Epitaxial orientation of β-FeSi2/Si heterojunctions obtained by RTP chemical vapor deposition

Abstract

In recent years the semiconducting phase of iron silicide 03B2-FeSi2 has attracted interest. Promising applications of a great deal of 03B2-FeSi2/Si heterojunctions are reported in semiconductor technology due to the 0.89 eV direct band gap of 03B2-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 03B2-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 03B2-FeSi2 using Rapid Thermal Processing (RTP). The results presented here mainly concern the epitaxial orientations and the morphology of 03B2-FeSi2 on silicon. The different epitaxial relationships are experimentally distinguished by the use of transmission electron diffraction (TED) and microscopy (TEM). Thick 03B2-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 03BCm) and mainly epitaxial. The main epitaxial relationship found is (220) 03B2-FeSi2 // (111) Si named type B in the literature. An important result is the flatness of the interface under each 03B2-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.