M. Chen; A. S. Sologubenko; J. M. Wheeler
Matter 6 (2023) 1903-1927
Germanium displays enhanced carrier mobility under mechanical straining, which makes it an important material for optoelectronics and ultrafast semiconductor devices. However, it is extremely brittle at ambient temperature. Here, we demonstrate plasticity in single-crystalline Ge over a wide temperature range, even at cryogenic temperatures, by using in situ compression of micron-sized specimens. Micromechanical tests were performed from −100°C to 400°C, which spans a homologous temperature range of 0.14–0.56 Tm for Ge. This wide temperature range includes two transitions in dislocation-mediated plastic deformation: the shuffle-to-glide (∼0.31 Tm) and brittle-to-ductile (∼0.47 Tm) transitions. Size effect in Ge is weak for deformation via partial dislocations but more pronounced via perfect dislocations. This study provides comprehensive knowledge for the fundamental understanding of temperature- and size-dependent plasticity and associated defect behavior in covalent semiconductors and practical guidelines for fabrication of robust Ge-based micro-structures for device applications.