First-principles calculation of the temperature dependence of the optical response of bulk GaAs

A novel approach has been developed to calculate the temperature dependence of the optical response of a semiconductor. The dielectric function is averaged over several thermally perturbed configurations that are extracted from molecular dynamic simulations. The calculated temperature dependence of the imaginary part of the dielectric function of GaAs is presented in the range from 0 to 700 K. This approach that explicitly takes into account lattice vibrations describes well the observed thermally-induced energy shifts and broadening of the dielectric function.Comment: 6 pages, 3 figure

Prozesskontrolle in der MOVPE mittels optischer in-situ-Analytik Abschlussbericht

The aim of the research work was the application of the spectroscopic methods Reflection-Anisotropy-Spectroscopy (RAS) an Ellipsometry (SE) for process control during growth of III-V-semiconductors by metalorganic vapour phase epitaxy (MOVPE). Sentech Instruments GmbH in cooperation with TU Berlin designed and built a demonstrator set-up of a robust and compact RAS-system. Meanwhile, this instrument was placed on the market as a new product (RAS 50). This set-up was successfully used at FBH for studies of process details like switching sequences and for on-line monitoring during production of device structures (LEDs und HBTs) by MOVPE. Further improvement of this RAS-set-up by TU Berlin for the first time made fully spectrally resolved RAS monitoring possible in a real production enviroment (wafer rotation). For the example of HBT layer structures it was shown that the reproducibility of the growth process can be assessed and deviations from the target process can be detected. Thus, control of the growth process was achieved. Real-time regulation of growth parameters for the correction of a deviation was demonstrated on the examples of lattice-matched growth of InGaAs on InP and InGaP on GaAs. The research work resulted in 41 scientific publications and 4 patents. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(65,29) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman