JPS58182280A - Photo detector - Google Patents

Abstract

PURPOSE:To obtain a photo detector of small dependence of photo detecting sensitivity on wavelengths and a low cost, by providing a pyroelectric material at the gate part of an FET constituted of a thin film transistor. CONSTITUTION:The pyroelectric body 12 having spontaneous polarization such as a ferroelectric substance is formed on a low cost transparent substrate 11 constituted of pyrex glass, etc. via a light absorber 10 and an electrode layer 13, the exposed surface thereof are covered with an SiO2 film 14 for a gate. Next, an N type substrate region 18 is formed on the pyroelectric body 12 via the film 14, and, respectively on the both sides thereof, a P<+> type source region 17 and drain region 19 which extend to the surface of the substrate 11 are provided. Thereafter, metallic wirings 15 for external connection are adhered on the side surfaces of these regions 17 and 19 while being made to run along the surface of the substrate 11 resulting in the formation of an N-channel transistor. Then, light shielding films 16 are adhered on the back surface of the substrate 11 at an interval, then a light 102 is made incident from this clearance, thus the light absorber 110 is made to generate a thermal conversion through the substrate 11, and accordingly the gate of the film 14 side of the pyroelectric body 12 is made to generate charges which differ with or without the presence of incident light.

Description

[Detailed description of the invention] This article concerns a photodetector consisting of:

As is well known, various photodetectors such as hot diode phototransistors have been proposed and put into practical use, but most of these photodetectors are mainly made of semiconductor materials, and their detection capability is limited by their energy gap. It has a wavelength limit and may be inconvenient to use.

The present invention provides a photodetector with less wavelength dependence and a lower cost than conventional photodetectors. The present invention will be explained in detail below with reference to the drawings.

The photodetector according to the invention has a structure similar to that of a conventional MOS field effect transistor, as shown in FIG. An S electric body 12 made of a pyroelectric material having spontaneous polarization such as a ferroelectric material is attached to an inexpensive transparent substrate 11 such as Pyrex glass, and a semiconductor thickness III such as polysilicon or amorphous silicon is further applied.
will be established. Semiconductor 7111111 such as 7 recon 7.
1 9Vi normal no M.

111 to the source and drain of the S-type field effect transistor
It corresponds to the l/i substrate, and the conductivity type is p.
+. This is an example of an n-channel transistor. 16 is a light shielding film. 14 is a regular silicon oxide metal for Kate, and 15 is North.

This is a metal wiring that electrically connects the drain to the outside. [Constructed by providing an electrode 13 on at least one side of the electric body 12.

Next, this photodetector is electrically connected as shown in diagram #I2.

As can be seen from FIG. 2, it is similar to the floating gate structure of an ordinary MO8 field effect transistor, and the drain 21 is equivalent to the semiconductor thickness a19 in FIG.
Semiconductor Expo ml 7. Saps) L/-) 2
3. Semiconductor thin film 18. The gate 24 is a pyroelectric material 12. The gate electrode 25 on the silicon oxide film 14 corresponds to the electrode 13. Source 22. A bias 26 is applied between the drain 21 and a load 27 is connected, and then a load 27 is connected between the drains 21 and 21.
7 is amplified by a signal processing system 28 and detected.

Further, incident light 102 as indicated by hv in FIG. 1 passes through the transparent substrate 11 and is thermally converted by the light absorber 11G.

At this time, the temperature of the pyroelectric body 12 increases compared to the case where no light is incident. Since the spontaneous polarization of a pyroelectric material changes depending on the temperature, as in the case of Shusho, the spontaneous polarization of the pyroelectric material 12 changes by Aps due to the incidence of light. ? [If the pole 13 is short-circuited to the source 22 and kept at ground potential as shown in FIG. Therefore, the electric field changes most strongly near the interface between the substrate 18 and the silicon oxide film 14 via the silicon oxide film 14. Therefore, source 22. The conductivity between the drains 21 changes depending on the presence or absence of light incidence, and the current flowing through the load 27'fr changes. The operation as a photodetector will be explained as above.

The photodetector according to the present invention has the advantage that the wavelength sensitivity is flat over a wide range from infrared to visible light.

That is, the wavelength sensitivity of the light absorber 110 is determined by the absorption characteristics of the light absorber 110.
When using an absorber called Gold Black, it has flat absorption characteristics from the infrared region to the entire visible light spectrum. It is already well known that all black can also be made into a thin film.
It is used for various purposes. As described above, the photodetector according to the present invention is essentially a thermal detector, and is advantageous in that its sensitivity is less dependent on wavelength, unlike ordinary semiconductor photodetectors.

Furthermore, as a heat detector, it is well known that a photodetector with a response speed on the order of microseconds has the general characteristics of a pyroelectric detector. This case is no exception.As is well known, titanium 1 is used as the material for the pyroelectric material 12 of the photodetector used in the present invention.
m! i! Lead (pbTios).

There are many materials such as lithium tantalate (AOS) and RMI-glycine (referred to as TGS), which can be made into thin films by high-frequency sputtering, vapor deposition, etc., and can be made into high-quality raw materials. Semiconductor thin films 17, 18, and 19 are made of sidemorphous silicon, cadmium 7V, etc. by chemical vapor deposition, etc.
The technology level is such that it is possible to easily form a mold, etc. It goes without saying that silicon oxide 1I 114 and metal wiring 15 can also be formed without any difficulty by making full use of current silicon integrated circuit technology.

Although the structure of the photodetector according to the *illustration example of the present invention is an example of an MO8 field effect transistor, it is not limited to this example and can be applied to other field effect transistors.

As described above, the present invention is effective as a photodetector which combines a non-electric material, mainly an IIE field effect, and a rice transistor, and which has a high ρ value and has little dependence on hepato length sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a photodetector according to an embodiment of the present invention, and FIG.
The figure is an electrical wiring diagram of the photodetector shown in FIG. 1. 11... Transparent substrate 12... Pyroelectric body 13... Electrode 14... Silicon oxide film 16... Light shielding layer 17, 18.19-... Semiconductor NBN 110-... Light absorber

Claims (1)

[Claims] (A photodetector patented as having a totally blind field effect transistor structure in which a 11g conductive material is provided in the gate portion. (2) All features of being a 'Turtle field effect transistor TASNII transistor. A photodetector according to claim 128.