nextnano3 is a simulation tool that aims at providing global insight into the basic physical properties of realistic three-dimensional mesoscopic semiconductor structures. It focuses on quantum mechanical properties such as the global electronic structure, optical properties, and the effects of electric and magnetic fields for virtually any geometry and combination of semiconducting materials. For the calculation of the carrier dynamics a drift--diffusion model based on a quantum-mechanically calculated density is employed. In this paper we present an overview of the capabilities of nextnano 3 and discuss some of the main equations that are implemented into the code. As examples, we first discuss the strain tensor components and the piezoelectric effect associated with a compressively strained InAs layer for different growth directions, secondly, we calculate self-consistently the quantum mechanical electron density of a Double Gate MOSFET, then we compare the intersubband transitions in a multi-quantum well structure that have been obtained with a single-band effective mass approach and with an 8-band k · p model, and finally, we calculate the energy spectrum of a structure in a uniform magnetic field.

Unipolar intersubband lasers like quantum cascade laser structures might be realized not only in III-V semiconductors but also in Si/SiGe multiple layer structures since no optical transitions across the indirect band gap are involved. We report on well-defined intersubband electroluminescence emission of Si/SiGe quantum cascade structures with different active quantum wells parameters. The complex valence band structure and a nonradiative relaxation rate of about 400 fs were calculated by multiband k•p formalism including Si/Ge segregation effects. The observed spectral shift of the electroluminescence peak from 146 to 159 meV is described well by quantum confinement of the two lowest heavy hole subbands. The electroluminescence observed reveals transverse magnetic polarization, a spectral line shape that changes with the direction of the current, and low-energy line broadening with an increase in temperature and current. All these features are described well by the k•p model calculation.

Electroluminescence from strain-compensated Si 0.2 Ge 0.8 / Si quantum-cascade structures based on a boundto-continuum transition Appl. Phys. Lett. 81, 4700 (2002); 10.1063/1.1528729 Theoretical investigation of intersubband hole transitions in Si/SiGe/Si quantum wells