Gallium arsenide (GaAs) island growth under SiO2 nanodisks patterned on GaAs substrates

We report a growth phenomenon where uniform gallium arsenide (GaAs) islands were found to grow underneath an ordered array of SiO2 nanodisks on a GaAs(100) substrate. Each island eventually grows into a pyramidal shape resulting in the toppling of the supported SiO2 nanodisk. This phenomenon occurred consistently for each nanodisk across a large patterned area of ~ 50 ×50 µm2 (with nanodisks of 210 nm diameter and 280 nm spacing). The growth mechanism is attributed to a combination of 'catalytic' growth and facet formation.

Source:IOPscience

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Room-temperature bonding of GaAs//Si and GaN//GaAs wafers with low electrical resistance

The electrical properties of room-temperature bonded wafers made from materials with different lattice constants, such as p-GaAs and n-Si, p-GaAs and n-Si [both with an indium tin oxide (ITO) surface layer], and n-GaN and p-GaAs, were investigated. The bonded p-GaAs//n-Si sample exhibited an electrical interface resistance of 2.8 × 10−1 Ωcenterdotcm2 and showed ohmic-like characteristics. In contrast, the bonded p-GaAs/ITO//ITO/n-Si sample showed Schottky-like characteristics. The bonded n-GaN//p-GaAs wafer sample exhibited ohmic-like characteristics with an interface resistance of 2.7 Ωcenterdotcm2. To our knowledge, this is the first reported instance of a bonded GaN//GaAs wafer with a low electrical resistance.

Source:IOPscience

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Precursor flow rate manipulation for the controlled fabrication of twin-free GaAs nanowires on silicon substrates

Vertically oriented GaAs nanowires (NWs) are grown on Si(111) substrates using metal–organic chemical vapor deposition. Controlled epitaxial growth along the 〈111〉 direction is demonstrated following the deposition of thin GaAs buffer layers and the elimination of structural defects, such as twin defects and stacking faults, is found for high growth rates. By systematically manipulating the AsH3 (group-V) and TMGa (group-III) precursor flow rates, it is found that the TMGa flow rate has the most significant effect on the nanowire quality. After capping the minimal tapering and twin-free GaAs NWs with an AlGaAs shell, long exciton lifetimes (over 700 ps) are obtained for high TMGa flow rate samples. It is observed that the Ga adatom concentration significantly affects the growth of GaAs NWs, with a high concentration and rapid growth leading to desirable characteristics for optoelectronic nanowire device applications including improved morphology, crystal structure and optical performance.

Source:IOPscience

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