JPS63175485A - Thin film light-emitting element - Google Patents

Abstract

PURPOSE:To make it possible to form GaAs films having an excellent crystallizability on an insulating substrate by a method wherein an insulator intermediate layer is provided on the single crystal substrate consisting of a metal and moreover, the P-type and N-type GaAs films are provided on its upper part. CONSTITUTION:An insulative fluoride film 2 is formed on a single crystal metal plate 1 consisting of such a metal as Fe, Ni, Al, Cu, Co and Cr, which can be matched with fluoride with respect to the thermal expansion coefficient to obtain a substrate. Thereby, the warpage of the substrate is prevented and the defect in the film 2 is eliminated to form GaAs films 3 and 5 having an excellent crystallizability thereon. The dielectric strength of fluoride is 10<5>V/m or more, the fluoride has sufficiently insulating properties and a strong orienta tion property, the single crystal fluoride film 2 is obtained on the single crystal metal plate 1 and moreover, the single crystal GaAs films 3 and 5 are easily grown on the film 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical printer head that records information optically, a display head that optically displays information, and a head that has both optical and semiconductor functions. Regarding optical IC.

Poor conventional technology] Various optical printers have been released for the purpose of high speed, low cost, and compactness.These include laser beam printers, liquid crystal printers, and LED printers. It has the advantage of being extremely fast and capable of high recording density, but it uses a rotating polygon mirror that rotates at high speed to deflect the laser beam and perform optical scanning.
This method modulates this light beam according to the information signal and applies it to the photoreceptor to be recorded to form a recorded image, which has the drawbacks of a large writing volume, high power consumption, and a high price for the entire device. be.

In addition, in LBP, the rotating polygon mirror has no jitter and no defocus on the recording surface, and in order to form a laser beam, it requires not only optical precision but also high mechanical and electrical precision such as the rotation servo of the motor. I needed the means. On the other hand, a liquid crystal printer has the advantage of a light source (fluorescent lamp LBP 115). However, the printing speed is extremely slow (for example, LBP 1
/20) and low recording density (2/3 of LBP).

On the other hand, the 0-hydraulic type, which uses a light emitting element (LED) array as an optical printer head, has no moving parts, just like the LC case, and only has the LED array and driving IC mounted on the board, so the overall performance is The volume of is 1/15 of LBP
It can be made extremely small, and the printing speed is also fast.
(1/2 to 1/3 of LBP) and high recording density (same or higher than LBP).However, in LED arrays, many LED chips are manufactured separately from the substrate, and then glued onto the substrate and connected to the recording head. Therefore, precise alignment is required to obtain the accuracy of the scanning line, and since each chip is glued separately, it causes "unevenness" in the light, and the thin film (7) on the substrate is
Ga As is formed by MOCVD, MBE, or liquid phase growth, but the size of the single crystal substrate is about 2 to 3 inches at most, and furthermore, this substrate has a high density of defects such as dislocations. Therefore, since an extremely high density of defects is introduced into the grown GaAs film, the luminous efficiency changes depending on the location. In addition, the price of GaAs single crystal substrates is extremely high.

Another disadvantage is that the price of the entire device cannot be lowered.

However, if it were possible to form light emitting diodes on Si substrates, sapphire substrates, etc., which are inexpensive and have extremely low dislocation density, instead of GaAs single crystal substrates, it would be possible to create LED printers and displays that do not have these drawbacks. It is believed that three-dimensional optical ICs can be manufactured at low cost. For this reason,
At each research institute, Si is deposited on Si single crystal as shown in Table 1.
After providing Ge whose lattice constant is very similar to that of G a A
Method (1) of growing GaAs itself and Si
A method (2) of providing a multi-layered layer on top and further providing a GaAs light-emitting screen on top is being considered.

Table 1 However, in method (1), the lattice constants of Ge and Ga As formed on top of it are quite different; (Table 1
), a large number of defects such as dislocations are introduced into GaAs, resulting in extremely poor luminous efficiency.

In the case of method (2), since it is necessary to laminate multiple GaAg layers, there are drawbacks such as requiring time and introducing a large number of dislocations due to different lattice constants.

Furthermore, as an intermediate layer, a CaFz film having a lattice constant similar to that of Go is formed on Si by vapor deposition, and GaAs is formed on top of the CaFz film (H, l5hi).
hara et, al: Mat, Res, Symp, P
roc, 25pp.

393-403) are also being considered. However, CaF
Since the coefficient of thermal expansion of z is five times that of Si, it has the disadvantage that it causes large warpage and the GaAs film formed on top of it also contains many defects.
No examples have been found in which a GaAs film with excellent crystallinity is formed on an insulating plate.

In addition, related to this type of technology.

For example, there is Japanese Patent Application Laid-Open No. 59-182582.

[Problem that the invention seeks to solve]

The object of the present invention is to provide a high-density, substrate-integrated optical printer head that does not require mechanical scanning by manufacturing a thin film light emitting device.

The conventional manufacturing process for LEDs is to create a light-emitting junction of GaAs, etc. on a GaAs substrate using liquid phase or vapor phase epitaxial growth technology.* The size of the GaAs substrate is The maximum length is three inches. Therefore, it is impossible to fabricate on a single substrate a length that can accommodate the document surface required by an optical printer, and a single optical head has been formed by performing multi-wave bear alignment of a plurality of light emitting diodes.

On the other hand, recent advances in thin film technology have made it possible to produce high-performance GaAs thin films by 1M0CVD or LBE.
Attempts have been made to form s thin films. However, if the lattice constants between the substrate made of different materials and the thin film formed on the substrate are different, then the stain may be due to the introduction of a large number of dislocations into the grown film, or the formation of polycrystalline stains. 1,4
In order to prevent the 6.3° potential, it is necessary to form an intermediate layer between the insulating substrate and the grown film to alleviate the lattice strain, and for this reason, Ge, CaFx, etc. are being considered. ing.

but.

Ge has a large difference in lattice constant from Si as shown in Table 1, and although the lattice constant of common compounds matches that of Si, as mentioned above, the difference in thermal expansion coefficient from Ge is large and it is difficult to use large areas. In printer heads that require an intermediate layer, a large "warp" occurs after the film is formed, and this causes f
S & fine cuticle cracks result in defects such as dislocations.

[Effect]

The thermal expansion coefficient of metal plates such as Cu, AQ, Few Ni, and Go is in the range of 12 to 26 x 10'-'/'C,
It is close to that of a common creature (17.5 x 10""8/"C).

Therefore, even if a fluoride film is formed on a metal plate.

Compared to the case where the film is formed on Si (3,5 x 10-''/°C), warping can be almost eliminated and defects are hardly introduced into the fluoride film.

In addition, G a A formed on the fluoride film/single crystal plate
The mismatch in lattice constant with the s film is caused by CaFz and SrF2
It is possible to almost eliminate it by controlling the blending composition.

[Means for solving problems]

The present invention has been made in view of the above-mentioned problems, and includes Fe, which can be matched with the coefficient of thermal expansion of the fluoride.
An insulating fluoride film is formed on a single crystal metal plate such as Ni, AQy Cu, Co, Cr, etc., and used as a substrate to prevent "substrate warpage" and eliminate defects in the fluoride film. The aim is to form a GaAs film with excellent crystallinity.

The dielectric strength voltage of the common compound is 10'V/m or more, and it has sufficient insulation properties.

Furthermore, fluorides have strong orientation, and a single-crystal fluoride film can be obtained on a single-crystal metal plate.

Furthermore, on the single crystal fluoride film, single crystal Ga A
s film grows easily.

〔Example〕

The present invention will be explained below using examples.

Figure 1 shows vacuum evaporation (10-7To) on the 5i (111) plane.
CaFx film (intermediate layer) by 0.1 to 0.5
μm and on a Cu(111) single crystal plate.

Similarly, the figure shows the warping of the substrate when a CaFx film is attached by vacuum evaporation. It can be seen that the warpage of the CaFz/Si substrate becomes larger as the CaFx film becomes thicker, but there is almost no warping of the CaFz/Cu substrate. However, the diameter of the substrate is Sow.

FIG. 2 shows the influence of the coefficient of thermal expansion of the metal plate on the warpage of the CaFxl gold plate. The coefficient of thermal expansion of the metal plate is l0
It can be seen that when the temperature exceeds 6°C, the warpage almost disappears.

Figure 3 shows ■CaF on Si obtained by MBE in Figure 1.
When a 1 μm thick G a As film is formed on the x film, ■
In order to examine the crystallinity of each GaAs film in the case where a 1 μm thick GaAs film is formed on a CaF film on Cu, the photoluminescence intensity and its values are measured.

As is clear from the figure, the crystallinity of the GaAs film when grown on the CaFz film/Cu is
It is preferable that it be similar to a GaAs film grown on a substrate. Furthermore, the crystallization property is the worst when grown on CaFz/Si.

FIG. 4 shows an embodiment of a semiconductor light emitting device. Vacuum deposition (10″″7) on Cu single crystal (111) substrate
Torr) to deposit a CaF2 film with a thickness of about 0.1 μm, then apply MBE to a temperature range of 600 to 700°C to deposit P-type Ga As and then n-type Ga As to approximately 4 μm.
Added μm. Next, as shown in the figure, after patterning and forming Au electrodes, the device is connected to a driver by wire bonding to emit light from the top of the device. Cu and CaF
The coefficient of thermal expansion of x film is 17X10-'/”e, respectively.
17.5X10-8/℃, which is almost the same, so
There is no warping of the board.

Also, instead of CaFx, a mixture of CaFz and Sr''12 ゛,... ]・film (CaFz(1-x)SrFx x=o~0.
6) But that's fine.

FIG. 5 is a basic configuration diagram of an optical printer head according to the present invention. In FIG. 0, reference numeral 31 denotes a substrate that serves as a substrate for a GaAs LED array, and a smooth flat surface such as sapphire or Si is used. Reference numeral 32 denotes an LED array, in which each dot in the grid corresponds to a light emitting part, is electrically separated from adjacent dots, and is configured to be able to emit light independently, depending on the number of pixels required on the same substrate. The pixel density also corresponds to the recorded information. Reference numeral 33 denotes a driver element for driving each LED array 32, which is usually a driver with a transistor and a latch circuit added thereto, and the driver section has a transistor or MOS driver circuit added thereto. 34
．． 35 conceptually shows this wiring pattern. This wiring is mainly done by wire bonding, but solder reflow connection may also be used.

FIG. 6 is an example of an optical printer to which an optical printer head, etc., mounted with the LED, driver array, etc. shown in the embodiment of FIG. 5 is applied. 1 is a photosensitive drum made of Se, '5eTe, or a composite thereof.

It is composed of A-8i, OPC, etc., and is made using technology in the field of general electrophotography.

Reference numeral 2 indicates a charger for applying charge to the surface of the photoreceptor, and reference numeral 3 indicates an optical printer head of the present invention. It is exposed to light in accordance with an information signal, the charges are erased in accordance with the information, and an electrostatic latent image is formed by the remaining charges. This electrostatic latent image is immediately developed by a developing roller 5 to which a developer 6 is attached by a developing device 4, and becomes a toner image 7. On the other hand, the recording paper 9 is stored in the paper feed cassette 8, and is pressed against the paper presser foot 11 by the paper presser spring 10 according to the number of remaining recording sheets, and when the paper feed roll 12 is operated, the paper is recorded one by one. Paper is fed. The recording paper driving rolls 14 and 15 are charged by the charger 17 at almost the same speed as the rotation of the drum 1, and the developed image 7 is transferred to the recording paper, so that no unnecessary charges such as flash discharge remain, and the transfer charger is The image is transferred through the static eliminator 18 which is placed at a position where the effect can be fully exerted, and the transferred image 19 is placed on the paper feed guide roll 20 before entering the heat fixing roll 21. Since the transferred image 19 is unfixed, fM
Since the image will simply be taken, sufficient care must be taken when designing guides, etc.

The papers 22 are stacked one after another on a recording paper stacker 23. On the other hand, since a small amount of residual developing material remaining after transfer remains on the photosensitive drum 1, a static eliminating light source 2 is used to remove the residual charge.
5, the developer passes through the residual developer removing section 26, is scraped off by the scraping plate 28, and accumulates in the removing section 26 as residual developer 27. In this state, the drum surface is in a cleaned state 29 and returns to a state in which it can be reused.

〔Effect of the invention〕 [Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the CaFz film thickness and the warpage of the substrate to explain the present invention, Fig. 2 is a diagram showing the relation between the thermal expansion coefficient of the substrate and the warpage of the substrate, and Fig. 3 is a diagram showing the relationship between the CaFz film thickness and the warpage of the substrate. A diagram showing the luminescence intensity and its half-width, Fig. 4 is a cross-sectional view showing an LED according to an embodiment of the present invention, Fig. 5 is an explanatory diagram showing the structure of the head, and Fig. 6 shows an LED printer. It is a structural diagram. 1-Cu, 2-CaFx, 4-Au, 6
...Protective film, height 1 figure CαF2 film, 1. (μ゛m) Fu2-Nitto 3 map board 1st class 5th Hidaka 6 diagram

Claims (1)

[Claims] 1. In a thin film light emitting device having a structure in which an intermediate layer is provided on a crystalline substrate, and p-type and n-type GaAs films are further provided on top of the intermediate layer, the crystalline material is a single crystal of metal; , a thin film light emitting device characterized in that the intermediate layer is an insulator.