Identification of Deep Levels Associated with Extended and Point Defects in GeSn Epitaxial Layers Using DLTs

Deep levels associated with extended and point defects in MOS capacitors fabricated on unintentionally doped GeSn epitaxial layers on Ge-on-Si substrates have been studied by Deep Level Transient Spectroscopy (DLTS). A 9nm layer of Al2O3 is deposited as high-k gate dielectric by Molecular Beam Epitaxy. The trap kinetics and origin of defect states is discussed. Also, it is shown that the dislocation cores in relaxed p-Ge are associated with band-like donor-like states in the lower half of forbidden band gap, and act as carrier trapping and recombination centers. In addition, slow and fast oxide interface traps are observed.