A review of recent advances in the spherical harmonics expansion method for semiconductor device simulation.

The Boltzmann transport equation is commonly considered to be the best semi-classical description of carrier transport in semiconductors, providing precise information about the distribution of carriers with respect to time (one dimension), location (three dimensions), and momentum (three dimensions). However, numerical solutions for the seven-dimensional carrier distribution functions are very demanding. The most common solution approach is the stochastic Monte Carlo method, because the gigabytes of memory requirements of deterministic direct solution approaches has not been available until recently. As a remedy, the higher accuracy provided by solutions of the Boltzmann transport equation is often exchanged for lower computational expense by using simpler models based on macroscopic quantities such as carrier density and mean carrier velocity. Recent developments for the deterministic spherical harmonics expansion method have reduced the computational cost for solving the Boltzmann transport equation, enabling the computation of carrier distribution functions even for spatially three-dimensional device simulations within minutes to hours. We summarize recent progress for the spherical harmonics expansion method and show that small currents, reasonable execution times, and rare events such as low-frequency noise, which are all hard or even impossible to simulate with the established Monte Carlo method, can be handled in a straight-forward manner. The applicability of the method for important practical applications is demonstrated for noise simulation, small-signal analysis, hot-carrier degradation, and avalanche breakdown.

[Frequency analytic EEG study on the topic of temporal function disorders in transsexuality]. / Frequenzanalytische EEG-Untersuchung zur Frage temporaler Funktionsstörungen bei Transsexualität.

A high rate of (temporal) EEG abnormalities within the group of transsexual patients has been previously described. These reports however were based on visual EEG analyses, which were not sufficiently statistically supported. It therefore seemed necessary to test this observations by utilizing quantitative frequency EEG analysis by using a larger group of transsexuals (n = 33). Fourier transformed data were recordings from T3-A1, T3-P3, T5-Cz, 01-Cz. The power of the delta-, theta-, alpha, and beta-bands were calculated as the percent of the total power (1,00-30,00 Hz). Different ratios of the absolute power values were computed. No significant differences of frequency-band related power, global power or power ratios between patients and normal subjects were found. There was also no separation on the basis of the genotypic sex of the subjects (Mann-Whitney-test). However 7 EEG's (21%) of the transsexual patients showed according to our interpretation temporo-parietal abnormalities.