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.