JPS60211798A - Electroluminescent element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electroluminescent device (ELJ device)
The present invention relates to a structure in which a .degree. C. light emitting device 1- is formed on a substrate via a buffer layer having a low resistance.

[Technical background of the invention and its problems]

EL elements are well-known5, including ZnS, Zn5a, and Cd.
5f) MrL%Cr, TCEr, T, Y, as active substances that form luminescent centers in group ■~■ compounds such as
Using a thin film doped with transition metals such as Is and rare earth metals,
Luminescence is obtained by causing electrons to collide with a luminescent center by applying an electric field. Conventional EL hydrogen molecular structures include the following.

(α) An electroluminescent element with an active substance added to the matrix (an insulating layer is provided above and below the EL hydrogen atoms; it is an AC-driven type in which the luminescent center is excited by the collision of electrons when an AC voltage is applied, and the driving requires 1000 V-IOOV). Requires high voltage.

(J) It is a DC drive type in which an EL hydrogen element is provided in contact with the electrode film, and when a DC voltage is applied, electrons injected from the negative electrode side into the KL thin film collide and excite the luminescent center to emit light.
A material obtained by adding an active substance such as M to a base compound such as nsm is heated on a glass substrate using a resistance heating method.
This is a transparent electrode film made of 5°8302 (so-called ITO) that is deposited by vacuum evaporation.
Unless the thickness of the L thin film is 5000A or more, no light will be emitted and high brightness will not be obtained. This is considered to be because the EL thin film does not exhibit sufficient crystallinity when the film thickness is less than 000X. In order to apply an electric field that enables collisional excitation by electrons in a thick EL thin film of about 5000 A or more, a considerably high voltage is required, and the threshold voltage for one shot is at least 2 (1'°C).

A KL thin film consisting of a lattice-matched zns, -M, single crystal layer is grown on a single crystal substrate of (clG(lA#) or Ge using the molecular beam epitaxial growth method.

Since this EL thin film is thin and has good crystallinity at a temperature of .degree. C., it is possible to obtain an element capable of emitting light with high efficiency and high brightness at a low threshold voltage of around 5V. However, the substrate material is GaA.

Single crystals of Ge and Ge are extremely expensive, and large-area crystals are difficult to obtain. Furthermore, although GaA# is a single crystal, the surface of the substrate is occupied by crystals due to processing, so the Zn8g-Mn layer in contact with the substrate is smaller than when an amorphous glass substrate is used. However, there are also problems in that the crystals are easily disordered and the brightness decreases near the substrate.

(d) Research has also been conducted on using glass as an inexpensive substrate and forming a ZnS, -Mn single crystal layer on this glass substrate by molecular beam epitaxial growth via an ITO electrode film. ZNS directly on glass substrate
In order to form the same Mn crystal layer, the crystal lattice is well-organized and a sufficient thickness is required to obtain good luminescence, so the thickness of one luminescent layer is increased, and the active substance Mn, which is the luminescent center, is added to the entire layer.
Although the ZNSG is dispersed, the crystallinity of the ZNSG in contact with the amorphous glass substrate is poor and the disorder of the crystal attenuates the brightness, so even if Mn near the substrate emits light, it increases the brightness. The problem is that it is not possible.

tg+ Z, S via ITO electrode film on glass substrate.

Form a buffer layer mainly composed of Z
There is a method of increasing the brightness at a low voltage by adjusting the crystallinity in the buffer layer by forming an nS, -Mn light-emitting layer.
There is a way to add. However, since the presence of the buffer layer increases the electrical resistance by the thickness thereof, there is no point in providing the buffer layer unless this is made as low as possible. Furthermore, if the amount of G added is increased, the resistance will be low (although there is a problem that the crystallinity of z?&s# will be impaired).

[Purpose of the invention]

In view of the above-mentioned problems, the present invention is based on a compound of group 1 to 2, such as z1%S-, on a substrate, and B to lower resistance.
, AI, In, and Tj, and on this buffer layer, a light-emitting layer was formed in which an active substance serving as a luminescent center, for example, M, was added to a compound of the ■~■ group, for example, znS-. As a result, the crystallinity is adjusted using a buffer layer with low resistance, and the light emitting layer is formed at the position where the crystallinity is the best.The thickness of the light emitting layer is reduced to enable operation at low voltage and to emit light with high brightness. That's what you're trying to get.

[Summary of the invention]

In the present invention, compounds of groups 1 to 2 are mainly formed on a substrate, and K B , A1. A buffer layer is formed to which a conductive substance made of either In or TA' is added.

On this buffer layer, a light-emitting layer is formed by adding an active substance that becomes a light-emitting center to a group 11-III compound, and the low-resistance buffer layer adjusts the crystallinity, and the light-emitting layer is formed at the best position of crystallinity using a low voltage. It is something that forms.

[Structure of the invention]

The substrate used in the present invention is glass.

Examples include GaA, single crystal, and Si single crystal. Used for buffer layer. The thickness of the buffer layer needs to be 0.3 μm or more.

If the buffer layer is thin, the crystallinity will be poor due to lattice mismatch and impurity mixture, and if the buffer layer is thicker than 2 μm, the electrical resistance will increase and the voltage required for light emission will increase. Examples of conductive substances added to lower the resistance of the buffer layer include B and Al.

There are In and TI, and if any of these seeds become brittle, the crystallinity of znS will be poor. Furthermore, the same compound as that for the buffer layer is used as the compound of groups 1 to 2 for the light emitting layer, and 0.1% to 0.5% of Mn as an active substance is added. The active substance is Mn, “r s
There are Tb*Ers, Tmb, Yb, etc. The thickness of the light emitting layer is 0.5 μm - 0.2 μm or less, the brightness will be low, and if it is 0.6 μm or more, the brightness will be high but the required voltage will also be high. In addition, as an electrode, if the substrate is glass, 1n20s between the substrate and the buffer layer, 5
A transparent electrode made of ITO made of n02 is used.

When the substrate is GaA, the buffer layer is formed directly on the *GaA# substrate.

[Embodiments of the invention]

Next, the present invention will be explained in detail.

Example 1 As shown in FIG.
A 0.3 μm thick buffer 7 made of μm ITO transparent electrode film (2) and ZfiS doped with Its for low resistance.
Layer 13).

thickness o of ZfiS- doped with Mn0.11;
uttm luminescent layer +41. An electrode layer (5) having a thickness of O0 is sequentially formed by Al vapor deposition. The buffer layer (3) and the light emitting layer 14) are made of Zs, Sg, Mn
, I% of each element was formed independently by molecular beam epitaxial growth.

Next, a method for manufacturing an EL element having the structure of Example 1 using a molecular beam epitaxial growth apparatus will be explained with reference to FIG.

This growth apparatus itself is well known, and the substrate (1) is placed in an ultra-high vacuum Pelger (71), and the constituent elements of the thin film to be grown are individually exposed to Zr&, 8...M, . The molecular beam generation cells +81 +911 (l) are charged in 1 ull, and the molecular beam from each cell 181191001 ttll is irradiated onto the substrate Ill to perform growth. Each cell +81191110111υ is surrounded by a shroud of liquid nitrogen ( 121 and is cooled.

Unwanted steam from the surrounding area is prevented during growth. U is a shutter, which is configured at 5° C. so that molecular beam growth can be performed on the substrate ttll only for a required period by external operation. The substrate... is, for example, an ITO-coated glass substrate with a thickness of 0.2 μm, and is placed on a temperature-controlled substrate holder (141) equipped with a heater in the single molecular beam growth apparatus. The temperature of is 550C
2LS, -1N buffer layer 131. Zn
Growth of the S, -Mn light-emitting layer (4) is performed sequentially. In the molecular beam cell (81f9+ffα[]J, Z3.
Ss, Mn, and I are arranged as single elements, and the temperature is controlled by independently attached heaters, and the Zn cell (
8) is 5#OU, 8g cell 19) is 160-170C
, Mn cell +1 (l is 600C, I cell συ is 300
It is kept at C. The degree of vacuum in the Pelger (71) during growth is preferably about 10 Torr or less, but
No significant difference was observed in the results even at ORR level. Next, the light emitting layer (4) is covered with an AI electrode film (5) by vacuum deposition.

Example 2: The one shown in the figure is on a single-crystal GaAs substrate 11+.

Buffer layer 131 made of In-doped Z and S
, Mn-doped Z, a light emitting layer (4) consisting of 8 g is sequentially formed by molecular beam epitaxial growth, and the substrate il+ and the light emitting layer (4) are connected to electrodes A, -G, and -electrode α9, respectively.
and Aμ electrode (161) are formed by vapor deposition.

[Experimental example of invention]

Example 1 in which In was added as a conductive substance to the buffer layer
In Example 1, I
Ga instead of n1C! The results of comparing the brightness of the added EL element (II) and the EL element (J) in which no conductive substance was added to the buffer layer in Example 1 while changing the thickness of the buffer layer are compared. The method of the experiment was to measure the brightness of the element using the short circuit current of the receiver <Si solar cell), and express it as the ii element efficiency.

From this contradictory diagram, it can be seen that (I) in which the conductive material In is added to the buffer layer has the highest efficiency<b, and (1) in which Ga is added is slightly inferior.

In the case of (I) with no conductive substance added, the effect of interposing the buffer layer is hardly visible.

〔Effect of the invention〕

According to the present invention, seven buff layers are formed on a substrate, which are mainly composed of compounds of groups 1 to 2 and to which a conductive substance made of any one of B, AI, In, and Tl is added to reduce resistance. Since the light-emitting layer is formed by adding an active substance that becomes a light-emitting center to the Klf (~■ group compound) on the buffer layer, the light-emitting layer is formed at the position where the crystallinity of the buffer layer formed on the substrate is the best. This makes it possible to improve the crystallinity of the light-emitting layer and obtain high-intensity light emission, and since the crystal lattice of this light-emitting layer is matched, the thickness of the layer can be made as thin as possible.

Also, the buffer layer button is B for lower resistance.

Since the conductive material made of any one of All, In, and TI is added, the resistance value does not increase even with the presence of a buffer layer, and together with the ability to form the above-mentioned 'e layer thinly, light emission is improved. Threshold voltage can be lowered.

[Brief explanation of the drawing]

Figure 1 is an enlarged sectional view of an electroluminescent element showing an embodiment of the present invention, and Figure 2 is a diagram of the same. (l)0.Substrate, (3).Buffer layer, 14).Light emitting layer. Thickness of 1 layer of buff (7”m)

Claims (1)

[Claims] B, A1. mainly composed of ■~■ group compounds on the Ill substrate to reduce resistance. A buffer layer is formed to which a conductive substance consisting of one of L% and T/ is added, and a light-emitting layer is formed on this buffer layer by adding an active substance serving as a luminescent center to a Tol group compound. Electroluminescent element.