RU2706197C1 - Method of controlling operation of a metal-insulator-semiconductor membrane capacitor structure - Google Patents

Abstract

FIELD: control systems.

SUBSTANCE: invention can be used to create memory and low power consuming integrated circuits of nonvolatile memory. Essence of the invention consists in that the method of controlling the operation of the membrane-type capacitor structure metal-insulator-semiconductor, in which the dielectric and the semiconductor are connected in series with respect to each other, wherein the dielectric is made from a non-light-sensitive material, and the semiconductor substrate is made from a light-sensitive material containing a dopant in concentrations of 10¹⁵÷10¹⁷ cm^-3, providing commensurability of capacitance or conductivity of dielectric and region of space charge of semiconductor and absence of fixation of Fermi level on interface of dielectric and semiconductor, comprises adjustment of electric field intensity and current value in dielectric during its forming and switching due to change of resistance of semiconductor substrate due to capacitance variation and conductivity of space charge region in semiconductor using high intensity light illumination 10¹⁸÷10²¹ photons/cm²⋅from structures on side of metal electrode and dielectric in area of own photosensitivity of semiconductor lining.

EFFECT: reduction of molding and switching voltages, expansion of resistance limit in low-ohmic and high-resistance states, expansion of spectral operating mode due to semiconductor, reduction of error probability when reading memristor state.

4 cl, 8 dwg

Description

The present invention relates to the field of nanotechnology, relates to a method for controlling the operation of a memristive capacitor structure of a metal-dielectric-semiconductor using lighting, which can be used to create a new generation of non-volatile memory devices for use in the element base of non-traditional neural network and quantum computing systems.

The study of the effect of light on the effect of resistive switching (memristive effect) is one of the promising areas in connection with the possibility of creating elements of resistive memory, the switching of which will be controlled by the effect of light. Resistive Switching Random Access Memory (RRAM, ReRAM), another name - memristor (English: memristor = memory + resistor) - the basis of a new generation of non-volatile memory devices, which work by using two stable dielectric states: states with high resistance (SHS) and states with low resistance (SSS), resistive switching (RP) between which is carried out by applying external voltage [Waser R., Aono M. // Nature Mater. - 2007. - V. 6. - P. 833-840]. The importance of conducting memristor research is currently evidenced by the inclusion of this research in the International Plan for the Development of Semiconductor Technology (Mickel P.R., Lohn A.J., Marinella M.J. // Mod. Phys. Lett. B. - 2014 .-- V. 28 (No. 10). - P. 1430003-1 - 1430003-25].

As a memristor, the structure is mainly used in the form of metal - dielectric - metal (MDM) capacitors and less often in the form of MIS capacitors, usually on a conductive silicon substrate.

For the occurrence of SHS and SNA, as a rule, the molding process is used: applying a voltage to the capacitor that is greater than a certain minimum voltage (molding voltage) and leading to a significant change in the electrophysical properties of the capacitor.

Only a few works are known on an attempt to obtain a light-sensitive resistive memory element. These works describe the effect of light on current and resistance when switching to a high-resistance or low-resistance state or several states that differ in resistance.

A transistor structure is known in which a current is transferred between a metal source and a drain in a dielectric film [P. Maier, F. Hartmann, M. Rebello Sousa Dias at al. Light sensitive memristor with bi-directional and wavelength-dependent conductance control. Applied physics letters. 109, 023501 (2016)]. In the middle of the dielectric film, quantum dots (QDs) are embedded. This current is controlled by two metal gates applied to the surface of the dielectric film. Capture of carriers by quantum dots provides a change in current during lighting and photo memory. However, such a structure is three-electrode, that is, it differs from the classical capacitor structure of a memristor with two electrodes. In addition, the memory is controlled by a charge on the CT, which tends to drain over time.

Branimir Bajac,

Goran M.

Photoresistive switching of multiferroic thin film memristors. Microelectronic Engineering. 2017]. В этой работе приводятся вольтамперные характеристики (ВАХ) с гистерезисом по току в темноте и на свету одинакового монотонного вида, но с несколько большими значениями тока при освещении.Known MDM - a structure with a photosensitive dielectric of a very complex and not sufficiently developed chemical composition (Pt / BaTiO ₃ / NiFe ₂ O ₄ / BaTiO ₃ / Au), which already complicates its production and compatibility with monolithic integrated circuits on silicon [

Branimir Bajac,

Goran M.

Photoresistive switching of multiferroic thin film memristors. Microelectronic Engineering. 2017]. In this work, the current-voltage characteristics (CVC) are presented with a current hysteresis in the dark and in the light of the same monotonous form, but with slightly larger current values under illumination.

Numerous two-electrode capacitor-type cells are known from patent RU 2256957 C2, containing layers of organic and inorganic materials that store resistance after applying a threshold voltage and are densified. Such structures are memory cells and can be controlled by both voltage and lighting. But no quantitative characteristics for these cells are given, both in the dark and under lighting.

It is known to create a MoS ₂ nanospheric memristor with planar gold electrodes, which showed the switching of light resistance [Wei Wang, Gennady.N. Panin, Xiao Fu and other. MoS ₂ memristor with photoresistive switching. Scietificc Reports, August 2016]. The authors believe that the polarization of MoS ₂ nanospheres can control the new device, which causes the resistance to switch in an electric field in the dark or under low-light white light due to the occurrence of conductivity wires. Memristor switching provides multi-level memorization. The ratio of resistances in the on and off mode is ten times greater in the light than in the dark. The authors believe that the MoS ₂ memristor has great potential, since the multifunctional device is designed using cost-effective manufacturing methods. However, the technology used by the authors requires high-resistance substrates, for example, semiconductor wafers coated with a thick dielectric. In addition, the planar arrangement of the electrodes and the high resistance of the memristor layers can lead to a strong environmental effect and require careful protection from the influence of the latter.

From patent RU 2580905 C2, a photo-switchable and an electric switchable organic field-effect transistor is known, a method for its manufacture and its use as a memory device. An organic field-effect transistor with a layer of photochromic compounds at the insulator-semiconductor interface is proposed as a light-controlled memory device, which ensures the appearance of a charge and its control at this interface, which is similar to the operation of an MNOS transistor used in flash memory. This device is technically more complex than a classic memristor and is controlled by a charge, which tends to drain as the information is stored. As you know, memorial memory is not inherent in the last drawback.

Photocatalytic oxidation of graphene with ZnO nanoparticles is known to create a light sensitive memristor [Olesya O. Kapitanoval, Gennady N. Panin At. All. Formation of Self-Assembled Nanoscale Graphene / Graphene Oxide Photomemristive Heterojunctions using Photocatalytic Oxidation. - NANO-113106.R2, 2017] A memristor is created on the basis of oxidized silicon with planar electrodes from Au and changes its resistance when switching voltage in the dark from 4⋅10 ⁶ (reset) to 5⋅10 ⁵ (set) Ohm and in the light from 1.5⋅10 ⁷ (RESET) to 3⋅10 ⁶ (SET) Ohm. A very slight effect of the influence of light is visible. In addition, the structure of such a memristor is different from the traditional one, which makes it impossible to use electrodes for switching crosshairs, as is done in crossbars.

From US 20160370682 A1, various structures and materials for light sensitive synaptic nanodevices based on alternating layers of metals, dielectrics and semiconductors are known. Planar structures are proposed when a light-sensitive film (including a multilayer film) is located on an oxidized silicon substrate and capacitor structures with a photosensitive material between metal plates. No specific characteristics of the devices: molding, switching and memory in the dark and in the light are not given in the document.

From the publication WO 2016171700 A1 of 10.27.2016, optical memory devices are known which can be used in optical programming devices. For example, we cite the principle of operation of one of such devices proposed in the document. In a metal waveguide filled with a semiconductor with memristive dielectric baffles, the current through which is controlled by the voltage on the plates of the MDM capacitor and, thus, the electromagnetic radiation passing through the semiconductor can be controlled by the state of the memristor (SET and RESET) and the number of memristors transferred to these states. The publication does not present the practical results of the implementation of the proposed ideas.

From patent US 8542518 B2, dated September 24, 2013, a photoresistive memristive element with a similar mechanism of action is known, based on a two-layer nanocondenser with a Pt / TiO _x / TiO ₂ / Pt structure. The photosensitivity in this element is due to a change in the resistance of the dielectric TiO _x film under illumination. However, it is known that dielectrics are less sensitive to light than semiconductors and can be very inertial due to the presence of a high concentration of electron traps in them, very small effects of light exposure are given in the patent. Also, the proposed photosensitive cell is poorly integrated into the planar-epitaxial silicon integrated circuit technology and is very limited in the selection of dielectric layer material. In an MIS capacitor, in the presence of a potential barrier in the semiconductor, which is easy to obtain, separation of photoelectrons and photoholes occurs during illumination, which determines the high speed and photosensitivity of the semiconductor. Also in the pn junction there is a potential barrier with similar effects. The proposed cell is very versatile in terms of the choice of technologies and materials for its manufacture and is easily integrated into planar-epitaxial silicon technology for the manufacture of integrated circuits and similar technologies based on other semiconductor materials.

The closest in technical essence and the achieved technical result to the proposed invention is a method of resistive switching in MIS structures based on silicon, stimulated by light, disclosed in the article "Light-stimulated resistive switching in structures metal-insulator-semiconductor based on silicon" (Tikhov S. V., Gorshkov O.N., Koryazhkina M.N., Antonov I.N., Kasatkin A.P. // PZhTF. T. 10. 2016. S. 78-86), adopted for the closest analogue (prototype) .

In the prototype method, resistive switching is performed in MIS structures based on silicon, stimulated by light. One of the high-k dielectrics — zirconia stabilized with yttrium oxide ZrO ₂ (Y ₂ O ₃ ) —YSZ (Yttria-stabilized zirconia), is used as the dielectric in these structures. Lighting is carried out by unfocused light from a 50 W halogen lamp (corresponds to a flux density of quanta (FLC) of ~ 10 ¹⁵ photons / cm ² ⋅ s). Such lighting reduces the resistance of the space charge region (SCR) of the semiconductor and increases the voltage drop across the dielectric, which leads to the formation of conductive cords in the dielectric. However, such lighting only causes the dielectric to be molded and does not further affect switching characteristics.

The objective of the invention is to create a method for controlling the operation of a memristive capacitor MIS structure based on a controlled change in the resistance of the semiconductor wrap of the capacitor under the action of high-intensity light, and thereby, on a smooth change in the voltage drop across the dielectric film.

The technical result is the expansion of the resistance limit in low-resistance and high-resistance states, reducing the likelihood of errors when reading the state of the memristor. Lighting also reduces the series resistance of the memristor, which significantly increases the speed when reading a high resistance state. Light control of the memristive structure expands the range of technical applications of resistive memory.

This is achieved by the fact that the method of controlling the memristive capacitor structure of a metal - dielectric - semiconductor, in which the dielectric and the semiconductor are connected in series with respect to each other, the dielectric is made of non-photosensitive material, and the semiconductor substrate is made of a photosensitive material containing an alloying impurity at concentrations of 10 ¹⁵ ÷ 10 ¹⁷ cm ^-3 , ensuring the commensurability of the capacitance or conductivity of the dielectric and the space charge region of the semiconductor and with the absence of fixing the Fermi level at the interface between the dielectric and the semiconductor, by adjusting the electric field strength and the current in the dielectric during its molding and switching due to a change in the resistance of the semiconductor substrate due to changes in the capacitance and conductivity of the space charge region in the semiconductor using light high intensity 10 ¹⁸ ÷ 10 ²¹ photons / cm ² ⋅c of structures from the side of the metal electrode and dielectric in the region of intrinsic photosensitivity of the plate semiconductor.

In FIG. 1 shows a schematic section and chemical composition of memristive structures, where: a) MIS planar structure; b) MDM structure; c) MIS-mesa structure.

In FIG. Figure 2 shows an exemplary view of equilibrium energy diagrams, where: a) a planar structure on Si; b) MIS mesa structure on GaAs. The figure indicates: E _c and E _v are the energies corresponding to the bottom of the conduction band and the ceiling of the valence band of the semiconductor; E _sd and E _vd are the energies corresponding to the bottom of the conduction band and the ceiling of the valence band for the dielectric, F is the Fermi level (Fermi energy).

In FIG. Figure 3 shows the I – V characteristics of the Au / Zr / YSZ / Sb / SiO ₂ / n-Si structure obtained at a voltage scan rate of 0.18 V / s. The capacitor area S ≈ 2⋅10 ^-3 cm ² . The arrows indicate the direction of the voltage scan: curve 1 - in the dark; curve 2 - in the light. IP - the initial state of the structure before molding.

In FIG. Figure 4 shows the I – V characteristics of an MIS capacitor with a 40 nm thick YSZ film, measured at a voltage scan duration of 0.18 V / s. The capacitor area S ≈ 10 ^-3 cm ² . Curves 3, 4 - in the dark, curves 5, 6 - when illuminated with focused light from a 40 W halogen lamp. The arrows indicate the direction of change of the switching voltage from SHS to SNA. The dashed curves show the I – V characteristics reproduced after switching in the SNA.

In FIG. Figure 5 shows the I – V characteristics of an MIS capacitor with a 40 nm thick YSZ film, measured at a voltage scan duration of 0.18 V / s. The capacitor area S ≈ 10 ^-3 cm ² . Curves 7, 8 - in the dark, curves 9, 10 - when illuminated with focused light from a 40 V halogen lamp.

In FIG. Figure 6 shows the switching curves of the I – V characteristics of an MDM capacitor with a YSZ film with different limiting currents of 0.1; one; 10 mA to the low-resistance state - curves 11, 12, 13, respectively, and to the high-resistance state - curve 14. The voltage sign is indicated for the gold electrode. At V> 0, switching to SHS occurs only in the absence of current limitation. The switching current in this case is 100 mA.

In FIG. Figure 7 shows the I – V characteristics of an MIS Mesa structure with a pn junction on GaAs with an area of 4.9 × 10 ^-4 cm ² . Curve 15 - in the high-resistance initial state in the dark, 16 - after switching to the low-resistance state in the dark, 17 - in the low-resistance state when illuminated with red light with a power of 1.5 W laser (LSR-660).

In FIG. Figure 8 shows the kinetics of the effect of the laser pulse on the current in the MIS Mesa structure at -1 V in the conducting state (set) at different light intensities. Power (P), W: curve 18-1.5; curve 19 - 0.58.

The proposed method for controlling the operation of a memristive capacitor MIS structure is as follows.

The method is carried out using memristive capacitor MIS structures on silicon or gallium arsenide using mesa structures with a pn junction facing the p-region dielectric (i.e., the dielectric and the semiconductor are connected in series with respect to each other). The structures illuminate with high-intensity light 10 ¹⁸ ÷ 10 ²¹ photons / cm ² ⋅ s from the side of the metal electrode and dielectric in the region of intrinsic photosensitivity of the semiconductor wrap. Lighting causes molding to occur due to a drop in the resistance of the semiconductor wafer and an increase in the voltage drop across the dielectric and the current flowing through it necessary for molding (the appearance of conductive filaments or filaments otherwise) shunting the MIS capacitor. The IV characteristics of such structures after molding demonstrate the effects of resistive switching and memory, i.e. Resistive switching in the dark appears, which can be controlled by lighting.

A prerequisite for the implementation of the proposed method is the use of memristive capacitor MIS structures, in which:

- the dielectric and the semiconductor are connected in series with respect to each other;

- the dielectric is made of a material that is not photosensitive;

- the semiconductor wafer contains a light-sensitive region, with the help of illumination of which at a given switching voltage, the current through the dielectric can be varied, both in the conducting state and in the initial high-resistance state (molding);

- the content of fine impurities in the semiconductor and the density of surface states (PS), provides the commensurability of the capacitances or conductivities of the dielectric and the SCR of the semiconductor, and, secondly, with the formation of structures with a low density of PS at the insulator-semiconductor interface to eliminate the fixation (pinning) of the Fermi level on this border.

The operation of the memristive structure (memristor) is carried out by adjusting the electric field strength and the current in the dielectric when it is molded and switching due to a change in the resistance of the semiconductor substrate due to a change in the capacitance and conductivity of the space charge region in the semiconductor by changing the lighting through practically transparent to light a metal electrode and a dielectric with a wavelength of 660 nm, which excites an intrinsic photoresponse in the semiconductor and lowers the potential flax barrier at the interface with dielectric and a p-n junction. The intrinsic photosensitivity range extends from short wavelengths of 400 nm to 1130 nm for silicon and from 400 nm to 870 nm for gallium arsenide.

An increase in conductivity or an increase in capacitance causes a redistribution of the voltage applied to the memristor on the dielectric, removing the current limitation through it and thereby causing it to form or switch.

To achieve the most efficient switching, the resistance and capacitance of the dielectric and the surface region of the semiconductor should be comparable. Thus, using a semiconductor wafer create a series-dependent resistance or capacitance that limits the current through the dielectric. Current limitation reduces the number of switching filaments and thus reduces the current in the conductive state. When illuminated, the voltage drop across the dielectric increases, which causes the formation or increase of the switching voltage across the dielectric. An increase in the number of switching filaments in the latter case increases the current in the conducting state. The region of spectral sensitivity of this effect corresponds to that for a semiconductor, and its absolute value and speed is determined by the presence of a potential barrier in the semiconductor. This can be, for example, a layer depleted in the main charge carriers at the surface of the semiconductor, bordering the dielectric, or a p ⁺ -n junction, facing the p-region to the dielectric. The dielectrics used in memristors are usually not sensitive to light in the visible and infrared regions of the spectrum. Photosensitivity in the present invention is determined by the photosensitivity of the SCR semiconductor. To increase the efficiency of the influence of light on switching, it is necessary to reduce or completely eliminate the influence of capture of free carriers, which reduces the current in the semiconductor under illumination. The last problem can be solved by creating a non-symmetric p ⁺ -n junction, facing the dielectric heavily doped with p-region. This is due to the fact that the heavily doped semiconductor region is similar to metal and practically does not contain PS, and the metallurgical boundary of the p ⁺ and n regions in the pn junction also does not contain these states because of its high perfection, as it is formed by the method of homoepitaxy.

The spectral photosensitivity palette can be changed by selecting the appropriate semiconductor materials. In InSb, for example, the intrinsic response or photoconductivity may be limited on the short-wavelength side to 12.3 μm. The use of different semiconductor wafers makes it possible to use a very wide range of light wavelengths from 13 microns to 400 nm to influence resistive switching.

Thus, the present invention provides an extension of the resistance limit in low-resistance and high-resistance states, which in turn affects the reduction of the probability of error when working in the read mode of recorded information, the expansion of the spectral range of light exposure. Lighting also reduces the series resistance of the memristor, which significantly increases the speed when reading a high resistance state. Light control of resistive memory in a dielectric expands the range of technical applications of resistive memory.

The present invention makes it possible to create photosensitive matrices for neural circuits and the development of technology in the current field of manufacturing memristors, which are the basis of a new generation of non-volatile memory devices. The individual elements of such a matrix are MIS capacitors that are molded and switched under the influence of light and voltage.

The proposed method differs from those described as prototypes, both in the structure of the memristor cell which is used, including a mesa structure with a pn junction, and in the type of implementation of the influence of lighting, based on a controlled change in the resistance of the semiconductor lining of the capacitor under the action of high-intensity light , and thereby, on a smooth change in the voltage drop across the dielectric film. These structures use materials whose production technology (and drawings of integrated circuits) is well developed and compatible with the widely used planar epitaxial silicon technology.

Below are examples of specific implementation of the proposed method.

Example 1

Management of the depleted-layer memristor of the planar structure at the insulator-semiconductor interface Au / Zr / YSZ / Sb / SiO ₂ / n-Si.

For the structure whose schematic representation is shown in FIG. 1a, single-crystal n-Si wafers (KEF-4.5) with a crystallographic orientation of (100) coated with a tunnel thin layer of SiO ₂ are used as a semiconductor wafer. A ~ 2 nm thick Sb layer is deposited on this layer by the MOS hydride method from a source of trimethylantimony in a hydrogen atmosphere at a temperature of 450 ° C. SiO ₂ oxide is created by sequential treatment of the Si surface in hydrofluoric acid, and then in a mixture of sulfuric acid with hydrogen peroxide. A 40 nm thick YSZ layer (12 mol% Y ₂ O ₃ ) was deposited onto this substrate by RF magnetron sputtering at a temperature of 300 ° C using a 2g1-1g2-eb4-th1 Torr International installation. The structure thus obtained is annealed for a short time (2 min) in an argon atmosphere at a temperature of 450 ° C. The method used to produce oxide, the subsequent deposition of an antimony layer on it, and thermal annealing make it possible to create a Si surface with a relatively low density of surface states (PS) and with the presence of regions of electric field concentrators on it to form filaments. After annealing, the upper electrodes translucent for illumination of 20 nm thick (with a 3-nm thick Zr sublayer to improve adhesion) are deposited onto the surface of the dielectric layer by direct current magnetron sputtering. An ohmic contact to the silicon wafer is created by burning an electric discharge of Sn (10% Sb) metal foil. An exemplary view of the equilibrium energy diagram of the structure is shown in FIG. 2a. The presence of depletion of the near-surface layer in the semiconductor at the interface with the dielectric is determined by the sign of the strong-signal barrier photoEMF (it corresponds to the value of the potential barrier ≈ 0.3 V). [Application of the method of high-signal capacitor photo-emf to determine some parameters. S.V. Tikhov. // FTP. 1995.15.29. issue 4. p. 742-749].

Then, the I – V characteristics of the structure are measured on Si at a voltage of V <0 on Au (determined relative to the semiconductor wrap) in the dark and under illumination (Fig. 3). All I – V characteristics are measured on an Agilent B1500A semiconductor analyzer. Focused light is produced using a halogen incandescent lamp with an electric power of 40 watts. The light output from this lamp is ≈ 1.2 W. The maximum of light radiation is observed at a wavelength of 660 nm and corresponds to a flux of quanta ≈ 4.2⋅10 ¹⁸ photons / cm ² s in a focused spot of 1 cm ² . That is, the density of the flux of quanta incident on the structure is 4.2 × 10 ¹⁸ photons / cm ² s. The radiation intensity (value PPC) is reduced using neutral filters.

The effect of lighting on the process of molding a dielectric in an MIS structure is investigated. As is known in MIS structures, the applied voltage V is divided between a semiconductor and a dielectric due to their series connection [V.N. Ovsyuk. Electronic processes in semiconductors with space charge regions. (Novosibirsk, Science, Sib. Branch, 1984), p. 252.]. In FIG. Figure 3 shows that in the dark the current I is small (curve 1) and practically does not depend on voltage. Forming does not occur. This can be explained by the predominant voltage drop across the electron-depleted SCR on the surface of a semiconductor adjacent to a dielectric. This state can be almost stationary if there is a leak of holes from the semiconductor to the dielectric [F.H. Hielsher, N.M. Preier Solid-State Electronics, 12, 527-538, 1969].

Lighting with a halogen lamp causes molds to appear. When illuminated, the concentration of electrons and holes increases sharply, the SCR resistance decreases, and the capacitance increases, and the voltage is redistributed from the semiconductor to the dielectric. The density of the current flowing through the dielectric, in this case, is sufficient for the molding of the dielectric and the formation of filaments. The current through the dielectric increases and then retains the value corresponding to the low-resistance state (SSS) of the dielectric (curve 2). The subsequent measurement of the I – V characteristic reproduces under illumination a curve corresponding to the state of the SNA.

In FIG. 4, the subsequent switching after dielectric molding in the dark and in the light for the MIS structure on Si at a voltage V <0 on Au is illustrated. Curves 3 and 5 when switching from SHS to a low-impedance state in the dark and under lighting, respectively. Curves 4 and 6 in the SNA in the dark and under lighting, respectively. It can be seen that the illumination reduced the limiting effect of the resistance layer of the layer depleted in the main charge carriers in the semiconductor, increased the current in the SNA and decreased the threshold voltage for switching from SSS to SHS (compare curves 3 and 5).

A feature of the molding and switching curves of memristive MIS structures is the practical coincidence of currents in the initial state (IC) and SHS in the dark and in the light. This circumstance can be explained by the high resistance of the semiconductor and its weak dependence on lighting and the capture of carriers on the PS.

In FIG. 5 illustrates the effect of lighting on bipolar switching curves of a planar structure. The increase in currents when switching to light is due to a decrease in the value of the series resistance of the capacitor due to a decrease in the limiting resistance of the semiconductor lining (compare curves 7, 8 and 9, 10). It can be seen that for both switching polarities, the light current in the SNA state exceeds the corresponding current in the dark by 2 orders of magnitude. When illuminated, the multiplicity of the ratio of the current in the SNA state with respect to the SHS state also increases by two orders of magnitude. It is established that a decrease in the limiting resistance of the semiconductor wrap also leads to an increase in the speed of memristors due to a decrease in the RC value.

Example 2

Control the operation of an MDM memristor with an Au / Zr / YSZ / TiN structure on a silicon substrate.

The MDM structure (Fig. 1b) is formed on a Si (001) substrate coated with a ≈0.5 μm thick SiO ₂ layer, on top of which a lower capacitor plate with an area of ~ 1 cm ² from a TiN layer (25 nm) with a Ti sublayer (25 nm). The method of obtaining the YSZ layer and the upper lining (area ~ 10 ^-3 cm ² ) did not differ from that described above for the MIS capacitor.

The importance of the voltage and switching currents in the dielectric (which in the case of the MIS structure can be controlled by the state of the semiconductor wrap) is indicated by the dependences shown in FIG. 6. From the I – V characteristics of the switching of these dependences, it is seen that the limitation of the switching current led to a decrease in the current in the conducting state of the memristor (Fig. 6, curves 11-13). This was due to the sequential inclusion of ohmic resistance in the memristor circuit, which reduces the current and confirms the above-proposed mechanism of the influence of lighting associated with an increase in voltage and current through the dielectric due to a decrease in the resistance of the semiconductor lining.

Example 3

Controlling the operation of an MIS mesastructure with a pn junction facing the p-type conducting region to a dielectric, Au / Zr / YSZ / p-GaAs / n-GaAs / n + -GaAs / Sn /.

[К.В. Шалимова. Физика полупроводников. М., Энергоатомиздат, 1985. - 392 с.], где k - постоянная Больцмана, Т - температура в градусах Кельвина, q - заряд электрона, р₀ и n₀ - концентрации равновесных дырок и электронов, n_i-концентрация собственных носителей в GaAs и составило 1,3 В. Омическтй контакт к n+GaAs создается вжиганием в него электрическим разрядом фольги из Sn.The structure shown in FIG. 1c, they are formed on the basis of n ⁺ -GaAs single-crystal plates with the (001) orientation with n-GaAs layers ~ 1 μm thick with an equilibrium electron concentration n ₀ equal to 10 ¹⁷ cm ^-3 and p-GaAs layers ~ 0.1 μm thick with equilibrium hole concentration p ₀ equal to 1⋅10 ¹⁹ cm ^-3 obtained by the method of MOS - hydride epitaxy. YSZ films are applied to a surface formed by the magnetron method at a substrate temperature of 200 ° C. The thickness of the dielectric layer is 40 nm. A control transparent metal electrode made of Au (20 nm thick) with a Zr sublayer (3 nm thick) is applied to the dielectric surface by direct current magnetron sputtering to improve adhesion. The gallium arsenide pn junction is formed in the substrate to eliminate the influence of high-density PS that can form at the insulator – GaAs interface [N.L. Dmitruk. University News of the USSR. Physics, vol. 1, 38 (1980). IN AND. White, V.R. Belosludov. In the book. Modern problems of physics and surface chemistry of semiconductors. Novosibirsk (1988)]. The heavily doped p ⁺ -GaAs layer behaves like a metal and does not contain PS at the dielectric interface, and the p ⁺ -GaAs-n-GaAs interface does not contain PS, due to its homoepitaxiality. To eliminate leakage along the p-layer, a mesa structure was created and the pn junction boundary was irradiated with protons with an energy of 50 keV and a dose of 10 μC / cm ² to obtain an insulating layer (S.V. Tikhov, V.V. Martynov, A.N. Kalinin, EI Zorin. The effect of proton irradiation on the properties of the metal (Au) - anode oxide - gallium arsenide structure. Izvestiya VUZov. Physics. 1983, No. 5, pp. 89-92). The value of the contact potential difference in the transition was calculated by the formula

[K.V. Shalimova. Semiconductor Physics. M., Energoatomizdat, 1985. - 392 p.], Where k is the Boltzmann constant, T is the temperature in degrees Kelvin, q is the electron charge, p ₀ and n ₀ are the concentrations of equilibrium holes and electrons, n _i is the concentration of intrinsic carriers in GaAs was 1.3 V. The ohmic contact to n + GaAs is created by burning Sn foil with an electric discharge.

An exemplary view of the equilibrium energy diagram of the MIS MES structure with a pn junction is shown in FIG. 2, b.

The mesa structure is illuminated with a red beam from a LSR-660 1500 laser (wavelength 660 nm, radiation power 1.5 W) with a strip of 5 mm ² photon flux ≈ 3 × 10 ¹⁸ per second (BCP ≈ 6 × 10 ²¹ photons / cm ² ⋅c). The radiation intensity (value PPC) is reduced using neutral filters.

The effect of laser irradiation on currents in a conducting state for the mesa structure is shown in FIG. 7 and 8. It is characterized by a significant effect: the current values in the light are 4 orders of magnitude higher than those in the dark (Fig. 7, curves 16 and 17) and are practically inertia-free and strongly dependent on the level of illumination (Fig. 8, curves 18 and 19) .

Thus, the proposed method for controlling the operation of memristive MIS structures with the help of light makes it possible to adjust such switching parameters as the molding voltage and switching voltage, the ratio of currents (resistances) in the state of the SHS and SSS and the speed when reading the states of the IS and SHS due to changes the magnitude of the series resistance determined by the semiconductor. Reduces the likelihood of errors when reading the state of the memristor.

Claims (4)

1. A method of controlling the operation of a memristive capacitor metal-insulator-semiconductor structure, in which the dielectric and the semiconductor are connected in series with respect to each other, wherein the dielectric is made of a non-photosensitive material, and the semiconductor substrate is made of a photosensitive material containing dopant in concentrations of 10 ¹⁵ ÷ 10 ¹⁷ cm ^-3 , ensuring the commensurability of the capacitances or conductivities of the dielectric and the space charge region of the semiconductor and the absence of fixation Fermi equilibrium at the interface between a dielectric and a semiconductor, by adjusting the electric field strength and the current in the dielectric during its molding and switching due to a change in the resistance of the semiconductor substrate due to a change in the capacitance and conductivity of the space charge region in the semiconductor using high-intensity light 10 ¹⁸ ÷ 10 ²¹ photons / cm ² ⋅ s of structures from the side of the metal electrode and dielectric in the region of intrinsic photosensitivity of the semiconductor wrap. 2. The method according to p. 1, characterized in that for the implementation of the method using a MIS structure with a depleted layer at the interface of the insulator-semiconductor Au / Zr / YSZ / Sb / SiO ₂ / n-Si. 3. The method according to p. 1, characterized in that they use an MIS mesastructure with a pn junction facing the p-type conducting region to the dielectric, Au / Zr / YSZ / p-GaAs / n-GaAs / n + -GaAs / Sn /. 4. The method according to p. 1, characterized in that the photosensitivity of the proposed devices is determined by their own photosensitivity for silicon 400 ÷ 1100 nm and for GaAs - 400 ÷ 870 nm at room temperature.

Images