Size dependent light absorption modulation and enhanced carrier transport in germanium quantum dots devices

Cosentino, Salvatore; Barbagiovanni, Eric G.; Crupi, I.; Miritello, M.; Nicotra, Giuseppe; Spinella, C.; Pacifici, Domenico; Mirabella, S.; Terrasi, A.

doi:10.1016/j.solmat.2014.09.012

Cited by 33 publications

(34 citation statements)

References 39 publications

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“…Because of the quantum confinement effect, it is possible to tune the band gap of the nanocrystals. Over the years, this was done for various QD materials [22][23][24], confirming that there is a red shift in absorption for larger dots. However, core/shell structures are more complex.…”

Section: Discussionmentioning

confidence: 81%

Ge/Si core/shell quantum dots in alumina: tuning the optical absorption by the core and shell size

et al. 2017

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Ge/Si core/shell quantum dots (QDs) recently received extensive attention due to their specific properties induced by the confinement effects of the core and shell structure. They have a type II confinement resulting in spatially separated charge carriers, the electronic structure strongly dependent on the core and shell size. Herein, the experimental realization of Ge/Si core/shell QDs with strongly tunable optical properties is demonstrated. QDs embedded in an amorphous alumina glass matrix are produced by simple magnetron sputtering deposition. In addition, they are regularly arranged within the matrix due to their self-assembled growth regime. QDs with different Ge core and Si shell sizes are made. These core/shell structures have a significantly stronger absorption compared to pure Ge QDs and a highly tunable absorption peak dependent on the size of the core and shell. The optical properties are in agreement with recent theoretical predictions showing the dramatic influence of the shell size on optical gap, resulting in 0.7 eV blue shift for only 0.4 nm decrease at the shell thickness. Therefore, these materials are very promising for light-harvesting applications.

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Section: Discussionmentioning

confidence: 81%

Ge/Si core/shell quantum dots in alumina: tuning the optical absorption by the core and shell size

et al. 2017

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“…Details on the SiGeO deposition, Ge diffusion, QD growth and structural order of Ge QDs are given in ref. 4,25,33. The presence and the size distribution of Ge QDs were evaluated by cross sectional transmission electron microscopy in scanning mode (STEM) analysis.…”

Section: Methodsmentioning

confidence: 99%

“…We evaluated the experimental absorption cross section from direct optical transmission and reflectance spectra of Ge QD films, as discussed in detail in ref. 4,16. The absorption cross section gives the probability of photon absorption normalized by the Ge content, 20 thus representing an intrinsic property to be compared among different samples.…”

Section: Methodsmentioning

confidence: 99%

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The role of the interface in germanium quantum dots: when not only size matters for quantum confinement effects

et al. 2015

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Quantum confinement (QC) typically assumes a sharp interface between a nanostructure and its environment, leading to an abrupt change in the potential for confined electrons and holes. When the interface is not ideally sharp and clean, significant deviations from the QC rule appear and other parameters beyond the nanostructure size play a considerable role. In this work we elucidate the role of the interface on QC in Ge quantum dots (QDs) synthesized by rf-magnetron sputtering or plasma enhanced chemical vapor deposition (PECVD). Through a detailed electron energy loss spectroscopy (EELS) analysis we investigated the structural and chemical properties of QD interfaces. PECVD QDs exhibit a sharper interface compared to sputter ones, which also evidences a larger contribution of mixed Ge-oxide states. Such a difference strongly modifies the QC strength, as experimentally verified by light absorption spectroscopy. A large size-tuning of the optical bandgap and an increase in the oscillator strength occur when the interface is sharp. A spatially dependent effective mass (SPDEM) model is employed to account for the interface difference between Ge QDs, pointing out a larger reduction in the exciton effective mass in the sharper interface case. These results add new insights into the role of interfaces on confined systems, and open the route for reliable exploitation of QC effects.

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“…Положительным результатом является то, что в струк-турах с включением Ge наблюдались более сильные токи при обратном смещении при освещении солнечным эталоном. По всей вилимости это является следствием повышения поглощения света видимого диапазона и уве-личении генерации носителей заряда в nc-Ge с атомами кислорода на границах [25]. Возможно, при оптимизации слоев можно достичь хорошей фоточувствительности данных структур и в ближнем ИК-диапазоне.…”

Section: темновой ток освещениеunclassified

Формирование и исследование p-i-n-структур на основе двухфазного гидрогенизированного кремния со слоем германия в i-области

Кривякин¹,

Володин²,

Шкляев³

et al. 2017

Физика И Техника Полупроводников

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Методом плазмохимического осаждения сформированы четыре пары p-i-n-структур на основе pm-Si:H (полиморфного Si : H). Структуры в каждой паре выращивались на одной подложке так, что одна из них была без Ge в i-слое, а другая содержала Ge, который осаждался слоем толщиной 10 нм методом вакуумного напыления. Пары различались между собой температурой подложки при осаждении Ge, которая была 300, 350, 400 и 450 oC. Данные электронной микроскопии показали, что структуры, полученные при 300 oC, содержали нанокристаллы Ge (nc-Ge), центрами зарождения которых являлись нанокристаллические включения на поверхности pm-Si:H. Концентрация nc-Ge увеличивалась c возрастанием температуры. Исследование вольт-амперных характеристик показало, что наличие Ge в i-слое уменьшало плотность тока короткого замыкания в p-i-n-структурах, когда они использовались как солнечные элементы, тогда как наблюдалось увеличение тока под действием освещения при обратном смещении. Полученные результаты согласуются с известными данными для структур с кластерами Ge в Si, согласно которым кластеры Ge увеличивают коэффициент поглощения света, но также увеличивают и скорость рекомбинации носителей. DOI: 10.21883/FTP.2017.10.45024.8547

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Size dependent light absorption modulation and enhanced carrier transport in germanium quantum dots devices

Cited by 33 publications

References 39 publications

Ge/Si core/shell quantum dots in alumina: tuning the optical absorption by the core and shell size

Ge/Si core/shell quantum dots in alumina: tuning the optical absorption by the core and shell size

The role of the interface in germanium quantum dots: when not only size matters for quantum confinement effects

Формирование и исследование p-i-n-структур на основе двухфазного гидрогенизированного кремния со слоем германия в i-области

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