Direct assessment of relaxation and defect propagation in different thin single Ge/Si and step-graded Si1-x/Si buffer layers for RF and microwave applications

We have used the direct and strain sensitive double crystal and multi-crystal high resolution x-ray diffraction to perform double crystal rocking curves (DC-HRRC) and triple axis high resolution 2-D reciprocal space mapping (2D-RSIM) respectively, as the main tool to assess the relaxation and defect propagation in Ge and Si_1-x relaxed buffers layers grown on Si (001) substrates. The present study represents one of the first studies regarding the direct extraction and assessment of relaxation parameters and defect propagation in relaxed buffer layers having top pure Ge fully relaxed layer. This technique allows the direct and accurate determination of the mismatches of the lattice parameters parallel and perpendicular to growth directions with an accuracy of 10^-5. The investigated heterostructures include Ge/Si single epitaxial relaxed buffer layer (SE-RBL) and step graded multi layer Si_1-x/Si relaxed buffer layer (SG-RBL) with Ge fractions of x=0.15, 0.44 and final pure Ge top layer. Moreover, the effect of post processing annealing is investigated for different temperature time cycles for some of these structures. The unique thin total grown thickness (maximum of 6 μm) actually enables the use of the high resolution X-ray diffraction