Si/SiGe n-type inverted modulation doping using ion implantation

We studied the density of two-dimensional electron gas (2DEG) in Si∕SiGe heterostructures as a function of the distance between the substrate-epilayer interface and the 2DEG layer. The 2DEG sheet density was observed to change from 2.2×1011to3.5×1011cm−2. Theoretical simulations are shown to be consistent with the experimental results within experimental errors. The slight deviations of the experimental results possibly come from temperature variation of the Sb dopant source during the growth of the Sb doping layer.

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Monolayer doping of silicon-germanium alloys: A balancing act between phosphorus incorporation and strain relaxation

Kennedy

Duffy²,

Mirabelli³

et al. 2019

Journal of Applied Physics

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This paper presents the application of monolayer doping (MLD) to silicon-germanium (SiGe). This study was carried out for phosphorus dopants on wafers of epitaxially grown thin films of strained SiGe on silicon with varying concentrations of Ge (18%, 30%, and 60%). The challenge presented here is achieving dopant incorporation while minimizing strain relaxation. The impact of high temperature annealing on the formation of defects due to strain relaxation of these layers was qualitatively monitored by cross-sectional transmission electron microscopy and atomic force microscopy prior to choosing an anneal temperature for the MLD drive-in. Though the bulk SiGe wafers provided are stated to have 18%, 30%, and 60% Ge in the epitaxial SiGe layers, it does not necessarily mean that the surface stoichiometry is the same, and this may impact the reaction conditions. X-ray photoelectron spectroscopy (XPS) and angle-resolved XPS were carried out to compare the bulk and surface stoichiometry of SiGe to allow tailoring of the reaction conditions for chemical functionalization. Finally, dopant profiling was carried out by secondary ion mass spectrometry to determine the impurity concentrations achieved by MLD. It is evident from the results that phosphorus incorporation decreases for increasing mole fraction of Ge, when the rapid thermal annealing temperature is a fixed amount below the melting temperature of each alloy.

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Si/SiGe n-type inverted modulation doping using ion implantation

Cited by 3 publications

References 14 publications

Low-dimensional inverted Si/SiGe modulation-doped electron gases using selective ex-situ ion implantation

Low-dimensional inverted Si/SiGe modulation-doped electron gases using selective ex-situ ion implantation

The proximity effect of the regrowth interface on two-dimensional electron density in strained Si

Monolayer doping of silicon-germanium alloys: A balancing act between phosphorus incorporation and strain relaxation

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