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 the strained Si/SiGe material system. 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 book Analysis and Simulation of Heterostructure Devices by Palankovski and Quay in the Springer-Verlag series on Computational Microelectronics.