JP2661689B2 - Light sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical sensor utilizing a photoelectric effect of a photoconductor. [Prior Art] FIG. 5 shows an example of a conventional optical sensor, in which reference numeral 1 denotes a substrate. The substrate 1 is made of glass, quartz, ceramics, metal coated with an insulating film, silicon coated with an oxide film, or the like, and a photoconductor 2 is provided on the substrate 1. The photoconductor 2 is a thin film made of a material exhibiting a photoelectric effect such as hydrogenated amorphous silicon (hereinafter abbreviated as a-Si: H) and cadmium sulfide. On the photoconductor 2, a-S doped with a phosphorus atom or the like is provided.
N ⁺ (gap) layers 3 and 4 made of i: H are provided via a gap 5 having a predetermined gap. Then, the electrode 6 is formed on such n ⁺ layer 3, the n ⁺ layer 4 electrode 7 on, respectively aluminum, a method and metal mask for patterning by etching by photolithography and depositing a metal such as chromium It is provided by a thin-film forming means such as a method of pattern-depositing the metal through the above. In such an optical sensor, as shown in FIG. 5, for example, when light is applied to the photoconductor 2 in the gap 5 in a state where a constant voltage is applied to the electrode 7 side, the positive light generated by this light is irradiated. Holes and electrons move to the electrodes 6 and 7, respectively, and a photocurrent flows between the electrodes 6 and 7 according to the intensity of irradiation light. [Problems to be Solved by the Invention] However, such an optical sensor has the following problems. That is, as shown in FIG.
Since the n ⁺ layer 3 is interposed between, the n ⁺ layer 3 is prevented to move in the electrodes 6 of the hole H becomes a barrier, the photoconductor in the vicinity of the interface between the n ⁺ layer 3 Holes H accumulate in 2. For this reason, the light response time of the optical sensor is determined by the lifetime of the accumulated holes H, and there is a problem that the light response speed cannot be increased. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a high-sensitivity optical sensor that can increase the light response speed, is easy to manufacture, has a large light-intake portion, and has a high light-receiving portion. [Means for Solving the Problems] In the present invention, a pair of electrodes are provided on a photoconductor so as to face each other via a gap layer, and one of the electrodes is brought into surface contact with the photoconductor. The solution was taken. In the optical sensor according to the present invention, one of the electrodes and the photoconductor are brought into surface contact, so that holes generated in the photoconductor by light irradiation do not accumulate in the vicinity of the interface with the gap layer. It can be quickly moved into the electrode in contact with the conductor. Therefore, in this optical sensor, the light response time does not depend on the lifetime of the hole but depends on the carrier traveling speed of the hole. Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. The same reference numerals are given to the common portions between the configuration of the optical sensor of the present invention and the configuration of the conventional optical sensor, and the description of those portions will be omitted. The optical sensor of this example is characterized in that a conductive portion 8 is provided on the gap 5 side of the electrode 6 as a conductive path between the electrode 6 and the photoconductor 2. The conducting portion 8 is provided integrally with the electrode 6, and the lower surface thereof is a contact surface 8 a that makes surface contact with the upper surface of the photoconductor 2. The size of the contact surface 8a is determined by the size of the hole H from the photoconductor 2.
Is determined in consideration of the ease of movement and the size of the substrate 1. The optical sensor having such a configuration is, as shown in FIG.
Since the holes H generated by the photoconductor 2 can quickly move into the electrode 6 via the conduction portion 8, the light response speed is determined according to the carrier traveling speed of the holes H, and the light response speed is increased. It will be possible. FIG. 3 shows a second embodiment of the present invention. In the optical sensor of this example, the contact surface 8 serving as a moving passage of the hole H from the photoconductor 2 is provided on both the electrode 6 side and the electrode 7 side.
Conducting portions 8, 8 having a, 8a are formed. In the optical sensor having such a configuration, the electrodes 6, 7
Since the conductive portions 8 and 8 are formed respectively, the holes H are moved to the electrodes 7 through the conductive portions 8 on the electrode 7 while applying a voltage to the electrode 6, contrary to the first embodiment. It can also be used in such a way that it can be used in both directions. FIG. 4 shows a third embodiment of the present invention. In the optical sensor of this example, the photoconductor 2
And the n ⁺ layers 3 and 4 and the plate-like electrodes 6 and 7 are provided so that their relative positions are reversed, and a part of the electrode 6 is a planar conductive portion 8. In the optical sensor having such a configuration, since a part of the plate-shaped electrode 6 is used as it is as the conducting portion 8, the effect of facilitating the production is achieved. Further, in the optical sensor of this example, since both electrodes 6 and 7 are configured to be covered with the photoconductor 2, the light taking-in portion can be made larger than in the above two embodiments, and the sensor becomes more sensitive. In the above three embodiments, glass, quartz, ceramics, etc. were used as the material for forming the substrate 1,
In particular, when a material having transparency is used for the substrate, light irradiation from the substrate side (the back side of the optical sensor) becomes possible. further,
In the above three embodiments, the contact surface 8a may be brought into contact with the photoconductor through a P-type semiconductor made of a-Si: H doped with boron or the like. In this case, the movement of holes from the photoconductor to the electrode is performed more effectively. Examples will be described below. Example A photoconductor made of a-Si: H having a thickness of about 1 μm was formed on a glass substrate by a plasma CVD method using glow discharge. Next, two n ⁺ layers were formed on the photoconductor at a distance of about 15 μm by plasma CVD and photolithography for about 1 μm.
It was formed with a thickness of 00 °. Then, this n ⁺ on one n ⁺ layer
A film about 3,000 mm thick made of chromium slightly larger than the layer and extended to the other n ⁺ layer side was formed by sputter deposition and photolithography, and this was used as one electrode. The extended portion of this electrode is used as a conductive portion, and the width of the portion is approximately 5 μm.
m. At the same time, on the other n ⁺ layer, a film made of chromium having the same shape as this n ⁺ layer and having a thickness of about 3000 ° was formed and used as the other electrode. Thus, an optical sensor having a distance between the two electrodes of about 10 μm was manufactured. Next, while applying a constant voltage to an electrode of the optical sensor where no conducting portion is formed, the photoconductor between the two electrodes was irradiated with pulsed light to examine the optical response. 10 to 100 μsec. For comparison, a prototype of the conventional optical sensor shown in FIG. 5 was manufactured and its optical response was examined. As a result, the response time of this optical sensor was about 1 msec. [Effects of the Invention] As described above, the optical sensor of the present invention is provided with a pair of electrodes facing each other via a gap layer on a photoconductor,
Since one of the electrodes and the photoconductor are brought into surface contact, the movement of holes generated in the photoconductor by light irradiation is rapidly performed from the photoconductor to the electrode. Therefore, since the optical response time of the optical sensor depends on the carrier traveling speed of the holes, the optical response speed is remarkably improved as compared with the conventional optical sensor which depends on the lifetime of the holes. It will be of type. If both electrodes are brought into surface contact with the photoconductor through the conductive portion, holes are applied to the electrodes through the conductive portion on the electrode side while applying a voltage to one of the two electrodes. It can be used by moving it to the side, so it is possible to move holes to one electrode side or to move the holes to the other electrode side, and it can be used bidirectionally with both electrodes Become like Further, a pair of electrodes and a gap layer are provided on the substrate, a photoconductor is provided so as to cover them, and at least a part of the electrode on the lower potential side is formed as a conductive portion in surface contact with the photoconductive layer, By using a part of the electrode as it is as a conducting part, it has the effect of facilitating manufacture, and since both electrodes are covered with the photoconductor, it is possible to make the light intake part larger than the previous configuration. And a more sensitive optical sensor can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing a first embodiment of the present invention;
FIG. 2 is an energy band diagram of the optical sensor of FIG. 1, FIG. 3 is a schematic sectional view showing a second embodiment of the present invention, and FIG. 4 is a third embodiment of the present invention. It is an outline sectional view. FIG. 5 is a schematic sectional view showing an example of a conventional optical sensor, and FIG.
The figure is an energy band diagram in the optical sensor of FIG. 2 ... photoconductor, 3, 4 ... n ⁺ layer (gap layer), 6,
7 ... Electrode, 8 ... Conduction part, 8a ... Contact surface of conduction part.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yasuhiko Kasama               1-7 Yukiya Otsukacho, Ota-ku, Tokyo Al               Within Pus Electric Co., Ltd.                (56) References JP-A-60-128484 (JP, A)                 JP-A-59-167075 (JP, A)                 JP-A-59-138373 (JP, A)                 Shokai Sho 59-127250 (JP, U)

Claims (1)

(57) [Claims] On the photoconductor, a pair of gap layers are provided adjacent to each other with a gap for light transmission therebetween, electrodes facing each other via the gap are provided on the pair of gap layers, and a potential difference is applied to both electrodes. And a conductive portion that is in surface contact with the photoconductor at least on the electrode side having a lower potential among the electrodes. 2. 2. The optical sensor according to claim 1, wherein each electrode is provided with a conductive portion that makes surface contact with the photoconductor. 3. On the substrate, a pair of electrodes that are opposed to each other with a gap for light transmission are provided, a gap layer is provided on the pair of electrodes with the gap therebetween, and the gap and the vicinity of the gap are provided on the electrodes. A photoconductor covering the electrode and the gap layer,
An electric potential difference is applied between the two electrodes, and a gap between the pair of electrodes is made narrower than a gap between the pair of gap layers, so that at least a part of the lower-potential electrode is in surface contact with the photoconductive layer. An optical sensor characterized in that it is a part.