摘要
To theoretically research the influence of a varied Al component on the active layer of AlGaN photocathodes,the first principle based on density functional theory is used to calculate the formation energy and band structure of AlxGa（1-x）N with x at 0,0.125,0.25,0.325,and 0.5.The calculation results show that the formation energy declines along with the Al component rise,while the band gap is increasing with Al component increasing.AlxGa（1-x）N with x at 0,0.125,0.25,0.325,and 0.5 are direct band gap semiconductors,and their absorption coefficient curves have the same variation tendency.For further study,we designed two kinds of reflection-mode AlGaN photocathode samples.Sample 1 has an AlxGa（1-x）N active layer with varied Al component ranging from0.5 to 0 and decreasing from the bulk to the surface,while sample 2 has an AlxGa（1-x）N active layer with the fixed Al component of 0.25.Using the multi-information measurement system,we measured the spectral response of the activated samples at room temperature.Their photocathode parameters were obtained by fitting quantum efficiency curves.Results show that sample 1 has a better spectral response than sample 2 at the range of short-wavelength.This work provides a reference for the structure design of the AlGaN photocathode.
To theoretically research the influence of a varied Al component on the active layer of AlGaN photocathodes,the first principle based on density functional theory is used to calculate the formation energy and band structure of AlxGa（1-x）N with x at 0,0.125,0.25,0.325,and 0.5.The calculation results show that the formation energy declines along with the Al component rise,while the band gap is increasing with Al component increasing.AlxGa（1-x）N with x at 0,0.125,0.25,0.325,and 0.5 are direct band gap semiconductors,and their absorption coefficient curves have the same variation tendency.For further study,we designed two kinds of reflection-mode AlGaN photocathode samples.Sample 1 has an AlxGa（1-x）N active layer with varied Al component ranging from0.5 to 0 and decreasing from the bulk to the surface,while sample 2 has an AlxGa（1-x）N active layer with the fixed Al component of 0.25.Using the multi-information measurement system,we measured the spectral response of the activated samples at room temperature.Their photocathode parameters were obtained by fitting quantum efficiency curves.Results show that sample 1 has a better spectral response than sample 2 at the range of short-wavelength.This work provides a reference for the structure design of the AlGaN photocathode.
基金
supported by the National Natural Science Foundation of China(Nos.61308089,6144005)
the Public Technology Applied Research Project of Zhejiang Province(No.2013C31068)
