CN213071056U - Transmission type GaAs photoelectric cathode based on optical antireflection film - Google Patents
Transmission type GaAs photoelectric cathode based on optical antireflection film Download PDFInfo
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- CN213071056U CN213071056U CN202022292033.1U CN202022292033U CN213071056U CN 213071056 U CN213071056 U CN 213071056U CN 202022292033 U CN202022292033 U CN 202022292033U CN 213071056 U CN213071056 U CN 213071056U
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Abstract
The utility model relates to a transmission-type GaAs photocathode based on optics antireflection coating relates to shimmer night vision technical field. Comprises a glass window, an optical anti-reflection film and Ga which are sequentially laminated from one end to the other end1‑xAlxAs buffer layer, GaAs emission layer, Cs: and O an active layer. The utility model discloses utilize the optics anti-reflection coating that has the wide spectrum anti-reflection effect, replace the Si that has the narrow spectrum anti-reflection effect at present3N4Thin film, the light reflection loss of the transmission type photoelectric cathode will be greatly reducedAnd less, thereby improving the absorption rate and quantum efficiency of a broad spectrum.
Description
Technical Field
The utility model relates to a shimmer night vision technical field especially relates to a transmission-type GaAs photocathode based on optics antireflection coating.
Background
The negative electron affinity GaAs transmission type photocathode has the advantages of high quantum efficiency, small dark current, wide response wave band, average electron energy and small angle distribution, and can be widely applied to the fields of low-light-level imaging detection, electron sources and the like, particularly the fields of military affairs, aerospace, environment and the like based on low-light-level image intensifiers. The working process of the traditional transmission type GaAs photoelectric cathode is as follows: first, signal light sequentially passes through a glass window and Si3N4And the antireflection film and the buffer layer reach the emitting layer, the signal light is absorbed and excited in the emitting layer to generate photoelectrons, and then the photoelectrons are transported to the surface of the cathode and emitted to vacuum with certain probability. However, the antireflection film in current transmissive GaAs photocathodes is a single layer of Si of about 100nm3N4According to the anti-reflection theory of the optical film, the single-layer film can only reflect the light in a narrow wave band and is single 100nm Si3N4The antireflection film has a good antireflection effect on 700-900nm wave bands, and the light reflection loss in other short wave bands reaches 5-30%, so that the quantum efficiency of the short wave band is limited, the further improvement of the overall spectral sensitivity is prevented, and particularly the transmission type photocathode with blue extension response is provided.
SUMMERY OF THE UTILITY MODEL
In order to overcome the defects of the prior art, the present invention provides a transmissive GaAs photocathode based on an optical antireflection film, which utilizes the optical antireflection film with a wide-spectrum antireflection effect to replace the current Si with a narrow-spectrum antireflection effect3N4Thin film, the light reflection loss of the transmission type photoelectric cathode is greatly reduced, thereby improving the absorption rate and quantum efficiency of a broad spectrum.
A transmissive GaAs photocathode based on an optical antireflection film, comprising: a glass window, an optical antireflection film and Ga sequentially laminated from one end to the other end1-xAlxAs buffer layer, GaAs emission layer, Cs: an O active layer; the Ga is1-xAlxThe value range of x in the As buffer layer (3) is more than or equal to 0.5 and less than or equal to 1.
Further, the optical antireflection film is composed of at least three layers of optical films, and the total thickness of the optical antireflection film is more than or equal to 30 nm; the material of each layer of the optical film is SiO independently2、TiO2、Si3N4、CaF2、MgF2、HfO2、ZrO2、Al2O3、AlF3、Y2O3、BeO、MgO、La2O3、La2O5、LiF、BaF2One or more of (a).
Further, the Ga is1-xAlxThe total thickness of the As buffer layer is 0.04-2 μm.
Furthermore, the thickness of the GaAs emission layer is 0.4-2 μm.
Further, the Cs: the thickness of the O active layer is 0.5-1.5 nm.
Further, the glass window is purple glass or borosilicate glass.
The utility model has the advantages that:
the utility model discloses utilize the optics anti-reflection coating that has the wide spectrum anti-reflection effect, replace the Si that has the narrow spectrum anti-reflection effect at present3N4Thin film, the light reflection loss of the transmission type photoelectric cathode is greatly reduced, thereby improving the absorption rate and quantum efficiency of a broad spectrum.
The utility model discloses owing to adopt and to have multilayer optical film, as the antireflection coating between glass window and the cathode material, overcome the shortcoming that single antireflection coating only can the anti-reflection narrower wave band, widened the wave band of anti-reflection response greatly, more do benefit to and realize the anti-reflection of super wide wave band, like the transmission-type photocathode of blue extension to the absorptivity and the quantum efficiency of negative pole have been improved greatly, make the utility model discloses a response performance is showing and is being superior to other current transmission-type GaAs photocathodes.
The utility model discloses image intensifier and photomultiplier that constitute with the microchannel plate are expected to realize and expand its potential application under special shimmer environment such as military affairs, underwater communication and detection, desert or water smoke condition, have more extensive application prospect.
The utility model discloses owing to adopt the whole set of manufacture craft of current transmission-type GaAs photocathode, consequently the technology is ripe, easily preparation.
Drawings
FIG. 1 is a schematic diagram of an embodiment of a transmissive GaAs photocathode based on an optical antireflection film.
FIG. 2 is a comparison graph of simulated absorption spectra of the transmissive GaAs photocathode based on the optical antireflection film in the example and the conventional GaAs cathode under the same conditions.
FIG. 3 is a graph comparing the simulated absorption spectra of the transmissive GaAs photocathode based on the optical antireflection film in the example with the conventional blue-extended GaAs cathode under the same conditions.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in 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.
The utility model provides a transmission-type GaAs photocathode based on optics antireflection coating, from one end to glass window 1, optics antireflection coating 2, Ga that the other end stromatolite set up in proper order1-xAlxAs buffer layer 3, GaAs emission layer 4, Cs: o active layer 5.
The optical antireflection film 2 is composed of a plurality of optical films, the number of layers is more than or equal to 3, and each layer of the optical antireflection film is SiO2、TiO2、Si3N4、CaF2、MgF2、HfO2、ZrO2、Al2O3、AlF3、Y2O3、BeO、MgO、La2O3、La2O5、LiF、BaF2Or a composite material composed of two or more materials, but each layer is not limited to the above materials and each layer has a uniform thickness. Wherein the total thickness of the optical antireflection film is less than or equal to 10 mu m; the optical thin film layer in contact with the buffer layer is preferably Si3N4A film; the optical thin film layer in contact with the buffer layer is not TiO2A film; the optical film layer in contact with the glass window is SiO2A film, and the thickness of the film is not required; the optical antireflection film at least contains Si3N4Or Al2O3And Si3N4Or Al2O3Or the total thickness of the two mixed materials is more than or equal to 30nm, so as to prevent the buffer layer and the emission layer from being polluted by impurities generated in the heating process.
SiO in contact with the glass window2A layer of a material selected from the group consisting of,the optical antireflection film is used as a bonding wetting layer between the optical antireflection film and the glass window, and the optical antireflection film and the glass window are only favorably bonded together in a hot way, so that the antireflection effect cannot be influenced by the thickness of the optical antireflection film, and the thickness of the optical antireflection film is not required. Passing the SiO under vacuum conditions at a temperature near the melting point of the glass window2And the wetting layer is used for thermally bonding the optical antireflection film and the glass window together. In addition, the material selection, the number of layers, the thickness of each layer and the like of the optical antireflection film are different according to different practical application requirements.
The GaAs emission layer has a thickness of 0.4-2 μm and a p-type doping concentration of 1018-1019cm-3The doping concentration of the emitting layer is uniform and unchanged, or the gradient from the emitting layer/buffer layer interface to the cathode surface is reduced.
The Ga is1-xAlxAn As buffer layer, wherein x is more than or equal to 0.5 and less than or equal to 1 in Al component, the thickness is 0.04-2 mu m, and the p-type doping concentration is 1018-1019cm-3And the Al component and the p-type doping concentration are independently unchanged or are reduced in gradient from the boundary of the emitting layer/the buffer layer to the surface of the cathode, and the reduction gradient and the range of the Al component or the p-type doping concentration are different according to different actual conditions.
The glass window is a signal light incidence window and is 9741 purple glass or corning 7056 silicon boron glass.
Cs: an O active layer of not more than 10-7In the ultra-high vacuum activation system under the Pa condition, a layer of 0.5-1.5nm Cs: and (3) O film.
The utility model discloses a transmission-type GaAs photocathode preparation method based on optics antireflection coating as follows:
step (1): firstly, the following structures are sequentially matched and epitaxially grown on a high-quality GaAs substrate by a Metal Organic Chemical Vapor Deposition (MOCVD) or Molecular Beam Epitaxy (MBE) growth technology: the GaAs substrate, GaAs smooth layer, GaAlAs barrier layer, GaAs emission layer, GaAlAs buffer layer, GaAs protective layer; wherein, the GaAs smooth layer has the thickness of 0.1-0.5 μm and is used as a transition layer of the GaAs substrate and other epitaxial structures so as to realize high-quality epitaxial structure growth; the GaAlAs barrier layer is 0.5-2 μm thick and is used for preventing the GaAs emission layer from being corroded by corrosive liquid in the selective chemical corrosion process; the GaAs protective layer is 0.05-0.2 μm thick and is used for protecting the buffer layer and the emitting layer after the growth is completed.
Step (2): and corroding and removing the GaAs protective layer by using a selective chemical corrosive agent to expose the GaAlAs buffer layer, and sequentially and uniformly evaporating each layer of the optical antireflection film on the GaAlAs buffer layer by using a vacuum coating machine under a vacuum condition to form the optical antireflection film which is favorable for imaging and has a good antireflection effect.
And (3): under the vacuum condition, gradually raising the temperature to 300-400 ℃, and fully heating and degassing the glass window and the semiconductor epitaxial structure; and then, gradually raising the temperature to be close to the melting point of the glass, thermally bonding the glass window and the bonding film of the optical antireflection film together, and gradually cooling to room temperature to finish the bonding process.
And (4): and after the bonding is finished, sequentially corroding and removing the GaAs substrate, the GaAs smooth layer and the GaAlAs barrier layer by using selective chemical reagents to expose the GaAs emission layer.
And (5): immigration is less than or equal to 10-7Pa, evaporating a layer of Cs with the particle size of 0.5-1.5nm on the surface of the GaAs emission layer: and O activating layer to form negative electron affinity state on the surface of the emitting layer so as to complete the cathode manufacture.
Example 1
An optical antireflection film-based transmissive GaAs photocathode, as shown in fig. 1, includes:
a glass window 1, an optical antireflection film 2 and Ga sequentially laminated from one end to the other end0.3Al0.7As buffer layer 3, GaAs emission layer 4, Cs: o active layer 5.
The optical antireflection film 2 comprises the following components in sequence from the glass window 1: 100nmSiO2/24nmSi3N4/53.7nmMgF2/39nmSi3N4/93.3nmMgF2/9.6nmSi3N4/116nm MgF2/78nmSi3N4。
The GaAs emission layer 4 has the thickness of 1.6 mu m and the p-type doping concentration of 1019cm-3。
The Ga is0.3Al0.7As buffer layer 3 with thickness of 0.4 μm and p-type doping concentration of 5x1018cm-3。
The glass window 1 is a signal light incidence window and is 9741 purple glass with two polished surfaces.
Cs: o an active layer 5 of 10 or less-7And depositing a layer of Cs with the particle size of 0.5-1.5nm on the surface of the emission layer 4 under the Pa vacuum condition: and (3) O film.
The manufacturing method of the transmission type GaAs photocathode comprises the following steps:
step (1): the following structures are epitaxially grown on a high-quality GaAs substrate by using a Metal Organic Chemical Vapor Deposition (MOCVD) or Molecular Beam Epitaxy (MBE) technique: GaAs substrate/0.5 mu m GaAs smooth layer/2 mu m Ga0.5Al0.5As barrier layer/1.6 mu m GaAs emission layer/0.4 mu mGa0.3Al0.7As buffer layer/0.1 mu mGaAs protective layer;
step (2): the GaAs protection layer is removed by wet etching to expose the buffer layer 3. And (3) sequentially and uniformly evaporating the optical antireflection film 2 on the buffer layer 3 by using a vacuum coating machine.
And (3): the glass window 1 and the Ga of the semiconductor epitaxial structure are put under vacuum0.3Al0.7Aligning the As buffer layer, gradually heating to 300-400 ℃, and fully heating for degassing; then gradually raising the temperature, keeping the temperature near the melting point of the glass window, and thermally bonding the glass window 1 and the optical antireflection film 2 together under the action of pressure; and finally, gradually cooling to room temperature to finish the bonding process.
And (4): and after bonding, removing the GaAs substrate, the GaAs smooth layer and the GaAlAs barrier layer in sequence by using a selective chemical etchant to expose the GaAs emission layer 4.
And (5): at most 10-7Pa ultra-high vacuum activation system, depositing a layer of 0.5-1.5nm Cs: and O, activating the layer 5 to finish the manufacturing process of the cathode.
The comparison graph of the simulated absorption spectrum of the transmissive GaAs photocathode provided in this example with that of a conventional cathode under the same conditions is shown in fig. 2. Fig. 2 shows that the response band of the photocathode provided in this embodiment is 450-900nm, which has a higher absorption rate than the conventional cathode in the short wavelength band, and the absorption rate in the 450-520nm band is higher than that of the conventional cathode by more than 5-10%, so that the photocathode using the optical antireflection film has a higher response performance.
Example 2
An optical antireflection film-based transmissive GaAs photocathode, as shown in fig. 1, includes:
the glass window 1, the optical antireflection film 2, the AlAs buffer layer 3, the GaAs emission layer 4 and the Cs are sequentially stacked from one end to the other end: o active layer 5.
The optical antireflection film 2 comprises, from the glass window 1 in sequence: 100nmSiO2/20.3nmSi3N4/43nmMgF2/33.7nmSi3N4/46.5nmMgF2/21nmSi3N4/123.5nmMgF2/13nmSi3N4/47.2nmMgF2/69.5nmSi3N4。
The GaAs emission layer 4 has a thickness of 1.6 μm, and is otherwise the same as that of example 1.
The AlAs buffer layer 3 is 0.1 μm thick and has a p-type doping concentration of 5x1018cm-3。
The glass window 1 is a signal light incidence window and is 9741 purple glass with two polished surfaces.
The Cs: the O active layer 5 is the same as in example 1.
The preparation method of the blue extension transmission type GaAs photoelectric cathode comprises the following steps:
step (1): the same as embodiment 1, wherein the following structure is epitaxially grown on a high-quality GaAs substrate: GaAs substrate/0.5 mu m GaAs smooth layer/2 mu m Ga0.5Al0.5As barrier layer/1.6 mu m GaAs emission layer/0.1 mu m mAlAs buffer layer/0.1 mu m GaAs protective layer;
step (2): in the same manner as in example 1, in the optical antireflection film 2, from the buffer layer, in order: 100nmSiO2/20.3nmSi3N4/43nmMgF2/33.7nmSi3N4/46.5nmMgF2/21nmSi3N4/123.5nmMgF2/13nmSi3N4/47.2nmMgF2/69.5nmSi3N4；
And (3): the same as example 1;
and (4): the same as example 1;
and (5): the same as in example 1.
The simulated absorption spectrum of the blue extended transmission type GaAs photocathode provided in this example is compared with that of a conventional cathode under the same conditions, and is shown in fig. 3. Fig. 3 shows that the response band 350-900nm of the blue extension transmissive cathode provided in this embodiment has a higher absorption rate than the conventional cathode in the short wave band, and the absorption rate of the cathode in the 400-430nm band is 5-20% higher, and the absorption rate of the cathode in the 470-580nm band is 3-5% higher, so that the blue extension cathode provided in this embodiment using the optical anti-reflection film has a better anti-reflection effect in the ultra-wide band, thereby achieving a higher quantum efficiency, and especially having a wider application prospect in the band response band.
The above embodiments are merely examples of the present invention, and do not limit the protection scope of the present invention, and all designs the same as or similar to the present invention belong to the protection scope of the present invention.
Claims (6)
1. A transmission type GaAs photocathode based on an optical antireflection film is characterized by comprising:
a glass window (1), an optical antireflection film (2) and Ga which are sequentially laminated from one end to the other end1-xAlxAs buffer layer (3), GaAs emission layer (4), Cs: an O active layer (5);
the Ga is1-xAlxThe value range of x in the As buffer layer (3) is more than or equal to 0.5 and less than or equal to 1.
2. The transmissive GaAs photocathode based on an optical antireflection film according to claim 1, wherein the optical antireflection film (2) is composed of at least three optical thin films, and the total thickness of the optical antireflection film (2) is not less than 30 nm.
3. The optical antireflection film-based transmissive GaAs photocathode of claim 1, wherein the Ga is1-xAlxThe total thickness of the As buffer layer (3) is 0.04-2 μm.
4. The optical antireflection film-based transmissive GaAs photocathode according to claim 1, wherein the thickness of the GaAs emission layer (4) is 0.4 to 2 μm.
5. The optical antireflection film-based transmissive GaAs photocathode of claim 1, wherein the Cs: the thickness of the O activation layer (5) is 0.5-1.5 nm.
6. Optical antireflection film based transmissive GaAs photocathode according to claim 1, characterized in that said glass window (1) is a clear glass or a borosilicate glass.
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