Observation of strain relaxation in Si1-xGex layers by optical and electrical characterisation of a Schottky junction

Turan R., Aslan B., Nur O., Yousif M., Willander M.

APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, vol.72, no.5, pp.587-593, 2001 (SCI-Expanded) identifier identifier


We have studied the effect of the strain relaxation on the band-edge alignments in a Pt/p-Si1-xGex Schottky junction with x = 0.14 by internal photoemission spectroscopy and current-voltage measurements. We have shown that the variations in the band-edge alignments can be observed directly by measuring the optical and electrical properties of a simple Schottky junction. The strain in the Si1-xGex layer has been partially relaxed by thermal treatments at two different temperatures, The degree of relaxation and other structural changes have been determined by a high-resolution X-ray diffractometer. Both optical and electrical techniques have shown that the barrier height of the Pt/Si0.86Ge0.14 junction increases with the amount of relaxation in the Si1-xGex layer. This shows that the valence-band edge of the Si1-xGex layer moves away from the Fermi level of the Pt/Si1-xGex junction. The band-edge movement results from the increase in the band gap of the Si1-xGex layer after the strain relaxation. This result agrees with the theoretical predictions for the strain-induced effects on the Si1-xGex band structure.