Technology
computer-aided design (TCAD) methodologies are extensively used in
development and production. Several questions during device
fabrication, such as performance optimization and process control, can
be addressed by simulation. The choice of a given simulation tool or a
combination of tools depends to a large extent on the complexity of the
particular task, on the desired accuracy of the problem solution, and
on the available human, computer, and time resources.
Optimization of geometry, doping, materials, and material compositions
targets high output power, high breakdown voltage, high speed, low
leakage, low noise, and low power consumption. This is a challenging
task that can be significantly supported by device simulation. While DC
simulation is sufficient for optimization of breakdown voltages,
turn-on voltages, or leakage currents, AC simulation is required for
speed, noise, and power issues.
There are several challenges which are specific for modeling and
simulation of heterostructure devices. The characterization of the
physical properties of SiGe and III-V compounds is required for wide
ranges of material compositions, temperatures, doping concentrations,
etc. Physics-based analytical models for the lattice, thermal,
band-structure, and transport properties of various semiconductor
materials, as well as models for important high-field and high-doping
effects taking place in the devices, are derived and implemented in the
three-dimensional device simulator Minimos-NT.
Special attention is paid to modeling of the properties of SiGe with
respect to material composition and strain due to lattice mismatch.
Another interesting aspect is the modeling of novel materials and
devices. For example, the GaSb or the GaN material systems enable
advanced devices such as InP/GaAsSb/InP or AlGaAs/InGaAsN/GaAs
heterojunction bipolar transistors.
Heterojunction bipolar transistors (HBTs) and high electron mobility
transistors (HEMTs) are among the most advanced high-frequency devices.
The most recent achievements in numerical simulation for industrial
heterostructure devices, together with relevant applications (GaAs,
InP, and SiGe HBTs; GaAs-, InP-, and GaN-based HEMTs) are presented in
the new book Analysis and Simulation
of Heterostructure Devices by
Palankovski and Quay in the Springer-Verlag series on Computational
Microelectronics.
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