H 2 S exposure of a (100)Ge surface: Evidences for a (2×1) electrically passivated surface

Abstract

The experimental study of the bonding geometry of a (100)Ge surface exposed to H2S in the gas phase at 330°C shows that 1 ML S coverage with (2×1) surface reconstruction can be achieved. The amount of S on the Ge surface and the observed surface periodicity can be explained by the formation of disulfide bridges between Ge–Ge dimers on the surface. First-principles molecular dynamics simulations confirm the preserved (2×1) reconstruction after dissociative adsorption of H2S molecules on a (100)Ge (2×1) surface, and predict the formation of (S–H)–(S–H) inter-Ge dimer bridges, i.e., disulfide bridges interacting via hydrogen bonding. The computed energy band gap of this atomic configuration is shown to be free of surface states, a very important finding for the potential application of Ge in future high performance integrated circuits.

Si passivation for Ge pMOSFETs: Impact of Si cap growth conditions

“…For pMOSFETs, germanium is identified as a particular good candidate [2] and many passivation routes have been proposed by introducing different Ge-high K interlayers: GeO 2 [3], GeON [4], S [5], Sr [6] and ultrathin Si cap [7][8][9]. The latter passivation scheme permits to introduce Si back into Ge MOSFET processing as a well-known starting surface for high K-metal gate stack deposition.…”

Impurity diffusion, point defect engineering, and surface/interface passivation in germanium

“…For this reason, researchers continue to look for alternative passivation schemes. Sulfur passivation [73,74] combined with Al 2 O 3 [75,76] is an attractive solution since it provides good passivation for both Ge and InGaAs surfaces [76] and therefore makes it a prospective candidate for a common passivation/gate dielectric scheme in dual channel CMOS.…”

Nature of chemical states of sulfur embedded in atomic-layer-deposited HfO2film on Ge substrate for interface passivation

“…Recently, it has been reported that passivation of the defects by injecting sulfur ions into Ge, is effective in improving the electrical properties . Along with a conventional wet process in which the Ge substrate is immersed in aqueous (NH 4 ) 2 S, a dry process in which the Ge substrate is exposed to H 2 S gas environment with heat, is newly developed . The S ions injected by these methods have been simply regarded as to fill the defects by occupying the oxygen sites or form Ge–S bonding at the interface.…”

“…The S ions injected by these methods have been simply regarded as to fill the defects by occupying the oxygen sites or form Ge–S bonding at the interface. In both cases, the S ions should have valence of –2 similar to O ions . However, the S ions incorporated in the high‐ k GI layers can, in principle, be further oxidized due to abundance of oxygen ions .…”

“…In spite of the possible oxidation of sulfur, as far as we know, studies on the oxidation states of sulfur have not been reported. This is mainly because the concentration of sulfur embedded in the high‐ k /Ge system, would be too low (&1%) to be observable in conventional chemical analysis techniques such as X‐ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy .…”