Characterization and device applications of silicon-germanium and compound semiconductor-based heterostructures.

摘要

The objective of this work is to provide an understanding of the growth and structural characteristics of Si_1−xGe _x and compound semiconductor-based heterostructures for electronic and optoelectronic device applications. Particular emphasis is placed on achieving defect-free growth of both relaxed and strained mismatched epitaxy. Several techniques for obtaining defect-free Si_1−xGe_x/Si epitaxy grown on Si are investigated, including the use of superlattice and graded buffer layer structures. A detailed description of the LT-Si buffer defect reduction mechanism, identified in the course of this work, will I then be provided. This work is the first comprehensive study of the LT-Si buffer layer defect reduction mechanism. This is also the first LT-Si study utilizing three different growth systems: gas source molecular beam epitaxy (MBE), solid source MBE, a id ultra high-vacuum chemical vapor deposition (UHV-CVD). Dislocation densities as low as 104 cm−2 have been achieved in Si_1−xGe_x/Si samples grown by GSMBE. The thickness of defect-free Si_1−xGe _x epitaxy is comparable to that grown by SSMBE at the same Ge composition. Both mesa and ridge waveguide photodiodes with relaxed Si_0.6Ge _0.4 absorption region using LT-Si buffer layers have demonstrated optical responses near 1.3 μm wavelength. Also, n-channel strained Si MOSFETs grown on relaxed Si_0.8Ge_0.2 layers have achieved higher transconductance and mobilities than conventional Si MOSFETs. The structural characteristics of ln(Ga)As/GaAs self-assembled quantum dots are then examined. Several growth techniques are presented to improve the spectral response of the dots, including buried stressor dots and cycled submonolayer deposition. Growth and properties of GaAs on Si substrates are reported as well. Several methods for minimizing defects in GaAs grown on Si are discussed. Finally, electroluminescent characteristics of In_xGa_1−xAs self-organized quantum dot lasers grown on Si will be provided.