Optimal growth of Ge-rich dots on Si(001) substrates with hexagonal packed pit patterns

Abstract

This paper reports a three-step method to fabricate hexagonal ordered Ge dots on Si with controllable size and spacing. After the introduction of a thin Si dioxide layer on the Si substrate, porous alumina turns out to be a good candidate for pattern transferring, which is rapid and simple to implement. A density-temperature relation for Ge dots has been discovered in this work; the Arrhenius relation with a slope of 0.33 is proved to be applicable for predicting the optimal temperature for a certain density of patterns. Different widths of pits are also studied to discover the dependence of the dot distribution on the pit morphology. The optimal pit width for ordered Ge dots is around 30 nm, while four aligned Ge dots can be achieved in a 70 nm pit. Extremely high Ge content (>0.92) in capped Ge dots is discovered by Raman characterization because the high density of pits leads to a low enough optimal temperature of 430 °C. The photoluminescence spectra of the capped dots also prove the high purity and quality of the Ge dots.

Germanium epitaxy on silicon

“…More recently, selective growth of islands in the patterned nanoscale region, or pattern guided growth, has been proposed and has attracted considerable attention. Patterned assisted QDs with precisely controlled site placement, size distribution and dot density have been realized in various nanostructures, including buried dislocation networks [43], stripe mesas [44], 2D hexagonal pits array [45] and lithography-based optical interference patterns [46]. Due to ordering of growth patterns, 2D and 3D QD arrays with perfect site periodicity and size distribution can be obtained provided that the growth parameters are optimized.…”

Optimization of the nanopore depth to improve the electroluminescence for GaN-based nanoporous green LEDs

“…After that, a 300 nm thick anodic aluminum oxide (AAO) membrane with a period of 400 nm was transferred to the LED chip wafer. The details of the transfer method have been reported elsewhere [18]. Then the LEDs were fabricated to be nanoporous by using the AAO membrane as the ICP etching mask.…”

Heteroepitaxy of Ge on Si(001) with pits and windows transferred from free-standing porous alumina mask

“…It is known that GeO formed in the reaction of Ge and SiO 2 sublimates at 625 • C [20]. For ordered Ge nanodots growth in step VI, an optimal temperature of 430 • C was investigated in the earlier work [21]. The surface morphologies and crystal quality of these Ge nanostructures on Si were obtained ex situ by scanning electron microscopy (SEM) (Zeiss Ultra-55), a micro-Raman system (Thermo DXR), a x-ray diffraction (XRD) system (PANalytical's Empyrean), high-power optical microscopy for etch-pit-density (EPD) counting and transmission electron microscopy (TEM) (200 kV Tecnai G2) with scanning mode, energy dispersive spectroscopy (EDS) and electron diffraction (ED).…”

“…In our earlier work, large-scale ordered Ge dots on Si pits were achieved by optimizing the growth conditions; a density-temperature relation was discovered [21]. The relation is very useful for predicting the optimal temperature for adatoms growth and migration on substrates with nanopatterns of a certain density.…”