Growth of quantum fortress structures in Si1-xGex/Si via combinatorial deposition

This study details the evolution of morphologies in the Si1-xGex/Si system, under kinetically controlled conditions of 550 degreesC growth temperature and 1 Angstrom/s growth rate. We find that, with increasing film thickness and Ge fraction, a series of three-dimensional structures develop, starting from pits, and leading to quantum fortresses and ridges. The quantum fortress structures are of special significance because of their potential application in quantum cellular automata. We establish approximate boundaries in the parameter space of film thickness and Ge fraction, in which these structures form. We present a simple model, based on kinetics and strain, to explain the observed structures. (C) 2003 American Institute of Physics.