Electrical and structural characterization of PtSi/p-Si1−xGex low Schottky barrier junctions prepared by co-sputtering

Abstract

Schottky barrier junctions of PtSi/Si1−xGex were produced; the silicide was deposited by co-sputtering on defect-free well-calibrated strained-Si1−xGex (0⩽x⩽0.242) layers. This work is motivated by the fact that it is very difficult to control the formation of well-defined and well-controlled PtSi/Si1−xGex junctions by reacting Pt/Si1−xGex or by using a silicon cap layer. The Schottky barrier heights of these junctions were substantially lower than those of PtSi/Si junctions. Different characterization tools were employed for structural characterization. High-resolution multicrystal x-ray diffraction (HR-MCXRD) was used to investigate the sample quality and strain state of the molecular beam epitaxy (MBE) grown Si1−xGex layers and to accurately determine the Ge fraction in the fabricated junctions. Cross-sectional transmission electron microscopy (XTEM) was applied to investigate the interface roughness. The possible interlayer diffusion was investigated by secondary ion mass spectrometry (SIMS). The variation of the barrier height of the junctions with the Ge fraction x was studied, and it was found to follow the same change as the band gap of strained-Si1−xGex. Also, and for comparison, Pt/p-Si1−xGex junctions were produced, and the effect of annealing on electrical characteristics was investigated.