CN106057960A - Heterojunction array based ultraviolet detector and manufacturing method thereof - Google Patents

Abstract

The invention discloses a heterojunction array-based ultraviolet detector and a preparation method thereof. The detector includes a substrate and a conductive film, and the conductive film has a Sm2O3@ZnO heterojunction array as an ultraviolet light absorbing layer and At least one N-type ohmic electrode, and at least one P-type ohmic electrode on the Sm2O3@ZnO heterojunction array; the Sm2O3@ZnO heterojunction array is a ZnO nanotube array and Sm2O3 nanometers filled in the ZnO nanotubes line composition. Since the core structure of the present invention is a heterojunction array composed of ZnO nanotube arrays and Sm2O3 nanowires running through ZnO nanotubes, the utilization rate of photogenerated carriers can be fully improved, and it has high external quantum efficiency and sensitivity, small size, etc. Many advantages.

Description

A heterojunction array-based ultraviolet detector and its manufacturing method

technical field

The invention relates to an ultraviolet light detector technology, in particular to a heterojunction array-based ultraviolet light detector for ultraviolet light detection and a preparation method thereof.

Background technique

Ultraviolet light detectors have been widely used in military and civilian fields because of their strong anti-interference ability and other advantages. Because traditional single crystal Si-based semiconductor materials have no selective absorption for ultraviolet light, expensive filters must be used, resulting in high production costs for single crystal Si-based ultraviolet detectors, which are difficult to meet the needs of the civilian market. Therefore, at present, people mainly focus on junction devices made of wide bandgap semiconductor materials, such as (Al)GaN, SiC, ZnO, diamond junction devices, etc., and the corresponding research is also mainly concentrated on single crystal devices. Due to the complex preparation process of single crystal materials and the need for expensive production equipment, the manufacturing cost of ultraviolet detectors is still high. In recent years, due to the rapid development of nanomaterials and nano-optoelectronics technology, researchers have paid more attention to nanostructured polycrystalline thin-film junction devices that are easier to prepare and do not require expensive manufacturing equipment. The research on ultraviolet light detectors with lower cost and more outstanding performance has become a new hotspot.

At present, researchers at home and abroad have designed a variety of ultraviolet photodetector devices with different junction structures based on nano-polycrystalline films, including liquid junction, Schottky junction, and PN junction ultraviolet photodetectors, and their photoelectric properties A more detailed study was carried out. However, although the research on nano-polycrystalline thin-film junction UV detectors has made some progress, it is still in its infancy in terms of the performance of the obtained devices. The optoelectronic properties of nano-polycrystalline thin-film ultraviolet light detectors have not been able to catch up with single-crystal devices and have been applied.

The fundamental reasons why the photoelectric performance of traditional polycrystalline thin film junction devices cannot be improved dramatically are as follows:

1. The heterojunction structure of traditional polycrystalline thin film junction devices is similar to that of single crystal junction devices, and the heterojunction interfaces are common planar contacts. Therefore, the area of the space charge region distributed near the contact surface is small, which is harmful to light generation. Limited separation of electron-hole pairs;

2. The excessively high grain boundary and defect density in the polycrystalline film seriously hinder the diffusion of photogenerated electrons to the conductive substrate or metal electrode, so that a large number of photogenerated electron-hole pairs are lost due to recombination before they diffuse to the electrode. Lose;

3. A large number of defects in the polycrystalline film serve as the recombination centers of photogenerated electron-hole pairs, which also seriously reduces the lifetime of photogenerated carriers.

The above-mentioned reasons inhibit the improvement of the photoelectric performance of nano-polycrystalline thin film junction devices to a large extent. If the crystal grains of the nano-polycrystalline film can be arranged in a highly orderly manner, so that it can form a dedicated channel for the transport of photogenerated carriers in the film, and at the same time, the area of the heterojunction interface can be maximized by optimizing the structure design, then it is bound to be It greatly reduces the hindrance of photo-generated carriers in the film, and greatly improves the separation efficiency of photo-generated electron-hole pairs, which is expected to significantly improve the photoelectric properties of nano-polycrystalline films, making them close to or even reach the single crystal device level.

As far as the current research results are concerned, highly ordered nanocrystalline grain structures, such as nanotube arrays, nanowire arrays, and photonic crystals, have been successfully applied to research in the fields of solar cells, gas sensors, and photocatalysis, and have achieved good results. Effect. However, it should be noted that although ordered nanostructures greatly increase the transport rate of photogenerated carriers, they have no direct effect on the separation of photogenerated electron-hole pairs.

Chinese patent ZL201010146780 discloses a nanowire heterojunction array-based ultraviolet light detector and its preparation method. In order to obtain higher separation efficiency of photogenerated electrons and hole pairs than traditional polycrystalline PN junction films, the patent uses P-type nanometer The wire is docked with the N-type nanowire to form a nanowire PN junction. Using the highly ordered structure of nanowires directly reaching the conductive substrate and the lower defect density than polycrystalline films, it provides dedicated transport channels for photo-generated electrons and holes, speeds up the charge transport rate, and reduces photo-generated electrons and holes. loss during transportation. However, since the junction cross-section of the nanowire PN junction is the same as the radial cross-sectional area of the nanowire, after a large number of nanowire PN junctions form an array, the total cross-sectional area of the PN junction is the same as that of the traditional polycrystalline film PN junction of the same volume, which is equal to The cross-sectional area parallel to the surface of the film. Therefore, this nanowire PN junction array only provides a fast transport channel for carriers, and does not expand the effective junction area of the PN junction under the condition of the same volume film. Therefore, in theory, the volume of the formed space charge region should be are the same (the range of action of the built-in electric field has not been expanded), and both are located inside the film. In this way, if the photogenerated carriers generated by light are not generated in the space charge region inside the film, it will take a certain time for the diffusion process to enter the space charge region. However, the lifetime of photogenerated carriers is limited. Once the diffusion time of photogenerated carriers is longer than its lifetime, this part of photogenerated carriers will be lost.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention designs a heterojunction array-based ultraviolet detector with low cost, high photoelectric performance and stable performance and its manufacturing method.

In order to achieve the above object, the technical scheme of the present invention is as follows: a heterojunction array-based ultraviolet detector includes a substrate and a conductive film, and the conductive film is located on the substrate; the substrate is a glass substrate, a metal substrate or a silicon substrate. The substrate, the conductive film has a Sm2O3@ZnO heterojunction array as an ultraviolet light absorbing layer and at least one N-type ohmic electrode, and the Sm2O3@ZnO heterojunction array has at least one P-type ohmic electrode; The Sm2O3@ZnO heterojunction array is composed of ZnO nanotube arrays and Sm2O3 nanowires filled in ZnO nanotubes. The ZnO nanotube array is composed of ZnO nanotubes whose growth direction is perpendicular to the conductive film. A Sm2O3 nanowire grows inside each ZnO nanotube.

The conductive thin film of the present invention is an indium tin oxide ITO conductive thin film or a fluorine-doped SnO ₂ FTO conductive thin film.

The P-type ohmic electrode and the N-type ohmic electrode described in the present invention have a dot structure, a ring structure or a curve structure.

A method for preparing a heterojunction array-based ultraviolet detector, comprising the following steps:

A. Clean the substrate;

B. Prepare a conductive film on the cleaned substrate to obtain a conductive substrate, and clean the conductive substrate;

C. Prepare a Sm2O3@ZnO heterojunction array on the conductive film, the area of the Sm2O3@ZnO heterojunction array is smaller than the area of the conductive film;

The preparation method of the Sm2O3@ZnO heterojunction array includes the following steps:

C1, with the high-purity Ti sheet as the base material, first prepare a series of ZnO nanotubes perpendicular to the plane where the Ti sheet is located, so that the prepared ZnO nanotubes are arranged in parallel to form a ZnO nanotube array;

C2. Pretreating the ZnO nanotube array to remove the Ti substrate to prepare an independent double-pass ZnO nanotube array film.

C3. Using the independent double-pass ZnO nanotube array film as a template, prepare Sm2O3 nanowires with a dense structure in the double-pass ZnO nanotubes to form a Sm2O3@ZnO heterojunction array;

D. Preparation of P-type ohmic electrodes on Sm2O3@ZnO heterojunction arrays;

E, making N-type ohmic electrodes on the conductive film.

The base thickness of the present invention is 0.5-2mm; the conductive film is a semiconductor conductive film or a metal conductive film with a thickness of 0.5-1 μm; the thickness of the Sm2O3@ZnO heterojunction array is 0.5-100 μm, and the length of the ZnO nanotube is 0.05- 100μm, the electron concentration is greater than 1×10 ¹⁸ cm ^-3 , the length of the Sm2O3 nanowire is 0.05-100μm, and the free carrier concentration is less than 1×10 ¹⁶ cm ^-3 .

The P-type ohmic electrode and the N-type ohmic electrode of the present invention are dot-shaped, ring-shaped, or curved, made of Au, Pd, Pt, Ni, or Al, with a thickness of 0.1-5 μm.

The preparation method of the ZnO nanotube array of the present invention includes anodic oxidation method, template method, hydrothermal method, deposition method and magnetron sputtering method; the method for pretreating the ZnO nanotube array includes high-voltage auxiliary anode Oxidation method, chemical corrosion method; the preparation method of the described Sm2O3 nanowire includes template in-situ chemical one-step synthesis method, template-electrophoretic deposition method, atomic vapor deposition method, sol-gel method; the P-type ohmic electrode The preparation method of the N-type ohmic electrode includes a sputtering process, a vapor deposition process, an ion plating process, and an evaporation process.

Compared with the prior art, the present invention has the following beneficial effects:

1, the present invention uses P, N type material namely Sm2O3 and ZnO material respectively as tube core and tube shell, and its advantage is: nanotube has the same highly ordered structure as nanowire, therefore, ZnO nanotube and Sm2O3 nanowire The formed coaxial cable can also provide fast transport channels for photogenerated electrons and holes respectively. Not only that, because nanowires and nanotubes have a large specific surface area much larger than that of bulk materials, after Sm2O3 nanowires and ZnO nanotubes are tightly combined to form, the cross-section of the space charge region formed at the interface between the two will theoretically be the same as that of a single nanowire The surface area is the same and distributed along the nanocable axis. After a large number of arrays with the above characteristics are formed, the space charge area will be hundreds of times or even larger than that of the traditional laminated PN junction film of the same volume, and it will run through the entire photosensitive layer. Since the space charge region is no longer only located inside the film, but runs through the entire film, when a bias voltage is applied to the heterojunction array through the P and N-type ohmic electrodes, most of the ultraviolet light generated by different positions in the film Photogenerated electrons and holes no longer need to diffuse to the space charge region first, but can be quickly separated in situ at the first time. Although a small part of the photo-generated carriers will still be generated outside the space charge region, due to the small diameter of the nanowire or nanotube (less than 100nm), it is completely within the diffusion distance of the photo-generated electrons. Therefore, they can enter the nearby space charge region and be separated by diffusion over a very short distance. In this way, the utilization rate of photogenerated carriers can be fully improved.

2. The present invention uses the ZnO nanotube array with an independent double-pass structure as the N-type material, and at the same time serves as a template for the deposition of Sm2O3 nanowires, and can realize the preparation of Sm2O3 nanowires through a template in-situ chemical one-step synthesis method. Its advantages are: firstly, the independent double-pass ZnO nanotube array is used as the raw material and template, which makes the preparation steps simpler; secondly, the independent double-pass ZnO nanotube has good internal circulation, and it can be easily A highly dense heterogeneous nanowire is prepared inside it; again, in the template in situ chemical one-step synthesis method, the characteristics of organic S source thermal decomposition are used to control the release rate of S ^2- ions, thereby indirectly controlling the SmS The growth process of nanowires, so that the nanowires have better density and more ordered structure (SmS can be oxidized to Sm2O3 in the later high temperature treatment process).

3. Since the core structure of the present invention is a heterojunction array composed of ZnO nanotube arrays and Sm2O3 nanowires running through the ZnO nanotubes, it has many advantages such as high external quantum efficiency, high sensitivity, and small size.

4. The preparation method of the present invention has the following characteristics: the preparation process of the nanotube array is simple and mature, and can be obtained by anodic oxidation technology commonly used at present. The titanium source is relatively cheap titanium platinum, and the nickel source is cheap and easy to purchase. of nickel nitrate. The manufacturing process does not require expensive manufacturing equipment. Since the band gaps of the substrates Sm2O3 and ZnO are both above 3.0eV, the prepared detector only has a high-sensitivity response output to ultraviolet light with a wavelength shorter than 380nm, which can avoid the use of expensive filters.

5. The present invention uses wide bandgap semiconductor materials (Eg>3.0eV) Sm2O3 nanowires and ZnO nanotube arrays as P and N-type materials to make heterojunctions, and arranges a large number of coaxial cable heterojunctions in parallel to make arrays , using this Sm2O3@ZnO heterojunction array as a photosensitive layer to prepare a UV photodetector

6. The Sm2O3 nanowires and ZnO nanotubes of the present invention have a more orderly linear structure than ordinary nanopolycrystalline films, and they act as fast transport channels for photogenerated electrons and holes respectively. Finally, under the dual effects of efficient separation and fast transport, the separation efficiency of photogenerated electron-hole pairs is significantly improved. Therefore, the light response speed of the detector is fast and the responsivity is high.

Description of drawings

The present invention has 4 accompanying drawings, wherein:

Figure 1 is a schematic cross-sectional view of a heterojunction array-based ultraviolet photodetector.

Fig. 2 is a schematic plan view of a heterojunction array-based ultraviolet photodetector without P-type ohmic electrodes.

Figure 3 is a schematic horizontal cross-sectional view of the Sm2O3@ZnO heterojunction array.

Fig. 4 is a schematic vertical cross-sectional view of the Sm2O3@ZnO heterojunction array.

In the figure, 1. substrate, 2. conductive film, 3. Sm2O3@ZnO heterojunction array, 4. P-type ohmic electrode, 5. N-type ohmic electrode, 301, ZnO nanotube, 302, Sm2O3 nanowire.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings. As shown in Figures 1-4, a heterojunction array-based ultraviolet detector includes a substrate 1 and a conductive film 2, and the conductive film 2 is located on the substrate 1; the substrate 1 is a glass substrate 1 and a metal substrate. 1 or a silicon substrate 1, the conductive film 2 has a Sm2O3@ZnO heterojunction array 3 as an ultraviolet light absorbing layer and at least one N-type ohmic electrode 5, and the Sm2O3@ZnO heterojunction array 3 has a At least one P-type ohmic electrode 4; the Sm2O3@ZnO heterojunction array 3 is composed of an array of ZnO nanotubes 301 and Sm2O3 nanowires 302 filled in the ZnO nanotubes 301, and the array of ZnO nanotubes 301 is formed by growing ZnO nanotubes 301 perpendicular to the conductive film 2 are arranged in parallel, and each ZnO nanotube 301 has a Sm2O3 nanowire 302 growing therein. The conductive film 2 is an indium tin oxide ITO conductive film 2 or a fluorine-doped SnO ₂ FTO conductive film 2 . The P-type ohmic electrodes 4 and N-type ohmic electrodes 5 are point structures, ring structures or curve structures.

A method for preparing a heterojunction array-based ultraviolet detector, comprising the following steps:

A, the substrate 1 is cleaned;

B. Prepare a conductive film 2 on the cleaned substrate 1 to obtain a conductive substrate 1, and clean the conductive substrate 1;

C. Prepare a Sm2O3@ZnO heterojunction array 3 on the conductive film 2, the area of the Sm2O3@ZnO heterojunction array 3 is smaller than the area of the conductive film 2;

The preparation method of the Sm2O3@ZnO heterojunction array 3 includes the following steps:

C1, with the high-purity Ti sheet as the base material, first prepare a series of ZnO nanotubes 301 perpendicular to the plane where the Ti sheet is located, so that the prepared ZnO nanotubes 301 are arranged in parallel to form a ZnO nanotube 301 array;

C2. Perform pretreatment on the ZnO nanotube 301 array, remove the Ti substrate 1, and prepare an independent double-pass ZnO nanotube 301 array thin film.

C3. Using the independent double-pass ZnO nanotube 301 array film as a template, prepare Sm2O3 nanowires 302 with a dense structure in the double-pass ZnO nanotube 301 to form a Sm2O3@ZnO heterojunction array 3;

D. Prepare a P-type ohmic electrode 4 on the Sm2O3@ZnO heterojunction array 3;

E. Fabricate an N-type ohmic electrode 5 on the conductive film 2 .

The substrate 1 described in the present invention has a thickness of 0.5-2 mm; the conductive film 2 is a semiconductor conductive film 2 or a metal conductive film 2, and the thickness is 0.5-1 μm; the thickness of the Sm2O3@ZnO heterojunction array 3 is 0.5-100 μm, wherein the ZnO nano The length of the tube 301 is 0.05-100 μm, the electron concentration is greater than 1×10 ¹⁸ cm ^-3 , the length of the Sm2O3 nanowire 302 is 0.05-100 μm, and the free carrier concentration is less than 1×10 ¹⁶ cm ^-3 .

The P-type ohmic electrode 4 and the N-type ohmic electrode 5 of the present invention are dot-shaped, ring-shaped, or curved, made of Au, Pd, Pt, Ni, or Al, with a thickness of 0.1-5 μm.

The preparation method of ZnO nanotube 301 array described in the present invention comprises anodic oxidation method, template method, hydrothermal method, deposition method and magnetron sputtering method; Described method that ZnO nanotube 301 array is pretreated comprises high pressure Auxiliary anodic oxidation method, chemical corrosion method; the preparation method of the Sm2O3 nanowire 302 includes template in-situ chemical one-step synthesis method, template-electrophoretic deposition method, atomic vapor deposition method, sol-gel method; the P The preparation methods of the N-type ohmic electrode 4 and the N-type ohmic electrode 5 include a sputtering process, a vapor deposition process, an ion plating process, and an evaporation process.

The steps of preparing an independent double-pass ZnO nanotube 301 array by the high-voltage assisted anodic oxidation method described in the present invention are as follows: a Ti sheet is used as a substrate, and a platinum sheet is used as an anode, and a voltage of 20-80V is applied for high-voltage anodic oxidation. The oxidation time lasts 20-240min. After the oxidation is finished, a pulse voltage of 70-130V is applied to the cathode to separate the oxidized ZnO nanotube 301 array from the Ti substrate 1 to obtain an independent double-pass ZnO nanotube 301 array thin film.

The steps of preparing the Sm2O3@ZnO heterojunction array 3 by the template in-situ chemical one-step synthesis method described in the present invention are as follows: the independent double-pass ZnO nanotube 301 array thin film is used as a template. The independent double-pass ZnO nanotube 301 array film is placed at the reaction channel of the double-unit reactor to ensure that the two units of the reactor are completely isolated by the independent double-pass ZnO nanotube 301 array film. Instead, inject a certain concentration of nickel nitrate and an alcohol solution containing S-organic alkoxide (thiourea or dithioacetamide, etc.) into the two units. The reactor was placed in an oil bath, and argon was introduced into the reaction solution to prevent the oxidation of ^S2- . The S-containing organic alkoxide is decomposed at a certain temperature, and S ^2- ions are slowly released. The Ni ²⁺ ions and S ^2- ions in the solution are immersed in the ZnO nanotube 301 through bidirectional diffusion, and react in situ in the tube to generate SmS crystal nuclei at high temperature, and grow into SmS nanowires, and then the ZnO nanotubes containing SmS nanowires The array of tubes 301 is calcined at a high temperature of 400-1000° C. to form Sm2O3 nanowires 302 , and finally the Sm2O3@ZnO heterojunction array 3 is produced.

The invention utilizes a bias voltage circuit to provide reverse bias voltage to the ultraviolet detector. When ultraviolet light is irradiated on the side of the detector quartz glass, photogenerated electron-hole pairs are generated in the Sm2O3@ZnO heterojunction array 3, and under the action of the built-in electric field, the photogenerated electrons and holes flow to the ZnO nanotubes 301 and The Sm2O3 nanowire 302 drifts rapidly, and is transmitted to the external circuit through the P-type ohmic electrode 4 and the N-type ohmic electrode 5 to generate a photocurrent signal, thereby achieving the purpose of ultraviolet light detection.

The above description is a preferred embodiment of the present invention, it should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also considered Be the protection scope of the present invention.

Claims (7)

1. a heterojunction array base ultraviolet detector, including substrate (1), conductive film (2), described conductive film (2) position In substrate (1)；Described substrate (1) is substrate of glass (1), metallic substrates (1) or silicon base (1), it is characterised in that: described Conductive film (2) on have Sm2O3@ZnO heterojunction array (3) as ultraviolet light absorbing layer and at least one N-type ohm electricity Pole (5), described Sm2O3@ZnO heterojunction array (3) has at least one p-type Ohmic electrode (4)；Described Sm2O3@ZnO Heterojunction array (3) is ZnO nanotube/(301) array and Sm2O3 nano wire (302) structure being filled in ZnO nanotube/(301) Becoming, described ZnO nanotube/(301) array is perpendicular to ZnO nanotube/(301) parallel of conductive film (2) by the direction of growth Row are constituted, and in each described ZnO nanotube/(301), all growth has a Sm2O3 nano wire (302).

A kind of heterojunction array base ultraviolet detector the most according to claim 1, it is characterised in that: described conductive film (2) it is tin indium oxide ITO conductive film (2) or fluorine doped SnO₂FTO conductive film (2).

A kind of heterojunction array base ultraviolet detector the most according to claim 1, it is characterised in that: described p-type ohm Electrode (4) and N-type Ohmic electrode (5) are dots structure or loop configuration or curvilinear structures.

4. the preparation method of a heterojunction array base ultraviolet detector, it is characterised in that: comprise the following steps:

A, substrate (1) is cleaned process；

Conductive film (2) is prepared, it is thus achieved that conductive substrates (1) in B, substrate (1) after the cleaning process, and to conductive substrates (1) It is cleaned processing；

C, at conductive film (2) upper preparation Sm2O3@ZnO heterojunction array (3), described Sm2O3@ZnO heterojunction array (3) Area less than the area of conductive film (2)；

The preparation method of described Sm2O3@ZnO heterojunction array (3) comprises the following steps:

C1, with high-purity Ti sheet as base material, first prepare a series of ZnO nanotube/(301) being perpendicular to Ti sheet place plane, make institute ZnO nanotube/(301) composition arranged in parallel ZnO nanotube/(301) array prepared；

C2, described ZnO nanotube/(301) array is carried out pretreatment, remove Ti substrate (1), prepare independent bilateral ZnO nanotube/ (301) array film；

C3, with described independent bilateral ZnO nanotube/(301) array film as template, in bilateral ZnO nanotube/(301) prepare The Sm2O3 nano wire (302) of compact structure, constitutes Sm2O3@ZnO heterojunction array (3)；

D, preparation p-type Ohmic electrode (4) on Sm2O3@ZnO heterojunction array (3)；

E, making N-type Ohmic electrode (5) on conductive film (2).

The preparation method of a kind of heterojunction array base ultraviolet detector the most according to claim 4, it is characterised in that: described Substrate (1) thickness be 0.5-2mm；Conductive film (2) is quasiconductor conductive film (2) or conductive metal film (2), and thickness is 0.5-1μm；Sm2O3@ZnO heterojunction array (3) thickness is 0.5-100 μm, wherein ZnO nanotube/(301) a length of 0.05- 100 μm, electron concentration is more than 1 × 10¹⁸cm^-3, Sm2O3 nano wire (302) a length of 0.05-100 μm, free carrier concentration Less than 1 × 10¹⁶cm^-3。

The preparation method of a kind of heterojunction array base ultraviolet detector the most according to claim 4, it is characterised in that: described P-type Ohmic electrode (4) and N-type Ohmic electrode (5) be dots structure or loop configuration or curvilinear structures, by Au or Pd or Pt or Ni or Al material prepares, and thickness is 0.1-5 μm.

The preparation method of a kind of heterojunction array base ultraviolet detector the most according to claim 4, it is characterised in that: described The preparation method of ZnO nanotube/(301) array include anodizing, template, hydro-thermal method, sedimentation and magnetron sputtering Method；The described method that ZnO nanotube/(301) array carries out pretreatment includes high pressure impressed current anode oxidizing process, chemical attack Method；The preparation method of described Sm2O3 nano wire (302) includes template in-situ chemical one-step synthesis, template-electrophoretic deposition Method, atom level vapour deposition process, sol-gel process；Described p-type Ohmic electrode (4) and the preparation side of N-type Ohmic electrode (5) Method includes sputtering technology, gas-phase deposition, ion plating, evaporation process.