Characterization of Si/Si_1-xGe_x/Si heterostructures by capacitance-transient spectroscopy

Deep level distributions have been investigated in B-doped Si/Si _1-xGe_x/Si layers grown by molecular beam epitaxy using deep level transient spectroscopy. Broadening in the deep level spectra is discussed in terms of carrier emission over a band of deep level energies as has been considered for both alloy disorder and dislocations. The distortion observed in the deep level spectra in the vicinity of the upper Si/Si _1-xGe_x heterojunction is suggested to be a consequence of the significant band bending that occurs in this region; the possible causes for this distortion are discussed. The deep states exhibit donor-like behavior and the origin of the electrical activity is considered to lie with metal point-defect/dislocation interactions.