Profiles of the optical absorption constant and interface composition in epitaxial silicon films.

The optical quality of epitaxial silicon films grown on sapphire by chemical vapour deposition was investigated as a function of film thickness by spectral reflectance measurements. Under optimum deposition conditions for epitaxy the film quality approaches the bulk value for thicknesses in excess of 0.3 μm. In-depth profiling by means of SIMS supported the idea of aluminium silicate interface layer formation between the sapphire substrate and the silicon film. Diffusion of aluminium into the silicon was also detected

Unexpectedly high energy photoluminescence of highly Si doped GaAs grown by MOVPE.

Epitaxial GaAs films highly doped with silicon were grown by the MOVPE method in the TMGa-AsH3-SiH4-H2 system. The films were investigated by Hall measurements, photoluminescence (PL) studies and SIMS. A linear relationship between the silane mole fraction in the gas phase and the incorporated Si in the epitaxial films was established by SIMS measurements. The Si concentrations of the samples investigated range from 3×1018 to 1×1020 atoms/cm3, whereas the corresponding Hall concentrations are in the range from 2×1018 to 5.5×1018 cm-3. They show a linear increase for the lower Si concentrations and then turn to a decrease for higher Si concentrations. The Hall mobilities decrease with increasing Si mole fraction (2320 to 760 cm2/V · s, 300 K). The intensities of the near band gap PL are markedly higher and the emission is shifted to higher energies by up to 60 meV as compared to melt- or solution-grown n-GaAs of the same concentration range. It appears that among the different growth techniques the MOVPE process gives highly doped n-type GaAs:Si samples which are more close to perfection

Neue Quellen fuer die Gasphasenepitaxie. Schichtstrukturen fuer Emitter. Teilvorhaben: Untersuchungen zur Eignung neuartiger Gruppe V-Chemikalien fuer die Herstellung von III-V-Halbleiter-Emitter-Schichtfolgen mittels metallorganischer Depositionssysteme Abschlussbericht

The activities were performed in close cooperation with partners from the universities of Leipzig (01BM411/1), Ulm (01BM412/2) and Marburg (01BM408/0). The main objective was to replace the highly toxic hydrides arsine and phosphine used today in MOVPE/MOMBE standard processes by new precursors with reduced toxicity and improved decomposition characteristics. As demonstrators lasers, LEDs and GaAs Hall sensor structures were chosen for the device oriented proove. The main contribution of Siemens was the investigation of MOMBE and MOVPE growth of GaInAsP/InP DH laser structures and MOVPE test structures for short wavelength AlGaInP/GaAs LEDs. Emitter structures based on the design given by Siemens were grown by the partners by MOMBE and/or MOVPE in the 1300-1500 nm and 610-670 nm wavelength range, respectively. These layer structures were evaluated and used for the preparation of devices, which were compared with reference structures grown by standard hybride processes at Siemens. With MOMBE 1.55 #mu#m laserstructures using the material combinations AsH_3/PH_3, TBAs/TBP and DTBAs/DTBP (tertiaery and ditertiaerybutyl arsine/-phosphine) were grown. The threshold current densities of test lasers (400 x 50 #mu#m_2) were comparable with results derived from those of the MOVPE AsH_3/PH_3 standard process (1.8-2.2 kAcm"-"2). Similar results were attained for MOVPE grown laser structures. Besides AsH_3/PH_3 the material combinations DETBAs (diethyltertiaerbutylarsine)/PH_3 and DETBAs (DTBAs, TBAs)/TBP were used for growth. For purity and availability reasons TBAs/TBP were selected to be particularly suitable. MCRW DH laser structures were grown and used for the preparation of small stripe lasers (350 x 2 #mu#m"2). The results obtained were nearly as good as those derived from laserstructures grown by the standard process. Beyond the original objective of the project, 2- SCH MQW MCRW laser structures were grown at Siemens using a complete TBAs/TBP process. The results gained from these lasers were adequate to best values of lasers from the hydride process (operation temperature up to 100 C). Therefore, these new precursors are fully compatible to AsH_3/PH_3 for the production of long wavelength lasers and GaAs Hall sensors. This increases their acceptance in industry considerably (transfer into production in preparation). In contrast, for short wavelength Al-containing material systems new sources of sufficient purity were not available until the immediate end of the project. That is why an urgent demand for further research and development is still required until the replacement of the hydrides for these materials can take place in industry. (orig.)SIGLEAvailable from TIB Hannover: F98B1752+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Photonik - Material und Technologien. Teilvorhaben: Integration photonischer Bauelementstrukturen mittels MOMBE Abschlussbericht

Growth of GaInAsP device structures by MOMBE had to be optimized, especially for selective area epitaxy to realize monolithic device integration. In addition the potential of MOMBE for device production had to be explored. Laser structures with strained multiple quantum well layers (MQWs) had to be fabricated and compared to MOVPE structures in terms of device performance. Laser-waveguide integration and planar-selective laser structures had to be formed by selective area epitaxy. A wafer holder for homogeneous growth in single and multi wafer (3 x 2'') operation had to be developed. A variety of MQW laser structures were fabricated with GaInAsP and InAsP layers as well material, where a compressive strain up to 2% was achieved. The MOMBE laser results are comparable to best MOVPE data. High quality waveguide-laser couplings were accomplished by embedded selective area epitaxy of the waveguide structure. Furthermore selective growth of laser structures was investigated. The threshold current densities of these lasers are comparable to data from large area reference lasers. A novel indium free wafer holder was realized resulting in excellent layer homogeneity. For GaInAsP NQW structures a standard deviation of photoluminescence #DELTA##lambda#<2 nm was obtained across more than 90% of the wafer area in multi-wafer operation for each wafer, the wafer-to-wafer standard deviation was #DELTA##lambda#<4 nm. Hence a basis for industrial use of MOMBE has been established. The investigations were performed in close cooperation with the University of Ulm, a project partner. An internationally leading position has been reached by this project. An extension of these studies to laser-modulator integration is planned for the future. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(70,42) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Laser fuer Teilnehmeranschluss

With 63 refs., 49 figs.SIGLETIB: FR 1439+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman