CN102244002B - Preparation method of heterojunction with metal/semiconductor nanometer wire crossing structure - Google Patents

Abstract

The invention discloses a method for preparing a metal/semiconductor nanowire cross structure heterojunction. Two pairs of metal thin film electrodes are prepared on a semiconductor nanowire by a single ultraviolet lithography method, wherein a pair of metal thin film electrodes pass through the semiconductor nanowire connected to the semiconductor nanowires in ohmic contact; an alternating electric field is applied to another pair of metal thin film electrodes, and the metal nanowires are adsorbed to the pair of metal thin film electrodes on which the alternating electric field is applied, and the metal nanowires intersect with the semiconductor nanowires to form a Schottky contacts form metal/semiconductor nanowire cross-structure heterojunctions. The preparation method of the present invention is simple, stable and reliable, and can be applied to electronic components and optical components of various nanometer sizes including Schottky diodes or metal-semiconductor field effect transistors with metal nanowires as gates, such as nanometer Photodetectors, gas sensors, solar cells, etc.

Description

Preparation method of metal/semiconductor nanowire cross structure heterojunction

1. Technical field

The invention relates to a method for preparing a semiconductor device, in particular to a method for preparing a metal/semiconductor nanowire intersection structure heterojunction.

2. Background technology

Metal/semiconductor heterojunctions play an important role in the fabrication of semiconductor devices, especially micro-nano devices. In semiconductor devices, it is usually necessary to use a metal that forms a good ohmic contact with the semiconductor as an electrode to input or output current, and a diode can be made by using the metal-semiconductor rectifying contact characteristic, that is, a Schottky diode. Compared with the p-n junction diode, the Schottky junction diode is mainly formed by the majority of carriers in the semiconductor entering the metal because the forward current is the majority carrier device, there is no charge storage effect, and it has high switching frequency and positive It has the advantages of low conduction voltage, no minority carrier lifetime and reverse recovery problems, so it has better photoelectric characteristics, and is more suitable for ultra-high-speed switching devices, photodetectors, solar cells, and semiconductor lasers.

At present, the formation methods of metal/semiconductor nanowire heterostructures mainly include the following: 1. Liquid phase synthesis of semiconductor nanowires embedded with metal particles to form a one-dimensional nanostructure containing metal/semiconductor heterojunctions; 2. Combining template method and electrochemical deposition technology to deposit semiconductor and metal materials in stages, form metal/semiconductor nanowire heterojunction in the template or selectively deposit metal particles on the top of the nanowire array deposited by template method to form metal particles/semiconductor Nanowire heterojunction; 3. On a single semiconductor nanowire, epitaxially grow a metal film on a selected area or through secondary photolithography (electron beam lithography or ultraviolet lithography) and electron beam evaporation technology, respectively vapor-deposit a A group of metal electrodes in ohmic contact and a group of metal electrodes in Schottky contact form a metal film/semiconductor nanowire heterojunction. The first two methods require strict control of the experimental process, and it is difficult to control the heterojunction on the target device, while the third method is expensive in equipment, and the secondary photolithography process is more complicated, and will affect the performance of the device to a certain extent . Therefore, a stable, reliable, and technically available method for preparing a metal/semiconductor nanowire cross-structure heterojunction is still of great significance in the field of nanodevices.

3. Contents of the invention

The present invention aims to provide a method for preparing a metal/semiconductor nanowire cross-structure heterojunction with a simple preparation method and easy realization in view of the shortcomings of the above-mentioned prior art.

The present invention solves technical problem and adopts following technical scheme:

The characteristics of the preparation method of the metal/semiconductor nanowire cross structure heterojunction of the present invention are: the semiconductor nanowires 3 are horizontally dispersed on the silicon wafer 1 covered with the insulating layer 2, and the insulating layer 2 is formed on the insulating layer 2 by a method of ultraviolet lithography. Prepare two pairs of metal thin film electrodes, wherein a pair of metal thin film electrodes 4 are connected through the semiconductor nanowires 3, and the metal thin film electrodes 4 are in ohmic contact with the semiconductor nanowires 3; the suspension liquid dispersed with the metal nanowires 5 is dropped on the On the insulating layer 2, an alternating electric field is applied to another pair of metal thin film electrodes 6, so that the metal nanowires 5 are adsorbed on the metal thin film electrodes 6, and the metal nanowires 5 intersect with the semiconductor nanowires 3 to form a Schottky contact. , forming a metal/semiconductor nanowire cross-structure heterojunction.

The method for preparing the metal/semiconductor nanowire cross structure heterojunction of the present invention is also characterized in that: the semiconductor nanowire 3 and the metal nanowire 5 are single crystal structures with a length not less than 10 μm and a diameter less than 1 μm.

The preparation method of the metal/semiconductor nanowire cross structure heterojunction of the present invention is also characterized in that: the semiconductor nanowire 3 is a simple semiconductor, II-VI semiconductor compound, I-VI semiconductor compound or III-V semiconductor compound ;

The preparation method of metal/semiconductor nanowire cross structure heterojunction of the present invention is also characterized in that: the simple semiconductor is Si or Ge; the II-VI group semiconductor compound is ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe or CdTe; the I-VI group semiconductor compound is CuO, CuS, CuSe or CuTe; the III-V group semiconductor compound is GaAs or In ₂ Sb ₃ ;

The feature of the preparation method of the metal/semiconductor nanowire cross structure heterojunction of the present invention is also that: when the semiconductor nanowire 3 is an n-type semiconductor, the two pairs of metal thin film electrodes are composed of In, Ti, Ag, Al One or more of them, the work function of the two pairs of metal film electrodes is lower than the work function of the semiconductor nanowire 3; the metal nanowire 5 is composed of one or more of Pt, Au, Ni, Cu One, the work function of the metal nanowire 5 is greater than the affinity between the semiconductor nanowire 3 and electrons;

When the semiconductor nanowire 3 is a p-type semiconductor, the two pairs of metal thin film electrodes include one or more of Pt, Au, Ni, Cu, and the work function of the two pairs of metal thin film electrodes is greater than the The work function of the semiconductor nanowire 3; the metal nanowire 5 includes one or more of In, Ti, Ag, and Al, and the work function of the metal nanowire 5 is lower than that of the semiconductor nanowire 3 and electrons. affinity.

The preparation process of the present invention is as follows:

Disperse semiconductor nanowires 3 horizontally on a silicon wafer 1 covered with an insulating layer 2 of 100-500nm, use a mask plate to photoetch two pairs of electrode patterns on the insulating layer through one-step photolithography, wherein a pair of electrode patterns pass through the semiconductor nanowires Connected, and then use electron beam evaporation technology to vapor-deposit two pairs of electrode patterns to obtain two pairs of metal thin film electrodes. A pair of metal film electrodes 4 communicated with the semiconductor nanowires are in ohmic contact with the semiconductor nanowires 3 . Subsequently, the pre-synthesized metal nanowires 5 are dispersed in absolute ethanol, deionized water or isopropanol to form a suspension, the suspension is dropped on the insulating layer 2, and the two ends of the other pair of metal thin film electrodes 6 are added When an alternating current is applied, the metal nanowires 5 are polarized in an alternating electric field and move along the direction of increasing electric field strength until a pair of metal thin film electrodes 6 applied with an alternating current are respectively in contact with the two ends of the metal nanowires 5, and the metal nanowires 5 intersects with the semiconductor nanowire 3 to form a Schottky contact, forming a stable metal/semiconductor nanowire cross-structure heterojunction.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

The invention prepares the metal nanowires and the semiconductor nanowires respectively, and can directly complete the formation of the heterojunction and the preparation of the device through one photolithography and the use of electric field adsorption, and the process is simple and easy. In addition, the metal nanowire in Schottky contact with the semiconductor nanowire can also be used as a gate to construct a metal-semiconductor field effect transistor. Because the heterojunction has very small junctions, it is more suitable for nanometer photodetectors and other fields, and is expected to obtain higher sensitivity and faster detection speed.

4. Description of drawings

Fig. 1 is a flow chart of the preparation method of the metal/semiconductor nanowire cross structure heterojunction of the present invention.

Fig. 2 is a schematic structural diagram of a metal/semiconductor nanowire cross-structure heterojunction device of the present invention.

Among them, 1 is a silicon wafer, 2 is an insulating layer, 3 is a semiconductor nanowire, 4 is a pair of metal thin film electrodes connected with the semiconductor nanowire, 5 is a metal nanowire, and 6 is a pair of metal thin film electrodes connected with the metal nanowire .

5. Specific implementation

The preparation method of the metal/semiconductor nanowire cross structure heterojunction of the present invention will be described in detail below in conjunction with the accompanying drawings, and the non-limiting examples are as follows.

Example 1:

A clean silicon wafer with a 300nm _SiO2 insulating layer is attached to a substrate grown by chemical vapor deposition (CVD) with p-type ZnS nanowires, and the silicon wafer is gently pushed along the horizontal direction, and through directional friction, The uniform and horizontal dispersion of the ZnS nanowires on the silicon wafer is realized, and the dispersion density is about 2-10 wires/mm ² through electron microscope observation. After the positive photoresist was evenly spin-coated, a specific mask was used for ultraviolet exposure and development, and two pairs of electrode patterns were photoetched. The distance between the tips of each pair of electrodes was 5 μm, and a pair of electrode patterns were connected through semiconductor nanowires. After that, metal Au with a thickness of 50nm is evaporated by electron beam evaporation technology as an ohmic contact electrode, and then the unexposed photoresist and the metal evaporated on it are removed with acetone.

Subsequently, take a small amount of pre-synthesized Al nanowires and ultrasonically disperse them in absolute ethanol to form a suspension, and use a rubber dropper to draw a drop on the silicon wafer with the metal electrode prepared, so that the dispersion density is about 2-10 /mm ² , add an alternating current with a frequency of 1kHz and a voltage of 30V _rms at both ends of the other pair of suspended electrodes, so that the Al nanowires will move to the two opposite electrodes under the action of the electric field, connect the electrodes and be perpendicular to the ZnS nanowires Intersect to form a metal/semiconductor nanowire cross-structure heterojunction with Schottky contacts, the structure of which is shown in Figure 2.

Example 2:

Ultrasonic dispersion of a small amount of pre-synthesized n-type CdS nanowires in isopropanol in isopropanol, suck a drop with a rubber dropper, and drop it in a specific direction on a slightly inclined clean silicon wafer with a 100nm HfO ₂ insulating layer , realize the horizontal dispersion of CdS nanowires, and make the dispersion density about 2-10 wires/mm ² . After the solvent is evaporated, the positive photoresist is uniformly spin-coated, exposed to ultraviolet light and developed, and two pairs of electrode patterns are photoetched, and one pair of electrode patterns is connected through a semiconductor nanowire. Afterwards, a double-layer metal electrode of 80nm In/20nm Au is evaporated by electron beam evaporation technology as an ohmic contact electrode, and then the unexposed photoresist and the metal evaporated on it are removed with acetone.

Subsequently, ultrasonically disperse the pre-synthesized Au nanowires in anhydrous ethanol to form a suspension, and drop them on the silicon wafers on which the metal electrodes have been prepared, with a dispersion density of about 2-10 wires/mm ² . Apply an alternating current with a frequency of 1kHz and a voltage of 30V _rms to the two ends of another pair of suspended electrodes, so that the Au nanowires move to the two opposite electrodes under the action of an electric field, connect the electrodes and intersect with the CdS nanowires to form a Schottky electrode. Metal/semiconductor nanowire cross-structure heterojunction with base contacts.

Claims (4)

1. The preparation method of metal/semiconductor nanowire cross-structure heterojunction is characterized in that: the semiconductor nanowire (3) is horizontally dispersed on a silicon wafer (1) covered with an insulating layer (2), and is processed by ultraviolet lithography once. The method prepares two pairs of metal film electrodes on the insulating layer (2), wherein a pair of metal film electrodes (4) are communicated through the semiconductor nanowires (3), and the metal film electrodes (4) are connected with the semiconductor nanowires (3) ) is in ohmic contact; the suspension liquid dispersed with metal nanowires (5) is dropped on the insulating layer (2), and an alternating electric field is applied to another pair of metal thin film electrodes (6), so that the metal nanowires (5) are adsorbed to the metal On the thin film electrode (6), the metal nanowire (5) intersects with the semiconductor nanowire (3) to form a Schottky contact, forming a metal/semiconductor nanowire cross-structure heterojunction; When the semiconductor nanowire (3) is an n-type semiconductor, the two pairs of metal thin film electrodes include one or more of In, Ti, Ag, Al, and the work function of the two pairs of metal thin film electrodes is low Based on the work function of the semiconductor nanowire (3); the metal nanowire (5) includes one or more of Pt, Au, Ni, Cu, and the work function of the metal nanowire (4) is greater than The affinity between the semiconductor nanowire (3) and electrons; When the semiconductor nanowire (3) is a p-type semiconductor, the two pairs of metal thin film electrodes include one or more of Pt, Au, Ni, Cu, and the work function of the two pairs of metal thin film electrodes is greater than The work function of the semiconductor nanowire (3); the metal nanowire (5) includes one or more of In, Ti, Ag, Al, and the work function of the metal nanowire (5) is lower than The affinity of the semiconductor nanowire (3) for electrons. 2. The preparation method according to claim 1, characterized in that: the semiconductor nanowires (3) and the metal nanowires (5) are single crystal structures with a length of not less than 10 μm and a diameter of less than 1 μm. 3. The preparation method according to claim 1, characterized in that: the semiconductor nanowires (3) are elemental semiconductors, II-VI compound semiconductors, I-VI compound semiconductors or III-V compound semiconductors; 4. The preparation method according to claim 3, characterized in that: the elemental semiconductor is Si or Ge; the II-VI group compound semiconductor is ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe or CdTe; The I-VI group compound semiconductor is CuO, CuS, CuSe or CuTe; the III-V group compound semiconductor is GaAs or In ₂ Sb ₃ .

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