RU1823931C - Phototransistor - Google Patents

Abstract

Usage: semiconductor microphotoelectronics, registration of visible optical radiation. SUMMARY OF THE INVENTION: The phototransistor is made in a thin semiconductor layer on an insulated substrate and contains drain and source areas with contacts to them, the p-region of the channel, above which there is a control electrode insulated by a dielectric layer connected to a reference voltage source. The channel area is isolated from other circuits except the source and drain. The reference voltage of the source satisfies the condition U0n - Unop (0.05-0.5) Unop, where Unop is the threshold voltage of the transistor field electrode. 1 ill.

Description

The invention relates to the field of optoelectronics, in particular to optical information processing devices, and can be used to construct devices for recording and processing optical signals.

An object of the present invention is to remedy these drawbacks and provide an increase in photosensitivity. The goal is achieved in that in the phototransistor, which includes a p-region of the source and drain with contacts made in a thin semiconductor layer on an insulated substrate, the p-region of the channel, over which there is a field electrode insulated by a dielectric layer connected to the voltage source, the channel region is insulated from areas other than areas of the stack and source, and the reference voltage of the source is Don. satisfies the condition:

Don - Unop - (0.05-0.5) UnoP. where Unop is the threshold voltage of the field electrode of the transistor.

The set of distinguishing features, namely, that the channel region is isolated from other areas except the drain and source regions, and the reference voltage of the source is Uon. satisfies the condition: Uon. - Unop (0.05-0.5) Unop improves the photosensitivity of the phototransistor.

When checking the patent documentation, no analogues were found with the indicated set of distinctive features, which allows us to conclude that there are significant differences between the claimed device and the previously known ones.

The drawing shows the structure of the proposed device. The phototransistor contains an insulating substrate 1 on which a region of p-type silicon 2 is formed with two regions 3 and 4, 2 electrodes 5 and 6 are connected to the p-region, respectively. The control electrode 7 is located above the p-region 2 and is isolated from it by a dielectric layer. The device operates as follows.

with

with

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R

about

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fe

A reference voltage equal to Uon Unop + AU is applied to the control electrode 7 located on the dielectric layer 8, where Unop is the threshold voltage of the MOS transistor formed by the regions n +, p, n +, 3.2 and 4, respectively, and the electrode 7, and Л U is the voltage equal to approximately (0.05-0.5) Unop. In this case, the transistor is ajar and an insignificant dark current flows through it, on the order of several tens of μA

i

proportional to (U0n-Unop)

(1).

Under the influence of quanta of the light flux supplied, for example, through a transparent substrate 1 to the p-region 2, electron-hole pairs are generated primarily, while the holes accumulate in the region p 2 and change the threshold voltage with their charge transistor downward.

The change in the threshold voltage is proportional to the accumulated charge, which, in turn, is proportional to the intensity of the light flux. Moreover, due to the isolation of the p-region 2 from all other electrodes and external circuits, its capacitance is very small and even a small charge caused by a weak light flux leads to a significant change in the threshold voltage. This, in turn, leads to a sharp increase in the current through the transistor in accordance with (1), i.e. the photosensitivity of such a structure is very high.

A specific device in accordance with the proposed device was made on a sapphire substrate with a thickness of 400-500 microns. The semiconductor regions GL r, n + are made in a silicon layer 0.6 μm thick. The control electrode is made of polycrystalline silicon with a thickness of

400-600 A.

10 At a ramped current through the structure of 1-2 μA, the light current reached 5-8 μA or more at a light power of the order of tens of nanowatts, which exceeds the light current of the same photodiode on bulk silicon and exceeds by several thousand times times photodetector of a diode made in the same thin layer of silicon on a sapphire substrate.

Claims (1)

The claims 20 Phototransistor, including a p + region of the source and drain with contacts made in a thin semiconductor layer on an insulated substrate, the p-region of the channel above which the insulated layer is located 25 dielectric field electrode connected to a reference voltage source, characterized in that, in order to increase photosensitivity, the channel area is isolated from other areas, 30 except the drain and source regions, and the reference voltage of the source Uon satisfies the condition Uon - Unop (0.05-0.5) UnoP, where Unop is the threshold voltage of the field 35 transistor electrodes.