RU2282270C1 - Device for reading from mis photo-receivers - Google Patents

Abstract

FIELD: integration micro-electronics, possible use in systems for processing optical information.

SUBSTANCE: device for reading from MIS photo-receivers contains semiconductor substrate, layer of dielectric, MIS gate, MIS transistor, amplifier, source of direct voltage, two impulse generators, while source of MIS transistor is connected to MIS gate, drain - to direct voltage source, gate - to impulse generator, substrate is connected to another impulse generator, while input of amplifier is connected to MIS gate. Device is additionally provided with resistor, one end of which is connected to MIS gate, and another end - to source of direct voltage.

EFFECT: possible selection of high frequency components of signals on background of low frequency non-informational components, expansion of dynamic range for informational components of signals.

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Description

The invention relates to integrated microelectronics and can be used in optical information processing systems.

A device for reading from MIS photodetectors (Charge-coupled devices. Edited by M. Howes. M: Energoizdat, 1981, p. 231, Fig. 4.5b), containing a semiconductor substrate, MIS gate, "floating" MIS - a gate located under the MIS gate, and an electric amplifier isolated from the MIS gate, with a floating MIS gate connected to its input.

The known device operates as follows. A pulsed polarity voltage is applied to the MIS gates, leading to the appearance of a nonequilibrium depletion mode. With the end of the voltage pulses applied to the MIS gate, under the action of the optical signal that hits the photodetector, in the inversion layer of nonequilibrium depletion, the integration of minority charge carriers occurs. An integrable charge proportional to the incoming optical signal changes the capacitance of the space charge region of the semiconductor substrate. A change in the capacitance of the nonequilibrium depletion of the semiconductor substrate leads to a change in the potential of the "floating" MIS gate and to the appearance of a signal at the input of the amplifier that is proportional to the accumulated charge of minority carriers and to the parameters of the capacitive divider, which is the capacitance of the region of nonequilibrium depletion of the semiconductor substrate in combination with the capacitance of the region between floating "MIS gate and semiconductor substrate, with the capacitance of the region between the" floating "MIS gate and MIS gate and with a capacitance Itel.

The closest technical solution to the claimed one is a reader with MIS photodetectors (charge-coupled devices. Edited by M. Howes. M .: Energoizdat, 1981, p. 231, Fig. 4.5a), containing a semiconductor substrate, a dielectric layer, MIS gate made on a dielectric layer, MIS transistor, amplifier, two pulse generators, a constant voltage source, while the source of the MIS transistor is connected to the MIS gate, the drain is connected to the first pulse generator, the gate is connected to a constant voltage source, amplifier input conn nen a MIS gate and the substrate coupled to the second pulse generator.

This known device operates as follows. A DC bias voltage is applied to the drain of the MOS transistor. A voltage in a pulse mode of a given polarity is applied to the semiconductor substrate and the gate of the MOS transistor. When a voltage pulse is applied, the MIS gate is brought into a state of nonequilibrium depletion. With the end of the voltage pulses applied to the gate of the MIS transistor and the semiconductor substrate, the integration of minority charge carriers occurs in the inversion layer of the nonequilibrium depletion under the influence of an optical signal that hits the photodetector. An integrable charge proportional to the incoming optical signal changes the capacitance of the space charge region of the semiconductor substrate. A change in the capacitance of the nonequilibrium depletion of the semiconductor substrate leads to a change in the potential of the MIS gate and to the appearance of a signal at the input of the amplifier proportional to the accumulated charge of minority carriers and the capacitive divider parameters, which is the capacitance of the region of nonequilibrium depletion of the semiconductor substrate in combination with the capacitance of the MIS gate and the capacitance amplifier.

The disadvantages of the above analogs include the lack of the function of highlighting high-frequency signal components against the background of low-frequency non-information components, the narrowness of the dynamic range for information signal components and, as a consequence, the limitation of the sensitivity of photodetector devices based on such reading devices, the need for preliminary signal processing devices placed before the amplification stage . The disadvantage is that for photodetectors in the infrared region of the spectrum (IR FPU), information components are variable signal components (high-frequency components), and constant or slowly varying signal components (low-frequency components) due to the presence of background radiation and dark leakage currents of photodetectors are not carrying useful information, but they make up 90% or more of the total signal level. The need to transmit the entire signal, together with components that do not carry useful information, imposes strict requirements on the dynamic range of the amplifier, limits the dynamic range for the information components of the signals, thereby limiting the sensitivity of photodetectors.

The technical result of the invention is:

- achieving the allocation of high-frequency components of the signals against the background of low-frequency non-information components;

- expansion of the dynamic range for information components of signals.

The technical result is achieved by the fact that the reader from the MIS photodetectors containing a semiconductor substrate, a dielectric layer, an MIS gate, an MIS transistor, an amplifier, a constant voltage source, two pulse generators, the source of the MOS transistor connected to the MIS gate, the drain - with a constant voltage source, the shutter - with a pulse generator, the substrate is connected to another pulse generator, and the input of the amplifier is connected to the MOS gate, additionally equipped with a resistance, one end of which is connected to the MIS gate, and the other end is a constant voltage source.

The invention is illustrated by the description and drawing, which shows a diagram of the proposed device for reading from MIS photodetectors, where 1 is the substrate, 2 is the dielectric layer, 3 is the MOS gate, 4 is the MIS transistor, 5 is the amplifier, 6 is the resistance, 7 - pulse generator, 8 - constant voltage source, 9 - pulse generator.

An additional implementation of the resistance in the reader from the MIS photodetectors between the constant voltage source and the MIS gate leads to the appearance of a function for isolating high-frequency signal components against the background of low-frequency non-information components. Suppression of constant or slowly changing signal components occurs as a result of the filter consisting of the MIS photodetector itself (since the MIS gate has a capacitance) and resistance.

For hybrid IR FPUs in which the reader and the MIS photodetector are performed on different substrates, the proposed solution, namely the use of the MIS photodetector itself as an integral part of the filter, provides significant advantages over traditional solutions. The creation of modern multi-element IR FPUs is characterized by an increasing tendency to downsize. In this regard, the placement in each cell of the reader along with the capacitance amplifier of a sufficiently large nominal value for separating the information components of the signal is possible only due to the deterioration of the parameters of the amplifier. Otherwise, if you do not go along the path of degradation of the amplifier parameters, then introducing a capacitance of a sufficiently large nominal value to isolate the information components of the signal leads to an increase in the cell size of the reader.

Creating a high-pass filter based on an MIS photodetector and an additional resistance connected to it placed before the amplifier reduces the requirements for the dynamic range of the amplifier, which leads to an expansion of the dynamic range for information components of signals and an increase in the sensitivity of the photodetector based on the proposed reader.

A reader with MIS photodetectors contains structural elements: a substrate (1), a dielectric layer (2), an MIS gate (3), an MOS transistor (4), an amplifier (5), a resistance (6), a pulse generator (7) , DC voltage source (8), pulse generator (9) (see drawing).

In the proposed technical solution, the structural elements of the reader and the MIS photodetector are made on different substrates. The MIS photodetector contains a substrate (1), a dielectric layer (2) placed on the substrate (1), an MIS gate (3), which is made on the dielectric layer (2). The reader contains structural elements that directly make it, an MOS transistor (4), an amplifier (5), a resistance (6), a pulse generator (7), a constant voltage source (8), a pulse generator (9), and also contains a MIS photodetector as a structural element.

The source of the MOS transistor (4) is connected to the MOS gate (3) of the photodetector, the drain of the MIS transistor (4) is connected to a constant voltage source, and the gate of the MIS transistor (4) is connected to a pulse generator (7). The substrate (1) of the photodetector is connected to a pulse generator (9). The input of the amplifier (5) is connected to the MIS gate (3) of the photodetector. The resistance (6) is connected at one end to the MIS gate (3) of the photodetector, and at the other end to a constant voltage source (8).

The pulse generators (7), (9) are designed to supply voltage in a pulse mode with a given polarity of a rectangular shape.

The device operates as follows. A DC bias voltage is applied to the drain of the MOS transistor (4). A voltage is applied to the substrate (1) and the gate of the MOS transistor (4) in a pulse mode of a given polarity, while the MIS gate (3) switches to the mode of nonequilibrium depletion. The voltage is supplied with the same polarity, with equal periods, however, the duration of the voltage pulse applied to the substrate (1) is less than the duration of the voltage pulse applied to the gate of the MIS transistor (4), and their time shift is such that the pulse lasts, fed to the gate of the MOS transistor (4), the pulse applied to the substrate (1) begins and ends. With the end of the voltage pulses applied to the gate of the MIS transistor (4) and the semiconductor substrate (1), under the influence of an optical signal that hits the photodetector, minority charge carriers are integrated in the inversion layer of nonequilibrium depletion. An integrable charge proportional to the incoming optical signal leads to a change in the capacitance of the space charge region of the semiconductor substrate (1). The charge accumulation time is equal to the time between the end of the current pulse and the beginning of the next voltage pulse applied to the gate of the MOS transistor (4). The capacity of the space charge region in combination with the resistance (6) filters high frequencies with a cutoff frequency equal to the inverse product of the capacitance and resistance. A change in the capacitance of the region of nonequilibrium depletion of the substrate (1) upon integration of minority charge carriers in the inversion region of the substrate under the MIS gate (3) leads to a change in the potential of the MIS gate (3). At the input of amplifier (5), a signal appears proportional to the amount of accumulated charge of minority carriers, to the parameter of the capacitive divider, which consists of the capacitance of the region of nonequilibrium depletion of the substrate (1), the capacitance of the MIS gate (3), the capacitance of the amplifier (5), and proportional to the transfer frequency response of the filter based on an MIS photodetector and additional resistance.

A positive effect of the invention is to increase the sensitivity of IR FPU created on its basis.

Claims (1)

A device for reading from MIS photodetectors containing a semiconductor substrate, a dielectric layer, an MIS gate, an MIS transistor, an amplifier, a constant voltage source, two pulse generators, the source of the MIS transistor connected to the MIS gate, and the drain to a constant voltage source, the gate is with one pulse generator, the substrate is connected to another pulse generator, and the input of the amplifier is with an MIS gate, characterized in that it is additionally equipped with a resistance, one end of which is connected to the MIS gate, and the other end with a constant voltage source.