PHASE-TRANSFORMATION OF CRYSTALLINITY OF SI1-XGEX LAYERS GROWN ON SI(001) BY LOW-TEMPERATURE MOLECULAR-BEAM EPITAXY

Abstract

The phase transformation of crystallinity of Si1-xGex layers (0 less than or equal to x less than or equal to 0.67) on Si(001) grown at low temperature (150-430 degrees C) is investigated. During the growth of a Si1-xGex layer, its crystallinity changes from single crystalline to amorphous or polycrystalline phase. As the Ge mole fraction x increases, the thickness of the single crystalline phase, the so-called limiting thickness h(L), increases exponentially and the crystallinity beyond h(L) changes from amorphous to polycrystalline phase. Moreover, the decrease of growth temperature at which the polycrystalline phase begins to appear beyond h, and the randomization of polycrystalline texture are also observed as increasing x. These alloy characteristics of the crystallinity transformation depending on x can be explained by lower melting point of Ge than of Si, since the increase of x can lower the thermal processing temperature of Si1-xGex alloy to get a physical phenomenon equivalent to that of pure Si.