a fifth means, at a predetermined location on the surface of the zinc selenide oxide film layer or the silicon oxide film layer 2 formed on the surface of the zinc selenide crystal plate,
By depositing gold and attaching the metal electrode layer 3, the zinc selenide light emitting diode according to the present invention is completed.

Next, a second method for manufacturing a zinc selenide light emitting diode according to the present invention will be described.

In this method, as the first method, a zinc selenide crystal plate made by high pressure melting method is
After cutting into mm pieces and polishing, add about 10g of zinc and 1g
Group B elements are added to the zinc selenide crystal plate by heat treatment for 5 to 16 hours at an ambient temperature of several 100 degrees Celsius in a quartz tube with a zinc compound of group B elements such as zinc chloride. do.

The surface of the zinc selenide crystal plate treated with the addition of group B elements in this manner has significantly deteriorated crystallinity due to the adhesion of zinc and the formation of an excessive zinc layer. If a zinc selenide crystal plate in this state is used,
Even if a light emitting diode is manufactured, the luminous efficiency will be extremely low. Therefore, in order to remove such a layer of degraded crystallinity, as a second means, the surface of the zinc selenide crystal plate to which group B elements have been added is etched using a chemical etching solution such as a sodium hydroxide solution.

As a third method, the surface of the zinc selenide crystal plate that has been etched is etched at an ambient temperature of 20°C to 300°C.
Then, a zinc selenide oxide film layer or a silicon oxide oxide film layer 2 with a thickness of 50 Å to 5000 Å is formed by a method such as sputtering deposition. As already mentioned, this oxide film layer 2 is destroyed due to voltage application and decrease in luminous efficiency due to increase in electrical resistance.
It is formed to a thickness of approximately 50 Å to 5000 Å. The reasons for limiting the ambient temperature and film thickness are the same as in the first manufacturing method.

On the back side of the zinc selenide crystal plate after the third method,
A fourth means of forming an ohmic electrode by applying an indium-gallium alloy and performing heat treatment for 5 minutes at an ambient temperature of 300°C in a nitrogen gas stream, and a zinc selenide oxide formed in this way. The zinc selenide light emitting diode according to the second manufacturing method is completed through the fifth means of attaching the metal electrode layer 3 by vapor depositing gold to a predetermined location on the surface of the film layer or silicon oxide film layer 2.

The blue light emission intensity of the zinc selenide light emitting diode according to the present invention tends to increase in proportion to the donor impurity concentration added to the zinc selenide crystal plate.

Therefore, in order to create a light emitting diode with high blue emission intensity, it is necessary to perform heat treatment at the highest possible temperature and under a high pressure atmosphere in order to add a large amount of donor impurities.

However, methods using quartz tubes have the problem of softening of the tubes at high temperatures and tube breakage due to increased pressure inside the tubes, making it difficult to perform heat treatment at temperatures significantly exceeding 1000°C.

In order to overcome this difficulty and add a large amount of donor impurities, it is convenient to use the third manufacturing method of the zinc selenide light emitting diode according to the present invention, which will be described below.

In this third production method, as a first means, a group B element or a zinc compound thereof, or one of a group B element or a zinc compound thereof is added to zinc selenide powder.
A seed or several kinds are added and heated in a high-pressure melting furnace to produce a zinc selenide crystal plate to which group B or group B elements are added.

Usually, zinc selenide crystals formed in a high-pressure melting furnace are rod-shaped, and in order to produce zinc selenide crystal plates from them, the rod-shaped crystals are cut and polished.
In order to remove the processing strain layer introduced at this time,
As a second method, the surface of the zinc selenide crystal plate containing a large amount of donor impurities obtained in the first method is etched with a chemical etching solution such as a sodium hydroxide solution.

As a third means, a zinc selenide oxide film layer or a silicon oxide silicon oxide film layer 2 with a thickness of 50 Å to 5000 Å is applied to the surface of the zinc selenide crystal plate treated in this way at an ambient temperature of 20°C to 300°C. , sputtering deposition, or other methods.

Note that the reason for limiting the ambient temperature and film thickness is the same as in the case of the first manufacturing method.

As a fourth method, an alloy of indium-gallium is applied to the back surface of the zinc selenide crystal plate on which the zinc selenide oxide film layer or silicon oxide silicon oxide film layer 2 is formed, and then heated at 300°C in a nitrogen gas stream. The ohmic electrode 4 is formed by heat treatment for 5 minutes at a high temperature, and as a fifth means, the surface of the zinc selenide oxide film layer or the silicon oxide film layer 2 formed on the surface of the zinc selenide crystal plate is heated. By vapor depositing gold and attaching the metal electrode layer 3 to predetermined locations, the zinc selenide light emitting diode according to the present invention is completed.

In this third production method, especially for group B elements such as chlorine, bromine, and iodine, they are added in the form of zinc chloride, zinc bromide, and zinc iodide.
This is advantageous in terms of controllability of the amount of added donor impurities.

In addition, when heat-treating zinc selenide crystals with high vapor pressure substances such as chlorine, bromine, iodine, zinc chloride, zinc bromide, and zinc iodide, these substances are added sufficiently even at temperatures of about 1000°C. During this process, the quartz tube will not soften, and only damage due to pressure increase inside the tube needs to be taken into consideration. In this case, place a vacuum-sealed quartz ampoule in a high-pressure melting furnace and heat it at 1000°C for 1 to
A method of heat treatment under conditions of 50 atm is effective.

FIG. 1 is a diagram showing the structure of a zinc selenide light emitting diode according to the method of the present invention.

An ohmic electrode layer 4 is formed on the back surface of the n-type zinc selenide crystal layer 1 doped with donor impurities, and the surface of the n-type zinc selenide crystal layer 1 has a thickness of 50 Å to
An oxide film layer 2 of a zinc selenide oxide film or a silicon oxide film with a thickness of 5000 Å is formed. Further, a metal electrode layer 3 is attached and formed on the surface of the oxide film layer 2.

When a voltage of 2 to 5 V is applied between the metal electrode layer 3 and the ohmic electrode layer 4 of the zinc selenide light emitting diode having such a configuration, a current of 1 to 30 mA flows and blue light is excited.

At this time, the function of the emission intensity and wavelength λ of the zinc selenide light emitting diode according to the method of the present invention is expressed as
As shown in the figure.

Curve a in the figure shows the luminescence intensity of the zinc selenide light emitting diode manufactured by the first method according to the present invention. This diode uses a zinc selenide crystal plate.
After heat treatment in zinc containing 10 atomic% (hereinafter referred to as at%) gallium at a temperature of 1000°C for 5 hours, the surface layer was etched in a boiled 30% sodium hydroxide solution, followed by high frequency treatment. A silicon oxide film with a thickness of 1000 Å was formed using a sputtering method at a substrate temperature of 150°C.

Curve b is a zinc selenide crystal plate in zinc, 1000
Curve c shows the luminescence intensity of a conventional diode heat-treated at a temperature of 1000°C for 5 hours in gallium. It indicates strength.

As is clear from FIG. 4, by adding gallium as a donor impurity, the zinc selenide light emitting diode according to the present invention can achieve a blue light emission intensity that is more than 10 times that of conventional diodes. That is clear. In this case, the added impurity is not limited to gallium, but similar results can be obtained if it is a group b element or a group b element.

By using any of the above manufacturing methods, it is possible to obtain a light emitting diode having blue light emission intensity ten times or more higher than that of a conventional light emitting diode.

As explained in detail above, according to the present invention,
A zinc selenide light-emitting diode that can be excited to emit blue light with excellent wavelength characteristics by effectively adding a group B element or a group B element to a zinc selenide crystal plate, and whose blue light emission intensity is more than 10 times that of conventional ones. It is possible to provide a manufacturing method for.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a zinc selenide light emitting diode according to the present invention, FIG. 2 is a diagram showing the relationship between the formation temperature of a silicon oxide film and the effective efficiency, and FIG.
The figure shows the relationship between the thickness of the zinc selenide oxide film and the luminous efficiency, and FIG. 4 shows the relationship between the luminous efficiency and wavelength of the zinc selenide light emitting diode according to the present invention. 1... N-type zinc selenide crystal layer, 2... Oxide film layer, 3... Metal electrode layer, 4... Ohmic electrode layer.

Claims (1)

[Claims] 1. Consists of a zinc selenide crystal layer with an ohmic electrode layer formed on the back surface and doped with impurities, and a zinc selenide oxide film or a silicon oxide film formed on the surface of the zinc selenide crystal layer. In the production of a zinc selenide light emitting diode having an oxide film layer and a metal electrode layer impregnated on the oxide film layer, a group B element or a group B element is added to a zinc selenide crystal plate as a donor impurity. A first means of adding zinc in an excessive zinc atmosphere to reduce the concentration of zinc vacancies in the substrate, and removing a degraded layer or a strained layer from processing on the surface of the zinc selenide crystal plate that has passed through the first means. Second etching for
and forming an oxide film layer consisting of a zinc selenide oxide film or a silicon oxide film with a thickness of 50 Å to 5000 Å on the surface of the zinc selenide crystal plate that has undergone the above second means at a temperature of 20° C. to 300° C. a fourth means of forming an ohmic electrode by heat-treating the back surface of the zinc selenide crystal plate;
and a fifth means for attaching a metal electrode to the surface of the oxide film layer. 2. A zinc selenide crystal layer with an ohmic electrode layer formed on the back surface and doped with impurities; an oxide film layer made of a zinc selenide oxide film or a silicon oxide film formed on the surface of the zinc selenide crystal layer; In manufacturing a zinc selenide light emitting diode having a metal electrode layer attached on an oxide film layer, a zinc selenide crystal plate is heated at a temperature of 700°C to 1300°C in zinc containing 1 to 80 at% group B elements. A first means of adding the Group B element by performing a heat treatment for 2 to 16 hours, and a second means of etching the surface of the zinc selenide crystal plate that has undergone the first means to remove a deteriorated layer. The surface of the zinc selenide crystal plate that has undergone the second means is heated at 20°C to 300°C.
a third means of forming an oxide film layer consisting of a zinc selenide oxide film or a silicon oxide film with a thickness of 50 Å to 5000 Å at a temperature of A method for manufacturing a zinc selenide light emitting diode, comprising: a fourth means for forming a metal electrode; and a fifth means for attaching a metal electrode to the surface of the oxide film layer. 3. A zinc selenide crystal layer with an ohmic electrode layer formed on the back surface and doped with impurities; an oxide film layer made of a zinc selenide oxide film or a silicon oxide film formed on the surface of the zinc selenide crystal layer; In manufacturing a zinc selenide light-emitting diode having a metal electrode layer attached to an oxide film layer, a zinc selenide crystal plate is vacuum-sealed in a quartz tube together with a zinc compound of group B element and heated at a temperature of several hundred degrees Celsius. 5 to
A first means of adding the Group B element by performing a heat treatment for 16 hours; a second means of etching the surface of the zinc selenide crystal plate that has undergone the first means to remove a deteriorated layer; The surface of the zinc selenide crystal plate that has undergone the second means is heated at 20°C to
A third means of forming an oxide film layer made of a zinc selenide oxide film or a silicon oxide film with a thickness of 50 Å to 5000 Å at a temperature of 300°C, and heat-treating the back surface of the zinc selenide crystal plate to make it ohmic. A method for manufacturing a zinc selenide light emitting diode, comprising a fourth means for forming an electrode and a fifth means for attaching a metal electrode to the surface of the oxide film layer. 4. A zinc selenide crystal layer with an ohmic electrode layer formed on the back surface and doped with impurities; an oxide film layer made of a zinc selenide oxide film or a silicon oxide film formed on the surface of the zinc selenide crystal layer; In manufacturing a zinc selenide light-emitting diode having a metal electrode layer attached on an oxide film layer, a group B element or a zinc compound thereof, or a group B element or a zinc compound thereof is added to zinc selenide and the mixture is heated in a high-pressure melting furnace. a first means of forming a zinc selenide crystal plate to which group B or group B elements are added; and a first means of etching the surface of the zinc selenide crystal plate that has passed through the first means to remove a processed layer. 2, and the surface of the zinc selenide crystal plate that has passed through the second means is heated at a temperature of 20°C to 300°C for 50°C.
A third means of forming an oxide film layer made of a zinc selenide oxide film or a silicon oxide film with a thickness of Å to 5000 Å, and a fourth means of forming an ohmic electrode by heat-treating the back surface of the zinc selenide crystal plate. and a fifth method of attaching a metal electrode to the surface of the oxide film layer.
A method for manufacturing a zinc selenide light emitting diode, comprising the steps of: