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Recently, the progress of SiGe molecular beam epitaxy (MBE)
growth technique has made possible grow high quality
superlattice and highly doped films which can improve largely
the of the high speed devices (such as High Electron Mobility
(HEMT) and Modulation Doped Field Effect Transistors Moreover,
SiGe-based technology is compatible with nowadays -based-very-
large-scale-integration (VLSI) technology. A lot of interest
has been focused on Si/GexSi1-x heterostructure devices. SiGe
related devices with ultra high carriers mobility, high
transconductance and high speed performance of field-effect
transistors have been successful fabricated. In this thesis,
the growth and fabrication of boron δ-doped and modulation-
doped field-effect transistors are reported. The properties of
Si/GexSi1-x heterojunction and the fundamental of δ-doping and
modulation-doping will be introduced first. Fim
characterization by using Secondary Ion Mass Spectrometry
(SIMS) analysis, Transmission Electron Microscopy (TEM)
observation, and Hall measurements are presented and analyzed.
The current-voltage characteristics of fabricated devices at
300 K and 77 K will be analyzed and discussed in detail. The δ-
doped Ge0.2Si0.8 MESFET with a gate length of 5 um exhibits an
extrinsic transconductance of 11.2 mS/mm and a high gate to
source breakdown voltage > 16 V. sheet carrier density and hole
mobility of the delta layer were to be 5*10^13 cm-2 and 35 cm2
V-1s-1 at 300 K, respectively. the δ-doped symmetric Si/Ge0.4
Si0.6/Si quantum welld MESFET exhibits an extrinsic
transconductance of 1.7 mS/mm. The mobility was found to be 106
and 2680 cm2V-1s-1 at 300 K and 77 respectively.
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