Epitaxial Ge-on-Nothing and Epitaxial Ge on Si-on-Nothing as Virtual Substrates for 3D Device Stacking Technologies

Abstract

Two new templates for strain-relaxed detachable Ge are introduced. The first one is based on epitaxial growth of Ge on a Si-on-Nothing (SiON) platform while the second consists of Ge-on-Nothing (GeON). The SiON and GeON templates are obtained from the reorganization of macro-porous Si and Ge, respectively, fabricated on regular Si substrates using conventional lithography, dry-etching and annealing routines. Both templates contain similar densities of threading dislocations as typically obtained for conventional strain relaxed epitaxial Ge grown on bulk Si. In the GeON case, the excess carrier lifetime (32 ns) as extracted from time-resolved photoluminescence was > 4 times higher than the values measured for Ge grown on bulk Si with a similar thickness of the Ge layer. Both templates can be considered for novel device applications relying on thin Ge films and as starting material for layer transfer and 3-dimensional device stacking technologies, provided that a successful detachment from the parent substrate can be demonstrated. The reduction of non-radiative electron-hole recombinations makes the GeON also attractive for the fabrication of optical devices used in the fields of communication and imagers, such as Ge photodetectors and modulators, as lower dark currents are expected.