Low Temperature Epitaxy of In Situ GaDoped Si_1-XGe_x: Dopant Incorporation, Structural and Electrical Properties

Abstract

The effect of the growth temperature and the Ga precursor flow on the epitaxy of Si1-xGex:Ga is studied. These parameters are found to have a significant impact on the Ga surface segregation behavior. In particular, Ga in situ doping impacts the growth rate of the epilayer, the Si1-xGex alloy composition, and the onset of strain relaxation. The growth temperature can be used to modulate the Ga segregation, enabling the deposition of materials with enhanced dopant concentrations and improved electrical properties. The Ga local atomic environment was studied in both a Si0.4Ge0.6:Ga and a Ge:Ga sample by X-ray absorption fine structure. The local environment of the Ga determined confirmed that the majority of dopants occupy a substitutional position within the lattice.

Low temperature selective growth of Ga-doped and Ga–B co-doped germanium source/drain for PMOS devices

“…Ga incorporation is delayed and takes off after a Ge thickness of 5-7 nm. As discussed in 9,32) Ga indeed first accumulates at the sample surface before it starts incorporating in the growing layer. The surface is then partly occupied, which apparently decreases the B incorporation efficiency.…”

“…This is supported by Xray absorption fine structure measurements, performed on similar samples and combined with density functional theory analysis, reported in. 32) Those indeed indicated that the majority of the Ga impurities were occupying substitutional sites in the Ge matrix. Full activation of the dopants can, however, not be confirmed due to a lack of literature reports on HSF values for high doping levels.…”