A large project (START) on the "Simulation of Advanced Semiconductor Devices"
funded by the Austrian Federal Ministry for Science and Research (BMWF) through
the Austrian Science Fund (FWF) has entered its fourth year.
The project includes several research topics, such as the modeling of novel
semiconductors (strained Si/SiGe, various III-Vs, as well as the Group IV-VI
material systems). The device applications include advanced high-frequency
high-power Heterojunction Bipolar Transistors (HBTs) and High
Electron Mobility Transistors (HEMTs), as well as quantum wires and
high-efficiency solar cells.
The physical material properties are characterized for wide ranges of material
compositions, temperatures, doping concentrations, etc. by means of a Monte Carlo (MC)
simulation. A new 2D Ensemble Monte Carlo code was developed and verified
versus a bulk MC code for different materials. It is being used as a platform for
the development of a 2D Wigner quantum MC code.
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 device simulator Minimos-NT. The models are
calibrated against experimental data from our scientific partners. Novel device
structures are investigated, designed, and optimized.
For example, a recent work on "Negative differential mobility at ultrahigh
fields: comparison between an experiment and simulations" (APL 92, 062114,
2008) explains that the superfast switching observed in GaAs bipolar
transistors should take place only with a strong negative differential electron
mobility up to an electric field of 600 kV/cm. A satisfactory velocity-field
dependence is predicted only by our 3-valley MC simulations.
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