Investigation of the electrical properties of widegap semiconductors for optoelectronic applications

For electrical characterization, experimental setups for current-voltage-, capacitance-voltage- and theHall-effect-technique were installed and used to get an insight into the electrical behaviourand degradation of the grown devices. Parallel to the optimization of the growth of deviceswithin other PhD theses, the main focus of this work was the investigation of metallizationschemes for laser and light emitting diodes. Two complete different technological proceduresto contact laser diodes grown on different substrate materials have been developed. Thus itis possible to distinguish between technology- and epitaxy-relevant problems and thereforeto optimize these topics separately. As a result, laser diodes on GaAs- and ZnSe-substrateshave been demonstrated operating in continuous-wave excitation from several seconds up tothree minutes, which is the best result ever obtained at an university. In the field of the III-Vmaterial GaN, the main topic was to investigate the basic electrical properties of molecularbeam epitaxial grown layers. Temperature dependent Hall effect measurements have beenperformed at a new Hall experiment setup to extract parameters for growth optimization. Twodifferent charge transport models for layers grown with two different plasma sources for thenitrogen supply were adopted successfully from other material systems and depositiontechniques. The advantage of molecular beam epitaxy for obtaining p-type conductivity withMagnesium without post-growth annealing could be shown. Also the search for alternativedopands for GaN was heavily investigated in connection with another PhD-work at thisinstitute. The contact technology for all used investigation techniques and for future lightemitting devices was established