Heteroepitaxial growth on microscale patterned silicon structures

This work is aimed at finding the effect of the patterned size on the quality of the heteroepitaxial growth. We have analyzed heteroepitaxial growth of Ge/SixGe1−x layers on variable duty cycle microscale-patterned Si substrates. These mesa patterns were fabricated using optical lithography, reactive ion and wet-chemical etching techniques. For reference, the quality of the growth on the patterned substrates was compared to that on planar substrates under identical conditions. The quality of the Ge epilayers was evaluated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution X-ray diffraction (HRXRD), and etch pit density (EPD) measurements. Using TEM and X-ray measurements we determined that the defect density is reduced as the size of the posts decreased from 20 to 4 μm, while keeping the center to center distance between the posts constant at 25 μm. The dislocation density obtained for Ge/SixGe1−x on the planar, the smallest patterned and the largest patterned structures were 6×108, 4×107 and 2×108 cm−2, respectively. The typical crosshatch pattern present in the planar samples is not present in the patterned samples.