Morphological Relaxation of Strained Epitaxial Films for Stripe‐Geometry Devices

Abstract

One of the major issues when reducing the channel length in strained transistors is the stress relaxation that significantly degrades the carriers mobility. A new morphological evolution is reported here, describing the relaxation of a strained epitaxial film deposited on a pattern characterized by stripe geometry, both paradigmatic of two‐dimensional (2D) like systems, and characteristic of many devices. The thermodynamic surface diffusion framework accounting for elasticity and capillarity is investigated. The former is solved in two dimensions thanks to the Airy formalism. The resulting dynamical Schrödinger‐like equation governing the film shape evolution is then solved thanks to a decomposition on eigenmodes. It reveals different developments depending upon the system's geometric parameters and the time scale. Mass transfer occurs toward the relaxed areas and creates a ridge at the nanolayers edges, controlled by the geometry and the scale of the structure. These results allow to refine the potential control of electronic properties via the geometry of a system.