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Varying Ge composition up to 57% and p+ tunnel-junction (source) doping concentration are employed to analyze strained pseudomorphic Si/[Si.sub.1-x][Ge.sub.x]/Si gate-controlled band-to-band tunneling (BTBT) devices. The results showed that the switching characteristics of TFETs could be significantly improved by controlling the strained-SiGe bandgap of 0.55 eV.

The mechanism responsible for the dependence of hole mobility on SiGe channel layer thickness is investigated for channel thickness of 1.8nm. Due to the combination of phonon and interface scattering the mobility is found to degrade for channel thickness below 4nm and for SiGe films of channel thickness greater than 2.8nm the scattering is not very significant.

The fabrication and analysis of n- and p-MOSFETs in novel ultrathin-body (UTB) strained semiconductor heterostructure-on-insulator (HOI), achieved by epitaxial growth, bonding and transfer of strained layers, is described. Increased OFF-state leakage currents are seen in HOI compared to strained Si directly on insulator (SSDOI) and unstrained silicon-on-insulator (SOI) and for a 4-nm-thick buried SiGe layer, leakage is reduced relative to devices with thicker SiGe channels.

Study was conducted to investigate the impact of processing factors such as ion implantation and rapid thermal annealing on mobility enhancement in strained-Si n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs). Electron mobility enhancement is presented to degrade considerably when the implant dose is above a certain critical dose for a given annealing condition.

A physically based analytic model for the threshold voltage Vt of long-channel strained-Si-Si1-(sub x)Ge(sub x) n-MOSFETs is given and confirmed with the help of numerical simulations for a wide range of channel doping concentration, gate-oxide thickness, and strained-Si layer thicknesses. The threshold voltage difference between strained- and unstrained-Si devices increases with channel doping but as such the increase is mitigated by gate oxide thickness reduction.

The study stated that Hole mobility is characterized in P-MOSFETs with a layered substrate consisting of tensile strained Si cap on a compressively strained Si (sub 0.4) Ge (sub 0.6) buried layer grown pseudomorphically to a relaxed. The analysis also founded that mobility is a function of inversion carrier density, measured mobility curves can be matched consistently with a single set of mobility-carrier-density relationship.

The impact of heavy doping and reduced density of states in Si1(sub -y)C(sub y) compared to Si on the extraction of the energy band offset, and on the collector current of p-n-p HBTs. A guide to further investigation of HBT designs aspects in the Si/Si1(sub -y)C(sub y) material system is provided by the study.

Conventional admittance spectroscopy is based on the measurement of pn junction admittance or Schottsky diodes made on a substrate. The principle of admittance spectroscopy is applied for the first time ever to the measurement of MOS capacitors manufactured on Si/Si sub 1-xGe sub x/Si double heterostructures. The method was verified through experimentation. A new feature of this MOS capacitor measurement method is that two hetero-interfaces of a double heterostructure can be evaluated separately by controlling the gate voltage.

Deep submicron strained-Si n-MOSFET's fabrication was undertaken on strained Si/relaxed Si0.8Ge0.2 heterostructures.

Strained pseudomorphic Si/Si1-xGex/Si gate-controlled band-to-band tunneling (BTBT) devices have been analyzed with varying Ge composition up to 57% and p+ tunnel-junction (source) doping concentration in the 1019-1020 cm-3 range. Measurements show the impact of these parameters on the transfer and output characteristics. Measurements are compared to simulations using a nonlocal BTBT model to analyze the mechanisms of device operation and to understand the impact of these parameters on the device switching behavior. The measured characteristics are consistent with simulation analysis that shows a reduction in energy barrier for tunneling (Egeff) and a reduction in tunneling distance with increasing Ge composition and source doping concentration. Increases in the pseudomorphic layer Ge content and doping concentration of the tunnel junction produce large improvements in the measured switching-behavior characteristics (Ion, slope, turn-on voltages, and sharpness of turn-on as a function of Vds). Simulations are also performed to project the potential performance of more optimized structures that may be suitable for extremely low power applications (Vdd < 0.4 V). [ABSTRACT FROM AUTHOR]

p-Si/n-Si[sub 1 - y]C[sub y]/p-Si heterojunction bipolar transistors with varying carbon fractions in the base were grown by rapid thermal chemical vapor deposition (RTCVD), to better understand the potential of Si[sub 1 - y]C[sub y] in enhancing the performance of Si-based bipolar technology. The band line-up issues which make Si[sub 1 - y]C[sub y] a desirable choice for forming the base region in a p-n-p HBT are discussed. Electrical measurements performed on the p-Si/n-Si[sub 1 - y]C[sub y]/p-Si HBTs (y = 0.6, 0.8 at.%) are used to extract important information regarding the electronic properties of the Si/Si[sub 1 - y]C[sub y] material system, e.g., thc bandgap reduction in Si[sub 1 - y]C[sub y] compared to Si and minority carrier recombination lifetime in Si[sub 1 - y]C[sub y]. Temperature dependent measurements of the collector current were performed to extract the bandgap narrowing at the Si/Si[sub 1 - y]C[sub y] heterojunction. This paper includes a detailed analysis of the impact of heavy doping and reduced density of states in Si[sub 1 - y]C[sub y] compared to Si on the extraction of the energy bandgap offset, and on the collector current of p-n-p HBTs. The impact of the reduced density of states on the design of p-n-p Si/Si[sub 1 - y]C[sub y] HBTs is discussed. The measured value of the energy band offset is (65 meV/at.% C) very close to previously measured values of the conduction band offset at the Si/Si[sub 1 - y]C[sub y] heterojunction. The results are thus consistent with a band line-up at the Si/Si[sub 1 - y]C[sub y] interface that is dominated by a conduction band offset with little if any valence band offset. [ABSTRACT FROM AUTHOR]