Browsing by Author "Cheng, C."

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Enhanced optical properties of InAs/GaAs quantum dots grown by radio-frequency hydrogen plasma-assisted molecular beam epitaxy
(2011-02-01)
Katkov, A. V.
;
Chi, Jim
;
Wang, C. C.
;
Cheng, C.
;
電子工程學系及電子研究所
Strong enhancement of photoluminescence (PL) efficiency has been observed in a GaAs/InAs quantum dots-in-a-well structure, grown with in situ irradiation of atomic hydrogen supplied by a radio-frequency hydrogen plasma source. The PL enhancement and wavelength position at room temperature have been found to be stable under extensive thermal annealing up to 630 degrees C in vacuum. As shown by the corresponding improvement of the barrier material, the possible mechanism for PL enhancement is the reduced nonradiative recombination in the barrier region by in situ passivation of defects while they are generated.
High Content Nd-Fe-B in Polymer Composite by Fused Depo-sition Modeling
(2018-01-01)
Chang, T.
;
Jyun, J. K.
;
Lee, W.
;
Tsai, M.
;
Cheng, C.
Optical property improvement of InAs/GaAs quantum dots grown by hydrogen-plasma-assisted molecular beam epitaxy
(2011-05-01)
Katkov, A. V.
;
Wang, C. C.
;
Chi, J. Y.
;
Cheng, C.
;
Gutakovskii, A. K.
An order-of-magnitude increase of photoluminescence (PL) efficiency at room temperature has been observed in the GaAs/InAs quantum dots (QDs)-in-a-well structure grown with in situ irradiation of atomic hydrogen supplied by a radio-frequency hydrogen-plasma source. The enhancement in PL intensity rapidly increases with the hydrogen flow rate and is stable with a variation of excitation power in the radio-frequency plasma source. Extensive thermal annealing of grown samples up to 634 degrees C did not show any significant degradation of photoluminescence intensity compared with the reference sample. The reduction of nonradiative recombination centers in the as-grown sample causes the greatly enhanced luminescence property. In addition to PL enhancement the authors observed that the H-assisted growth of InAs QDs has suppressed bimodal distribution of QD shape. In contrast to the hydrogen-plasma-assisted growth, irradiation by hydrogen in molecular form has a detrimental effect on the optical properties of similar structures. The high thermal stability of improved optical properties suggests that the formation of the defects which are responsible for nonradiative recombination channels is suppressed during H-assisted epitaxy although in situ defect passivation by atomic hydrogen cannot be completely ruled out. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3570870]