nextnano GmbH based in München/Germany, is a spin-off from the Walter Schottky Institute of the Technische Universität München (former Chair for Theoretical Semiconductor Physics, emeritus Prof. Peter Vogl). It was founded in 2012 to develop and commercialize software for the simulation of electronic and optoelectronic semiconductor nanodevices, including software for quantum cascade lasers. The vision of nextnano GmbH is to establish the nextnano software as the de facto standard simulator for the next generation of electronic and optoelectronic semiconductor nanodevices. In particular, it wants to become the leading provider of software for quantum cascade lasers. The (non-QCL) software is used by more than 250 customers and in more than 35 countries. To date, the company has 9 employees.
Role in FLASH
NEXTNANO brings state-of-the-art modelling capability that complements the device design and growth activities in WP3 and WP5. The experimental program will be underpinned by this capability. NEXTNANO will
- Perform quantum transport and gain calculations of SiGe THz QCLs using the nonequilibrium Green’s function method (NEGF);
- Provide software tool for calculation of strain, energy levels and wave functions in SiGe QCLs including training for other participants;
- Compare simulations to experimental results, and to results of simulations performed with the tools of the other project partners;
- Optimize QCL parameters with respect to device performance (e.g. quantum well and barrier widths, barrier heights, material parameters, doping concentration/profile, alloy scattering).
The Nonequilibrium Green's Function method
"Room temperature operation of n-type Ge/SiGe terahertz quantum cascade lasers predicted by non-equilibrium Green’s functions"
n-type Ge/SiGe terahertz quantum cascade laser are investigated using non-equilibrium Green’s functions calculations. We compare the temperature dependence of the terahertz gain properties with an equivalent GaAs/AlGaAs QCL design. In the Ge/SiGe case, the gain is found to be much more robust to temperature increase, enabling operation up to room temperature. The better temperature robustness with respect to III-V is attributed to the much weaker interaction with optical phonons. The effect of lower interface quality is investigated and can be partly overcome by engineering smoother quantum confinement.
T. Grange, D. Stark, G. Scalari, J. Faist, L. Persichetti, L. Di Gaspare, M. De Seta, M. Ortolani, D. J. Paul, G. Capellini, S. Birner, M. Virgilio
Applied Physics Letters 114, 111102 (2019)
Pre-print available open access https://arxiv.org/pdf/1811.12879.pdf.