Impact of the Ge Content on the Bandgap-Narrowing Induced Leakage Current of Recessed $\hbox {Si}_{1 - x}\hbox {Ge}_{x}$ Source/Drain Junctions

The purpose of this paper is to evaluate the impact of process-induced stress on the generation current of fully strained Si_1- xGex source/drain junctions. The Ge content of the compressively strained SiGe epitaxial layer plays a key role in the tensile stress levels present in the underlying Si substrate. Current-voltage (I-V) measurements were employed to further investigate the leakage current enhancement due to the stress-induced bandgap narrowing in the Si depletion region, when no extended defects are formed. An empirical approach is proposed to describe the Ge content dependence of the bandgap-shrinkage-induced leakage current. An increase of the intrinsic carrier concentration as a function of the stress mismatch is observed. Moreover, the role of the epilayer thickness in the generation current is also discussed.