We study the photoemission process of graded-doping CaN photocathode and find that the built-in electric fields can increase the escape probability and the effective diffusion length of photo-generated electrons, whic...We study the photoemission process of graded-doping CaN photocathode and find that the built-in electric fields can increase the escape probability and the effective diffusion length of photo-generated electrons, which results in the enhancement of quantum efficiency. The intervalley scattering mechanism and the lattice scattering mechanism in high electric fields are also investigated. To prevent negative differential mobility from appearing, the surface doping concentration needs to be optimized, and it is calculated to be 3.19×10^17 cm-3. The graded-doping GaN photocathode with higher performance can be realized by further optimizing the doping profile.展开更多
GaN samples 1-3 are cleaned by a 2：2：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%） to de-ionized water;hydrochloric acid（37%）;or a 4：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%）...GaN samples 1-3 are cleaned by a 2：2：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%） to de-ionized water;hydrochloric acid（37%）;or a 4：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%）.The samples are activated by Cs/O after the same annealing process.X-ray photoelectron spectroscopy after the different ways of wet chemical cleaning shows：sample 1 has the largest proportion of Ga,N,and O among the three samples,while its C content is the lowest.After activation the quantum efficiency curves show sample 1 has the best photocathode performance.We think the wet chemical cleaning method is a process which will mainly remove C contamination.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 60871012)the Research Fund of Nanjing University of Science and Technology (Grant No. 2010ZYTS032)
文摘We study the photoemission process of graded-doping CaN photocathode and find that the built-in electric fields can increase the escape probability and the effective diffusion length of photo-generated electrons, which results in the enhancement of quantum efficiency. The intervalley scattering mechanism and the lattice scattering mechanism in high electric fields are also investigated. To prevent negative differential mobility from appearing, the surface doping concentration needs to be optimized, and it is calculated to be 3.19×10^17 cm-3. The graded-doping GaN photocathode with higher performance can be realized by further optimizing the doping profile.
基金Projects supported by the National Natural Science Foundation of China (Grant No. 60871012)the National Key Laboratory of Science and Technology Foundation on Low Light Level Night Vision (Grant No. J20110104)the Research and Innovation Plan for Graduate Students of Jiangsu Higher Education Institutions (Grant No. CXZZ11 0238)
文摘GaN samples 1-3 are cleaned by a 2：2：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%） to de-ionized water;hydrochloric acid（37%）;or a 4：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%）.The samples are activated by Cs/O after the same annealing process.X-ray photoelectron spectroscopy after the different ways of wet chemical cleaning shows：sample 1 has the largest proportion of Ga,N,and O among the three samples,while its C content is the lowest.After activation the quantum efficiency curves show sample 1 has the best photocathode performance.We think the wet chemical cleaning method is a process which will mainly remove C contamination.
