JPS6276575A - Mis type light emitting element - Google Patents

Abstract

PURPOSE:To improve luminous efficiency, and to rejularte sincle stabilize dynam ic characteristics by using an LB film containing an addition polymerization polymer, a side chain thereof has nonlocalized group pi electrons, as an insulating film. CONSTITUTION:The inside of sub-phase aqueous phase is prepared and maintained at predetermined pH, temperature and metallic salt concentration, and the developing solution of an organic substance containing an addition polymerization polymer is dropped onto the water surface thereof, thus develop ing a monomolecular film layer. An LB film 13 in prescribed film thickness is accumulated onto a substrate 11, holding a monomolecular film at fixed surface pressure as a condensed film. The whole is dried sufficiently in an inert gas atmosphere, such as N2, Ar, etc., and a predetermined metal is evapo rated onto the LB film through an evaporating mask with a proper pattern, thus forming an electrode 14. Carbon-carbon unsaturated bonds are subjected to an addition reaction and the addition polymerization polymer employed is formed, but the addition polymerization polymer is of a polymer and side chains thereof have substituents with nonlocalized group pi electrons.

Description

Detailed Description of the Invention (Techniques of the Invention (Field ii)) The present invention relates to an MfS type light emitting device having a metal (M)/'insulator (+)-'semiconductor (S) junction structure, particularly an insulating The present invention relates to an MIS type light emitting device using an organic film as a body.

[Techniques of invention ((i) backstory and its problems) Electroluminescent device,
In particular, visible light emitting diodes (LEDs) are widely used as U1 display elements in all fields. Recently, printers.

Applications such as mini-fax machines are also being considered, and their popularity is likely to increase in the future.

Currently, red, yellow, green, etc. LEDs use GaP, GaAs, AffiGaAs as semiconductor substrates.

A ■-V group compound semiconductor such as GaASP is used, and impurities such as Zn, ○, and N are appropriately added to this substrate to form a pr+ junction, and the recombination light emission created at the pn junction interface is utilized. ing. These LEDs have a high luminous efficiency of 0.2 to several percent (direction is less than 1q).

On the other hand, as a blue LED board, 3
Compound semiconductors such as iC, ZnS, and Zn5c are used. However, in SiC, high quality crystals are
It is difficult to form a ρn junction with Zns and Zn3c.

Therefore, for these, 1 to 11
Seven attempts are being made to create 1,141 light-emitting devices by configuring three junctions. At present, this tvl l S type light emitting element still has a luminous efficiency as low as -3 compared to the above-mentioned ρn junction type red, yellow, etc. LEDs, and is also extremely unstable. One of the reasons for this is that it is extremely difficult to form an excellent insulating film such as the silicon oxide film used in the current 81 IsI on the semiconductor (4) substrates mentioned above. be.

When a light emitting element is constructed with a ~IIS junction, the following conditions are essential for the intermediate insulating film, for example.

First, the film thickness can be made thin enough to allow tunneling of electrons or holes, and high-precision sampling can be performed.
Second, it has a homogeneous and uniform thickness with no structural defects such as pinholes. Third, there is a trap level that traps electrons and holes at the interface between the insulating film and the metal or the interface between the insulating film and the semiconductor. Fourthly, there is no heat generation associated with light emission or deterioration due to voltage application.

Taking these circumstances into consideration, in recent years, attempts have been made to form cumulative imprints of organic molecules on various semiconductor single plates by the Langmuir-Blogier method (hereinafter referred to as the LB method) and use this as an insulating film. . The sample formed by this method (hereinafter referred to as LB film) has the possibility of satisfying the conditions required for an insulating film when forming the above-mentioned MIS junction (by selecting the film-forming molecules used). Because of this, it is attracting a lot of interest.

There are two known examples of MIS type light emitting devices using this LBI as an insulating film for MIS junctions.

One is L of stearinic cadmium on an n-type GaP substrate.
It is a light-emitting element in which B Mu is cumulatively formed (Thin Solid Films).
) 99.283 pages (1984)). Fatty acids generally have poor mechanical strength and thermal resistance, and the applied withstand voltage is not necessarily high, so they are not satisfactory as insulating films. However, they are easy to form into LB films, and the film thickness depends on the molecular length. (more than about 25 in the case of stearic acid).

The above-mentioned light emitting device uses the LB film of this fatty acid, and its luminous efficiency increases as the film thickness increases, reaching 200 to 2
The film thickness reaches its maximum at 50 people. However, this light-emitting element has unstable characteristics, poor durability, and has drawbacks in that the luminous intensity is greatly attenuated after short-term operation.

One example is a MIS type light emitting device constructed by cumulatively forming an LB film of a phthalocyanine derivative on an n-type GaP substrate (Electronics Letters (E 1e)).
ctronics L etters) 20
.

＼0.12.489 page (1984)), J
5 then L B K! The luminous efficiency is 8 with a height of 57 people.
．． The maximum value is 6X10-3%. This value is comparable to that of a pn junction element. Also, this is 40 pieces per piece.
This is equivalent to forming a human silicon molten model on a GaP substrate, and it operates quickly as an injection type device having an MIS structure. The phthalocyanine used as the LB film has unique thermal stability among various organic substances.

However, although the MIS type light emitting device developed by 1q is slightly improved over the one using the stearic acid LB film,
Changes in luminous efficiency over time; 1. The instability of the 'f property has been observed, and there are many problems to be solved for practical use.

For the above reasons, there is a strong demand for the development of an insulation R'A for MIS type light emitting devices that has a small number of traps W and is stable over time.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and is an MIS type light-emitting element (2-layer organic light-emitting element) in which an MIS junction is constructed using four organic films as insulating films, and the stability of luminous efficiency and characteristics is improved. purpose.

(Summary of the Invention) The present inventors have discovered that LB as an insulating film of a MIS type light emitting element.
As a result of extensive research into organic materials that can form films, especially LB films, we have found that when a BM material containing an addition polymer with delocalized π electrons in its side chain is used, It has been found that luminous efficiency, stability of eight characteristics, and stability over time are significantly improved.

That is, the present invention is characterized in that 1) an 1-B film of an organic material containing an addition polymer having delocalized π electrons in its side chain is used as an insulating film of an fvl IS type light emitting device;

The addition polymerization polymer used in this Komei is a general term for polymers produced by addition reactions of carbon-carbon unsaturated bonds, and polymers that have substituents with delocalized π electrons in their side chains. . The addition polymerization polymer contributes to stabilizing the characteristics of the MIS structure, and the presence of delocalized π electrons reduces the ionization potential of the organic thin film, increasing the hole injection efficiency from the metal side of the 4IS structure to the semiconductor. This contributes to an improvement in luminous efficiency.

Here, examples of the redeemable group having delocalized π electrons include those listed below.

``H2 CI, C = 0 flll]t +) [In cases where it is difficult to form an IB film as a single-layer polymer by itself, it can be accumulated by using other adult molecules in combination. Examples of the nine molecules that make up such a song include stearic acid, araxic acid, behenic acid, and vinyl stearate. 〕ruυ
1 go (yu, preferably 0 to 70 weight M%: 1 go,
More preferably, the weight should be less than 50% by weight and 11%.

Metals used in the ~11S'l'1 light emitting device of the present invention include Au, Ni, etc.
, Cu.

Cr etc. are preferable. Au is particularly suitable.

Further, as a semiconductor of the MIS type light emitting device of the present invention, 1,
'1. Are you using Bridgman method, vapor phase growth method, liquid phase growth method, etc. for public use? GaP and GaN grown by humans.

This can be achieved by using compound semiconductors such as SIC, ZnS, and Zn5e.

The MIS device of the present invention can be manufactured, for example, as follows.

Surface cleaning α filling (SH) of the semiconductor 1<
After applying this treatment, it is placed inside the B-shaped heel. The subface aqueous phase is maintained at a predetermined DI, temperature, and metal salt concentration, and a monomolecular film layer is formed by dropping an open solution of an organic substance containing an addition polymer onto the water surface. Expand. Thereafter, while maintaining the monomolecular film at a predetermined surface pressure to form a condensed film, a vertical pulling method or a horizontal deposition method is applied multiple times to accumulate an LB film of a predetermined thickness on the substrate. Then, for example, N2. After sufficiently drying the substrate in an inert gas atmosphere such as Ar, the substrate is placed in a cooling device, and a predetermined metal is vapor deposited on the LB crotch through a vapor deposition mask having an appropriate pattern to form an electrode.

(Effects of the Invention) According to the present invention, the luminous efficiency is improved and the dynamic characteristics are stabilized by using LB, 9, containing an addition polymer having delocalized 7'c electrons in the side chain as an insulating model. It is possible to provide a MIS type light-emitting device with improved performance.

[Embodiments of the invention]

Practical Problem Example 1 An addition polymer represented by the following formula % (2), i.e., polyvinylcarbazole, was flooded with stearic acid at a weight ratio of 1:1, and this was added to a chloroform solvent at a concentration of 1 tn g mλ. LB membrane and developing solution were prepared.

Using a commercially available LSI'lJH device, set the conditions from 1 to rough.
After setting -1=6.0, water temperature of 15° C., and 211IIi cadmium salt concentration of 0.05 mM, the n-type GaP wafer was placed in Cera 1 in the chamber. The n-type GaP wafer is N'
Doped with Q I After that, the GaP wafer was pulled at a pulling rate of 0.5.
It was pulled up at a rate of 5 m/min, and 1 m of LB was accumulated.

After drying this GaP wafer in a dry N2 atmosphere, about 200 U electrodes were formed on the LB film using a conventional vacuum evaporation apparatus.

FIG. 1 shows the MIS type light emitting device thus obtained. 11 is a GaP wafer, 12 is an In-Ge electrode, 1
3 HaL B B9.111 HaA LI I tl.

This light emitting element had an emission peak of 565 nm and was stable with good current-voltage characteristics. Applied voltage 5
Luminous efficiency at V (7B current value 25mA) is approximately 0.3%
Met. In addition, the initial luminous efficiency was maintained for about one month, and it was confirmed that the product had excellent stability over time.

A MIS type light-emitting device was fabricated by using a Zn5e double-layered substrate having a rounded substrate doped with about 50 ppam of Δ, and by forming a five-layer LB film in the same manner as in Example 1.

FIG. 2 shows this MIS type light emitting device. 21 is Z n
S e Ux-ha, 22 is 1n-Qe electrode, 23 is LB
24 is the AIJ main electrode.

In this light emitting element, an emission peak of 465 nl was observed, and the current-voltage characteristics were also stable. The luminous efficiency at an applied voltage of 5 V (current value 40 mA) was approximately 0.35%, and it was confirmed that this initial luminous efficiency was maintained for approximately one month.

[111] An MIS type light emitting device was manufactured under the same conditions as in Example 1 except that a compound represented by r2 formula % formula % was used as the addition polymerization polymer.

This light emitting element has a luminous efficiency of approximately 0.35% at an applied voltage of 5 V (current of 50 mA), and this luminous efficiency is approximately 1.
Maintained for months.

[Brief explanation of drawings]

FIG. 1 is a diagram of an MIS type light emitting device according to an embodiment of the present invention, and FIG. 2 is a diagram of an IIS type light emitting device according to an embodiment of the present invention. 11 ・GaP wafer, 12-In-Ge electrode,
13-LB film, 14-Au electrode, 21-ZnS
e wafer, 22-1 n-G e 714 poles, 23
-L B III, 24...A (J electrode.

Claims (1)

[Claims] In an MIS type light emitting device having a metal (M)/insulator (I)/semiconductor (S) junction structure and using an organic thin film as the insulator, the organic thin film has delocalized π electrons in side chains. Langmuir containing an addition polymer with
An MIS type light emitting device characterized by using a projector film.