Deep-Level Transient Spectroscopy of MOS Capacitors on GeSn Epitaxial Layers

摘要

Deep levels present in MOS capacitors, fabricated on GeSn epitaxial layers on Ge-on-Si substrates have been studied by Deep-Level Transient Spectroscopy (DLTS). The gate dielectric is composed of 9 nm Al_2O_3 deposited by Molecular Beam Epitaxy (MBE) on two different types of Interfacial Oxide Layers (IOL). It is shown that the density of interface traps (D_(it)) near the valence band edge is significantly reduced for GeSn epilayers compared with the same gate stack on a Ge cap. At the same time, several deep-level traps in the germanium depletion region have been observed, whereof the origin is discussed.