CN112382558B - Preparation method of controllable quantum structure based on micro-nano metal/semiconductor Schottky junction - Google Patents

Abstract

The invention belongs to the technical field of semiconductor quantum structures, in particular to a method for preparing a controllable quantum structure based on micro-nano metal/semiconductor Schottky junctions. The method of the present invention is to prepare a metal micro-nano structure on the semiconductor surface containing a quantum well to form a metal/semiconductor Schottky junction in a micro-nano scale. There is a local electrostatic field near the micro-nano Schottky junction, which can be used in the quantum A lateral confinement is generated to carriers in the well layer, thereby obtaining a new controllable quantum structure in the semiconductor quantum well; the quantum structure includes quantum dots, quantum wires, quantum rings and their hybrid structures and arrays; the method of the present invention is simple It is easy to operate, and under the premise of not damaging the quality of semiconductor crystals and introducing additional impurities, a controllable semiconductor quantum structure can be prepared, and it can even be used to prepare complex and high-quality semiconductor quantum structure systems, which provides a new way for the preparation of new semiconductor quantum devices. way.

Description

Preparation method of controllable quantum structure based on micro-nano metal/semiconductor Schottky junction

technical field

The invention belongs to the technical field of semiconductor quantum structures, and in particular relates to a method for forming a controllable quantum structure inside a semiconductor.

Background technique

Semiconductor quantum structures have broad application prospects in new microelectronics and optoelectronic devices, such as light-emitting diodes, photodetectors, single-photon source devices, and semiconductor lasers; in particular, controllable quantum structures are of great interest for researching new optoelectronic devices. favor. However, it is difficult to control the size, shape and distribution of semiconductor quantum structures prepared by common methods at present, such as quantum dots or quantum wires grown by self-organization methods; point.

The common controllable semiconductor quantum structure is a quantum structure prepared by a patterned substrate, but due to the complicated preparation steps, the process cost is high, and more defects are easily introduced due to etching, resulting in poor photoelectric properties and other problems. On the premise of not damaging the crystal quality inside the semiconductor and not introducing impurities and defects, by preparing controllable metal micro-nanostructures on the semiconductor surface, the corresponding micro-nano regions are generated due to the Schottky contact between the metal micro-nanostructures and the semiconductor. Depletion layer, the interface at different depths can form a lateral potential well confinement that is basically the same shape as the metal micro-nano structure (such as nano-disk, nano-wire, nano-ring, etc.), so that it can induce the formation of corresponding quantum structures at different interfaces inside the semiconductor . This method provides a new way to prepare controllable, diverse and diversified semiconductor quantum structures.

Contents of the invention

In order to solve the controllable and diverse requirements of quantum structures and the problems of difficult device fabrication and integration, the present invention proposes a new method of using metal/semiconductor micro-nano contacts to induce the formation of controllable and diverse quantum structures, called micro-based Preparation method of controllable quantum structure of nanometer metal/semiconductor Schottky junction.

The method for preparing a controllable quantum structure based on a micro-nano metal/semiconductor Schottky junction proposed by the present invention is to prepare a metal micro-nano structure on a semiconductor surface containing a quantum well to form a micro-nano scale metal/semiconductor Schottky junction, There is a local electrostatic field near the micro-nano Schottky junction, which can generate a lateral confinement to carriers in the quantum well layer, thereby obtaining a new controllable quantum structure in the semiconductor quantum well; the quantum structure includes quantum Dots, quantum wires, quantum rings and their hybrid structures and arrays; the specific steps are as follows:

(1) A semiconductor quantum well layer with a capping layer is grown on a single crystal semiconductor substrate; the growth method can be molecular beam epitaxy or other methods;

(2) Then, by electron beam etching or photolithography, controllable metal micro-nanostructures are prepared on the semiconductor surface buried with semiconductor quantum wells; in this way, the size, shape and distribution of metal micro-nanostructures in the quantum wells and on the surface can be obtained Almost identical semiconductor quantum structures.

In the step (1) of the present invention, the thickness of the semiconductor quantum well is 1-30 nm, and the distance between the quantum well layer and the semiconductor surface (ie the thickness of the semiconductor cap layer) is 5-100 nm.

；In step (2) of the present invention, the scale of a single metal nanostructure is 10-500 nm; the selected metal needs to meet the following conditions:

;

为半导体的亲和势，E _c 为半导体的导带底能量，E _f 为半导体的费米能。金属微纳米结构可以是任何形状，例如纳米盘、纳米线、纳米环及其混合结构或阵列。where W is the metal work function,

is the _affinity of the semiconductor, Ec is the conduction band bottom energy of the semiconductor, and _Ef is the Fermi energy of the semiconductor . Metallic micro-nanostructures can be in any shape, such as nanodisks, nanowires, nanorings, and hybrid structures or arrays thereof.

The method of the present invention will be further described by taking gold on a silicon surface as an example below.

According to the characteristics of the metal/semiconductor Schottky contact to regulate the energy band inside the semiconductor, the present invention first calculates the distribution diagram of the potential energy change produced by the energy band regulation of different gold nanostructures (gold nanodisks and gold nanowires) in silicon semiconductors (Figure 2), which clearly shows the lateral potential energy distribution of the semiconductor nanoscale region at different depths under the gold nanostructure, so that in the semiconductor quantum wells within a certain depth range under the micro-nano metal/semiconductor Schottky junction The lateral potential well confinement is formed, and the shape, size and distribution of the lateral potential well are almost the same as those of the metal micro-nano structure on the surface; while the vertical (perpendicular to the surface) potential well confinement is determined by the energy band deviation between the quantum well and the surrounding semiconductor. produce. Therefore, by combining these two kinds of potential well confinement, a new type of quantum structure can be obtained in the semiconductor quantum well. For example, metal nanodisks on the surface (providing two-dimensional lateral confinement) induce quantum dots in quantum wells (providing one-dimensional longitudinal confinement), while metal nanowires on the surface (providing one-dimensional lateral confinement) induce quantum dots in quantum wells ( Provides one-dimensional longitudinal confinement) induced quantum wires. In conclusion, metal micro-nanostructures on semiconductor surfaces can induce controllable new semiconductor quantum structures in semiconductor quantum wells.

The present invention uses gold/silicon semiconductor Schottky contacts to induce the formation of a controllable quantum structure in the semiconductor, and the specific steps are as follows:

First, on a Si(001) single crystal substrate, a germanium-silicon (GeSi) alloy layer is grown as a quantum well layer of holes by molecular beam epitaxy or other growth methods, and then electron beam exposure technology or photolithography is used to Technology to obtain templates of micro-nano structures on the surface;

Then, a layer of metal film is coated by electron beam evaporation (or thermal evaporation, magnetron sputtering, etc.), and the metal micro-nano structure is obtained after peeling off the micro-nano structure template; through the metal micro-nano structure on the surface, the A specific semiconductor quantum structure is induced in the quantum well layer; specific semiconductor quantum structures (such as quantum dots, quantum wires and quantum rings, and their combinations or arrays) can be realized in the quantum well layer by adjusting the shape of the metal micro-nano structure .

In the present invention, the silicon single crystal substrate is cleaned by the standard RCA method, the germanium silicon (GeSi) alloy thin film can be grown by molecular beam epitaxy equipment or other growth equipment, and the gold nanostructure on the surface is obtained by electron beam exposure and electron beam evaporation Technical realization. The specific operation process is as follows:

(1) Take a Si(001) single wafer as the substrate, and perform chemical cleaning on it;

(2) On the cleaned Si(001) single wafer substrate, grow a germanium-silicon (GeSi) alloy thin film and a silicon covering layer by molecular beam epitaxy equipment or other growth equipment. The composition of germanium in the alloy layer is: 5%-50%, the thickness of the alloy layer: 1-30nm, the thickness of the silicon covering layer: 5-100 nm;

(3) On the sample grown with a germanium-silicon (GeSi) alloy film and a silicon covering layer, a layer of SiO ₂ film is evaporated first, with a thickness of 30-100nm; then a PMMA mask with a certain structure array is formed by electron beam exposure. Template; then remove the SiO ₂ under the hole by soaking in BOE solution (20g NH ₄ F: 10mlHF: 200mlH ₂ O) for 20s, then evaporate a gold film by electron beam evaporation with a thickness of 10-30nm, and then peel off the PMMA glue A gold nanostructure is obtained: wherein, the certain structure array includes a circular hole array (such as a honeycomb array), a line array, an annular array or a combined array thereof, and the obtained nanostructure is a nanodisk (such as a diameter of 30- 100nm), nanowires (if the size is ) or nanorings, or their combined nanostructures.

The present invention can produce micro-nano structures with different shapes, different structures, and different periodic arrangements according to requirements; it can also adjust the effective value of different internal interface potential energy changes according to their different work functions by evaporating different metals; Regulating the thickness of the covering layer changes the potential energy distribution in the quantum well layer.

The innovation of the present invention lies in that: under the premise of not damaging the semiconductor crystal quality and not introducing additional impurities, various semiconductor quantum structures (such as Quantum dots, quantum wires, quantum rings and their composite structures and arrays), the potential well depth of the semiconductor quantum structure can be adjusted by selecting different metals (with different work functions) or the thickness of the covering layer above the quantum well layer. The size, shape and arrangement of micro-nanostructures regulate the morphology and distribution of semiconductor quantum structures.

Description of drawings

Figure 1 is a schematic diagram of different metal micro-nanostructures. Among them, (a) nanodisk, (b) nanowire, (c) nanoring.

Fig. 2 shows the electric potential energy change inside silicon due to the nanoscale metal/semiconductor Schottky contact, gold nanodisk and nanowire structure.

3 is a SEM image of a honeycomb periodic array of gold nanodisks prepared on a silicon surface containing a germanium silicon (GeSi) quantum well layer. The gold nanodisks have a diameter of 60nm and a period of 120nm.

FIG. 4 is an SEM image of a gold nanowire array prepared on a silicon surface containing a germanium silicon (GeSi) quantum well layer, and the gold nanowire is .

5 is a SEM image of a honeycomb periodic array of nickel nanodisks prepared on a silicon surface containing a germanium silicon (GeSi) quantum well layer. The gold nanodisks have a diameter of 45nm and a period of 100nm.

detailed description

The molecular beam epitaxy equipment is a Riber EVA-32 ultra-high vacuum molecular beam epitaxy system; the system consists of a sample chamber (pre-chamber) and a growth chamber (main chamber). Metal micro-nano structure samples were completed by electron beam exposure technology (model: RaithElphy Plus) and electron beam evaporation equipment (model: DE400). The morphology of the samples was characterized by a scanning electron microscope (model: Zeiss Sigma).

Example 1

This example is to prepare a gold nanodisk to induce a controllable quantum structure in a silicon semiconductor, which is divided into three steps: step 1: RCA cleaning; step 2: growth of a germanium silicon (GeSi) quantum well layer with a silicon capping layer; step 3 : Fabrication of gold nanodisk structures. The details are described below.

Step 1: RCA Cleaning

The Si(001) substrate needs to be cleaned before being put into the molecular beam epitaxy equipment for growth. The cleaning procedure is as follows:

(1) Sonicate the Si(100) single wafer in acetone and methanol successively for 5 minutes to remove organic matter on the substrate surface. Sonicate again for 5 minutes in deionized water.

(2) Soak in a mixed solution of sulfuric acid and hydrogen peroxide (volume ratio 4:1) for 10 minutes, then rinse with deionized water for 10 minutes.

(3) After bathing in a water bath at 80°C for 15 minutes in a mixed solution of ammonia, hydrogen peroxide, and water (volume ratio 1:1:5), rinse with deionized water for 15 minutes.

(4) After bathing in a mixed solution of hydrochloric acid, hydrogen peroxide, and water (volume ratio 1:1:5) at 80°C for 15 minutes, rinse with deionized water for 15 minutes.

(5) Soak in 5 wt% hydrofluoric acid for 60-80 seconds to remove the oxide layer on the surface. Then rinse with deionized water.

Step 2: Growth of germanium silicon (GeSi) quantum well layer with silicon capping layer

Take a Si(001) silicon single wafer, after cleaning according to the cleaning procedure described in step 1, put it into molecular beam epitaxy equipment to carry out molecular beam epitaxy growth of germanium and silicon materials. Both silicon and germanium sources of the system are evaporated by electron beam heating. The following are the basic process conditions for material growth.

i) Heat the substrate to 860°C (higher temperature is possible) and keep it for 6 minutes to desorb the impurity molecules adsorbed on the surface.

ii) Epitaxial growth of silicon buffer layer, growth temperature: 500°C, growth rate: 0.6 Å/s, growth thickness: 100nm.

iii) Epitaxial growth of germanium silicon (GeSi) quantum well layer, growth temperature: 420° C., germanium composition in germanium silicon (GeSi) alloy is 38%, and its thickness is 5 nm. The thickness and composition can be tuned by the growth rate and time of Ge and Si.

iv) Continue to epitaxially grow the silicon capping layer, growth temperature: 420-500°C, growth rate: 0.6 Å/s, growth thickness: 30nm. The thickness of the silicon capping layer can be controlled by the growth time. Lower the temperature to room temperature immediately after growth is complete.

Step 3: Preparation of gold nanodisk structure

According to different needs, gold nanostructures with different shapes and distributions, such as nanodisks or nanowires, can be prepared. The following is the fabrication of gold nanodisks:

Fabrication of gold nanodisk arrays by electron beam exposure: evaporating a 30nm silicon dioxide layer on the surface of the sample, and then etching it into a circular hole array (such as a honeycomb arrangement) by spin-coating electron beam glue PMMA for electron beam etching technology mask board. Place the sample in BOE solution (20gNH ₄ F: 10mlHF: 200mlH ₂ O) and soak for 20s to remove the silicon dioxide under the hole of the mask, then evaporate a 10nm gold film by electron beam, and then peel off the PMMA mask to form a honeycomb nanometer The standard gold discs are arranged periodically, and the diameter and spacing of the gold discs are precisely adjustable.

By performing scanning electron microscope morphology characterization on the sample in Step 3 of Example 1 (as shown in Figure 3), it was obtained that the honeycomb array lattice period of gold nanodisks in the sample was 120 nm, and the diameter was about 60 nm. Due to the metal nanostructure/silicon Schottky contact, a honeycomb-like periodic arrangement of lateral local potential well distribution can be formed in the quantum well layer, so the present invention can provide a new idea for preparing a graphene-like structure.

Example 2

This example is to prepare a controllable quantum structure in a silicon semiconductor induced by gold nanowires. Wherein, step 1: RCA cleaning; step 2: growth of a germanium silicon (GeSi) quantum well layer with a silicon capping layer. The first two steps are the same as Steps 1 and 2 of Example 1 and will not be described again. Step 3: Preparation of gold nanowire structure will be introduced below.

Step 3: Gold nanowire structure preparation

Fabrication of gold nanowire arrays by electron beam exposure: a 30nm silicon dioxide layer was evaporated on the sample surface, and then etched into a mask plate with nanowire arrays by spin-coating electron beam glue PMMA for electron beam etching technology. Place the sample in BOE solution (20gNH ₄ F: 10mlHF: 200mlH ₂ O) and soak for 20s to remove the silicon dioxide under the mask template nanowires, then evaporate a 10nm gold film by thermal evaporation, and then peel off the PMMA mask template to form nanowire cycles arrangement. The size and period of gold nanowires are precisely tunable.

By performing scanning electron microscope morphology characterization on the sample in Step 3 of Example 2 (as shown in FIG. 4 ), the period of the gold nanowires in the sample is obtained, and the size of a single gold nanowire is . Due to the metal nanostructure/silicon Schottky contact, a periodic semiconductor quantum wire structure can be realized in the semiconductor quantum well layer.

Example 3

This example is to prepare a nickel nanodisk to induce a controllable quantum structure in a silicon semiconductor. Wherein, step 1: RCA cleaning; step 2: growth of a germanium silicon (GeSi) quantum well layer with a silicon capping layer. The first two steps are the same as Steps 1 and 2 of Example 1 and will not be described again. Step 3: Preparation of nickel nanodisk structure is introduced below.

Step 3: Preparation of nickel nanodisk structure

Fabrication of gold nanodisk arrays by electron beam exposure: evaporating a 30nm silicon dioxide layer on the surface of the sample, and then etching it into a circular hole array (such as a honeycomb arrangement) by spin-coating electron beam glue PMMA for electron beam etching technology mask board. Place the sample in the BOE solution (20gNH ₄ F: 10mlHF: 200mlH ₂ O) and soak for 20s to remove the silicon dioxide under the hole of the mask, and then evaporate a 15nm nickel film by thermal evaporation, and then peel off the PMMA mask to form a honeycomb The nanoscale nickel disks are arranged periodically, and the diameter and interval of the nickel disks are precisely adjustable.

By performing scanning electron microscope morphology characterization on the sample in Step 3 of Example 3 (as shown in FIG. 5 ), it was obtained that the honeycomb array lattice period of nickel nanodisks in the sample was 100 nm, and the diameter was about 45 nm. Due to the metal nanostructure/silicon Schottky contact, a honeycomb-like periodic arrangement of lateral local potential well distribution can be formed in the quantum well layer, so a graphene-like structure with magnetic properties can be realized.

In the present invention, it is listed that different metal micro-nanostructures can form corresponding quantum structures through energy band regulation inside the semiconductor (as shown in Figure 1); it is analyzed that gold nanodisks and nanowires form larger quantum structures in the quantum well layer near the surface. energy band bending (as shown in Figure 2), so as to form quantum dots and quantum wire structures in the quantum well layer; grow germanium silicon (GeSi) alloy quantum wells by molecular beam epitaxy (such as step 1 in each embodiment , 2); using electron beam exposure technology to prepare nanodisks and periodic arrays of nanowires of different metals (such as step 3 in the three examples); and use scanning electron microscopy (SEM) for morphology characterization (as shown in Figure 3, Figure 4 and Figure 5). Due to the nanoscale Schottky contact, the metal micro-nanostructure on the semiconductor surface can induce the formation of a new type of semiconductor quantum structure in the quantum well layer inside the semiconductor, and the lateral shape and distribution of the semiconductor quantum structure are similar to those of the metal micro-nanostructure on the surface. The structures are almost identical; in particular, the semiconductor quantum structure prepared by the present invention does not involve any etching process, thereby completely avoiding defects and impurities caused by etching in controllable semiconductor quantum structures generally obtained by etching methods. Therefore, the invention provides a brand-new idea for designing and preparing a new controllable high-quality semiconductor quantum structure, and can also be used in the field of design and preparation of new quantum devices.

Claims (4)

1. A method for preparing a controllable quantum structure based on a micro-nano metal/semiconductor Schottky junction, which is to prepare a metal micro-nano structure on a semiconductor surface containing a quantum well to form a micro-nano scale metal/semiconductor Schottky junction, There is a local electrostatic field near the micro-nano Schottky junction, which creates a lateral confinement of carriers in the quantum well layer, and the shape, size and distribution of the lateral potential well are almost the same as those of the metal micro-nano structure on the surface; The vertical potential well confinement is produced by the energy band deviation between the quantum well and the surrounding semiconductor; combining these two potential well confinements, a new controllable quantum structure is obtained in the semiconductor quantum well; the quantum structure includes quantum dots, quantum Lines, quantum rings and their hybrid structures and arrays; the specific steps are as follows: (1) growing a semiconductor quantum well layer with a capping layer on a single crystal semiconductor substrate; (2) Then, by electron beam etching or photolithography, controllable metal micro-nanostructures are prepared on the semiconductor surface buried with semiconductor quantum wells, so that the size, shape and distribution of the surface metal micro-nanostructures in the quantum wells are almost the same semiconductor quantum structures. 2. preparation method according to claim 1, is characterized in that, the thickness of semiconductor quantum well described in step (1) is 1-30nm, and the distance of quantum well layer from semiconductor surface is the thickness of semiconductor cap layer is 5-30nm. 100nm. 3. preparation method according to claim 1, is characterized in that, in step (2), the scale of single metal nanostructure is 10-500nm; Used metal meets following condition:|(W-x)-( _Ec -E _f )|>0.005eV; Wherein, W is the work function of the metal, χ is the affinity of the semiconductor, _Ec is the conduction band bottom energy of the semiconductor, and _Ef is the Fermi energy of the semiconductor; the metal micro-nanostructure is any shape, including nanodisks, nanowires, Nanorings and hybrid structures or arrays thereof. 4. preparation method according to claim 1, is characterized in that, described metal is gold, and described semiconductor quantum well layer is germanium-silicon alloy layer, and the specific operation process of preparation is as follows: (1) get Si(001) single wafer as substrate, and carry out chemical cleaning to it; (2) On the cleaned Si(001) single wafer substrate, grow germanium-silicon alloy film and silicon covering layer through molecular beam epitaxy equipment or other growth equipment; the quality of germanium component in the alloy layer is 5%-50% , the thickness of the alloy layer is 1-30nm, and the thickness of the silicon covering layer is 5-100nm; (3) on the sample that has germanium-silicon alloy thin film and silicon capping layer, evaporate one deck SiO earlier thin film, its thickness is _30-100nm ; Then form the PMMA glue mask plate of certain structure array by electron beam exposure; Then Remove the SiO ₂ under the holes by immersing in BOE solution for 20s, and then vapor-deposit a gold film with a thickness of 10-30nm by electron beam evaporation, and then peel off the PMMA glue to obtain a gold nanostructure: wherein, the certain structure array includes a circle Hole arrays, line arrays, ring arrays or combinations thereof, the obtained nanostructures are nanodisks, nanowires or nanorings, or combination nanostructures.

Images