A novel Si (silicon)-based double-barrier structure (DBS) is newly proposed to study Si resonant tunneling devices. To form a thin Si single-crystal plate as a quantum well, anisotropic wet chemical etching and thermal oxidation are adopted. The DBS has a 43 nm-wide Si quantum well and 2.3 nm-thick SiO2 barriers. The electrical characteristic exhibits negative differential conductance (NDC).
We have demonstrated the low-V
BE operation of SiGeC heterojunction bipolar transistors by introducing a novel device design concept using the SiGe cap structure and high Ge- (up to 25%) and C- (up to 0.8%) content base. We successfully controlled the base current by designing the SiGe cap structure and C content, which enabled us to obtain suitable values of h
FE and B
V
CEO, while maintaining a high collector current and high-frequency performance. We clarified that the recombination around the emitter-base junction is enhanced by introducing the SiGe cap structure and high C content, which contribute to the increase of the base current.
The incorporation of C into Si1-x
Ge
x
alloys contributes to enlarging the critical layer thickness and to improving the thermal budget. It also realizes a narrower bandgap with compensated strain. These effects would introduce good performance at high frequency in the devices. We fabricate heterojunction bipolar transistors (HBTs) with an Si1-x-y
Ge
x
C
y
base layer using ultrahigh-vacuum chemical vapor deposition (UHV-CVD) technology. The bandgaps of Si1-x-y
Ge
x
C
y
base layers are measured by the evaluation of the collector current dependence on temperature. The strain of the pseudomorphic Si1-x-y
Ge
x
C
y
layer is also extracted by an analysis of the X-ray diffraction spectra. Good flexibility of Si1-x-y
Ge
x
C
y
alloy is shown for the bandgap and strain engineering. The devices using the excellent characteristics of Si1-x-y
Ge
x
C
y
alloy have numerous applications for wireless telecommunications.
A novel fabrication method of silicon quantum wire Gate-All-Around Iransistor (GAAT), in which the gate oxide and the gate electrode are wrapped around the ultra fine silicon quantum wire, has been proposed. In order to verify one-dimensional (1D) subbands effects, we have studied quantum transport in Si quantum wire GAAT with a width of 50nm at low temperatures in zero-magnetic field and in fields up to 10T. Electrical population of lD subbands and magnetic depopulation of lD subbands are clearly observed.
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