JPH04156518A - Manufacture of space light modulation element and thin film - Google Patents

Abstract

PURPOSE:To perform stable light switching and realize a high-speed action by laminating a stratified compound connected to a light conducting layer in the c-axis direction with the van der Waals force to constitute a space light modulation element. CONSTITUTION:A transparent conducting electrode 102 is formed on a transparent insulating substrate 101, a stratified compound 103 and a light conducting layer 104 are laminated on it, and a transparent conducting electrode 105 is formed. The stratified compound 103 is made of materials such as GaSe, GaS, PbI2, HgI2, InSe, InS, GaTe, HgTe, BiI2, CdI2, or it may be made of a single material among them, or two or more kinds of materials may be laminated. The material used for the light conducting layer 104 functions as a dielectric substance in darkness and loses the characteristic of the dielectric substance by photoconductivity when light is radiated, and an amorphous semiconductor made of at least one kind of element selected among C, Si, Ge and containing hydrogen is used for the material.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a spatial light modulation element used in an optical processing device or a projection type display, and a thin film manufacturing method for obtaining a high quality thin film. Technology Spatial light modulator (Yo) It is an important element for realizing optical operations such as optical logical operations and optical neurocomputing.
A photoconductive layer made of CdSe, BSO or hydrogenated amorphous silicon (hereinafter abbreviated as a-3i:H) and a ferroelectric liquid crystal or twisted nematic liquid crystal are laminated together. The halide epitaxy method has been reported as a method for producing thin films of group compounds (Tera L.
](tl!,,′,: Yabanese Journal of
Applied Physics Volume 28 No. 12 1989
Year L2134 L21.36 pages, N, Ter
aguchjet a, ], Jj, A, P
2j8 (1,2n (+989) L2+34-L2
+36. reference).

Problems to be Solved by the Invention In the spatial light modulator described above, since the switching operation electric field of the liquid crystal layer is as high as 101 to 10 SV/c+n,
The electric field applied to the photoconductive layer becomes equal to or greater than that. For this reason, the dark current in the photoconductive layer increases,
There is a problem that the liquid crystal layer switches even in the dark, making it impossible to operate correctly.
In the production method of Vl group thin films, those with a zinc blend structure are easy to grow, and even if mica is used as a substrate, a layered structure of II
There was a problem that I-Vl group thin films did not grow.Surprisingly, many functional devices operate by applying an electric field (mica is an insulating substrate).
Another problem is that it is difficult to apply a sufficient electric field to the layered structure, making it difficult to fabricate a functional device. The only way to obtain a thin film with a layered structure was to peel a crystal grown by a method such as the Brillant-Man method into thin layers between the folds.
Alternatively, it is difficult to form a veterinary junction in which different types of thin films are laminated in multiple layers, and it is difficult to create a functional element that takes advantage of the characteristics of the layered structure. , the present invention (provides a spatial light modulator that operates in a very low electric field, and also provides a spatial light modulator that can be used on a conductive substrate that can easily apply an electric field to a layered structure).
The present invention provides a method for growing a thin film having a layered structure.

Means for Solving the Problems In order to achieve the above objects (2) The spatial light modulator ζ of the present invention has a structure in which a photoconductive layer and a layered compound in which the C-axis direction is connected by van der Waals force are laminated.

In the thin film growth method of the present invention (G a S e, G a S, P b I 2
．． HgT2. In S e, I n
S, G a T e, Hg T e, B
A thin film made of at least one selected from IIz and Cdl1 is produced by a vapor phase growth method.

Working Layered Compound 11 The direction parallel to the c-plane is a covalent bonding force (the C-axis direction is bonded by a weak van der Waalska. Therefore, in the case of a single material, L van der Waals gap It can be regarded as a pseudopolarized superlattice with confinement, and electrons, holes, and excitons combined with them are confined two-dimensionally within the layer.

In addition, excitons have a large binding energy and can exist stably even at room temperature.

When an external electric field is applied to such a layered compound, the absorption spectrum of excitons shifts to longer wavelengths. This is a phenomenon in which light of a certain wavelength is transmitted in the absence of an electric field, but is absorbed and not transmitted when an electric field is applied. shows. Moreover, such optical modulation requires a low electric field of about 1o3v/cm and can operate at high speed.

Therefore, when a spatial light modulator is constructed by combining such a layered compound and a photoconductive layer, the electric field strength applied to the photoconductive layer is small, and stable optical switching can be performed and high-speed operation can be realized.

Also, such layered compounds such as GaSe, Ga
In the case of III-Vl group compounds such as S, this crystal structure has one closed-shell structure with four layers of VI-III-111-Vr. When producing a III-VI group layered thin film, one group VI atom is After layer lamination, group III and ■■
Two layers of group atoms may be stacked. When vapor phase growth is used, a gas containing group III elements and a gas containing group Vl elements are alternately flowed onto the substrate, and the amount of adsorbed atoms or molecules on the substrate surface is controlled by controlling the substrate temperature. Although it is possible to deposit atomic layers one layer at a time or two layers at a time, this method can be used to deposit materials other than layered compounds, such as metals or IT, since the thin film is layered.
Crystals can be easily grown on conductive substrates such as O.Example: Examples of the present invention will be described with reference to the drawings. Fig. 1 shows an example of the spatial modulation element of the present invention. 1st
The figure shows an example of a transmission type.

Element configuration (i.e. transparent conductive electrode (e.g. ITO, Snow, etc.) on transparent insulating substrate 101 (e.g. glass plate)
A layered compound layer 103 and a photoconductive layer 104 are laminated thereon, and a transparent conductive electrode 105 is further formed.

The operation of the spatial light modulator will also be described. Light is irradiated from the transparent conductive electrode 105, and the transparent conductive electrode 1
It is assumed that the external voltage V is applied between 02.105 and 0.02.105. Before irradiation with light, the electrical impedance of the photoconductive layer 104 was large. Even though the voltage V is mainly applied to the photoconductive layer 104, when the photoconductive layer 104 is irradiated with light, the electrical impedance of the photoconductive layer 104 increases. As a result, the voltage V is applied mainly to the layered compound layer 103.As shown in FIG. Although the amount of light transmitted through the layered compound layer 103 changes, for example, at the wavelength shown in FIG.
3. It is assumed that the light of λ2 is always incident on the transparent conductive electrode 105 as the readout light, and the light of λ1 is used as the signal light. In this case, if the light intensity of λ1 is small, the light of λ2 will be transmitted through the transparent conductive electrode 102\If the light intensity of λ1 is large, the light of λ2 will hardly be transmitted. In the operation of the light modulation element, a photoconductive layer 104 having photosensitivity to λ2 is used (X, and incident light with a wavelength of λ2 is transferred to the transparent conductive electrode 104).
When the layered compound layer 103 is irradiated with more light, the incident light reaches the photoconductive layer 104 when no electric field is applied to the layered compound layer 103, an electric field is applied to the layered compound layer 103, and the light of λ2 is absorbed by the layered compound layer 103. Therefore, light does not reach the photoconductive layer 104. Therefore, the electric field applied to the layered compound 103 decreases, and the λ2 light reaches the photoconductive layer.In this way, by simply irradiating this element with λ2 light of a constant intensity, the above cycle is repeated. Atsushi
The transmitted light from the photoconductive layer 104 is pulsed. Therefore, this spatial light modulator also operates as a light pulse generator.

Here, the layered compound layer 103 is made of GaSe or GaS.

P b I 2. Hg I *, I n S
e, I n S, G a T e.

It is composed of materials such as HgTe, BiIa, and CdIt, and may be composed of a single material among these, or
, two or more types of materials may be laminated.

The material used for the photoconductive layer 104 (a material that acts as a dielectric in the dark and loses its dielectric properties due to photoconductivity when irradiated with light; for example, if, CdS, CdTe,
CdSe, ZnS, Zn5e, GaAs.

Compound semiconductors such as GaN, GaP, GaAlAs, InP, S e, S e T e, A s
Amorphous semiconductor K S such as S e etc. 1. Ge, S
1l-xcx, S l+-xGex.

Polycrystalline or amorphous semiconductor structure of Q 6 +-wCX (0<X<1)? , :, (1) Phthalocyanine pigment (abbreviated as PC), for example, metal-free Pc, XPc (X=Cu,
Ni, Co, Tie, Mg, Si
(OH)2, etc.), AICIPccl, Ti0
CIPcC1, InClPcC1, InClPc,
InBrPcBr natomi (2) Monoazo pigments Azo color blacks such as disazo pigments (3) Penylene pigments such as penylene acid anhydride and penylene acid imide (4) Indigoid pigments (5) Quinacridone pigments (6) Anthraquinones Polycyclic bovine nones such as pyrenequinones (7) Cyanine dark in color (8) Xanthine dyed porcelain (9) Charge transfer complexes such as PVK/TNF (10)
Eutectic complexes formed from biryllium salt dyes and polycarbonate resins and (11) organic semiconductors such as azulenium salt compounds are also amorphous ('), S 1. Ge, S
II-XCX, Sl+-wGex, Ge
I-XC× (hereinafter a-3i, a-G e, a-
5i+-++C++, a-S i+-xGex,
a -Qe+-xCx) is the photoconductive layer 10
4, these materials have a large quantum efficiency in the visible region and are effective. In this case, the inclusion of hydrogen or halogen elements in these materials can further increase the photosensitivity, and can further reduce the dielectric constant and Oxygen or nitrogen may be included to increase resistivity (- p
type impurities such as B, AI, Ga, or n
Elements such as P, As, and Sb, which are type impurities, may also be added. L% By laminating amorphous materials doped with impurities in this way, p/n.

The dielectric constant and dark resistance or operating voltage polarity may be controlled by forming junctions such as p/i, i/n, p/i/n and forming a depletion layer within the photoconductive layer 103.
In addition to these amorphous materials, it is also possible to form a depletion layer in the photoconductive layer 104 by laminating two or more of the above materials to form a heterojunction. The thickness is desirably from 0.01 to 100 μm. An embodiment of the reflective spatial light modulator according to the present invention is shown in FIG. The structure (almost the same as that in Figure 1) consists of a transparent insulating substrate 201, a transparent conductive electrode 202, a layered compound layer 20a, a photoconductive layer 204, and a transparent conductive electrode 205, with the difference being that the layered compound layer 203 and A reflective layer 206 is provided between the photoconductive layers 204. Operation L is basically the same as the transmission type shown in FIG. 205
Human radiation from the side, readout light enters from the transparent conductive electrode 202 side, and the reflected output light is emitted from the transparent conductive electrode 202 side by the reflection layer 206.

In the case of this reflective type, when the intensity of the incident light L increases, the output light decreases, and it functions as a spatial light modulator.

Also, the reflective layer 206 i;L AI, C with high reflectance
r.

The dielectric mirror is formed by laminating a large number of thin metal A such as Ag or dielectric thin films.

In this way, the spatial light modulation element of the present invention can obtain the same operation in both the transmissive type and the reflective type. Specific examples will be described below.

Example 1 A film of ITO with a thickness of 0.1 to 0.5 μm was formed on a glass substrate by sputtering to form a transparent conductive electrode.
After laminating a GaSe film with a thickness of 1 to 3 μm by vapor phase epitaxy using G e CI 2 and H S e, an a-3i:H film was deposited as a photoconductive layer by plasma CVD method.
．． Formed 5~2μm, then 0゜1~0.5μm
A transmissive spatial light modulator similar to that shown in Fig. 1 was fabricated by forming an IT○ electrode pattern with a thickness of m, and a direct current voltage was applied to the spatial light modulator to irradiate the photoconductive layer with light. &G
After confirming that the light with a wavelength of 620 to 6.40 nm that had been transmitted through the aSe film was no longer transmitted, Example 2 An AI electrode array was deposited as a reflective layer 401 on the GaSe crystal prepared by the Bridgman method. After, plasma C
a-5i +-xQ as photoconductive layer 402 by VD method
x: H film (x: O~0.3) was laminated. Next, using cleavage, Ga, S e layers 403 were stacked to 100
After forming a thickness of ~200 μm, facing platinum translucent electrodes 404, . 405 is formed to produce a reflective spatial light modulator array. A cross-sectional view of this is shown in FIG.

In this spatial light modulator, it was confirmed that the transmittance of the GaSe layer 403 changes with respect to the sum of the amounts of light incident on one AI electrode.Example 3: Conductive substrate 501 (glass substrate or semiconductor wafer) GaSe, G
aS, InSe, InS, GaTe.

A schematic diagram of an example of a fabrication apparatus used for vapor phase growth of a group III-VI layered compound such as HgTe is shown.

A conductive substrate 501 (a carbon susceptor 503 placed on a carbon susceptor 503 inside a quartz tube 502)
is heated by an induction heating coil 504 installed around a quartz tube 502, and a gas containing a group III element (for example, Ga(CHs)*, Ga(CPHs), In(Cp
H6)s, Gacla, etc.) was introduced into the quartz tube 502 through the bubbler 505.At this time, as a carrier gas (He, N2.He, Ar, Ne, etc.) was introduced into the quartz tube 502.
Do not use the flow meter 506 to adjust the supply amount.
A gas containing group elements (for example, CHis, HtSe, etc.) is introduced into the quartz tube 502 from a gas cylinder 507 through a flowmeter 508. T
When using a substance with low vapor pressure such as e(CH*)a (
As a substrate heating method using a bubbler in the same way as the III element gas introduction system (an electric furnace may be used instead of the induction coil 504), in the above manufacturing apparatus, a glass substrate on which an ITO thin film is deposited is used. (ITO substrate) is introduced into the quartz tube 502 alternately with GaCl2 and H2S, and a GaS thin film is grown on the TO substrate.
When observed, it was found that it had a layered structure.9 Furthermore, when IT○ electrodes were stacked on this GaS thin film and an electric field was applied between the opposing ITO electrodes, the absorption spectrum shifted to the longer wavelength side. Example 4 Using the manufacturing equipment used in Example 3, a CaF2 film was laminated on an IT○ substrate and a GaS thin film was grown in the same way. It was found that crystals with a layered structure grow over a wider substrate temperature range than when no JLCaF2 film is used.

41 as the cause of this! , the bonding energy between Ca-F of CaFp is very large, and the Ca-F bond is broken and V
This seems to be because group I frozen atoms (in this case, S atoms) become difficult to bond with Ca atoms.

In addition, on this GaS thin film, a
A spatial light modulation element was fabricated by laminating -3i:H thin films and ITO electrodes, and it was confirmed that transmitted light was modulated by irradiating light onto a-Si:H.9 Effects of the InventionAccording to the present invention. A spatial light modulator that can be driven at low voltage and operates at high speed can be obtained, and a method for manufacturing a thin layered compound film that can be easily grown even on a conductive substrate can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a spatial light modulator according to an embodiment of the present invention. FIG. The cross-section of the reflective spatial light modulator in FIG. 4 is shown in FIG. 101...Transparent insulating substrate, 102.105...Transparent conductive electrical machine 103...Layered compound J! 104.
...Photoconductive [301...Transparent insulating substrate, 302.3
05...Transparent conductive type i 303...Layered compound sales 304...Light guiding layer 306...Reflection layer 4゜1
...Reflection 402...Photoconductivity 71. 403...
・Ga5eli! 404, 405... Platinum translucent wind 501... Conductive substrate, 502... Quartz tube, 50
3... Carbon susceptor, 504... Induction heating coil t'v, 505... Bubbler, 506.508
...Flowmeter, 507...Name of gas cylinder agent Patent attorney Akira Koka 2 people tof-
---Open loquat 1 and box board tOE! , m5 --- 91 thick electric conductivity 103 ---
Layered Ihi spring proboscis eyebrow 1st rlA to4-k group t J2nd figure 30 I-11 Liao Q arrangement J elephant character base translation 80ξ昶5-11 Encounter port to wait for sex ao3--11 technique conversion Spring layer:? o4-Inumaki Party 1 Stone 3 Diagram: j06--Shaku Wealth layer 40+L--Anti-elbow counterfeit 402--One liter $ Denbyou 403--Go, Se layer 404.405--Brachito flat arrest ! 5ol --- 11-party d11 plate 5 (: 12-m = quartz tube 503 --- carbon buccinator 504 --- 3 kidney atsumi mouth coin 505 --- bubbler 5o6.so8--first class 1 go

Claims (6)

[Claims] (1) A spatial light modulation element characterized by having a structure in which a photoconductive layer and a layered compound in which the c-axis direction is connected by a van der Waals force are laminated. (2) The layered compound is GaSe, GaS, PbI_2,
HgI_2, InSe, InS, GaTe, HgTe,
The spatial light modulation element according to claim 1, comprising at least one selected from BiI_2 and CdI_2. (3) The spatial light modulator according to claim 1, wherein the photoconductive layer is an amorphous semiconductor made of at least one element selected from C, Si, and Ge and contains hydrogen. (4) The spatial light modulator according to claim 1, further comprising a reflective layer between the photoconductive layer and the layered compound. (5) GaSe, GaS, InSe, I
A method for producing a thin film, comprising producing a thin film made of at least one selected from nS, GaTe, and HgTe by a vapor phase growth method. (6) The method for manufacturing a thin film according to claim 5, characterized in that a CaF_2 film is laminated on a conductive substrate.