EPITAXIAL ORIENTATION OF BETA-FESI2/SI HETEROJUNCTIONS OBTAINED BY RTP CHEMICAL-VAPOR-DEPOSITION

In recent years the semiconducting phase of iron silicide beta-FeSi2 has attracted interest. Promising applications of a great deal of beta-FeSi2/Si heterojunctions are reported in semiconductor technology due to the 0.89 eV direct band gap of beta-FeSi2. Most of the papers devoted to this material present three different deposition modes, i.e. MBE, Solid Phase Epitaxy (SPE) and Reactive Deposition Epitaxy (RDE). The epitaxy of very thin layers of beta-FeSi2 has already been reported on (111) and (001) silicon substrates. This paper presents an original application of Chemical Vapor Deposition (CVD) for the growth of beta-FeSi2 using Rapid Thermal Processing (RTP). The results presented here mainly concern the epitaxial orientations and the morphology of beta-FeSi2 on silicon. The different epitaxial relationships are experimentally distinguished by the use of transmission electron diffraction (TED) and microscopy (TEM). Thick beta-FeSi2 layers (> 100 nm) have been selectively grown by RTP chemical vapor deposition on patterned (111) and (001) silicon wafers and under different experimental conditions. They are polycrystalline with large grains (about 1 mum) and mainly epitaxial. The main epitaxial relationship found is (220) beta-FeSi2 // (111) Si named type B in the literature. An important result is the flatness of the interface under each beta-FeSi2 grain which presents large areas (about 50 nm) without any monoatomic step. This result seems to be an advantage of the promising chemical vapor deposition process used which minimizes the interdiffusion processes at the interface.