A Model of Liquid Phase Electroepitaxial Lateral Overgrowth of Semiconductor Epilayers

摘要

Epitaxial lateral overgrowth (ELO) is a method of epitaxial growth on partially masked substrates [1]. First, the substrate is covered by a thin masking film and patterned by photolithography and etching to form on its whole area a grating of mask-free seeding windows. Then, an epitaxial layer is deposited on such substrate. The epilayer nucleates on the seeds and the growth proceeds in the direction normal to the substrate. As soon as the crystallization front exceeds the top layer of the mask, the growth in lateral direction over the masking film starts (see Fig.l). ELO technique is successfully used to reduce defect density in lattice mismatched heteroepitaxial systems [2]. The breakthrough in development of long lifetime GaN/InGaN blue lasers, partly being due to high efficiency of defects filtration during lateral overgrowth, is the most spectacular achievement of the technique. Great practical importance of the ELO technique is the reason of much attention physics and technology of ELO growth have received recently. In this article we present a novel mathematical model for lateral overgrowth of semiconductor layers by the liquid phase electroepitaxy (LPEE) - a solution growth method in which layer growth is driven by passing an electrical current through the solid-liquid interface while the temperature of the system is kept constant. Taking the GaAs system as an example, we show that by varying electrical conductivity of the mask shape and dimensions of ELO layer grown by LPEE can be efficiently tailored. In particular, dome-shaped crystals can be grown if insulating mask is applied, while thin and wide ELO layers are obtained when electrically conductive mask is used, under otherwise the same growth conditions. These results are in very good agreement with our experimental data.