DFG Research Group PolarCoN

Although optoelectronic devices emitting in the short wavelength visible range of the spectrum have seen an impressive development over the recent years, we are still faced with a substantial efficiency drop for slightly longer wavelengths towards the green color. As a major reason, the polar character of GaN and related compounds is identified, in particular in devices commonly grown along the crystalline c-axis. The research group "PolarCoN" will continue to investigate possibilities to solve this problem by studying non- and semi-polar nitride based hetero and device structures, realized by the epitaxial growth in non- or semipolar directions. In the second project phase (2012 - 2015), we will narrow our focus on approaches being identified as most promising in the first phase. Besides working on small-area defect-free non- and semi-polar free-standing GaN substrates, we will investigate possibilities to grow less polar structures on large areas of pre-structured sapphire wafers and planar silicon wafers. On such templates, optoelectronic device structures will be grown with a major focus on longer wavelength, less-polar laser diodes. A deeper understanding of the physics of less-polar nitride structures and their fabrication processes and limits will enable to give sound answers about future directions for longer wavelength device realization paths. Our research group is composed of expert teams covering all scientific fields for these investigations from epitaxial growth over several kinds of high-level characterization methods to sophisticated device processing, also including the necessary theoretical background for a sound device modelling.

Goals

  • Control polarization effects in group III nitride-based heterostructures
  • Investigate various approaches towards application in optoelectronic devices
  • Close the so-called “green gap” describing lower efficiency in GaN based green light emitters as opposed to their blue and ultraviolet counterparts
  • Develop green nitride-based laser diodes

Approach

  • Epitaxial growth of GaN based structures in non- or semipolar directions
  • Epitaxial growth of defect-free non-polar materials including the development of free-standing non- and semipolar GaN substrates
  • Growth of optoelectronic device structures with a major focus on longer wavelength, non-polar laser diodes
  • Development of respective building blocks – active quantum wells, n- and p-type doping, device processing, mirror fabrication etc.
  • Theoretical modelling

Kontakt

  • Ferdinand Scholz
  • Institut für Optoelektronik
  • Albert-Einstein-Allee 45
  • 89081 Ulm
  • Telefon: +49 (0)731/50-26052
  • Telefax: +49 (0)731/50-26049