Strain tailoring in heavily Sb-doped Ge via pulsed laser melting

This study investigates the lattice strain induced by Ge:Sb alloy films on Ge substrates. Metastable films are formed by UV pulsed laser melting (PLM) of a Sb-coated Ge substrate. We fabricate thin Ge:Sb layers, systematically varying processing parameters and crystal orientation to study strain and strain-relaxation-induced defects. High-resolution X-Ray diffraction and electrical characterization revealed extremely high strain values as well as ultra-low resistivity induced by Sb. Maximum strain before the onset of strain relaxation was found to depend on crystal orientation with the Ge (111) orientation yielding the highest strain values. By combining structural as well as electrical information, we estimated Sb contribution to lattice expansion, separating electronically active from inactive fractions. Strain optimization was applied to an innovative application that is the production of bent crystals for high energy particle beam deflection and radiation production. Bending tests on thin Ge substrates confirmed the method, with controlled PLM processing allowing inducing quantifiable curvature with smallest achievable radii of 4.5 m. Exploiting non-equilibrium doping/alloying to exceed equilibrium Sb solubility is promising for applications ranging from ultra-low-resistivity layers in scaled nano-electronic devices to bent crystals for advanced systems like crystal-based undulators, enabling new approaches to highenergy photon production.