JPS61252675A - Blue-light emitting element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a blue-light emitting element characterized by light emitting efficiency, high reliability and less dispersion in characteristics, by using a single crystal thin film of zinc sulfide, which is prepared by an MOCVD method using an added body, as an insulating layer. CONSTITUTION:In an MIS type light emitting element using low resistance ZnS, into which a III-group element is doped, a single crystal ZnS thin film, which is prepared by an MOCVD method using an added body, is used as an insulating layer 4. When the single crystal ZnS thin film, which is the insulating film 4, is prepared by the MOCVD method in the preparing method of the MIS type light emitting element, the added body, which is obtained by the equimolar mixing of dialkyl zinc and dialkyl sulfur or dialkyl selenium is used as a Zn source, and hydrogen sulfide is used as a sulfur source. After a light emitting layer 3 is formed, the insulating layer 4 is continuously formed by stopping only the supply of dopant. Thus a ZnS insulating layer characterized by excellent insulating property and uniform thickness is formed and the light emitting efficiency, reliability, uniform characteristics and the like of the light emitting element can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a blue light emitting element used for display purposes or as a light source for sensors, etc., and a method for manufacturing the same.

[Summary of the invention]

The present invention utilizes low-resistance ZnS doped with group Ⅰ elements.
-3emicorductor) type light emitting device, which is characterized in that a ZnS single crystal thin film formed by the MOCVD method using an adduct is used as an insulating layer.
When forming an S single crystal thin film using the MOCVD method, an adduct obtained by equimolar mixture of dialkyl zinc and dialkyl sulfur or dialkyl selenium is used as the Zn source, and hydrogen sulfide is used as the sulfur source, and after the formation of the light emitting layer. The method is characterized in that only the supply of the dopant is interrupted and the insulating layer is formed continuously.

As a result of forming a ZnS insulating layer with excellent insulation properties and uniform thickness, the luminous efficiency, reliability, and uniformity of characteristics of the light emitting device were improved.

[Prior art]

Since the MOCVD method is a CVD technique that uses an extremely highly reactive organometallic compound as a raw material, it is a thin film forming method that is suitable for mass production and is capable of crystal growth at low temperatures.

By keeping the crystal growth temperature low, the incorporation of impurities into the grown film due to autodoping can be suppressed, and since the crystal growth process proceeds in a state deviated from the thermal equilibrium process, the occurrence of lattice defects can be reduced. This is an attempt to apply the MOCVD method, which has these advantages, to II-VI group metal semiconductors, where high-quality single crystal thin films have not been obtained due to the presence of impurity contamination and lattice defects generated during the crystal growth process. is being done.

For example, Japan J, A, P, 22 (1983
) L 583Japan J, A, P, 23 (1
983) L 388 and Z obtained by MOCVD method
For example, Extended Abstracts of MIS type blue light emitting device fabrication using nS single crystal thin film
the 15thConference o
f 5olid 5tate Devices a
ndMateiala Tokyo, 1985.
PP, 549-452. However, in the cited example above, MOCVD is
A light-emitting device with ZnS:AJ formed by the method as a light-emitting layer has not been realized, and undoped ZnS is replaced with bulk ZnS containing Al.
It is only an MIS type light-emitting device in which an insulating layer is a ZnS single-crystal thin film laminated on a crystal using the MOCVD method. This is because the MOCVD method used in the above cited example uses dimethyl zinc (DMZ) and hydrogen sulfide (HzS) as raw materials.
, 59 (1982) 155. Th1nSoli
d Films 55 (1978) 375-58
6 JapanJ, A, P 22 (1983) L
583, etc., the n-vt group MO
A gas phase reaction that occurs before the raw material reaches the growth substrate, which is characteristic of the CVD method, is the so-called "premature rea."
This is thought to be due to the influence of cation. In other words, the raw material gas reacts before reaching the substrate,
Because the generated ZnS fine particles are injected into the grown film,
This results in a decrease in the crystallinity of the resulting film. The crystallinity of the light emitting layer is 'premature reactio'.
It is considered that because of the decrease due to the influence of n'', the cited example did not lead to the realization of a light-emitting element having a light-emitting layer made of ZnS:AI formed by MOCVD.

Recently, a low-resistance ZnS:AI single crystal with a resistivity of several g.alpha. A membrane was obtained. Furthermore, this low resistance ZnS:AA! S on top of
Blue light emission was confirmed during forward bias due to the MIS type structure in which an insulating layer such as tow and an electrode layer were laminated.

Zinc source from dialkylzinc to the aforementioned adduct (!: K Yotte' premature rea
It is thought that a light emitting device using ZnS:AJ produced by MOCVD method was realized because cation' could be suppressed and the crystallinity of the light emitting layer was improved.

[Problem that the invention seeks to solve]

The blue light-emitting device manufactured by the above-mentioned conventional technique has the following problems because the sample is taken out after the growth of the light-emitting layer ZnS:AI is completed and the insulating layer is formed in a separate device. There is.

1, 2nS: Since the A1 surface is very active, the surface state is likely to change before the insulating layer is formed. Therefore, zn
The reproducibility of the interface state between S2Al and the laminated insulating layer is poor, and the device characteristics vary widely.

2. When forming an insulating layer by vapor deposition or sputtering, pinholes and the like are likely to occur, which can cause device destruction.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a structure and manufacturing method for a blue light-emitting element that has high luminous efficiency and reliability and has less variation in characteristics.

[Failure to solve the problem]

The blue light emitting device of the present invention is characterized in that a ZnS single crystal thin film formed by MOCVD using an adduct is used as an insulating layer. In addition, in the MIS type light emitting device manufacturing method, when forming a ZnS single crystal thin film as an insulating layer by MOCVD, an adduct obtained by equimolar mixing of dialkyl zinc and dialkyl sulfur or dialkyl selenium is used as Zn north. The method is characterized in that hydrogen sulfide is used as the sulfur source, and after the formation of the light-emitting layer, the insulating layer is continuously formed by interrupting only the supply of the dopant.

The adduct here includes not only a coordination compound obtained by an acid-base reaction when dialkyl zinc and dialkyl sulfur or dialkyl selenium are mixed in equimolar amounts, but also a mixture obtained by equimolar mixing. Furthermore, in the mixture, a part forms a coordination compound and the other part dissociates into dialkylzinc and dialkylsulfur or dialkylselenium.
This also includes cases where two chemical species coexist.

[Effect]

Since ZnS has a band gap of about 16 eV at room temperature, it becomes an insulating layer. Therefore, a high-quality ZnS single crystal thin film can be used as it is as an insulating layer. Exfeuded Abstracts ofthe
15th Conference of 5olid
3tateDeviea and material
s, Tokyo, (1983) pps49-5
As shown in No. 52, a ZnS thin film produced by the MOCVD method using DMZ also exhibits high resistance and can be used as an insulating film. However, in terms of insulation properties when voltage is applied, if there are many dislocations, line defects, etc. in the ZnS film, these are likely to cause current leakage or catastrophic breakdown. Therefore, as explained in the prior art, ZnS formed by the MOCVD method using DMZ as a zinc source.
It can be easily inferred that ZnS produced by the MOCVD method using an adduct, which has a high crystal quality, has better insulating properties. It can also be inferred that by continuously growing the ZnS:AI light emitting layer and the ZnS insulating layer, the interface between them can be formed with good reproducibility.

[Example 1] FIG. 1 shows an example of the cross-sectional structure of an element according to the present invention.

2 is a low-resistance n-type single crystal substrate made of GaAa, GaP, St, etc., and an ohmic electrode 2 is formed on one surface thereof.

MOCV with Zn north as adduct on the opposite side to ■
ZnS prepared by method D: AA! A light emitting layer (2) made of a single crystal film, etc., a ZnS single crystal film (2), and an electrode (2) are sequentially laminated, and the MIS structure is such that (2) corresponds to one S layer, (2) corresponds to two layers, and (2) corresponds to one M layer.

The device was manufactured using the following steps.

1. Formation of a light emitting layer (2) on a low resistance n-type single crystal substrate (2) by MOCVD method (2) Lamination of an insulating ZnS single crystal film (5) Vapor deposition or sputtering of an ohmic electrode material (4) Formation of an ohmic electrode (2) by alloying Formation 5: Formation of electrode (2) Following the above-described device fabrication process, s Z n S:
A method for manufacturing a blue light-emitting device according to the present invention will be described by taking as an example the manufacture of a device having A1 as a light-emitting layer.

FIG. 2 is a schematic diagram of the MOCVD apparatus used in the present invention.

A graphite susceptor (2) coated with SIC is placed inside a horizontal reaction tube (2) made of quartz glass, and a substrate (2) is further placed on top of it. High frequency heating furnace, infrared furnace from the side of the reactor.

Alternatively, heat the substrate using a resistance heating furnace.

The substrate temperature is monitored by a thermocouple embedded in the graphite susceptor. The reaction tube is connected to an exhaust system O and a waste gas treatment system 0 via pulps 0 and 0. The adduct obtained by equimolar mixing of dialkylzinc, which is Znose, and dialkyl sulfur or dialkyl selenium is enclosed in bubbler (2). In addition, triethyl aluminum (TEAA), which is the source of AI, is sealed in a bubbler [phase]. Carrier gas and hydrogen sulfide are each filled in cylinders. Purification equipment 0
The flow rate is controlled by carrier gas purified by hydrogen sulfide and a hydrogen sulfide Hamascrow controller Φ. The adducts and TEAI sealed in bubblers e and e are maintained at a predetermined temperature in a constant temperature bath. A desired amount of adduct and TEAl are supplied by introducing an appropriate amount of carrier gas into the bubbler and performing bubbling. Bubbler 0° [phase] and adduct supplied from cylinder 0, TEA
l.

The hydrogen sulfide is diluted with a carrier gas, then merged and introduced into the reaction tube (1) through a three-way pulp.

The three-way pulp 0 switches between introducing the raw material gas into the reaction tube [F] and disposing it into the waste gas treatment system O. Although FIG. 2 shows a horizontal reactor, the basic configuration is the same for a vertical reactor. However, if a mechanism for rotating the substrate is provided, it is necessary to ensure the uniformity of the film obtained.

Low-resistance n-type gallium arsenide (GaAs) is sliced in the (100) plane, a plane with a 5° or 2° deviation in the direction from the (100) plane to the (110) plane, and mirror-polished.
), gallium phosphide (GaP) and silicon (Si)t
Etching is performed after ultrasonic cleaning using trichlorethylene, acetone, and methanol. The etching conditions are as follows.

QaAs substrate HzSOn:HeOz:HzO=5
: 1 : 1 (Volume ratio) 2m1n GaP substrate at room temperature He:HNOs=3:1 (Volume ratio) 1sec Si substrate at room temperature HF:HeO-1: '
(Volume ratio) Etching was stopped using 2 ml of pure water at room temperature, washed with pure water and methanol, and then stored in a Daiflon.

Immediately before setting the substrate in the reaction tube, the substrate is taken out from the diaphragm, and the diaphron is removed by dry nitrogen blowing. After setting the substrates, the inside of the reactor is evacuated to about 10 Torr to remove any gas remaining in the system. After introducing carrier gas and returning the system to normal pressure, 1 to 2 J/mi
The temperature is started to rise while flowing a carrier gas of about n. An infrared heating furnace was used for heating. As the carrier gas, Het with a purity of 99.9999% or H2 passed through a purification device was used. After the substrate temperature reaches a predetermined temperature and becomes stable, supply of raw material gas is started and a low resistance ZnS film is grown. However, in the case of a Si substrate, 9
It is necessary to clean the substrate surface by heat treatment at 00° C. for about 10 minutes. The purity of the adduct used was 999999.
It is an adduct obtained by mixing equimolar amounts of dimethylzinc and diethyl sulfur.

This adduct has a vapor pressure of about 280 mHf at 30°C. Approximately 3 μm of Zn was grown under the growth conditions shown below.
An S:Al single crystal film is formed.

3 at a substrate temperature of 500 to 550°C, a distance zofi from the raw material inlet to the substrate, and an adduct bubbling amount of -16°C.
011Ll/min, T EAJ Bubbling Ki-1
2 QWLt/min at 0 °C, supply rate of 2% Hz S diluted with He 200 iaj/min, total gas flow rate including carrier gas 4.517 m1n, growth time 190 m1n, After forming the ZnS:Al layer, the following steps A ZnS dense layer is formed according to the following steps.

1. Discard the raw material gas to the gas treatment system O by operating the three-way pulp @, thereby interrupting the supply to the reaction tube (■).

2 Stop supplying TEAl by operating the bubbler at pulp 0.

5. TE remaining in the piping after disposing of the gas for a while
Remove AJ. In order to efficiently remove TEjl, the supply of all source gases and carrier gases may be interrupted, and the inside of the pipe may be degassed via the pulp 0°0 using the exhaust system (2).

4. Introduce the raw material gas consisting of the adduct and hydrogen sulfide into the reaction tube (2) by operating the three-way pulp.

Growth of undoped ZnS starts from this K.

By growing about 7 m1n, an undoped ZnS layer of about 100 OA' is formed.

After growth for a predetermined period of time, the supply of raw materials is stopped and the system is cooled. During cooling, He or Hz is applied at 1 to 2 J/min.
Let it flow. He was used to prevent thermal etching of the substrate surface.
Cooling may be performed while flowing 2 diluted Hz S at a rate of about 50 to 60 d/min. When the substrate returns to room temperature, the reactor is evacuated to remove hydrogen sulfide remaining in the system. After returning the system to atmospheric pressure, remove the substrate.

Subsequently, an ohmic contact is formed on the back surface of the substrate under the following conditions.

After depositing Au-Ge (Qem 12wt-%) or Au-2n on a GaAs substrate to about 200 OA', 350 OA' was deposited in an inert atmosphere.
Heat-treated GaP substrate Au-siAu-5i (Si%) or Au-Zn for 5-10 ml at ~500°C for about 2
400~600 in inert atmosphere after evaporation of about 00OA'
Heat treated Si substrate Al or AI-8i (S 1-2wt-%) for s~10m1n at ℃ 3
Sputtering or vapor deposition is carried out to the extent of 000A0, followed by heat treatment at 300° C. for 50 minutes in an inert atmosphere.Finally, a gold or ITO layer is formed on the insulating layer as a contact electrode. In order to ensure light extraction, Au is 500 to 500
Make it about A' thick.

When a forward bias voltage was applied to the device having the MIS structure manufactured as described above, light emission was observed from around 1 to 2 V.

The emission intensity increased in proportion to the current flowing through the device. A typical example of the emission spectrum of the obtained device is shown in FIG. The emission spectrum had a peak near 475 order at room temperature, and the luminous efficiency of the device was about 10.

When devices were fabricated using the above steps on a 25 m x 25 m wafer, the variation in device characteristics within the same uniform bar was about 10%. Furthermore, when comparing different batches, the results were also at the same level. It is believed that variations in device characteristics can be further reduced by improving the manufacturing process.

For comparison, MOCVD using KDMZ and hydrogen sulfide as raw materials
When undoped ZnS formed by the method was laminated on a znS:A1 light-emitting layer formed according to the above-mentioned process to form a MIS-type light-emitting device, which differed only in the manufacturing process of the insulating layer, the light-emitting efficiency was about 10 to 10. The variation in device characteristics was about 20%. Furthermore, the average life of the device was at most a fraction of that of a device formed using a monoadduct and having an insulating layer of undoped ZnS.

As is clear from the above comparison, when the undoped ZnS layer formed using the adduct is processed in a continuous process, ZnS:AI
By manufacturing an MIS type element by laminating the two layers, the characteristics and reliability of the element can be improved, and variations thereof can be reduced.

In the above explanation, the adduct K obtained by equimolar mixing of dimethylzinc and diethyl sulfur was described.
In addition, dimethyl zinc and dimethyl sulfur (vapor pressure flH at 20°C?), diethyl zinc and dimethyl sulfur (5
88 s+mHf' vapor pressure at 0°C) and diethylzinc and diethyl sulfur (15mH vapor pressure at 20°C)
Combination adducts such as f) can also be obtained by equimolar mixing of dialkylzinc and dialkylsulfur, and can be used in the same manner as the adducts of dimethylzinc and diethylsulfur.
This falls within the scope of the present invention. In addition, it hardly decomposes at a growth temperature of 400° C. or lower. Four types of adducts obtained from the combination K of dimethylselenium, diethylselenium, dimethylzinc, and diethylzinc can also be used as well as the adducts of alkylselenium, and are included in the present invention.

As can be easily inferred from the above explanation, in the same way as the addition of Al to ZnS, the addition of G, a, and In can also be performed using a corresponding organometallic compound, such as triethylgallium (boiling point = 14
3°C) and triethyl indium (boiling point -184°C). When the supply amount calculated from the vapor pressure at the bubbling temperature and the bubbling gas flow rate is equal to that of triethylaluminum, s Z n
S: Ga.

The MIS-type blue light emitting device using ZnS:In as a light emitting layer also exhibited characteristics similar to those using znS:Al as a light emitting layer.

〔Effect of the invention〕

As described above, in the blue light emitting device according to the present invention, Z
By forming an nS single crystal thin film, luminous efficiency and
Reliability and lifespan have been improved, and variations in device characteristics have also been reduced.

Furthermore, in the method for manufacturing a blue light emitting element according to the present invention,
After forming the light-emitting layer, the insulating layer is formed continuously by interrupting only the supply of dopant, making it possible to control the interface between the light-emitting layer and the insulating layer with good reproducibility. This has made it possible to reduce variations in device characteristics and improve device reliability. We believe that the present invention will greatly contribute to blue light emitting devices and their production.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a blue light emitting device manufactured according to the present invention. 1. Low resistance n-type single crystal substrate 2. Ohmic electrode
! h ZnS: A light-emitting layer made of AJ single crystal thin film, etc. 4. Insulating layer and electrode made of undoped ZnS single crystal thin film Figure 2 is a schematic diagram of the MOCVD apparatus used in the present invention & Reaction tube made of quartz glass Z Susceptor made of graphite with SiC coating a Substrate 9 High frequency heating furnace or infrared furnace or resistor Heating furnace 1α thermocouple 11. Exhaust system 12. Waste gas treatment system 1
3, 14. Pulp 15. Bubbler 1 containing adducts & Bubbler containing organometallic compounds of group I elements
1'1 Cylinder 1a containing carrier gas Cylinder 19 containing hydrogen sulfide, Gas purifier 21 Mass flow controller 21. Constant temperature bath 22. Mikata Pulp 25 Pulp Figure 3 is an emission spectrum diagram of the blue light emitting element produced in the present invention. that's all

Claims (1)

[Claims] 1. In a blue light-emitting element in which an insulating layer and an electrode layer are sequentially laminated on a light-emitting layer formed on a single crystal substrate by a metal organic vapor phase pyrolysis method (MOCVD method) using an adduct. A blue light emitting device, wherein the insulating layer is a zinc sulfide single crystal thin film produced by an MOCVD method using an adduct. 2. In a method for manufacturing a blue light-emitting device in which an insulating layer and an electrode layer are sequentially laminated on a light-emitting layer formed by an MOCVD method using an adduct on a single crystal substrate, dialkylzinc and dialkylsulfur or dialkylzinc are used as zinc sources. A method for producing a blue light emitting device, characterized in that a high resistance zinc sulfide single crystal thin film is formed as an insulating layer by an MOCVD method using an adduct obtained by equimolar mixing of dialkyl selenium and hydrogen sulfide as a sulfur source. 3. A method for manufacturing a blue light emitting device according to claim 2, characterized in that after the light emitting layer is formed, the insulating layer is continuously formed by interrupting only the supply of dopant.