Frequenzselektive molekularelektronische Speicher. Entwicklung eines monolithischen durchstimmbaren AlGaAs/GaAs-Lasers Schlussbericht

Wavelength tunable AlGaAs/GaAs-lasers in the spectral range around 785 nm had to be developed for the spectral hole burning in naphtalocyanin. Laserstructures for this spectral region had been optimized. It was experimentally found that lasers with double quantum wells containing aluminium (thickness L_Z=2 x 7 nm) showed lower threshold current densities (j_t_h=510 A/cm"2) than lasers with aluminiumfree multi-quantumwells (L_z=5 x 3 nm, j_t_h=750 A/cm"2). These results had been proved also theoretically by model calculations. The technological work concentrated on the development of an damagefree wetchemical etchprocess for first-order gratings. Sinusoidal gratings with a corrugation-depth of 30 nm had been fabricated. Due to instabilities of the photoresist the reproducibility of the process was not satisfying. For three-section DBR-Lasers it is necessary to provide a coupling between active waveguides with gain and passive transparent ones. A method has been developed allowing the local diffusion induced disordering of quantum wells. During tempering in a MOVPE-reactor the process is controlled by the properties of the surface coated with a dielectricum. Wavelength shifts up to 42 nm in comparison to an untempered wafer had been realized. In a wafer the energetic difference between Si_3N_4-coated and uncoated areas was 31 meV. Also this process lacked of reproducibility. The high values of threshold current densities of tempered and overgrown laserstructures show the technological induced degradation of the interface. From optimized epitaxial wafers ridge-waveguide lasers had been fabricated with threshold currents down to 10 mA CW. The lasers could be operated up to 80 C and higher. The spectrum showed single mode emission with a few mode hops. Over wide ranges of power a side mode supression ratio up to 23 db had been measured. These lasers were provied for spectral hole burning experiments. (orig.)SIGLEAvailable from TIB Hannover: F96B1311+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman