多层复杂结构GaAs基光电阴极的光学性能和量子效率

Optical properties and quantum efficiency of multilayer complicated GaAs-based photocathode

为了更好地了解这两种结构对光电发射性能的影响,设计和生长了两种结构的光电阴极样品,对其光电发射性能进行比较,并利用薄膜光学的矩阵法推导的光学性能公式以及通过求解一维连续性方程推导的量子效率模型,对比研究了光电阴极发射层、缓冲层厚度变化以及AlxGa1-xAs缓冲层中Al组分变化对两种结构光电阴极光学性能和量子效率的影响。这两种结构对光电发射性能的影响机理并不相同,因此作用效果也大不一样。渐变带隙结构的光电阴极通过引入内建电场和减少界面复合从而提升光电发射性能,而DBR结构则通过形成法布里-罗伯共振腔,使得特定波长的入射光在共振腔内来回反射进而被多次吸收,从而加强光电发射。激活实验结果表明,DBR结构样品的发射效率与渐变带隙结构相比具有明显优势,尤其是在755,808和880 nm处有更高的发射效率峰值,可分别提升37.5%,38.9%和47.0%。最后利用模型拟合了量子效率曲线,验证了光学性能参量对复杂结构光电阴极的重要影响及理论模型的合理性。

To comprehensively assess the impact of these structures on photoelectric emission perfor⁃mance,we design and cultivate photocathode samples featuring both configurations,subsequently comparing their photoemission performance.Optical properties and the quantum efficiency model are ascertained through the matrix method of thin-film optics and one-dimensional continuity equations,respectively.We examine and analyze the effects of varying the thickness of the emission layer,altering the buffer layer,and adjusting the Al component within the buffer layer on the optical properties and quantum efficiencies of these two photocathode structures via simulations.These two structures exert distinct influences on photo⁃electric emission performance due to their disparate mechanisms.Consequently,their effects on photo⁃emission performance exhibit substantial differences.The photocathode with the graded bandgap structure improves the photoelectric emission performance by introducing a built-in electric field and reducing inter⁃face recombination.Conversely,the DBR structure augments the photoelectric emission by forming a Fab⁃ry Robb resonant cavity,so that incident light of a specific wavelength can be reflected back and forth in the resonant cavity and absorbed many times.The results of an activation experiment indicate that the emission efficiency of DBR structures exceeds that of graded bandgap structures.Notably,higher emis⁃sion efficiency peak values are obtained at the wavelengths of 755,808,and 880 nm,which can be im⁃proved by 37.5%,38.9%,and 47.0%,respectively.Furthermore,the quantum efficiency curves are well fitted using the derived model,confirming the importance of optical performance parameters and the model’s validity.