2004 Fiscal Year Final Research Report Summary
Spatial and temporal spectroscopy of the luminescence generated by hot carriers in narrow-gap-semiconductor quantum dots
| Project/Area Number |
14350355
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Toyo University |
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Principal Investigator |
WADA Noboru Toyo University, Engineering, Professor, 工学部, 教授 (40256772)
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| Co-Investigator(Kenkyū-buntansha) |
HANAJIRI Tatsuro Toyo University, Engineering, Associate Professor, 工学部, 助教授 (30266994)
TOYABE Tohru Toyo University, Engineering, Professor, 工学部, 教授 (20266993)
ISHIBASI Kouji RIKEN, Full time researcher, 理化学研究所, 専任研究員 (30211048)
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| Project Period (FY) |
2002 – 2004
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| Keywords | narrow-gap semiconductor / hot carrier / luminescence spectroscopy / nanowires / InAs / InSb / quantum dot / hot luminescence |
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| Research Abstract |
The dynamics of hot carriers in semiconductors has been an intensive research subject for some decades. From a fundamental point of view, the behavior of highly excited, almost free carriers and their interactions with other carriers, phonons, photons and so on is of great interest. Application-wise, understanding the hot carrier dynamics is essential in advancing nano-scale semiconductor devices, where a small voltage easily generates hot carriers in nano-scale dimensions. Intense femto-second laser pulses (λ=780 nm) were used to generate hot carriers in bulk InAs, where not only Stokes luminescence, but also surprisingly strong anti-Stokes luminescence were observed. Moreover, a periodic intensity variation found in the anti-Stokes spectrum was found and may be attributed to two-LO-phonon cascade emission by the hot carriers. Hot carries produced in two-photon absorption process may generate several pairs of LO phonons before they emit a photon by recombination.
The luminescence spatial extent was also probed in InAs and InSb. It was several times larger than the laser spot size (〜2 μ m). Our results suggest that hot carriers in the narrow-gap semiconductors may travel ballistically over a surprisingly long distance. It is also noted that the luminescence intensity exhibited large non-linearity with the excitation laser energy.
In addition, fabrication of the double structured (core-shell and axial superlattice) nanowires with some dots was conducted with FIB apparatus and a furnace. The double structured nanowires consist of crystalline InSb and In_2O_3. The method is simple and can be used to mass-produce compound semiconductor nanowires. Manipulation of Ga-ion beams in nanoscale may enable us to fabricate nanoelectronics devices and nanophotodevices. The detailed conditions and mechanism for creating such novel nanostructures are not clear at this time, but we hope these findings may invoke more interests in compound semiconductor nanowire research.
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