JP2561321B2 - Method of manufacturing light emitting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a light emitting device using a II-VI group compound, and particularly to a method for manufacturing a blue light emitting device using a II-VI group compound containing zinc. Regarding

[Conventional technology]

An ion implantation method has been conventionally known as a method of controlling the conduction type of silicon or gallium arsenide. On the other hand, a p-type forming method for zinc selenide or zinc sulfide single crystal thin film has not been well established, and an ion implantation method can be considered as one means, but specific conditions are hardly known.
In particular, the rate at which implanted atoms contribute to electrical conduction without removing damage due to implantation by heat treatment after ion implantation and without causing intrinsic defects in zinc vacancies and group VI vacancies (activation rate).
The conditions for improving the are hardly known. In addition to the above-mentioned conditions, almost no study has been made on the quality required for a crystal thin film for ion implantation, such as the stoichiometric ratio.

[Problems to be Solved by the Invention] Generally, when impurities are added to a crystal by ion implantation, damage to the crystal due to that is inevitable, and the damage is recovered, and the implanted impurities effectively contribute to electric conduction. Therefore, some heat treatment process is indispensable. However, the zinc selenide crystal thin film has the following problems. That is, when the zinc selenide single crystal thin film is vapor-phase grown, unless the growth temperature is set to a low temperature of 200 to 400 ° C., an intrinsic defect occurs and crystal quality is deteriorated. Further, if the stoichiometric ratio of this thin film is not properly maintained, deep levels due to intrinsic defects are easily generated even by the low temperature heat treatment at about the above growth temperature. Therefore, there is a serious problem that it is extremely difficult to ion-implant zinc selenide with impurities and obtain p-type conduction without impairing the crystal quality.

[Means for solving the problem]

The present invention has been made in order to solve the above-mentioned conventional problems, and comprises a step of epitaxially growing a low-resistance n-type II-VI group compound single crystal thin film on a single crystal substrate. A step of epitaxially growing a non-doped high resistance II-VI compound single crystal thin film, a step of adding a p-type dopant to the high resistance single crystal thin film by using an ion implantation method, and a heat treatment of the single crystal thin film added with the dopant In the method for manufacturing a light emitting device including steps, the heat treatment is performed at a temperature of 550 to 800 ° C. in an atmosphere of an inert gas and / or a gas containing a group II element.

In the present invention, the heat treatment is performed at 550 to 800 ° C. in an atmosphere of an inert gas and / or a gas containing a group II element, but if both conditions are not met, a light emitting device having a good light emitting function cannot be obtained. .

Heat treatments below 550 ° C. do not recover the damage caused by ion implantation and do not activate the dopant. 55
Inert gas and / or even heat treatment at 0 ~ 800 ℃
Unless in the atmosphere of a gas containing a group II element, a defect is generated in the II-VI group compound semiconductor thin film, and a light emitting device having a good light emitting function cannot be obtained. Heat treatment at a temperature higher than 800 ° C. causes defects in the thin film, even in an atmosphere of an inert gas and / or a gas containing a group II element.

The heat treatment time is adjusted depending on the heat treatment temperature, the amount of ion implantation, and the like, but it is usually preferable to be 1 minute or more and 6 hours or less.

The atmosphere of the inert gas and / or the gas containing the group II element may be under any pressure such as pressurization, normal pressure, and reduced pressure, but the normal pressure should prevent the occurrence of defects in terms of equipment and the like. In terms of

Further, it is preferable that the treatment temperature is relatively high, because the defects caused by the higher concentration implantation can be recovered, and it is desirable to set the treatment temperature to 620 to 760 ° C.

The heat treatment is carried out in a gas atmosphere containing an inert gas and / or a group II element.
Examples of the gas containing a group II element such as N ₂ , He, Ne and Ar include dimethyl zinc, diethyl zinc, zinc simple substance and the like.

Used when using gas containing Group II elements
It is preferred to use Group II elements of II-VI compounds.

When a gas atmosphere containing a Group II element is used, the atmosphere may be 100% of the gas, but in order to perform heat treatment under normal pressure, the gas containing the Group II element should be 10 ^-5 mol%.
It is preferable to make the above.

[Action]

According to the present invention, in the production of a zinc selenide light emitting device, in order to obtain a p-type film by an ion implantation method, first, by maintaining a high stoichiometric ratio of the film before the ion implantation, Even under the heat treatment conditions, an inert gas such as nitrogen is used as an atmosphere gas in the atmosphere containing a group II element (zinc) vapor in order to suppress vacancies of the group II element (zinc). Heat treatment up to 800 ℃ can be achieved while suppressing the generation of certain Group II element (zinc) vacancies. Therefore, the damage caused by implantation begins to gradually recover from the damage to the implanted film when the processing temperature is 450 ° C or higher, and as the heat treatment temperature increases,
The rapid damage is removed without the generation of intrinsic defects (deep levels involved in Zn vacancies), and the implanted atoms can also be activated, so that the film exhibits p-type conduction.

〔Example〕

FIG. 3 and FIG. 4 are sectional views showing the structure of the light emitting device produced according to the present invention.

FIG. 3 is an example showing a device structure using a pn junction of ZnSe when an n-type GaAs (100) substrate or a ZnSe (100) substrate is used as a single crystal substrate. On the other hand, FIG. 4 shows the device structure of the blue light emitting element when the p-type GaAs (100) substrate 6 is used. In both cases, the plane orientation of the substrate may be the (100) plane or (100) to <110
It may be off to 2 to 5 degrees. The growth conditions of the film are described in detail in JP-A-63-79795. However, the growth temperature is 250 ° C., the pressure in the tube is atmospheric pressure, and the gas is a group VI source gas, hydrogen selenide, and a group II source material. Using dimethyl zinc, its molar flow rate ratio (ratio of selenium to zinc)
Keep it at 20. The flow rate of dimethyl zinc is 11.5 ×
10 ^-6 mol / min, 3 liters / with hydrogen as carrier gas
It is made by being raised in minutes. Also, n-type ZnSe2 is 10 ¹⁸ cm
It is a film with an electron concentration of ^-3 . Also, as the doping gas, tBu-I (tercinal butyl iodine) or EtI is used.
(Ethyl iodine), hydrogen iodide, hydrogen chloride or the like is used.

 The manufacturing process of the light emitting device shown in FIG. 3 will be described below.

About n-type ZnSe2 as a buffer layer on n-type GaAs substrate 1
After growing about 0.3 μm, high resistance non-doped ZnSe layer 3
Is grown to about 0.3 μm. After that, lithium ions are implanted into the high-resistance non-doped ZnSe layer 3 at an acceleration voltage of 50 keV and an ion current of 80 μA at a dose of about 10 ¹⁴ cm ^-2 . After injection
The substrate is placed in an annealing furnace and heat-treated at 757 ° C. for 5 minutes in a nitrogen atmosphere at a normal pressure (flow rate 4 liters / minute). FIG. 1 is an evaluation of this by photoluminescence, and the untreated one does not show blue light emission. However, after heat treatment at 451 ° C for 5 minutes, a slight blue luminescence was started and heat treatment started at 657 ° C.
The intensity of blue emission increases rapidly when performed at ℃,
It can be seen that the damage caused by the injection has been recovered. Furthermore, when the temperature is raised to 757 ° C, blue light emission due to lithium becomes even stronger, which is about 10,000 times that of the untreated one. This indicates that lithium atoms are activated in the film by heat treatment at about 700 ° C. or higher.

In addition, dimethyl zinc (DMZ) was used as an atmosphere gas at 10 ^−5.
Even if the heat treatment is performed at 700 ° C for 5 minutes in an atmosphere of hydrogen carrier gas (4 / min) containing moles / minute, Zn vacancy is the same as in the case of heat treatment in nitrogen atmosphere at 757 ° C for 5 minutes in Fig. 1. It is possible to suppress the generation of a deep level related to and activate the lithium atom.

After this heat treatment, Au.Sb alloy 4 is vapor-deposited on the upper surface of the sample, and Au.Ge alloy 5 is vapor-deposited on the lower surface as an ohmic electrode.

FIG. 2 shows the light emission time characteristics when current is injected into the blue light emitting device manufactured in this manner. Strong blue emission without long-wavelength emission via deep levels was obtained.

 The manufacturing process of the light emitting device shown in FIG. 4 will be described below.

A high resistance non-doped ZnSe film 3 is formed on the p-type GaAs substrate 6 by 0.3
After μm grown to 10 ¹⁴ cm ^-2 ions implanted lithium 50KeV80myuei. After injection, sample 757 in a nitrogen atmosphere.
Heat treatment is performed at 5 ° C. for 5 minutes to activate lithium atoms and obtain a p-layer. After that, the substrate is again placed in the reaction chamber and the n-type ZnSe layer 2 is grown to a thickness of about 3 μm, and the Au / In ohmic electrode 7 is formed on the upper surface and the Au / Zn ohmic electrode 8 is formed on the lower surface.

The blue light-emitting device manufactured in this manner also exhibits strong blue light emission, which is almost the same as in FIG.

The heat treatment temperature required to recover the damage caused by the implantation depends on the implantation dose amount. At 10 ¹³ cm ^-2 or less, the impurities are sufficiently activated even at the heat treatment temperature of 450 ° C.
At temperatures above 0 ¹⁴ cm ^-2 , damage does not recover even at 500 ℃, and at least at 550 ℃ or higher. Further, in such high temperature ion implantation, the activation of impurities rapidly increases with temperature and reaches a maximum around 800 ° C, but selenium atoms start to evaporate from the film, and the film surface has a rough film quality. Due to the deterioration, the blue emission intensity also sharply decreases.

Although zinc selenide has been described in this example, this is also applicable to zinc sulfide or a mixed crystal of zinc selenide and zinc sulfide. The implanted ions are not limited to lithium, but may be sodium, potassium, group V nitrogen, phosphorus, arsenic, antimony, or the like. The atmosphere for the heat treatment is preferably atmospheric pressure, but reduced pressure is also possible. Further, the metal material for ohmic electrode is not limited to the above,
Any material can be used as long as it can form ohmic contact with each of the p-type and p-type.

〔The invention's effect〕

According to the present invention, until now, p-type zinc selenide by the ion implantation method, and further, a blue light emitting device using a pn junction have not been studied at all. By setting the film formation conditions and the heat treatment conditions after ion implantation to the above conditions, it becomes possible to remove the damage due to the implantation and activate the implanted ions without generating intrinsic defects and deep levels caused by them. , P-type zinc selenide can be produced, and a zinc selenide blue light emitting device utilizing a pn junction can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in photoluminescence spectrum of a zinc selenide film due to a change in heat treatment temperature, and FIG. 2 is a diagram showing an emission spectrum of a light emitting device manufactured in Example,
FIG. 3 and FIG. 4 are sectional views showing the outline of the light emitting device produced in the example.

Claims (1)

(57) [Claims] 1. A step of epitaxially growing a low resistance n-type II-VI compound single crystal thin film on a single crystal substrate, and an undoped high resistance II-VI compound single crystal thin film is epitaxially grown on the low resistance single crystal thin film. In the manufacturing method of the light emitting device, the heat treatment is inactive, including a step, a step of adding a p-type dopant to the high-resistance single crystal thin film by using an ion implantation method, and a step of heat-treating the single crystal thin film added with the dopant. A method for producing a light-emitting element, which is performed at a temperature of 550 to 800 ° C. in an atmosphere of a gas and / or a gas containing a group II element.