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See detailFormation of ultra-thin Ge1−xSnx/Ge1−x−ySixSny quantum heterostructures and their electrical properties for realizing resonant tunneling diode
Suwito, Galih Ramadana; Fukuda, Masahiro; Suprayoga, Edi et al

in Applied Physics Letters (2020), 117(23), 232104

Huge thermal noise owing to the narrow energy bandgap is one of the critical issues for group IV-based photonics in the mid-infrared regime. With this motivation, we examined to form Ge1−xSnx ... [more ▼]

Huge thermal noise owing to the narrow energy bandgap is one of the critical issues for group IV-based photonics in the mid-infrared regime. With this motivation, we examined to form Ge1−xSnx/Ge1−x−ySixSny quantum heterostructures (QHs) by molecular beam epitaxy for realizing resonant tunneling diodes composed of group-IV materials. We confirmed the formation of approximately 2 nm-thick Ge1−xSnx/Ge1−x−ySixSny QHs with atomically flat interfaces by x-ray diffraction and transmission electron microscopy methods. Moreover, by the current density–voltage (J–V) measurement at 10 K, we observed the occurrence of a non-linear distinct hump in the J–V characteristic, which is possibly originated from quantum transport of heavy holes. According to the tunneling transmission spectra simulation result, the hump property would be due to two possible scenarios: a resonant tunneling of heavy holes in the QH and/or a resonance phenomenon that heavy holes pass just above a potential barrier. [less ▲]

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See detailModulation of coherent phonon amplitudes in low-dimensional materials by ultrafast laser pulse trains
Nugraha, Ahmad R.; Hanna, Muhammad Y.; Suprayoga, Edi et al

in AIP Conference Proceedings (2020), 2256(1), 020005

We theoretically investigate how coherent phonon amplitudes in low dimensional materials can be modulated by ultrafast laser pulse trains. Important laser parameters for the modulation of coherent phonon ... [more ▼]

We theoretically investigate how coherent phonon amplitudes in low dimensional materials can be modulated by ultrafast laser pulse trains. Important laser parameters for the modulation of coherent phonon amplitudes are the pulse width, repetition period, and number of pulses in the pulse train. We find that it is possible to switch on or switch off the radial breathing mode (RBM) and the G-band phonons in a single wall carbon nanotube (SWNT), as a typical model of low-dimensional materials. In particular, if the repetition period matches with integer multiple of the RBM phonon period, the RBM phonon could be switched on, while the other modes are switched off. On the other hand, for the G-band, which has a higher frequency (shorter period) than the RBM, the number of pulses in the pulse train also affects the switching process. The ratios of the G-band and RBM amplitudes are found to be significantly enhanced at certain integer multiples of pulse number as a function of SWNT diameter. Such a “magic number” phenomenon in ultrafast spectroscopy can be extended to other low-dimensional materials, in which we may realize a phonon switch in the future. [less ▲]

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