Browsing by Author "Yeh, SH"

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Edge quantum yield in n-channel metal-oxide-semiconductor field-effect transistor
(2004-08-01)
Kang, TK
;
Su, KC
;
Chang, YJ
;
Chen, MJ
;
Yeh, SH
The quantum yield of impact ionization is performed on an n-channel metal-oxide-semiconductor field-effect transistor (n-MOSFET) by a carrier separation measurement. When the n-MOSFET is biased in accumulation, the carrier separation measurement demonstrates that the gate current mainly originates from the electrons injected into the underlying drain/source overlap regions. The measured substrate current is due to excess holes originating from the impact ionization of the injected electrons in the overlap regions. Therefore, the quantum yield in the overlap regions can be determined by the ratio of the substrate current to the gate current. It is well matched with the theoretical calculation of quantum yield. (C) 2004 American Institute of Physics.
Electron-hole capture suppression and ultraviolet emission in conjugated polymers under high electric fields
(2002-06-15)
Chen, ES
;
Yeh, SH
;
Meng, HF
;
物理研究所
;
Institute of Physics
The probability for the Coulomb capture of an electron-hole pair to form an exciton in conjugated polymers is found to be significantly suppressed under high electric field, which is usually required for electroluminescence due to the low mobility. The Coulomb capture is a continuous descent of electronic energy through cascade emission of phonons, and the high field prevents this descent by heating up the carriers. On the other hand, ultraviolet emission through direct interband transition is found to be much less affected by the field, and becomes the dominant radiative decay channel for field beyond 10(8) V/m. Combined with impact ionization, our model provides a complete quantitative explanation of the peculiar high-field behaviors of the visible emission, ultraviolet emission, and current observed in conjugated polymer both before and after the avalanche breakdown.