27-10-2012, 11:58 AM
High Electron Mobility SiGe/Si Transistor Structures on Sapphire Substrates
ABSTRACT
SiGe/Si n-type modulation doped field effect structures and transistors (n-MODFETs) have been fabricated on r-plane
sapphire substrates. The structures were deposited using molecular beam epitaxy, and antimony dopants were incorporated via
a delta doping process. Secondary ion mass spectroscopy (SIMS) indicates that the peak antimony concentration was
approximately 4 x 10(exp 19) per cubic centimeter. At these two temperatures, the electron carrier densities were 1.6 and 1.33
x 10(exp 12) per square centimeter, thus demonstrating that carrier confinement was excellent. Shubnikov-de Haas oscillations
were observed at 0.25 K, thus confirming the two-dimensional nature of the carriers. Transistors, with gate lengths varying
from 1 micron to 5 microns, were fabricated using these structures and dc characterization was performed at room temperature.
The saturated drain current region extended over a wide source-to-drain voltage (V (sub DS)) range, with V (sub DS) knee
voltages of approximately 0.5 V and increased leakage starting at voltages slightly higher than 4 V.
ABSTRACT
SiGe/Si n-type modulation doped field effect structures and transistors (n-MODFETs) have been fabricated on r-plane
sapphire substrates. The structures were deposited using molecular beam epitaxy, and antimony dopants were incorporated via
a delta doping process. Secondary ion mass spectroscopy (SIMS) indicates that the peak antimony concentration was
approximately 4 x 10(exp 19) per cubic centimeter. At these two temperatures, the electron carrier densities were 1.6 and 1.33
x 10(exp 12) per square centimeter, thus demonstrating that carrier confinement was excellent. Shubnikov-de Haas oscillations
were observed at 0.25 K, thus confirming the two-dimensional nature of the carriers. Transistors, with gate lengths varying
from 1 micron to 5 microns, were fabricated using these structures and dc characterization was performed at room temperature.
The saturated drain current region extended over a wide source-to-drain voltage (V (sub DS)) range, with V (sub DS) knee
voltages of approximately 0.5 V and increased leakage starting at voltages slightly higher than 4 V.