阅读说明：本技术 一种具有超晶格结构电子发射层的AlGaN/GaN光电阴极 (AlGaN/GaN photocathode with superlattice structure electron emission layer ) 是由 王晓晖 班启沛 张世博 张翔 王振营 于 2021-06-23 设计创作，主要内容包括：本发明公开了一种具有超晶格结构电子发射层的AlGaN/GaN光电阴极。该超晶格AlGaN/GaN光电阴极的结构包括：由下至上依次设置的衬底(11)、缓冲层(12)、p型超晶格AlGaN/GaN电子发射层(13)、激活层(14)。本发明在传统GaN光电阴极结构基础上,采用p型超晶格AlGaN/GaN结构作为光电阴极的电子发射层,能够促进光电子在发射层中的扩散和在表面的逸出,从而有效解决光电阴极中光电转化率不高的问题,有助于进一步提高AlGaN/GaN光电阴极的量子效率。(The invention discloses an AlGaN/GaN photocathode with an electron emission layer with a superlattice structure. The structure of the superlattice AlGaN/GaN photocathode comprises: the substrate (11), the buffer layer (12), the p-type superlattice AlGaN/GaN electron emission layer (13) and the activation layer (14) are sequentially arranged from bottom to top. On the basis of the traditional GaN photocathode structure, the p-type superlattice AlGaN/GaN structure is adopted as the electron emission layer of the photocathode, so that the diffusion of photoelectrons in the emission layer and the escape of the photoelectrons on the surface can be promoted, the problem of low photoelectric conversion rate in the photocathode is effectively solved, and the quantum efficiency of the AlGaN/GaN photocathode is further improved.)

1. An AlGaN/GaN photocathode having an electron emission layer of superlattice structure, characterized in that: the substrate (11), the buffer layer (12), the p-type superlattice AlGaN/GaN electron emission layer (13) and the activation layer (14) are sequentially arranged from bottom to top.

2. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: in the p-type superlattice AlGaN/GaN electron emission layer (13), the thickness of an AlGaN layer (21) in a single period is 5-10 nm, and the thickness of a GaN layer (22) is 5-10 nm.

3. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: in the AlGaN/GaN electron emission layer (13) with the p-type superlattice structure, the number of the repeating cycles of the superlattice is 4-30.

4. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: in the AlGaN/GaN electron emission layer (13) with the p-type superlattice structure, the thickness of the electron emission layer of the p-type superlattice AlGaN/GaN layer is 80-300 nm.

5. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: the AlGaN/GaN electron emission layer (13) of the p-type superlattice structure is doped with Mg, and the Hall concentration of holes of the doped material is 10¹⁶～10¹⁸cm^-3。

6. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: the substrate (11) can be made of sapphire, silicon, gallium nitride, aluminum nitride, silicon carbide and the like, and the thickness of the substrate is 400-600 mu m.

7. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: the buffer layer (12) can be made of Al_1-xGa_xN, GaN, AlN, etc.

8. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: the thickness of the buffer layer (12) is 10-100 nm.

9. The AlGaN/GaN photocathode structure having an electron emission layer with a superlattice structure according to claim 1, wherein: the active layer (14) comprises a single Cs active layer or a Cs/O active layer, the thickness of the active layer is 1-5 atomic layers, and the active layer is tightly adsorbed on the surface of the p-type AlGaN/GaN superlattice electron emission layer through an ultrahigh vacuum activation process.

Technical Field

The invention relates to the field of photoelectron materials and devices, in particular to an AlGaN/GaN photocathode structure with an electron emission layer of a superlattice structure.

Background

The GaN photocathode has the advantages of high quantum efficiency, small dark emission, concentrated energy distribution of emitted electrons, small fluctuation of quantum efficiency relative to wavelength, wide direct band gap and the like. The photocathode device based on GaN design has been widely used in various aspects of life and military, for example, ultraviolet detection devices and some electron sources are photocathodes made of GaN. The GaN photocathode has important application value and development prospect in the fields of ultraviolet detection, biosensors, low-light-level image intensifiers and the like.

In recent years, with the rapid development of GaN photocathode technology, the performance thereof reaches a better level and can be put into use. However, the current GaN photocathode development seems to encounter a bottleneck, and as the research progresses, the performance of the photocathode is difficult to be further improved. The method for improving the performance of the GaN photocathode by changing the substrate, the thickness, the doping concentration and the like is relatively mature, and the quantum efficiency of the GaN photocathode is difficult to further improve.

The superlattice structure has good semiconductor characteristics. If the barrier layers are thin and the coupling between adjacent wells is strong, the discrete energy levels originally in each quantum well will be spread into energy bands whose width and position are related to the depth, width and thickness of the potential well, and such a multilayer structure is called a superlattice. Structures featuring superlattices are sometimes referred to as coupled multiple quantum wells, and if the superlattices are made of two semiconductor materials with different band gaps, each quantum well will form a new selection rule to influence the movement of charges in the structure.

Disclosure of Invention

In order to overcome the bottleneck existing in the prior art, the invention aims to provide the AlGaN/GaN photocathode with the superlattice structure electron emission layer, which can effectively solve the problem of low photoelectric conversion rate in the photocathode and is beneficial to improving the quantum efficiency of the GaN photocathode.

In order to achieve the purpose, the invention adopts the technical scheme that:

an AlGaN/GaN photocathode structure with a superlattice electron emission layer comprises a substrate (11), a buffer layer (12), a p-type superlattice AlGaN/GaN electron emission layer (13) and an activation layer (14) which are sequentially arranged from bottom to top.

The solar cell is characterized in that the AlGaN/GaN electron emission layer (13) with the superlattice structure.

Preferably, the substrate (11) is a sapphire crystal and has a thickness of 400-600 μm. .

Preferably, the buffer layer (12) is AlGaN and has a thickness of 10 to 100 nm.

Preferably, in the p-type superlattice AlGaN/GaN electron emission layer (13), the thickness of the AlGaN layer (21) in a single period is 5-10 nm, and the thickness of the GaN layer (22) is 5-10 nm.

Preferably, in the p-type superlattice AlGaN/GaN electron emission layer (13), the number of the repeating cycles of the superlattice is 4-30.

Preferably, the doped element in the AlGaN/GaN electron emission layer (13) of the p-type superlattice structure is Mg, and the Hall concentration of holes of the doped material is 10¹⁶～10¹⁸cm^-3。

Preferably, the activation layer (14) is a Cs/O activation layer, and the thickness of the activation layer is 1-5 atomic layers. .

The beneficial effects of this technical scheme do: the invention provides an AlGaN/GaN photocathode with an electron emission layer with a superlattice structure. Due to the high transverse carrier mobility and the strong polarization effect of the multi-period superlattice structure, and the original discrete energy levels in the quantum wells are expanded into energy bands, the spatial separation of holes and electrons can be effectively realized, the photoelectric conversion rate of an electron emission layer is improved, and finally the quantum efficiency of the GaN photocathode is improved.

Drawings

Fig. 1 is a schematic view of an AlGaN/GaN photocathode structure having an electron emission layer of a superlattice structure in an embodiment.

Fig. 2 is a schematic structural view of the superlattice AlGaN/GaN electron emission layer in the embodiment.

Detailed Description

The invention is further described below with reference to fig. 1.

As shown in FIG. 1, the AlGaN/GaN photocathode with an electron emission layer of a superlattice structure comprises a substrate (11), a buffer layer (12), a p-type superlattice AlGaN/GaN electron emission layer (13) and an activation layer (14) which are sequentially arranged from bottom to top.

The substrate (11) is a c-plane sapphire crystal and has a thickness of 500 [ mu ] m.

And carrying out double-sided polishing treatment on the c-surface sapphire crystal of the substrate (11).

The buffer layer (12) is an AlGaN layer and has a thickness of 50 nm.

The buffer layer (12) is epitaxially grown by MOCVD.

In the p-type superlattice AlGaN/GaN electron emission layer (13), the thickness of an AlGaN layer (21) in a single period is 8nm, and the thickness of a GaN layer (22) in the single period is 8 nm.

The repeating cycle number of the p-type superlattice AlGaN/GaN electron emission layer (13) is 10, and the total thickness is 160 nm.

The AlGaN/GaN electron emission layer (13) of the p-type superlattice structure contains Mg as a doping element, and the Hall concentration of holes of the doped material is 3 h 10¹⁷cm^-3。

The active layer (14) is a Cs/O active layer.

It must be noted that: the invention is not only suitable for the photoelectric cathode taking superlattice AlGaN/GaN as an electron emission layer, but also suitable for the photoelectric cathode taking superlattice AlGaAs/GaAs as the electron emission layer.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and are intended to be within the scope of the invention.