Ultrathin Si films grown epitaxially on porous silicon

Abstract

Homoepitaxial growth on a porous silicon (PS) substrate anodized from Si(111) was investigated by reflection high energy electron diffraction (RHEED), high resolution scanning electron microscope (SEM) and Rutherford backscattering spectrometry (RBS). The Si growth was carried out on a PS substrate with various porosities (ϱ p) at substrate temperatures of 760–820°C, resulting in that substrate temperatures above 800°C are desirable for an in-situ chemical etching of SiO 2 by a Si beam. For ϱ p < 47% the Si thickness necessary to complete the 7 × 7 structure increases gradually with the porosity, while it increases drastically with ϱ p > 47%. These results are discussed in relation to the structure of the top PS surface. The effectiveness of the PS substrate anodized with dual rates (first at 5 mA/cm 2 and secondly at 50 mA/cm 2) is also discussed in comparison to the results for the single rate anodization.