Spontaneous Nanopatterning and Strain Relaxation in SiGe Layers Grown by Oxidative Solid Phase Epitaxy

The wafer-scale monolithic integration of III-V materials on Si would lead to revolutionary optoelectronic hardware for data, computing and other applications. However, heteroepitaxy of III-Vs on Si requires overcoming the large lattice and thermal mismatches between the materials and reducing threading dislocations densities. In this work, we explore the oxidative solid phase epitaxy (SPE) of Ge+ implanted Si(111) to form ultra-thin strain-relieving SiGe metamorphic buffer layers for heteroepitaxy on Si. The SPE process is shown to result in a nanopatterning of the Ge concentration variation across the sample surface, visible by scanning and transmission electron microscopy (SEM and TEM). The concentration patterning is the result of a hexagonal network of Shockley partial dislocations at the SiGe/Si interface. Analyzing the pattern spacing observed by SEM is demonstrated as an easy, non-destructive method for obtaining the local strain state of SiGe layers. This work is important for engineering ultra-thin SiGe metamorphic buffer layers for III-V optoelectronics heteroepitaxy on the silicon platform.