BaO半导体薄膜在外加垂直表面电场作用下的近紫外光吸收增强现象研究

STUDY OF ENHANCED PHOTOABSORPTION OF BaO THIN FILMS IN THE NEAR-ULTRAVIOLET BAND WITH APPLIED VERTICAL ELECTRIC FIELD ON THE SURFACE

通过对真空蒸发沉积制备的BaO半导体薄膜在外加垂直表面电场作用下光吸收特性的测试 ,实验上观察到BaO薄膜在近紫外波段的光吸收随电场强度的增加而明显增强 .理论分析表明 ,BaO半导体薄膜在外加垂直表面电场作用下发生能带倾斜 ,价带电子隧穿带间位垒而在带隙中出现的概率增加 ,近紫外波段光吸收增强是光子协助隧道穿越的结果 .不同能量光子激发下电场作用引起的BaO薄膜光吸收增强现象是夫兰茨 凯尔迪什 (Franz Keldysh)效应和斯塔克 (Stark)

The optical absorption properties of BaO semiconductor thin films deposited by vacuum evaporation were measured when a vertical electric field was applied on the surface of the thin films.Enhanced absorption in the near\|ultraviolet band was observed.The absorption was increased with the increased intensity of applied electric field.Theoretical analysis indicates that the energy\|band edges of BaO semiconductor become bent on the application of electric field,and there is an increased probability for electrons in the valence band to tunnel through the forbidden gap according to the quantum\|mechanics.As a result,it becomes possible for the photons with energy less than E \-g to be absorbed by the electrons,and which leads to the enhanced photoabsorption of BaO thin films in the near\|ultraviolet band.Franz\|Keldysh effect and Stark effect were used to explain the electroabsorption spectrum when metal oxide semiconductor was excited by the photons with energy less or more than E g.