JPS6194358A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To use a sensitivity layer having low resistivity, and to improve resolution characteristics in the lateral direction by forming a potential barrier by shaping a common electrode or region between a sampling electrode or region. CONSTITUTION:A plurality of sampling electrodes 7 and common electrodes 14 are formed selectively onto a substrate 6 consisting of a semiconductor, etc. An I layer 9 composed of amorphous Si is deposited. In a sensor having said structure, negative voltage is applied to the electrodes 14 and positive voltage to the electrodes 7. Optical signal charges 13 generated by beams in the upper surfaces of the sampling electrodes A flow through the electrodes A by a drift electric field EL in the sensor. The charges 13 intend to spread in the lateral direction by a diffusion phenomenon at that time, but the diffusion phenomenon is prevented by the electric field EL. Consequently, the charges shift to the adjacent sampling electrode B, thus reducing stored signal charges, then improving the deterioration of lateral resolution. Resistance need not be increased by the addition of an impurity, etc. in the photoelectric conversion layer 9, thus also enhancing optical response characteristics.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a photoelectric conversion device having a photoelectric conversion layer.

Structures of conventional examples and their problems Recently, in 1976, W.E.S. Basic and applied research on amorphous silicon has become active. It is no secret that research into solar cells with a p-1-n diode structure is active as part of applied research, but rather than using the current generated by this light as energy, applied research into photoelectric conversion sensor devices is important. has also started.

General near-morphous silicon is often created by glow discharge decomposition of silane (SiH4) gas.

FIG. 1 shows an example of the structure of a solar cell produced by this method, and the photoelectric conversion sensor film also has essentially a similar structure.

In Figure 1, 1 is a glass or metal substrate, 2 is an n-type amorphous silicon layer (n layer) doped with phosphine gas (PHs), etc., and 3 is an intrinsic amorphous silicon layer (1 layer) with no impurity added. It is. Of course, a trace amount of impurity gas may be added to each layer 3. 4 is a p-type amorphous silicon layer doped with impurity gas such as diborane (BH6,); 1 is a parallel silicon layer (p layer); 5 is a metal electrode (A7);
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(Au, etc.) or a transparent electrode (ITO, etc.).

Light enters from the substrate 1 or electrode 5 side as indicated by the arrow. Upon incidence of light, carrier pairs of electrons and holes are generated,
Electrons are diffused toward the substrate 1 side, holes are diffused toward the electrode 5, and the resulting current is extracted to the outside.

The greater the number of carriers that reach both sides due to this diffusion, the greater the amount of current that can be extracted to the outside. That is, the smaller the resistivity of this single layer 3 and the longer the diffusion length, the better. In normal decomposition of silane gas, the resistivity is about 1080 cm. On the other hand, when used as a sensor film, unless the resistivity of the sensitive layer 1 layer 3 is as large as about 1011 to 1012 Ωcm, the signal will be diffused in the lateral direction, resulting in poor signal separation characteristics and resolution characteristics. do.

Figure 2 shows an example of a sensor with a structure similar to a solar cell, and Figure 4 shows a signal sampling electrode or area electrically scanned by a scanning circuit (not shown) on a substrate 6 such as a semiconductor. 7 is placed thereon, and an n-type amorphous 7 silicon layer (n layer) 8. is placed thereon as a photoelectric conversion layer. An intrinsic amorphous i (i layer) 9, a p-type amorphous silicon layer (p layer) 10, and a transparent electrode layer 11 on the light incident side are laminated. In FIG. 2(b), the incident direction of light is reversed, and on a transparent glass substrate 12 on which a transparent electrode 11 is formed, nine layers 1o, an i layer 9. An n-layer 8 and a sampling electrode or region 7 are laminated, as shown in FIGS.
) are examples of different manufacturing orders.

Sensors generally apply a drift electric field from the outside and use light to effectively pull out all the optical signal carriers (electrons and holes) generated inside the photoelectric conversion film to an external circuit, which is different from solar cells. . The n-layers 8 and 9-layers 1o in Figure 2 are simply blocking layers, and when an external voltage is applied, they block the injection of holes from the positive electrode and electrons from the negative electrode side, and block the application of external voltage. One layer 9 serves as a sensitive layer that suppresses an increase in dark current due to voltage and improves the S/N ratio of an optical signal, and generates a main optical signal.

Therefore, without using such a blocking layer at all, a structure having a Sirotchi barrier layer that blocks the injection of electrons or holes due to the difference in work function between the sensitive layer and the conductive electrodes on both sides may be used.

Next, FIG. 3 shows the operating state of the sensor, taking FIG. 2(a)' as an example. As mentioned above, in order to use it as a sensor, a negative voltage is applied to the transparent electrode 11 and a positive voltage is applied to the sampling electrode or region 7 to form a drift electric field E (positive direction with respect to electrons) inside the sensor. do. FIG. 3 is a simulated representation of the movement of optical signal charges 13 (electrons) in the cross section of the element when light is incident on the sampling electrode layer from the transparent electrode 11 side.
is the sampling electrode A due to the drift electric field E in the sensor.
However, due to the diffusion phenomenon and the lateral electric field E, some optical signal charge 1 also moves toward the sampling electrode B.
3 will move. This degrades resolution. For this reason, research has been conducted on adding a small amount of impurity (N, B, H, etc.) to the sensitive layer to create a high resistance layer. requires a higher drift electric field and is difficult to drive at low voltage.

There is a problem that when a high drift electric field is applied, dark current increases and S/N deteriorates. As described above, conventional devices have had problems in satisfying the three conditions of low voltage drive and high resolution.

OBJECTS OF THE INVENTION In view of the above-mentioned problems, the present invention provides a sensor having a structure that allows the use of a sensitive layer with low resistivity and has improved lateral resolution.

Structure of the Invention The present invention is a photoelectric conversion device comprising a photoelectric conversion layer, a plurality of signal sampling electrodes or regions selectively formed in the photoelectric conversion layer, and a common electrode or region,
By arranging a common electrode or region between multiple signal sampling electrodes or regions, the lateral diffusion of optical signals is completely suppressed, lateral resolution is improved, and the photoelectric conversion layer is driven at a low voltage. The dark current is small and the S/Nk is improved.

Description of examples Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 4 shows a sensor structure according to an embodiment of the present invention in which a common electrode or region is separately arranged between a plurality of signal sampling electrodes or regions for the purpose of improving lateral resolution; Parts that are the same as those in the figure are given the same numbers. In the manufacturing method shown in FIG. 4, a plurality of sampling electrodes 7 and a common electrode 14 are selectively formed using a metal such as β on a substrate 6 such as a semiconductor. Next, silane gas (5iHa
), etc., by depositing one layer 9 of amorphous silicon by plasma glow discharge decomposition method.

In operation of the sensor having the above structure, a negative voltage is applied to the common electrode 14 and a positive voltage is applied to the sampling electrode 7. The electric field EL is drawn in the positive direction with respect to the electrons.

Optical signal charge 13 generated by light on the upper surface of the sampling electrode section flows to the sampling electrode section due to the drift electric field EL within the sensor. At this time, the diffusion phenomenon tends to cause lateral bleeding, but the drift electric field E prevents the diffusion phenomenon, and as a result, the signal charge that moves to the adjacent sampling electrode B and is accumulated decreases and spreads in the lateral direction. Resolution deterioration is improved.

In the above embodiment, a plurality of sampling electrodes 7
There is an advantage that the process is simple and the common electrode 14 can be formed at the same time. However, this configuration has the disadvantage that dark current tends to increase because there is no blocking layer between the photoelectric conversion layer 9 and the electrode 7 (or 14). Or
Dark current can be reduced by adopting a structure that takes full advantage of the differences in Schottky barrier height due to differences in work function using metals such as metals. In addition, n-type polysilicon is used as the sampling electrode 7, p-type polysilicon is used as the common electrode 14, and each blocking layer 15.16'i is selectively used between each electrode and the photoelectric conversion layer as shown in FIG. It is also possible to reduce the dark current by adopting a structure having the following structure.

The blocking layers 15 and 16 can be formed by depositing one layer 9 as described above and then selectively ion-implanting or diffusing each impurity into this one layer, or by depositing the blocking layers 15 and 16.
It is also possible to perform selective etching to leave only the electrode portion after depositing the layer 6, and then form the layer 9.

According to such a configuration, since each electrode is formed separately, it is possible to lower the resistance of the blocking layer 15,16'i. Therefore, the lateral resolution can be improved and charge injection can be completely blocked, resulting in a low dark current. Furthermore, since it is not necessary to increase the resistance of the photoelectric conversion film 9 so as not to degrade the resolution, an increase in forward current can be obtained, so that a diode with an excellent rectification ratio can be obtained.

In the above embodiment, signal charges generated by light incidence flow to the sampling electrode section due to the drift electric field EL within the photoelectric conversion layer 9.

However, on the light incident side of the photoelectric conversion layer 9, the drift electric field EL
becomes weaker, and the traveling distance of the generated signal charge becomes shorter. This tendency becomes stronger as the photoelectric conversion layer 9 approaches the light incident side, and the closer it gets to the surface, the more charges are recombined, resulting in a decrease in sensitivity. For this reason, in particular, the sensitivity on the short wavelength side where signal charges are generated near the light incident side of the photoelectric conversion layer, that is, the blue light sensitivity decreases significantly. FIG. 6 shows a sensor structure according to an embodiment of the present invention, in which an auxiliary electrode or region is arranged on the other side of the photoelectric conversion layer for the purpose of improving the photosensitivity. Second.
The same parts as in Figure 3.4 are given the same numbers. 7 run gas (5iH4) etc. and diborane gas (B
Using an additive gas such as 2H6), a 1° p-layer made of amorphous silicon is deposited. Next, an auxiliary electrode 17 made of a transparent electrode such as ITO is laminated.

In operation of the sensor having the above structure, the common electrode 14,
A negative voltage is applied to the auxiliary electrode 17, and a positive voltage is applied to the sampling electrode T. By applying a full negative voltage to this auxiliary electrode 17, the optical signal charge generated by the light on the upper surface of the B sampling electrode 7 can be caused to drift toward the sampling electrode 7, so that the decrease in photosensitivity on the short wavelength side is completely reduced. It can be improved.

In the above explanation, electrons have been mainly treated as optical signal charges, but the present invention is not limited to this. For example, they may be holes, and in this case, the bias voltage and The conductivity of each blocking layer may be reversed. It goes without saying that it is also possible to adopt a structure in which the light is incident from the entire substrate side. Furthermore, the photoelectric conversion layer 9
Although the present invention has been mainly described with reference to amorphous silicon, the present invention is not limited thereto, and may be a semiconductor thin film such as an I[-Vl group compound or a -v group compound.

Effects of the Invention As described above, according to the present invention, separation of the lateral resolution of the photoelectric conversion layer 9 having a sensitive layer with a relatively low resistivity is achieved by creating a potential barrier by forming different electrodes between the sampling electrodes. It is a simple process and structure.
:9 can be realized, so the effect is great. Further, since it is not necessary to increase the resistance of the photoelectric conversion layer 9 by adding impurities or the like, it is possible to completely reduce traps in the photoelectric conversion layer 9, and improve photoresponse characteristics.

In addition, sensors with this low resistivity sensitivity layer can use materials with high charge mobility, such as amorphous, single crystal, or compounds, and have the same sensitivity as conventional high resistivity sensitivity layers. The sensor can be driven with a lower bias voltage than a sensor with a layer, making it possible to create a low-voltage drive sensor that meets the trend toward lower power consumption in recent years.

[Brief explanation of drawings]

Figure 1 is a cross-sectional structural diagram of a conventional solar cell, Figure 2 (a)
, (b) is a structural cross-sectional view of a conventional sensor with a structure similar to that of a solar cell, Fig. 3 is a conceptual diagram of the operating state of the sensor, Fig. 4,
5 and 6 are structural sectional views of a sensor having a structure including a common electrode between a plurality of sampling electrodes (((()) according to an embodiment of the present invention. 6...Semiconductor substrate, 7...Signal sample amorphous silicon layer (・i layer), 10°16°°°...p-type amorphous silicon i (p-type,
11...Transparent electrode layer, 14...Common electrode or region, 17...Auxiliary electrode or region. Name of agent: Patent attorney Toshio Nakao, 1st person, 2nd person
Figure 3 Figure 4 ◇ Figure 5- Figure 6 ◇

Claims (3)

[Claims] (1) a photoelectric conversion layer; a plurality of sampling electrodes or regions selectively arranged on one of the photoelectric conversion layers;
A photoelectric conversion device comprising a common electrode or region between the plurality of sampling electrodes or regions. (2) The photoelectric conversion device according to claim 1, wherein the photoelectric conversion layer is made of amorphous silicon. (3) The photoelectric conversion device according to claim 1, further comprising an auxiliary electrode or region on the other side of the photoelectric conversion layer.