TY - JOUR
T1 - Femtosecond-laser-driven photoelectron-gun for time-resolved cathodoluminescence measurement of GaN
AU - Onuma, T.
AU - Kagamitani, Y.
AU - Hazu, K.
AU - Ishiguro, T.
AU - Fukuda, T.
AU - Chichibu, S. F.
N1 - Funding Information:
The authors would like to thank K. Uta of Unsys, Ltd. for technical support on PE-gun construction. The principal author (S.F.C.) would like to thank Dr. Q. Bao, Dr. D. Tomida, and Professor C. Yokoyama for the technical help on AT-GaN growth. This work was supported in part by grant-in-aids of CANTech, IMRAM, Tohoku University, the Project of Strategic Development for Energy Conservation Technology driven by New Energy and Industrial Technology Development Organization programs by the Ministry of Economy, Trade, and Industry, and a grant-in-aid for scientific research on priority areas (Grant. No. 18069001) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
PY - 2012/4
Y1 - 2012/4
N2 - A rear-excitation femtosecond-laser-driven photoelectron gun (PE-gun) is developed for measuring time-resolved cathodoluminescence (TRCL) spectrum of wide bandgap materials and structures such as semiconductors and phosphors. The maximum quantum efficiency of a 20-nm-thick Au photocathode excited using a frequency-tripled Al 2O 3:Ti laser under a rear-excitation configuration is 3.6 × 10 -6, which is a reasonable value for a PE-gun. When the distance between the front edge of the PE-gun and the observation point is 10 mm, the narrowest electron-beam (e-beam) diameter is 19 m, which corresponds to one tenth of the laser-beam diameter and is comparable to the initial e-beam diameter of a typical W hair-pin filament of thermionic electron-gun. From the results of TRCL measurements on the freestanding GaN grown by the ammonothermal method and a GaN homoepitaxial film grown by metalorganic vapor phase epitaxy, overall response time for the present TRCL system is estimated to be 8 ps. The value is the same as that of time-resolved photoluminescence measurement using the same excitation laser pulses, meaning that the time-resolution is simply limited by the streak-camera, not by the PE-gun performance. The result of numerical simulation on the temporal e-beam broadening caused by the space-charge-effect suggests that the present PE-gun can be used as a pulsed e-beam source for spatio-time-resolved cathodoluminescence, when equipped in a scanning electron microscope.
AB - A rear-excitation femtosecond-laser-driven photoelectron gun (PE-gun) is developed for measuring time-resolved cathodoluminescence (TRCL) spectrum of wide bandgap materials and structures such as semiconductors and phosphors. The maximum quantum efficiency of a 20-nm-thick Au photocathode excited using a frequency-tripled Al 2O 3:Ti laser under a rear-excitation configuration is 3.6 × 10 -6, which is a reasonable value for a PE-gun. When the distance between the front edge of the PE-gun and the observation point is 10 mm, the narrowest electron-beam (e-beam) diameter is 19 m, which corresponds to one tenth of the laser-beam diameter and is comparable to the initial e-beam diameter of a typical W hair-pin filament of thermionic electron-gun. From the results of TRCL measurements on the freestanding GaN grown by the ammonothermal method and a GaN homoepitaxial film grown by metalorganic vapor phase epitaxy, overall response time for the present TRCL system is estimated to be 8 ps. The value is the same as that of time-resolved photoluminescence measurement using the same excitation laser pulses, meaning that the time-resolution is simply limited by the streak-camera, not by the PE-gun performance. The result of numerical simulation on the temporal e-beam broadening caused by the space-charge-effect suggests that the present PE-gun can be used as a pulsed e-beam source for spatio-time-resolved cathodoluminescence, when equipped in a scanning electron microscope.
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U2 - 10.1063/1.3701368
DO - 10.1063/1.3701368
M3 - Review article
C2 - 22559547
AN - SCOPUS:84860550765
SN - 0034-6748
VL - 83
JO - Review of Scientific Instruments
JF - Review of Scientific Instruments
IS - 4
M1 - 043905
ER -