Analysis of Ge distribution in Si 1 − xGe x single crystal fibers by the micro-pulling down method

Abstract

The Ge distribution in both melt and crystal was analyzed for the growth of Si 1 − x Ge x ( x = 0.05) single crystal fibers by the micro-pulling down (μ-PD) method. The solute accumulation volume in the vicinity of the interface comprises the molten zone (zone I) next to the interface and the capillary zone (zone II) leading to the bulk melt. A steady-state solution was given for each of these two zones and the initial transient analysis lead to the equilibrium partition coefficient, k 0 and diffusion constant, D, for Ge in the Si 1 − x Ge x ( x = 0.05) melt to be 0.43 and 5.6 × 10 −5cm 2s −1, respectively. A sudden change of either the growth velocity or the molten zone volume size during steady-state growth yields an abrupt change of Ge distribution, and its change mode is interpreted in terms of the degree of imbalance of the Ge mass flow between zone I and zone II at the zone boundary. It is, therefore, suggested that the desired impurity distribution in a Si single crystal fiber can be designed by the manipulation of the imbalance of the impurity mass flow at the zone boundary.