CN110148665B - Piezoelectric PN junction module with adjustable volt-ampere characteristics and regulation and control method and application thereof - Google Patents
Piezoelectric PN junction module with adjustable volt-ampere characteristics and regulation and control method and application thereof Download PDFInfo
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Abstract
The invention discloses a piezoelectric PN junction module with adjustable volt-ampere characteristics, a regulation method and application thereof, and belongs to the field of piezoelectric semiconductors. The piezoelectric PN junction module includes: the piezoelectric PN junction, the insulating substrate and the direct current source are connected; fixedly connecting the piezoelectric PN junction to the upper surface of an insulating base body through insulating glue in a point connection mode on two sides of the center of the piezoelectric PN junction, wherein the connection points on the two sides are symmetrical about the center of the piezoelectric PN junction; the direct current source is used for applying forward or reverse direct current bias to two ends of the piezoelectric PN junction; the volt-ampere characteristic of the piezoelectric PN junction can be regulated and controlled by changing the bending moment applied to the insulating substrate, turning and changing the position of the connecting point. The structure of the invention can mechanically regulate and control the piezoelectric PN junction through the insulating substrate, thereby obtaining a modular structure capable of changing the stress of the piezoelectric PN junction and providing a necessary foundation for the mechanical regulation and control and application research of the piezoelectric PN junction.
Description
Technical Field
The invention belongs to the field of piezoelectric semiconductors, and particularly relates to a mechanical regulation and control method for the volt-ampere characteristics of a piezoelectric PN junction and application thereof.
Background
The rapid development of high-tech technologies such as artificial intelligence and modern sensing requires new-generation microelectronic devices with new functions, such as human-computer interaction and compatibility, self-calibration, wireless manipulation and wireless energy supply, which mostly involve interface communication between natural people and electronic devices/systems. Most of the signals generated by the human body are mechanical motion signals (few are electrical signals), so that the interaction between the human body motion signals and the device signals needs to be considered inevitably, that is, the mechanical signals need to be converted into electrical signals or vice versa. In addition, in the human-computer interaction process, the interaction is inevitably interfered by external disturbance. Therefore, in order to achieve better human-computer interaction, the electronic device must have good controllability while having a mechanical-electrical signal interchange function.
For realizing the conversion of mechanical signals and electrical signals, the piezoelectric material is characterized in thatHas natural force electric coupling effect and is preferred. In which Pb (Zr, Ti) O3More commonly, are widely used in sensors, actuators and energy harvesters. They are insulating materials and are not suitable for electronic device applications.
Conventional electronic devices are based on silicon-based devices, but it is difficult for silicon-based devices to directly interact with mechanical signals, so that a medium is required for transmission in order to realize man-machine interaction, such as the translation of mechanical signals generated by a human body into electrical signals that can be "read" by the electronic device.
The piezoelectric semiconductor material integrates the piezoelectric effect and the semiconductor effect, can directly sense external mechanical signals and electric signals, and has wide application prospect in the fields of human-computer interaction, micro-electro-mechanical systems, nano robots and the like. In recent years, wurtzite-type piezoelectric semiconductors typified by ZnO and GaN have gradually become basic materials for innovative devices such as nanogenerators, piezoelectric field effect transistors, piezoelectric diodes, piezoelectric chemical sensors, and piezoelectric optoelectronic devices. However, when considering external interference or sudden situations, the working accuracy and stability of these piezoelectric semiconductor devices will be seriously interfered, even accidents are caused, and therefore, it is very important to control the working characteristics of the piezoelectric semiconductor devices. The piezoelectric PN junction is an important component of the piezoelectric semiconductor device, and thus if the physical characteristics of the piezoelectric PN junction can be controlled, the operating characteristics of the corresponding piezoelectric semiconductor device can be controlled.
Disclosure of Invention
The invention provides a piezoelectric PN junction module with adjustable volt-ampere characteristics, a regulation method and application thereof, aiming at designing a modular structure capable of changing stress based on a piezoelectric PN junction, so that the volt-ampere characteristics of the piezoelectric PN junction can be changed in a mechanical regulation mode based on the modular structure, further research and utilization are facilitated, and a theoretical basis and a feasible practical scheme are provided for regulation and control of the working characteristics of a piezoelectric semiconductor device.
In order to achieve the above object, according to an aspect of the present invention, there is provided a piezoelectric PN junction module having a tunable current-voltage characteristic, including: the piezoelectric PN junction is formed by a direct current source, a piezoelectric PN junction and an insulating substrate; fixedly connecting the piezoelectric PN junction to the upper surface of an insulating base body through insulating glue in a point connection mode on two sides of the center of the piezoelectric PN junction, wherein the connection points on the two sides are symmetrical about the center of the piezoelectric PN junction; the direct current source is used for applying forward or reverse direct current bias to two ends of the piezoelectric PN junction; the volt-ampere characteristic of the piezoelectric PN junction can be regulated and controlled by changing the bending moment applied to the insulating substrate, turning and changing the position of the connecting point.
Further, the piezoelectric PN junction material is ZnO, CdS or GaN.
Further, the insulating matrix is polystyrene.
In order to achieve the above object, according to another aspect of the present invention, there is provided a volt-ampere characteristic regulating method for a piezoelectric PN junction module with adjustable volt-ampere characteristics, where if a c-axis direction of a piezoelectric PN junction is P → N, the regulating method is any one of (a) to (e); if the c-axis direction of the piezoelectric PN junction is N → P, the control method is to change the tensile force applied in any one of (a) to (e) to the pressure force, and the applied pressure force to the tensile force:
(a) under forward bias, applying tension to the piezoelectric PN junction through the insulating base body, thereby reducing the current density output by the piezoelectric PN junction; or pressure is applied to the piezoelectric PN junction through the insulating substrate, so that the current density output by the piezoelectric PN junction is improved;
(b) under forward bias, applying tension to the piezoelectric PN junction through the insulating substrate, and generating reverse current under the forward bias when the tension is increased enough to offset the forward bias;
(c) under reverse bias, when reverse current flowing through the piezoelectric PN junction is saturated, pulling force is applied to the piezoelectric PN junction through the insulating base body, and therefore the saturation current density of the piezoelectric PN junction is reduced; or applying pressure to the piezoelectric PN junction through the insulating substrate so as to increase the saturation current density of the piezoelectric PN junction;
(d) under reverse bias, applying pressure to the piezoelectric PN junction through the insulating substrate, and generating forward current under the reverse bias when the pressure is increased enough to offset the reverse bias;
(e) reducing the distance between the connecting point and the space charge region boundary of the piezoelectric PN junction, thereby increasing the variation of current density caused by external loading of the insulating substrate; or the distance between the connecting point and the space charge region boundary of the piezoelectric PN junction is increased, so that the variation of the current density caused by the external loading of the insulating substrate is reduced.
In order to achieve the above object, according to another aspect of the present invention, there is provided a use of the piezoelectric PN junction module for improving the operation accuracy or sensitivity of a piezoelectric semiconductor device.
In order to achieve the above object, according to another aspect of the present invention, there is provided a method for improving the operation accuracy or sensitivity of a piezoelectric semiconductor device using the above piezoelectric PN junction module, wherein pre-stress is applied to the piezoelectric PN junction of the piezoelectric semiconductor device under forward bias, or the operation position of the piezoelectric semiconductor device is brought closer to the space charge region boundary of the piezoelectric PN junction.
In order to achieve the above object, according to another aspect of the present invention, there is provided a use of the piezoelectric PN junction module for improving stability of a piezoelectric semiconductor device.
In order to achieve the above object, according to another aspect of the present invention, there is provided a method for improving stability or reducing sensitivity of a piezoelectric semiconductor device using the above piezoelectric PN junction module, wherein a pretension force is applied to a piezoelectric PN junction of the piezoelectric semiconductor device under a forward bias, or an operating position of the piezoelectric semiconductor device is located farther from a space charge region boundary of the piezoelectric PN junction.
In order to achieve the above object, according to another aspect of the present invention, there is provided a use of the piezoelectric PN junction module for determining whether a load is overloaded.
In order to achieve the above object, according to another aspect of the present invention, there is provided a method for determining whether a load is overloaded by using the piezoelectric PN junction module, wherein if the final action result of the load on the piezoelectric PN junction is an axial tension, a forward bias of the piezoelectric PN junction is adjusted according to a limit value of the load, so that the axial tension generated on the piezoelectric PN junction when the load reaches the limit value is sufficient to counteract the forward bias, and the piezoelectric PN junction generates a reverse current under the forward bias; after the forward bias is set according to the limit value of the load, detecting a current signal output by the piezoelectric PN junction when the device works, and indicating that the load is overloaded when the current density output by the piezoelectric PN junction is detected to be changed from the forward direction to the reverse direction;
if the final action result of the load on the piezoelectric PN junction is embodied as axial pressure, adjusting the reverse bias voltage of the piezoelectric PN junction according to the limit value of the load, so that the axial pressure generated on the piezoelectric PN junction when the load reaches the limit value can sufficiently offset the reverse bias voltage, and the piezoelectric PN junction can generate forward current under the reverse bias voltage; after the reverse bias is set according to the limit value of the load, the current signal output by the piezoelectric PN junction is detected when the work is carried out, and the overload of the load is indicated when the current density output by the piezoelectric PN junction is detected to be changed from the reverse direction to the forward direction.
In general, compared with the prior art, the above technical solution contemplated by the present invention can obtain the following beneficial effects:
1. the structure of the invention can mechanically regulate and control the piezoelectric PN junction through the insulating substrate, thereby obtaining a modular structure capable of changing the stress of the piezoelectric PN junction and providing a necessary foundation for the mechanical regulation and control and application research of the piezoelectric PN junction.
2. The piezoelectric PN junction module based on the invention provides various regulation and control modes, and provides various feasible guidance schemes for solving corresponding problems encountered in practical engineering application.
3. The invention provides specific applications, and provides corresponding solutions and directions for common problems in industry, such as load detection, safety monitoring, interference resistance, precision and sensitivity improvement and the like.
Drawings
Fig. 1 is a schematic structural view of a piezoelectric PN junction module according to a preferred embodiment of the present invention;
FIG. 2 is a schematic flow diagram of a preferred embodiment of the present invention;
FIG. 3 is a schematic illustration of piezoelectric PN junction loading in accordance with a preferred embodiment of the present invention;
fig. 4(a) -4 (e) are electrical quantity distribution rules after the piezoelectric PN junction is loaded under the bias voltage of 0.05V according to the preferred embodiment of the present invention, where 4(a) is the potential distribution under different load, 4(b) is the redistribution rule of the initial current carrier under different tensile force, and 4(c) is the redistribution rule of the initial current carrier under different pressure; 4(d) is the distribution of the non-equilibrium carriers under the action of different tensile forces, and 4(e) is the distribution of the non-equilibrium carriers under the action of different compressive forces
Fig. 5(a) is a voltage-current characteristic curve of a piezoelectric PN junction under the influence of different loads under forward bias according to a preferred embodiment of the present invention;
FIG. 6(a) is a voltage-current characteristic curve of a piezoelectric PN junction under the reverse bias and under the influence of different loads according to a preferred embodiment of the invention;
fig. 7(a) and 7(b) show the influence of different loading points on the voltammetry characteristics of the piezoelectric PN junction according to the preferred embodiment of the present invention, where 7(a) is the comparison of the voltammetry characteristics under the influence of different loading positions at σ -10MPa with the voltammetry characteristics under the influence of σ -0 MPa, i.e., unloaded, and 7(b) is the comparison of the voltammetry characteristics under the influence of different loading positions at σ -10MPa with the voltammetry characteristics under the influence of σ -0 MPa, i.e., unloaded.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1, a piezoelectric PN junction module with adjustable current-voltage characteristics according to a preferred embodiment of the present invention includes: the device comprises a direct current source 1, a piezoelectric PN junction 2 and an insulating base body 3; the piezoelectric PN junction 2 is fixedly connected to the upper surface of an insulating base body 3 through insulating glue in a point connection mode on two sides of the center of the piezoelectric PN junction 2, and connection points 4 on two sides are symmetrical about the center of the piezoelectric PN junction; the direct current source 1 is used for applying forward or reverse direct current bias to two ends of the piezoelectric PN junction 2; the volt-ampere characteristic of the piezoelectric PN junction can be regulated and controlled by changing the bending moment applied to the insulating base body 3, turning and changing the position of the connecting point.
The piezoelectric PN junction 2 material is ZnO, CdS or GaN or other common piezoelectric semiconductor materials. The insulating matrix 3 is preferably polystyrene.
As shown in fig. 2, the main steps of the present invention are as follows:
(1) establishing a theoretical model of the piezoelectric PN junction module under the combined action of bias voltage and axial mechanical loading;
(2) based on a semiconductor theory and starting from the relationship between potential and a carrier, obtaining an analytical relationship between bias voltage, loading magnitude, loading position and current density flowing through a piezoelectric PN junction;
(3) on the basis of the analytical relationship in the step (2), the regulation and control functions of the loading size and the loading position on the output current density of the piezoelectric PN junction are respectively analyzed by a control variable method, and the method comprises the following steps:
controlling the external bias voltage and the loading position to be unchanged, regulating the loading size and regulating the output current density of the piezoelectric PN junction;
controlling the magnitude of the external bias voltage and the loading to be unchanged, regulating and controlling the position of a loading point, and regulating and controlling the output current density of the piezoelectric PN junction;
(4) repeating the step (3) under different bias voltages to obtain the output current density of the piezoelectric PN junction under each bias voltage, and further respectively obtaining a volt-ampere characteristic curve under the influence of a loading position and a volt-ampere characteristic curve under the influence of a loading size, so that one or more of the following mechanical regulation and control modes are carried out on the volt-ampere characteristics of the piezoelectric PN junction according to the two volt-ampere characteristic curves:
(a) under forward bias, applying tension to the piezoelectric PN junction through the insulating base body, thereby reducing the current density output by the piezoelectric PN junction; or pressure is applied to the piezoelectric PN junction through the insulating substrate, so that the current density output by the piezoelectric PN junction is improved;
(b) under forward bias, applying tension to the piezoelectric PN junction through the insulating substrate, and generating reverse current under the forward bias when the tension is increased enough to offset the forward bias;
(c) under reverse bias, when reverse current flowing through the piezoelectric PN junction is saturated, pulling force is applied to the piezoelectric PN junction through the insulating base body, and therefore the saturation current density of the piezoelectric PN junction is reduced; or applying pressure to the piezoelectric PN junction through the insulating substrate so as to increase the saturation current density of the piezoelectric PN junction;
(d) under reverse bias, applying pressure to the piezoelectric PN junction through the insulating substrate, and generating forward current under the reverse bias when the pressure is increased enough to offset the reverse bias;
(e) reducing the distance between the connecting point and the space charge region boundary of the piezoelectric PN junction, thereby increasing the variation of current density caused by external loading of the insulating substrate; or the distance between the connecting point and the space charge region boundary of the piezoelectric PN junction is increased, so that the variation of the current density caused by the external loading of the insulating substrate is reduced.
The control methods (a) to (e) are exemplified by the c-axis direction of the piezoelectric PN junction being P → N; if the c-axis direction of the piezoelectric PN junction is N → P, the control method is to change the tensile force applied in any one of (a) to (e) to the compressive force, and the applied compressive force to the tensile force.
In the invention, in order to realize that the electrical signal converted from the mechanical signal is deeply transmitted into the main structure of the device, a mechanical regulation method capable of effectively regulating the volt-ampere characteristic of the piezoelectric PN junction is designed based on the piezoelectricity and the semiconductor characteristic of the piezoelectric semiconductor.
The regulation and control method and the theoretical basis of the present invention are specifically described below:
(1) fig. 1 establishes a piezoelectric PN junction module under the combined action of bias voltage and axial mechanical loading, and gives a theoretical schematic diagram as shown in fig. 3 based on semiconductor theory. In fig. 3, a piezoelectric long PN junction composed of P-type and N-type piezoelectric semiconductors, wherein: l ispAnd LnAre respectively two ends of a piezoelectric PN junctionpAnd lnLoad points, x, for P and N regions, respectivelypAnd xnIs the boundary of the space charge region. In addition, the c-axis of the piezoelectric semiconductor is parallel to the x-axis and points in the positive x-axis direction.
(2) Based on the theoretical model in the step (1), starting from the relationship between potential and current carriers, obtaining an analytical relationship among bias voltage, loading size, loading position and current density flowing through the piezoelectric PN junction;
the method for establishing the theoretical model of the piezoelectric PN junction according to the semiconductor theory comprises the following steps:
due to the piezoelectric effect, the electrical displacement D is expressed as:
σ＝cS-eE,D＝eS+εE、
m2＝e2/(cε)。
wherein S is strain, E is electric field, c is elastic constant, E is piezoelectric constant, epsilon dielectric constant, m is intermediate variable, sigma is stress for representing loading magnitude,
is a correction value of the dielectric constant. If loading σ is a constant value, based on the depletion layer assumption, the gaussian theorem of the piezoelectric PN junction model can be written as:
wherein: phi is the potential, NA、NDDoping concentrations, p, of respectively acceptor and donorp0(x)、np0(x) Respectively the hole concentration and the electron concentration after redistribution of the P region, Pn0(x)、nn0(x) Respectively the hole concentration and the electron concentration of the redistributed N region. In addition, q is 1.602 × 10-19C。
The relationship between the potential of the P region and the potential of the N region in the piezoelectric PN junction and the concentration of redistributed carriers can be represented as follows:
wherein,
niis the intrinsic carrier concentration. For analyzing small injection non-equilibrium piezoelectric PN junction, in the formula
According to semiconductor theory
V is a bias voltage provided by an external dc source. K is Boltzmann's constant,. phi is the potential, T is the temperature, and 300K is assumed in this example. (p)p0、np0) And (p)n0、nn0) The initial hole and electron concentrations of the P and N regions, respectively. Equations (1) and (2) can be solved based on the boundary condition that the boundary electric displacement and the space charge region boundary electric field are zero and the continuity condition that the electric potential and the electric displacement at each connection point are continuous.
If the two sides of the space charge region are loaded equally, the potential difference of the space charge region and the position of the space charge region after loading can be finally expressed as:
in the case of small implants, the influence of unbalanced minority carriers on the electric field is a high order small quantity, negligible with respect to the influence of the deformation on the electric field. Thus, according to perturbation theory, the second step of modeling may substitute the potential solved in the first step into the diffusion equation for the non-equilibrium carriers, solving for the non-equilibrium carriers. The diffusion equation for non-equilibrium carriers can be written as:
wherein: (mu.) an、μp)、(Dn、Dp) And (tau)n、τp) Mobility, diffusion coefficient and recombination time of electrons and holes, respectively. Δ np(x) And Δ pn(x) The non-equilibrium minority carrier concentrations of the P region and the N region, respectively.
In particular, x ═ xp、xnWhen the temperature of the water is higher than the set temperature,
and
the non-equilibrium minority carrier concentrations injected at the boundaries of the P region and the N region respectively. Equation (4) can be solved according to the boundary condition that the boundary unbalanced minority carrier is zero and the continuity condition of the current and the carrier continuity at the loading point.
The total current density J can be determined by the sum of minority current densities at the two boundaries of the space charge region, i.e., when x is-xp、xnThe method comprises the following steps: j is Jn(-xp)+Jp(xn) Wherein:
Jn(x)、Jp(x) Respectively, the current densities of P-region non-equilibrium electrons and N-region non-equilibrium holes.
(3) On the basis of the theoretical model in the step (2), the regulation and control functions of the loading size and the loading position on the output current density of the piezoelectric PN junction are respectively analyzed by a control variable method, and the method comprises the following steps:
controlling the external bias voltage and the loading position to be unchanged, regulating the loading size and regulating the output current density of the piezoelectric PN junction;
controlling the magnitude of the external bias voltage and the loading to be unchanged, regulating and controlling the position of a loading point, and regulating and controlling the output current density of the piezoelectric PN junction;
the regulation method of the present invention is described below in a specific example. Taking the CdS piezoelectric PN junction with the same doping concentration of the P region and the N region as an example, the elasticity, the piezoelectricity and the dielectric constant are respectively 93.8GPa for C and 0.44C/m for e2,ε＝9.53ε0In which epsilon0Is the dielectric constant in vacuum. The drift coefficient and diffusion coefficient of the carriers are respectively:
μn＝0.034m2/V·s、μp＝0.005m2/V·s、
and
the intrinsic carrier concentration, the multi-carrier concentration and the doping concentration are respectively selected as follows:
ni＝1×1016(m-3)、pp0＝nn0＝1×1021(m-3)、NA＝ND≈1×1021(m-3)
in FIGS. 4(a) to 6(a), L is the numberp＝Ln＝10lpAnd
the analysis was performed under conditions in which:
is the initial space charge region position under the unloaded condition, and can be obtained due to the same doping concentration at two ends:
fig. 4(a) -4 (e) show distribution rules of different loaded potentials and carriers under the action of a small injection forward bias of 0.05V. As can be seen from FIG. 4(a), under the action of a pair of pulling forces, the increment of the potential of the P-region loading region is negative, and the increment of the potential of the N-region loading region is positive; on the contrary, under the action of a pair of pressures, the potential increment of the P area loading area is positive, the potential increment of the N area loading area is negative, and therefore, the corresponding potential energy of electrons is changed. Under the action of tensile force, the change of electron potential energy enables the intrinsic energy level of electrons in the P region to be increased, and the intrinsic energy level of electrons in the N region to be decreased. Similarly, under pressure, the intrinsic energy level of the P-region electron decreases, while the intrinsic energy level of the N-region electron increases. Thus, under forward bias, the pulling force will cause the initial majority concentration near the load point to increase and the minority concentration to decreaseSo that the PN junction barrier is increased, as shown in FIG. 4 (b); conversely, the pressure will decrease the initial majority concentration and increase the minority concentration near the loading point, thereby lowering the PN junction barrier, as shown in fig. 4 (c). Fig. 4(d) and 4(e) are distribution diagrams of non-equilibrium carriers. As can be seen from fig. 4(d) and 4(e), under the action of the pulling force, the carriers are more difficult to break through the barrier region, so that the nonequilibrium carriers injected from the boundary are reduced along with the increase of the pulling force; on the contrary, under the action of pressure, carriers are easier to break through the barrier region, so that the nonequilibrium carriers injected from the boundary are increased along with the increase of the pressure. The carrier concentration on the vertical axis in FIGS. 4(d) and 4(e) is dimensionless
Where n represents the electron concentration and p represents the hole concentration. In addition, under the action of tensile force, the concentration of non-equilibrium electrons near a P region loading point is sharply reduced due to the increase of potential energy; conversely, under pressure, the concentration of non-equilibrium electrons near the P-region loading point increases dramatically due to the decrease in potential energy. Further, the current density value flowing through the PN junction under the bias of 0.05V can be obtained from the equation (5).
(4) And (4) repeating the step (3) under different bias voltages, obtaining the output current density of the piezoelectric PN junction under each bias voltage, further respectively obtaining a volt-ampere characteristic curve under the influence of the loading size and a volt-ampere characteristic curve under the influence of the loading position, and accordingly obtaining different regulation and control modes.
Fig. 5(a) shows a regulation rule of the voltage-current characteristics of the piezoelectric PN junction under forward bias by mechanical loading. As can be seen from fig. 5(a), under forward bias, the potential barrier of the space charge region is increased by the piezoelectric PN junction under the action of a pair of tensile forces, so that the carriers are more difficult to break through, and the current density flowing through the space charge region is reduced corresponding to the increase of the resistance of the potential barrier; on the contrary, the potential barrier of the space charge region is lowered under the action of a pair of pressures, so that the carriers are easier to break through, and the current density of the space charge region flowing through is increased corresponding to the reduction of the resistance of the potential barrier region. Thus, under forward bias, applying a pair of pressures corresponds to increasing the forward bias; and applying a pair of pulling forces corresponds to reducing the forward bias. In addition, it is worth mentioning: under forward bias, when the pulling force is increased enough to offset the forward bias, the piezoelectric PN junction can also generate reverse current under the forward bias.
Fig. 6(a) shows a regulation rule of the voltage-current characteristics of the piezoelectric PN junction under the reverse bias by the mechanical loading. As can be seen from fig. 6(a), when the reverse current is not saturated, the reverse current density is greatly affected by the bias voltage, and the pulling force is applied, which is equivalent to increasing the reverse bias voltage, thereby increasing the absolute value of the current density flowing through the piezoelectric PN junction; and applying pressure, which corresponds to reducing the reverse bias, reduces the absolute value of the current density flowing through the piezoelectric PN junction. When the reverse current is saturated, the reverse current is less influenced by bias voltage, and the initial minority carrier concentration at the boundary is reduced due to the application of pulling force, so that minority carriers are more difficult to be extracted reversely, and the absolute value of the current density flowing through the piezoelectric PN junction is reduced; and the application of pressure will result in an increase in the initial minority carrier concentration at the boundary, making it easier for minority carriers to be extracted in the reverse direction, thereby increasing the absolute value of the current density flowing through the piezoelectric PN junction.
Fig. 7(a), 7(b) show the effect of different loading points under compression and tension of 10MPa on the volt-ampere characteristics of piezoelectric PN junctions. As can be seen from fig. 7(a) and 7(b), the closer the loading point is to the space charge region boundary, the greater the amount of change in current density due to stress. The phenomenon is that the closer the loading point is to the boundary of the space charge region, the shorter the action region of the weakening effect generated by the redistribution of the current carriers is, and therefore, the stronger the influence of external loading on the space charge region is; conversely, the farther the loading point is from the boundary of the space charge region, the longer the action zone of the carrier redistribution for weakening effect is, and the weaker the influence of external loading on the space charge region is. Therefore, the closer the loading point is to the space charge region, the more obvious the regulation effect is.
The application of the invention is described below with reference to several specific control cases:
as shown in FIG. 5(a), if an instrument provides an operating bias voltage of 0.10V to the piezoelectric PN junction, and the pressure applied to the piezoelectric PN junction is provided by a load, the current instrument can only detect 0.002A/m2As can be seen from FIG. 5(a), the bias voltage is set at 0.10VThe current density output by the pressure load below 5MPa is lower than 0.002A/m2Therefore, it is difficult for the apparatus to detect a pressure load of 5MPa or less.
However, if a pressure of 5MPa is preset on the piezoelectric PN junction, when a load of 5MPa is applied to the piezoelectric PN junction, the pressure applied to the piezoelectric PN junction is actually 10MPa, and the current density output at this time is 0.0078A/m2And can be detected by an instrument. Similarly, the pressure load below 5MPa can be detected, that is, the sensitivity of the piezoelectric PN junction in response to the pressure load is improved by applying the pre-pressure to improve the output current density of the piezoelectric PN junction, so that the sensitivity of the instrument having the piezoelectric PN junction is also improved. Similarly, according to fig. 7(a), the working position of the piezoelectric semiconductor device is closer to the space charge region boundary of the piezoelectric PN junction, and the sensitivity of the piezoelectric PN junction in response to the pressure load is improved, so that the sensitivity of the instrument having the piezoelectric PN junction is improved, and the piezoelectric PN junction can be applied to a pressure sensor to more accurately detect the target pressure value.
Accordingly, the method for improving the stability or decreasing the sensitivity of the piezoelectric semiconductor device is opposite to the above method, and for example, when the piezoelectric semiconductor device is operated under a forward bias, a pretension force needs to be applied to the piezoelectric PN junction of the piezoelectric semiconductor device, or the operating position of the piezoelectric semiconductor device needs to be farther away from the space charge region boundary of the piezoelectric PN junction. Improving the stability or reducing the sensitivity of the piezoelectric semiconductor device can generally resist some unstable environmental factors, avoiding false triggering. Still taking the above-mentioned instrument as an example, if we preset a tension of 5MPa, the current density output by the piezoelectric PN junction will exceed 0.002A/m when the pressure provided by the load exceeds 10MPa2And thus detected by the instrument, thereby avoiding false triggering of an external pressure lower than 10MPa, for example, applied to a pressure response switch, and adjusting the magnitude of the pretension force according to actual conditions so that the pretension force can be triggered above a specified pressure.
In addition, it should be noted that the aforementioned pressure and tension for regulating the piezoelectric PN junction are based on the result acting on the axial direction of the piezoelectric PN junction. For example, if the piezoelectric PN junction 2 is fixed to the upper surface of the insulating base 3 according to fig. 1, then if the insulating base 3 is fixed at both ends and a tensile force is applied downward with respect to the insulating base 3 in the middle of the insulating base 3, the tensile force is actually finally applied to both ends of the insulating base 3, resulting in a bending moment M that causes the piezoelectric PN junction to be pressed in the axial direction.
If fig. 1 is turned upside down, the insulating base 3 is above the piezoelectric PN junction 2: if the two ends of the insulating matrix 3 are fixed and a downward pressure is applied in the middle of the insulating matrix 3, the pressure actually forces the two connection points away from each other, causing the piezoelectric PN junction to be pulled axially, and the effect on the piezoelectric PN junction is a pulling force; however, if the insulating base body 3 is fixed at the center and downward pressure is applied to both ends of the insulating base body 3, the pressure actually urges the two connection points to approach each other, causing the piezoelectric PN junction to be pressed axially, and the result of the action on the piezoelectric PN junction is pressure.
In addition, the insulating base body 3 can be directly adhered or fixed on the surface of the object to be measured integrally, so that the insulating base body deforms synchronously along with the surface deformation of the object to be measured, and the axial stress of the piezoelectric PN junction is changed. Therefore, the tensile force and the compressive force for regulating the piezoelectric PN junction should be determined in combination with the actual use scenario of the piezoelectric PN junction module of the present invention.
Since the modeling analysis and the mechanical control are both performed along the positive direction of the c-axis of the piezoelectric PN junction along the x-axis, i.e., the c-axis direction is P → N, it can be known that, if the c-axis direction of the piezoelectric PN junction is along the negative direction of the x-axis, i.e., the c-axis direction is N → P, the tensile force applied in the steps (a) - (e) when the c-axis direction is P → N should be changed to the compressive force, and the applied compressive force should be changed to the tensile force.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. The utility model provides a piezoelectricity PN junction module of volt-ampere characteristic adjustable which characterized in that includes: the piezoelectric PN junction structure comprises a direct current source (1), a piezoelectric PN junction (2) and an insulating base body (3); the piezoelectric PN junction (2) is fixedly connected to the upper surface of an insulating base body (3) through insulating glue in a point connection mode on two sides of the center of the piezoelectric PN junction (2), and connection points (4) on two sides are symmetrical about the center of the piezoelectric PN junction; the direct current source (1) is used for applying forward or reverse direct current bias to two ends of the piezoelectric PN junction (2); the volt-ampere characteristic of the piezoelectric PN junction can be regulated and controlled by changing the bending moment applied to the insulating base body (3), turning and changing the position of a connecting point.
2. The piezoelectric PN junction module with adjustable volt-ampere characteristics as claimed in claim 1, wherein the material of the piezoelectric PN junction (2) is ZnO, CdS or GaN.
3. A piezoelectric PN junction module with adjustable current-voltage characteristics according to claim 1, wherein the insulating matrix (3) is polystyrene.
4. The volt-ampere characteristic regulating method of the piezoelectric PN junction module with the adjustable volt-ampere characteristic as claimed in any one of claims 1 to 3, wherein if the c-axis direction of the piezoelectric PN junction is P → N, the regulating method is any one of (a) to (e); if the c-axis direction of the piezoelectric PN junction is N → P, the control method is to change the tensile force applied in any one of (a) to (e) to the pressure force, and the applied pressure force to the tensile force:
(a) under forward bias, applying tension to the piezoelectric PN junction through the insulating base body, thereby reducing the current density output by the piezoelectric PN junction; or pressure is applied to the piezoelectric PN junction through the insulating substrate, so that the current density output by the piezoelectric PN junction is improved;
(b) under forward bias, applying tension to the piezoelectric PN junction through the insulating substrate, and generating reverse current under the forward bias when the tension is increased enough to offset the forward bias;
(c) under reverse bias, when reverse current flowing through the piezoelectric PN junction is saturated, pulling force is applied to the piezoelectric PN junction through the insulating base body, and therefore the saturation current density of the piezoelectric PN junction is reduced; or applying pressure to the piezoelectric PN junction through the insulating substrate so as to increase the saturation current density of the piezoelectric PN junction;
(d) under reverse bias, applying pressure to the piezoelectric PN junction through the insulating substrate, and generating forward current under the reverse bias when the pressure is increased enough to offset the reverse bias;
(e) reducing the distance between the connecting point and the space charge region boundary of the piezoelectric PN junction, thereby increasing the variation of current density caused by external loading of the insulating substrate; or the distance between the connecting point and the space charge region boundary of the piezoelectric PN junction is increased, so that the variation of the current density caused by the external loading of the insulating substrate is reduced.
5. Use of a piezoelectric PN junction module as claimed in any one of claims 1 to 3 for improving the working accuracy or sensitivity of a piezoelectric semiconductor device.
6. The method for improving the working accuracy or sensitivity of the piezoelectric semiconductor device by using the piezoelectric PN junction module as claimed in any one of claims 1 to 3, wherein under the forward bias, pre-pressure is applied to the piezoelectric PN junction of the piezoelectric semiconductor device, or the working position of the piezoelectric semiconductor device is closer to the space charge region boundary of the piezoelectric PN junction.
7. Use of a piezoelectric PN junction module as claimed in any one of claims 1 to 3 for improving the stability of a piezoelectric semiconductor device.
8. The method for improving the stability or reducing the sensitivity of the piezoelectric semiconductor device by using the piezoelectric PN junction module as claimed in any one of claims 1 to 3, characterized in that under forward bias, a pretension force is applied to the piezoelectric PN junction of the piezoelectric semiconductor device, or the working position of the piezoelectric semiconductor device is further away from the space charge region boundary of the piezoelectric PN junction.
9. Use of a piezoelectric PN junction module as claimed in any one of claims 1 to 3 for determining whether a load is overloaded.
10. The method for judging whether the load is overloaded by utilizing the piezoelectric PN junction module according to any one of claims 1 to 3, wherein if the final action result of the load on the piezoelectric PN junction is embodied as axial tension, the forward bias of the piezoelectric PN junction is adjusted according to the limit value of the load, so that the axial tension generated on the piezoelectric PN junction when the load reaches the limit value can sufficiently counteract the forward bias, and the piezoelectric PN junction can generate reverse current under the forward bias; after the forward bias is set according to the limit value of the load, detecting a current signal output by the piezoelectric PN junction when the device works, and indicating that the load is overloaded when the current density output by the piezoelectric PN junction is detected to be changed from the forward direction to the reverse direction;
if the final action result of the load on the piezoelectric PN junction is embodied as axial pressure, adjusting the reverse bias voltage of the piezoelectric PN junction according to the limit value of the load, so that the axial pressure generated on the piezoelectric PN junction when the load reaches the limit value can sufficiently offset the reverse bias voltage, and the piezoelectric PN junction can generate forward current under the reverse bias voltage; after the reverse bias is set according to the limit value of the load, the current signal output by the piezoelectric PN junction is detected when the work is carried out, and the overload of the load is indicated when the current density output by the piezoelectric PN junction is detected to be changed from the reverse direction to the forward direction.
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