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III–V compound semiconductor quantum dots photonic devices are very attractive because of their low power consumption, temperature stability, and high-speed modulation. We studied and developed a defect-free top-down fabrication process for sub-20-nm GaAs nanodisks (NDs) that uses bio-template and neutral beam etching. We successfully fabricated 100-nm-high nanopillars embedding 4- and 8-nm-thick GaAs quantum well and 30-nm-thick Al0.3Ga0.7As barrier-stacked structures. The nanopillars were mounted by metalorganic vapor phase epitaxy. We measured visible light photoluminescence at a low temperature originating from the GaAs NDs. Nanodisks fabricated by the top-down process have a great potential for use in high-performance III–V photonic devices. [ABSTRACT FROM PUBLISHER]

Silicon (Si) quantum dot (QD) materials have been proposed for all-Silicon tandem solar cells. In this study, for the first time, high efficiency solar cells consisting of a sub-10-nm highly ordered and dense 2-dimensional (2D) array (one layer) of Si nanodisks (Si-ND) with a silicon carbide (SiC) interlayer have been fabricated. These Si-NDs were fabricated with an original top-down process involving a 2D-array bio-template etching mask made of Listeria-Dps (Li-Dps) with a 4.5-nm-diameter iron oxide core and damage-free neutral beam etching (Si-ND diameter: 6.4 nm). The Si-ND 2D array with a SiC interlayer had an extremely high optical absorption coefficient and high carrier transport due to the formation of a wide mini-band between the Si-NDs through the SiC interlayer. As a result, an open-circuit voltage of 0.556 V, short-circuit current of 31.3 mA/cm2, fill factor of 72%, and conversion efficiency of 12.6% were accomplished just by inserting one-layer Si-NDs in solar cells. [ABSTRACT FROM PUBLISHER]

We fabricated a highly ordered and dense 2-dimensional array of Si nanodisks (NDs) with our new processes using a bio-template and damage-free neutral beam. Direct-bandgap-like photon emissions were observed from the Si-NDs due to quantum confinement by using time resolved PL measurements. The PL time-profiles were identified in three components (nanosecond region or less) originated in lateral coupling of wave-function i.e. miniband state and localized state in silicon nanodisks. Furthermore, The I-V characteristics of the 2D array of Si-NDs using conductive atomic force microscopy (AFM) indicated that the electronic states of the neighboring NDs were coupled and formed minibands in the 2D array. We also fabricated Si-NDs with an inter-layer of SiC, and found that the SiC matrix could yield a high absorption coefficient without any shift in the bandgap energy (Eg) of the Si-ND structure. [ABSTRACT FROM PUBLISHER]

A series of damage-free fabrication processes for a two-dimensional array of sub-10-nm GaAs nanodiscs was developed by using bio-templates and neutral beam etching. The photoluminescence of GaAs etched with a neutral beam clearly revealed that the processes could accomplish defect-free etching for GaAs. In the bio-template process, a hydrogen-radical treatment was used to remove the native oxide on the GaAs surface, and then neutral beam oxidation (NBO) was used to form a hydrophilic 1-nm-thick GaAs oxide (GaAs-NBO) film. The two-dimensional array of ferritins (protein including a 7-nm-diameter iron core) can be arranged well on hydrophilic GaAs-NBO film. The ferritin protein shell was removed using an oxygen-radical treatment at a low temperature of 280°C without thermal damage to the GaAs. Then, the neutral beam etched the the GaAs to form defect-free nanodisc structure of using the iron core as an etching mask. Finally, the iron oxide core was removed by wet etching with diluted hydrogen chloride and the fabrication process was completed without inflicting any damage to the GaAs. As a result, a two-dimensional array of GaAs quantum dots with a diameter of ∼7 nm, a height of ∼10 nm, a high taper angle of 88°, and a quantum dot density of more than 7×1011 cm−2 was successfully fabricated without causing any damage to the GaAs. [ABSTRACT FROM PUBLISHER]